This is ./gnutls.info, produced by makeinfo version 4.8 from ./gnutls.texi. This manual is last updated 7 January 2012 for version 2.12.23 of GnuTLS. Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010 Free Software Foundation, Inc. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License". INFO-DIR-SECTION Software libraries START-INFO-DIR-ENTRY * GnuTLS: (gnutls). GNU Transport Layer Security Library. END-INFO-DIR-ENTRY INFO-DIR-SECTION System Administration START-INFO-DIR-ENTRY * certtool: (gnutls)Invoking certtool. Manipulate certificates and keys. * gnutls-serv: (gnutls)Invoking gnutls-serv. GnuTLS test server. * gnutls-cli: (gnutls)Invoking gnutls-cli. GnuTLS test client. * gnutls-cli-debug: (gnutls)Invoking gnutls-cli-debug. GnuTLS debug client. * psktool: (gnutls)Invoking psktool. Simple TLS-Pre-Shared-Keys manager. * srptool: (gnutls)Invoking srptool. Simple SRP password tool. END-INFO-DIR-ENTRY  File: gnutls.info, Node: Top, Next: Preface, Up: (dir) GnuTLS ****** This manual is last updated 7 January 2012 for version 2.12.23 of GnuTLS. Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010 Free Software Foundation, Inc. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License". * Menu: * Preface:: * The Library:: * Introduction to TLS:: * Authentication methods:: * More on certificate authentication:: * How to use TLS in application protocols:: * How to use GnuTLS in applications:: * Included programs:: * Function reference:: * All the supported ciphersuites in GnuTLS:: * Guile Bindings:: * Internal architecture of GnuTLS:: * Copying Information:: * Concept Index:: * Function and Data Index:: * Bibliography::  File: gnutls.info, Node: Preface, Next: The Library, Prev: Top, Up: Top 1 Preface ********* This document tries to demonstrate and explain the GnuTLS library API. A brief introduction to the protocols and the technology involved, is also included so that an application programmer can better understand the GnuTLS purpose and actual offerings. Even if GnuTLS is a typical library software, it operates over several security and cryptographic protocols, which require the programmer to make careful and correct usage of them, otherwise he risks to offer just a false sense of security. Security and the network security terms are very general terms even for computer software thus cannot be easily restricted to a single cryptographic library. For that reason, do not consider a program secure just because it uses GnuTLS; there are several ways to compromise a program or a communication line and GnuTLS only helps with some of them. Although this document tries to be self contained, basic network programming and PKI knowlegde is assumed in most of it. A good introduction to networking can be found in [STEVENS] (*note Bibliography::) and for Public Key Infrastructure in [GUTPKI] (*note Bibliography::). Updated versions of the GnuTLS software and this document will be available from `http://www.gnutls.org/' and `http://www.gnu.org/software/gnutls/'. * Menu: * Getting help:: * Commercial Support:: * Downloading and Installing:: * Bug Reports:: * Contributing::  File: gnutls.info, Node: Getting help, Next: Commercial Support, Up: Preface 1.1 Getting Help ================ A mailing list where users may help each other exists, and you can reach it by sending e-mail to . Archives of the mailing list discussions, and an interface to manage subscriptions, is available through the World Wide Web at `http://lists.gnu.org/mailman/listinfo/help-gnutls'. A mailing list for developers are also available, see `http://www.gnu.org/software/gnutls/lists.html'. Bug reports should be sent to , see *Note Bug Reports::.  File: gnutls.info, Node: Commercial Support, Next: Downloading and Installing, Prev: Getting help, Up: Preface 1.2 Commercial Support ====================== Commercial support is available for users of GnuTLS. The kind of support that can be purchased may include: * Implement new features. Such as a new TLS extension. * Port GnuTLS to new platforms. This could include porting to an embedded platforms that may need memory or size optimization. * Integrating TLS as a security environment in your existing project. * System design of components related to TLS. If you are interested, please write to: Simon Josefsson Datakonsult Hagagatan 24 113 47 Stockholm Sweden E-mail: simon@josefsson.org If your company provides support related to GnuTLS and would like to be mentioned here, contact the author (*note Bug Reports::).  File: gnutls.info, Node: Downloading and Installing, Next: Bug Reports, Prev: Commercial Support, Up: Preface 1.3 Downloading and Installing ============================== GnuTLS is available for download from the following URL: `http://www.gnutls.org/download.html' The latest version is stored in a file, e.g., `gnutls-2.12.23.tar.gz' where the `2.12.23' value is the highest version number in the directory. GnuTLS uses a Linux-like development cycle: even minor version numbers indicate a stable release and a odd minor version number indicates a development release. For example, GnuTLS 1.6.3 denote a stable release since 6 is even, and GnuTLS 1.7.11 denote a development release since 7 is odd. GnuTLS depends on Libgcrypt, and you will need to install Libgcrypt before installing GnuTLS. Libgcrypt is available from `ftp://ftp.gnupg.org/gcrypt/libgcrypt'. Libgcrypt needs another library, libgpg-error, and you need to install libgpg-error before installing Libgcrypt. Libgpg-error is available from `ftp://ftp.gnupg.org/gcrypt/libgpg-error'. Don't forget to verify the cryptographic signature after downloading source code packages. The package is then extracted, configured and built like many other packages that use Autoconf. For detailed information on configuring and building it, refer to the `INSTALL' file that is part of the distribution archive. Typically you invoke `./configure' and then `make check install'. There are a number of compile-time parameters, as discussed below. The compression libraries (libz and lzo) are optional dependencies. You can get libz from `http://www.zlib.net/'. You can get lzo from `http://www.oberhumer.com/opensource/lzo/'. The X.509 part of GnuTLS needs ASN.1 functionality, from a library called libtasn1. A copy of libtasn1 is included in GnuTLS. If you want to install it separately (e.g., to make it possibly to use libtasn1 in other programs), you can get it from `http://www.gnu.org/software/gnutls/download.html'. The OpenPGP part of GnuTLS uses a stripped down version of OpenCDK for parsing OpenPGP packets. It is included GnuTLS. Use parameter `--disable-openpgp-authentication' to disable the OpenPGP functionality in GnuTLS. Unfortunately, we didn't have resources to maintain the code in a separate library. Regarding the Guile bindings, there are additional installation considerations, see *Note Guile Preparations::. A few `configure' options may be relevant, summarized in the table. `--disable-srp-authentication' `--disable-psk-authentication' `--disable-anon-authentication' `--disable-extra-pki' `--disable-openpgp-authentication' `--disable-openssl-compatibility' Disable or enable particular features. Generally not recommended. For the complete list, refer to the output from `configure --help'.  File: gnutls.info, Node: Bug Reports, Next: Contributing, Prev: Downloading and Installing, Up: Preface 1.4 Bug Reports =============== If you think you have found a bug in GnuTLS, please investigate it and report it. * Please make sure that the bug is really in GnuTLS, and preferably also check that it hasn't already been fixed in the latest version. * You have to send us a test case that makes it possible for us to reproduce the bug. * You also have to explain what is wrong; if you get a crash, or if the results printed are not good and in that case, in what way. Make sure that the bug report includes all information you would need to fix this kind of bug for someone else. Please make an effort to produce a self-contained report, with something definite that can be tested or debugged. Vague queries or piecemeal messages are difficult to act on and don't help the development effort. If your bug report is good, we will do our best to help you to get a corrected version of the software; if the bug report is poor, we won't do anything about it (apart from asking you to send better bug reports). If you think something in this manual is unclear, or downright incorrect, or if the language needs to be improved, please also send a note. Send your bug report to: `bug-gnutls@gnu.org'  File: gnutls.info, Node: Contributing, Prev: Bug Reports, Up: Preface 1.5 Contributing ================ If you want to submit a patch for inclusion - from solve a typo you discovered, up to adding support for a new feature - you should submit it as a bug report (*note Bug Reports::). There are some things that you can do to increase the chances for it to be included in the official package. Unless your patch is very small (say, under 10 lines) we require that you assign the copyright of your work to the Free Software Foundation. This is to protect the freedom of the project. If you have not already signed papers, we will send you the necessary information when you submit your contribution. For contributions that doesn't consist of actual programming code, the only guidelines are common sense. Use it. For code contributions, a number of style guides will help you: * Coding Style. Follow the GNU Standards document. If you normally code using another coding standard, there is no problem, but you should use `indent' to reformat the code before submitting your work. * Use the unified diff format `diff -u'. * Return errors. No reason whatsoever should abort the execution of the library. Even memory allocation errors, e.g. when malloc return NULL, should work although result in an error code. * Design with thread safety in mind. Don't use global variables. Don't even write to per-handle global variables unless the documented behaviour of the function you write is to write to the per-handle global variable. * Avoid using the C math library. It causes problems for embedded implementations, and in most situations it is very easy to avoid using it. * Document your functions. Use comments before each function headers, that, if properly formatted, are extracted into Texinfo manuals and GTK-DOC web pages. * Supply a ChangeLog and NEWS entries, where appropriate.  File: gnutls.info, Node: The Library, Next: Introduction to TLS, Prev: Preface, Up: Top 2 The Library ************* In brief GnuTLS can be described as a library which offers an API to access secure communication protocols. These protocols provide privacy over insecure lines, and were designed to prevent eavesdropping, tampering, or message forgery. Technically GnuTLS is a portable ANSI C based library which implements the protocols ranging from SSL 3.0 to TLS 1.2 (*Note Introduction to TLS::, for a more detailed description of the protocols), accompanied with the required framework for authentication and public key infrastructure. Important features of the GnuTLS library include: * Support for TLS 1.2, TLS 1.1, TLS 1.0 and SSL 3.0 protocols. * Support for both X.509 and OpenPGP certificates. * Support for handling and verification of certificates. * Support for SRP for TLS authentication. * Support for PSK for TLS authentication. * Support for TLS Extension mechanism. * Support for TLS Compression Methods. Additionally GnuTLS provides a limited emulation API for the widely used OpenSSL(1) library, to ease integration with existing applications. GnuTLS consists of three independent parts, namely the "TLS protocol part", the "Certificate part", and the "Cryptographic backend" part. The `TLS protocol part' is the actual protocol implementation, and is entirely implemented within the GnuTLS library. The `Certificate part' consists of the certificate parsing, and verification functions which is partially implemented in the GnuTLS library. The Libtasn1(2), a library which offers ASN.1 parsing capabilities, is used for the X.509 certificate parsing functions. A smaller version of OpenCDK(3) is used for the OpenPGP key support in GnuTLS. The "Cryptographic backend" is provided by the Libgcrypt(4) library(5). In order to ease integration in embedded systems, parts of the GnuTLS library can be disabled at compile time. That way a small library, with the required features, can be generated. * Menu: * General Idea:: * Error handling:: * Memory handling:: * Callback functions:: ---------- Footnotes ---------- (1) `http://www.openssl.org/' (2) `ftp://ftp.gnupg.org/gcrypt/alpha/gnutls/libtasn1/' (3) `ftp://ftp.gnupg.org/gcrypt/alpha/gnutls/opencdk/' (4) `ftp://ftp.gnupg.org/gcrypt/alpha/libgcrypt/' (5) On current versions of GnuTLS it is possible to override the default crypto backend. Check *note Cryptographic Backend:: for details  File: gnutls.info, Node: General Idea, Next: Error handling, Up: The Library 2.1 General Idea ================ A brief description of how GnuTLS works internally is shown at the figure below. This section may be easier to understand after having seen the examples (*note examples::). [image src="gnutls-internals.png"] As shown in the figure, there is a read-only global state that is initialized once by the global initialization function. This global structure, among others, contains the memory allocation functions used, and some structures needed for the ASN.1 parser. This structure is never modified by any GnuTLS function, except for the deinitialization function which frees all memory allocated in the global structure and is called after the program has permanently finished using GnuTLS. The credentials structure is used by some authentication methods, such as certificate authentication (*note Certificate Authentication::). A credentials structure may contain certificates, private keys, temporary parameters for Diffie-Hellman or RSA key exchange, and other stuff that may be shared between several TLS sessions. This structure should be initialized using the appropriate initialization functions. For example an application which uses certificate authentication would probably initialize the credentials, using the appropriate functions, and put its trusted certificates in this structure. The next step is to associate the credentials structure with each TLS session. A GnuTLS session contains all the required stuff for a session to handle one secure connection. This session calls directly to the transport layer functions, in order to communicate with the peer. Every session has a unique session ID shared with the peer. Since TLS sessions can be resumed, servers would probably need a database backend to hold the session's parameters. Every GnuTLS session after a successful handshake calls the appropriate backend function (*Note resume::, for information on initialization) to store the newly negotiated session. The session database is examined by the server just after having received the client hello(1), and if the session ID sent by the client, matches a stored session, the stored session will be retrieved, and the new session will be a resumed one, and will share the same session ID with the previous one. ---------- Footnotes ---------- (1) The first message in a TLS handshake  File: gnutls.info, Node: Error handling, Next: Memory handling, Prev: General Idea, Up: The Library 2.2 Error Handling ================== In GnuTLS most functions return an integer type as a result. In almost all cases a zero or a positive number means success, and a negative number indicates failure, or a situation that some action has to be taken. Thus negative error codes may be fatal or not. Fatal errors terminate the connection immediately and further sends and receives will be disallowed. An example of a fatal error code is `GNUTLS_E_DECRYPTION_FAILED'. Non-fatal errors may warn about something, i.e., a warning alert was received, or indicate the some action has to be taken. This is the case with the error code `GNUTLS_E_REHANDSHAKE' returned by *Note gnutls_record_recv::. This error code indicates that the server requests a re-handshake. The client may ignore this request, or may reply with an alert. You can test if an error code is a fatal one by using the *Note gnutls_error_is_fatal::. If any non fatal errors, that require an action, are to be returned by a function, these error codes will be documented in the function's reference. *Note Error Codes::, for all the error codes.  File: gnutls.info, Node: Memory handling, Next: Callback functions, Prev: Error handling, Up: The Library 2.3 Memory Handling =================== GnuTLS internally handles heap allocated objects differently, depending on the sensitivity of the data they contain. However for performance reasons, the default memory functions do not overwrite sensitive data from memory, nor protect such objects from being written to the swap. In order to change the default behavior the *Note gnutls_global_set_mem_functions:: function is available which can be used to set other memory handlers than the defaults. The Libgcrypt library on which GnuTLS depends, has such secure memory allocation functions available. These should be used in cases where even the system's swap memory is not considered secure. See the documentation of Libgcrypt for more information.  File: gnutls.info, Node: Callback functions, Prev: Memory handling, Up: The Library 2.4 Callback Functions ====================== There are several cases where GnuTLS may need some out of band input from your program. This is now implemented using some callback functions, which your program is expected to register. An example of this type of functions are the push and pull callbacks which are used to specify the functions that will retrieve and send data to the transport layer. * *Note gnutls_transport_set_push_function:: * *Note gnutls_transport_set_pull_function:: Other callback functions such as the one set by *Note gnutls_srp_set_server_credentials_function::, may require more complicated input, including data to be allocated. These callbacks should allocate and free memory using the functions shown below. * *Note gnutls_malloc:: * *Note gnutls_free::  File: gnutls.info, Node: Introduction to TLS, Next: Authentication methods, Prev: The Library, Up: Top 3 Introduction to TLS ********************* TLS stands for "Transport Layer Security" and is the successor of SSL, the Secure Sockets Layer protocol [SSL3] (*note Bibliography::) designed by Netscape. TLS is an Internet protocol, defined by IETF(1), described in RFC 4346 and also in [RESCORLA] (*note Bibliography::). The protocol provides confidentiality, and authentication layers over any reliable transport layer. The description, below, refers to TLS 1.0 but also applies to TLS 1.1 [RFC4346] (*note Bibliography::) and SSL 3.0, since the differences of these protocols are minor. Older protocols such as SSL 2.0 are not discussed nor implemented in GnuTLS since they are not considered secure today. GnuTLS also supports X.509 and OpenPGP [RFC4880] (*note Bibliography::). * Menu: * TLS layers:: * The transport layer:: * The TLS record protocol:: * The TLS Alert Protocol:: * The TLS Handshake Protocol:: * TLS Extensions:: * Selecting cryptographic key sizes:: * On SSL 2 and older protocols:: ---------- Footnotes ---------- (1) IETF, or Internet Engineering Task Force, is a large open international community of network designers, operators, vendors, and researchers concerned with the evolution of the Internet architecture and the smooth operation of the Internet. It is open to any interested individual.  File: gnutls.info, Node: TLS layers, Next: The transport layer, Up: Introduction to TLS 3.1 TLS Layers ============== TLS is a layered protocol, and consists of the Record Protocol, the Handshake Protocol and the Alert Protocol. The Record Protocol is to serve all other protocols and is above the transport layer. The Record protocol offers symmetric encryption, data authenticity, and optionally compression. The Alert protocol offers some signaling to the other protocols. It can help informing the peer for the cause of failures and other error conditions. *Note The Alert Protocol::, for more information. The alert protocol is above the record protocol. The Handshake protocol is responsible for the security parameters' negotiation, the initial key exchange and authentication. *Note The Handshake Protocol::, for more information about the handshake protocol. The protocol layering in TLS is shown in the figure below. [image src="gnutls-layers.png"]  File: gnutls.info, Node: The transport layer, Next: The TLS record protocol, Prev: TLS layers, Up: Introduction to TLS 3.2 The Transport Layer ======================= TLS is not limited to one transport layer, it can be used above any transport layer, as long as it is a reliable one. A set of functions is provided and their purpose is to load to GnuTLS the required callbacks to access the transport layer. * *Note gnutls_transport_set_push_function:: * *Note gnutls_transport_set_vec_push_function:: * *Note gnutls_transport_set_pull_function:: * *Note gnutls_transport_set_ptr:: * *Note gnutls_transport_set_lowat:: * *Note gnutls_transport_set_errno:: These functions accept a callback function as a parameter. The callback functions should return the number of bytes written, or -1 on error and should set `errno' appropriately. In some environments, setting `errno' is unreliable, for example Windows have several errno variables in different CRTs, or it may be that errno is not a thread-local variable. If this is a concern to you, call `gnutls_transport_set_errno' with the intended errno value instead of setting `errno' directly. GnuTLS currently only interprets the EINTR and EAGAIN errno values and returns the corresponding GnuTLS error codes `GNUTLS_E_INTERRUPTED' and `GNUTLS_E_AGAIN'. These values are usually returned by interrupted system calls, or when non blocking IO is used. All GnuTLS functions can be resumed (called again), if any of these error codes is returned. The error codes above refer to the system call, not the GnuTLS function, since signals do not interrupt GnuTLS' functions. For non blocking sockets or other custom made pull/push functions the *Note gnutls_transport_set_lowat:: must be called, with a zero low water mark value. By default, if the transport functions are not set, GnuTLS will use the Berkeley Sockets functions.  File: gnutls.info, Node: The TLS record protocol, Next: The TLS Alert Protocol, Prev: The transport layer, Up: Introduction to TLS 3.3 The TLS Record Protocol =========================== The Record protocol is the secure communications provider. Its purpose is to encrypt, authenticate and --optionally-- compress packets. The following functions are available: *Note gnutls_record_send::: To send a record packet (with application data). *Note gnutls_record_recv::: To receive a record packet (with application data). *Note gnutls_record_get_direction::: To get the direction of the last interrupted function call. As you may have already noticed, the functions which access the Record protocol, are quite limited, given the importance of this protocol in TLS. This is because the Record protocol's parameters are all set by the Handshake protocol. The Record protocol initially starts with NULL parameters, which means no encryption, and no MAC is used. Encryption and authentication begin just after the handshake protocol has finished. * Menu: * Encryption algorithms used in the record layer:: * Compression algorithms used in the record layer:: * Weaknesses and countermeasures:: * On Record Padding::  File: gnutls.info, Node: Encryption algorithms used in the record layer, Next: Compression algorithms used in the record layer, Up: The TLS record protocol 3.3.1 Encryption Algorithms Used in the Record Layer ---------------------------------------------------- Confidentiality in the record layer is achieved by using symmetric block encryption algorithms like `3DES', `AES'(1), or stream algorithms like `ARCFOUR_128'(2). Ciphers are encryption algorithms that use a single, secret, key to encrypt and decrypt data. Block algorithms in TLS also provide protection against statistical analysis of the data. Thus, if you're using the TLS protocol, a random number of blocks will be appended to data, to prevent eavesdroppers from guessing the actual data size. Supported cipher algorithms: `3DES_CBC' `3DES_CBC' is the DES block cipher algorithm used with triple encryption (EDE). Has 64 bits block size and is used in CBC mode. `ARCFOUR_128' ARCFOUR is a fast stream cipher. `ARCFOUR_40' This is the ARCFOUR cipher that is fed with a 40 bit key, which is considered weak. `AES_CBC' AES or RIJNDAEL is the block cipher algorithm that replaces the old DES algorithm. Has 128 bits block size and is used in CBC mode. Supported MAC algorithms: `MAC_MD5' MD5 is a cryptographic hash algorithm designed by Ron Rivest. Outputs 128 bits of data. `MAC_SHA' SHA is a cryptographic hash algorithm designed by NSA. Outputs 160 bits of data. ---------- Footnotes ---------- (1) AES, or Advanced Encryption Standard, is actually the RIJNDAEL algorithm. This is the algorithm that replaced DES. (2) `ARCFOUR_128' is a compatible algorithm with RSA's RC4 algorithm, which is considered to be a trade secret.  File: gnutls.info, Node: Compression algorithms used in the record layer, Next: Weaknesses and countermeasures, Prev: Encryption algorithms used in the record layer, Up: The TLS record protocol 3.3.2 Compression Algorithms Used in the Record Layer ----------------------------------------------------- The TLS record layer also supports compression. The algorithms implemented in GnuTLS can be found in the table below. All the algorithms except for DEFLATE which is referenced in [RFC3749] (*note Bibliography::), should be considered as GnuTLS' extensions(1), and should be advertised only when the peer is known to have a compliant client, to avoid interoperability problems. The included algorithms perform really good when text, or other compressible data are to be transfered, but offer nothing on already compressed data, such as compressed images, zipped archives etc. These compression algorithms, may be useful in high bandwidth TLS tunnels, and in cases where network usage has to be minimized. As a drawback, compression increases latency. The record layer compression in GnuTLS is implemented based on the proposal [RFC3749] (*note Bibliography::). The supported compression algorithms are: `DEFLATE' Zlib compression, using the deflate algorithm. `LZO' LZO is a very fast compression algorithm. This algorithm is only available if the GnuTLS-extra library has been initialized and the private extensions are enabled, and if GnuTLS was built with LZO support. ---------- Footnotes ---------- (1) You should use *Note gnutls_handshake_set_private_extensions:: to enable private extensions.  File: gnutls.info, Node: Weaknesses and countermeasures, Next: On Record Padding, Prev: Compression algorithms used in the record layer, Up: The TLS record protocol 3.3.3 Weaknesses and Countermeasures ------------------------------------ Some weaknesses that may affect the security of the Record layer have been found in TLS 1.0 protocol. These weaknesses can be exploited by active attackers, and exploit the facts that 1. TLS has separate alerts for "decryption_failed" and "bad_record_mac" 2. The decryption failure reason can be detected by timing the response time. 3. The IV for CBC encrypted packets is the last block of the previous encrypted packet. Those weaknesses were solved in TLS 1.1 [RFC4346] (*note Bibliography::) which is implemented in GnuTLS. For a detailed discussion see the archives of the TLS Working Group mailing list and the paper [CBCATT] (*note Bibliography::).  File: gnutls.info, Node: On Record Padding, Prev: Weaknesses and countermeasures, Up: The TLS record protocol 3.3.4 On Record Padding ----------------------- The TLS protocol allows for random padding of records, to make it more difficult to perform analysis on the length of exchanged messages (RFC 5246 6.2.3.2). GnuTLS appears to be one of few implementation that take advantage of this text, and pad records by a random length. The TLS implementation in the Symbian operating system, frequently used by Nokia and Sony-Ericsson mobile phones, cannot handle non-minimal record padding. What happens when one of these clients handshake with a GnuTLS server is that the client will fail to compute the correct MAC for the record. The client sends a TLS alert (`bad_record_mac') and disconnects. Typically this will result in error messages such as 'A TLS fatal alert has been received', 'Bad record MAC', or both, on the GnuTLS server side. GnuTLS implements a work around for this problem. However, it has to be enabled specifically. It can be enabled by using *Note gnutls_record_disable_padding::, or *Note gnutls_priority_set:: with the `%COMPAT' priority string. If you implement an application that have a configuration file, we recommend that you make it possible for users or administrators to specify a GnuTLS protocol priority string, which is used by your application via *Note gnutls_priority_set::. To allow the best flexibility, make it possible to have a different priority string for different incoming IP addresses. To enable the workaround in the `gnutls-cli' client or the `gnutls-serv' server, for testing of other implementations, use the following parameter: `--priority "NORMAL:%COMPAT"'.  File: gnutls.info, Node: The TLS Alert Protocol, Next: The TLS Handshake Protocol, Prev: The TLS record protocol, Up: Introduction to TLS 3.4 The TLS Alert Protocol ========================== The Alert protocol is there to allow signals to be sent between peers. These signals are mostly used to inform the peer about the cause of a protocol failure. Some of these signals are used internally by the protocol and the application protocol does not have to cope with them (see `GNUTLS_A_CLOSE_NOTIFY'), and others refer to the application protocol solely (see `GNUTLS_A_USER_CANCELLED'). An alert signal includes a level indication which may be either fatal or warning. Fatal alerts always terminate the current connection, and prevent future renegotiations using the current session ID. The alert messages are protected by the record protocol, thus the information that is included does not leak. You must take extreme care for the alert information not to leak to a possible attacker, via public log files etc. *Note gnutls_alert_send::: To send an alert signal. *Note gnutls_error_to_alert::: To map a gnutls error number to an alert signal. *Note gnutls_alert_get::: Returns the last received alert. *Note gnutls_alert_get_name::: Returns the name, in a character array, of the given alert.  File: gnutls.info, Node: The TLS Handshake Protocol, Next: TLS Extensions, Prev: The TLS Alert Protocol, Up: Introduction to TLS 3.5 The TLS Handshake Protocol ============================== The Handshake protocol is responsible for the ciphersuite negotiation, the initial key exchange, and the authentication of the two peers. This is fully controlled by the application layer, thus your program has to set up the required parameters. Available functions to control the handshake protocol include: *Note gnutls_priority_init::: To initialize a priority set of ciphers. *Note gnutls_priority_deinit::: To deinitialize a priority set of ciphers. *Note gnutls_priority_set::: To associate a priority set with a TLS session. *Note gnutls_priority_set_direct::: To directly associate a session with a given priority string. *Note gnutls_credentials_set::: To set the appropriate credentials structures. *Note gnutls_certificate_server_set_request::: To set whether client certificate is required or not. *Note gnutls_handshake::: To initiate the handshake. * Menu: * TLS Cipher Suites:: TLS session parameters. * Priority Strings:: Defining how parameters are negotiated. * Client Authentication:: Requesting a certificate from the client. * Resuming Sessions:: Reusing previously established keys. * Resuming Internals:: More information on reusing previously established keys. * Interoperability:: About interoperability with other implementations.  File: gnutls.info, Node: TLS Cipher Suites, Next: Priority Strings, Up: The TLS Handshake Protocol 3.5.1 TLS Cipher Suites ----------------------- The Handshake Protocol of TLS negotiates cipher suites of the form `TLS_DHE_RSA_WITH_3DES_CBC_SHA'. The usual cipher suites contain these parameters: * The key exchange algorithm. `DHE_RSA' in the example. * The Symmetric encryption algorithm and mode `3DES_CBC' in this example. * The MAC(1) algorithm used for authentication. `MAC_SHA' is used in the above example. The cipher suite negotiated in the handshake protocol will affect the Record Protocol, by enabling encryption and data authentication. Note that you should not over rely on TLS to negotiate the strongest available cipher suite. Do not enable ciphers and algorithms that you consider weak. All the supported ciphersuites are shown in *Note ciphersuites::. ---------- Footnotes ---------- (1) MAC stands for Message Authentication Code. It can be described as a keyed hash algorithm. See RFC2104.  File: gnutls.info, Node: Priority Strings, Next: Client Authentication, Prev: TLS Cipher Suites, Up: The TLS Handshake Protocol 3.5.2 Priority Strings ---------------------- In order to specify cipher suite preferences, the previously shown priority functions accept a string that specifies the algorithms to be enabled in a TLS handshake. That string may contain some high level keyword such as: PERFORMANCE: All the "secure" ciphersuites are enabled, limited to 128 bit ciphers and sorted by terms of speed performance. NORMAL: Means all "secure" ciphersuites. The 256-bit ciphers are included as a fallback only. The ciphers are sorted by security margin. SECURE128: Means all "secure" ciphersuites with ciphers up to 128 bits, sorted by security margin. SECURE256: Means all "secure" ciphersuites including the 256 bit ciphers, sorted by security margin. EXPORT: Means all ciphersuites are enabled, including the low-security 40 bit ciphers. NONE: Means nothing is enabled. This disables even protocols and compression methods. It should be followed by the algorithms to be enabled. or it might contain special keywords, that will be explained later on. Unless the first keyword is "NONE" the defaults (in preference order) are for TLS protocols TLS 1.2, TLS1.1, TLS1.0, SSL3.0; for compression NULL; for certificate types X.509, OpenPGP. For key exchange algorithms when in NORMAL or SECURE levels the perfect forward secrecy algorithms take precedence of the other protocols. In all cases all the supported key exchange algorithms are enabled (except for the RSA-EXPORT which is only enabled in EXPORT level). The NONE keyword is followed by the algorithms to be enabled, and is used to provide the exact list of requested algorithms(1). The order with which every algorithm is specified is significant. Similar algorithms specified before others will take precedence. Keywords prepended to individual algorithms: '!' or '-' appended with an algorithm will remove this algorithm. "+" appended with an algorithm will add this algorithm. Individual algorithms: Ciphers: AES-128-CBC, AES-256-CBC, CAMELLIA-128-CBC, CAMELLIA-256-CBC, ARCFOUR-128, 3DES-CBC ARCFOUR-40. Catch all name is CIPHER-ALL which will add all the algorithms from NORMAL priority. Key exchange: RSA, DHE-RSA, DHE-DSS, SRP, SRP-RSA, SRP-DSS, PSK, DHE-PSK, ANON-DH, RSA-EXPORT. The key exchange methods do not have a catch all. MAC: MD5, SHA1, SHA256. All algorithms from NORMAL priority can be accessed with MAC-ALL. Compression algorithms: COMP-NULL, COMP-DEFLATE. Catch all is COMP-ALL. TLS versions: VERS-SSL3.0, VERS-TLS1.0, VERS-TLS1.1, VERS-TLS1.2. Catch all is VERS-TLS-ALL. Signature algorithms: SIGN-RSA-SHA1, SIGN-RSA-SHA224, SIGN-RSA-SHA256, SIGN-RSA-SHA384, SIGN-RSA-SHA512, SIGN-DSA-SHA1, SIGN-DSA-SHA224, SIGN-DSA-SHA256, SIGN-RSA-MD5. Catch all is SIGN-ALL. This is only valid for TLS 1.2 and later. Special keywords: %COMPAT: will enable compatibility mode. It might mean that violations of the protocols are allowed as long as maximum compatibility with problematic clients and servers is achieved. %DISABLE_SAFE_RENEGOTIATION: will disable safe renegotiation completely. Do not use unless you know what you are doing. Testing purposes only. %UNSAFE_RENEGOTIATION: will allow handshakes and rehandshakes without the safe renegotiation extension. Note that for clients this mode is insecure (you may be under attack), and for servers it will allow insecure clients to connect (which could be fooled by an attacker). Do not use unless you know what you are doing and want maximum compatibility. %PARTIAL_RENEGOTIATION: will allow initial handshakes to proceed, but not rehandshakes. This leaves the client vulnerable to attack, and servers will be compatible with non-upgraded clients for initial handshakes. This is currently the default for clients and servers, for compatibility reasons. %SAFE_RENEGOTIATION: will enforce safe renegotiation. Clients and servers will refuse to talk to an insecure peer. Currently this causes operability problems, but is required for full protection. %SSL3_RECORD_VERSION: will use SSL3.0 record version in client hello. This is the default. %LATEST_RECORD_VERSION: will use the latest TLS version record version in client hello. %VERIFY_ALLOW_SIGN_RSA_MD5: will allow RSA-MD5 signatures in certificate chains. %VERIFY_ALLOW_X509_V1_CA_CRT: will allow V1 CAs in chains. ---------- Footnotes ---------- (1) To avoid collisions in order to specify a compression algorithm in this string you have to prefix it with "COMP-", protocol versions with "VERS-", signature algorithms with "SIGN-" and certificate types with "CTYPE-". All other algorithms don't need a prefix.  File: gnutls.info, Node: Client Authentication, Next: Resuming Sessions, Prev: Priority Strings, Up: The TLS Handshake Protocol 3.5.3 Client Authentication --------------------------- In the case of ciphersuites that use certificate authentication, the authentication of the client is optional in TLS. A server may request a certificate from the client -- using the *Note gnutls_certificate_server_set_request:: function. If a certificate is to be requested from the client during the handshake, the server will send a certificate request message that contains a list of acceptable certificate signers. In GnuTLS the certificate signers list is constructed using the trusted Certificate Authorities by the server. That is the ones set using * *Note gnutls_certificate_set_x509_trust_file:: * *Note gnutls_certificate_set_x509_trust_mem:: Sending of the names of the CAs can be controlled using *Note gnutls_certificate_send_x509_rdn_sequence::. The client, then, may send a certificate, signed by one of the server's acceptable signers.  File: gnutls.info, Node: Resuming Sessions, Next: Resuming Internals, Prev: Client Authentication, Up: The TLS Handshake Protocol 3.5.4 Resuming Sessions ----------------------- The *Note gnutls_handshake:: function, is expensive since a lot of calculations are performed. In order to support many fast connections to the same server a client may use session resuming. *Session resuming* is a feature of the TLS protocol which allows a client to connect to a server, after a successful handshake, without the expensive calculations. This is achieved by using the previously established keys. GnuTLS supports this feature, and the example (*note ex:resume-client::) illustrates a typical use of it. Keep in mind that sessions are expired after some time, for security reasons, thus it may be normal for a server not to resume a session even if you requested that. Also note that you must enable, using the priority functions, at least the algorithms used in the last session.  File: gnutls.info, Node: Resuming Internals, Next: Interoperability, Prev: Resuming Sessions, Up: The TLS Handshake Protocol 3.5.5 Resuming Internals ------------------------ The resuming capability, mostly in the server side, is one of the problems of a thread-safe TLS implementations. The problem is that all threads must share information in order to be able to resume sessions. The gnutls approach is, in case of a client, to leave all the burden of resuming to the client. I.e., copy and keep the necessary parameters. See the functions: * *Note gnutls_session_get_data:: * *Note gnutls_session_get_id:: * *Note gnutls_session_set_data:: The server side is different. A server has to specify some callback functions which store, retrieve and delete session data. These can be registered with: * *Note gnutls_db_set_remove_function:: * *Note gnutls_db_set_store_function:: * *Note gnutls_db_set_retrieve_function:: * *Note gnutls_db_set_ptr:: It might also be useful to be able to check for expired sessions in order to remove them, and save space. The function *Note gnutls_db_check_entry:: is provided for that reason.  File: gnutls.info, Node: Interoperability, Prev: Resuming Internals, Up: The TLS Handshake Protocol 3.5.6 Interoperability ---------------------- The TLS handshake is a complex procedure that negotiates all required parameters for a secure session. GnuTLS supports several TLS extensions, as well as the latest TLS protocol version 1.2. However few implementations are not able to properly interoperate once faced with extensions or version protocols they do not support and understand. The TLS protocol allows for a graceful downgrade to the commonly supported options, but practice shows it is not always implemented correctly. Because there is no way to achieve maximum interoperability with broken peers without sacrificing security, GnuTLS ignores such peers by default. This might not be acceptable in cases where maximum compatibility is required. Thus we allow enabling compatibility with broken peers using priority strings (see *Note Priority Strings::). An example priority string that is known to provide wide compatibility even with broken peers is shown below: NORMAL:-VERS-TLS-ALL:+VERS-TLS1.0:+VERS-SSL3.0:%COMPAT This priority string will only enable SSL 3.0 and TLS 1.0 as protocols and will disable, via the `%COMPAT' keyword, several TLS protocol options that are known to cause compatibility problems. We suggest however only to use this mode if compatibility issues occur.  File: gnutls.info, Node: TLS Extensions, Next: Selecting cryptographic key sizes, Prev: The TLS Handshake Protocol, Up: Introduction to TLS 3.6 TLS Extensions ================== A number of extensions to the TLS protocol have been proposed mainly in [TLSEXT] (*note Bibliography::). The extensions supported in GnuTLS are: * Maximum fragment length negotiation * Server name indication * Session tickets * Safe Renegotiation and they will be discussed in the subsections that follow. 3.6.1 Maximum Fragment Length Negotiation ----------------------------------------- This extension allows a TLS implementation to negotiate a smaller value for record packet maximum length. This extension may be useful to clients with constrained capabilities. See the *Note gnutls_record_set_max_size:: and the *Note gnutls_record_get_max_size:: functions. 3.6.2 Server Name Indication ---------------------------- A common problem in HTTPS servers is the fact that the TLS protocol is not aware of the hostname that a client connects to, when the handshake procedure begins. For that reason the TLS server has no way to know which certificate to send. This extension solves that problem within the TLS protocol, and allows a client to send the HTTP hostname before the handshake begins within the first handshake packet. The functions *Note gnutls_server_name_set:: and *Note gnutls_server_name_get:: can be used to enable this extension, or to retrieve the name sent by a client. 3.6.3 Session Tickets --------------------- To resume a TLS session the server normally store some state. This complicates deployment, and typical situations the client can cache information and send it to the server instead. The Session Ticket extension implements this idea, and it is documented in RFC 5077 [TLSTKT] (*note Bibliography::). Clients can enable support for TLS tickets with *Note gnutls_session_ticket_enable_client:: and servers use *Note gnutls_session_ticket_key_generate:: to generate a key and *Note gnutls_session_ticket_enable_server:: to enable the extension. Clients resume sessions using the ticket using the normal session resume functions, *Note resume::. 3.6.4 Safe Renegotiation ------------------------ TLS gives the option to two communicating parties to renegotiate and update their security parameters. One useful example of this feature was for a client to initially connect using anonymous negotiation to a server, and the renegotiate using some authenticated ciphersuite. This occured to avoid having the client sending its credentials in the clear. However this renegotiation, as initially designed would not ensure that the party one is renegotiating is the same as the one in the initial negotiation. For example one server could forward all renegotiation traffic to an other server who will see this traffic as an initial negotiation attempt. This might be seen as a valid design decision, but it seems it was not widely known or understood, thus today some application protocols the TLS renegotiation feature in a manner that enables a malicious server to insert content of his choice in the beginning of a TLS session. The most prominent vulnerability was with HTTPS. There servers request a renegotiation to enforce an anonymous user to use a certificate in order to access certain parts of a web site. The attack works by having the attacker simulate a client and connect to a server, with server-only authentication, and send some data intended to cause harm. The server will then require renegotiation from him in order to perform the request. When the proper client attempts to contact the server, the attacker hijacks that connection and forwards traffic to the initial server that requested renegotiation. The attacker will not be able to read the data exchanged between the client and the server. However, the server will (incorrectly) assume that the initial request sent by the attacker was sent by the now authenticated client. The result is a prefix plain-text injection attack. The above is just one example. Other vulnerabilities exists that do not rely on the TLS renegotiation to change the client's authenticated status (either TLS or application layer). While fixing these application protocols and implementations would be one natural reaction, an extension to TLS has been designed that cryptographically binds together any renegotiated handshakes with the initial negotiation. When the extension is used, the attack is detected and the session can be terminated. The extension is specified in [RFC5746] (*note Bibliography::). GnuTLS supports the safe renegotiation extension. The default behavior is as follows. Clients will attempt to negotiate the safe renegotiation extension when talking to servers. Servers will accept the extension when presented by clients. Clients and servers will permit an initial handshake to complete even when the other side does not support the safe renegotiation extension. Clients and servers will refuse renegotiation attempts when the extension has not been negotiated. Note that permitting clients to connect to servers when the safe renegotiation extension is not enabled, is open up for attacks. Changing this default behaviour would prevent interoperability against the majority of deployed servers out there. We will reconsider this default behaviour in the future when more servers have been upgraded. Note that it is easy to configure clients to always require the safe renegotiation extension from servers (see below on the `%SAFE_RENEGOTIATION' priority string). To modify the default behaviour, we have introduced some new priority strings. The priority strings can be used by applications (*note gnutls_priority_set::) and end users (e.g., `--priority' parameter to `gnutls-cli' and `gnutls-serv'). The `%UNSAFE_RENEGOTIATION' priority string permits (re-)handshakes even when the safe renegotiation extension was not negotiated. The default behavior is `%PARTIAL_RENEGOTIATION' that will prevent renegotiation with clients and servers not supporting the extension. This is secure for servers but leaves clients vulnerable to some attacks, but this is a tradeoff between security and compatibility with old servers. The `%SAFE_RENEGOTIATION' priority string makes clients and servers require the extension for every handshake. The latter is the most secure option for clients, at the cost of not being able to connect to legacy servers. Servers will also deny clients that do not support the extension from connecting. It is possible to disable use of the extension completely, in both clients and servers, by using the `%DISABLE_SAFE_RENEGOTIATION' priority string however we strongly recommend you to only do this for debugging and test purposes. The default values if the flags above are not specified are: `Server:' %PARTIAL_RENEGOTIATION `Client:' %PARTIAL_RENEGOTIATION For applications we have introduced a new API related to safe renegotiation. The *Note gnutls_safe_renegotiation_status:: function is used to check if the extension has been negotiated on a session, and can be used both by clients and servers.  File: gnutls.info, Node: Selecting cryptographic key sizes, Next: On SSL 2 and older protocols, Prev: TLS Extensions, Up: Introduction to TLS 3.7 Selecting Cryptographic Key Sizes ===================================== In TLS, since a lot of algorithms are involved, it is not easy to set a consistent security level. For this reason this section will present some correspondance between key sizes of symmetric algorithms and public key algorithms based on the "ECRYPT II Yearly Report on Algorithms and Keysizes (2009-2010)" in [ECRYPT] (*note Bibliography::). Those can be used to generate certificates with appropriate key sizes as well as parameters for Diffie-Hellman and SRP authentication. SecurityRSA, DH ECC `gnutls_sec_param_t'Description bits and SRP key parameter size size 64 816 128 `WEAK' Very short term protection against small organizations 80 1248 160 `LOW' Very short term protection against agencies 112 2432 224 `NORMAL' Medium-term protection 128 3248 256 `HIGH' Long term protection 256 15424 512 `ULTRA' Foreseeable future The first column provides a security parameter in a number of bits. This gives an indication of the number of combinations to be tried by an adversary to brute force a key. For example to test all possible keys in a 112 bit security parameter 2^112 combinations have to be tried. For today's technology this is infeasible. The next two columns correlate the security parameter with actual bit sizes of parameters for DH, RSA, SRP and ECC algorithms. A mapping to `gnutls_sec_param_t' value is given for each security parameter, on the next column, and finally a brief description of the level. Note however that the values suggested here are nothing more than an educated guess that is valid today. There are no guarrantees that an algorithm will remain unbreakable or that these values will remain constant in time. There could be scientific breakthroughs that cannot be predicted or total failure of the current public key systems by quantum computers. On the other hand though the cryptosystems used in TLS are selected in a conservative way and such catastrophic breakthroughs or failures are believed to be unlikely. NIST publication SP 800-57 [NISTSP80057] (*note Bibliography::) contains a similar table. When using GnuTLS and a decision on bit sizes for a public key algorithm is required, use of the following functions is recommended: * *Note gnutls_pk_bits_to_sec_param:: * *Note gnutls_sec_param_to_pk_bits:: Those functions will convert a human understandable security parameter of `gnutls_sec_param_t' type, to a number of bits suitable for a public key algorithm.  File: gnutls.info, Node: On SSL 2 and older protocols, Prev: Selecting cryptographic key sizes, Up: Introduction to TLS 3.8 On SSL 2 and Older Protocols ================================ One of the initial decisions in the GnuTLS development was to implement the known security protocols for the transport layer. Initially TLS 1.0 was implemented since it was the latest at that time, and was considered to be the most advanced in security properties. Later the SSL 3.0 protocol was implemented since it is still the only protocol supported by several servers and there are no serious security vulnerabilities known. One question that may arise is why we didn't implement SSL 2.0 in the library. There are several reasons, most important being that it has serious security flaws, unacceptable for a modern security library. Other than that, this protocol is barely used by anyone these days since it has been deprecated since 1996. The security problems in SSL 2.0 include: * Message integrity compromised. The SSLv2 message authentication uses the MD5 function, and is insecure. * Man-in-the-middle attack. There is no protection of the handshake in SSLv2, which permits a man-in-the-middle attack. * Truncation attack. SSLv2 relies on TCP FIN to close the session, so the attacker can forge a TCP FIN, and the peer cannot tell if it was a legitimate end of data or not. * Weak message integrity for export ciphers. The cryptographic keys in SSLv2 are used for both message authentication and encryption, so if weak encryption schemes are negotiated (say 40-bit keys) the message authentication code use the same weak key, which isn't necessary. Other protocols such as Microsoft's PCT 1 and PCT 2 were not implemented because they were also abandoned and deprecated by SSL 3.0 and later TLS 1.0.  File: gnutls.info, Node: Authentication methods, Next: More on certificate authentication, Prev: Introduction to TLS, Up: Top 4 Authentication Methods ************************ The TLS protocol provides confidentiality and encryption, but also offers authentication, which is a prerequisite for a secure connection. The available authentication methods in GnuTLS are: * Certificate authentication * Anonymous authentication * SRP authentication * PSK authentication * Menu: * Certificate authentication:: * Anonymous authentication:: * Authentication using SRP:: * Authentication using PSK:: * Authentication and credentials:: * Parameters stored in credentials::  File: gnutls.info, Node: Certificate authentication, Next: Anonymous authentication, Up: Authentication methods 4.1 Certificate Authentication ============================== 4.1.1 Authentication Using X.509 Certificates --------------------------------------------- X.509 certificates contain the public parameters, of a public key algorithm, and an authority's signature, which proves the authenticity of the parameters. *Note The X.509 trust model::, for more information on X.509 protocols. 4.1.2 Authentication Using OpenPGP Keys --------------------------------------- OpenPGP keys also contain public parameters of a public key algorithm, and signatures from several other parties. Depending on whether a signer is trusted the key is considered trusted or not. GnuTLS's OpenPGP authentication implementation is based on the [TLSPGP] (*note Bibliography::) proposal. *Note The OpenPGP trust model::, for more information about the OpenPGP trust model. For a more detailed introduction to OpenPGP and GnuPG see [GPGH] (*note Bibliography::). 4.1.3 Using Certificate Authentication -------------------------------------- In GnuTLS both the OpenPGP and X.509 certificates are part of the certificate authentication and thus are handled using a common API. When using certificates the server is required to have at least one certificate and private key pair. A client may or may not have such a pair. The certificate and key pair should be loaded, before any TLS session is initialized, in a certificate credentials structure. This should be done by using *Note gnutls_certificate_set_x509_key_file:: or *Note gnutls_certificate_set_openpgp_key_file:: depending on the certificate type. In the X.509 case, the functions will also accept and use a certificate list that leads to a trusted authority. The certificate list must be ordered in such way that every certificate certifies the one before it. The trusted authority's certificate need not to be included, since the peer should possess it already. As an alternative, a callback may be used so the server or the client specify the certificate and the key at the handshake time. That callback can be set using the functions: * *Note gnutls_certificate_server_set_retrieve_function:: * *Note gnutls_certificate_client_set_retrieve_function:: Clients and servers that will select certificates using callback functions should select a certificate according the peer's signature algorithm preferences. To get those preferences use *Note gnutls_sign_algorithm_get_requested::. Certificate verification is possible by loading the trusted authorities into the credentials structure by using *Note gnutls_certificate_set_x509_trust_file:: or *Note gnutls_certificate_set_openpgp_keyring_file:: for openpgp keys. Note however that the peer's certificate is not automatically verified, you should call *Note gnutls_certificate_verify_peers2::, after a successful handshake, to verify the signatures of the certificate. An alternative way, which reports a more detailed verification output, is to use *Note gnutls_certificate_get_peers:: to obtain the raw certificate of the peer and verify it using the functions discussed in *Note The X.509 trust model::. In a handshake, the negotiated cipher suite depends on the certificate's parameters, so not all key exchange methods will be available with some certificates. GnuTLS will disable ciphersuites that are not compatible with the key, or the enabled authentication methods. For example keys marked as sign-only, will not be able to access the plain RSA ciphersuites, but only the `DHE_RSA' ones. It is recommended not to use RSA keys for both signing and encryption. If possible use the same key for the `DHE_RSA' and `RSA_EXPORT' ciphersuites, which use signing, and a different key for the plain RSA ciphersuites, which use encryption. All the key exchange methods shown below are available in certificate authentication. Note that the DHE key exchange methods are generally slower(1) than plain RSA and require Diffie Hellman parameters to be generated and associated with a credentials structure, by the server. The `RSA-EXPORT' method also requires 512 bit RSA parameters, that should also be generated and associated with the credentials structure. See the functions: * *Note gnutls_dh_params_generate2:: * *Note gnutls_certificate_set_dh_params:: * *Note gnutls_rsa_params_generate2:: * *Note gnutls_certificate_set_rsa_export_params:: Sometimes in order to avoid bottlenecks in programs it is useful to store and read parameters from formats that can be generated by external programs such as `certtool'. This is possible with GnuTLS by using the following functions: * *Note gnutls_dh_params_import_pkcs3:: * *Note gnutls_rsa_params_import_pkcs1:: * *Note gnutls_dh_params_export_pkcs3:: * *Note gnutls_rsa_params_export_pkcs1:: Key exchange algorithms for OpenPGP and X.509 certificates: `RSA:' The RSA algorithm is used to encrypt a key and send it to the peer. The certificate must allow the key to be used for encryption. `RSA_EXPORT:' The RSA algorithm is used to encrypt a key and send it to the peer. In the EXPORT algorithm, the server signs temporary RSA parameters of 512 bits -- which are considered weak -- and sends them to the client. `DHE_RSA:' The RSA algorithm is used to sign Ephemeral Diffie-Hellman parameters which are sent to the peer. The key in the certificate must allow the key to be used for signing. Note that key exchange algorithms which use Ephemeral Diffie-Hellman parameters, offer perfect forward secrecy. That means that even if the private key used for signing is compromised, it cannot be used to reveal past session data. `DHE_DSS:' The DSS algorithm is used to sign Ephemeral Diffie-Hellman parameters which are sent to the peer. The certificate must contain DSA parameters to use this key exchange algorithm. DSS stands for Digital Signature Standard. ---------- Footnotes ---------- (1) It really depends on the group used. Primes with lesser bits are always faster, but also easier to break. Values less than 768 should not be used today  File: gnutls.info, Node: Anonymous authentication, Next: Authentication using SRP, Prev: Certificate authentication, Up: Authentication methods 4.2 Anonymous Authentication ============================ The anonymous key exchange performs encryption but there is no indication of the identity of the peer. This kind of authentication is vulnerable to a man in the middle attack, but this protocol can be used even if there is no prior communication and trusted parties with the peer, or when full anonymity is required. Unless really required, do not use anonymous authentication. Available key exchange methods are shown below. Note that the key exchange methods for anonymous authentication require Diffie-Hellman parameters to be generated by the server and associated with an anonymous credentials structure. Supported anonymous key exchange algorithms: `ANON_DH:' This algorithm exchanges Diffie-Hellman parameters.  File: gnutls.info, Node: Authentication using SRP, Next: Authentication using PSK, Prev: Anonymous authentication, Up: Authentication methods 4.3 Authentication using SRP ============================ Authentication via the Secure Remote Password protocol, SRP(1), is supported. The SRP key exchange is an extension to the TLS protocol, and it is a password based authentication (unlike X.509 or OpenPGP that use certificates). The two peers can be identified using a single password, or there can be combinations where the client is authenticated using SRP and the server using a certificate. The advantage of SRP authentication, over other proposed secure password authentication schemes, is that SRP does not require the server to hold the user's password. This kind of protection is similar to the one used traditionally in the _UNIX_ `/etc/passwd' file, where the contents of this file did not cause harm to the system security if they were revealed. The SRP needs instead of the plain password something called a verifier, which is calculated using the user's password, and if stolen cannot be used to impersonate the user. Check [TOMSRP] (*note Bibliography::) for a detailed description of the SRP protocol and the Stanford SRP libraries, which includes a PAM module that synchronizes the system's users passwords with the SRP password files. That way SRP authentication could be used for all the system's users. The implementation in GnuTLS is based on paper [TLSSRP] (*note Bibliography::). The supported SRP key exchange methods are: `SRP:' Authentication using the SRP protocol. `SRP_DSS:' Client authentication using the SRP protocol. Server is authenticated using a certificate with DSA parameters. `SRP_RSA:' Client authentication using the SRP protocol. Server is authenticated using a certificate with RSA parameters. If clients supporting SRP know the username and password before the connection, should initialize the client credentials and call the function *Note gnutls_srp_set_client_credentials::. Alternatively they could specify a callback function by using the function *Note gnutls_srp_set_client_credentials_function::. This has the advantage that allows probing the server for SRP support. In that case the callback function will be called twice per handshake. The first time is before the ciphersuite is negotiated, and if the callback returns a negative error code, the callback will be called again if SRP has been negotiated. This uses a special TLS-SRP handshake idiom in order to avoid, in interactive applications, to ask the user for SRP password and username if the server does not negotiate an SRP ciphersuite. In server side the default behaviour of GnuTLS is to read the usernames and SRP verifiers from password files. These password files are the ones used by the _Stanford srp libraries_ and can be specified using the *Note gnutls_srp_set_server_credentials_file::. If a different password file format is to be used, then the function *Note gnutls_srp_set_server_credentials_function::, should be called, in order to set an appropriate callback. Some helper functions such as * *Note gnutls_srp_verifier:: * *Note gnutls_srp_base64_encode:: * *Note gnutls_srp_base64_decode:: are included in GnuTLS, and can be used to generate and maintain SRP verifiers and password files. A program to manipulate the required parameters for SRP authentication is also included. *Note srptool::, for more information. ---------- Footnotes ---------- (1) SRP is described in [RFC2945] (*note Bibliography::)  File: gnutls.info, Node: Authentication using PSK, Next: Authentication and credentials, Prev: Authentication using SRP, Up: Authentication methods 4.4 Authentication using PSK ============================ Authentication using Pre-shared keys is a method to authenticate using usernames and binary keys. This protocol avoids making use of public key infrastructure and expensive calculations, thus it is suitable for constraint clients. The implementation in GnuTLS is based on paper [TLSPSK] (*note Bibliography::). The supported PSK key exchange methods are: `PSK:' Authentication using the PSK protocol. `DHE-PSK:' Authentication using the PSK protocol and Diffie-Hellman key exchange. This method offers perfect forward secrecy. Clients supporting PSK should supply the username and key before the connection to the client credentials by calling the function *Note gnutls_psk_set_client_credentials::. Alternatively they could specify a callback function by using the function *Note gnutls_psk_set_client_credentials_function::. This has the advantage that the callback will be called only if PSK has been negotiated. In server side the default behaviour of GnuTLS is to read the usernames and PSK keys from a password file. The password file should contain usernames and keys in hexadecimal format. The name of the password file can be stored to the credentials structure by calling *Note gnutls_psk_set_server_credentials_file::. If a different password file format is to be used, then the function *Note gnutls_psk_set_server_credentials_function::, should be used instead. The server can help the client chose a suitable username and password, by sending a hint. In the server, specify the hint by calling *Note gnutls_psk_set_server_credentials_hint::. The client can retrieve the hint, for example in the callback function, using *Note gnutls_psk_client_get_hint::. There is no mechanism to derive a PSK key from a password specified by the TLS PSK document(1). For password-based authentication check *Note Authentication using SRP::. Some helper functions such as: * *Note gnutls_hex_encode:: * *Note gnutls_hex_decode:: are included in GnuTLS, and may be used to generate and maintain PSK keys. ---------- Footnotes ---------- (1) GnuTLS used to provide `gnutls_psk_netconf_derive_key' which follows the algorithm specified in `draft-ietf-netconf-tls-02.txt'. This method is deprecated and might be removed in later versions of GnuTLS.  File: gnutls.info, Node: Authentication and credentials, Next: Parameters stored in credentials, Prev: Authentication using PSK, Up: Authentication methods 4.5 Authentication and Credentials ================================== In GnuTLS every key exchange method is associated with a credentials type. So in order to enable to enable a specific method, the corresponding credentials type should be initialized and set using *Note gnutls_credentials_set::. A mapping is shown below. Key exchange algorithms and the corresponding credential types: Key exchange Client credentials Server credentials --------------------------------------------------------------------- `KX_RSA' `KX_DHE_RSA' `KX_DHE_DSS' `KX_RSA_EXPORT' `CRD_CERTIFICATE' `CRD_CERTIFICATE' `KX_SRP_RSA' `CRD_SRP' `CRD_SRP' `KX_SRP_DSS' `CRD_CERTIFICATE' `KX_SRP' `CRD_SRP' `CRD_SRP' `KX_ANON_DH' `CRD_ANON' `CRD_ANON' `KX_PSK' `CRD_PSK' `CRD_PSK'  File: gnutls.info, Node: Parameters stored in credentials, Prev: Authentication and credentials, Up: Authentication methods 4.6 Parameters Stored in Credentials ==================================== Several parameters such as the ones used for Diffie-Hellman authentication are stored within the credentials structures, so all sessions can access them. Those parameters are stored in structures such as `gnutls_dh_params_t' and `gnutls_rsa_params_t', and functions like *Note gnutls_certificate_set_dh_params:: and *Note gnutls_certificate_set_rsa_export_params:: can be used to associate those parameters with the given credentials structure. Since those parameters need to be renewed from time to time and a global structure such as the credentials, may not be easy to modify since it is accessible by all sessions, an alternative interface is available using a callback function. This can be set using the *Note gnutls_certificate_set_params_function::. An example is shown below. #include gnutls_rsa_params_t rsa_params; gnutls_dh_params_t dh_params; /* This function will be called once a session requests DH * or RSA parameters. The parameters returned (if any) will * be used for the first handshake only. */ static int get_params( gnutls_session_t session, gnutls_params_type_t type, gnutls_params_st *st) { if (type == GNUTLS_PARAMS_RSA_EXPORT) st->params.rsa_export = rsa_params; else if (type == GNUTLS_PARAMS_DH) st->params.dh = dh_params; else return -1; st->type = type; /* do not deinitialize those parameters. */ st->deinit = 0; return 0; } int main() { gnutls_certificate_credentials_t cert_cred; initialize_params(); /* ... */ gnutls_certificate_set_params_function( cert_cred, get_params); }  File: gnutls.info, Node: More on certificate authentication, Next: How to use TLS in application protocols, Prev: Authentication methods, Up: Top 5 More on Certificate Authentication ************************************ * Menu: * The X.509 trust model:: * The OpenPGP trust model:: * PKCS #11 tokens:: * Abstract data types:: * Digital signatures::  File: gnutls.info, Node: The X.509 trust model, Next: The OpenPGP trust model, Up: More on certificate authentication 5.1 The X.509 Trust Model ========================= The X.509 protocols rely on a hierarchical trust model. In this trust model Certification Authorities (CAs) are used to certify entities. Usually more than one certification authorities exist, and certification authorities may certify other authorities to issue certificates as well, following a hierarchical model. [image src="gnutls-x509.png"] One needs to trust one or more CAs for his secure communications. In that case only the certificates issued by the trusted authorities are acceptable. See the figure above for a typical example. The API for handling X.509 certificates is described at section *Note sec:x509api::. Some examples are listed below. * Menu: * X.509 certificates:: * Verifying X.509 certificate paths:: * PKCS #10 certificate requests:: * PKCS #12 structures::  File: gnutls.info, Node: X.509 certificates, Next: Verifying X.509 certificate paths, Up: The X.509 trust model 5.1.1 X.509 Certificates ------------------------ An X.509 certificate usually contains information about the certificate holder, the signer, a unique serial number, expiration dates and some other fields [PKIX] (*note Bibliography::) as shown in the table below. `version:' The field that indicates the version of the certificate. `serialNumber:' This field holds a unique serial number per certificate. `issuer:' Holds the issuer's distinguished name. `validity:' The activation and expiration dates. `subject:' The subject's distinguished name of the certificate. `extensions:' The extensions are fields only present in version 3 certificates. The certificate's _subject or issuer name_ is not just a single string. It is a Distinguished name and in the ASN.1 notation is a sequence of several object IDs with their corresponding values. Some of available OIDs to be used in an X.509 distinguished name are defined in `gnutls/x509.h'. The _Version_ field in a certificate has values either 1 or 3 for version 3 certificates. Version 1 certificates do not support the extensions field so it is not possible to distinguish a CA from a person, thus their usage should be avoided. The _validity_ dates are there to indicate the date that the specific certificate was activated and the date the certificate's key would be considered invalid. Certificate _extensions_ are there to include information about the certificate's subject that did not fit in the typical certificate fields. Those may be e-mail addresses, flags that indicate whether the belongs to a CA etc. All the supported X.509 version 3 extensions are shown in the table below. `subject key id (2.5.29.14):' An identifier of the key of the subject. `authority key id (2.5.29.35):' An identifier of the authority's key used to sign the certificate. `subject alternative name (2.5.29.17):' Alternative names to subject's distinguished name. `key usage (2.5.29.15):' Constraints the key's usage of the certificate. `extended key usage (2.5.29.37):' Constraints the purpose of the certificate. `basic constraints (2.5.29.19):' Indicates whether this is a CA certificate or not, and specify the maximum path lengths of certificate chains. `CRL distribution points (2.5.29.31):' This extension is set by the CA, in order to inform about the issued CRLs. `Proxy Certification Information (1.3.6.1.5.5.7.1.14):' Proxy Certificates includes this extension that contains the OID of the proxy policy language used, and can specify limits on the maximum lengths of proxy chains. Proxy Certificates are specified in [RFC3820] (*note Bibliography::). In GnuTLS the X.509 certificate structures are handled using the `gnutls_x509_crt_t' type and the corresponding private keys with the `gnutls_x509_privkey_t' type. All the available functions for X.509 certificate handling have their prototypes in `gnutls/x509.h'. An example program to demonstrate the X.509 parsing capabilities can be found at section *Note ex:x509-info::.  File: gnutls.info, Node: Verifying X.509 certificate paths, Next: PKCS #10 certificate requests, Prev: X.509 certificates, Up: The X.509 trust model 5.1.2 Verifying X.509 Certificate Paths --------------------------------------- Verifying certificate paths is important in X.509 authentication. For this purpose the function *Note gnutls_x509_crt_verify:: is provided. The output of this function is the bitwise OR of the elements of the `gnutls_certificate_status_t' enumeration. A detailed description of these elements can be found in figure below. The function *Note gnutls_certificate_verify_peers2:: is equivalent to the previous one, and will verify the peer's certificate in a TLS session. `GNUTLS_CERT_INVALID:' The certificate is not signed by one of the known authorities, or the signature is invalid. `GNUTLS_CERT_REVOKED:' The certificate has been revoked by its CA. `GNUTLS_CERT_SIGNER_NOT_FOUND:' The certificate's issuer is not known. This is the case when the issuer is not in the trusted certificates list. `GNUTLS_CERT_SIGNER_NOT_CA:' The certificate's signer was not a CA. This may happen if this was a version 1 certificate, which is common with some CAs, or a version 3 certificate without the basic constrains extension. `GNUTLS_CERT_INSECURE_ALGORITHM:' The certificate was signed using an insecure algorithm such as MD2 or MD5. These algorithms have been broken and should not be trusted. There is also to possibility to pass some input to the verification functions in the form of flags. For *Note gnutls_x509_crt_verify:: the flags are passed straightforward, but *Note gnutls_certificate_verify_peers2:: depends on the flags set by calling *Note gnutls_certificate_set_verify_flags::. All the available flags are part of the enumeration *Note gnutls_certificate_verify_flags:: and are explained in the table below. `GNUTLS_VERIFY_DISABLE_CA_SIGN:' If set a signer does not have to be a certificate authority. This flag should normaly be disabled, unless you know what this means. `GNUTLS_VERIFY_ALLOW_X509_V1_CA_CRT:' Allow only trusted CA certificates that have version 1. This is safer than GNUTLS_VERIFY_ALLOW_ANY_X509_V1_CA_CRT, and should be used instead. That way only signers in your trusted list will be allowed to have certificates of version 1. `GNUTLS_VERIFY_ALLOW_ANY_X509_V1_CA_CRT:' Allow CA certificates that have version 1 (both root and intermediate). This is dangerous since those haven't the basicConstraints extension. Must be used in combination with GNUTLS_VERIFY_ALLOW_X509_V1_CA_CRT. `GNUTLS_VERIFY_DO_NOT_ALLOW_SAME:' If a certificate is not signed by anyone trusted but exists in the trusted CA list do not treat it as trusted. `GNUTLS_VERIFY_ALLOW_SIGN_RSA_MD2:' Allow certificates to be signed using the old MD2 algorithm. `GNUTLS_VERIFY_ALLOW_SIGN_RSA_MD5:' Allow certificates to be signed using the broken MD5 algorithm. Although the verification of a certificate path indicates that the certificate is signed by trusted authority, does not reveal anything about the peer's identity. It is required to verify if the certificate's owner is the one you expect. For more information consult [RFC2818] (*note Bibliography::) and section *Note ex:verify:: for an example.  File: gnutls.info, Node: PKCS #10 certificate requests, Next: PKCS #12 structures, Prev: Verifying X.509 certificate paths, Up: The X.509 trust model 5.1.3 PKCS #10 Certificate Requests ----------------------------------- A certificate request is a structure, which contain information about an applicant of a certificate service. It usually contains a private key, a distinguished name and secondary data such as a challenge password. GnuTLS supports the requests defined in PKCS #10 [RFC2986] (*note Bibliography::). Other certificate request's format such as PKIX's [RFC4211] (*note Bibliography::) are not currently supported. In GnuTLS the PKCS #10 structures are handled using the `gnutls_x509_crq_t' type. An example of a certificate request generation can be found at section *Note ex:crq::.  File: gnutls.info, Node: PKCS #12 structures, Prev: PKCS #10 certificate requests, Up: The X.509 trust model 5.1.4 PKCS #12 Structures ------------------------- A PKCS #12 structure [PKCS12] (*note Bibliography::) usually contains a user's private keys and certificates. It is commonly used in browsers to export and import the user's identities. In GnuTLS the PKCS #12 structures are handled using the `gnutls_pkcs12_t' type. This is an abstract type that may hold several `gnutls_pkcs12_bag_t' types. The Bag types are the holders of the actual data, which may be certificates, private keys or encrypted data. An Bag of type encrypted should be decrypted in order for its data to be accessed. An example of a PKCS #12 structure generation can be found at section *Note ex:pkcs12::.  File: gnutls.info, Node: The OpenPGP trust model, Next: PKCS #11 tokens, Prev: The X.509 trust model, Up: More on certificate authentication 5.2 The OpenPGP Trust Model =========================== The OpenPGP key authentication relies on a distributed trust model, called the "web of trust". The "web of trust" uses a decentralized system of trusted introducers, which are the same as a CA. OpenPGP allows anyone to sign anyone's else public key. When Alice signs Bob's key, she is introducing Bob's key to anyone who trusts Alice. If someone trusts Alice to introduce keys, then Alice is a trusted introducer in the mind of that observer. [image src="gnutls-pgp.png"] For example: If David trusts Alice to be an introducer, and Alice signed Bob's key, Dave also trusts Bob's key to be the real one. There are some key points that are important in that model. In the example Alice has to sign Bob's key, only if she is sure that the key belongs to Bob. Otherwise she may also make Dave falsely believe that this is Bob's key. Dave has also the responsibility to know who to trust. This model is similar to real life relations. Just see how Charlie behaves in the previous example. Although he has signed Bob's key - because he knows, somehow, that it belongs to Bob - he does not trust Bob to be an introducer. Charlie decided to trust only Kevin, for some reason. A reason could be that Bob is lazy enough, and signs other people's keys without being sure that they belong to the actual owner. 5.2.1 OpenPGP Keys ------------------ In GnuTLS the OpenPGP key structures [RFC2440] (*note Bibliography::) are handled using the `gnutls_openpgp_crt_t' type and the corresponding private keys with the `gnutls_openpgp_privkey_t' type. All the prototypes for the key handling functions can be found at `gnutls/openpgp.h'. 5.2.2 Verifying an OpenPGP Key ------------------------------ The verification functions of OpenPGP keys, included in GnuTLS, are simple ones, and do not use the features of the "web of trust". For that reason, if the verification needs are complex, the assistance of external tools like GnuPG and GPGME (`http://www.gnupg.org/related_software/gpgme/') is recommended. There is one verification function in GnuTLS, the *Note gnutls_openpgp_crt_verify_ring::. This checks an OpenPGP key against a given set of public keys (keyring) and returns the key status. The key verification status is the same as in X.509 certificates, although the meaning and interpretation are different. For example an OpenPGP key may be valid, if the self signature is ok, even if no signers were found. The meaning of verification status is shown in the figure below. `CERT_INVALID:' A signature on the key is invalid. That means that the key was modified by somebody, or corrupted during transport. `CERT_REVOKED:' The key has been revoked by its owner. `CERT_SIGNER_NOT_FOUND:' The key was not signed by a known signer. `GNUTLS_CERT_INSECURE_ALGORITHM:' The certificate was signed using an insecure algorithm such as MD2 or MD5. These algorithms have been broken and should not be trusted.  File: gnutls.info, Node: PKCS #11 tokens, Next: Abstract data types, Prev: The OpenPGP trust model, Up: More on certificate authentication 5.3 PKCS #11 tokens =================== 5.3.1 Introduction ------------------ This section copes with the PKCS #11 [PKCS11] (*note Bibliography::) support in GnuTLS. PKCS #11 is plugin API allowing applications to access cryptographic operations on a token, as well as to objects residing on the token. A token can be a real hardware token such as a smart card, or it can be a software component such as Gnome Keyring. The objects residing on such token can be certificates, public keys, private keys or even plain data or secret keys. Of those certificates and public/private key pairs can be used with GnuTLS. Its main advantage is that it allows operations on private key objects such as decryption and signing without accessing the key itself. Moreover it can be used to allow all applications in the same operating system to access shared cryptographic keys and certificates in a uniform way, as in the following picture. [image src="pkcs11-vision.png"] 5.3.2 Initialization -------------------- To allow all the GnuTLS applications to access PKCS #11 tokens you can use a configuration per module, such as `/etc/pkcs11/modules/mymodule.conf'. This file has the following format: module: /usr/lib/opensc-pkcs11.so If you use this file, then there is no need for other initialization in GnuTLS, except for the PIN and token functions. Those allow retrieving a PIN when accessing a protected object, such as a private key, as well as probe the user to insert the token. All the initialization functions are below. * *Note gnutls_pkcs11_init::: Global initialization * *Note gnutls_pkcs11_deinit::: Global deinitialization * *Note gnutls_pkcs11_set_token_function::: Sets the token insertion function * *Note gnutls_pkcs11_set_pin_function::: Sets the PIN request function * *Note gnutls_pkcs11_add_provider::: Adds an additional PKCS #11 provider Note that due to limitations of PKCS #11 there might be issues when multiple libraries are sharing a module. If this is the case we suggest to use p11-kit(1) that provides an intermediate module to control access to resources over the multiple users. 5.3.3 Reading Objects --------------------- All PKCS #11 objects are referenced by GnuTLS functions by URLs as described in `draft-pechanec-pkcs11uri-03'. For example a public key on a smart card may be referenced as: pkcs11:token=Nikos;serial=307521161601031;model=PKCS%2315; \ manufacturer=EnterSafe;object=test1;objecttype=public;\ id=32:f1:53:f3:e3:79:90:b0:86:24:14:10:77:ca:5d:ec:2d:15:fa:ed while the smart card itself can be referenced as: pkcs11:token=Nikos;serial=307521161601031;model=PKCS%2315;manufacturer=EnterSafe Objects can be accessed with the following functions * *Note gnutls_pkcs11_obj_init::: Initializes an object * *Note gnutls_pkcs11_obj_import_url::: To import an object from a url * *Note gnutls_pkcs11_obj_export_url::: To export the URL of the object * *Note gnutls_pkcs11_obj_deinit::: To deinitialize an object * *Note gnutls_pkcs11_obj_export::: To export data associated with object * *Note gnutls_pkcs11_obj_get_info::: To obtain information about an object * *Note gnutls_pkcs11_obj_list_import_url::: To mass load of objects * *Note gnutls_x509_crt_import_pkcs11::: Import a certificate object * *Note gnutls_x509_crt_import_pkcs11_url::: Helper function to directly import a URL into a certificate * *Note gnutls_x509_crt_list_import_pkcs11::: Mass import of certificates Functions that relate to token handling are shown below * *Note gnutls_pkcs11_token_init::: Initializes a token * *Note gnutls_pkcs11_token_set_pin::: Sets the token user's PIN * *Note gnutls_pkcs11_token_get_url::: Returns the URL of a token * *Note gnutls_pkcs11_token_get_info::: Obtain information about a token * *Note gnutls_pkcs11_token_get_flags::: Returns flags about a token (i.e. hardware or software) The following example will list all tokens. int i; char* url; gnutls_global_init(); for (i=0;;i++) { ret = gnutls_pkcs11_token_get_url(i, &url); if (ret == GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE) break; if (ret < 0) exit(1); fprintf(stdout, "Token[%d]: URL: %s\n", i, url); gnutls_free(url); } gnutls_global_deinit(); The next one will list all certificates in a token, that have a corresponding private key: gnutls_pkcs11_obj_t *obj_list; unsigned int obj_list_size = 0; gnutls_datum_t cinfo; int i; obj_list_size = 0; ret = gnutls_pkcs11_obj_list_import_url( obj_list, NULL, url, \ GNUTLS_PKCS11_OBJ_ATTR_CRT_WITH_PRIVKEY); if (ret < 0 && ret != GNUTLS_E_SHORT_MEMORY_BUFFER) exit(1); /* no error checking from now on */ obj_list = malloc(sizeof(*obj_list)*obj_list_size); gnutls_pkcs11_obj_list_import_url( obj_list, &obj_list_size, url, flags); /* now all certificates are in obj_list */ for (i=0;i #inlude void sign_cert( gnutls_x509_crt_t to_be_signed) { gnutls_pkcs11_privkey_t ca_key; gnutls_x509_crt_t ca_cert; gnutls_privkey_t abs_key; /* load the PKCS #11 key and certificates */ gnutls_pkcs11_privkey_init(&ca_key); gnutls_pkcs11_privkey_import_url(ca_key, key_url); gnutls_x509_crt_init(&ca_cert); gnutls_x509_crt_import_pkcs11_url(&ca_cert, cert_url); /* initialize the abstract key */ gnutls_privkey_init(&abs_key); gnutls_privkey_import_pkcs11(abs_key, ca_key); /* sign the certificate to be signed */ gnutls_x509_crt_privkey_sign(to_be_signed, ca_cert, ca_key, GNUTLS_DIG_SHA1, 0); }  File: gnutls.info, Node: Digital signatures, Prev: Abstract data types, Up: More on certificate authentication 5.5 Digital Signatures ====================== In this section we will provide some information about digital signatures, how they work, and give the rationale for disabling some of the algorithms used. Digital signatures work by using somebody's secret key to sign some arbitrary data. Then anybody else could use the public key of that person to verify the signature. Since the data may be arbitrary it is not suitable input to a cryptographic digital signature algorithm. For this reason and also for performance cryptographic hash algorithms are used to preprocess the input to the signature algorithm. This works as long as it is difficult enough to generate two different messages with the same hash algorithm output. In that case the same signature could be used as a proof for both messages. Nobody wants to sign an innocent message of donating 1 euro to Greenpeace and find out that he donated 1.000.000 euros to Bad Inc. For a hash algorithm to be called cryptographic the following three requirements must hold: 1. Preimage resistance. That means the algorithm must be one way and given the output of the hash function H(x), it is impossible to calculate x. 2. 2nd preimage resistance. That means that given a pair x,y with y=H(x) it is impossible to calculate an x' such that y=H(x'). 3. Collision resistance. That means that it is impossible to calculate random x and x' such H(x')=H(x). The last two requirements in the list are the most important in digital signatures. These protect against somebody who would like to generate two messages with the same hash output. When an algorithm is considered broken usually it means that the Collision resistance of the algorithm is less than brute force. Using the birthday paradox the brute force attack takes 2^((hash size) / 2) operations. Today colliding certificates using the MD5 hash algorithm have been generated as shown in [WEGER] (*note Bibliography::). There has been cryptographic results for the SHA-1 hash algorithms as well, although they are not yet critical. Before 2004, MD5 had a presumed collision strength of 2^64, but it has been showed to have a collision strength well under 2^50. As of November 2005, it is believed that SHA-1's collision strength is around 2^63. We consider this sufficiently hard so that we still support SHA-1. We anticipate that SHA-256/386/512 will be used in publicly-distributed certificates in the future. When 2^63 can be considered too weak compared to the computer power available sometime in the future, SHA-1 will be disabled as well. The collision attacks on SHA-1 may also get better, given the new interest in tools for creating them. 5.5.1 Trading Security for Interoperability ------------------------------------------- If you connect to a server and use GnuTLS' functions to verify the certificate chain, and get a *Note GNUTLS_CERT_INSECURE_ALGORITHM:: validation error (*note Verifying X.509 certificate paths::), it means that somewhere in the certificate chain there is a certificate signed using `RSA-MD2' or `RSA-MD5'. These two digital signature algorithms are considered broken, so GnuTLS fail when attempting to verify the certificate. In some situations, it may be useful to be able to verify the certificate chain anyway, assuming an attacker did not utilize the fact that these signatures algorithms are broken. This section will give help on how to achieve that. First, it is important to know that you do not have to enable any of the flags discussed here to be able to use trusted root CA certificates signed using `RSA-MD2' or `RSA-MD5'. The only attack today is that it is possible to generate certificates with colliding signatures (collision resistance); you cannot generate a certificate that has the same signature as an already existing signature (2nd preimage resistance). If you are using *Note gnutls_certificate_verify_peers2:: to verify the certificate chain, you can call *Note gnutls_certificate_set_verify_flags:: with the `GNUTLS_VERIFY_ALLOW_SIGN_RSA_MD2' or `GNUTLS_VERIFY_ALLOW_SIGN_RSA_MD5' flag, as in: gnutls_certificate_set_verify_flags (x509cred, GNUTLS_VERIFY_ALLOW_SIGN_RSA_MD5); This will tell the verifier algorithm to enable `RSA-MD5' when verifying the certificates. If you are using *Note gnutls_x509_crt_verify:: or *Note gnutls_x509_crt_list_verify::, you can pass the `GNUTLS_VERIFY_ALLOW_SIGN_RSA_MD5' parameter directly in the `flags' parameter. If you are using these flags, it may also be a good idea to warn the user when verification failure occur for this reason. The simplest is to not use the flags by default, and only fall back to using them after warning the user. If you wish to inspect the certificate chain yourself, you can use *Note gnutls_certificate_get_peers:: to extract the raw server's certificate chain, then use *Note gnutls_x509_crt_import:: to parse each of the certificates, and then use *Note gnutls_x509_crt_get_signature_algorithm:: to find out the signing algorithm used for each certificate. If any of the intermediary certificates are using `GNUTLS_SIGN_RSA_MD2' or `GNUTLS_SIGN_RSA_MD5', you could present a warning.  File: gnutls.info, Node: How to use TLS in application protocols, Next: How to use GnuTLS in applications, Prev: More on certificate authentication, Up: Top 6 How To Use TLS in Application Protocols ***************************************** This chapter is intended to provide some hints on how to use the TLS over simple custom made application protocols. The discussion below mainly refers to the _TCP/IP_ transport layer but may be extended to other ones too. * Menu: * Separate ports:: * Upward negotiation::  File: gnutls.info, Node: Separate ports, Next: Upward negotiation, Up: How to use TLS in application protocols 6.1 Separate Ports ================== Traditionally SSL was used in application protocols by assigning a new port number for the secure services. That way two separate ports were assigned, one for the non secure sessions, and one for the secured ones. This has the benefit that if a user requests a secure session then the client will try to connect to the secure port and fail otherwise. The only possible attack with this method is a denial of service one. The most famous example of this method is the famous "HTTP over TLS" or HTTPS protocol [RFC2818] (*note Bibliography::). Despite its wide use, this method is not as good as it seems. This approach starts the TLS Handshake procedure just after the client connects on the --so called-- secure port. That way the TLS protocol does not know anything about the client, and popular methods like the host advertising in HTTP do not work(1). There is no way for the client to say "I connected to YYY server" before the Handshake starts, so the server cannot possibly know which certificate to use. Other than that it requires two separate ports to run a single service, which is unnecessary complication. Due to the fact that there is a limitation on the available privileged ports, this approach was soon obsoleted. ---------- Footnotes ---------- (1) See also the Server Name Indication extension on *Note serverind::.  File: gnutls.info, Node: Upward negotiation, Prev: Separate ports, Up: How to use TLS in application protocols 6.2 Upward Negotiation ====================== Other application protocols(1) use a different approach to enable the secure layer. They use something called the "TLS upgrade" method. This method is quite tricky but it is more flexible. The idea is to extend the application protocol to have a "STARTTLS" request, whose purpose it to start the TLS protocols just after the client requests it. This is a really neat idea and does not require an extra port. This method is used by almost all modern protocols and there is even the [RFC2817] (*note Bibliography::) paper which proposes extensions to HTTP to support it. The tricky part, in this method, is that the "STARTTLS" request is sent in the clear, thus is vulnerable to modifications. A typical attack is to modify the messages in a way that the client is fooled and thinks that the server does not have the "STARTTLS" capability. See a typical conversation of a hypothetical protocol: (client connects to the server) CLIENT: HELLO I'M MR. XXX SERVER: NICE TO MEET YOU XXX CLIENT: PLEASE START TLS SERVER: OK *** TLS STARTS CLIENT: HERE ARE SOME CONFIDENTIAL DATA And see an example of a conversation where someone is acting in between: (client connects to the server) CLIENT: HELLO I'M MR. XXX SERVER: NICE TO MEET YOU XXX CLIENT: PLEASE START TLS (here someone inserts this message) SERVER: SORRY I DON'T HAVE THIS CAPABILITY CLIENT: HERE ARE SOME CONFIDENTIAL DATA As you can see above the client was fooled, and was dummy enough to send the confidential data in the clear. How to avoid the above attack? As you may have already thought this one is easy to avoid. The client has to ask the user before it connects whether the user requests TLS or not. If the user answered that he certainly wants the secure layer the last conversation should be: (client connects to the server) CLIENT: HELLO I'M MR. XXX SERVER: NICE TO MEET YOU XXX CLIENT: PLEASE START TLS (here someone inserts this message) SERVER: SORRY I DON'T HAVE THIS CAPABILITY CLIENT: BYE (the client notifies the user that the secure connection was not possible) This method, if implemented properly, is far better than the traditional method, and the security properties remain the same, since only denial of service is possible. The benefit is that the server may request additional data before the TLS Handshake protocol starts, in order to send the correct certificate, use the correct password file(2), or anything else! ---------- Footnotes ---------- (1) See LDAP, IMAP etc. (2) in SRP authentication  File: gnutls.info, Node: How to use GnuTLS in applications, Next: Included programs, Prev: How to use TLS in application protocols, Up: Top 7 How To Use GnuTLS in Applications *********************************** * Menu: * Preparation:: * Multi-threaded applications:: * Client examples:: * Server examples:: * Miscellaneous examples:: * Parameter generation:: * Keying Material Exporters:: * Channel Bindings:: * Compatibility with the OpenSSL library::  File: gnutls.info, Node: Preparation, Next: Multi-threaded applications, Up: How to use GnuTLS in applications 7.1 Preparation =============== To use GnuTLS, you have to perform some changes to your sources and your build system. The necessary changes are explained in the following subsections. * Menu: * Headers:: * Initialization:: * Version check:: * Debugging:: * Building the source::  File: gnutls.info, Node: Headers, Next: Initialization, Up: Preparation 7.1.1 Headers ------------- All the data types and functions of the GnuTLS library are defined in the header file `gnutls/gnutls.h'. This must be included in all programs that make use of the GnuTLS library. The extra functionality of the GnuTLS-extra library is available by including the header file `gnutls/extra.h' in your programs.  File: gnutls.info, Node: Initialization, Next: Version check, Prev: Headers, Up: Preparation 7.1.2 Initialization -------------------- GnuTLS must be initialized before it can be used. The library is initialized by calling *Note gnutls_global_init::. The resources allocated by the initialization process can be released if the application no longer has a need to call GnuTLS functions, this is done by calling *Note gnutls_global_deinit::. The extra functionality of the GnuTLS-extra library is available after calling *Note gnutls_global_init_extra::. In order to take advantage of the internationalisation features in GnuTLS, such as translated error messages, the application must set the current locale using `setlocale' before initializing GnuTLS.  File: gnutls.info, Node: Version check, Next: Debugging, Prev: Initialization, Up: Preparation 7.1.3 Version Check ------------------- It is often desirable to check that the version of `gnutls' used is indeed one which fits all requirements. Even with binary compatibility new features may have been introduced but due to problem with the dynamic linker an old version is actually used. So you may want to check that the version is okay right after program startup. See the function *Note gnutls_check_version::.  File: gnutls.info, Node: Debugging, Next: Building the source, Prev: Version check, Up: Preparation 7.1.4 Debugging --------------- In many cases things may not go as expected and further information, to assist debugging, from GnuTLS is desired. Those are the case where the *Note gnutls_global_set_log_level:: and *Note gnutls_global_set_log_function:: are to be used. Those will print verbose information on the GnuTLS functions internal flow.  File: gnutls.info, Node: Building the source, Prev: Debugging, Up: Preparation 7.1.5 Building the Source ------------------------- If you want to compile a source file including the `gnutls/gnutls.h' header file, you must make sure that the compiler can find it in the directory hierarchy. This is accomplished by adding the path to the directory in which the header file is located to the compilers include file search path (via the `-I' option). However, the path to the include file is determined at the time the source is configured. To solve this problem, the library uses the external package `pkg-config' that knows the path to the include file and other configuration options. The options that need to be added to the compiler invocation at compile time are output by the `--cflags' option to `pkg-config gnutls'. The following example shows how it can be used at the command line: gcc -c foo.c `pkg-config gnutls --cflags` Adding the output of `pkg-config gnutls --cflags' to the compilers command line will ensure that the compiler can find the `gnutls/gnutls.h' header file. A similar problem occurs when linking the program with the library. Again, the compiler has to find the library files. For this to work, the path to the library files has to be added to the library search path (via the `-L' option). For this, the option `--libs' to `pkg-config gnutls' can be used. For convenience, this option also outputs all other options that are required to link the program with the libarary (for instance, the `-ltasn1' option). The example shows how to link `foo.o' with the library to a program `foo'. gcc -o foo foo.o `pkg-config gnutls --libs` Of course you can also combine both examples to a single command by specifying both options to `pkg-config': gcc -o foo foo.c `pkg-config gnutls --cflags --libs`  File: gnutls.info, Node: Multi-threaded applications, Next: Client examples, Prev: Preparation, Up: How to use GnuTLS in applications 7.2 Multi-Threaded Applications =============================== Although the GnuTLS library is thread safe by design, some parts of the cryptographic backend, such as the random generator, are not. Applications can either call *Note gnutls_global_init:: and use the default operating system provided locks (i.e. `pthreads' on GNU/Linux), or specify manualy the locking system using the function *Note gnutls_global_set_mutex:: before calling *Note gnutls_global_init::. Setting manually mutexes is recommended only to applications that have full control of the underlying libraries. If this is not the case, the use of the operating system defaults is recommended. There are helper macros to help you properly initialize the libraries. Examples are shown below. * POSIX threads in GNU/Linux #include #include #include int main() { gnutls_global_init(); } * Other thread packages int main() { gnutls_global_mutex_set (mutex_init, mutex_deinit, mutex_lock, mutex_unlock); gnutls_global_init(); }  File: gnutls.info, Node: Client examples, Next: Server examples, Prev: Multi-threaded applications, Up: How to use GnuTLS in applications 7.3 Client Examples =================== This section contains examples of TLS and SSL clients, using GnuTLS. Note that these examples contain little or no error checking. Some of the examples require functions implemented by another example. * Menu: * Simple client example with anonymous authentication:: * Simple client example with X.509 certificate support:: * Obtaining session information:: * Verifying peer's certificate:: * Using a callback to select the certificate to use:: * Client using a PKCS #11 token with TLS:: * Client with Resume capability example:: * Simple client example with SRP authentication:: * Simple client example in C++:: * Helper function for TCP connections::  File: gnutls.info, Node: Simple client example with anonymous authentication, Next: Simple client example with X.509 certificate support, Up: Client examples 7.3.1 Simple Client Example with Anonymous Authentication --------------------------------------------------------- The simplest client using TLS is the one that doesn't do any authentication. This means no external certificates or passwords are needed to set up the connection. As could be expected, the connection is vulnerable to man-in-the-middle (active or redirection) attacks. However, the data is integrity and privacy protected. /* This example code is placed in the public domain. */ #ifdef HAVE_CONFIG_H #include #endif #include #include #include #include #include #include #include #include /* A very basic TLS client, with anonymous authentication. */ #define MAX_BUF 1024 #define MSG "GET / HTTP/1.0\r\n\r\n" extern int tcp_connect (void); extern void tcp_close (int sd); int main (void) { int ret, sd, ii; gnutls_session_t session; char buffer[MAX_BUF + 1]; gnutls_anon_client_credentials_t anoncred; /* Need to enable anonymous KX specifically. */ gnutls_global_init (); gnutls_anon_allocate_client_credentials (&anoncred); /* Initialize TLS session */ gnutls_init (&session, GNUTLS_CLIENT); /* Use default priorities */ gnutls_priority_set_direct (session, "PERFORMANCE:+ANON-DH:!ARCFOUR-128", NULL); /* put the anonymous credentials to the current session */ gnutls_credentials_set (session, GNUTLS_CRD_ANON, anoncred); /* connect to the peer */ sd = tcp_connect (); gnutls_transport_set_ptr (session, (gnutls_transport_ptr_t) sd); /* Perform the TLS handshake */ ret = gnutls_handshake (session); if (ret < 0) { fprintf (stderr, "*** Handshake failed\n"); gnutls_perror (ret); goto end; } else { printf ("- Handshake was completed\n"); } gnutls_record_send (session, MSG, strlen (MSG)); ret = gnutls_record_recv (session, buffer, MAX_BUF); if (ret == 0) { printf ("- Peer has closed the TLS connection\n"); goto end; } else if (ret < 0) { fprintf (stderr, "*** Error: %s\n", gnutls_strerror (ret)); goto end; } printf ("- Received %d bytes: ", ret); for (ii = 0; ii < ret; ii++) { fputc (buffer[ii], stdout); } fputs ("\n", stdout); gnutls_bye (session, GNUTLS_SHUT_RDWR); end: tcp_close (sd); gnutls_deinit (session); gnutls_anon_free_client_credentials (anoncred); gnutls_global_deinit (); return 0; }  File: gnutls.info, Node: Simple client example with X.509 certificate support, Next: Obtaining session information, Prev: Simple client example with anonymous authentication, Up: Client examples 7.3.2 Simple Client Example with X.509 Certificate Support ---------------------------------------------------------- Let's assume now that we want to create a TCP client which communicates with servers that use X.509 or OpenPGP certificate authentication. The following client is a very simple TLS client, it does not support session resuming, not even certificate verification. The TCP functions defined in this example are used in most of the other examples below, without redefining them. /* This example code is placed in the public domain. */ #ifdef HAVE_CONFIG_H #include #endif #include #include #include #include #include #include #include #include /* A very basic TLS client, with X.509 authentication. */ #define MAX_BUF 1024 #define CAFILE "ca.pem" #define MSG "GET / HTTP/1.0\r\n\r\n" extern int tcp_connect (void); extern void tcp_close (int sd); int main (void) { int ret, sd, ii; gnutls_session_t session; char buffer[MAX_BUF + 1]; const char *err; gnutls_certificate_credentials_t xcred; gnutls_global_init (); /* X509 stuff */ gnutls_certificate_allocate_credentials (&xcred); /* sets the trusted cas file */ gnutls_certificate_set_x509_trust_file (xcred, CAFILE, GNUTLS_X509_FMT_PEM); /* Initialize TLS session */ gnutls_init (&session, GNUTLS_CLIENT); /* Use default priorities */ ret = gnutls_priority_set_direct (session, "PERFORMANCE", &err); if (ret < 0) { if (ret == GNUTLS_E_INVALID_REQUEST) { fprintf (stderr, "Syntax error at: %s\n", err); } exit (1); } /* put the x509 credentials to the current session */ gnutls_credentials_set (session, GNUTLS_CRD_CERTIFICATE, xcred); /* connect to the peer */ sd = tcp_connect (); gnutls_transport_set_ptr (session, (gnutls_transport_ptr_t) sd); /* Perform the TLS handshake */ ret = gnutls_handshake (session); if (ret < 0) { fprintf (stderr, "*** Handshake failed\n"); gnutls_perror (ret); goto end; } else { printf ("- Handshake was completed\n"); } gnutls_record_send (session, MSG, strlen (MSG)); ret = gnutls_record_recv (session, buffer, MAX_BUF); if (ret == 0) { printf ("- Peer has closed the TLS connection\n"); goto end; } else if (ret < 0) { fprintf (stderr, "*** Error: %s\n", gnutls_strerror (ret)); goto end; } printf ("- Received %d bytes: ", ret); for (ii = 0; ii < ret; ii++) { fputc (buffer[ii], stdout); } fputs ("\n", stdout); gnutls_bye (session, GNUTLS_SHUT_RDWR); end: tcp_close (sd); gnutls_deinit (session); gnutls_certificate_free_credentials (xcred); gnutls_global_deinit (); return 0; }  File: gnutls.info, Node: Obtaining session information, Next: Verifying peer's certificate, Prev: Simple client example with X.509 certificate support, Up: Client examples 7.3.3 Obtaining Session Information ----------------------------------- Most of the times it is desirable to know the security properties of the current established session. This includes the underlying ciphers and the protocols involved. That is the purpose of the following function. Note that this function will print meaningful values only if called after a successful *Note gnutls_handshake::. /* This example code is placed in the public domain. */ #ifdef HAVE_CONFIG_H #include #endif #include #include #include #include #include "examples.h" /* This function will print some details of the * given session. */ int print_info (gnutls_session_t session) { const char *tmp; gnutls_credentials_type_t cred; gnutls_kx_algorithm_t kx; /* print the key exchange's algorithm name */ kx = gnutls_kx_get (session); tmp = gnutls_kx_get_name (kx); printf ("- Key Exchange: %s\n", tmp); /* Check the authentication type used and switch * to the appropriate. */ cred = gnutls_auth_get_type (session); switch (cred) { case GNUTLS_CRD_IA: printf ("- TLS/IA session\n"); break; #ifdef ENABLE_SRP case GNUTLS_CRD_SRP: printf ("- SRP session with username %s\n", gnutls_srp_server_get_username (session)); break; #endif case GNUTLS_CRD_PSK: /* This returns NULL in server side. */ if (gnutls_psk_client_get_hint (session) != NULL) printf ("- PSK authentication. PSK hint '%s'\n", gnutls_psk_client_get_hint (session)); /* This returns NULL in client side. */ if (gnutls_psk_server_get_username (session) != NULL) printf ("- PSK authentication. Connected as '%s'\n", gnutls_psk_server_get_username (session)); break; case GNUTLS_CRD_ANON: /* anonymous authentication */ printf ("- Anonymous DH using prime of %d bits\n", gnutls_dh_get_prime_bits (session)); break; case GNUTLS_CRD_CERTIFICATE: /* certificate authentication */ /* Check if we have been using ephemeral Diffie-Hellman. */ if (kx == GNUTLS_KX_DHE_RSA || kx == GNUTLS_KX_DHE_DSS) { printf ("\n- Ephemeral DH using prime of %d bits\n", gnutls_dh_get_prime_bits (session)); } /* if the certificate list is available, then * print some information about it. */ print_x509_certificate_info (session); } /* switch */ /* print the protocol's name (ie TLS 1.0) */ tmp = gnutls_protocol_get_name (gnutls_protocol_get_version (session)); printf ("- Protocol: %s\n", tmp); /* print the certificate type of the peer. * ie X.509 */ tmp = gnutls_certificate_type_get_name (gnutls_certificate_type_get (session)); printf ("- Certificate Type: %s\n", tmp); /* print the compression algorithm (if any) */ tmp = gnutls_compression_get_name (gnutls_compression_get (session)); printf ("- Compression: %s\n", tmp); /* print the name of the cipher used. * ie 3DES. */ tmp = gnutls_cipher_get_name (gnutls_cipher_get (session)); printf ("- Cipher: %s\n", tmp); /* Print the MAC algorithms name. * ie SHA1 */ tmp = gnutls_mac_get_name (gnutls_mac_get (session)); printf ("- MAC: %s\n", tmp); return 0; }  File: gnutls.info, Node: Verifying peer's certificate, Next: Using a callback to select the certificate to use, Prev: Obtaining session information, Up: Client examples 7.3.4 Verifying Peer's Certificate ---------------------------------- A TLS session is not secure just after the handshake procedure has finished. It must be considered secure, only after the peer's certificate and identity have been verified. That is, you have to verify the signature in peer's certificate, the hostname in the certificate, and expiration dates. Just after this step you should treat the connection as being a secure one. /* This example code is placed in the public domain. */ #ifdef HAVE_CONFIG_H #include #endif #include #include #include #include #include #include "examples.h" /* A very basic TLS client, with X.509 authentication and server certificate * verification. */ #define MAX_BUF 1024 #define CAFILE "ca.pem" #define MSG "GET / HTTP/1.0\r\n\r\n" extern int tcp_connect (void); extern void tcp_close (int sd); /* This function will try to verify the peer's certificate, and * also check if the hostname matches, and the activation, expiration dates. */ static int verify_certificate_callback (gnutls_session_t session) { unsigned int status; const gnutls_datum_t *cert_list; unsigned int cert_list_size; int ret; gnutls_x509_crt_t cert; const char *hostname; /* read hostname */ hostname = gnutls_session_get_ptr (session); /* This verification function uses the trusted CAs in the credentials * structure. So you must have installed one or more CA certificates. */ ret = gnutls_certificate_verify_peers2 (session, &status); if (ret < 0) { printf ("Error\n"); return GNUTLS_E_CERTIFICATE_ERROR; } if (status & GNUTLS_CERT_INVALID) printf ("The certificate is not trusted.\n"); if (status & GNUTLS_CERT_SIGNER_NOT_FOUND) printf ("The certificate hasn't got a known issuer.\n"); if (status & GNUTLS_CERT_REVOKED) printf ("The certificate has been revoked.\n"); if (status & GNUTLS_CERT_EXPIRED) printf ("The certificate has expired\n"); if (status & GNUTLS_CERT_NOT_ACTIVATED) printf ("The certificate is not yet activated\n"); /* Up to here the process is the same for X.509 certificates and * OpenPGP keys. From now on X.509 certificates are assumed. This can * be easily extended to work with openpgp keys as well. */ if (gnutls_certificate_type_get (session) != GNUTLS_CRT_X509) return GNUTLS_E_CERTIFICATE_ERROR; if (gnutls_x509_crt_init (&cert) < 0) { printf ("error in initialization\n"); return GNUTLS_E_CERTIFICATE_ERROR; } cert_list = gnutls_certificate_get_peers (session, &cert_list_size); if (cert_list == NULL) { printf ("No certificate was found!\n"); return GNUTLS_E_CERTIFICATE_ERROR; } /* This is not a real world example, since we only check the first * certificate in the given chain. */ if (gnutls_x509_crt_import (cert, &cert_list[0], GNUTLS_X509_FMT_DER) < 0) { printf ("error parsing certificate\n"); return GNUTLS_E_CERTIFICATE_ERROR; } if (!gnutls_x509_crt_check_hostname (cert, hostname)) { printf ("The certificate's owner does not match hostname '%s'\n", hostname); return GNUTLS_E_CERTIFICATE_ERROR; } gnutls_x509_crt_deinit (cert); /* notify gnutls to continue handshake normally */ return 0; } int main (void) { int ret, sd, ii; gnutls_session_t session; char buffer[MAX_BUF + 1]; const char *err; gnutls_certificate_credentials_t xcred; gnutls_global_init (); /* X509 stuff */ gnutls_certificate_allocate_credentials (&xcred); /* sets the trusted cas file */ gnutls_certificate_set_x509_trust_file (xcred, CAFILE, GNUTLS_X509_FMT_PEM); gnutls_certificate_set_verify_function (xcred, verify_certificate_callback); gnutls_certificate_set_verify_flags (xcred, GNUTLS_VERIFY_ALLOW_X509_V1_CA_CRT); /* Initialize TLS session */ gnutls_init (&session, GNUTLS_CLIENT); gnutls_session_set_ptr (session, (void *) "my_host_name"); /* Use default priorities */ ret = gnutls_priority_set_direct (session, "PERFORMANCE", &err); if (ret < 0) { if (ret == GNUTLS_E_INVALID_REQUEST) { fprintf (stderr, "Syntax error at: %s\n", err); } exit (1); } /* put the x509 credentials to the current session */ gnutls_credentials_set (session, GNUTLS_CRD_CERTIFICATE, xcred); /* connect to the peer */ sd = tcp_connect (); gnutls_transport_set_ptr (session, (gnutls_transport_ptr_t) sd); /* Perform the TLS handshake */ ret = gnutls_handshake (session); if (ret < 0) { fprintf (stderr, "*** Handshake failed\n"); gnutls_perror (ret); goto end; } else { printf ("- Handshake was completed\n"); } gnutls_record_send (session, MSG, strlen (MSG)); ret = gnutls_record_recv (session, buffer, MAX_BUF); if (ret == 0) { printf ("- Peer has closed the TLS connection\n"); goto end; } else if (ret < 0) { fprintf (stderr, "*** Error: %s\n", gnutls_strerror (ret)); goto end; } printf ("- Received %d bytes: ", ret); for (ii = 0; ii < ret; ii++) { fputc (buffer[ii], stdout); } fputs ("\n", stdout); gnutls_bye (session, GNUTLS_SHUT_RDWR); end: tcp_close (sd); gnutls_deinit (session); gnutls_certificate_free_credentials (xcred); gnutls_global_deinit (); return 0; } Another example is listed below which provides more detailed verification output, for applications that need it. /* This example code is placed in the public domain. */ #ifdef HAVE_CONFIG_H #include #endif #include #include #include #include #include "examples.h" /* All the available CRLs */ gnutls_x509_crl_t *crl_list; int crl_list_size; /* All the available trusted CAs */ gnutls_x509_crt_t *ca_list; int ca_list_size; static void verify_cert2 (gnutls_x509_crt_t crt, gnutls_x509_crt_t issuer, gnutls_x509_crl_t * crl_list, int crl_list_size); static void verify_last_cert (gnutls_x509_crt_t crt, gnutls_x509_crt_t * ca_list, int ca_list_size, gnutls_x509_crl_t * crl_list, int crl_list_size); /* This function will try to verify the peer's certificate chain, and * also check if the hostname matches, and the activation, expiration dates. */ void verify_certificate_chain (gnutls_session_t session, const char *hostname, const gnutls_datum_t * cert_chain, int cert_chain_length) { int i; gnutls_x509_crt_t *cert; cert = malloc (sizeof (*cert) * cert_chain_length); /* Import all the certificates in the chain to * native certificate format. */ for (i = 0; i < cert_chain_length; i++) { gnutls_x509_crt_init (&cert[i]); gnutls_x509_crt_import (cert[i], &cert_chain[i], GNUTLS_X509_FMT_DER); } /* If the last certificate in the chain is self signed ignore it. * That is because we want to check against our trusted certificate * list. */ if (gnutls_x509_crt_check_issuer (cert[cert_chain_length - 1], cert[cert_chain_length - 1]) > 0 && cert_chain_length > 0) { cert_chain_length--; } /* Now verify the certificates against their issuers * in the chain. */ for (i = 1; i < cert_chain_length; i++) { verify_cert2 (cert[i - 1], cert[i], crl_list, crl_list_size); } /* Here we must verify the last certificate in the chain against * our trusted CA list. */ verify_last_cert (cert[cert_chain_length - 1], ca_list, ca_list_size, crl_list, crl_list_size); /* Check if the name in the first certificate matches our destination! */ if (!gnutls_x509_crt_check_hostname (cert[0], hostname)) { printf ("The certificate's owner does not match hostname '%s'\n", hostname); } for (i = 0; i < cert_chain_length; i++) gnutls_x509_crt_deinit (cert[i]); return; } /* Verifies a certificate against an other certificate * which is supposed to be it's issuer. Also checks the * crl_list if the certificate is revoked. */ static void verify_cert2 (gnutls_x509_crt_t crt, gnutls_x509_crt_t issuer, gnutls_x509_crl_t * crl_list, int crl_list_size) { unsigned int output; int ret; size_t name_size; char name[64]; /* Print information about the certificates to * be checked. */ name_size = sizeof (name); gnutls_x509_crt_get_dn (crt, name, &name_size); fprintf (stderr, "\nCertificate: %s\n", name); name_size = sizeof (name); gnutls_x509_crt_get_issuer_dn (crt, name, &name_size); fprintf (stderr, "Issued by: %s\n", name); /* Get the DN of the issuer cert. */ name_size = sizeof (name); gnutls_x509_crt_get_dn (issuer, name, &name_size); fprintf (stderr, "Checking against: %s\n", name); /* Do the actual verification. */ gnutls_x509_crt_verify (crt, &issuer, 1, 0, &output); if (output & GNUTLS_CERT_INVALID) { fprintf (stderr, "Not trusted"); if (output & GNUTLS_CERT_SIGNER_NOT_FOUND) fprintf (stderr, ": no issuer was found"); if (output & GNUTLS_CERT_SIGNER_NOT_CA) fprintf (stderr, ": issuer is not a CA"); if (output & GNUTLS_CERT_NOT_ACTIVATED) fprintf (stderr, ": not yet activated\n"); if (output & GNUTLS_CERT_EXPIRED) fprintf (stderr, ": expired\n"); fprintf (stderr, "\n"); } else fprintf (stderr, "Trusted\n"); /* Check if the certificate is revoked. */ ret = gnutls_x509_crt_check_revocation (crt, crl_list, crl_list_size); if (ret == 1) { /* revoked */ fprintf (stderr, "Revoked\n"); } } /* Verifies a certificate against our trusted CA list. * Also checks the crl_list if the certificate is revoked. */ static void verify_last_cert (gnutls_x509_crt_t crt, gnutls_x509_crt_t * ca_list, int ca_list_size, gnutls_x509_crl_t * crl_list, int crl_list_size) { unsigned int output; int ret; size_t name_size; char name[64]; /* Print information about the certificates to * be checked. */ name_size = sizeof (name); gnutls_x509_crt_get_dn (crt, name, &name_size); fprintf (stderr, "\nCertificate: %s\n", name); name_size = sizeof (name); gnutls_x509_crt_get_issuer_dn (crt, name, &name_size); fprintf (stderr, "Issued by: %s\n", name); /* Do the actual verification. */ gnutls_x509_crt_verify (crt, ca_list, ca_list_size, GNUTLS_VERIFY_ALLOW_X509_V1_CA_CRT, &output); if (output & GNUTLS_CERT_INVALID) { fprintf (stderr, "Not trusted"); if (output & GNUTLS_CERT_SIGNER_NOT_CA) fprintf (stderr, ": Issuer is not a CA\n"); if (output & GNUTLS_CERT_NOT_ACTIVATED) fprintf (stderr, ": Not yet activated\n"); if (output & GNUTLS_CERT_EXPIRED) fprintf (stderr, ": Expired\n"); fprintf (stderr, "\n"); } else fprintf (stderr, "Trusted\n"); /* Check if the certificate is revoked. */ ret = gnutls_x509_crt_check_revocation (crt, crl_list, crl_list_size); if (ret == 1) { /* revoked */ fprintf (stderr, "Revoked\n"); } }  File: gnutls.info, Node: Using a callback to select the certificate to use, Next: Client using a PKCS #11 token with TLS, Prev: Verifying peer's certificate, Up: Client examples 7.3.5 Using a Callback to Select the Certificate to Use ------------------------------------------------------- There are cases where a client holds several certificate and key pairs, and may not want to load all of them in the credentials structure. The following example demonstrates the use of the certificate selection callback. /* This example code is placed in the public domain. */ #ifdef HAVE_CONFIG_H #include #endif #include #include #include #include #include #include #include #include #include #include #include #include /* A TLS client that loads the certificate and key. */ #define MAX_BUF 1024 #define MSG "GET / HTTP/1.0\r\n\r\n" #define CERT_FILE "cert.pem" #define KEY_FILE "key.pem" #define CAFILE "ca.pem" extern int tcp_connect (void); extern void tcp_close (int sd); static int cert_callback (gnutls_session_t session, const gnutls_datum_t * req_ca_rdn, int nreqs, const gnutls_pk_algorithm_t * sign_algos, int sign_algos_length, gnutls_retr2_st * st); gnutls_x509_crt_t crt; gnutls_x509_privkey_t key; /* Helper functions to load a certificate and key * files into memory. */ static gnutls_datum_t load_file (const char *file) { FILE *f; gnutls_datum_t loaded_file = { NULL, 0 }; long filelen; void *ptr; if (!(f = fopen (file, "r")) || fseek (f, 0, SEEK_END) != 0 || (filelen = ftell (f)) < 0 || fseek (f, 0, SEEK_SET) != 0 || !(ptr = malloc ((size_t) filelen)) || fread (ptr, 1, (size_t) filelen, f) < (size_t) filelen) { return loaded_file; } loaded_file.data = ptr; loaded_file.size = (unsigned int) filelen; return loaded_file; } static void unload_file (gnutls_datum_t data) { free (data.data); } /* Load the certificate and the private key. */ static void load_keys (void) { int ret; gnutls_datum_t data; data = load_file (CERT_FILE); if (data.data == NULL) { fprintf (stderr, "*** Error loading cert file.\n"); exit (1); } gnutls_x509_crt_init (&crt); ret = gnutls_x509_crt_import (crt, &data, GNUTLS_X509_FMT_PEM); if (ret < 0) { fprintf (stderr, "*** Error loading key file: %s\n", gnutls_strerror (ret)); exit (1); } unload_file (data); data = load_file (KEY_FILE); if (data.data == NULL) { fprintf (stderr, "*** Error loading key file.\n"); exit (1); } gnutls_x509_privkey_init (&key); ret = gnutls_x509_privkey_import (key, &data, GNUTLS_X509_FMT_PEM); if (ret < 0) { fprintf (stderr, "*** Error loading key file: %s\n", gnutls_strerror (ret)); exit (1); } unload_file (data); } int main (void) { int ret, sd, ii; gnutls_session_t session; gnutls_priority_t priorities_cache; char buffer[MAX_BUF + 1]; gnutls_certificate_credentials_t xcred; /* Allow connections to servers that have OpenPGP keys as well. */ gnutls_global_init (); load_keys (); /* X509 stuff */ gnutls_certificate_allocate_credentials (&xcred); /* priorities */ gnutls_priority_init (&priorities_cache, "NORMAL", NULL); /* sets the trusted cas file */ gnutls_certificate_set_x509_trust_file (xcred, CAFILE, GNUTLS_X509_FMT_PEM); gnutls_certificate_set_retrieve_function (xcred, cert_callback); /* Initialize TLS session */ gnutls_init (&session, GNUTLS_CLIENT); /* Use default priorities */ gnutls_priority_set (session, priorities_cache); /* put the x509 credentials to the current session */ gnutls_credentials_set (session, GNUTLS_CRD_CERTIFICATE, xcred); /* connect to the peer */ sd = tcp_connect (); gnutls_transport_set_ptr (session, (gnutls_transport_ptr_t) sd); /* Perform the TLS handshake */ ret = gnutls_handshake (session); if (ret < 0) { fprintf (stderr, "*** Handshake failed\n"); gnutls_perror (ret); goto end; } else { printf ("- Handshake was completed\n"); } gnutls_record_send (session, MSG, strlen (MSG)); ret = gnutls_record_recv (session, buffer, MAX_BUF); if (ret == 0) { printf ("- Peer has closed the TLS connection\n"); goto end; } else if (ret < 0) { fprintf (stderr, "*** Error: %s\n", gnutls_strerror (ret)); goto end; } printf ("- Received %d bytes: ", ret); for (ii = 0; ii < ret; ii++) { fputc (buffer[ii], stdout); } fputs ("\n", stdout); gnutls_bye (session, GNUTLS_SHUT_RDWR); end: tcp_close (sd); gnutls_deinit (session); gnutls_certificate_free_credentials (xcred); gnutls_priority_deinit (priorities_cache); gnutls_global_deinit (); return 0; } /* This callback should be associated with a session by calling * gnutls_certificate_client_set_retrieve_function( session, cert_callback), * before a handshake. */ static int cert_callback (gnutls_session_t session, const gnutls_datum_t * req_ca_rdn, int nreqs, const gnutls_pk_algorithm_t * sign_algos, int sign_algos_length, gnutls_retr2_st * st) { char issuer_dn[256]; int i, ret; size_t len; gnutls_certificate_type_t type; /* Print the server's trusted CAs */ if (nreqs > 0) printf ("- Server's trusted authorities:\n"); else printf ("- Server did not send us any trusted authorities names.\n"); /* print the names (if any) */ for (i = 0; i < nreqs; i++) { len = sizeof (issuer_dn); ret = gnutls_x509_rdn_get (&req_ca_rdn[i], issuer_dn, &len); if (ret >= 0) { printf (" [%d]: ", i); printf ("%s\n", issuer_dn); } } /* Select a certificate and return it. * The certificate must be of any of the "sign algorithms" * supported by the server. */ type = gnutls_certificate_type_get (session); if (type == GNUTLS_CRT_X509) { /* check if the certificate we are sending is signed * with an algorithm that the server accepts */ gnutls_sign_algorithm_t cert_algo, req_algo; int i, match = 0; ret = gnutls_x509_crt_get_signature_algorithm (crt); if (ret < 0) { /* error reading signature algorithm */ return -1; } cert_algo = ret; i = 0; do { ret = gnutls_sign_algorithm_get_requested (session, i, &req_algo); if (ret >= 0 && cert_algo == req_algo) { match = 1; break; } /* server has not requested anything specific */ if (i == 0 && ret == GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE) { match = 1; break; } i++; } while (ret >= 0); if (match == 0) { printf ("- Could not find a suitable certificate to send to server\n"); return -1; } st->cert_type = type; st->ncerts = 1; st->cert.x509 = &crt; st->key.x509 = key; st->key_type = GNUTLS_PRIVKEY_X509; st->deinit_all = 0; } else { return -1; } return 0; }  File: gnutls.info, Node: Client using a PKCS #11 token with TLS, Next: Client with Resume capability example, Prev: Using a callback to select the certificate to use, Up: Client examples 7.3.6 Using a PKCS #11 token with TLS ------------------------------------- This example will demonstrate how to load keys and certificates from a PKCS #11 token, and use it with a TLS connection. /* This example code is placed in the public domain. */ #ifdef HAVE_CONFIG_H #include #endif #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* A TLS client that loads the certificate and key. */ #define MAX_BUF 1024 #define MSG "GET / HTTP/1.0\r\n\r\n" #define MIN(x,y) (((x)<(y))?(x):(y)) #define CAFILE "ca.pem" #define KEY_URL "pkcs11:manufacturer=SomeManufacturer;object=Private%20Key" \ ";objecttype=private;id=db:5b:3e:b5:72:33" #define CERT_URL "pkcs11:manufacturer=SomeManufacturer;object=Certificate;" \ "objecttype=cert;id=db:5b:3e:b5:72:33" extern int tcp_connect (void); extern void tcp_close (int sd); static int cert_callback (gnutls_session_t session, const gnutls_datum_t * req_ca_rdn, int nreqs, const gnutls_pk_algorithm_t * sign_algos, int sign_algos_length, gnutls_retr2_st * st); gnutls_x509_crt_t crt; gnutls_pkcs11_privkey_t key; /* Load the certificate and the private key. */ static void load_keys (void) { int ret; gnutls_x509_crt_init (&crt); ret = gnutls_x509_crt_import_pkcs11_url (crt, CERT_URL, 0); /* some tokens require login to read data */ if (ret == GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE) ret = gnutls_x509_crt_import_pkcs11_url (crt, CERT_URL, GNUTLS_PKCS11_OBJ_FLAG_LOGIN); if (ret < 0) { fprintf (stderr, "*** Error loading key file: %s\n", gnutls_strerror (ret)); exit (1); } gnutls_pkcs11_privkey_init (&key); ret = gnutls_pkcs11_privkey_import_url (key, KEY_URL, 0); if (ret < 0) { fprintf (stderr, "*** Error loading key file: %s\n", gnutls_strerror (ret)); exit (1); } } static int pin_callback (void *user, int attempt, const char *token_url, const char *token_label, unsigned int flags, char *pin, size_t pin_max) { const char *password; int len; printf ("PIN required for token '%s' with URL '%s'\n", token_label, token_url); if (flags & GNUTLS_PKCS11_PIN_FINAL_TRY) printf ("*** This is the final try before locking!\n"); if (flags & GNUTLS_PKCS11_PIN_COUNT_LOW) printf ("*** Only few tries left before locking!\n"); password = getpass ("Enter pin: "); if (password == NULL || password[0] == 0) { fprintf (stderr, "No password given\n"); exit (1); } len = MIN (pin_max, strlen (password)); memcpy (pin, password, len); pin[len] = 0; return 0; } int main (void) { int ret, sd, ii; gnutls_session_t session; gnutls_priority_t priorities_cache; char buffer[MAX_BUF + 1]; gnutls_certificate_credentials_t xcred; /* Allow connections to servers that have OpenPGP keys as well. */ gnutls_global_init (); /* PKCS11 private key operations might require PIN. * Register a callback. */ gnutls_pkcs11_set_pin_function (pin_callback, NULL); load_keys (); /* X509 stuff */ gnutls_certificate_allocate_credentials (&xcred); /* priorities */ gnutls_priority_init (&priorities_cache, "NORMAL", NULL); /* sets the trusted cas file */ gnutls_certificate_set_x509_trust_file (xcred, CAFILE, GNUTLS_X509_FMT_PEM); gnutls_certificate_set_retrieve_function (xcred, cert_callback); /* Initialize TLS session */ gnutls_init (&session, GNUTLS_CLIENT); /* Use default priorities */ gnutls_priority_set (session, priorities_cache); /* put the x509 credentials to the current session */ gnutls_credentials_set (session, GNUTLS_CRD_CERTIFICATE, xcred); /* connect to the peer */ sd = tcp_connect (); gnutls_transport_set_ptr (session, (gnutls_transport_ptr_t) sd); /* Perform the TLS handshake */ ret = gnutls_handshake (session); if (ret < 0) { fprintf (stderr, "*** Handshake failed\n"); gnutls_perror (ret); goto end; } else { printf ("- Handshake was completed\n"); } gnutls_record_send (session, MSG, strlen (MSG)); ret = gnutls_record_recv (session, buffer, MAX_BUF); if (ret == 0) { printf ("- Peer has closed the TLS connection\n"); goto end; } else if (ret < 0) { fprintf (stderr, "*** Error: %s\n", gnutls_strerror (ret)); goto end; } printf ("- Received %d bytes: ", ret); for (ii = 0; ii < ret; ii++) { fputc (buffer[ii], stdout); } fputs ("\n", stdout); gnutls_bye (session, GNUTLS_SHUT_RDWR); end: tcp_close (sd); gnutls_deinit (session); gnutls_certificate_free_credentials (xcred); gnutls_priority_deinit (priorities_cache); gnutls_global_deinit (); return 0; } /* This callback should be associated with a session by calling * gnutls_certificate_client_set_retrieve_function( session, cert_callback), * before a handshake. */ static int cert_callback (gnutls_session_t session, const gnutls_datum_t * req_ca_rdn, int nreqs, const gnutls_pk_algorithm_t * sign_algos, int sign_algos_length, gnutls_retr2_st * st) { char issuer_dn[256]; int i, ret; size_t len; gnutls_certificate_type_t type; /* Print the server's trusted CAs */ if (nreqs > 0) printf ("- Server's trusted authorities:\n"); else printf ("- Server did not send us any trusted authorities names.\n"); /* print the names (if any) */ for (i = 0; i < nreqs; i++) { len = sizeof (issuer_dn); ret = gnutls_x509_rdn_get (&req_ca_rdn[i], issuer_dn, &len); if (ret >= 0) { printf (" [%d]: ", i); printf ("%s\n", issuer_dn); } } /* Select a certificate and return it. * The certificate must be of any of the "sign algorithms" * supported by the server. */ type = gnutls_certificate_type_get (session); if (type == GNUTLS_CRT_X509) { /* check if the certificate we are sending is signed * with an algorithm that the server accepts */ gnutls_sign_algorithm_t cert_algo, req_algo; int i, match = 0; ret = gnutls_x509_crt_get_signature_algorithm (crt); if (ret < 0) { /* error reading signature algorithm */ return -1; } cert_algo = ret; i = 0; do { ret = gnutls_sign_algorithm_get_requested (session, i, &req_algo); if (ret >= 0 && cert_algo == req_algo) { match = 1; break; } /* server has not requested anything specific */ if (i == 0 && ret == GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE) { match = 1; break; } i++; } while (ret >= 0); if (match == 0) { printf ("- Could not find a suitable certificate to send to server\n"); return -1; } st->cert_type = type; st->ncerts = 1; st->cert.x509 = &crt; st->key.pkcs11 = key; st->key_type = GNUTLS_PRIVKEY_PKCS11; st->deinit_all = 0; } else { return -1; } return 0; }  File: gnutls.info, Node: Client with Resume capability example, Next: Simple client example with SRP authentication, Prev: Client using a PKCS #11 token with TLS, Up: Client examples 7.3.7 Client with Resume Capability Example ------------------------------------------- This is a modification of the simple client example. Here we demonstrate the use of session resumption. The client tries to connect once using TLS, close the connection and then try to establish a new connection using the previously negotiated data. /* This example code is placed in the public domain. */ #ifdef HAVE_CONFIG_H #include #endif #include #include #include #include /* Those functions are defined in other examples. */ extern void check_alert (gnutls_session_t session, int ret); extern int tcp_connect (void); extern void tcp_close (int sd); #define MAX_BUF 1024 #define CAFILE "ca.pem" #define MSG "GET / HTTP/1.0\r\n\r\n" int main (void) { int ret; int sd, ii; gnutls_session_t session; char buffer[MAX_BUF + 1]; gnutls_certificate_credentials_t xcred; /* variables used in session resuming */ int t; char *session_data = NULL; size_t session_data_size = 0; gnutls_global_init (); /* X509 stuff */ gnutls_certificate_allocate_credentials (&xcred); gnutls_certificate_set_x509_trust_file (xcred, CAFILE, GNUTLS_X509_FMT_PEM); for (t = 0; t < 2; t++) { /* connect 2 times to the server */ sd = tcp_connect (); gnutls_init (&session, GNUTLS_CLIENT); gnutls_priority_set_direct (session, "PERFORMANCE:!ARCFOUR-128", NULL); gnutls_credentials_set (session, GNUTLS_CRD_CERTIFICATE, xcred); if (t > 0) { /* if this is not the first time we connect */ gnutls_session_set_data (session, session_data, session_data_size); free (session_data); } gnutls_transport_set_ptr (session, (gnutls_transport_ptr_t) sd); /* Perform the TLS handshake */ ret = gnutls_handshake (session); if (ret < 0) { fprintf (stderr, "*** Handshake failed\n"); gnutls_perror (ret); goto end; } else { printf ("- Handshake was completed\n"); } if (t == 0) { /* the first time we connect */ /* get the session data size */ gnutls_session_get_data (session, NULL, &session_data_size); session_data = malloc (session_data_size); /* put session data to the session variable */ gnutls_session_get_data (session, session_data, &session_data_size); } else { /* the second time we connect */ /* check if we actually resumed the previous session */ if (gnutls_session_is_resumed (session) != 0) { printf ("- Previous session was resumed\n"); } else { fprintf (stderr, "*** Previous session was NOT resumed\n"); } } /* This function was defined in a previous example */ /* print_info(session); */ gnutls_record_send (session, MSG, strlen (MSG)); ret = gnutls_record_recv (session, buffer, MAX_BUF); if (ret == 0) { printf ("- Peer has closed the TLS connection\n"); goto end; } else if (ret < 0) { fprintf (stderr, "*** Error: %s\n", gnutls_strerror (ret)); goto end; } printf ("- Received %d bytes: ", ret); for (ii = 0; ii < ret; ii++) { fputc (buffer[ii], stdout); } fputs ("\n", stdout); gnutls_bye (session, GNUTLS_SHUT_RDWR); end: tcp_close (sd); gnutls_deinit (session); } /* for() */ gnutls_certificate_free_credentials (xcred); gnutls_global_deinit (); return 0; }  File: gnutls.info, Node: Simple client example with SRP authentication, Next: Simple client example in C++, Prev: Client with Resume capability example, Up: Client examples 7.3.8 Simple Client Example with SRP Authentication --------------------------------------------------- The following client is a very simple SRP TLS client which connects to a server and authenticates using a _username_ and a _password_. The server may authenticate itself using a certificate, and in that case it has to be verified. /* This example code is placed in the public domain. */ #ifdef HAVE_CONFIG_H #include #endif #include #include #include #include #include /* Those functions are defined in other examples. */ extern void check_alert (gnutls_session_t session, int ret); extern int tcp_connect (void); extern void tcp_close (int sd); #define MAX_BUF 1024 #define USERNAME "user" #define PASSWORD "pass" #define CAFILE "ca.pem" #define MSG "GET / HTTP/1.0\r\n\r\n" int main (void) { int ret; int sd, ii; gnutls_session_t session; char buffer[MAX_BUF + 1]; gnutls_srp_client_credentials_t srp_cred; gnutls_certificate_credentials_t cert_cred; gnutls_global_init (); /* now enable the gnutls-extra library which contains the * SRP stuff. */ gnutls_global_init_extra (); gnutls_srp_allocate_client_credentials (&srp_cred); gnutls_certificate_allocate_credentials (&cert_cred); gnutls_certificate_set_x509_trust_file (cert_cred, CAFILE, GNUTLS_X509_FMT_PEM); gnutls_srp_set_client_credentials (srp_cred, USERNAME, PASSWORD); /* connects to server */ sd = tcp_connect (); /* Initialize TLS session */ gnutls_init (&session, GNUTLS_CLIENT); /* Set the priorities. */ gnutls_priority_set_direct (session, "NORMAL:+SRP:+SRP-RSA:+SRP-DSS", NULL); /* put the SRP credentials to the current session */ gnutls_credentials_set (session, GNUTLS_CRD_SRP, srp_cred); gnutls_credentials_set (session, GNUTLS_CRD_CERTIFICATE, cert_cred); gnutls_transport_set_ptr (session, (gnutls_transport_ptr_t) sd); /* Perform the TLS handshake */ ret = gnutls_handshake (session); if (ret < 0) { fprintf (stderr, "*** Handshake failed\n"); gnutls_perror (ret); goto end; } else { printf ("- Handshake was completed\n"); } gnutls_record_send (session, MSG, strlen (MSG)); ret = gnutls_record_recv (session, buffer, MAX_BUF); if (gnutls_error_is_fatal (ret) == 1 || ret == 0) { if (ret == 0) { printf ("- Peer has closed the GnuTLS connection\n"); goto end; } else { fprintf (stderr, "*** Error: %s\n", gnutls_strerror (ret)); goto end; } } else check_alert (session, ret); if (ret > 0) { printf ("- Received %d bytes: ", ret); for (ii = 0; ii < ret; ii++) { fputc (buffer[ii], stdout); } fputs ("\n", stdout); } gnutls_bye (session, GNUTLS_SHUT_RDWR); end: tcp_close (sd); gnutls_deinit (session); gnutls_srp_free_client_credentials (srp_cred); gnutls_certificate_free_credentials (cert_cred); gnutls_global_deinit (); return 0; }  File: gnutls.info, Node: Simple client example in C++, Next: Helper function for TCP connections, Prev: Simple client example with SRP authentication, Up: Client examples 7.3.9 Simple Client Example using the C++ API --------------------------------------------- The following client is a simple example of a client client utilizing the GnuTLS C++ API. #include #include #include #include #include /* for strlen */ /* A very basic TLS client, with anonymous authentication. * written by Eduardo Villanueva Che. */ #define MAX_BUF 1024 #define SA struct sockaddr #define CAFILE "ca.pem" #define MSG "GET / HTTP/1.0\r\n\r\n" extern "C" { int tcp_connect(void); void tcp_close(int sd); } int main(void) { int sd = -1; gnutls_global_init(); try { /* Allow connections to servers that have OpenPGP keys as well. */ gnutls::client_session session; /* X509 stuff */ gnutls::certificate_credentials credentials; /* sets the trusted cas file */ credentials.set_x509_trust_file(CAFILE, GNUTLS_X509_FMT_PEM); /* put the x509 credentials to the current session */ session.set_credentials(credentials); /* Use default priorities */ session.set_priority ("NORMAL", NULL); /* connect to the peer */ sd = tcp_connect(); session.set_transport_ptr((gnutls_transport_ptr_t) sd); /* Perform the TLS handshake */ int ret = session.handshake(); if (ret < 0) { throw std::runtime_error("Handshake failed"); } else { std::cout << "- Handshake was completed" << std::endl; } session.send(MSG, strlen(MSG)); char buffer[MAX_BUF + 1]; ret = session.recv(buffer, MAX_BUF); if (ret == 0) { throw std::runtime_error("Peer has closed the TLS connection"); } else if (ret < 0) { throw std::runtime_error(gnutls_strerror(ret)); } std::cout << "- Received " << ret << " bytes:" << std::endl; std::cout.write(buffer, ret); std::cout << std::endl; session.bye(GNUTLS_SHUT_RDWR); } catch (std::exception &ex) { std::cerr << "Exception caught: " << ex.what() << std::endl; } if (sd != -1) tcp_close(sd); gnutls_global_deinit(); return 0; }  File: gnutls.info, Node: Helper function for TCP connections, Prev: Simple client example in C++, Up: Client examples 7.3.10 Helper Function for TCP Connections ------------------------------------------ This helper function abstracts away TCP connection handling from the other examples. It is required to build some examples. /* This example code is placed in the public domain. */ #ifdef HAVE_CONFIG_H #include #endif #include #include #include #include #include #include #include #include #define SA struct sockaddr /* tcp.c */ int tcp_connect (void); void tcp_close (int sd); /* Connects to the peer and returns a socket * descriptor. */ extern int tcp_connect (void) { const char *PORT = "5556"; const char *SERVER = "127.0.0.1"; int err, sd; struct sockaddr_in sa; /* connects to server */ sd = socket (AF_INET, SOCK_STREAM, 0); memset (&sa, '\0', sizeof (sa)); sa.sin_family = AF_INET; sa.sin_port = htons (atoi (PORT)); inet_pton (AF_INET, SERVER, &sa.sin_addr); err = connect (sd, (SA *) & sa, sizeof (sa)); if (err < 0) { fprintf (stderr, "Connect error\n"); exit (1); } return sd; } /* closes the given socket descriptor. */ extern void tcp_close (int sd) { shutdown (sd, SHUT_RDWR); /* no more receptions */ close (sd); }  File: gnutls.info, Node: Server examples, Next: Miscellaneous examples, Prev: Client examples, Up: How to use GnuTLS in applications 7.4 Server Examples =================== This section contains examples of TLS and SSL servers, using GnuTLS. * Menu: * Echo Server with X.509 authentication:: * Echo Server with OpenPGP authentication:: * Echo Server with SRP authentication:: * Echo Server with anonymous authentication::  File: gnutls.info, Node: Echo Server with X.509 authentication, Next: Echo Server with OpenPGP authentication, Up: Server examples 7.4.1 Echo Server with X.509 Authentication ------------------------------------------- This example is a very simple echo server which supports X.509 authentication, using the RSA ciphersuites. /* This example code is placed in the public domain. */ #ifdef HAVE_CONFIG_H #include #endif #include #include #include #include #include #include #include #include #include #include #define KEYFILE "key.pem" #define CERTFILE "cert.pem" #define CAFILE "ca.pem" #define CRLFILE "crl.pem" /* This is a sample TLS 1.0 echo server, using X.509 authentication. */ #define SA struct sockaddr #define SOCKET_ERR(err,s) if(err==-1) {perror(s);return(1);} #define MAX_BUF 1024 #define PORT 5556 /* listen to 5556 port */ #define DH_BITS 1024 /* These are global */ gnutls_certificate_credentials_t x509_cred; gnutls_priority_t priority_cache; static gnutls_session_t initialize_tls_session (void) { gnutls_session_t session; gnutls_init (&session, GNUTLS_SERVER); gnutls_priority_set (session, priority_cache); gnutls_credentials_set (session, GNUTLS_CRD_CERTIFICATE, x509_cred); /* request client certificate if any. */ gnutls_certificate_server_set_request (session, GNUTLS_CERT_REQUEST); /* Set maximum compatibility mode. This is only suggested on public webservers * that need to trade security for compatibility */ gnutls_session_enable_compatibility_mode (session); return session; } static gnutls_dh_params_t dh_params; static int generate_dh_params (void) { /* Generate Diffie-Hellman parameters - for use with DHE * kx algorithms. When short bit length is used, it might * be wise to regenerate parameters. * * Check the ex-serv-export.c example for using static * parameters. */ gnutls_dh_params_init (&dh_params); gnutls_dh_params_generate2 (dh_params, DH_BITS); return 0; } int main (void) { int err, listen_sd; int sd, ret; struct sockaddr_in sa_serv; struct sockaddr_in sa_cli; int client_len; char topbuf[512]; gnutls_session_t session; char buffer[MAX_BUF + 1]; int optval = 1; /* this must be called once in the program */ gnutls_global_init (); gnutls_certificate_allocate_credentials (&x509_cred); gnutls_certificate_set_x509_trust_file (x509_cred, CAFILE, GNUTLS_X509_FMT_PEM); gnutls_certificate_set_x509_crl_file (x509_cred, CRLFILE, GNUTLS_X509_FMT_PEM); gnutls_certificate_set_x509_key_file (x509_cred, CERTFILE, KEYFILE, GNUTLS_X509_FMT_PEM); generate_dh_params (); gnutls_priority_init (&priority_cache, "NORMAL", NULL); gnutls_certificate_set_dh_params (x509_cred, dh_params); /* Socket operations */ listen_sd = socket (AF_INET, SOCK_STREAM, 0); SOCKET_ERR (listen_sd, "socket"); memset (&sa_serv, '\0', sizeof (sa_serv)); sa_serv.sin_family = AF_INET; sa_serv.sin_addr.s_addr = INADDR_ANY; sa_serv.sin_port = htons (PORT); /* Server Port number */ setsockopt (listen_sd, SOL_SOCKET, SO_REUSEADDR, (void *) &optval, sizeof (int)); err = bind (listen_sd, (SA *) & sa_serv, sizeof (sa_serv)); SOCKET_ERR (err, "bind"); err = listen (listen_sd, 1024); SOCKET_ERR (err, "listen"); printf ("Server ready. Listening to port '%d'.\n\n", PORT); client_len = sizeof (sa_cli); for (;;) { session = initialize_tls_session (); sd = accept (listen_sd, (SA *) & sa_cli, &client_len); printf ("- connection from %s, port %d\n", inet_ntop (AF_INET, &sa_cli.sin_addr, topbuf, sizeof (topbuf)), ntohs (sa_cli.sin_port)); gnutls_transport_set_ptr (session, (gnutls_transport_ptr_t) sd); ret = gnutls_handshake (session); if (ret < 0) { close (sd); gnutls_deinit (session); fprintf (stderr, "*** Handshake has failed (%s)\n\n", gnutls_strerror (ret)); continue; } printf ("- Handshake was completed\n"); /* see the Getting peer's information example */ /* print_info(session); */ for (;;) { memset (buffer, 0, MAX_BUF + 1); ret = gnutls_record_recv (session, buffer, MAX_BUF); if (ret == 0) { printf ("\n- Peer has closed the GnuTLS connection\n"); break; } else if (ret < 0) { fprintf (stderr, "\n*** Received corrupted " "data(%d). Closing the connection.\n\n", ret); break; } else if (ret > 0) { /* echo data back to the client */ gnutls_record_send (session, buffer, strlen (buffer)); } } printf ("\n"); /* do not wait for the peer to close the connection. */ gnutls_bye (session, GNUTLS_SHUT_WR); close (sd); gnutls_deinit (session); } close (listen_sd); gnutls_certificate_free_credentials (x509_cred); gnutls_priority_deinit (priority_cache); gnutls_global_deinit (); return 0; }  File: gnutls.info, Node: Echo Server with OpenPGP authentication, Next: Echo Server with SRP authentication, Prev: Echo Server with X.509 authentication, Up: Server examples 7.4.2 Echo Server with OpenPGP Authentication --------------------------------------------- The following example is an echo server which supports OpenPGP key authentication. You can easily combine this functionality --that is have a server that supports both X.509 and OpenPGP certificates-- but we separated them to keep these examples as simple as possible. /* This example code is placed in the public domain. */ #ifdef HAVE_CONFIG_H #include #endif #include #include #include #include #include #include #include #include #include #include #include #define KEYFILE "secret.asc" #define CERTFILE "public.asc" #define RINGFILE "ring.gpg" /* This is a sample TLS 1.0-OpenPGP echo server. */ #define SA struct sockaddr #define SOCKET_ERR(err,s) if(err==-1) {perror(s);return(1);} #define MAX_BUF 1024 #define PORT 5556 /* listen to 5556 port */ #define DH_BITS 1024 /* These are global */ gnutls_certificate_credentials_t cred; gnutls_dh_params_t dh_params; static int generate_dh_params (void) { /* Generate Diffie-Hellman parameters - for use with DHE * kx algorithms. These should be discarded and regenerated * once a day, once a week or once a month. Depending on the * security requirements. */ gnutls_dh_params_init (&dh_params); gnutls_dh_params_generate2 (dh_params, DH_BITS); return 0; } static gnutls_session_t initialize_tls_session (void) { gnutls_session_t session; gnutls_init (&session, GNUTLS_SERVER); gnutls_priority_set_direct (session, "NORMAL", NULL); /* request client certificate if any. */ gnutls_certificate_server_set_request (session, GNUTLS_CERT_REQUEST); gnutls_dh_set_prime_bits (session, DH_BITS); return session; } int main (void) { int err, listen_sd; int sd, ret; struct sockaddr_in sa_serv; struct sockaddr_in sa_cli; int client_len; char topbuf[512]; gnutls_session_t session; char buffer[MAX_BUF + 1]; int optval = 1; char name[256]; strcpy (name, "Echo Server"); /* this must be called once in the program */ gnutls_global_init (); gnutls_certificate_allocate_credentials (&cred); gnutls_certificate_set_openpgp_keyring_file (cred, RINGFILE, GNUTLS_OPENPGP_FMT_BASE64); gnutls_certificate_set_openpgp_key_file (cred, CERTFILE, KEYFILE, GNUTLS_OPENPGP_FMT_BASE64); generate_dh_params (); gnutls_certificate_set_dh_params (cred, dh_params); /* Socket operations */ listen_sd = socket (AF_INET, SOCK_STREAM, 0); SOCKET_ERR (listen_sd, "socket"); memset (&sa_serv, '\0', sizeof (sa_serv)); sa_serv.sin_family = AF_INET; sa_serv.sin_addr.s_addr = INADDR_ANY; sa_serv.sin_port = htons (PORT); /* Server Port number */ setsockopt (listen_sd, SOL_SOCKET, SO_REUSEADDR, (void *) &optval, sizeof (int)); err = bind (listen_sd, (SA *) & sa_serv, sizeof (sa_serv)); SOCKET_ERR (err, "bind"); err = listen (listen_sd, 1024); SOCKET_ERR (err, "listen"); printf ("%s ready. Listening to port '%d'.\n\n", name, PORT); client_len = sizeof (sa_cli); for (;;) { session = initialize_tls_session (); sd = accept (listen_sd, (SA *) & sa_cli, &client_len); printf ("- connection from %s, port %d\n", inet_ntop (AF_INET, &sa_cli.sin_addr, topbuf, sizeof (topbuf)), ntohs (sa_cli.sin_port)); gnutls_transport_set_ptr (session, (gnutls_transport_ptr_t) sd); ret = gnutls_handshake (session); if (ret < 0) { close (sd); gnutls_deinit (session); fprintf (stderr, "*** Handshake has failed (%s)\n\n", gnutls_strerror (ret)); continue; } printf ("- Handshake was completed\n"); /* see the Getting peer's information example */ /* print_info(session); */ for (;;) { memset (buffer, 0, MAX_BUF + 1); ret = gnutls_record_recv (session, buffer, MAX_BUF); if (ret == 0) { printf ("\n- Peer has closed the GnuTLS connection\n"); break; } else if (ret < 0) { fprintf (stderr, "\n*** Received corrupted " "data(%d). Closing the connection.\n\n", ret); break; } else if (ret > 0) { /* echo data back to the client */ gnutls_record_send (session, buffer, strlen (buffer)); } } printf ("\n"); /* do not wait for the peer to close the connection. */ gnutls_bye (session, GNUTLS_SHUT_WR); close (sd); gnutls_deinit (session); } close (listen_sd); gnutls_certificate_free_credentials (cred); gnutls_global_deinit (); return 0; }  File: gnutls.info, Node: Echo Server with SRP authentication, Next: Echo Server with anonymous authentication, Prev: Echo Server with OpenPGP authentication, Up: Server examples 7.4.3 Echo Server with SRP Authentication ----------------------------------------- This is a server which supports SRP authentication. It is also possible to combine this functionality with a certificate server. Here it is separate for simplicity. /* This example code is placed in the public domain. */ #ifdef HAVE_CONFIG_H #include #endif #include #include #include #include #include #include #include #include #include #include #include #define SRP_PASSWD "tpasswd" #define SRP_PASSWD_CONF "tpasswd.conf" #define KEYFILE "key.pem" #define CERTFILE "cert.pem" #define CAFILE "ca.pem" /* This is a sample TLS-SRP echo server. */ #define SA struct sockaddr #define SOCKET_ERR(err,s) if(err==-1) {perror(s);return(1);} #define MAX_BUF 1024 #define PORT 5556 /* listen to 5556 port */ /* These are global */ gnutls_srp_server_credentials_t srp_cred; gnutls_certificate_credentials_t cert_cred; static gnutls_session_t initialize_tls_session (void) { gnutls_session_t session; gnutls_init (&session, GNUTLS_SERVER); gnutls_priority_set_direct (session, "NORMAL:+SRP:+SRP-DSS:+SRP-RSA", NULL); gnutls_credentials_set (session, GNUTLS_CRD_SRP, srp_cred); /* for the certificate authenticated ciphersuites. */ gnutls_credentials_set (session, GNUTLS_CRD_CERTIFICATE, cert_cred); /* request client certificate if any. */ gnutls_certificate_server_set_request (session, GNUTLS_CERT_IGNORE); return session; } int main (void) { int err, listen_sd; int sd, ret; struct sockaddr_in sa_serv; struct sockaddr_in sa_cli; int client_len; char topbuf[512]; gnutls_session_t session; char buffer[MAX_BUF + 1]; int optval = 1; char name[256]; strcpy (name, "Echo Server"); /* these must be called once in the program */ gnutls_global_init (); gnutls_global_init_extra (); /* for SRP */ /* SRP_PASSWD a password file (created with the included srptool utility) */ gnutls_srp_allocate_server_credentials (&srp_cred); gnutls_srp_set_server_credentials_file (srp_cred, SRP_PASSWD, SRP_PASSWD_CONF); gnutls_certificate_allocate_credentials (&cert_cred); gnutls_certificate_set_x509_trust_file (cert_cred, CAFILE, GNUTLS_X509_FMT_PEM); gnutls_certificate_set_x509_key_file (cert_cred, CERTFILE, KEYFILE, GNUTLS_X509_FMT_PEM); /* TCP socket operations */ listen_sd = socket (AF_INET, SOCK_STREAM, 0); SOCKET_ERR (listen_sd, "socket"); memset (&sa_serv, '\0', sizeof (sa_serv)); sa_serv.sin_family = AF_INET; sa_serv.sin_addr.s_addr = INADDR_ANY; sa_serv.sin_port = htons (PORT); /* Server Port number */ setsockopt (listen_sd, SOL_SOCKET, SO_REUSEADDR, (void *) &optval, sizeof (int)); err = bind (listen_sd, (SA *) & sa_serv, sizeof (sa_serv)); SOCKET_ERR (err, "bind"); err = listen (listen_sd, 1024); SOCKET_ERR (err, "listen"); printf ("%s ready. Listening to port '%d'.\n\n", name, PORT); client_len = sizeof (sa_cli); for (;;) { session = initialize_tls_session (); sd = accept (listen_sd, (SA *) & sa_cli, &client_len); printf ("- connection from %s, port %d\n", inet_ntop (AF_INET, &sa_cli.sin_addr, topbuf, sizeof (topbuf)), ntohs (sa_cli.sin_port)); gnutls_transport_set_ptr (session, (gnutls_transport_ptr_t) sd); ret = gnutls_handshake (session); if (ret < 0) { close (sd); gnutls_deinit (session); fprintf (stderr, "*** Handshake has failed (%s)\n\n", gnutls_strerror (ret)); continue; } printf ("- Handshake was completed\n"); /* print_info(session); */ for (;;) { memset (buffer, 0, MAX_BUF + 1); ret = gnutls_record_recv (session, buffer, MAX_BUF); if (ret == 0) { printf ("\n- Peer has closed the GnuTLS connection\n"); break; } else if (ret < 0) { fprintf (stderr, "\n*** Received corrupted " "data(%d). Closing the connection.\n\n", ret); break; } else if (ret > 0) { /* echo data back to the client */ gnutls_record_send (session, buffer, strlen (buffer)); } } printf ("\n"); /* do not wait for the peer to close the connection. */ gnutls_bye (session, GNUTLS_SHUT_WR); close (sd); gnutls_deinit (session); } close (listen_sd); gnutls_srp_free_server_credentials (srp_cred); gnutls_certificate_free_credentials (cert_cred); gnutls_global_deinit (); return 0; }  File: gnutls.info, Node: Echo Server with anonymous authentication, Prev: Echo Server with SRP authentication, Up: Server examples 7.4.4 Echo Server with Anonymous Authentication ----------------------------------------------- This example server support anonymous authentication, and could be used to serve the example client for anonymous authentication. /* This example code is placed in the public domain. */ #ifdef HAVE_CONFIG_H #include #endif #include #include #include #include #include #include #include #include #include #include /* This is a sample TLS 1.0 echo server, for anonymous authentication only. */ #define SA struct sockaddr #define SOCKET_ERR(err,s) if(err==-1) {perror(s);return(1);} #define MAX_BUF 1024 #define PORT 5556 /* listen to 5556 port */ #define DH_BITS 1024 /* These are global */ gnutls_anon_server_credentials_t anoncred; static gnutls_session_t initialize_tls_session (void) { gnutls_session_t session; gnutls_init (&session, GNUTLS_SERVER); gnutls_priority_set_direct (session, "NORMAL:+ANON-DH", NULL); gnutls_credentials_set (session, GNUTLS_CRD_ANON, anoncred); gnutls_dh_set_prime_bits (session, DH_BITS); return session; } static gnutls_dh_params_t dh_params; static int generate_dh_params (void) { /* Generate Diffie-Hellman parameters - for use with DHE * kx algorithms. These should be discarded and regenerated * once a day, once a week or once a month. Depending on the * security requirements. */ gnutls_dh_params_init (&dh_params); gnutls_dh_params_generate2 (dh_params, DH_BITS); return 0; } int main (void) { int err, listen_sd; int sd, ret; struct sockaddr_in sa_serv; struct sockaddr_in sa_cli; int client_len; char topbuf[512]; gnutls_session_t session; char buffer[MAX_BUF + 1]; int optval = 1; /* this must be called once in the program */ gnutls_global_init (); gnutls_anon_allocate_server_credentials (&anoncred); generate_dh_params (); gnutls_anon_set_server_dh_params (anoncred, dh_params); /* Socket operations */ listen_sd = socket (AF_INET, SOCK_STREAM, 0); SOCKET_ERR (listen_sd, "socket"); memset (&sa_serv, '\0', sizeof (sa_serv)); sa_serv.sin_family = AF_INET; sa_serv.sin_addr.s_addr = INADDR_ANY; sa_serv.sin_port = htons (PORT); /* Server Port number */ setsockopt (listen_sd, SOL_SOCKET, SO_REUSEADDR, (void *) &optval, sizeof (int)); err = bind (listen_sd, (SA *) & sa_serv, sizeof (sa_serv)); SOCKET_ERR (err, "bind"); err = listen (listen_sd, 1024); SOCKET_ERR (err, "listen"); printf ("Server ready. Listening to port '%d'.\n\n", PORT); client_len = sizeof (sa_cli); for (;;) { session = initialize_tls_session (); sd = accept (listen_sd, (SA *) & sa_cli, &client_len); printf ("- connection from %s, port %d\n", inet_ntop (AF_INET, &sa_cli.sin_addr, topbuf, sizeof (topbuf)), ntohs (sa_cli.sin_port)); gnutls_transport_set_ptr (session, (gnutls_transport_ptr_t) sd); ret = gnutls_handshake (session); if (ret < 0) { close (sd); gnutls_deinit (session); fprintf (stderr, "*** Handshake has failed (%s)\n\n", gnutls_strerror (ret)); continue; } printf ("- Handshake was completed\n"); /* see the Getting peer's information example */ /* print_info(session); */ for (;;) { memset (buffer, 0, MAX_BUF + 1); ret = gnutls_record_recv (session, buffer, MAX_BUF); if (ret == 0) { printf ("\n- Peer has closed the GnuTLS connection\n"); break; } else if (ret < 0) { fprintf (stderr, "\n*** Received corrupted " "data(%d). Closing the connection.\n\n", ret); break; } else if (ret > 0) { /* echo data back to the client */ gnutls_record_send (session, buffer, strlen (buffer)); } } printf ("\n"); /* do not wait for the peer to close the connection. */ gnutls_bye (session, GNUTLS_SHUT_WR); close (sd); gnutls_deinit (session); } close (listen_sd); gnutls_anon_free_server_credentials (anoncred); gnutls_global_deinit (); return 0; }  File: gnutls.info, Node: Miscellaneous examples, Next: Parameter generation, Prev: Server examples, Up: How to use GnuTLS in applications 7.5 Miscellaneous Examples ========================== * Menu: * Checking for an alert:: * X.509 certificate parsing example:: * Certificate request generation:: * PKCS #12 structure generation::  File: gnutls.info, Node: Checking for an alert, Next: X.509 certificate parsing example, Up: Miscellaneous examples 7.5.1 Checking for an Alert --------------------------- This is a function that checks if an alert has been received in the current session. /* This example code is placed in the public domain. */ #ifdef HAVE_CONFIG_H #include #endif #include #include #include #include "examples.h" /* This function will check whether the given return code from * a gnutls function (recv/send), is an alert, and will print * that alert. */ void check_alert (gnutls_session_t session, int ret) { int last_alert; if (ret == GNUTLS_E_WARNING_ALERT_RECEIVED || ret == GNUTLS_E_FATAL_ALERT_RECEIVED) { last_alert = gnutls_alert_get (session); /* The check for renegotiation is only useful if we are * a server, and we had requested a rehandshake. */ if (last_alert == GNUTLS_A_NO_RENEGOTIATION && ret == GNUTLS_E_WARNING_ALERT_RECEIVED) printf ("* Received NO_RENEGOTIATION alert. " "Client Does not support renegotiation.\n"); else printf ("* Received alert '%d': %s.\n", last_alert, gnutls_alert_get_name (last_alert)); } }  File: gnutls.info, Node: X.509 certificate parsing example, Next: Certificate request generation, Prev: Checking for an alert, Up: Miscellaneous examples 7.5.2 X.509 Certificate Parsing Example --------------------------------------- To demonstrate the X.509 parsing capabilities an example program is listed below. That program reads the peer's certificate, and prints information about it. /* This example code is placed in the public domain. */ #ifdef HAVE_CONFIG_H #include #endif #include #include #include #include #include "examples.h" static const char * bin2hex (const void *bin, size_t bin_size) { static char printable[110]; const unsigned char *_bin = bin; char *print; size_t i; if (bin_size > 50) bin_size = 50; print = printable; for (i = 0; i < bin_size; i++) { sprintf (print, "%.2x ", _bin[i]); print += 2; } return printable; } /* This function will print information about this session's peer * certificate. */ void print_x509_certificate_info (gnutls_session_t session) { char serial[40]; char dn[256]; size_t size; unsigned int algo, bits; time_t expiration_time, activation_time; const gnutls_datum_t *cert_list; unsigned int cert_list_size = 0; gnutls_x509_crt_t cert; gnutls_datum_t cinfo; /* This function only works for X.509 certificates. */ if (gnutls_certificate_type_get (session) != GNUTLS_CRT_X509) return; cert_list = gnutls_certificate_get_peers (session, &cert_list_size); printf ("Peer provided %d certificates.\n", cert_list_size); if (cert_list_size > 0) { int ret; /* we only print information about the first certificate. */ gnutls_x509_crt_init (&cert); gnutls_x509_crt_import (cert, &cert_list[0], GNUTLS_X509_FMT_DER); printf ("Certificate info:\n"); /* This is the preferred way of printing short information about a certificate. */ ret = gnutls_x509_crt_print (cert, GNUTLS_CRT_PRINT_ONELINE, &cinfo); if (ret == 0) { printf ("\t%s\n", cinfo.data); gnutls_free (cinfo.data); } /* If you want to extract fields manually for some other reason, below are popular example calls. */ expiration_time = gnutls_x509_crt_get_expiration_time (cert); activation_time = gnutls_x509_crt_get_activation_time (cert); printf ("\tCertificate is valid since: %s", ctime (&activation_time)); printf ("\tCertificate expires: %s", ctime (&expiration_time)); /* Print the serial number of the certificate. */ size = sizeof (serial); gnutls_x509_crt_get_serial (cert, serial, &size); printf ("\tCertificate serial number: %s\n", bin2hex (serial, size)); /* Extract some of the public key algorithm's parameters */ algo = gnutls_x509_crt_get_pk_algorithm (cert, &bits); printf ("Certificate public key: %s", gnutls_pk_algorithm_get_name (algo)); /* Print the version of the X.509 * certificate. */ printf ("\tCertificate version: #%d\n", gnutls_x509_crt_get_version (cert)); size = sizeof (dn); gnutls_x509_crt_get_dn (cert, dn, &size); printf ("\tDN: %s\n", dn); size = sizeof (dn); gnutls_x509_crt_get_issuer_dn (cert, dn, &size); printf ("\tIssuer's DN: %s\n", dn); gnutls_x509_crt_deinit (cert); } }  File: gnutls.info, Node: Certificate request generation, Next: PKCS #12 structure generation, Prev: X.509 certificate parsing example, Up: Miscellaneous examples 7.5.3 Certificate Request Generation ------------------------------------ The following example is about generating a certificate request, and a private key. A certificate request can be later be processed by a CA, which should return a signed certificate. /* This example code is placed in the public domain. */ #ifdef HAVE_CONFIG_H #include #endif #include #include #include #include #include #include #include /* This example will generate a private key and a certificate * request. */ int main (void) { gnutls_x509_crq_t crq; gnutls_x509_privkey_t key; gnutls_privkey_t pkey; /* object used for signing */ unsigned char buffer[10 * 1024]; size_t buffer_size = sizeof (buffer); unsigned int bits; gnutls_global_init (); /* Initialize an empty certificate request, and * an empty private key. */ gnutls_x509_crq_init (&crq); gnutls_x509_privkey_init (&key); gnutls_privkey_init (&pkey); /* Generate an RSA key of moderate security. */ bits = gnutls_sec_param_to_pk_bits (GNUTLS_PK_RSA, GNUTLS_SEC_PARAM_NORMAL); gnutls_x509_privkey_generate (key, GNUTLS_PK_RSA, bits, 0); /* Add stuff to the distinguished name */ gnutls_x509_crq_set_dn_by_oid (crq, GNUTLS_OID_X520_COUNTRY_NAME, 0, "GR", 2); gnutls_x509_crq_set_dn_by_oid (crq, GNUTLS_OID_X520_COMMON_NAME, 0, "Nikos", strlen ("Nikos")); /* Set the request version. */ gnutls_x509_crq_set_version (crq, 1); /* Set a challenge password. */ gnutls_x509_crq_set_challenge_password (crq, "something to remember here"); /* Associate the request with the private key */ gnutls_x509_crq_set_key (crq, key); /* Self sign the certificate request. */ gnutls_privkey_import_x509( pkey, key, 0); gnutls_x509_crq_privkey_sign (crq, pkey, GNUTLS_DIG_SHA1, 0); /* Export the PEM encoded certificate request, and * display it. */ gnutls_x509_crq_export (crq, GNUTLS_X509_FMT_PEM, buffer, &buffer_size); printf ("Certificate Request: \n%s", buffer); /* Export the PEM encoded private key, and * display it. */ buffer_size = sizeof (buffer); gnutls_x509_privkey_export (key, GNUTLS_X509_FMT_PEM, buffer, &buffer_size); printf ("\n\nPrivate key: \n%s", buffer); gnutls_x509_crq_deinit (crq); gnutls_x509_privkey_deinit (key); return 0; }  File: gnutls.info, Node: PKCS #12 structure generation, Prev: Certificate request generation, Up: Miscellaneous examples 7.5.4 PKCS #12 Structure Generation ----------------------------------- The following example is about generating a PKCS #12 structure. /* This example code is placed in the public domain. */ #ifdef HAVE_CONFIG_H #include #endif #include #include #include #include #include "examples.h" #define OUTFILE "out.p12" /* This function will write a pkcs12 structure into a file. * cert: is a DER encoded certificate * pkcs8_key: is a PKCS #8 encrypted key (note that this must be * encrypted using a PKCS #12 cipher, or some browsers will crash) * password: is the password used to encrypt the PKCS #12 packet. */ int write_pkcs12 (const gnutls_datum_t * cert, const gnutls_datum_t * pkcs8_key, const char *password) { gnutls_pkcs12_t pkcs12; int ret, bag_index; gnutls_pkcs12_bag_t bag, key_bag; char pkcs12_struct[10 * 1024]; size_t pkcs12_struct_size; FILE *fd; /* A good idea might be to use gnutls_x509_privkey_get_key_id() * to obtain a unique ID. */ gnutls_datum_t key_id = { (char *) "\x00\x00\x07", 3 }; gnutls_global_init (); /* Firstly we create two helper bags, which hold the certificate, * and the (encrypted) key. */ gnutls_pkcs12_bag_init (&bag); gnutls_pkcs12_bag_init (&key_bag); ret = gnutls_pkcs12_bag_set_data (bag, GNUTLS_BAG_CERTIFICATE, cert); if (ret < 0) { fprintf (stderr, "ret: %s\n", gnutls_strerror (ret)); return 1; } /* ret now holds the bag's index. */ bag_index = ret; /* Associate a friendly name with the given certificate. Used * by browsers. */ gnutls_pkcs12_bag_set_friendly_name (bag, bag_index, "My name"); /* Associate the certificate with the key using a unique key * ID. */ gnutls_pkcs12_bag_set_key_id (bag, bag_index, &key_id); /* use weak encryption for the certificate. */ gnutls_pkcs12_bag_encrypt (bag, password, GNUTLS_PKCS_USE_PKCS12_RC2_40); /* Now the key. */ ret = gnutls_pkcs12_bag_set_data (key_bag, GNUTLS_BAG_PKCS8_ENCRYPTED_KEY, pkcs8_key); if (ret < 0) { fprintf (stderr, "ret: %s\n", gnutls_strerror (ret)); return 1; } /* Note that since the PKCS #8 key is already encrypted we don't * bother encrypting that bag. */ bag_index = ret; gnutls_pkcs12_bag_set_friendly_name (key_bag, bag_index, "My name"); gnutls_pkcs12_bag_set_key_id (key_bag, bag_index, &key_id); /* The bags were filled. Now create the PKCS #12 structure. */ gnutls_pkcs12_init (&pkcs12); /* Insert the two bags in the PKCS #12 structure. */ gnutls_pkcs12_set_bag (pkcs12, bag); gnutls_pkcs12_set_bag (pkcs12, key_bag); /* Generate a message authentication code for the PKCS #12 * structure. */ gnutls_pkcs12_generate_mac (pkcs12, password); pkcs12_struct_size = sizeof (pkcs12_struct); ret = gnutls_pkcs12_export (pkcs12, GNUTLS_X509_FMT_DER, pkcs12_struct, &pkcs12_struct_size); if (ret < 0) { fprintf (stderr, "ret: %s\n", gnutls_strerror (ret)); return 1; } fd = fopen (OUTFILE, "w"); if (fd == NULL) { fprintf (stderr, "cannot open file\n"); return 1; } fwrite (pkcs12_struct, 1, pkcs12_struct_size, fd); fclose (fd); gnutls_pkcs12_bag_deinit (bag); gnutls_pkcs12_bag_deinit (key_bag); gnutls_pkcs12_deinit (pkcs12); return 0; }  File: gnutls.info, Node: Parameter generation, Next: Keying Material Exporters, Prev: Miscellaneous examples, Up: How to use GnuTLS in applications 7.6 Parameter generation ======================== Several TLS ciphersuites require additional parameters that need to be generated or provided by the application. The Diffie-Hellman based ciphersuites (ANON-DH or DHE), require the group information to be provided. This information can be either be generated on the fly using *Note gnutls_dh_params_generate2:: or imported from some pregenerated value using *Note gnutls_dh_params_import_pkcs3::. The parameters can be used in a session by calling *Note gnutls_certificate_set_dh_params:: or *Note gnutls_anon_set_server_dh_params:: for anonymous sessions. Due to the time-consuming calculations required for the generation of Diffie-Hellman parameters we suggest against performing generation of them within an application. The `certtool' tool can be used to generate or export known safe values that can be stored in code or in a configuration file to provide the ability to replace. We also recommend the usage of *Note gnutls_sec_param_to_pk_bits:: to determine the bit size of the parameters to be generated. The ciphersuites that involve the RSA-EXPORT key exchange require additional parameters. Those ciphersuites are rarely used today because they are by design insecure, thus if you have no requirement for them, this section should be skipped. The RSA-EXPORT key exchange requires 512-bit RSA keys to be generated. It is recommended those parameters to be refreshed (regenerated) in short intervals. The following functions can be used for these parameters. * *Note gnutls_rsa_params_generate2:: * *Note gnutls_certificate_set_rsa_export_params:: * *Note gnutls_rsa_params_import_pkcs1:: * *Note gnutls_rsa_params_export_pkcs1::  File: gnutls.info, Node: Keying Material Exporters, Next: Channel Bindings, Prev: Parameter generation, Up: How to use GnuTLS in applications 7.7 Keying Material Exporters ============================= The TLS PRF can be used by other protocols to derive data. The API to use is *Note gnutls_prf::. The function needs to be provided with the label in the parameter `label', and the extra data to mix in the `extra' parameter. Depending on whether you want to mix in the client or server random data first, you can set the `server_random_first' parameter. For example, after establishing a TLS session using *Note gnutls_handshake::, you can invoke the TLS PRF with this call: #define MYLABEL "EXPORTER-FOO" #define MYCONTEXT "some context data" char out[32]; rc = gnutls_prf (session, strlen (MYLABEL), MYLABEL, 0, strlen (MYCONTEXT), MYCONTEXT, 32, out); If you don't want to mix in the client/server random, there is a more low-level TLS PRF interface called *Note gnutls_prf_raw::.  File: gnutls.info, Node: Channel Bindings, Next: Compatibility with the OpenSSL library, Prev: Keying Material Exporters, Up: How to use GnuTLS in applications 7.8 Channel Bindings ==================== In user authentication protocols (e.g., EAP or SASL mechanisms) it is useful to have a unique string that identifies the secure channel that is used, to bind together the user authentication with the secure channel. This can protect against man-in-the-middle attacks in some situations. The unique strings is a "channel bindings". For background and more discussion see [RFC5056] (*note Bibliography::). You can extract a channel bindings using the *Note gnutls_session_channel_binding:: function. Currently only the `GNUTLS_CB_TLS_UNIQUE' type is supported, which corresponds to the `tls-unique' channel bindings for TLS defined in [RFC5929] (*note Bibliography::). The following example describes how to print the channel binding data. Note that it must be run after a successful TLS handshake. { gnutls_datum cb; int rc; rc = gnutls_session_channel_binding (session, GNUTLS_CB_TLS_UNIQUE, &cb); if (rc) fprintf (stderr, "Channel binding error: %s\n", gnutls_strerror (rc)); else { size_t i; printf ("- Channel binding 'tls-unique': "); for (i = 0; i < cb.size; i++) printf ("%02x", cb.data[i]); printf ("\n"); } }  File: gnutls.info, Node: Compatibility with the OpenSSL library, Prev: Channel Bindings, Up: How to use GnuTLS in applications 7.9 Compatibility with the OpenSSL Library ========================================== To ease GnuTLS' integration with existing applications, a compatibility layer with the widely used OpenSSL library is included in the `gnutls-openssl' library. This compatibility layer is not complete and it is not intended to completely reimplement the OpenSSL API with GnuTLS. It only provides source-level compatibility. There is currently no attempt to make it binary-compatible with OpenSSL. The prototypes for the compatibility functions are in the `gnutls/openssl.h' header file. Current limitations imposed by the compatibility layer include: * Error handling is not thread safe.  File: gnutls.info, Node: Included programs, Next: Function reference, Prev: How to use GnuTLS in applications, Up: Top 8 Included Programs ******************* Included with GnuTLS are also a few command line tools that let you use the library for common tasks without writing an application. The applications are discussed in this chapter. * Menu: * Invoking certtool:: * Invoking gnutls-cli:: * Invoking gnutls-cli-debug:: * Invoking gnutls-serv:: * Invoking psktool:: * Invoking srptool:: * Invoking p11tool::  File: gnutls.info, Node: Invoking certtool, Next: Invoking gnutls-cli, Up: Included programs 8.1 Invoking certtool ===================== This is a program to generate X.509 certificates, certificate requests, CRLs and private keys. Certtool help Usage: certtool [options] -s, --generate-self-signed Generate a self-signed certificate. -c, --generate-certificate Generate a signed certificate. --generate-proxy Generate a proxy certificate. --generate-crl Generate a CRL. -u, --update-certificate Update a signed certificate. -p, --generate-privkey Generate a private key. -q, --generate-request Generate a PKCS #10 certificate request. -e, --verify-chain Verify a PEM encoded certificate chain. The last certificate in the chain must be a self signed one. --verify-crl Verify a CRL. --generate-dh-params Generate PKCS #3 encoded Diffie-Hellman parameters. --get-dh-params Get the included PKCS #3 encoded Diffie Hellman parameters. --load-privkey FILE Private key file to use. --load-request FILE Certificate request file to use. --load-certificate FILE Certificate file to use. --load-ca-privkey FILE Certificate authority's private key file to use. --load-ca-certificate FILE Certificate authority's certificate file to use. --password PASSWORD Password to use. -i, --certificate-info Print information on a certificate. -l, --crl-info Print information on a CRL. --p12-info Print information on a PKCS #12 structure. --p7-info Print information on a PKCS #7 structure. --smime-to-p7 Convert S/MIME to PKCS #7 structure. -k, --key-info Print information on a private key. --fix-key Regenerate the parameters in a private key. --to-p12 Generate a PKCS #12 structure. -8, --pkcs8 Use PKCS #8 format for private keys. --dsa Use DSA keys. --hash STR Hash algorithm to use for signing (MD5,SHA1,RMD160). --export-ciphers Use weak encryption algorithms. --inder Use DER format for input certificates and private keys. --outder Use DER format for output certificates and private keys. --bits BITS specify the number of bits for key generation. --outfile FILE Output file. --infile FILE Input file. --template FILE Template file to use for non interactive operation. -d, --debug LEVEL specify the debug level. Default is 1. -h, --help shows this help text -v, --version shows the program's version The program can be used interactively or non interactively by specifying the `--template' command line option. See below for an example of a template file. How to use certtool interactively: * To generate parameters for Diffie-Hellman key exchange, use the command: $ certtool --generate-dh-params --outfile dh.pem * To generate parameters for the RSA-EXPORT key exchange, use the command: $ certtool --generate-privkey --bits 512 --outfile rsa.pem * To create a self signed certificate, use the command: $ certtool --generate-privkey --outfile ca-key.pem $ certtool --generate-self-signed --load-privkey ca-key.pem \ --outfile ca-cert.pem Note that a self-signed certificate usually belongs to a certificate authority, that signs other certificates. * To create a private key (RSA by default), run: $ certtool --generate-privkey --outfile key.pem To create a DSA private key, run: $ certtool --dsa --generate-privkey --outfile key-dsa.pem * To generate a certificate using the private key, use the command: $ certtool --generate-certificate --load-privkey key.pem \ --outfile cert.pem --load-ca-certificate ca-cert.pem \ --load-ca-privkey ca-key.pem * To create a certificate request (needed when the certificate is issued by another party), run: $ certtool --generate-request --load-privkey key.pem \ --outfile request.pem * To generate a certificate using the previous request, use the command: $ certtool --generate-certificate --load-request request.pem \ --outfile cert.pem \ --load-ca-certificate ca-cert.pem --load-ca-privkey ca-key.pem * To view the certificate information, use: $ certtool --certificate-info --infile cert.pem * To generate a PKCS #12 structure using the previous key and certificate, use the command: $ certtool --load-certificate cert.pem --load-privkey key.pem \ --to-p12 --outder --outfile key.p12 Some tools (reportedly web browsers) have problems with that file because it does not contain the CA certificate for the certificate. To work around that problem in the tool, you can use the `--load-ca-certificate' parameter as follows: $ certtool --load-ca-certificate ca.pem \ --load-certificate cert.pem --load-privkey key.pem \ --to-p12 --outder --outfile key.p12 * Proxy certificate can be used to delegate your credential to a temporary, typically short-lived, certificate. To create one from the previously created certificate, first create a temporary key and then generate a proxy certificate for it, using the commands: $ certtool --generate-privkey > proxy-key.pem $ certtool --generate-proxy --load-ca-privkey key.pem \ --load-privkey proxy-key.pem --load-certificate cert.pem \ --outfile proxy-cert.pem * To create an empty Certificate Revocation List (CRL) do: $ certtool --generate-crl --load-ca-privkey x509-ca-key.pem --load-ca-certificate x509-ca.pem To create a CRL that contains some revoked certificates, place the certificates in a file and use `--load-certificate' as follows: $ certtool --generate-crl --load-ca-privkey x509-ca-key.pem --load-ca-certificate x509-ca.pem --load-certificate revoked-certs.pem * To verify a Certificate Revocation List (CRL) do: $ certtool --verify-crl --load-ca-certificate x509-ca.pem < crl.pem Certtool's template file format: * Firstly create a file named 'cert.cfg' that contains the information about the certificate. An example file is listed below. * Then execute: $ certtool --generate-certificate cert.pem --load-privkey key.pem \ --template cert.cfg \ --load-ca-certificate ca-cert.pem --load-ca-privkey ca-key.pem An example certtool template file: # X.509 Certificate options # # DN options # The organization of the subject. organization = "Koko inc." # The organizational unit of the subject. unit = "sleeping dept." # The locality of the subject. # locality = # The state of the certificate owner. state = "Attiki" # The country of the subject. Two letter code. country = GR # The common name of the certificate owner. cn = "Cindy Lauper" # A user id of the certificate owner. #uid = "clauper" # If the supported DN OIDs are not adequate you can set # any OID here. # For example set the X.520 Title and the X.520 Pseudonym # by using OID and string pairs. #dn_oid = "2.5.4.12" "Dr." "2.5.4.65" "jackal" # This is deprecated and should not be used in new # certificates. # pkcs9_email = "none@none.org" # The serial number of the certificate serial = 007 # In how many days, counting from today, this certificate will expire. expiration_days = 700 # X.509 v3 extensions # A dnsname in case of a WWW server. #dns_name = "www.none.org" #dns_name = "www.morethanone.org" # An IP address in case of a server. #ip_address = "192.168.1.1" # An email in case of a person email = "none@none.org" # An URL that has CRLs (certificate revocation lists) # available. Needed in CA certificates. #crl_dist_points = "http://www.getcrl.crl/getcrl/" # Whether this is a CA certificate or not #ca # Whether this certificate will be used for a TLS client #tls_www_client # Whether this certificate will be used for a TLS server #tls_www_server # Whether this certificate will be used to sign data (needed # in TLS DHE ciphersuites). signing_key # Whether this certificate will be used to encrypt data (needed # in TLS RSA ciphersuites). Note that it is preferred to use different # keys for encryption and signing. #encryption_key # Whether this key will be used to sign other certificates. #cert_signing_key # Whether this key will be used to sign CRLs. #crl_signing_key # Whether this key will be used to sign code. #code_signing_key # Whether this key will be used to sign OCSP data. #ocsp_signing_key # Whether this key will be used for time stamping. #time_stamping_key # Whether this key will be used for IPsec IKE operations. #ipsec_ike_key  File: gnutls.info, Node: Invoking gnutls-cli, Next: Invoking gnutls-cli-debug, Prev: Invoking certtool, Up: Included programs 8.2 Invoking gnutls-cli ======================= Simple client program to set up a TLS connection to some other computer. It sets up a TLS connection and forwards data from the standard input to the secured socket and vice versa. GnuTLS test client Usage: gnutls-cli [options] hostname -d, --debug integer Enable debugging -r, --resume Connect, establish a session. Connect again and resume this session. -s, --starttls Connect, establish a plain session and start TLS when EOF or a SIGALRM is received. --crlf Send CR LF instead of LF. --x509fmtder Use DER format for certificates to read from. -f, --fingerprint Send the openpgp fingerprint, instead of the key. --disable-extensions Disable all the TLS extensions. --print-cert Print the certificate in PEM format. --recordsize integer The maximum record size to advertize. -V, --verbose More verbose output. --ciphers cipher1 cipher2... Ciphers to enable. --protocols protocol1 protocol2... Protocols to enable. --comp comp1 comp2... Compression methods to enable. --macs mac1 mac2... MACs to enable. --kx kx1 kx2... Key exchange methods to enable. --ctypes certType1 certType2... Certificate types to enable. --priority PRIORITY STRING Priorities string. --x509cafile FILE Certificate file to use. --x509crlfile FILE CRL file to use. --pgpkeyfile FILE PGP Key file to use. --pgpkeyring FILE PGP Key ring file to use. --pgpcertfile FILE PGP Public Key (certificate) file to use. --pgpsubkey HEX|auto PGP subkey to use. --x509keyfile FILE X.509 key file to use. --x509certfile FILE X.509 Certificate file to use. --srpusername NAME SRP username to use. --srppasswd PASSWD SRP password to use. --pskusername NAME PSK username to use. --pskkey KEY PSK key (in hex) to use. --opaque-prf-input DATA Use Opaque PRF Input DATA. -p, --port PORT The port to connect to. --insecure Don't abort program if server certificate can't be validated. -l, --list Print a list of the supported algorithms and modes. -h, --help prints this help -v, --version prints the program's version number To connect to a server using PSK authentication, you may use something like: $ gnutls-cli -p 5556 test.gnutls.org --pskusername jas --pskkey 9e32cf7786321a828ef7668f09fb35db --priority NORMAL:+DHE-PSK:+PSK:-RSA:-DHE-RSA -d 4711 * Menu: * Example client PSK connection::  File: gnutls.info, Node: Example client PSK connection, Up: Invoking gnutls-cli 8.2.1 Example client PSK connection ----------------------------------- If your server only supports the PSK ciphersuite, connecting to it should be as simple as connecting to the server: $ ./gnutls-cli -p 5556 localhost Resolving 'localhost'... Connecting to '127.0.0.1:5556'... - PSK client callback. Enter PSK identity: psk_identity Enter password: - PSK authentication. - Version: TLS1.1 - Key Exchange: PSK - Cipher: AES-128-CBC - MAC: SHA1 - Compression: NULL - Handshake was completed - Simple Client Mode: If the server supports several cipher suites, you may need to force it to chose PSK by using a cipher priority parameter such as `--priority NORMAL:+PSK:-RSA:-DHE-RSA:-DHE-PSK'. Instead of using the Netconf-way to derive the PSK key from a password, you can also give the PSK username and key directly on the command line: $ ./gnutls-cli -p 5556 localhost --pskusername psk_identity --pskkey 88f3824b3e5659f52d00e959bacab954b6540344 --priority NORMAL:+DHE-PSK:+PSK Resolving 'localhost'... Connecting to '127.0.0.1:5556'... - PSK authentication. - Version: TLS1.1 - Key Exchange: PSK - Cipher: AES-128-CBC - MAC: SHA1 - Compression: NULL - Handshake was completed - Simple Client Mode: By keeping the `--pskusername' parameter and removing the `--pskkey' parameter, it will query only for the password during the handshake.  File: gnutls.info, Node: Invoking gnutls-cli-debug, Next: Invoking gnutls-serv, Prev: Invoking gnutls-cli, Up: Included programs 8.3 Invoking gnutls-cli-debug ============================= This program was created to assist in debugging GnuTLS, but it might be useful to extract a TLS server's capabilities. It's purpose is to connect onto a TLS server, perform some tests and print the server's capabilities. If called with the `-v' parameter a more checks will be performed. An example output is: crystal:/cvs/gnutls/src$ ./gnutls-cli-debug localhost -p 5556 Resolving 'localhost'... Connecting to '127.0.0.1:5556'... Checking for TLS 1.1 support... yes Checking fallback from TLS 1.1 to... N/A Checking for TLS 1.0 support... yes Checking for SSL 3.0 support... yes Checking for version rollback bug in RSA PMS... no Checking for version rollback bug in Client Hello... no Checking whether we need to disable TLS 1.0... N/A Checking whether the server ignores the RSA PMS version... no Checking whether the server can accept Hello Extensions... yes Checking whether the server can accept cipher suites not in SSL 3.0 spec... yes Checking whether the server can accept a bogus TLS record version in the client hello... yes Checking for certificate information... N/A Checking for trusted CAs... N/A Checking whether the server understands TLS closure alerts... yes Checking whether the server supports session resumption... yes Checking for export-grade ciphersuite support... no Checking RSA-export ciphersuite info... N/A Checking for anonymous authentication support... no Checking anonymous Diffie-Hellman group info... N/A Checking for ephemeral Diffie-Hellman support... no Checking ephemeral Diffie-Hellman group info... N/A Checking for AES cipher support (TLS extension)... yes Checking for 3DES cipher support... yes Checking for ARCFOUR 128 cipher support... yes Checking for ARCFOUR 40 cipher support... no Checking for MD5 MAC support... yes Checking for SHA1 MAC support... yes Checking for ZLIB compression support (TLS extension)... yes Checking for LZO compression support (GnuTLS extension)... yes Checking for max record size (TLS extension)... yes Checking for SRP authentication support (TLS extension)... yes Checking for OpenPGP authentication support (TLS extension)... no  File: gnutls.info, Node: Invoking gnutls-serv, Next: Invoking psktool, Prev: Invoking gnutls-cli-debug, Up: Included programs 8.4 Invoking gnutls-serv ======================== Simple server program that listens to incoming TLS connections. GnuTLS test server Usage: gnutls-serv [options] -d, --debug integer Enable debugging -g, --generate Generate Diffie-Hellman Parameters. -p, --port integer The port to connect to. -q, --quiet Suppress some messages. --nodb Does not use the resume database. --http Act as an HTTP Server. --echo Act as an Echo Server. --dhparams FILE DH params file to use. --x509fmtder Use DER format for certificates --x509cafile FILE Certificate file to use. --x509crlfile FILE CRL file to use. --pgpkeyring FILE PGP Key ring file to use. --pgpkeyfile FILE PGP Key file to use. --pgpcertfile FILE PGP Public Key (certificate) file to use. --pgpsubkey HEX|auto PGP subkey to use. --x509keyfile FILE X.509 key file to use. --x509certfile FILE X.509 Certificate file to use. --x509dsakeyfile FILE Alternative X.509 key file to use. --x509dsacertfile FILE Alternative X.509 certificate file to use. -r, --require-cert Require a valid certificate. -a, --disable-client-cert Disable request for a client certificate. --pskpasswd FILE PSK password file to use. --pskhint HINT PSK identity hint to use. --srppasswd FILE SRP password file to use. --srppasswdconf FILE SRP password conf file to use. --opaque-prf-input DATA Use Opaque PRF Input DATA. --ciphers cipher1 cipher2... Ciphers to enable. --protocols protocol1 protocol2... Protocols to enable. --comp comp1 comp2... Compression methods to enable. --macs mac1 mac2... MACs to enable. --kx kx1 kx2... Key exchange methods to enable. --ctypes certType1 certType2... Certificate types to enable. --priority PRIORITY STRING Priorities string. -l, --list Print a list of the supported algorithms and modes. -h, --help prints this help -v, --version prints the program's version number 8.4.1 Setting Up a Test HTTPS Server ------------------------------------ Running your own TLS server based on GnuTLS can be useful when debugging clients and/or GnuTLS itself. This section describes how to use `gnutls-serv' as a simple HTTPS server. The most basic server can be started as: gnutls-serv --http It will only support anonymous ciphersuites, which many TLS clients refuse to use. The next step is to add support for X.509. First we generate a CA: certtool --generate-privkey > x509-ca-key.pem echo 'cn = GnuTLS test CA' > ca.tmpl echo 'ca' >> ca.tmpl echo 'cert_signing_key' >> ca.tmpl certtool --generate-self-signed --load-privkey x509-ca-key.pem \ --template ca.tmpl --outfile x509-ca.pem ... Then generate a server certificate. Remember to change the dns_name value to the name of your server host, or skip that command to avoid the field. certtool --generate-privkey > x509-server-key.pem echo 'organization = GnuTLS test server' > server.tmpl echo 'cn = test.gnutls.org' >> server.tmpl echo 'tls_www_server' >> server.tmpl echo 'encryption_key' >> server.tmpl echo 'signing_key' >> server.tmpl echo 'dns_name = test.gnutls.org' >> server.tmpl certtool --generate-certificate --load-privkey x509-server-key.pem \ --load-ca-certificate x509-ca.pem --load-ca-privkey x509-ca-key.pem \ --template server.tmpl --outfile x509-server.pem ... For use in the client, you may want to generate a client certificate as well. certtool --generate-privkey > x509-client-key.pem echo 'cn = GnuTLS test client' > client.tmpl echo 'tls_www_client' >> client.tmpl echo 'encryption_key' >> client.tmpl echo 'signing_key' >> client.tmpl certtool --generate-certificate --load-privkey x509-client-key.pem \ --load-ca-certificate x509-ca.pem --load-ca-privkey x509-ca-key.pem \ --template client.tmpl --outfile x509-client.pem ... To be able to import the client key/certificate into some applications, you will need to convert them into a PKCS#12 structure. This also encrypts the security sensitive key with a password. certtool --to-p12 --load-ca-certificate x509-ca.pem --load-privkey x509-client-key.pem --load-certificate x509-client.pem --outder --outfile x509-client.p12 For icing, we'll create a proxy certificate for the client too. certtool --generate-privkey > x509-proxy-key.pem echo 'cn = GnuTLS test client proxy' > proxy.tmpl certtool --generate-proxy --load-privkey x509-proxy-key.pem \ --load-ca-certificate x509-client.pem --load-ca-privkey x509-client-key.pem \ --load-certificate x509-client.pem --template proxy.tmpl \ --outfile x509-proxy.pem ... Then start the server again: gnutls-serv --http \ --x509cafile x509-ca.pem \ --x509keyfile x509-server-key.pem \ --x509certfile x509-server.pem Try connecting to the server using your web browser. Note that the server listens to port 5556 by default. While you are at it, to allow connections using DSA, you can also create a DSA key and certificate for the server. These credentials will be used in the final example below. certtool --generate-privkey --dsa > x509-server-key-dsa.pem certtool --generate-certificate --load-privkey x509-server-key-dsa.pem \ --load-ca-certificate x509-ca.pem --load-ca-privkey x509-ca-key.pem \ --template server.tmpl --outfile x509-server-dsa.pem ... The next step is to create OpenPGP credentials for the server. gpg --gen-key ...enter whatever details you want, use 'test.gnutls.org' as name... Make a note of the OpenPGP key identifier of the newly generated key, here it was `5D1D14D8'. You will need to export the key for GnuTLS to be able to use it. gpg -a --export 5D1D14D8 > openpgp-server.txt gpg --export 5D1D14D8 > openpgp-server.bin gpg --export-secret-keys 5D1D14D8 > openpgp-server-key.bin gpg -a --export-secret-keys 5D1D14D8 > openpgp-server-key.txt Let's start the server with support for OpenPGP credentials: gnutls-serv --http \ --pgpkeyfile openpgp-server-key.txt \ --pgpcertfile openpgp-server.txt The next step is to add support for SRP authentication. srptool --create-conf srp-tpasswd.conf srptool --passwd-conf srp-tpasswd.conf --username jas --passwd srp-passwd.txt Enter password: [TYPE "foo"] Start the server with SRP support: gnutls-serv --http \ --srppasswdconf srp-tpasswd.conf \ --srppasswd srp-passwd.txt Let's also add support for PSK. $ psktool --passwd psk-passwd.txt Start the server with PSK support: gnutls-serv --http \ --pskpasswd psk-passwd.txt Finally, we start the server with all the earlier parameters and you get this command: gnutls-serv --http \ --x509cafile x509-ca.pem \ --x509keyfile x509-server-key.pem \ --x509certfile x509-server.pem \ --x509dsakeyfile x509-server-key-dsa.pem \ --x509dsacertfile x509-server-dsa.pem \ --pgpkeyfile openpgp-server-key.txt \ --pgpcertfile openpgp-server.txt \ --srppasswdconf srp-tpasswd.conf \ --srppasswd srp-passwd.txt \ --pskpasswd psk-passwd.txt * Menu: * Example server PSK connection::  File: gnutls.info, Node: Example server PSK connection, Up: Invoking gnutls-serv 8.4.2 Example server PSK connection ----------------------------------- To set up a PSK server with `gnutls-serv' you need to create PSK password file (*note Invoking psktool::). In the example below, I type `password' at the prompt. $ ./psktool -u psk_identity -p psks.txt Enter password: Key stored to psks.txt $ cat psks.txt psk_identity:88f3824b3e5659f52d00e959bacab954b6540344 $ After this, start the server pointing to the password file. We disable DHE-PSK. $ ./gnutls-serv --pskpasswd psks.txt --pskhint psk_identity_hint --priority NORMAL:-DHE-PSK Set static Diffie-Hellman parameters, consider --dhparams. Echo Server ready. Listening to port '5556'. You can now connect to the server using a PSK client (*note Example client PSK connection::).  File: gnutls.info, Node: Invoking psktool, Next: Invoking srptool, Prev: Invoking gnutls-serv, Up: Included programs 8.5 Invoking psktool ==================== This is a program to manage PSK username and keys. PSKtool help Usage : psktool [options] -u, --username username specify username. -p, --passwd FILE specify a password file. -n, --netconf-hint HINT derive key from Netconf password, using HINT as the psk_identity_hint. -s, --keysize SIZE specify the key size in bytes. -v, --version prints the program's version number -h, --help shows this help text Normally the file will generate random keys for the indicate username. You may also derive PSK keys from passwords, using the algorithm specified in `draft-ietf-netconf-tls-02.txt'. The algorithm needs a PSK identity hint, which you specify using `--netconf-hint'. To derive a PSK key from a password with an empty PSK identity hint, using `--netconf-hint ""'.  File: gnutls.info, Node: Invoking srptool, Next: Invoking p11tool, Prev: Invoking psktool, Up: Included programs 8.6 Invoking srptool ==================== The `srptool' is a very simple program that emulates the programs in the _Stanford SRP libraries_, see `http://srp.stanford.edu/'. It is intended for use in places where you don't expect SRP authentication to be the used for system users. Traditionally _libsrp_ used two files. One called `tpasswd' which holds usernames and verifiers, and `tpasswd.conf' which holds generators and primes. How to use srptool: * To create tpasswd.conf which holds the g and n values for SRP protocol (generator and a large prime), run: $ srptool --create-conf /etc/tpasswd.conf * This command will create /etc/tpasswd and will add user 'test' (you will also be prompted for a password). Verifiers are stored by default in the way libsrp expects. $ srptool --passwd /etc/tpasswd \ --passwd-conf /etc/tpasswd.conf -u test * This command will check against a password. If the password matches the one in /etc/tpasswd you will get an ok. $ srptool --passwd /etc/tpasswd \ --passwd-conf /etc/tpasswd.conf --verify -u test  File: gnutls.info, Node: Invoking p11tool, Prev: Invoking srptool, Up: Included programs 8.7 Invoking p11tool ==================== The `p11tool' is a program that helps with accessing tokens and security modules that support the PKCS #11 API. It requires the individual PKCS #11 modules to be loaded either with the `--provider' option, or by setting up the GnuTLS configuration file for PKCS #11 as in *Note sec:pkcs11::. p11tool help Usage: p11tool [options] --export URL Export an object specified by a pkcs11 URL --list-tokens List all available tokens --list-mechanisms URL List all available mechanisms in token. --list-all List all objects specified by a PKCS#11 URL --list-all-certs List all certificates specified by a PKCS#11 URL --list-certs List certificates that have a private key specified by a PKCS#11 URL --list-privkeys List private keys specified by a PKCS#11 URL --list-trusted List certificates marked as trusted, specified by a PKCS#11 URL --initialize URL Initializes a PKCS11 token. --write URL Writes loaded certificates, private or secret keys to a PKCS11 token. --delete URL Deletes objects matching the URL. --label label Sets a label for the write operation. --trusted Marks the certificate to be imported as trusted. --login Force login to token --detailed-url Export detailed URLs. --no-detailed-url Export less detailed URLs. --secret-key HEX_KEY Provide a hex encoded secret key. --load-privkey FILE Private key file to use. --load-pubkey FILE Private key file to use. --load-certificate FILE Certificate file to use. -8, --pkcs8 Use PKCS #8 format for private keys. --inder Use DER format for input certificates and private keys. --inraw Use RAW/DER format for input certificates and private keys. --provider Library Specify the pkcs11 provider library --outfile FILE Output file. -d, --debug LEVEL specify the debug level. Default is 1. -h, --help shows this help text After being provided the available PKCS #11 modules, it can list all tokens available in your system, the objects on the tokens, and perform operations on them. Some examples on how to use p11tool: * List all tokens $ p11tool --list-tokens * List all objects $ p11tool --login --list-all * To export an object $ p11tool --login --export pkcs11:(OBJECT URL) * To copy an object to a token $ p11tool --login --write pkcs11:(TOKEN URL) --load-certificate (certificate file) --label "my_cert" Note that typically PKCS #11 private key objects are not allowed to be extracted from the token.  File: gnutls.info, Node: Function reference, Next: All the supported ciphersuites in GnuTLS, Prev: Included programs, Up: Top 9 Function Reference ******************** * Menu: * Core functions:: * X.509 certificate functions:: * GnuTLS-extra functions:: * OpenPGP functions:: * TLS Inner Application (TLS/IA) functions:: * Error codes and descriptions::  File: gnutls.info, Node: Core functions, Next: X.509 certificate functions, Up: Function reference 9.1 Core Functions ================== The prototypes for the following functions lie in `gnutls/gnutls.h'. gnutls_alert_get_name --------------------- -- Function: const char * gnutls_alert_get_name (gnutls_alert_description_t ALERT) ALERT: is an alert number `gnutls_session_t' structure. This function will return a string that describes the given alert number, or `NULL'. See `gnutls_alert_get()'. *Returns:* string corresponding to `gnutls_alert_description_t' value. gnutls_alert_get ---------------- -- Function: gnutls_alert_description_t gnutls_alert_get (gnutls_session_t SESSION) SESSION: is a `gnutls_session_t' structure. This function will return the last alert number received. This function should be called if `GNUTLS_E_WARNING_ALERT_RECEIVED' or `GNUTLS_E_FATAL_ALERT_RECEIVED' has been returned by a gnutls function. The peer may send alerts if he thinks some things were not right. Check gnutls.h for the available alert descriptions. If no alert has been received the returned value is undefined. *Returns:* returns the last alert received, a `gnutls_alert_description_t' value. gnutls_alert_send_appropriate ----------------------------- -- Function: int gnutls_alert_send_appropriate (gnutls_session_t SESSION, int ERR) SESSION: is a `gnutls_session_t' structure. ERR: is an integer Sends an alert to the peer depending on the error code returned by a gnutls function. This function will call `gnutls_error_to_alert()' to determine the appropriate alert to send. This function may also return `GNUTLS_E_AGAIN', or `GNUTLS_E_INTERRUPTED'. If the return value is `GNUTLS_E_INVALID_REQUEST', then no alert has been sent to the peer. *Returns:* On success, `GNUTLS_E_SUCCESS' (0) is returned, otherwise an error code is returned. gnutls_alert_send ----------------- -- Function: int gnutls_alert_send (gnutls_session_t SESSION, gnutls_alert_level_t LEVEL, gnutls_alert_description_t DESC) SESSION: is a `gnutls_session_t' structure. LEVEL: is the level of the alert DESC: is the alert description This function will send an alert to the peer in order to inform him of something important (eg. his Certificate could not be verified). If the alert level is Fatal then the peer is expected to close the connection, otherwise he may ignore the alert and continue. The error code of the underlying record send function will be returned, so you may also receive `GNUTLS_E_INTERRUPTED' or `GNUTLS_E_AGAIN' as well. *Returns:* On success, `GNUTLS_E_SUCCESS' (0) is returned, otherwise an error code is returned. gnutls_anon_allocate_client_credentials --------------------------------------- -- Function: int gnutls_anon_allocate_client_credentials (gnutls_anon_client_credentials_t * SC) SC: is a pointer to a `gnutls_anon_client_credentials_t' structure. This structure is complex enough to manipulate directly thus this helper function is provided in order to allocate it. *Returns:* `GNUTLS_E_SUCCESS' on success, or an error code. gnutls_anon_allocate_server_credentials --------------------------------------- -- Function: int gnutls_anon_allocate_server_credentials (gnutls_anon_server_credentials_t * SC) SC: is a pointer to a `gnutls_anon_server_credentials_t' structure. This structure is complex enough to manipulate directly thus this helper function is provided in order to allocate it. *Returns:* `GNUTLS_E_SUCCESS' on success, or an error code. gnutls_anon_free_client_credentials ----------------------------------- -- Function: void gnutls_anon_free_client_credentials (gnutls_anon_client_credentials_t SC) SC: is a `gnutls_anon_client_credentials_t' structure. This structure is complex enough to manipulate directly thus this helper function is provided in order to free (deallocate) it. gnutls_anon_free_server_credentials ----------------------------------- -- Function: void gnutls_anon_free_server_credentials (gnutls_anon_server_credentials_t SC) SC: is a `gnutls_anon_server_credentials_t' structure. This structure is complex enough to manipulate directly thus this helper function is provided in order to free (deallocate) it. gnutls_anon_set_params_function ------------------------------- -- Function: void gnutls_anon_set_params_function (gnutls_anon_server_credentials_t RES, gnutls_params_function * FUNC) RES: is a gnutls_anon_server_credentials_t structure FUNC: is the function to be called This function will set a callback in order for the server to get the Diffie-Hellman or RSA parameters for anonymous authentication. The callback should return zero on success. gnutls_anon_set_server_dh_params -------------------------------- -- Function: void gnutls_anon_set_server_dh_params (gnutls_anon_server_credentials_t RES, gnutls_dh_params_t DH_PARAMS) RES: is a gnutls_anon_server_credentials_t structure DH_PARAMS: is a structure that holds Diffie-Hellman parameters. This function will set the Diffie-Hellman parameters for an anonymous server to use. These parameters will be used in Anonymous Diffie-Hellman cipher suites. gnutls_anon_set_server_params_function -------------------------------------- -- Function: void gnutls_anon_set_server_params_function (gnutls_anon_server_credentials_t RES, gnutls_params_function * FUNC) RES: is a gnutls_certificate_credentials_t structure FUNC: is the function to be called This function will set a callback in order for the server to get the Diffie-Hellman parameters for anonymous authentication. The callback should return zero on success. gnutls_auth_client_get_type --------------------------- -- Function: gnutls_credentials_type_t gnutls_auth_client_get_type (gnutls_session_t SESSION) SESSION: is a `gnutls_session_t' structure. Returns the type of credentials that were used for client authentication. The returned information is to be used to distinguish the function used to access authentication data. *Returns:* The type of credentials for the client authentication schema, a `gnutls_credentials_type_t' type. gnutls_auth_get_type -------------------- -- Function: gnutls_credentials_type_t gnutls_auth_get_type (gnutls_session_t SESSION) SESSION: is a `gnutls_session_t' structure. Returns type of credentials for the current authentication schema. The returned information is to be used to distinguish the function used to access authentication data. Eg. for CERTIFICATE ciphersuites (key exchange algorithms: `GNUTLS_KX_RSA', `GNUTLS_KX_DHE_RSA'), the same function are to be used to access the authentication data. *Returns:* The type of credentials for the current authentication schema, a `gnutls_credentials_type_t' type. gnutls_auth_server_get_type --------------------------- -- Function: gnutls_credentials_type_t gnutls_auth_server_get_type (gnutls_session_t SESSION) SESSION: is a `gnutls_session_t' structure. Returns the type of credentials that were used for server authentication. The returned information is to be used to distinguish the function used to access authentication data. *Returns:* The type of credentials for the server authentication schema, a `gnutls_credentials_type_t' type. gnutls_bye ---------- -- Function: int gnutls_bye (gnutls_session_t SESSION, gnutls_close_request_t HOW) SESSION: is a `gnutls_session_t' structure. HOW: is an integer Terminates the current TLS/SSL connection. The connection should have been initiated using `gnutls_handshake()'. `how' should be one of `GNUTLS_SHUT_RDWR', `GNUTLS_SHUT_WR'. In case of `GNUTLS_SHUT_RDWR' then the TLS connection gets terminated and further receives and sends will be disallowed. If the return value is zero you may continue using the connection. `GNUTLS_SHUT_RDWR' actually sends an alert containing a close request and waits for the peer to reply with the same message. In case of `GNUTLS_SHUT_WR' then the TLS connection gets terminated and further sends will be disallowed. In order to reuse the connection you should wait for an EOF from the peer. `GNUTLS_SHUT_WR' sends an alert containing a close request. Note that not all implementations will properly terminate a TLS connection. Some of them, usually for performance reasons, will terminate only the underlying transport layer, thus causing a transmission error to the peer. This error cannot be distinguished from a malicious party prematurely terminating the session, thus this behavior is not recommended. This function may also return `GNUTLS_E_AGAIN' or `GNUTLS_E_INTERRUPTED'; cf. `gnutls_record_get_direction()'. *Returns:* `GNUTLS_E_SUCCESS' on success, or an error code, see function documentation for entire semantics. gnutls_certificate_activation_time_peers ---------------------------------------- -- Function: time_t gnutls_certificate_activation_time_peers (gnutls_session_t SESSION) SESSION: is a gnutls session This function will return the peer's certificate activation time. This is the creation time for openpgp keys. *Returns:* (time_t)-1 on error. *Deprecated:* `gnutls_certificate_verify_peers2()' now verifies activation times. gnutls_certificate_allocate_credentials --------------------------------------- -- Function: int gnutls_certificate_allocate_credentials (gnutls_certificate_credentials_t * RES) RES: is a pointer to a `gnutls_certificate_credentials_t' structure. This structure is complex enough to manipulate directly thus this helper function is provided in order to allocate it. *Returns:* `GNUTLS_E_SUCCESS' on success, or an error code. gnutls_certificate_client_get_request_status -------------------------------------------- -- Function: int gnutls_certificate_client_get_request_status (gnutls_session_t SESSION) SESSION: is a gnutls session Get whether client certificate is requested or not. *Returns:* 0 if the peer (server) did not request client authentication or 1 otherwise, or a negative value in case of error. gnutls_certificate_client_set_retrieve_function ----------------------------------------------- -- Function: void gnutls_certificate_client_set_retrieve_function (gnutls_certificate_credentials_t CRED, gnutls_certificate_client_retrieve_function * FUNC) CRED: is a `gnutls_certificate_credentials_t' structure. FUNC: is the callback function This function sets a callback to be called in order to retrieve the certificate to be used in the handshake. The callback's function prototype is: int (*callback)(gnutls_session_t, const gnutls_datum_t* req_ca_dn, int nreqs, const gnutls_pk_algorithm_t* pk_algos, int pk_algos_length, gnutls_retr_st* st); `req_ca_cert' is only used in X.509 certificates. Contains a list with the CA names that the server considers trusted. Normally we should send a certificate that is signed by one of these CAs. These names are DER encoded. To get a more meaningful value use the function `gnutls_x509_rdn_get()'. `pk_algos' contains a list with server's acceptable signature algorithms. The certificate returned should support the server's given algorithms. `st' should contain the certificates and private keys. If the callback function is provided then gnutls will call it, in the handshake, after the certificate request message has been received. The callback function should set the certificate list to be sent, and return 0 on success. If no certificate was selected then the number of certificates should be set to zero. The value (-1) indicates error and the handshake will be terminated. gnutls_certificate_expiration_time_peers ---------------------------------------- -- Function: time_t gnutls_certificate_expiration_time_peers (gnutls_session_t SESSION) SESSION: is a gnutls session This function will return the peer's certificate expiration time. *Returns:* (time_t)-1 on error. *Deprecated:* `gnutls_certificate_verify_peers2()' now verifies expiration times. gnutls_certificate_free_ca_names -------------------------------- -- Function: void gnutls_certificate_free_ca_names (gnutls_certificate_credentials_t SC) SC: is a `gnutls_certificate_credentials_t' structure. This function will delete all the CA name in the given credentials. Clients may call this to save some memory since in client side the CA names are not used. Servers might want to use this function if a large list of trusted CAs is present and sending the names of it would just consume bandwidth without providing information to client. CA names are used by servers to advertize the CAs they support to clients. gnutls_certificate_free_cas --------------------------- -- Function: void gnutls_certificate_free_cas (gnutls_certificate_credentials_t SC) SC: is a `gnutls_certificate_credentials_t' structure. This function will delete all the CAs associated with the given credentials. Servers that do not use `gnutls_certificate_verify_peers2()' may call this to save some memory. gnutls_certificate_free_credentials ----------------------------------- -- Function: void gnutls_certificate_free_credentials (gnutls_certificate_credentials_t SC) SC: is a `gnutls_certificate_credentials_t' structure. This structure is complex enough to manipulate directly thus this helper function is provided in order to free (deallocate) it. This function does not free any temporary parameters associated with this structure (ie RSA and DH parameters are not freed by this function). gnutls_certificate_free_crls ---------------------------- -- Function: void gnutls_certificate_free_crls (gnutls_certificate_credentials_t SC) SC: is a `gnutls_certificate_credentials_t' structure. This function will delete all the CRLs associated with the given credentials. gnutls_certificate_free_keys ---------------------------- -- Function: void gnutls_certificate_free_keys (gnutls_certificate_credentials_t SC) SC: is a `gnutls_certificate_credentials_t' structure. This function will delete all the keys and the certificates associated with the given credentials. This function must not be called when a TLS negotiation that uses the credentials is in progress. gnutls_certificate_get_issuer ----------------------------- -- Function: int gnutls_certificate_get_issuer (gnutls_certificate_credentials_t SC, gnutls_x509_crt_t CERT, gnutls_x509_crt_t* ISSUER, unsigned int FLAGS) SC: is a `gnutls_certificate_credentials_t' structure. CERT: is the certificate to find issuer for ISSUER: Will hold the issuer if any. Should be treated as constant. FLAGS: Use zero. This function will return the issuer of a given certificate. *Returns:* On success, `GNUTLS_E_SUCCESS' is returned, otherwise a negative error value. gnutls_certificate_get_openpgp_keyring -------------------------------------- -- Function: void gnutls_certificate_get_openpgp_keyring (gnutls_certificate_credentials_t SC, gnutls_openpgp_keyring_t * KEYRING) SC: is a `gnutls_certificate_credentials_t' structure. KEYRING: the exported keyring. Should be treated as constant This function will export the OpenPGP keyring associated with the given credentials. *Since:* 2.4.0 gnutls_certificate_get_ours --------------------------- -- Function: const gnutls_datum_t * gnutls_certificate_get_ours (gnutls_session_t SESSION) SESSION: is a gnutls session Get the certificate as sent to the peer, in the last handshake. These certificates are in raw format. In X.509 this is a certificate list. In OpenPGP this is a single certificate. *Returns:* return a pointer to a `gnutls_datum_t' containing our certificates, or `NULL' in case of an error or if no certificate was used. gnutls_certificate_get_peers ---------------------------- -- Function: const gnutls_datum_t * gnutls_certificate_get_peers (gnutls_session_t SESSION, unsigned int * LIST_SIZE) SESSION: is a gnutls session LIST_SIZE: is the length of the certificate list Get the peer's raw certificate (chain) as sent by the peer. These certificates are in raw format (DER encoded for X.509). In case of a X.509 then a certificate list may be present. The first certificate in the list is the peer's certificate, following the issuer's certificate, then the issuer's issuer etc. In case of OpenPGP keys a single key will be returned in raw format. *Returns:* return a pointer to a `gnutls_datum_t' containing our certificates, or `NULL' in case of an error or if no certificate was used. gnutls_certificate_get_x509_cas ------------------------------- -- Function: void gnutls_certificate_get_x509_cas (gnutls_certificate_credentials_t SC, gnutls_x509_crt_t ** X509_CA_LIST, unsigned int * NCAS) SC: is a `gnutls_certificate_credentials_t' structure. X509_CA_LIST: will point to the CA list. Should be treated as constant NCAS: the number of CAs This function will export all the CAs associated with the given credentials. *Since:* 2.4.0 gnutls_certificate_get_x509_crls -------------------------------- -- Function: void gnutls_certificate_get_x509_crls (gnutls_certificate_credentials_t SC, gnutls_x509_crl_t ** X509_CRL_LIST, unsigned int * NCRLS) SC: is a `gnutls_certificate_credentials_t' structure. X509_CRL_LIST: the exported CRL list. Should be treated as constant NCRLS: the number of exported CRLs This function will export all the CRLs associated with the given credentials. *Since:* 2.4.0 gnutls_certificate_send_x509_rdn_sequence ----------------------------------------- -- Function: void gnutls_certificate_send_x509_rdn_sequence (gnutls_session_t SESSION, int STATUS) SESSION: is a pointer to a `gnutls_session_t' structure. STATUS: is 0 or 1 If status is non zero, this function will order gnutls not to send the rdnSequence in the certificate request message. That is the server will not advertize it's trusted CAs to the peer. If status is zero then the default behaviour will take effect, which is to advertize the server's trusted CAs. This function has no effect in clients, and in authentication methods other than certificate with X.509 certificates. gnutls_certificate_server_set_request ------------------------------------- -- Function: void gnutls_certificate_server_set_request (gnutls_session_t SESSION, gnutls_certificate_request_t REQ) SESSION: is a `gnutls_session_t' structure. REQ: is one of GNUTLS_CERT_REQUEST, GNUTLS_CERT_REQUIRE This function specifies if we (in case of a server) are going to send a certificate request message to the client. If `req' is GNUTLS_CERT_REQUIRE then the server will return an error if the peer does not provide a certificate. If you do not call this function then the client will not be asked to send a certificate. gnutls_certificate_server_set_retrieve_function ----------------------------------------------- -- Function: void gnutls_certificate_server_set_retrieve_function (gnutls_certificate_credentials_t CRED, gnutls_certificate_server_retrieve_function * FUNC) CRED: is a `gnutls_certificate_credentials_t' structure. FUNC: is the callback function This function sets a callback to be called in order to retrieve the certificate to be used in the handshake. The callback's function prototype is: int (*callback)(gnutls_session_t, gnutls_retr_st* st); `st' should contain the certificates and private keys. If the callback function is provided then gnutls will call it, in the handshake, after the certificate request message has been received. The callback function should set the certificate list to be sent, and return 0 on success. The value (-1) indicates error and the handshake will be terminated. gnutls_certificate_set_dh_params -------------------------------- -- Function: void gnutls_certificate_set_dh_params (gnutls_certificate_credentials_t RES, gnutls_dh_params_t DH_PARAMS) RES: is a gnutls_certificate_credentials_t structure DH_PARAMS: is a structure that holds Diffie-Hellman parameters. This function will set the Diffie-Hellman parameters for a certificate server to use. These parameters will be used in Ephemeral Diffie-Hellman cipher suites. Note that only a pointer to the parameters are stored in the certificate handle, so if you deallocate the parameters before the certificate is deallocated, you must change the parameters stored in the certificate first. gnutls_certificate_set_params_function -------------------------------------- -- Function: void gnutls_certificate_set_params_function (gnutls_certificate_credentials_t RES, gnutls_params_function * FUNC) RES: is a gnutls_certificate_credentials_t structure FUNC: is the function to be called This function will set a callback in order for the server to get the Diffie-Hellman or RSA parameters for certificate authentication. The callback should return zero on success. gnutls_certificate_set_retrieve_function ---------------------------------------- -- Function: void gnutls_certificate_set_retrieve_function (gnutls_certificate_credentials_t CRED, gnutls_certificate_retrieve_function * FUNC) CRED: is a `gnutls_certificate_credentials_t' structure. FUNC: is the callback function This function sets a callback to be called in order to retrieve the certificate to be used in the handshake. The callback's function prototype is: int (*callback)(gnutls_session_t, const gnutls_datum_t* req_ca_dn, int nreqs, const gnutls_pk_algorithm_t* pk_algos, int pk_algos_length, gnutls_retr2_st* st); `req_ca_cert' is only used in X.509 certificates. Contains a list with the CA names that the server considers trusted. Normally we should send a certificate that is signed by one of these CAs. These names are DER encoded. To get a more meaningful value use the function `gnutls_x509_rdn_get()'. `pk_algos' contains a list with server's acceptable signature algorithms. The certificate returned should support the server's given algorithms. `st' should contain the certificates and private keys. If the callback function is provided then gnutls will call it, in the handshake, after the certificate request message has been received. In server side pk_algos and req_ca_dn are NULL. The callback function should set the certificate list to be sent, and return 0 on success. If no certificate was selected then the number of certificates should be set to zero. The value (-1) indicates error and the handshake will be terminated. gnutls_certificate_set_rsa_export_params ---------------------------------------- -- Function: void gnutls_certificate_set_rsa_export_params (gnutls_certificate_credentials_t RES, gnutls_rsa_params_t RSA_PARAMS) RES: is a gnutls_certificate_credentials_t structure RSA_PARAMS: is a structure that holds temporary RSA parameters. This function will set the temporary RSA parameters for a certificate server to use. These parameters will be used in RSA-EXPORT cipher suites. gnutls_certificate_set_verify_flags ----------------------------------- -- Function: void gnutls_certificate_set_verify_flags (gnutls_certificate_credentials_t RES, unsigned int FLAGS) RES: is a gnutls_certificate_credentials_t structure FLAGS: are the flags This function will set the flags to be used at verification of the certificates. Flags must be OR of the `gnutls_certificate_verify_flags' enumerations. gnutls_certificate_set_verify_function -------------------------------------- -- Function: void gnutls_certificate_set_verify_function (gnutls_certificate_credentials_t CRED, gnutls_certificate_verify_function * FUNC) CRED: is a `gnutls_certificate_credentials_t' structure. FUNC: is the callback function This function sets a callback to be called when peer's certificate has been received in order to verify it on receipt rather than doing after the handshake is completed. The callback's function prototype is: int (*callback)(gnutls_session_t); If the callback function is provided then gnutls will call it, in the handshake, just after the certificate message has been received. To verify or obtain the certificate the `gnutls_certificate_verify_peers2()', `gnutls_certificate_type_get()', `gnutls_certificate_get_peers()' functions can be used. The callback function should return 0 for the handshake to continue or non-zero to terminate. *Since:* 2.10.0 gnutls_certificate_set_verify_limits ------------------------------------ -- Function: void gnutls_certificate_set_verify_limits (gnutls_certificate_credentials_t RES, unsigned int MAX_BITS, unsigned int MAX_DEPTH) RES: is a gnutls_certificate_credentials structure MAX_BITS: is the number of bits of an acceptable certificate (default 8200) MAX_DEPTH: is maximum depth of the verification of a certificate chain (default 5) This function will set some upper limits for the default verification function, `gnutls_certificate_verify_peers2()', to avoid denial of service attacks. You can set them to zero to disable limits. gnutls_certificate_set_x509_crl_file ------------------------------------ -- Function: int gnutls_certificate_set_x509_crl_file (gnutls_certificate_credentials_t RES, const char * CRLFILE, gnutls_x509_crt_fmt_t TYPE) RES: is a `gnutls_certificate_credentials_t' structure. CRLFILE: is a file containing the list of verified CRLs (DER or PEM list) TYPE: is PEM or DER This function adds the trusted CRLs in order to verify client or server certificates. In case of a client this is not required to be called if the certificates are not verified using `gnutls_certificate_verify_peers2()'. This function may be called multiple times. *Returns:* number of CRLs processed or a negative value on error. gnutls_certificate_set_x509_crl_mem ----------------------------------- -- Function: int gnutls_certificate_set_x509_crl_mem (gnutls_certificate_credentials_t RES, const gnutls_datum_t * CRL, gnutls_x509_crt_fmt_t TYPE) RES: is a `gnutls_certificate_credentials_t' structure. CRL: is a list of trusted CRLs. They should have been verified before. TYPE: is DER or PEM This function adds the trusted CRLs in order to verify client or server certificates. In case of a client this is not required to be called if the certificates are not verified using `gnutls_certificate_verify_peers2()'. This function may be called multiple times. *Returns:* number of CRLs processed, or a negative value on error. gnutls_certificate_set_x509_crl ------------------------------- -- Function: int gnutls_certificate_set_x509_crl (gnutls_certificate_credentials_t RES, gnutls_x509_crl_t * CRL_LIST, int CRL_LIST_SIZE) RES: is a `gnutls_certificate_credentials_t' structure. CRL_LIST: is a list of trusted CRLs. They should have been verified before. CRL_LIST_SIZE: holds the size of the crl_list This function adds the trusted CRLs in order to verify client or server certificates. In case of a client this is not required to be called if the certificates are not verified using `gnutls_certificate_verify_peers2()'. This function may be called multiple times. *Returns:* `GNUTLS_E_SUCCESS' on success, or an error code. *Since:* 2.4.0 gnutls_certificate_set_x509_key_file ------------------------------------ -- Function: int gnutls_certificate_set_x509_key_file (gnutls_certificate_credentials_t RES, const char * CERTFILE, const char * KEYFILE, gnutls_x509_crt_fmt_t TYPE) RES: is a `gnutls_certificate_credentials_t' structure. CERTFILE: is a file that containing the certificate list (path) for the specified private key, in PKCS7 format, or a list of certificates KEYFILE: is a file that contains the private key TYPE: is PEM or DER This function sets a certificate/private key pair in the gnutls_certificate_credentials_t structure. This function may be called more than once (in case multiple keys/certificates exist for the server). For clients that wants to send more than its own end entity certificate (e.g., also an intermediate CA cert) then put the certificate chain in `certfile'. Currently only PKCS-1 encoded RSA and DSA private keys are accepted by this function. This function can also accept PKCS `11' URLs. In that case it will import the private key and certificate indicated by the urls. *Returns:* `GNUTLS_E_SUCCESS' on success, or an error code. gnutls_certificate_set_x509_key_mem ----------------------------------- -- Function: int gnutls_certificate_set_x509_key_mem (gnutls_certificate_credentials_t RES, const gnutls_datum_t * CERT, const gnutls_datum_t * KEY, gnutls_x509_crt_fmt_t TYPE) RES: is a `gnutls_certificate_credentials_t' structure. CERT: contains a certificate list (path) for the specified private key KEY: is the private key, or `NULL' TYPE: is PEM or DER This function sets a certificate/private key pair in the gnutls_certificate_credentials_t structure. This function may be called more than once (in case multiple keys/certificates exist for the server). *Currently are supported:* RSA PKCS-1 encoded private keys, DSA private keys. DSA private keys are encoded the OpenSSL way, which is an ASN.1 DER sequence of 6 INTEGERs - version, p, q, g, pub, priv. Note that the keyUsage (2.5.29.15) PKIX extension in X.509 certificates is supported. This means that certificates intended for signing cannot be used for ciphersuites that require encryption. If the certificate and the private key are given in PEM encoding then the strings that hold their values must be null terminated. The `key' may be `NULL' if you are using a sign callback, see `gnutls_sign_callback_set()'. *Returns:* `GNUTLS_E_SUCCESS' on success, or an error code. gnutls_certificate_set_x509_key ------------------------------- -- Function: int gnutls_certificate_set_x509_key (gnutls_certificate_credentials_t RES, gnutls_x509_crt_t * CERT_LIST, int CERT_LIST_SIZE, gnutls_x509_privkey_t KEY) RES: is a `gnutls_certificate_credentials_t' structure. CERT_LIST: contains a certificate list (path) for the specified private key CERT_LIST_SIZE: holds the size of the certificate list KEY: is a gnutls_x509_privkey_t key This function sets a certificate/private key pair in the gnutls_certificate_credentials_t structure. This function may be called more than once (in case multiple keys/certificates exist for the server). For clients that wants to send more than its own end entity certificate (e.g., also an intermediate CA cert) then put the certificate chain in `cert_list'. *Returns:* `GNUTLS_E_SUCCESS' on success, or an error code. *Since:* 2.4.0 gnutls_certificate_set_x509_simple_pkcs12_file ---------------------------------------------- -- Function: int gnutls_certificate_set_x509_simple_pkcs12_file (gnutls_certificate_credentials_t RES, const char * PKCS12FILE, gnutls_x509_crt_fmt_t TYPE, const char * PASSWORD) RES: is a `gnutls_certificate_credentials_t' structure. PKCS12FILE: filename of file containing PKCS`12' blob. TYPE: is PEM or DER of the `pkcs12file'. PASSWORD: optional password used to decrypt PKCS`12' file, bags and keys. This function sets a certificate/private key pair and/or a CRL in the gnutls_certificate_credentials_t structure. This function may be called more than once (in case multiple keys/certificates exist for the server). *MAC:* ed PKCS`12' files are supported. Encrypted PKCS`12' bags are supported. Encrypted PKCS`8' private keys are supported. However, only password based security, and the same password for all operations, are supported. The private keys may be RSA PKCS`1' or DSA private keys encoded in the OpenSSL way. PKCS`12' file may contain many keys and/or certificates, and there is no way to identify which key/certificate pair you want. You should make sure the PKCS`12' file only contain one key/certificate pair and/or one CRL. It is believed that the limitations of this function is acceptable for most usage, and that any more flexibility would introduce complexity that would make it harder to use this functionality at all. *Returns:* `GNUTLS_E_SUCCESS' on success, or an error code. gnutls_certificate_set_x509_simple_pkcs12_mem --------------------------------------------- -- Function: int gnutls_certificate_set_x509_simple_pkcs12_mem (gnutls_certificate_credentials_t RES, const gnutls_datum_t * P12BLOB, gnutls_x509_crt_fmt_t TYPE, const char * PASSWORD) RES: is a `gnutls_certificate_credentials_t' structure. P12BLOB: the PKCS`12' blob. TYPE: is PEM or DER of the `pkcs12file'. PASSWORD: optional password used to decrypt PKCS`12' file, bags and keys. This function sets a certificate/private key pair and/or a CRL in the gnutls_certificate_credentials_t structure. This function may be called more than once (in case multiple keys/certificates exist for the server). *MAC:* ed PKCS`12' files are supported. Encrypted PKCS`12' bags are supported. Encrypted PKCS`8' private keys are supported. However, only password based security, and the same password for all operations, are supported. The private keys may be RSA PKCS`1' or DSA private keys encoded in the OpenSSL way. PKCS`12' file may contain many keys and/or certificates, and there is no way to identify which key/certificate pair you want. You should make sure the PKCS`12' file only contain one key/certificate pair and/or one CRL. It is believed that the limitations of this function is acceptable for most usage, and that any more flexibility would introduce complexity that would make it harder to use this functionality at all. *Returns:* `GNUTLS_E_SUCCESS' on success, or an error code. *Since:* 2.8.0 gnutls_certificate_set_x509_trust_file -------------------------------------- -- Function: int gnutls_certificate_set_x509_trust_file (gnutls_certificate_credentials_t RES, const char * CAFILE, gnutls_x509_crt_fmt_t TYPE) RES: is a `gnutls_certificate_credentials_t' structure. CAFILE: is a file containing the list of trusted CAs (DER or PEM list) TYPE: is PEM or DER This function adds the trusted CAs in order to verify client or server certificates. In case of a client this is not required to be called if the certificates are not verified using `gnutls_certificate_verify_peers2()'. This function may be called multiple times. In case of a server the names of the CAs set here will be sent to the client if a certificate request is sent. This can be disabled using `gnutls_certificate_send_x509_rdn_sequence()'. This function can also accept PKCS `11' URLs. In that case it will import all certificates that are marked as trusted. *Returns:* number of certificates processed, or a negative value on error. gnutls_certificate_set_x509_trust_mem ------------------------------------- -- Function: int gnutls_certificate_set_x509_trust_mem (gnutls_certificate_credentials_t RES, const gnutls_datum_t * CA, gnutls_x509_crt_fmt_t TYPE) RES: is a `gnutls_certificate_credentials_t' structure. CA: is a list of trusted CAs or a DER certificate TYPE: is DER or PEM This function adds the trusted CAs in order to verify client or server certificates. In case of a client this is not required to be called if the certificates are not verified using `gnutls_certificate_verify_peers2()'. This function may be called multiple times. In case of a server the CAs set here will be sent to the client if a certificate request is sent. This can be disabled using `gnutls_certificate_send_x509_rdn_sequence()'. *Returns:* the number of certificates processed or a negative value on error. gnutls_certificate_set_x509_trust --------------------------------- -- Function: int gnutls_certificate_set_x509_trust (gnutls_certificate_credentials_t RES, gnutls_x509_crt_t * CA_LIST, int CA_LIST_SIZE) RES: is a `gnutls_certificate_credentials_t' structure. CA_LIST: is a list of trusted CAs CA_LIST_SIZE: holds the size of the CA list This function adds the trusted CAs in order to verify client or server certificates. In case of a client this is not required to be called if the certificates are not verified using `gnutls_certificate_verify_peers2()'. This function may be called multiple times. In case of a server the CAs set here will be sent to the client if a certificate request is sent. This can be disabled using `gnutls_certificate_send_x509_rdn_sequence()'. *Returns:* `GNUTLS_E_SUCCESS' on success, or an error code. *Since:* 2.4.0 gnutls_certificate_type_get_id ------------------------------ -- Function: gnutls_certificate_type_t gnutls_certificate_type_get_id (const char * NAME) NAME: is a certificate type name The names are compared in a case insensitive way. *Returns:* a `gnutls_certificate_type_t' for the specified in a string certificate type, or `GNUTLS_CRT_UNKNOWN' on error. gnutls_certificate_type_get_name -------------------------------- -- Function: const char * gnutls_certificate_type_get_name (gnutls_certificate_type_t TYPE) TYPE: is a certificate type Convert a `gnutls_certificate_type_t' type to a string. *Returns:* a string that contains the name of the specified certificate type, or `NULL' in case of unknown types. gnutls_certificate_type_get --------------------------- -- Function: gnutls_certificate_type_t gnutls_certificate_type_get (gnutls_session_t SESSION) SESSION: is a `gnutls_session_t' structure. The certificate type is by default X.509, unless it is negotiated as a TLS extension. *Returns:* the currently used `gnutls_certificate_type_t' certificate type. gnutls_certificate_type_list ---------------------------- -- Function: const gnutls_certificate_type_t * gnutls_certificate_type_list ( VOID) Get a list of certificate types. Note that to be able to use OpenPGP certificates, you must link to libgnutls-extra and call `gnutls_global_init_extra()'. *Returns:* a zero-terminated list of `gnutls_certificate_type_t' integers indicating the available certificate types. gnutls_certificate_type_set_priority ------------------------------------ -- Function: int gnutls_certificate_type_set_priority (gnutls_session_t SESSION, const int * LIST) SESSION: is a `gnutls_session_t' structure. LIST: is a 0 terminated list of gnutls_certificate_type_t elements. Sets the priority on the certificate types supported by gnutls. Priority is higher for elements specified before others. After specifying the types you want, you must append a 0. Note that the certificate type priority is set on the client. The server does not use the cert type priority except for disabling types that were not specified. *Returns:* `GNUTLS_E_SUCCESS' on success, or an error code. gnutls_certificate_verify_peers2 -------------------------------- -- Function: int gnutls_certificate_verify_peers2 (gnutls_session_t SESSION, unsigned int * STATUS) SESSION: is a gnutls session STATUS: is the output of the verification This function will try to verify the peer's certificate and return its status (trusted, invalid etc.). The value of `status' should be one or more of the gnutls_certificate_status_t enumerated elements bitwise or'd. To avoid denial of service attacks some default upper limits regarding the certificate key size and chain size are set. To override them use `gnutls_certificate_set_verify_limits()'. Note that you must also check the peer's name in order to check if the verified certificate belongs to the actual peer. This function uses `gnutls_x509_crt_list_verify()' with the CAs in the credentials as trusted CAs. *Returns:* a negative error code on error and zero on success. gnutls_certificate_verify_peers ------------------------------- -- Function: int gnutls_certificate_verify_peers (gnutls_session_t SESSION) SESSION: is a gnutls session This function will try to verify the peer's certificate and return its status (trusted, invalid etc.). However you must also check the peer's name in order to check if the verified certificate belongs to the actual peer. This function uses `gnutls_x509_crt_list_verify()'. *Returns:* one or more of the `gnutls_certificate_status_t' enumerated elements bitwise or'd, or a negative value on error. *Deprecated:* Use `gnutls_certificate_verify_peers2()' instead. gnutls_check_version -------------------- -- Function: const char * gnutls_check_version (const char * REQ_VERSION) REQ_VERSION: version string to compare with, or `NULL'. Check GnuTLS Library version. See `GNUTLS_VERSION' for a suitable `req_version' string. *Return value:* Check that the version of the library is at minimum the one given as a string in `req_version' and return the actual version string of the library; return `NULL' if the condition is not met. If `NULL' is passed to this function no check is done and only the version string is returned. gnutls_cipher_decrypt2 ---------------------- -- Function: int gnutls_cipher_decrypt2 (gnutls_cipher_hd_t HANDLE, const void * CIPHERTEXT, size_t CIPHERTEXTLEN, void * TEXT, size_t TEXTLEN) HANDLE: is a `gnutls_cipher_hd_t' structure. CIPHERTEXT: the data to encrypt CIPHERTEXTLEN: The length of data to encrypt TEXT: the decrypted data TEXTLEN: The available length for decrypted data This function will decrypt the given data using the algorithm specified by the context. *Returns:* Zero or a negative value on error. *Since:* 2.10.0 gnutls_cipher_decrypt --------------------- -- Function: int gnutls_cipher_decrypt (gnutls_cipher_hd_t HANDLE, void * CIPHERTEXT, size_t CIPHERTEXTLEN) HANDLE: is a `gnutls_cipher_hd_t' structure. CIPHERTEXT: the data to encrypt CIPHERTEXTLEN: The length of data to encrypt This function will decrypt the given data using the algorithm specified by the context. *Returns:* Zero or a negative value on error. *Since:* 2.10.0 gnutls_cipher_deinit -------------------- -- Function: void gnutls_cipher_deinit (gnutls_cipher_hd_t HANDLE) HANDLE: is a `gnutls_cipher_hd_t' structure. This function will deinitialize all resources occupied by the given encryption context. *Since:* 2.10.0 gnutls_cipher_encrypt2 ---------------------- -- Function: int gnutls_cipher_encrypt2 (gnutls_cipher_hd_t HANDLE, void * TEXT, size_t TEXTLEN, void * CIPHERTEXT, size_t CIPHERTEXTLEN) HANDLE: is a `gnutls_cipher_hd_t' structure. TEXT: the data to encrypt TEXTLEN: The length of data to encrypt CIPHERTEXT: the encrypted data CIPHERTEXTLEN: The available length for encrypted data This function will encrypt the given data using the algorithm specified by the context. *Returns:* Zero or a negative value on error. *Since:* 2.10.0 gnutls_cipher_encrypt --------------------- -- Function: int gnutls_cipher_encrypt (gnutls_cipher_hd_t HANDLE, void * TEXT, size_t TEXTLEN) HANDLE: is a `gnutls_cipher_hd_t' structure. TEXT: the data to encrypt TEXTLEN: The length of data to encrypt This function will encrypt the given data using the algorithm specified by the context. *Returns:* Zero or a negative value on error. *Since:* 2.10.0 gnutls_cipher_get_block_size ---------------------------- -- Function: int gnutls_cipher_get_block_size (gnutls_cipher_algorithm_t ALGORITHM) ALGORITHM: is an encryption algorithm Get block size for encryption algorithm. *Returns:* block size for encryption algorithm. *Since:* 2.10.0 gnutls_cipher_get_id -------------------- -- Function: gnutls_cipher_algorithm_t gnutls_cipher_get_id (const char * NAME) NAME: is a MAC algorithm name The names are compared in a case insensitive way. *Returns:* return a `gnutls_cipher_algorithm_t' value corresponding to the specified cipher, or `GNUTLS_CIPHER_UNKNOWN' on error. gnutls_cipher_get_key_size -------------------------- -- Function: size_t gnutls_cipher_get_key_size (gnutls_cipher_algorithm_t ALGORITHM) ALGORITHM: is an encryption algorithm Get key size for cipher. *Returns:* length (in bytes) of the given cipher's key size, or 0 if the given cipher is invalid. gnutls_cipher_get_name ---------------------- -- Function: const char * gnutls_cipher_get_name (gnutls_cipher_algorithm_t ALGORITHM) ALGORITHM: is an encryption algorithm Convert a `gnutls_cipher_algorithm_t' type to a string. *Returns:* a pointer to a string that contains the name of the specified cipher, or `NULL'. gnutls_cipher_get ----------------- -- Function: gnutls_cipher_algorithm_t gnutls_cipher_get (gnutls_session_t SESSION) SESSION: is a `gnutls_session_t' structure. Get currently used cipher. *Returns:* the currently used cipher, a `gnutls_cipher_algorithm_t' type. gnutls_cipher_init ------------------ -- Function: int gnutls_cipher_init (gnutls_cipher_hd_t * HANDLE, gnutls_cipher_algorithm_t CIPHER, const gnutls_datum_t * KEY, const gnutls_datum_t * IV) HANDLE: is a `gnutls_cipher_hd_t' structure. CIPHER: the encryption algorithm to use KEY: The key to be used for encryption IV: The IV to use (if not applicable set NULL) This function will initialize an context that can be used for encryption/decryption of data. This will effectively use the current crypto backend in use by gnutls or the cryptographic accelerator in use. *Returns:* Zero or a negative value on error. *Since:* 2.10.0 gnutls_cipher_list ------------------ -- Function: const gnutls_cipher_algorithm_t * gnutls_cipher_list ( VOID) Get a list of supported cipher algorithms. Note that not necessarily all ciphers are supported as TLS cipher suites. For example, DES is not supported as a cipher suite, but is supported for other purposes (e.g., PKCS`8' or similar). *Returns:* a zero-terminated list of `gnutls_cipher_algorithm_t' integers indicating the available ciphers. gnutls_cipher_set_priority -------------------------- -- Function: int gnutls_cipher_set_priority (gnutls_session_t SESSION, const int * LIST) SESSION: is a `gnutls_session_t' structure. LIST: is a 0 terminated list of gnutls_cipher_algorithm_t elements. Sets the priority on the ciphers supported by gnutls. Priority is higher for elements specified before others. After specifying the ciphers you want, you must append a 0. Note that the priority is set on the client. The server does not use the algorithm's priority except for disabling algorithms that were not specified. *Returns:* `GNUTLS_E_SUCCESS' on success, or an error code. gnutls_cipher_suite_get_name ---------------------------- -- Function: const char * gnutls_cipher_suite_get_name (gnutls_kx_algorithm_t KX_ALGORITHM, gnutls_cipher_algorithm_t CIPHER_ALGORITHM, gnutls_mac_algorithm_t MAC_ALGORITHM) KX_ALGORITHM: is a Key exchange algorithm CIPHER_ALGORITHM: is a cipher algorithm MAC_ALGORITHM: is a MAC algorithm Note that the full cipher suite name must be prepended by TLS or SSL depending of the protocol in use. *Returns:* a string that contains the name of a TLS cipher suite, specified by the given algorithms, or `NULL'. gnutls_cipher_suite_info ------------------------ -- Function: const char * gnutls_cipher_suite_info (size_t IDX, char * CS_ID, gnutls_kx_algorithm_t * KX, gnutls_cipher_algorithm_t * CIPHER, gnutls_mac_algorithm_t * MAC, gnutls_protocol_t * MIN_VERSION) IDX: index of cipher suite to get information about, starts on 0. CS_ID: output buffer with room for 2 bytes, indicating cipher suite value KX: output variable indicating key exchange algorithm, or `NULL'. CIPHER: output variable indicating cipher, or `NULL'. MAC: output variable indicating MAC algorithm, or `NULL'. Get information about supported cipher suites. Use the function iteratively to get information about all supported cipher suites. Call with idx=0 to get information about first cipher suite, then idx=1 and so on until the function returns NULL. *Returns:* the name of `idx' cipher suite, and set the information about the cipher suite in the output variables. If `idx' is out of bounds, `NULL' is returned. gnutls_compression_get_id ------------------------- -- Function: gnutls_compression_method_t gnutls_compression_get_id (const char * NAME) NAME: is a compression method name The names are compared in a case insensitive way. *Returns:* an id of the specified in a string compression method, or `GNUTLS_COMP_UNKNOWN' on error. gnutls_compression_get_name --------------------------- -- Function: const char * gnutls_compression_get_name (gnutls_compression_method_t ALGORITHM) ALGORITHM: is a Compression algorithm Convert a `gnutls_compression_method_t' value to a string. *Returns:* a pointer to a string that contains the name of the specified compression algorithm, or `NULL'. gnutls_compression_get ---------------------- -- Function: gnutls_compression_method_t gnutls_compression_get (gnutls_session_t SESSION) SESSION: is a `gnutls_session_t' structure. Get currently used compression algorithm. *Returns:* the currently used compression method, a `gnutls_compression_method_t' value. gnutls_compression_list ----------------------- -- Function: const gnutls_compression_method_t * gnutls_compression_list ( VOID) Get a list of compression methods. Note that to be able to use LZO compression, you must link to libgnutls-extra and call `gnutls_global_init_extra()'. *Returns:* a zero-terminated list of `gnutls_compression_method_t' integers indicating the available compression methods. gnutls_compression_set_priority ------------------------------- -- Function: int gnutls_compression_set_priority (gnutls_session_t SESSION, const int * LIST) SESSION: is a `gnutls_session_t' structure. LIST: is a 0 terminated list of gnutls_compression_method_t elements. Sets the priority on the compression algorithms supported by gnutls. Priority is higher for elements specified before others. After specifying the algorithms you want, you must append a 0. Note that the priority is set on the client. The server does not use the algorithm's priority except for disabling algorithms that were not specified. TLS 1.0 does not define any compression algorithms except NULL. Other compression algorithms are to be considered as gnutls extensions. *Returns:* `GNUTLS_E_SUCCESS' on success, or an error code. gnutls_credentials_clear ------------------------ -- Function: void gnutls_credentials_clear (gnutls_session_t SESSION) SESSION: is a `gnutls_session_t' structure. Clears all the credentials previously set in this session. gnutls_credentials_set ---------------------- -- Function: int gnutls_credentials_set (gnutls_session_t SESSION, gnutls_credentials_type_t TYPE, void * CRED) SESSION: is a `gnutls_session_t' structure. TYPE: is the type of the credentials CRED: is a pointer to a structure. Sets the needed credentials for the specified type. Eg username, password - or public and private keys etc. The `cred' parameter is a structure that depends on the specified type and on the current session (client or server). In order to minimize memory usage, and share credentials between several threads gnutls keeps a pointer to cred, and not the whole cred structure. Thus you will have to keep the structure allocated until you call `gnutls_deinit()'. For `GNUTLS_CRD_ANON', `cred' should be `gnutls_anon_client_credentials_t' in case of a client. In case of a server it should be `gnutls_anon_server_credentials_t'. For `GNUTLS_CRD_SRP', `cred' should be `gnutls_srp_client_credentials_t' in case of a client, and `gnutls_srp_server_credentials_t', in case of a server. For `GNUTLS_CRD_CERTIFICATE', `cred' should be `gnutls_certificate_credentials_t'. *Returns:* On success, `GNUTLS_E_SUCCESS' (zero) is returned, otherwise an error code is returned. gnutls_crypto_bigint_register2 ------------------------------ -- Function: int gnutls_crypto_bigint_register2 (int PRIORITY, int VERSION, const gnutls_crypto_bigint_st * S) PRIORITY: is the priority of the interface VERSION: should be set to `GNUTLS_CRYPTO_API_VERSION' S: is a structure holding new interface's data This function will register an interface for gnutls to operate on big integers. Any interface registered will override the included interface. The interface with the lowest priority will be used by gnutls. Note that the bigint interface must interoperate with the public key interface. Thus if this interface is updated the `gnutls_crypto_pk_register()' should also be used. This function should be called before `gnutls_global_init()'. For simplicity you can use the convenience `gnutls_crypto_bigint_register()' macro. *Returns:* `GNUTLS_E_SUCCESS' on success, otherwise an error. *Since:* 2.6.0 gnutls_crypto_cipher_register2 ------------------------------ -- Function: int gnutls_crypto_cipher_register2 (int PRIORITY, int VERSION, const gnutls_crypto_cipher_st * S) PRIORITY: is the priority of the cipher interface VERSION: should be set to `GNUTLS_CRYPTO_API_VERSION' S: is a structure holding new interface's data This function will register a cipher interface to be used by gnutls. Any interface registered will override the included engine and by convention kernel implemented interfaces should have priority of 90. The interface with the lowest priority will be used by gnutls. This function should be called before `gnutls_global_init()'. For simplicity you can use the convenience `gnutls_crypto_cipher_register()' macro. *Returns:* `GNUTLS_E_SUCCESS' on success, otherwise an error. *Since:* 2.6.0 gnutls_crypto_digest_register2 ------------------------------ -- Function: int gnutls_crypto_digest_register2 (int PRIORITY, int VERSION, const gnutls_crypto_digest_st * S) PRIORITY: is the priority of the digest interface VERSION: should be set to `GNUTLS_CRYPTO_API_VERSION' S: is a structure holding new interface's data This function will register a digest interface to be used by gnutls. Any interface registered will override the included engine and by convention kernel implemented interfaces should have priority of 90. The interface with the lowest priority will be used by gnutls. This function should be called before `gnutls_global_init()'. For simplicity you can use the convenience `gnutls_crypto_digest_register()' macro. *Returns:* `GNUTLS_E_SUCCESS' on success, otherwise an error. *Since:* 2.6.0 gnutls_crypto_mac_register2 --------------------------- -- Function: int gnutls_crypto_mac_register2 (int PRIORITY, int VERSION, const gnutls_crypto_mac_st * S) PRIORITY: is the priority of the mac interface VERSION: should be set to `GNUTLS_CRYPTO_API_VERSION' S: is a structure holding new interface's data This function will register a mac interface to be used by gnutls. Any interface registered will override the included engine and by convention kernel implemented interfaces should have priority of 90. The interface with the lowest priority will be used by gnutls. This function should be called before `gnutls_global_init()'. For simplicity you can use the convenience `gnutls_crypto_digest_register()' macro. *Returns:* `GNUTLS_E_SUCCESS' on success, otherwise an error. *Since:* 2.6.0 gnutls_crypto_pk_register2 -------------------------- -- Function: int gnutls_crypto_pk_register2 (int PRIORITY, int VERSION, const gnutls_crypto_pk_st * S) PRIORITY: is the priority of the interface VERSION: should be set to `GNUTLS_CRYPTO_API_VERSION' S: is a structure holding new interface's data This function will register an interface for gnutls to operate on public key operations. Any interface registered will override the included interface. The interface with the lowest priority will be used by gnutls. Note that the bigint interface must interoperate with the bigint interface. Thus if this interface is updated the `gnutls_crypto_bigint_register()' should also be used. This function should be called before `gnutls_global_init()'. For simplicity you can use the convenience `gnutls_crypto_pk_register()' macro. *Returns:* `GNUTLS_E_SUCCESS' on success, otherwise an error. *Since:* 2.6.0 gnutls_crypto_rnd_register2 --------------------------- -- Function: int gnutls_crypto_rnd_register2 (int PRIORITY, int VERSION, const gnutls_crypto_rnd_st * S) PRIORITY: is the priority of the generator VERSION: should be set to `GNUTLS_CRYPTO_API_VERSION' S: is a structure holding new generator's data This function will register a random generator to be used by gnutls. Any generator registered will override the included generator and by convention kernel implemented generators have priority of 90. The generator with the lowest priority will be used by gnutls. This function should be called before `gnutls_global_init()'. For simplicity you can use the convenience `gnutls_crypto_rnd_register()' macro. *Returns:* `GNUTLS_E_SUCCESS' on success, otherwise an error. *Since:* 2.6.0 gnutls_crypto_single_cipher_register2 ------------------------------------- -- Function: int gnutls_crypto_single_cipher_register2 (gnutls_cipher_algorithm_t ALGORITHM, int PRIORITY, int VERSION, const gnutls_crypto_cipher_st * S) ALGORITHM: is the gnutls algorithm identifier PRIORITY: is the priority of the algorithm VERSION: should be set to `GNUTLS_CRYPTO_API_VERSION' S: is a structure holding new cipher's data This function will register a cipher algorithm to be used by gnutls. Any algorithm registered will override the included algorithms and by convention kernel implemented algorithms have priority of 90. The algorithm with the lowest priority will be used by gnutls. This function should be called before `gnutls_global_init()'. For simplicity you can use the convenience `gnutls_crypto_single_cipher_register()' macro. *Returns:* `GNUTLS_E_SUCCESS' on success, otherwise an error. *Since:* 2.6.0 gnutls_crypto_single_digest_register2 ------------------------------------- -- Function: int gnutls_crypto_single_digest_register2 (gnutls_digest_algorithm_t ALGORITHM, int PRIORITY, int VERSION, const gnutls_crypto_digest_st * S) ALGORITHM: is the gnutls algorithm identifier PRIORITY: is the priority of the algorithm VERSION: should be set to `GNUTLS_CRYPTO_API_VERSION' S: is a structure holding new algorithms's data This function will register a digest (hash) algorithm to be used by gnutls. Any algorithm registered will override the included algorithms and by convention kernel implemented algorithms have priority of 90. The algorithm with the lowest priority will be used by gnutls. This function should be called before `gnutls_global_init()'. For simplicity you can use the convenience `gnutls_crypto_single_digest_register()' macro. *Returns:* `GNUTLS_E_SUCCESS' on success, otherwise an error. *Since:* 2.6.0 gnutls_crypto_single_mac_register2 ---------------------------------- -- Function: int gnutls_crypto_single_mac_register2 (gnutls_mac_algorithm_t ALGORITHM, int PRIORITY, int VERSION, const gnutls_crypto_mac_st * S) ALGORITHM: is the gnutls algorithm identifier PRIORITY: is the priority of the algorithm VERSION: should be set to `GNUTLS_CRYPTO_API_VERSION' S: is a structure holding new algorithms's data This function will register a MAC algorithm to be used by gnutls. Any algorithm registered will override the included algorithms and by convention kernel implemented algorithms have priority of 90. The algorithm with the lowest priority will be used by gnutls. This function should be called before `gnutls_global_init()'. For simplicity you can use the convenience `gnutls_crypto_single_mac_register()' macro. *Returns:* `GNUTLS_E_SUCCESS' on success, otherwise an error. *Since:* 2.6.0 gnutls_db_check_entry --------------------- -- Function: int gnutls_db_check_entry (gnutls_session_t SESSION, gnutls_datum_t SESSION_ENTRY) SESSION: is a `gnutls_session_t' structure. SESSION_ENTRY: is the session data (not key) Check if database entry has expired. This function is to be used when you want to clear unnesessary session which occupy space in your backend. *Returns:* Returns `GNUTLS_E_EXPIRED', if the database entry has expired or 0 otherwise. gnutls_db_get_ptr ----------------- -- Function: void * gnutls_db_get_ptr (gnutls_session_t SESSION) SESSION: is a `gnutls_session_t' structure. Get db function pointer. *Returns:* the pointer that will be sent to db store, retrieve and delete functions, as the first argument. gnutls_db_remove_session ------------------------ -- Function: void gnutls_db_remove_session (gnutls_session_t SESSION) SESSION: is a `gnutls_session_t' structure. This function will remove the current session data from the session database. This will prevent future handshakes reusing these session data. This function should be called if a session was terminated abnormally, and before `gnutls_deinit()' is called. Normally `gnutls_deinit()' will remove abnormally terminated sessions. gnutls_db_set_cache_expiration ------------------------------ -- Function: void gnutls_db_set_cache_expiration (gnutls_session_t SESSION, int SECONDS) SESSION: is a `gnutls_session_t' structure. SECONDS: is the number of seconds. Set the expiration time for resumed sessions. The default is 3600 (one hour) at the time writing this. gnutls_db_set_ptr ----------------- -- Function: void gnutls_db_set_ptr (gnutls_session_t SESSION, void * PTR) SESSION: is a `gnutls_session_t' structure. PTR: is the pointer Sets the pointer that will be provided to db store, retrieve and delete functions, as the first argument. gnutls_db_set_remove_function ----------------------------- -- Function: void gnutls_db_set_remove_function (gnutls_session_t SESSION, gnutls_db_remove_func REM_FUNC) SESSION: is a `gnutls_session_t' structure. REM_FUNC: is the function. Sets the function that will be used to remove data from the resumed sessions database. This function must return 0 on success. The first argument to `rem_func' will be null unless `gnutls_db_set_ptr()' has been called. gnutls_db_set_retrieve_function ------------------------------- -- Function: void gnutls_db_set_retrieve_function (gnutls_session_t SESSION, gnutls_db_retr_func RETR_FUNC) SESSION: is a `gnutls_session_t' structure. RETR_FUNC: is the function. Sets the function that will be used to retrieve data from the resumed sessions database. This function must return a gnutls_datum_t containing the data on success, or a gnutls_datum_t containing null and 0 on failure. The datum's data must be allocated using the function `gnutls_malloc()'. The first argument to `retr_func' will be null unless `gnutls_db_set_ptr()' has been called. gnutls_db_set_store_function ---------------------------- -- Function: void gnutls_db_set_store_function (gnutls_session_t SESSION, gnutls_db_store_func STORE_FUNC) SESSION: is a `gnutls_session_t' structure. STORE_FUNC: is the function Sets the function that will be used to store data from the resumed sessions database. This function must remove 0 on success. The first argument to `store_func()' will be null unless `gnutls_db_set_ptr()' has been called. gnutls_deinit ------------- -- Function: void gnutls_deinit (gnutls_session_t SESSION) SESSION: is a `gnutls_session_t' structure. This function clears all buffers associated with the `session'. This function will also remove session data from the session database if the session was terminated abnormally. gnutls_dh_get_group ------------------- -- Function: int gnutls_dh_get_group (gnutls_session_t SESSION, gnutls_datum_t * RAW_GEN, gnutls_datum_t * RAW_PRIME) SESSION: is a gnutls session RAW_GEN: will hold the generator. RAW_PRIME: will hold the prime. This function will return the group parameters used in the last Diffie-Hellman key exchange with the peer. These are the prime and the generator used. This function should be used for both anonymous and ephemeral Diffie-Hellman. The output parameters must be freed with `gnutls_free()'. *Returns:* On success, `GNUTLS_E_SUCCESS' (0) is returned, otherwise an error code is returned. gnutls_dh_get_peers_public_bits ------------------------------- -- Function: int gnutls_dh_get_peers_public_bits (gnutls_session_t SESSION) SESSION: is a gnutls session Get the Diffie-Hellman public key bit size. Can be used for both anonymous and ephemeral Diffie-Hellman. *Returns:* the public key bit size used in the last Diffie-Hellman key exchange with the peer, or a negative value in case of error. gnutls_dh_get_prime_bits ------------------------ -- Function: int gnutls_dh_get_prime_bits (gnutls_session_t SESSION) SESSION: is a gnutls session This function will return the bits of the prime used in the last Diffie-Hellman key exchange with the peer. Should be used for both anonymous and ephemeral Diffie-Hellman. Note that some ciphers, like RSA and DSA without DHE, does not use a Diffie-Hellman key exchange, and then this function will return 0. *Returns:* The Diffie-Hellman bit strength is returned, or 0 if no Diffie-Hellman key exchange was done, or a negative error code on failure. gnutls_dh_get_pubkey -------------------- -- Function: int gnutls_dh_get_pubkey (gnutls_session_t SESSION, gnutls_datum_t * RAW_KEY) SESSION: is a gnutls session RAW_KEY: will hold the public key. This function will return the peer's public key used in the last Diffie-Hellman key exchange. This function should be used for both anonymous and ephemeral Diffie-Hellman. The output parameters must be freed with `gnutls_free()'. *Returns:* On success, `GNUTLS_E_SUCCESS' (0) is returned, otherwise an error code is returned. gnutls_dh_get_secret_bits ------------------------- -- Function: int gnutls_dh_get_secret_bits (gnutls_session_t SESSION) SESSION: is a gnutls session This function will return the bits used in the last Diffie-Hellman key exchange with the peer. Should be used for both anonymous and ephemeral Diffie-Hellman. *Returns:* On success, `GNUTLS_E_SUCCESS' (0) is returned, otherwise an error code is returned. gnutls_dh_params_cpy -------------------- -- Function: int gnutls_dh_params_cpy (gnutls_dh_params_t DST, gnutls_dh_params_t SRC) DST: Is the destination structure, which should be initialized. SRC: Is the source structure This function will copy the DH parameters structure from source to destination. *Returns:* On success, `GNUTLS_E_SUCCESS' (zero) is returned, otherwise an error code is returned. gnutls_dh_params_deinit ----------------------- -- Function: void gnutls_dh_params_deinit (gnutls_dh_params_t DH_PARAMS) DH_PARAMS: Is a structure that holds the prime numbers This function will deinitialize the DH parameters structure. gnutls_dh_params_export_pkcs3 ----------------------------- -- Function: int gnutls_dh_params_export_pkcs3 (gnutls_dh_params_t PARAMS, gnutls_x509_crt_fmt_t FORMAT, unsigned char * PARAMS_DATA, size_t * PARAMS_DATA_SIZE) PARAMS: Holds the DH parameters FORMAT: the format of output params. One of PEM or DER. PARAMS_DATA: will contain a PKCS3 DHParams structure PEM or DER encoded PARAMS_DATA_SIZE: holds the size of params_data (and will be replaced by the actual size of parameters) This function will export the given dh parameters to a PKCS3 DHParams structure. This is the format generated by "openssl dhparam" tool. If the buffer provided is not long enough to hold the output, then GNUTLS_E_SHORT_MEMORY_BUFFER will be returned. If the structure is PEM encoded, it will have a header of "BEGIN DH PARAMETERS". *Returns:* On success, `GNUTLS_E_SUCCESS' (zero) is returned, otherwise an error code is returned. gnutls_dh_params_export_raw --------------------------- -- Function: int gnutls_dh_params_export_raw (gnutls_dh_params_t PARAMS, gnutls_datum_t * PRIME, gnutls_datum_t * GENERATOR, unsigned int * BITS) PARAMS: Holds the DH parameters PRIME: will hold the new prime GENERATOR: will hold the new generator BITS: if non null will hold is the prime's number of bits This function will export the pair of prime and generator for use in the Diffie-Hellman key exchange. The new parameters will be allocated using `gnutls_malloc()' and will be stored in the appropriate datum. *Returns:* On success, `GNUTLS_E_SUCCESS' (zero) is returned, otherwise an error code is returned. gnutls_dh_params_generate2 -------------------------- -- Function: int gnutls_dh_params_generate2 (gnutls_dh_params_t PARAMS, unsigned int BITS) PARAMS: Is the structure that the DH parameters will be stored BITS: is the prime's number of bits This function will generate a new pair of prime and generator for use in the Diffie-Hellman key exchange. The new parameters will be allocated using `gnutls_malloc()' and will be stored in the appropriate datum. This function is normally slow. Do not set the number of bits directly, use `gnutls_sec_param_to_pk_bits()' to get bits for `GNUTLS_PK_DSA'. Also note that the DH parameters are only useful to servers. Since clients use the parameters sent by the server, it's of no use to call this in client side. *Returns:* On success, `GNUTLS_E_SUCCESS' (zero) is returned, otherwise an error code is returned. gnutls_dh_params_import_pkcs3 ----------------------------- -- Function: int gnutls_dh_params_import_pkcs3 (gnutls_dh_params_t PARAMS, const gnutls_datum_t * PKCS3_PARAMS, gnutls_x509_crt_fmt_t FORMAT) PARAMS: A structure where the parameters will be copied to PKCS3_PARAMS: should contain a PKCS3 DHParams structure PEM or DER encoded FORMAT: the format of params. PEM or DER. This function will extract the DHParams found in a PKCS3 formatted structure. This is the format generated by "openssl dhparam" tool. If the structure is PEM encoded, it should have a header of "BEGIN DH PARAMETERS". *Returns:* On success, `GNUTLS_E_SUCCESS' (zero) is returned, otherwise an error code is returned. gnutls_dh_params_import_raw --------------------------- -- Function: int gnutls_dh_params_import_raw (gnutls_dh_params_t DH_PARAMS, const gnutls_datum_t * PRIME, const gnutls_datum_t * GENERATOR) DH_PARAMS: Is a structure that will hold the prime numbers PRIME: holds the new prime GENERATOR: holds the new generator This function will replace the pair of prime and generator for use in the Diffie-Hellman key exchange. The new parameters should be stored in the appropriate gnutls_datum. *Returns:* On success, `GNUTLS_E_SUCCESS' (zero) is returned, otherwise an error code is returned. gnutls_dh_params_init --------------------- -- Function: int gnutls_dh_params_init (gnutls_dh_params_t * DH_PARAMS) DH_PARAMS: Is a structure that will hold the prime numbers This function will initialize the DH parameters structure. *Returns:* On success, `GNUTLS_E_SUCCESS' (zero) is returned, otherwise an error code is returned. gnutls_dh_set_prime_bits ------------------------ -- Function: void gnutls_dh_set_prime_bits (gnutls_session_t SESSION, unsigned int BITS) SESSION: is a `gnutls_session_t' structure. BITS: is the number of bits This function sets the number of bits, for use in an Diffie-Hellman key exchange. This is used both in DH ephemeral and DH anonymous cipher suites. This will set the minimum size of the prime that will be used for the handshake. In the client side it sets the minimum accepted number of bits. If a server sends a prime with less bits than that `GNUTLS_E_DH_PRIME_UNACCEPTABLE' will be returned by the handshake. This function has no effect in server side. gnutls_error_is_fatal --------------------- -- Function: int gnutls_error_is_fatal (int ERROR) ERROR: is a GnuTLS error code, a negative value If a GnuTLS function returns a negative value you may feed that value to this function to see if the error condition is fatal. Note that you may want to check the error code manually, since some non-fatal errors to the protocol may be fatal for you program. This function is only useful if you are dealing with errors from the record layer or the handshake layer. *Returns:* 1 if the error code is fatal, for positive `error' values, 0 is returned. For unknown `error' values, -1 is returned. gnutls_error_to_alert --------------------- -- Function: int gnutls_error_to_alert (int ERR, int * LEVEL) ERR: is a negative integer LEVEL: the alert level will be stored there Get an alert depending on the error code returned by a gnutls function. All alerts sent by this function should be considered fatal. The only exception is when `err' is `GNUTLS_E_REHANDSHAKE', where a warning alert should be sent to the peer indicating that no renegotiation will be performed. If there is no mapping to a valid alert the alert to indicate internal error is returned. *Returns:* the alert code to use for a particular error code. gnutls_ext_register ------------------- -- Function: int gnutls_ext_register (int TYPE, const char * NAME, gnutls_ext_parse_type_t PARSE_TYPE, gnutls_ext_recv_func RECV_FUNC, gnutls_ext_send_func SEND_FUNC) TYPE: the 16-bit integer referring to the extension type NAME: human printable name of the extension used for debugging PARSE_TYPE: either `GNUTLS_EXT_TLS' or `GNUTLS_EXT_APPLICATION'. RECV_FUNC: a function to receive extension data SEND_FUNC: a function to send extension data This function is used to register a new TLS extension handler. *Returns:* `GNUTLS_E_SUCCESS' on success, or an error code. *Deprecated in:* 2.12.0 gnutls_fingerprint ------------------ -- Function: int gnutls_fingerprint (gnutls_digest_algorithm_t ALGO, const gnutls_datum_t * DATA, void * RESULT, size_t * RESULT_SIZE) ALGO: is a digest algorithm DATA: is the data RESULT: is the place where the result will be copied (may be null). RESULT_SIZE: should hold the size of the result. The actual size of the returned result will also be copied there. This function will calculate a fingerprint (actually a hash), of the given data. The result is not printable data. You should convert it to hex, or to something else printable. This is the usual way to calculate a fingerprint of an X.509 DER encoded certificate. Note however that the fingerprint of an OpenPGP is not just a hash and cannot be calculated with this function. *Returns:* On success, `GNUTLS_E_SUCCESS' (0) is returned, otherwise an error code is returned. gnutls_free ----------- -- Function: void gnutls_free (void * PTR) This function will free data pointed by ptr. The deallocation function used is the one set by `gnutls_global_set_mem_functions()'. gnutls_global_deinit -------------------- -- Function: void gnutls_global_deinit ( VOID) This function deinitializes the global data, that were initialized using `gnutls_global_init()'. Note! This function is not thread safe. See the discussion for `gnutls_global_init()' for more information. gnutls_global_init ------------------ -- Function: int gnutls_global_init ( VOID) This function initializes the global data to defaults. Every gnutls application has a global data which holds common parameters shared by gnutls session structures. You should call `gnutls_global_deinit()' when gnutls usage is no longer needed Note that this function will also initialize the underlying crypto backend, if it has not been initialized before. This function increment a global counter, so that `gnutls_global_deinit()' only releases resources when it has been called as many times as `gnutls_global_init()'. This is useful when GnuTLS is used by more than one library in an application. This function can be called many times, but will only do something the first time. Note! This function is not thread safe. If two threads call this function simultaneously, they can cause a race between checking the global counter and incrementing it, causing both threads to execute the library initialization code. That would lead to a memory leak. To handle this, your application could invoke this function after aquiring a thread mutex. To ignore the potential memory leak is also an option. *Returns:* On success, `GNUTLS_E_SUCCESS' (zero) is returned, otherwise an error code is returned. gnutls_global_set_log_function ------------------------------ -- Function: void gnutls_global_set_log_function (gnutls_log_func LOG_FUNC) LOG_FUNC: it's a log function This is the function where you set the logging function gnutls is going to use. This function only accepts a character array. Normally you may not use this function since it is only used for debugging purposes. gnutls_log_func is of the form, void (*gnutls_log_func)( int level, const char*); gnutls_global_set_log_level --------------------------- -- Function: void gnutls_global_set_log_level (int LEVEL) LEVEL: it's an integer from 0 to 9. This is the function that allows you to set the log level. The level is an integer between 0 and 9. Higher values mean more verbosity. The default value is 0. Larger values should only be used with care, since they may reveal sensitive information. Use a log level over 10 to enable all debugging options. gnutls_global_set_mem_functions ------------------------------- -- Function: void gnutls_global_set_mem_functions (gnutls_alloc_function ALLOC_FUNC, gnutls_alloc_function SECURE_ALLOC_FUNC, gnutls_is_secure_function IS_SECURE_FUNC, gnutls_realloc_function REALLOC_FUNC, gnutls_free_function FREE_FUNC) ALLOC_FUNC: it's the default memory allocation function. Like `malloc()'. SECURE_ALLOC_FUNC: This is the memory allocation function that will be used for sensitive data. IS_SECURE_FUNC: a function that returns 0 if the memory given is not secure. May be NULL. REALLOC_FUNC: A realloc function FREE_FUNC: The function that frees allocated data. Must accept a NULL pointer. This is the function were you set the memory allocation functions gnutls is going to use. By default the libc's allocation functions (`malloc()', `free()'), are used by gnutls, to allocate both sensitive and not sensitive data. This function is provided to set the memory allocation functions to something other than the defaults This function must be called before `gnutls_global_init()' is called. This function is not thread safe. gnutls_global_set_mutex ----------------------- -- Function: void gnutls_global_set_mutex (mutex_init_func INIT, mutex_deinit_func DEINIT, mutex_lock_func LOCK, mutex_unlock_func UNLOCK) INIT: mutex initialization function DEINIT: mutex deinitialization function LOCK: mutex locking function UNLOCK: mutex unlocking function With this function you are allowed to override the default mutex locks used in some parts of gnutls and dependent libraries. This function should be used if you have complete control of your program and libraries. Do not call this function from a library. Instead only initialize gnutls and the default OS mutex locks will be used. This function must be called before `gnutls_global_init()'. gnutls_global_set_time_function ------------------------------- -- Function: void gnutls_global_set_time_function (gnutls_time_func TIME_FUNC) TIME_FUNC: it's the system time function This is the function where you can override the default system time function. gnutls_time_func is of the form, time_t (*gnutls_time_func)( time*); gnutls_handshake_get_last_in ---------------------------- -- Function: gnutls_handshake_description_t gnutls_handshake_get_last_in (gnutls_session_t SESSION) SESSION: is a `gnutls_session_t' structure. This function is only useful to check where the last performed handshake failed. If the previous handshake succeed or was not performed at all then no meaningful value will be returned. Check `gnutls_handshake_description_t' in gnutls.h for the available handshake descriptions. *Returns:* the last handshake message type received, a `gnutls_handshake_description_t'. gnutls_handshake_get_last_out ----------------------------- -- Function: gnutls_handshake_description_t gnutls_handshake_get_last_out (gnutls_session_t SESSION) SESSION: is a `gnutls_session_t' structure. This function is only useful to check where the last performed handshake failed. If the previous handshake succeed or was not performed at all then no meaningful value will be returned. Check `gnutls_handshake_description_t' in gnutls.h for the available handshake descriptions. *Returns:* the last handshake message type sent, a `gnutls_handshake_description_t'. gnutls_handshake_set_max_packet_length -------------------------------------- -- Function: void gnutls_handshake_set_max_packet_length (gnutls_session_t SESSION, size_t MAX) SESSION: is a `gnutls_session_t' structure. MAX: is the maximum number. This function will set the maximum size of all handshake messages. Handshakes over this size are rejected with `GNUTLS_E_HANDSHAKE_TOO_LARGE' error code. The default value is 48kb which is typically large enough. Set this to 0 if you do not want to set an upper limit. The reason for restricting the handshake message sizes are to limit Denial of Service attacks. gnutls_handshake_set_post_client_hello_function ----------------------------------------------- -- Function: void gnutls_handshake_set_post_client_hello_function (gnutls_session_t SESSION, gnutls_handshake_post_client_hello_func FUNC) SESSION: is a `gnutls_session_t' structure. FUNC: is the function to be called This function will set a callback to be called after the client hello has been received (callback valid in server side only). This allows the server to adjust settings based on received extensions. Those settings could be ciphersuites, requesting certificate, or anything else except for version negotiation (this is done before the hello message is parsed). This callback must return 0 on success or a gnutls error code to terminate the handshake. *Warning:* You should not use this function to terminate the handshake based on client input unless you know what you are doing. Before the handshake is finished there is no way to know if there is a man-in-the-middle attack being performed. gnutls_handshake_set_private_extensions --------------------------------------- -- Function: void gnutls_handshake_set_private_extensions (gnutls_session_t SESSION, int ALLOW) SESSION: is a `gnutls_session_t' structure. ALLOW: is an integer (0 or 1) This function will enable or disable the use of private cipher suites (the ones that start with 0xFF). By default or if `allow' is 0 then these cipher suites will not be advertized nor used. Unless this function is called with the option to allow (1), then no compression algorithms, like LZO. That is because these algorithms are not yet defined in any RFC or even internet draft. Enabling the private ciphersuites when talking to other than gnutls servers and clients may cause interoperability problems. gnutls_handshake ---------------- -- Function: int gnutls_handshake (gnutls_session_t SESSION) SESSION: is a `gnutls_session_t' structure. This function does the handshake of the TLS/SSL protocol, and initializes the TLS connection. This function will fail if any problem is encountered, and will return a negative error code. In case of a client, if the client has asked to resume a session, but the server couldn't, then a full handshake will be performed. The non-fatal errors such as `GNUTLS_E_AGAIN' and `GNUTLS_E_INTERRUPTED' interrupt the handshake procedure, which should be later be resumed. Call this function again, until it returns 0; cf. `gnutls_record_get_direction()' and `gnutls_error_is_fatal()'. If this function is called by a server after a rehandshake request then `GNUTLS_E_GOT_APPLICATION_DATA' or `GNUTLS_E_WARNING_ALERT_RECEIVED' may be returned. Note that these are non fatal errors, only in the specific case of a rehandshake. Their meaning is that the client rejected the rehandshake request or in the case of `GNUTLS_E_GOT_APPLICATION_DATA' it might also mean that some data were pending. *Returns:* `GNUTLS_E_SUCCESS' on success, otherwise an error. gnutls_hash_deinit ------------------ -- Function: void gnutls_hash_deinit (gnutls_hash_hd_t HANDLE, void * DIGEST) HANDLE: is a `gnutls_hash_hd_t' structure. DIGEST: is the output value of the hash This function will deinitialize all resources occupied by the given hash context. *Since:* 2.10.0 gnutls_hash_fast ---------------- -- Function: int gnutls_hash_fast (gnutls_digest_algorithm_t ALGORITHM, const void * TEXT, size_t TEXTLEN, void * DIGEST) ALGORITHM: the hash algorithm to use TEXT: the data to hash TEXTLEN: The length of data to hash DIGEST: is the output value of the hash This convenience function will hash the given data and return output on a single call. *Returns:* Zero or a negative value on error. *Since:* 2.10.0 gnutls_hash_get_len ------------------- -- Function: int gnutls_hash_get_len (gnutls_digest_algorithm_t ALGORITHM) ALGORITHM: the hash algorithm to use This function will return the length of the output data of the given hash algorithm. *Returns:* The length or zero on error. *Since:* 2.10.0 gnutls_hash_init ---------------- -- Function: int gnutls_hash_init (gnutls_hash_hd_t * DIG, gnutls_digest_algorithm_t ALGORITHM) DIG: is a `gnutls_hash_hd_t' structure. ALGORITHM: the hash algorithm to use This function will initialize an context that can be used to produce a Message Digest of data. This will effectively use the current crypto backend in use by gnutls or the cryptographic accelerator in use. *Returns:* Zero or a negative value on error. *Since:* 2.10.0 gnutls_hash_output ------------------ -- Function: void gnutls_hash_output (gnutls_hash_hd_t HANDLE, void * DIGEST) HANDLE: is a `gnutls_hash_hd_t' structure. DIGEST: is the output value of the hash This function will output the current hash value. *Since:* 2.10.0 gnutls_hash ----------- -- Function: int gnutls_hash (gnutls_hash_hd_t HANDLE, const void * TEXT, size_t TEXTLEN) HANDLE: is a `gnutls_cipher_hd_t' structure. TEXT: the data to hash TEXTLEN: The length of data to hash This function will hash the given data using the algorithm specified by the context. *Returns:* Zero or a negative value on error. *Since:* 2.10.0 gnutls_hex2bin -------------- -- Function: int gnutls_hex2bin (const char * HEX_DATA, size_t HEX_SIZE, char * BIN_DATA, size_t * BIN_SIZE) HEX_DATA: string with data in hex format HEX_SIZE: size of hex data BIN_DATA: output array with binary data BIN_SIZE: when calling *`bin_size' should hold size of `bin_data', on return will hold actual size of `bin_data'. Convert a buffer with hex data to binary data. *Returns:* `GNUTLS_E_SUCCESS' on success, otherwise an error. *Since:* 2.4.0 gnutls_hex_decode ----------------- -- Function: int gnutls_hex_decode (const gnutls_datum_t * HEX_DATA, char * RESULT, size_t * RESULT_SIZE) HEX_DATA: contain the encoded data RESULT: the place where decoded data will be copied RESULT_SIZE: holds the size of the result This function will decode the given encoded data, using the hex encoding used by PSK password files. Note that hex_data should be null terminated. *Returns:* `GNUTLS_E_SHORT_MEMORY_BUFFER' if the buffer given is not long enough, or 0 on success. gnutls_hex_encode ----------------- -- Function: int gnutls_hex_encode (const gnutls_datum_t * DATA, char * RESULT, size_t * RESULT_SIZE) DATA: contain the raw data RESULT: the place where hex data will be copied RESULT_SIZE: holds the size of the result This function will convert the given data to printable data, using the hex encoding, as used in the PSK password files. *Returns:* `GNUTLS_E_SHORT_MEMORY_BUFFER' if the buffer given is not long enough, or 0 on success. gnutls_hmac_deinit ------------------ -- Function: void gnutls_hmac_deinit (gnutls_hmac_hd_t HANDLE, void * DIGEST) HANDLE: is a `gnutls_hmac_hd_t' structure. DIGEST: is the output value of the MAC This function will deinitialize all resources occupied by the given hmac context. *Since:* 2.10.0 gnutls_hmac_fast ---------------- -- Function: int gnutls_hmac_fast (gnutls_mac_algorithm_t ALGORITHM, const void * KEY, size_t KEYLEN, const void * TEXT, size_t TEXTLEN, void * DIGEST) ALGORITHM: the hash algorithm to use KEY: the key to use KEYLEN: The length of the key TEXT: the data to hash TEXTLEN: The length of data to hash DIGEST: is the output value of the hash This convenience function will hash the given data and return output on a single call. *Returns:* Zero or a negative value on error. *Since:* 2.10.0 gnutls_hmac_get_len ------------------- -- Function: int gnutls_hmac_get_len (gnutls_mac_algorithm_t ALGORITHM) ALGORITHM: the hmac algorithm to use This function will return the length of the output data of the given hmac algorithm. *Returns:* The length or zero on error. *Since:* 2.10.0 gnutls_hmac_init ---------------- -- Function: int gnutls_hmac_init (gnutls_hmac_hd_t * DIG, gnutls_digest_algorithm_t ALGORITHM, const void * KEY, size_t KEYLEN) DIG: is a `gnutls_hmac_hd_t' structure. ALGORITHM: the HMAC algorithm to use KEY: The key to be used for encryption KEYLEN: The length of the key This function will initialize an context that can be used to produce a Message Authentication Code (MAC) of data. This will effectively use the current crypto backend in use by gnutls or the cryptographic accelerator in use. *Returns:* Zero or a negative value on error. *Since:* 2.10.0 gnutls_hmac_output ------------------ -- Function: void gnutls_hmac_output (gnutls_hmac_hd_t HANDLE, void * DIGEST) HANDLE: is a `gnutls_hmac_hd_t' structure. DIGEST: is the output value of the MAC This function will output the current MAC value. *Since:* 2.10.0 gnutls_hmac ----------- -- Function: int gnutls_hmac (gnutls_hmac_hd_t HANDLE, const void * TEXT, size_t TEXTLEN) HANDLE: is a `gnutls_cipher_hd_t' structure. TEXT: the data to hash TEXTLEN: The length of data to hash This function will hash the given data using the algorithm specified by the context. *Returns:* Zero or a negative value on error. *Since:* 2.10.0 gnutls_init ----------- -- Function: int gnutls_init (gnutls_session_t * SESSION, gnutls_connection_end_t CON_END) SESSION: is a pointer to a `gnutls_session_t' structure. CON_END: indicate if this session is to be used for server or client. This function initializes the current session to null. Every session must be initialized before use, so internal structures can be allocated. This function allocates structures which can only be free'd by calling `gnutls_deinit()'. Returns zero on success. `con_end' can be one of `GNUTLS_CLIENT' and `GNUTLS_SERVER'. *Returns:* `GNUTLS_E_SUCCESS' on success, or an error code. gnutls_kx_get_id ---------------- -- Function: gnutls_kx_algorithm_t gnutls_kx_get_id (const char * NAME) NAME: is a KX name Convert a string to a `gnutls_kx_algorithm_t' value. The names are compared in a case insensitive way. *Returns:* an id of the specified KX algorithm, or `GNUTLS_KX_UNKNOWN' on error. gnutls_kx_get_name ------------------ -- Function: const char * gnutls_kx_get_name (gnutls_kx_algorithm_t ALGORITHM) ALGORITHM: is a key exchange algorithm Convert a `gnutls_kx_algorithm_t' value to a string. *Returns:* a pointer to a string that contains the name of the specified key exchange algorithm, or `NULL'. gnutls_kx_get ------------- -- Function: gnutls_kx_algorithm_t gnutls_kx_get (gnutls_session_t SESSION) SESSION: is a `gnutls_session_t' structure. Get currently used key exchange algorithm. *Returns:* the key exchange algorithm used in the last handshake, a `gnutls_kx_algorithm_t' value. gnutls_kx_list -------------- -- Function: const gnutls_kx_algorithm_t * gnutls_kx_list ( VOID) Get a list of supported key exchange algorithms. *Returns:* a zero-terminated list of `gnutls_kx_algorithm_t' integers indicating the available key exchange algorithms. gnutls_kx_set_priority ---------------------- -- Function: int gnutls_kx_set_priority (gnutls_session_t SESSION, const int * LIST) SESSION: is a `gnutls_session_t' structure. LIST: is a 0 terminated list of gnutls_kx_algorithm_t elements. Sets the priority on the key exchange algorithms supported by gnutls. Priority is higher for elements specified before others. After specifying the algorithms you want, you must append a 0. Note that the priority is set on the client. The server does not use the algorithm's priority except for disabling algorithms that were not specified. *Returns:* `GNUTLS_E_SUCCESS' on success, or an error code. gnutls_mac_get_id ----------------- -- Function: gnutls_mac_algorithm_t gnutls_mac_get_id (const char * NAME) NAME: is a MAC algorithm name Convert a string to a `gnutls_mac_algorithm_t' value. The names are compared in a case insensitive way. *Returns:* a `gnutls_mac_algorithm_t' id of the specified MAC algorithm string, or `GNUTLS_MAC_UNKNOWN' on failures. gnutls_mac_get_key_size ----------------------- -- Function: size_t gnutls_mac_get_key_size (gnutls_mac_algorithm_t ALGORITHM) ALGORITHM: is an encryption algorithm Get size of MAC key. *Returns:* length (in bytes) of the given MAC key size, or 0 if the given MAC algorithm is invalid. gnutls_mac_get_name ------------------- -- Function: const char * gnutls_mac_get_name (gnutls_mac_algorithm_t ALGORITHM) ALGORITHM: is a MAC algorithm Convert a `gnutls_mac_algorithm_t' value to a string. *Returns:* a string that contains the name of the specified MAC algorithm, or `NULL'. gnutls_mac_get -------------- -- Function: gnutls_mac_algorithm_t gnutls_mac_get (gnutls_session_t SESSION) SESSION: is a `gnutls_session_t' structure. Get currently used MAC algorithm. *Returns:* the currently used mac algorithm, a `gnutls_mac_algorithm_t' value. gnutls_mac_list --------------- -- Function: const gnutls_mac_algorithm_t * gnutls_mac_list ( VOID) Get a list of hash algorithms for use as MACs. Note that not necessarily all MACs are supported in TLS cipher suites. For example, MD2 is not supported as a cipher suite, but is supported for other purposes (e.g., X.509 signature verification or similar). *Returns:* Return a zero-terminated list of `gnutls_mac_algorithm_t' integers indicating the available MACs. gnutls_mac_set_priority ----------------------- -- Function: int gnutls_mac_set_priority (gnutls_session_t SESSION, const int * LIST) SESSION: is a `gnutls_session_t' structure. LIST: is a 0 terminated list of gnutls_mac_algorithm_t elements. Sets the priority on the mac algorithms supported by gnutls. Priority is higher for elements specified before others. After specifying the algorithms you want, you must append a 0. Note that the priority is set on the client. The server does not use the algorithm's priority except for disabling algorithms that were not specified. *Returns:* `GNUTLS_E_SUCCESS' on success, or an error code. gnutls_malloc ------------- -- Function: void * gnutls_malloc (size_t S) This function will allocate 's' bytes data, and return a pointer to memory. This function is supposed to be used by callbacks. The allocation function used is the one set by `gnutls_global_set_mem_functions()'. gnutls_openpgp_send_cert ------------------------ -- Function: void gnutls_openpgp_send_cert (gnutls_session_t SESSION, gnutls_openpgp_crt_status_t STATUS) SESSION: is a pointer to a `gnutls_session_t' structure. STATUS: is one of GNUTLS_OPENPGP_CERT, or GNUTLS_OPENPGP_CERT_FINGERPRINT This function will order gnutls to send the key fingerprint instead of the key in the initial handshake procedure. This should be used with care and only when there is indication or knowledge that the server can obtain the client's key. gnutls_pem_base64_decode_alloc ------------------------------ -- Function: int gnutls_pem_base64_decode_alloc (const char * HEADER, const gnutls_datum_t * B64_DATA, gnutls_datum_t * RESULT) HEADER: The PEM header (eg. CERTIFICATE) B64_DATA: contains the encoded data RESULT: the place where decoded data lie This function will decode the given encoded data. The decoded data will be allocated, and stored into result. If the header given is non null this function will search for "----BEGIN header" and decode only this part. Otherwise it will decode the first PEM packet found. You should use `gnutls_free()' to free the returned data. *Returns:* On success, `GNUTLS_E_SUCCESS' (0) is returned, otherwise an error code is returned. gnutls_pem_base64_decode ------------------------ -- Function: int gnutls_pem_base64_decode (const char * HEADER, const gnutls_datum_t * B64_DATA, unsigned char * RESULT, size_t * RESULT_SIZE) HEADER: A null terminated string with the PEM header (eg. CERTIFICATE) B64_DATA: contain the encoded data RESULT: the place where decoded data will be copied RESULT_SIZE: holds the size of the result This function will decode the given encoded data. If the header given is non null this function will search for "----BEGIN header" and decode only this part. Otherwise it will decode the first PEM packet found. *Returns:* On success `GNUTLS_E_SUCCESS' (0) is returned, `GNUTLS_E_SHORT_MEMORY_BUFFER' is returned if the buffer given is not long enough, or 0 on success. gnutls_pem_base64_encode_alloc ------------------------------ -- Function: int gnutls_pem_base64_encode_alloc (const char * MSG, const gnutls_datum_t * DATA, gnutls_datum_t * RESULT) MSG: is a message to be put in the encoded header DATA: contains the raw data RESULT: will hold the newly allocated encoded data This function will convert the given data to printable data, using the base64 encoding. This is the encoding used in PEM messages. This function will allocate the required memory to hold the encoded data. You should use `gnutls_free()' to free the returned data. *Returns:* On success, `GNUTLS_E_SUCCESS' (0) is returned, otherwise an error code is returned. gnutls_pem_base64_encode ------------------------ -- Function: int gnutls_pem_base64_encode (const char * MSG, const gnutls_datum_t * DATA, char * RESULT, size_t * RESULT_SIZE) MSG: is a message to be put in the header DATA: contain the raw data RESULT: the place where base64 data will be copied RESULT_SIZE: holds the size of the result This function will convert the given data to printable data, using the base64 encoding. This is the encoding used in PEM messages. The output string will be null terminated, although the size will not include the terminating null. *Returns:* On success `GNUTLS_E_SUCCESS' (0) is returned, `GNUTLS_E_SHORT_MEMORY_BUFFER' is returned if the buffer given is not long enough, or 0 on success. gnutls_perror ------------- -- Function: void gnutls_perror (int ERROR) ERROR: is a GnuTLS error code, a negative value This function is like `perror()'. The only difference is that it accepts an error number returned by a gnutls function. gnutls_pk_algorithm_get_name ---------------------------- -- Function: const char * gnutls_pk_algorithm_get_name (gnutls_pk_algorithm_t ALGORITHM) ALGORITHM: is a pk algorithm Convert a `gnutls_pk_algorithm_t' value to a string. *Returns:* a string that contains the name of the specified public key algorithm, or `NULL'. gnutls_pk_bits_to_sec_param --------------------------- -- Function: gnutls_sec_param_t gnutls_pk_bits_to_sec_param (gnutls_pk_algorithm_t ALGO, unsigned int BITS) ALGO: is a public key algorithm BITS: is the number of bits This is the inverse of `gnutls_sec_param_to_pk_bits()'. Given an algorithm and the number of bits, it will return the security parameter. This is a rough indication. *Returns:* The security parameter. gnutls_pk_get_id ---------------- -- Function: gnutls_pk_algorithm_t gnutls_pk_get_id (const char * NAME) NAME: is a string containing a public key algorithm name. Convert a string to a `gnutls_pk_algorithm_t' value. The names are compared in a case insensitive way. For example, gnutls_pk_get_id("RSA") will return `GNUTLS_PK_RSA'. *Returns:* a `gnutls_pk_algorithm_t' id of the specified public key algorithm string, or `GNUTLS_PK_UNKNOWN' on failures. *Since:* 2.6.0 gnutls_pk_get_name ------------------ -- Function: const char * gnutls_pk_get_name (gnutls_pk_algorithm_t ALGORITHM) ALGORITHM: is a public key algorithm Convert a `gnutls_pk_algorithm_t' value to a string. *Returns:* a pointer to a string that contains the name of the specified public key algorithm, or `NULL'. *Since:* 2.6.0 gnutls_pk_list -------------- -- Function: const gnutls_pk_algorithm_t * gnutls_pk_list ( VOID) Get a list of supported public key algorithms. *Returns:* a zero-terminated list of `gnutls_pk_algorithm_t' integers indicating the available ciphers. *Since:* 2.6.0 gnutls_pkcs11_add_provider -------------------------- -- Function: int gnutls_pkcs11_add_provider (const char * NAME, const char * PARAMS) NAME: The filename of the module PARAMS: should be NULL This function will load and add a PKCS 11 module to the module list used in gnutls. After this function is called the module will be used for PKCS 11 operations. *Returns:* On success, `GNUTLS_E_SUCCESS' is returned, otherwise a negative error value. gnutls_pkcs11_copy_secret_key ----------------------------- -- Function: int gnutls_pkcs11_copy_secret_key (const char * TOKEN_URL, gnutls_datum_t * KEY, const char * LABEL, unsigned int KEY_USAGE, unsigned int FLAGS) TOKEN_URL: A PKCS `11' URL specifying a token KEY: The raw key LABEL: A name to be used for the stored data KEY_USAGE: One of GNUTLS_KEY_* FLAGS: One of GNUTLS_PKCS11_OBJ_FLAG_* This function will copy a raw secret (symmetric) key into a PKCS `11' token specified by a URL. The key can be marked as sensitive or not. *Returns:* On success, `GNUTLS_E_SUCCESS' is returned, otherwise a negative error value. gnutls_pkcs11_copy_x509_crt --------------------------- -- Function: int gnutls_pkcs11_copy_x509_crt (const char * TOKEN_URL, gnutls_x509_crt_t CRT, const char * LABEL, unsigned int FLAGS) TOKEN_URL: A PKCS `11' URL specifying a token CRT: A certificate LABEL: A name to be used for the stored data FLAGS: One of GNUTLS_PKCS11_OBJ_FLAG_* This function will copy a certificate into a PKCS `11' token specified by a URL. The certificate can be marked as trusted or not. *Returns:* On success, `GNUTLS_E_SUCCESS' is returned, otherwise a negative error value. gnutls_pkcs11_copy_x509_privkey ------------------------------- -- Function: int gnutls_pkcs11_copy_x509_privkey (const char * TOKEN_URL, gnutls_x509_privkey_t KEY, const char * LABEL, unsigned int KEY_USAGE, unsigned int FLAGS) TOKEN_URL: A PKCS `11' URL specifying a token KEY: A private key LABEL: A name to be used for the stored data KEY_USAGE: One of GNUTLS_KEY_* FLAGS: One of GNUTLS_PKCS11_OBJ_* flags This function will copy a private key into a PKCS `11' token specified by a URL. It is highly recommended flags to contain `GNUTLS_PKCS11_OBJ_FLAG_MARK_SENSITIVE' unless there is a strong reason not to. *Returns:* On success, `GNUTLS_E_SUCCESS' is returned, otherwise a negative error value. gnutls_pkcs11_deinit -------------------- -- Function: void gnutls_pkcs11_deinit ( VOID) This function will deinitialize the PKCS 11 subsystem in gnutls. gnutls_pkcs11_delete_url ------------------------ -- Function: int gnutls_pkcs11_delete_url (const char * OBJECT_URL, unsigned int FLAGS) OBJECT_URL: The URL of the object to delete. FLAGS: One of GNUTLS_PKCS11_OBJ_* flags This function will delete objects matching the given URL. *Returns:* On success, the number of objects deleted is returned, otherwise a negative error value. gnutls_pkcs11_init ------------------ -- Function: int gnutls_pkcs11_init (unsigned int FLAGS, const char * DEPRECATED_CONFIG_FILE) FLAGS: `GNUTLS_PKCS11_FLAG_MANUAL' or `GNUTLS_PKCS11_FLAG_AUTO' DEPRECATED_CONFIG_FILE: either NULL or the location of a deprecated configuration file This function will initialize the PKCS 11 subsystem in gnutls. It will read configuration files if `GNUTLS_PKCS11_FLAG_AUTO' is used or allow you to independently load PKCS 11 modules using `gnutls_pkcs11_add_provider()' if `GNUTLS_PKCS11_FLAG_MANUAL' is specified. Using a custom configfile is deprecated and will not be supported in future versions of gnutls. Normally you don't need to call this function since it is being called by `gnutls_global_init()' using the `GNUTLS_PKCS11_FLAG_AUTO'. If you need to call this function, you must call it before `gnutls_global_init()'. *Returns:* On success, `GNUTLS_E_SUCCESS' is returned, otherwise a negative error value. gnutls_pkcs11_obj_deinit ------------------------ -- Function: void gnutls_pkcs11_obj_deinit (gnutls_pkcs11_obj_t OBJ) OBJ: The structure to be initialized This function will deinitialize a certificate structure. gnutls_pkcs11_obj_export_url ---------------------------- -- Function: int gnutls_pkcs11_obj_export_url (gnutls_pkcs11_obj_t OBJ, gnutls_pkcs11_url_type_t DETAILED, char ** URL) OBJ: Holds the PKCS 11 certificate DETAILED: non zero if a detailed URL is required URL: will contain an allocated url This function will export a URL identifying the given certificate. *Returns:* On success, `GNUTLS_E_SUCCESS' is returned, otherwise a negative error value. gnutls_pkcs11_obj_export ------------------------ -- Function: int gnutls_pkcs11_obj_export (gnutls_pkcs11_obj_t OBJ, void * OUTPUT_DATA, size_t * OUTPUT_DATA_SIZE) OBJ: Holds the object OUTPUT_DATA: will contain a certificate PEM or DER encoded OUTPUT_DATA_SIZE: holds the size of output_data (and will be replaced by the actual size of parameters) This function will export the pkcs11 object data. It is normal for PKCS `11' data to be inaccesible and in that case `GNUTLS_E_INVALID_REQUEST' will be returned. If the buffer provided is not long enough to hold the output, then *output_data_size is updated and GNUTLS_E_SHORT_MEMORY_BUFFER will be returned. If the structure is PEM encoded, it will have a header of "BEGIN CERTIFICATE". *Return value:* In case of failure a negative value will be returned, and 0 on success. gnutls_pkcs11_obj_get_info -------------------------- -- Function: int gnutls_pkcs11_obj_get_info (gnutls_pkcs11_obj_t CRT, gnutls_pkcs11_obj_info_t ITYPE, void * OUTPUT, size_t * OUTPUT_SIZE) CRT: should contain a `gnutls_pkcs11_obj_t' structure ITYPE: Denotes the type of information requested OUTPUT: where output will be stored OUTPUT_SIZE: contains the maximum size of the output and will be overwritten with actual This function will return information about the PKCS 11 certificatesuch as the label, id as well as token information where the key is stored. When output is text it returns null terminated string although `output_size' contains the size of the actual data only. *Returns:* zero on success or a negative value on error. gnutls_pkcs11_obj_get_type -------------------------- -- Function: gnutls_pkcs11_obj_type_t gnutls_pkcs11_obj_get_type (gnutls_pkcs11_obj_t OBJ) This function will return the type of the certificate being stored in the structure. *Returns:* The type of the certificate. gnutls_pkcs11_obj_import_url ---------------------------- -- Function: int gnutls_pkcs11_obj_import_url (gnutls_pkcs11_obj_t CERT, const char * URL, unsigned int FLAGS) CERT: The structure to store the parsed certificate URL: a PKCS 11 url identifying the key FLAGS: One of GNUTLS_PKCS11_OBJ_* flags This function will "import" a PKCS 11 URL identifying a certificate key to the `gnutls_pkcs11_obj_t' structure. This does not involve any parsing (such as X.509 or OpenPGP) since the `gnutls_pkcs11_obj_t' is format agnostic. Only data are transferred. *Returns:* On success, `GNUTLS_E_SUCCESS' is returned, otherwise a negative error value. gnutls_pkcs11_obj_init ---------------------- -- Function: int gnutls_pkcs11_obj_init (gnutls_pkcs11_obj_t * OBJ) OBJ: The structure to be initialized This function will initialize a pkcs11 certificate structure. *Returns:* On success, `GNUTLS_E_SUCCESS' is returned, otherwise a negative error value. gnutls_pkcs11_obj_list_import_url --------------------------------- -- Function: int gnutls_pkcs11_obj_list_import_url (gnutls_pkcs11_obj_t * P_LIST, unsigned int * N_LIST, const char * URL, gnutls_pkcs11_obj_attr_t ATTRS, unsigned int FLAGS) P_LIST: An uninitialized object list (may be NULL) N_LIST: initially should hold the maximum size of the list. Will contain the actual size. URL: A PKCS 11 url identifying a set of objects ATTRS: Attributes of type `gnutls_pkcs11_obj_attr_t' that can be used to limit output FLAGS: One of GNUTLS_PKCS11_OBJ_* flags This function will initialize and set values to an object list by using all objects identified by a PKCS 11 URL. *Returns:* On success, `GNUTLS_E_SUCCESS' is returned, otherwise a negative error value. gnutls_pkcs11_privkey_deinit ---------------------------- -- Function: void gnutls_pkcs11_privkey_deinit (gnutls_pkcs11_privkey_t KEY) KEY: The structure to be initialized This function will deinitialize a private key structure. gnutls_pkcs11_privkey_export_url -------------------------------- -- Function: int gnutls_pkcs11_privkey_export_url (gnutls_pkcs11_privkey_t KEY, gnutls_pkcs11_url_type_t DETAILED, char ** URL) KEY: Holds the PKCS 11 key DETAILED: non zero if a detailed URL is required URL: will contain an allocated url This function will export a URL identifying the given key. *Returns:* On success, `GNUTLS_E_SUCCESS' is returned, otherwise a negative error value. gnutls_pkcs11_privkey_get_info ------------------------------ -- Function: int gnutls_pkcs11_privkey_get_info (gnutls_pkcs11_privkey_t PKEY, gnutls_pkcs11_obj_info_t ITYPE, void * OUTPUT, size_t * OUTPUT_SIZE) PKEY: should contain a `gnutls_pkcs11_privkey_t' structure ITYPE: Denotes the type of information requested OUTPUT: where output will be stored OUTPUT_SIZE: contains the maximum size of the output and will be overwritten with actual This function will return information about the PKCS 11 private key such as the label, id as well as token information where the key is stored. When output is text it returns null terminated string although `output_size' contains the size of the actual data only. *Returns:* zero on success or a negative value on error. gnutls_pkcs11_privkey_get_pk_algorithm -------------------------------------- -- Function: int gnutls_pkcs11_privkey_get_pk_algorithm (gnutls_pkcs11_privkey_t KEY, unsigned int * BITS) KEY: should contain a `gnutls_pkcs11_privkey_t' structure This function will return the public key algorithm of a private key. *Returns:* a member of the `gnutls_pk_algorithm_t' enumeration on success, or a negative value on error. gnutls_pkcs11_privkey_import_url -------------------------------- -- Function: int gnutls_pkcs11_privkey_import_url (gnutls_pkcs11_privkey_t PKEY, const char * URL, unsigned int FLAGS) PKEY: The structure to store the parsed key URL: a PKCS 11 url identifying the key FLAGS: sequence of GNUTLS_PKCS_PRIVKEY_* This function will "import" a PKCS 11 URL identifying a private key to the `gnutls_pkcs11_privkey_t' structure. In reality since in most cases keys cannot be exported, the private key structure is being associated with the available operations on the token. *Returns:* On success, `GNUTLS_E_SUCCESS' is returned, otherwise a negative error value. gnutls_pkcs11_privkey_init -------------------------- -- Function: int gnutls_pkcs11_privkey_init (gnutls_pkcs11_privkey_t * KEY) KEY: The structure to be initialized This function will initialize an private key structure. *Returns:* On success, `GNUTLS_E_SUCCESS' is returned, otherwise a negative error value. gnutls_pkcs11_reinit -------------------- -- Function: int gnutls_pkcs11_reinit ( VOID) This function will reinitialize the PKCS 11 subsystem in gnutls. This is required by PKCS 11 when an application uses `fork()'. The reinitialization function must be called on the child. *Returns:* On success, `GNUTLS_E_SUCCESS' (0) is returned, otherwise a negative error value. *Since:* 3.0.0 gnutls_pkcs11_set_pin_function ------------------------------ -- Function: void gnutls_pkcs11_set_pin_function (gnutls_pkcs11_pin_callback_t FN, void * USERDATA) FN: The PIN callback USERDATA: data to be supplied to callback This function will set a callback function to be used when a PIN is required for PKCS 11 operations. Callback for PKCS`11' PIN entry. The callback provides the PIN code to unlock the token with label 'token_label', specified by the URL 'token_url'. The PIN code, as a NUL-terminated ASCII string, should be copied into the 'pin' buffer (of maximum size pin_max), and return 0 to indicate success. Alternatively, the callback may return a negative gnutls error code to indicate failure and cancel PIN entry (in which case, the contents of the 'pin' parameter are ignored). When a PIN is required, the callback will be invoked repeatedly (and indefinitely) until either the returned PIN code is correct, the callback returns failure, or the token refuses login (e.g. when the token is locked due to too many incorrect PINs!). For the first such invocation, the 'attempt' counter will have value zero; it will increase by one for each subsequent attempt. *Returns:* On success, `GNUTLS_E_SUCCESS' is returned, otherwise a negative error value. gnutls_pkcs11_set_token_function -------------------------------- -- Function: void gnutls_pkcs11_set_token_function (gnutls_pkcs11_token_callback_t FN, void * USERDATA) FN: The token callback USERDATA: data to be supplied to callback This function will set a callback function to be used when a token needs to be inserted to continue PKCS 11 operations. *Returns:* On success, `GNUTLS_E_SUCCESS' is returned, otherwise a negative error value. gnutls_pkcs11_token_get_flags ----------------------------- -- Function: int gnutls_pkcs11_token_get_flags (const char * URL, unsigned int * FLAGS) URL: should contain a PKCS 11 URL FLAGS: The output flags (GNUTLS_PKCS11_TOKEN_*) This function will return information about the PKCS 11 token flags. *Returns:* zero on success or a negative value on error. gnutls_pkcs11_token_get_info ---------------------------- -- Function: int gnutls_pkcs11_token_get_info (const char * URL, gnutls_pkcs11_token_info_t TTYPE, void * OUTPUT, size_t * OUTPUT_SIZE) URL: should contain a PKCS 11 URL TTYPE: Denotes the type of information requested OUTPUT: where output will be stored OUTPUT_SIZE: contains the maximum size of the output and will be overwritten with actual This function will return information about the PKCS 11 token such as the label, id as well as token information where the key is stored. *Returns:* zero on success or a negative value on error. gnutls_pkcs11_token_get_mechanism --------------------------------- -- Function: int gnutls_pkcs11_token_get_mechanism (const char * URL, int IDX, unsigned long * MECHANISM) URL: should contain a PKCS 11 URL IDX: The index of the mechanism MECHANISM: The PKCS `11' mechanism ID This function will return the names of the supported mechanisms by the token. It should be called with an increasing index until it return GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE. *Returns:* zero on success or a negative value on error. gnutls_pkcs11_token_get_url --------------------------- -- Function: int gnutls_pkcs11_token_get_url (unsigned int SEQ, gnutls_pkcs11_url_type_t DETAILED, char ** URL) SEQ: sequence number starting from 0 DETAILED: non zero if a detailed URL is required URL: will contain an allocated url This function will return the URL for each token available in system. The url has to be released using `gnutls_free()' *Returns:* On success, `GNUTLS_E_SUCCESS' is returned, `GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE' if the sequence number exceeds the available tokens, otherwise a negative error value. gnutls_pkcs11_token_init ------------------------ -- Function: int gnutls_pkcs11_token_init (const char * TOKEN_URL, const char * SO_PIN, const char * LABEL) TOKEN_URL: A PKCS `11' URL specifying a token SO_PIN: Security Officer's PIN LABEL: A name to be used for the token This function will initialize (format) a token. If the token is at a factory defaults state the security officer's PIN given will be set to be the default. Otherwise it should match the officer's PIN. *Returns:* On success, `GNUTLS_E_SUCCESS' is returned, otherwise a negative error value. gnutls_pkcs11_token_set_pin --------------------------- -- Function: int gnutls_pkcs11_token_set_pin (const char * TOKEN_URL, const char * OLDPIN, const char * NEWPIN, unsigned int FLAGS) TOKEN_URL: A PKCS `11' URL specifying a token OLDPIN: old user's PIN NEWPIN: new user's PIN FLAGS: one of gnutls_pkcs11_pin_flag_t This function will modify or set a user's PIN for the given token. If it is called to set a user pin for first time the oldpin must be NULL. *Returns:* On success, `GNUTLS_E_SUCCESS' is returned, otherwise a negative error value. gnutls_prf_raw -------------- -- Function: int gnutls_prf_raw (gnutls_session_t SESSION, size_t LABEL_SIZE, const char * LABEL, size_t SEED_SIZE, const char * SEED, size_t OUTSIZE, char * OUT) SESSION: is a `gnutls_session_t' structure. LABEL_SIZE: length of the `label' variable. LABEL: label used in PRF computation, typically a short string. SEED_SIZE: length of the `seed' variable. SEED: optional extra data to seed the PRF with. OUTSIZE: size of pre-allocated output buffer to hold the output. OUT: pre-allocate buffer to hold the generated data. Apply the TLS Pseudo-Random-Function (PRF) using the master secret on some data. The `label' variable usually contain a string denoting the purpose for the generated data. The `seed' usually contain data such as the client and server random, perhaps together with some additional data that is added to guarantee uniqueness of the output for a particular purpose. Because the output is not guaranteed to be unique for a particular session unless `seed' include the client random and server random fields (the PRF would output the same data on another connection resumed from the first one), it is not recommended to use this function directly. The `gnutls_prf()' function seed the PRF with the client and server random fields directly, and is recommended if you want to generate pseudo random data unique for each session. *Returns:* `GNUTLS_E_SUCCESS' on success, or an error code. gnutls_prf ---------- -- Function: int gnutls_prf (gnutls_session_t SESSION, size_t LABEL_SIZE, const char * LABEL, int SERVER_RANDOM_FIRST, size_t EXTRA_SIZE, const char * EXTRA, size_t OUTSIZE, char * OUT) SESSION: is a `gnutls_session_t' structure. LABEL_SIZE: length of the `label' variable. LABEL: label used in PRF computation, typically a short string. SERVER_RANDOM_FIRST: non-0 if server random field should be first in seed EXTRA_SIZE: length of the `extra' variable. EXTRA: optional extra data to seed the PRF with. OUTSIZE: size of pre-allocated output buffer to hold the output. OUT: pre-allocate buffer to hold the generated data. Apply the TLS Pseudo-Random-Function (PRF) using the master secret on some data, seeded with the client and server random fields. The `label' variable usually contain a string denoting the purpose for the generated data. The `server_random_first' indicate whether the client random field or the server random field should be first in the seed. Non-0 indicate that the server random field is first, 0 that the client random field is first. The `extra' variable can be used to add more data to the seed, after the random variables. It can be used to tie make sure the generated output is strongly connected to some additional data (e.g., a string used in user authentication). The output is placed in *`OUT', which must be pre-allocated. *Returns:* `GNUTLS_E_SUCCESS' on success, or an error code. gnutls_priority_deinit ---------------------- -- Function: void gnutls_priority_deinit (gnutls_priority_t PRIORITY_CACHE) PRIORITY_CACHE: is a `gnutls_prioritity_t' structure. Deinitializes the priority cache. gnutls_priority_init -------------------- -- Function: int gnutls_priority_init (gnutls_priority_t * PRIORITY_CACHE, const char * PRIORITIES, const char ** ERR_POS) PRIORITY_CACHE: is a `gnutls_prioritity_t' structure. PRIORITIES: is a string describing priorities ERR_POS: In case of an error this will have the position in the string the error occured Sets priorities for the ciphers, key exchange methods, macs and compression methods. The `priorities' option allows you to specify a colon separated list of the cipher priorities to enable. *Common keywords:* Some keywords are defined to provide quick access to common preferences. "PERFORMANCE" means all the "secure" ciphersuites are enabled, limited to 128 bit ciphers and sorted by terms of speed performance. "NORMAL" means all "secure" ciphersuites. The 256-bit ciphers are included as a fallback only. The ciphers are sorted by security margin. "SECURE128" means all "secure" ciphersuites with ciphers up to 128 bits, sorted by security margin. "SECURE256" means all "secure" ciphersuites including the 256 bit ciphers, sorted by security margin. "EXPORT" means all ciphersuites are enabled, including the low-security 40 bit ciphers. "NONE" means nothing is enabled. This disables even protocols and compression methods. *Special keywords:* "!" or "-" appended with an algorithm will remove this algorithm. "+" appended with an algorithm will add this algorithm. Check the GnuTLS manual section "Priority strings" for detailed information. *Examples:* "NONE:+VERS-TLS-ALL:+MAC-ALL:+RSA:+AES-128-CBC:+SIGN-ALL:+COMP-NULL" "NORMAL:-ARCFOUR-128" means normal ciphers except for ARCFOUR-128. "SECURE:-VERS-SSL3.0:+COMP-DEFLATE" means that only secure ciphers are enabled, SSL3.0 is disabled, and libz compression enabled. "NONE:+VERS-TLS-ALL:+AES-128-CBC:+RSA:+SHA1:+COMP-NULL:+SIGN-RSA-SHA1", "NORMAL:`COMPAT'" is the most compatible mode. *Returns:* On syntax error `GNUTLS_E_INVALID_REQUEST' is returned, `GNUTLS_E_SUCCESS' on success, or an error code. gnutls_priority_set_direct -------------------------- -- Function: int gnutls_priority_set_direct (gnutls_session_t SESSION, const char * PRIORITIES, const char ** ERR_POS) SESSION: is a `gnutls_session_t' structure. PRIORITIES: is a string describing priorities ERR_POS: In case of an error this will have the position in the string the error occured Sets the priorities to use on the ciphers, key exchange methods, macs and compression methods. This function avoids keeping a priority cache and is used to directly set string priorities to a TLS session. For documentation check the `gnutls_priority_init()'. *Returns:* On syntax error `GNUTLS_E_INVALID_REQUEST' is returned, `GNUTLS_E_SUCCESS' on success, or an error code. gnutls_priority_set ------------------- -- Function: int gnutls_priority_set (gnutls_session_t SESSION, gnutls_priority_t PRIORITY) SESSION: is a `gnutls_session_t' structure. PRIORITY: is a `gnutls_priority_t' structure. Sets the priorities to use on the ciphers, key exchange methods, macs and compression methods. *Returns:* `GNUTLS_E_SUCCESS' on success, or an error code. gnutls_privkey_decrypt_data --------------------------- -- Function: int gnutls_privkey_decrypt_data (gnutls_privkey_t KEY, unsigned int FLAGS, const gnutls_datum_t * CIPHERTEXT, gnutls_datum_t * PLAINTEXT) KEY: Holds the key FLAGS: zero for now CIPHERTEXT: holds the data to be decrypted PLAINTEXT: will contain the decrypted data, allocated with `gnutls_malloc()' This function will decrypt the given data using the algorithm supported by the private key. *Returns:* On success, `GNUTLS_E_SUCCESS' is returned, otherwise a negative error value. gnutls_privkey_deinit --------------------- -- Function: void gnutls_privkey_deinit (gnutls_privkey_t KEY) KEY: The structure to be deinitialized This function will deinitialize a private key structure. gnutls_privkey_get_pk_algorithm ------------------------------- -- Function: int gnutls_privkey_get_pk_algorithm (gnutls_privkey_t KEY, unsigned int * BITS) KEY: should contain a `gnutls_privkey_t' structure BITS: If set will return the number of bits of the parameters (may be NULL) This function will return the public key algorithm of a private key and if possible will return a number of bits that indicates the security parameter of the key. *Returns:* a member of the `gnutls_pk_algorithm_t' enumeration on success, or a negative value on error. gnutls_privkey_get_type ----------------------- -- Function: gnutls_privkey_type_t gnutls_privkey_get_type (gnutls_privkey_t KEY) KEY: should contain a `gnutls_privkey_t' structure This function will return the type of the private key. This is actually the type of the subsystem used to set this private key. *Returns:* a member of the `gnutls_privkey_type_t' enumeration on success, or a negative value on error. gnutls_privkey_import_openpgp ----------------------------- -- Function: int gnutls_privkey_import_openpgp (gnutls_privkey_t PKEY, gnutls_openpgp_privkey_t KEY, unsigned int FLAGS) PKEY: The private key KEY: The private key to be imported FLAGS: should be zero This function will import the given private key to the abstract `gnutls_privkey_t' structure. The `gnutls_openpgp_privkey_t' object must not be deallocated during the lifetime of this structure. The subkey set as preferred will be used, or the master key otherwise. *Returns:* On success, `GNUTLS_E_SUCCESS' is returned, otherwise a negative error value. gnutls_privkey_import_pkcs11 ---------------------------- -- Function: int gnutls_privkey_import_pkcs11 (gnutls_privkey_t PKEY, gnutls_pkcs11_privkey_t KEY, unsigned int FLAGS) PKEY: The private key KEY: The private key to be imported FLAGS: should be zero This function will import the given private key to the abstract `gnutls_privkey_t' structure. The `gnutls_pkcs11_privkey_t' object must not be deallocated during the lifetime of this structure. *Returns:* On success, `GNUTLS_E_SUCCESS' is returned, otherwise a negative error value. gnutls_privkey_import_x509 -------------------------- -- Function: int gnutls_privkey_import_x509 (gnutls_privkey_t PKEY, gnutls_x509_privkey_t KEY, unsigned int FLAGS) PKEY: The private key KEY: The private key to be imported FLAGS: should be zero This function will import the given private key to the abstract `gnutls_privkey_t' structure. The `gnutls_x509_privkey_t' object must not be deallocated during the lifetime of this structure. *Returns:* On success, `GNUTLS_E_SUCCESS' is returned, otherwise a negative error value. gnutls_privkey_init ------------------- -- Function: int gnutls_privkey_init (gnutls_privkey_t * KEY) KEY: The structure to be initialized This function will initialize an private key structure. *Returns:* On success, `GNUTLS_E_SUCCESS' is returned, otherwise a negative error value. gnutls_privkey_sign_data ------------------------ -- Function: int gnutls_privkey_sign_data (gnutls_privkey_t SIGNER, gnutls_digest_algorithm_t HASH, unsigned int FLAGS, const gnutls_datum_t * DATA, gnutls_datum_t * SIGNATURE) SIGNER: Holds the key HASH: should be a digest algorithm FLAGS: should be 0 for now DATA: holds the data to be signed SIGNATURE: will contain the signature allocate with `gnutls_malloc()' This function will sign the given data using a signature algorithm supported by the private key. Signature algorithms are always used together with a hash functions. Different hash functions may be used for the RSA algorithm, but only SHA-1 for the DSA keys. *Returns:* On success, `GNUTLS_E_SUCCESS' is returned, otherwise a negative error value. *Since:* 2.12.0 gnutls_privkey_sign_hash ------------------------ -- Function: int gnutls_privkey_sign_hash (gnutls_privkey_t SIGNER, gnutls_digest_algorithm_t HASH_ALGO, unsigned int FLAGS, const gnutls_datum_t * HASH_DATA, gnutls_datum_t * SIGNATURE) SIGNER: Holds the signer's key HASH_ALGO: The hash algorithm used FLAGS: zero for now HASH_DATA: holds the data to be signed SIGNATURE: will contain newly allocated signature This function will sign the given hashed data using a signature algorithm supported by the private key. Signature algorithms are always used together with a hash functions. Different hash functions may be used for the RSA algorithm, but only SHA-XXX for the DSA keys. Use `gnutls_x509_crt_get_preferred_hash_algorithm()' to determine the hash algorithm. *Returns:* On success, `GNUTLS_E_SUCCESS' is returned, otherwise a negative error value. *Since:* 2.12.0 gnutls_protocol_get_id ---------------------- -- Function: gnutls_protocol_t gnutls_protocol_get_id (const char * NAME) NAME: is a protocol name The names are compared in a case insensitive way. *Returns:* an id of the specified protocol, or `GNUTLS_VERSION_UNKNOWN' on error. gnutls_protocol_get_name ------------------------ -- Function: const char * gnutls_protocol_get_name (gnutls_protocol_t VERSION) VERSION: is a (gnutls) version number Convert a `gnutls_protocol_t' value to a string. *Returns:* a string that contains the name of the specified TLS version (e.g., "TLS1.0"), or `NULL'. gnutls_protocol_get_version --------------------------- -- Function: gnutls_protocol_t gnutls_protocol_get_version (gnutls_session_t SESSION) SESSION: is a `gnutls_session_t' structure. Get TLS version, a `gnutls_protocol_t' value. *Returns:* the version of the currently used protocol. gnutls_protocol_list -------------------- -- Function: const gnutls_protocol_t * gnutls_protocol_list ( VOID) Get a list of supported protocols, e.g. SSL 3.0, TLS 1.0 etc. *Returns:* a zero-terminated list of `gnutls_protocol_t' integers indicating the available protocols. gnutls_protocol_set_priority ---------------------------- -- Function: int gnutls_protocol_set_priority (gnutls_session_t SESSION, const int * LIST) SESSION: is a `gnutls_session_t' structure. LIST: is a 0 terminated list of gnutls_protocol_t elements. Sets the priority on the protocol versions supported by gnutls. This function actually enables or disables protocols. Newer protocol versions always have highest priority. *Returns:* `GNUTLS_E_SUCCESS' on success, or an error code. gnutls_psk_allocate_client_credentials -------------------------------------- -- Function: int gnutls_psk_allocate_client_credentials (gnutls_psk_client_credentials_t * SC) SC: is a pointer to a `gnutls_psk_server_credentials_t' structure. This structure is complex enough to manipulate directly thus this helper function is provided in order to allocate it. *Returns:* `GNUTLS_E_SUCCESS' on success, or an error code. gnutls_psk_allocate_server_credentials -------------------------------------- -- Function: int gnutls_psk_allocate_server_credentials (gnutls_psk_server_credentials_t * SC) SC: is a pointer to a `gnutls_psk_server_credentials_t' structure. This structure is complex enough to manipulate directly thus this helper function is provided in order to allocate it. *Returns:* `GNUTLS_E_SUCCESS' on success, or an error code. gnutls_psk_client_get_hint -------------------------- -- Function: const char * gnutls_psk_client_get_hint (gnutls_session_t SESSION) SESSION: is a gnutls session The PSK identity hint may give the client help in deciding which username to use. This should only be called in case of PSK authentication and in case of a client. *Returns:* the identity hint of the peer, or `NULL' in case of an error. *Since:* 2.4.0 gnutls_psk_free_client_credentials ---------------------------------- -- Function: void gnutls_psk_free_client_credentials (gnutls_psk_client_credentials_t SC) SC: is a `gnutls_psk_client_credentials_t' structure. This structure is complex enough to manipulate directly thus this helper function is provided in order to free (deallocate) it. gnutls_psk_free_server_credentials ---------------------------------- -- Function: void gnutls_psk_free_server_credentials (gnutls_psk_server_credentials_t SC) SC: is a `gnutls_psk_server_credentials_t' structure. This structure is complex enough to manipulate directly thus this helper function is provided in order to free (deallocate) it. gnutls_psk_netconf_derive_key ----------------------------- -- Function: int gnutls_psk_netconf_derive_key (const char * PASSWORD, const char * PSK_IDENTITY, const char * PSK_IDENTITY_HINT, gnutls_datum_t * OUTPUT_KEY) PASSWORD: zero terminated string containing password. PSK_IDENTITY: zero terminated string with PSK identity. PSK_IDENTITY_HINT: zero terminated string with PSK identity hint. OUTPUT_KEY: output variable, contains newly allocated *data pointer. This function will derive a PSK key from a password, for use with the Netconf protocol. *Returns:* `GNUTLS_E_SUCCESS' on success, or an error code. *Since:* 2.4.0 *Deprecated:* The need for this interface was dropped from the standard on publication as a RFC. The function works now but will return a hard failure in a future release. gnutls_psk_server_get_username ------------------------------ -- Function: const char * gnutls_psk_server_get_username (gnutls_session_t SESSION) SESSION: is a gnutls session This should only be called in case of PSK authentication and in case of a server. *Returns:* the username of the peer, or `NULL' in case of an error. gnutls_psk_set_client_credentials_function ------------------------------------------ -- Function: void gnutls_psk_set_client_credentials_function (gnutls_psk_client_credentials_t CRED, gnutls_psk_client_credentials_function * FUNC) CRED: is a `gnutls_psk_server_credentials_t' structure. FUNC: is the callback function This function can be used to set a callback to retrieve the username and password for client PSK authentication. The callback's function form is: int (*callback)(gnutls_session_t, char** username, gnutls_datum_t* key); The `username' and `key'->data must be allocated using `gnutls_malloc()'. `username' should be ASCII strings or UTF-8 strings prepared using the "SASLprep" profile of "stringprep". The callback function will be called once per handshake. The callback function should return 0 on success. -1 indicates an error. gnutls_psk_set_client_credentials --------------------------------- -- Function: int gnutls_psk_set_client_credentials (gnutls_psk_client_credentials_t RES, const char * USERNAME, const gnutls_datum_t * KEY, gnutls_psk_key_flags FLAGS) RES: is a `gnutls_psk_client_credentials_t' structure. USERNAME: is the user's zero-terminated userid KEY: is the user's key This function sets the username and password, in a gnutls_psk_client_credentials_t structure. Those will be used in PSK authentication. `username' should be an ASCII string or UTF-8 strings prepared using the "SASLprep" profile of "stringprep". The key can be either in raw byte format or in Hex format (without the 0x prefix). *Returns:* `GNUTLS_E_SUCCESS' on success, or an error code. gnutls_psk_set_params_function ------------------------------ -- Function: void gnutls_psk_set_params_function (gnutls_psk_server_credentials_t RES, gnutls_params_function * FUNC) RES: is a gnutls_psk_server_credentials_t structure FUNC: is the function to be called This function will set a callback in order for the server to get the Diffie-Hellman or RSA parameters for PSK authentication. The callback should return zero on success. gnutls_psk_set_server_credentials_file -------------------------------------- -- Function: int gnutls_psk_set_server_credentials_file (gnutls_psk_server_credentials_t RES, const char * PASSWORD_FILE) RES: is a `gnutls_psk_server_credentials_t' structure. PASSWORD_FILE: is the PSK password file (passwd.psk) This function sets the password file, in a `gnutls_psk_server_credentials_t' structure. This password file holds usernames and keys and will be used for PSK authentication. *Returns:* `GNUTLS_E_SUCCESS' on success, or an error code. gnutls_psk_set_server_credentials_function ------------------------------------------ -- Function: void gnutls_psk_set_server_credentials_function (gnutls_psk_server_credentials_t CRED, gnutls_psk_server_credentials_function * FUNC) CRED: is a `gnutls_psk_server_credentials_t' structure. FUNC: is the callback function This function can be used to set a callback to retrieve the user's PSK credentials. The callback's function form is: int (*callback)(gnutls_session_t, const char* username, gnutls_datum_t* key); `username' contains the actual username. The `key' must be filled in using the `gnutls_malloc()'. In case the callback returned a negative number then gnutls will assume that the username does not exist. The callback function will only be called once per handshake. The callback function should return 0 on success, while -1 indicates an error. gnutls_psk_set_server_credentials_hint -------------------------------------- -- Function: int gnutls_psk_set_server_credentials_hint (gnutls_psk_server_credentials_t RES, const char * HINT) RES: is a `gnutls_psk_server_credentials_t' structure. HINT: is the PSK identity hint string This function sets the identity hint, in a `gnutls_psk_server_credentials_t' structure. This hint is sent to the client to help it chose a good PSK credential (i.e., username and password). *Returns:* `GNUTLS_E_SUCCESS' on success, or an error code. *Since:* 2.4.0 gnutls_psk_set_server_dh_params ------------------------------- -- Function: void gnutls_psk_set_server_dh_params (gnutls_psk_server_credentials_t RES, gnutls_dh_params_t DH_PARAMS) RES: is a gnutls_psk_server_credentials_t structure DH_PARAMS: is a structure that holds Diffie-Hellman parameters. This function will set the Diffie-Hellman parameters for an anonymous server to use. These parameters will be used in Diffie-Hellman exchange with PSK cipher suites. gnutls_psk_set_server_params_function ------------------------------------- -- Function: void gnutls_psk_set_server_params_function (gnutls_psk_server_credentials_t RES, gnutls_params_function * FUNC) RES: is a `gnutls_certificate_credentials_t' structure FUNC: is the function to be called This function will set a callback in order for the server to get the Diffie-Hellman parameters for PSK authentication. The callback should return zero on success. gnutls_pubkey_deinit -------------------- -- Function: void gnutls_pubkey_deinit (gnutls_pubkey_t KEY) KEY: The structure to be deinitialized This function will deinitialize a public key structure. gnutls_pubkey_export -------------------- -- Function: int gnutls_pubkey_export (gnutls_pubkey_t KEY, gnutls_x509_crt_fmt_t FORMAT, void * OUTPUT_DATA, size_t * OUTPUT_DATA_SIZE) KEY: Holds the certificate FORMAT: the format of output params. One of PEM or DER. OUTPUT_DATA: will contain a certificate PEM or DER encoded OUTPUT_DATA_SIZE: holds the size of output_data (and will be replaced by the actual size of parameters) This function will export the certificate to DER or PEM format. If the buffer provided is not long enough to hold the output, then *output_data_size is updated and GNUTLS_E_SHORT_MEMORY_BUFFER will be returned. If the structure is PEM encoded, it will have a header of "BEGIN CERTIFICATE". *Return value:* In case of failure a negative value will be returned, and 0 on success. gnutls_pubkey_get_key_id ------------------------ -- Function: int gnutls_pubkey_get_key_id (gnutls_pubkey_t KEY, unsigned int FLAGS, unsigned char * OUTPUT_DATA, size_t * OUTPUT_DATA_SIZE) KEY: Holds the public key FLAGS: should be 0 for now OUTPUT_DATA: will contain the key ID OUTPUT_DATA_SIZE: holds the size of output_data (and will be replaced by the actual size of parameters) This function will return a unique ID the depends on the public key parameters. This ID can be used in checking whether a certificate corresponds to the given public key. If the buffer provided is not long enough to hold the output, then *output_data_size is updated and GNUTLS_E_SHORT_MEMORY_BUFFER will be returned. The output will normally be a SHA-1 hash output, which is 20 bytes. *Return value:* In case of failure a negative value will be returned, and 0 on success. gnutls_pubkey_get_key_usage --------------------------- -- Function: int gnutls_pubkey_get_key_usage (gnutls_pubkey_t KEY, unsigned int * USAGE) KEY: should contain a `gnutls_pubkey_t' structure USAGE: If set will return the number of bits of the parameters (may be NULL) This function will return the key usage of the public key. *Returns:* On success, `GNUTLS_E_SUCCESS' is returned, otherwise a negative error value. gnutls_pubkey_get_pk_algorithm ------------------------------ -- Function: int gnutls_pubkey_get_pk_algorithm (gnutls_pubkey_t KEY, unsigned int * BITS) KEY: should contain a `gnutls_pubkey_t' structure BITS: If set will return the number of bits of the parameters (may be NULL) This function will return the public key algorithm of a public key and if possible will return a number of bits that indicates the security parameter of the key. *Returns:* a member of the `gnutls_pk_algorithm_t' enumeration on success, or a negative value on error. gnutls_pubkey_get_pk_dsa_raw ---------------------------- -- Function: int gnutls_pubkey_get_pk_dsa_raw (gnutls_pubkey_t KEY, gnutls_datum_t * P, gnutls_datum_t * Q, gnutls_datum_t * G, gnutls_datum_t * Y) KEY: Holds the public key P: will hold the p Q: will hold the q G: will hold the g Y: will hold the y This function will export the DSA public key's parameters found in the given certificate. The new parameters will be allocated using `gnutls_malloc()' and will be stored in the appropriate datum. *Returns:* `GNUTLS_E_SUCCESS' on success, otherwise an error. gnutls_pubkey_get_pk_rsa_raw ---------------------------- -- Function: int gnutls_pubkey_get_pk_rsa_raw (gnutls_pubkey_t KEY, gnutls_datum_t * M, gnutls_datum_t * E) KEY: Holds the certificate M: will hold the modulus E: will hold the public exponent This function will export the RSA public key's parameters found in the given structure. The new parameters will be allocated using `gnutls_malloc()' and will be stored in the appropriate datum. *Returns:* `GNUTLS_E_SUCCESS' on success, otherwise an error. gnutls_pubkey_get_preferred_hash_algorithm ------------------------------------------ -- Function: int gnutls_pubkey_get_preferred_hash_algorithm (gnutls_pubkey_t KEY, gnutls_digest_algorithm_t * HASH, unsigned int * MAND) KEY: Holds the certificate HASH: The result of the call with the hash algorithm used for signature MAND: If non zero it means that the algorithm MUST use this hash. May be NULL. This function will read the certifcate and return the appropriate digest algorithm to use for signing with this certificate. Some certificates (i.e. DSA might not be able to sign without the preferred algorithm). *Returns:* the 0 if the hash algorithm is found. A negative value is returned on error. *Since:* 2.11.0 gnutls_pubkey_get_verify_algorithm ---------------------------------- -- Function: int gnutls_pubkey_get_verify_algorithm (gnutls_pubkey_t KEY, const gnutls_datum_t * SIGNATURE, gnutls_digest_algorithm_t * HASH) KEY: Holds the certificate SIGNATURE: contains the signature HASH: The result of the call with the hash algorithm used for signature This function will read the certifcate and the signed data to determine the hash algorithm used to generate the signature. *Returns:* the 0 if the hash algorithm is found. A negative value is returned on error. gnutls_pubkey_import_dsa_raw ---------------------------- -- Function: int gnutls_pubkey_import_dsa_raw (gnutls_pubkey_t KEY, const gnutls_datum_t * P, const gnutls_datum_t * Q, const gnutls_datum_t * G, const gnutls_datum_t * Y) KEY: The structure to store the parsed key P: holds the p Q: holds the q G: holds the g Y: holds the y This function will convert the given DSA raw parameters to the native `gnutls_pubkey_t' format. The output will be stored in `key'. *Returns:* On success, `GNUTLS_E_SUCCESS' is returned, otherwise a negative error value. gnutls_pubkey_import_openpgp ---------------------------- -- Function: int gnutls_pubkey_import_openpgp (gnutls_pubkey_t KEY, gnutls_openpgp_crt_t CRT, unsigned int FLAGS) KEY: The public key CRT: The certificate to be imported FLAGS: should be zero This function will import the given public key to the abstract `gnutls_pubkey_t' structure. The subkey set as preferred will be imported or the master key otherwise. *Returns:* On success, `GNUTLS_E_SUCCESS' is returned, otherwise a negative error value. gnutls_pubkey_import_pkcs11_url ------------------------------- -- Function: int gnutls_pubkey_import_pkcs11_url (gnutls_pubkey_t KEY, const char * URL, unsigned int FLAGS) KEY: A key of type `gnutls_pubkey_t' URL: A PKCS 11 url FLAGS: One of GNUTLS_PKCS11_OBJ_* flags This function will import a PKCS 11 certificate to a `gnutls_pubkey_t' structure. *Returns:* On success, `GNUTLS_E_SUCCESS' is returned, otherwise a negative error value. gnutls_pubkey_import_pkcs11 --------------------------- -- Function: int gnutls_pubkey_import_pkcs11 (gnutls_pubkey_t KEY, gnutls_pkcs11_obj_t OBJ, unsigned int FLAGS) KEY: The public key OBJ: The parameters to be imported FLAGS: should be zero This function will import the given public key to the abstract `gnutls_pubkey_t' structure. *Returns:* On success, `GNUTLS_E_SUCCESS' is returned, otherwise a negative error value. gnutls_pubkey_import_privkey ---------------------------- -- Function: int gnutls_pubkey_import_privkey (gnutls_pubkey_t KEY, gnutls_privkey_t PKEY, unsigned int USAGE, unsigned int FLAGS) KEY: The public key PKEY: The private key USAGE: GNUTLS_KEY_* key usage flags. FLAGS: should be zero This function will import the given public key to the abstract `gnutls_pubkey_t' structure. *Returns:* On success, `GNUTLS_E_SUCCESS' is returned, otherwise a negative error value. *Since:* 2.12.0 gnutls_pubkey_import_rsa_raw ---------------------------- -- Function: int gnutls_pubkey_import_rsa_raw (gnutls_pubkey_t KEY, const gnutls_datum_t * M, const gnutls_datum_t * E) KEY: Is a structure will hold the parameters M: holds the modulus E: holds the public exponent This function will replace the parameters in the given structure. The new parameters should be stored in the appropriate gnutls_datum. *Returns:* `GNUTLS_E_SUCCESS' on success, or an negative error code. gnutls_pubkey_import_x509 ------------------------- -- Function: int gnutls_pubkey_import_x509 (gnutls_pubkey_t KEY, gnutls_x509_crt_t CRT, unsigned int FLAGS) KEY: The public key CRT: The certificate to be imported FLAGS: should be zero This function will import the given public key to the abstract `gnutls_pubkey_t' structure. *Returns:* On success, `GNUTLS_E_SUCCESS' is returned, otherwise a negative error value. gnutls_pubkey_import -------------------- -- Function: int gnutls_pubkey_import (gnutls_pubkey_t KEY, const gnutls_datum_t * DATA, gnutls_x509_crt_fmt_t FORMAT) KEY: The structure to store the parsed public key. DATA: The DER or PEM encoded certificate. FORMAT: One of DER or PEM This function will convert the given DER or PEM encoded Public key to the native gnutls_pubkey_t format.The output will be stored * in key. If the Certificate is PEM encoded it should have a header of "PUBLIC KEY". *Returns:* On success, `GNUTLS_E_SUCCESS' is returned, otherwise a negative error value. gnutls_pubkey_init ------------------ -- Function: int gnutls_pubkey_init (gnutls_pubkey_t * KEY) KEY: The structure to be initialized This function will initialize an public key structure. *Returns:* On success, `GNUTLS_E_SUCCESS' is returned, otherwise a negative error value. gnutls_pubkey_set_key_usage --------------------------- -- Function: int gnutls_pubkey_set_key_usage (gnutls_pubkey_t KEY, unsigned int USAGE) KEY: a certificate of type `gnutls_x509_crt_t' USAGE: an ORed sequence of the GNUTLS_KEY_* elements. This function will set the key usage flags of the public key. This is only useful if the key is to be exported to a certificate or certificate request. *Returns:* On success, `GNUTLS_E_SUCCESS' is returned, otherwise a negative error value. gnutls_pubkey_verify_data ------------------------- -- Function: int gnutls_pubkey_verify_data (gnutls_pubkey_t PUBKEY, unsigned int FLAGS, const gnutls_datum_t * DATA, const gnutls_datum_t * SIGNATURE) PUBKEY: Holds the public key FLAGS: should be 0 for now DATA: holds the data to be signed SIGNATURE: contains the signature This function will verify the given signed data, using the parameters from the certificate. *Returns:* In case of a verification failure `GNUTLS_E_PK_SIG_VERIFY_FAILED' is returned, and a positive code on success. *Since:* 2.12.0 gnutls_pubkey_verify_hash ------------------------- -- Function: int gnutls_pubkey_verify_hash (gnutls_pubkey_t KEY, unsigned int FLAGS, const gnutls_datum_t * HASH, const gnutls_datum_t * SIGNATURE) KEY: Holds the certificate FLAGS: should be 0 for now HASH: holds the hash digest to be verified SIGNATURE: contains the signature This function will verify the given signed digest, using the parameters from the certificate. *Returns:* In case of a verification failure `GNUTLS_E_PK_SIG_VERIFY_FAILED' is returned, and a positive code on success. gnutls_record_check_pending --------------------------- -- Function: size_t gnutls_record_check_pending (gnutls_session_t SESSION) SESSION: is a `gnutls_session_t' structure. This function checks if there are any data to receive in the gnutls buffers. *Returns:* the size of that data or 0. gnutls_record_disable_padding ----------------------------- -- Function: void gnutls_record_disable_padding (gnutls_session_t SESSION) SESSION: is a `gnutls_session_t' structure. Used to disabled padding in TLS 1.0 and above. Normally you do not need to use this function, but there are buggy clients that complain if a server pads the encrypted data. This of course will disable protection against statistical attacks on the data. Normally only servers that require maximum compatibility with everything out there, need to call this function. gnutls_record_get_direction --------------------------- -- Function: int gnutls_record_get_direction (gnutls_session_t SESSION) SESSION: is a `gnutls_session_t' structure. This function provides information about the internals of the record protocol and is only useful if a prior gnutls function call (e.g. `gnutls_handshake()') was interrupted for some reason, that is, if a function returned `GNUTLS_E_INTERRUPTED' or `GNUTLS_E_AGAIN'. In such a case, you might want to call `select()' or `poll()' before calling the interrupted gnutls function again. To tell you whether a file descriptor should be selected for either reading or writing, `gnutls_record_get_direction()' returns 0 if the interrupted function was trying to read data, and 1 if it was trying to write data. *Returns:* 0 if trying to read data, 1 if trying to write data. gnutls_record_get_max_size -------------------------- -- Function: size_t gnutls_record_get_max_size (gnutls_session_t SESSION) SESSION: is a `gnutls_session_t' structure. Get the record size. The maximum record size is negotiated by the client after the first handshake message. *Returns:* The maximum record packet size in this connection. gnutls_record_recv ------------------ -- Function: ssize_t gnutls_record_recv (gnutls_session_t SESSION, void * DATA, size_t SIZEOFDATA) SESSION: is a `gnutls_session_t' structure. DATA: the buffer that the data will be read into SIZEOFDATA: the number of requested bytes This function has the similar semantics with `recv()'. The only difference is that it accepts a GnuTLS session, and uses different error codes. In the special case that a server requests a renegotiation, the client may receive an error code of `GNUTLS_E_REHANDSHAKE'. This message may be simply ignored, replied with an alert `GNUTLS_A_NO_RENEGOTIATION', or replied with a new handshake, depending on the client's will. If `EINTR' is returned by the internal push function (the default is `recv()') then `GNUTLS_E_INTERRUPTED' will be returned. If `GNUTLS_E_INTERRUPTED' or `GNUTLS_E_AGAIN' is returned, you must call this function again to get the data. See also `gnutls_record_get_direction()'. A server may also receive `GNUTLS_E_REHANDSHAKE' when a client has initiated a handshake. In that case the server can only initiate a handshake or terminate the connection. *Returns:* the number of bytes received and zero on EOF. A negative error code is returned in case of an error. The number of bytes received might be less than `sizeofdata'. gnutls_record_send ------------------ -- Function: ssize_t gnutls_record_send (gnutls_session_t SESSION, const void * DATA, size_t SIZEOFDATA) SESSION: is a `gnutls_session_t' structure. DATA: contains the data to send SIZEOFDATA: is the length of the data This function has the similar semantics with `send()'. The only difference is that it accepts a GnuTLS session, and uses different error codes. Note that if the send buffer is full, `send()' will block this function. See the `send()' documentation for full information. You can replace the default push function by using `gnutls_transport_set_ptr2()' with a call to `send()' with a MSG_DONTWAIT flag if blocking is a problem. If the EINTR is returned by the internal push function (the default is `send()'} then `GNUTLS_E_INTERRUPTED' will be returned. If `GNUTLS_E_INTERRUPTED' or `GNUTLS_E_AGAIN' is returned, you must call this function again, with the same parameters; alternatively you could provide a `NULL' pointer for data, and 0 for size. cf. `gnutls_record_get_direction()'. *Returns:* the number of bytes sent, or a negative error code. The number of bytes sent might be less than `sizeofdata'. The maximum number of bytes this function can send in a single call depends on the negotiated maximum record size. gnutls_record_set_max_size -------------------------- -- Function: ssize_t gnutls_record_set_max_size (gnutls_session_t SESSION, size_t SIZE) SESSION: is a `gnutls_session_t' structure. SIZE: is the new size This function sets the maximum record packet size in this connection. This property can only be set to clients. The server may choose not to accept the requested size. Acceptable values are 512(=2^9), 1024(=2^10), 2048(=2^11) and 4096(=2^12). The requested record size does get in effect immediately only while sending data. The receive part will take effect after a successful handshake. This function uses a TLS extension called 'max record size'. Not all TLS implementations use or even understand this extension. *Returns:* On success, `GNUTLS_E_SUCCESS' (zero) is returned, otherwise an error code is returned. gnutls_rehandshake ------------------ -- Function: int gnutls_rehandshake (gnutls_session_t SESSION) SESSION: is a `gnutls_session_t' structure. This function will renegotiate security parameters with the client. This should only be called in case of a server. This message informs the peer that we want to renegotiate parameters (perform a handshake). If this function succeeds (returns 0), you must call the `gnutls_handshake()' function in order to negotiate the new parameters. Since TLS is full duplex some application data might have been sent during peer's processing of this message. In that case one should call `gnutls_record_recv()' until GNUTLS_E_REHANDSHAKE is returned to clear any pending data. Care must be taken if rehandshake is mandatory to terminate if it does not start after some threshold. If the client does not wish to renegotiate parameters he will should with an alert message, thus the return code will be `GNUTLS_E_WARNING_ALERT_RECEIVED' and the alert will be `GNUTLS_A_NO_RENEGOTIATION'. A client may also choose to ignore this message. *Returns:* `GNUTLS_E_SUCCESS' on success, otherwise an error. gnutls_rnd ---------- -- Function: int gnutls_rnd (gnutls_rnd_level_t LEVEL, void * DATA, size_t LEN) LEVEL: a security level DATA: place to store random bytes LEN: The requested size This function will generate random data and store it to output buffer. *Returns:* Zero or a negative value on error. gnutls_rsa_export_get_modulus_bits ---------------------------------- -- Function: int gnutls_rsa_export_get_modulus_bits (gnutls_session_t SESSION) SESSION: is a gnutls session Get the export RSA parameter's modulus size. *Returns:* the bits used in the last RSA-EXPORT key exchange with the peer, or a negative value in case of error. gnutls_rsa_export_get_pubkey ---------------------------- -- Function: int gnutls_rsa_export_get_pubkey (gnutls_session_t SESSION, gnutls_datum_t * EXPONENT, gnutls_datum_t * MODULUS) SESSION: is a gnutls session EXPONENT: will hold the exponent. MODULUS: will hold the modulus. This function will return the peer's public key exponent and modulus used in the last RSA-EXPORT authentication. The output parameters must be freed with `gnutls_free()'. *Returns:* On success, `GNUTLS_E_SUCCESS' (0) is returned, otherwise an error code is returned. gnutls_rsa_params_cpy --------------------- -- Function: int gnutls_rsa_params_cpy (gnutls_rsa_params_t DST, gnutls_rsa_params_t SRC) DST: Is the destination structure, which should be initialized. SRC: Is the source structure This function will copy the RSA parameters structure from source to destination. *Returns:* `GNUTLS_E_SUCCESS' on success, or an negative error code. gnutls_rsa_params_deinit ------------------------ -- Function: void gnutls_rsa_params_deinit (gnutls_rsa_params_t RSA_PARAMS) RSA_PARAMS: Is a structure that holds the parameters This function will deinitialize the RSA parameters structure. gnutls_rsa_params_export_pkcs1 ------------------------------ -- Function: int gnutls_rsa_params_export_pkcs1 (gnutls_rsa_params_t PARAMS, gnutls_x509_crt_fmt_t FORMAT, unsigned char * PARAMS_DATA, size_t * PARAMS_DATA_SIZE) PARAMS: Holds the RSA parameters FORMAT: the format of output params. One of PEM or DER. PARAMS_DATA: will contain a PKCS1 RSAPublicKey structure PEM or DER encoded PARAMS_DATA_SIZE: holds the size of params_data (and will be replaced by the actual size of parameters) This function will export the given RSA parameters to a PKCS1 RSAPublicKey structure. If the buffer provided is not long enough to hold the output, then GNUTLS_E_SHORT_MEMORY_BUFFER will be returned. If the structure is PEM encoded, it will have a header of "BEGIN RSA PRIVATE KEY". *Returns:* `GNUTLS_E_SUCCESS' on success, or an negative error code. gnutls_rsa_params_export_raw ---------------------------- -- Function: int gnutls_rsa_params_export_raw (gnutls_rsa_params_t PARAMS, gnutls_datum_t * M, gnutls_datum_t * E, gnutls_datum_t * D, gnutls_datum_t * P, gnutls_datum_t * Q, gnutls_datum_t * U, unsigned int * BITS) PARAMS: a structure that holds the rsa parameters M: will hold the modulus E: will hold the public exponent D: will hold the private exponent P: will hold the first prime (p) Q: will hold the second prime (q) U: will hold the coefficient BITS: if non null will hold the prime's number of bits This function will export the RSA parameters found in the given structure. The new parameters will be allocated using `gnutls_malloc()' and will be stored in the appropriate datum. *Returns:* `GNUTLS_E_SUCCESS' on success, or an negative error code. gnutls_rsa_params_generate2 --------------------------- -- Function: int gnutls_rsa_params_generate2 (gnutls_rsa_params_t PARAMS, unsigned int BITS) PARAMS: The structure where the parameters will be stored BITS: is the prime's number of bits This function will generate new temporary RSA parameters for use in RSA-EXPORT ciphersuites. This function is normally slow. Note that if the parameters are to be used in export cipher suites the bits value should be 512 or less. Also note that the generation of new RSA parameters is only useful to servers. Clients use the parameters sent by the server, thus it's no use calling this in client side. *Returns:* `GNUTLS_E_SUCCESS' on success, or an negative error code. gnutls_rsa_params_import_pkcs1 ------------------------------ -- Function: int gnutls_rsa_params_import_pkcs1 (gnutls_rsa_params_t PARAMS, const gnutls_datum_t * PKCS1_PARAMS, gnutls_x509_crt_fmt_t FORMAT) PARAMS: A structure where the parameters will be copied to PKCS1_PARAMS: should contain a PKCS1 RSAPublicKey structure PEM or DER encoded FORMAT: the format of params. PEM or DER. This function will extract the RSAPublicKey found in a PKCS1 formatted structure. If the structure is PEM encoded, it should have a header of "BEGIN RSA PRIVATE KEY". *Returns:* `GNUTLS_E_SUCCESS' on success, or an negative error code. gnutls_rsa_params_import_raw ---------------------------- -- Function: int gnutls_rsa_params_import_raw (gnutls_rsa_params_t RSA_PARAMS, const gnutls_datum_t * M, const gnutls_datum_t * E, const gnutls_datum_t * D, const gnutls_datum_t * P, const gnutls_datum_t * Q, const gnutls_datum_t * U) RSA_PARAMS: Is a structure will hold the parameters M: holds the modulus E: holds the public exponent D: holds the private exponent P: holds the first prime (p) Q: holds the second prime (q) U: holds the coefficient This function will replace the parameters in the given structure. The new parameters should be stored in the appropriate gnutls_datum. *Returns:* `GNUTLS_E_SUCCESS' on success, or an negative error code. gnutls_rsa_params_init ---------------------- -- Function: int gnutls_rsa_params_init (gnutls_rsa_params_t * RSA_PARAMS) RSA_PARAMS: Is a structure that will hold the parameters This function will initialize the temporary RSA parameters structure. *Returns:* `GNUTLS_E_SUCCESS' on success, or an negative error code. gnutls_safe_renegotiation_status -------------------------------- -- Function: int gnutls_safe_renegotiation_status (gnutls_session_t SESSION) SESSION: is a `gnutls_session_t' structure. Can be used to check whether safe renegotiation is being used in the current session. *Returns:* 0 when safe renegotiation is not used and non zero when safe renegotiation is used. *Since:* 2.10.0 gnutls_sec_param_get_name ------------------------- -- Function: const char * gnutls_sec_param_get_name (gnutls_sec_param_t PARAM) PARAM: is a security parameter Convert a `gnutls_sec_param_t' value to a string. *Returns:* a pointer to a string that contains the name of the specified public key algorithm, or `NULL'. gnutls_sec_param_to_pk_bits --------------------------- -- Function: unsigned int gnutls_sec_param_to_pk_bits (gnutls_pk_algorithm_t ALGO, gnutls_sec_param_t PARAM) ALGO: is a public key algorithm PARAM: is a security parameter When generating private and public key pairs a difficult question is which size of "bits" the modulus will be in RSA and the group size in DSA. The easy answer is 1024, which is also wrong. This function will convert a human understandable security parameter to an appropriate size for the specific algorithm. *Returns:* The number of bits, or zero. gnutls_server_name_get ---------------------- -- Function: int gnutls_server_name_get (gnutls_session_t SESSION, void * DATA, size_t * DATA_LENGTH, unsigned int * TYPE, unsigned int INDX) SESSION: is a `gnutls_session_t' structure. DATA: will hold the data DATA_LENGTH: will hold the data length. Must hold the maximum size of data. TYPE: will hold the server name indicator type INDX: is the index of the server_name This function will allow you to get the name indication (if any), a client has sent. The name indication may be any of the enumeration gnutls_server_name_type_t. If `type' is GNUTLS_NAME_DNS, then this function is to be used by servers that support virtual hosting, and the data will be a null terminated UTF-8 string. If `data' has not enough size to hold the server name GNUTLS_E_SHORT_MEMORY_BUFFER is returned, and `data_length' will hold the required size. `index' is used to retrieve more than one server names (if sent by the client). The first server name has an index of 0, the second 1 and so on. If no name with the given index exists GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE is returned. *Returns:* On success, `GNUTLS_E_SUCCESS' (zero) is returned, otherwise an error code is returned. gnutls_server_name_set ---------------------- -- Function: int gnutls_server_name_set (gnutls_session_t SESSION, gnutls_server_name_type_t TYPE, const void * NAME, size_t NAME_LENGTH) SESSION: is a `gnutls_session_t' structure. TYPE: specifies the indicator type NAME: is a string that contains the server name. NAME_LENGTH: holds the length of name This function is to be used by clients that want to inform (via a TLS extension mechanism) the server of the name they connected to. This should be used by clients that connect to servers that do virtual hosting. The value of `name' depends on the `type' type. In case of `GNUTLS_NAME_DNS', an ASCII zero-terminated domain name string, without the trailing dot, is expected. IPv4 or IPv6 addresses are not permitted. *Returns:* On success, `GNUTLS_E_SUCCESS' (zero) is returned, otherwise an error code is returned. gnutls_session_channel_binding ------------------------------ -- Function: int gnutls_session_channel_binding (gnutls_session_t SESSION, gnutls_channel_binding_t CBTYPE, gnutls_datum_t * CB) SESSION: is a `gnutls_session_t' structure. CBTYPE: an `gnutls_channel_binding_t' enumeration type CB: output buffer array with data Extract given channel binding data of the `cbtype' (e.g., `GNUTLS_CB_TLS_UNIQUE') type. *Returns:* `GNUTLS_E_SUCCESS' on success, `GNUTLS_E_UNIMPLEMENTED_FEATURE' if the `cbtype' is unsupported, `GNUTLS_E_CHANNEL_BINDING_NOT_AVAILABLE' if the data is not currently available, or an error code. *Since:* 2.12.0 gnutls_session_enable_compatibility_mode ---------------------------------------- -- Function: void gnutls_session_enable_compatibility_mode (gnutls_session_t SESSION) SESSION: is a `gnutls_session_t' structure. This function can be used to disable certain (security) features in TLS in order to maintain maximum compatibility with buggy clients. It is equivalent to calling: `gnutls_record_disable_padding()' Normally only servers that require maximum compatibility with everything out there, need to call this function. gnutls_session_get_data2 ------------------------ -- Function: int gnutls_session_get_data2 (gnutls_session_t SESSION, gnutls_datum_t * DATA) SESSION: is a `gnutls_session_t' structure. DATA: is a pointer to a datum that will hold the session. Returns all session parameters, in order to support resuming. The client should call this, and keep the returned session, if he wants to resume that current version later by calling `gnutls_session_set_data()'. This function must be called after a successful handshake. The returned datum must be freed with `gnutls_free()'. Resuming sessions is really useful and speedups connections after a successful one. *Returns:* On success, `GNUTLS_E_SUCCESS' (0) is returned, otherwise an error code is returned. gnutls_session_get_data ----------------------- -- Function: int gnutls_session_get_data (gnutls_session_t SESSION, void * SESSION_DATA, size_t * SESSION_DATA_SIZE) SESSION: is a `gnutls_session_t' structure. SESSION_DATA: is a pointer to space to hold the session. SESSION_DATA_SIZE: is the session_data's size, or it will be set by the function. Returns all session parameters, in order to support resuming. The client should call this, and keep the returned session, if he wants to resume that current version later by calling `gnutls_session_set_data()' This function must be called after a successful handshake. Resuming sessions is really useful and speedups connections after a successful one. *Returns:* On success, `GNUTLS_E_SUCCESS' (0) is returned, otherwise an error code is returned. gnutls_session_get_id --------------------- -- Function: int gnutls_session_get_id (gnutls_session_t SESSION, void * SESSION_ID, size_t * SESSION_ID_SIZE) SESSION: is a `gnutls_session_t' structure. SESSION_ID: is a pointer to space to hold the session id. SESSION_ID_SIZE: is the session id's size, or it will be set by the function. Returns the current session id. This can be used if you want to check if the next session you tried to resume was actually resumed. This is because resumed sessions have the same sessionID with the original session. Session id is some data set by the server, that identify the current session. In TLS 1.0 and SSL 3.0 session id is always less than 32 bytes. *Returns:* On success, `GNUTLS_E_SUCCESS' (0) is returned, otherwise an error code is returned. gnutls_session_get_ptr ---------------------- -- Function: void * gnutls_session_get_ptr (gnutls_session_t SESSION) SESSION: is a `gnutls_session_t' structure. Get user pointer for session. Useful in callbacks. This is the pointer set with `gnutls_session_set_ptr()'. *Returns:* the user given pointer from the session structure, or `NULL' if it was never set. gnutls_session_is_resumed ------------------------- -- Function: int gnutls_session_is_resumed (gnutls_session_t SESSION) SESSION: is a `gnutls_session_t' structure. Check whether session is resumed or not. *Returns:* non zero if this session is resumed, or a zero if this is a new session. gnutls_session_set_data ----------------------- -- Function: int gnutls_session_set_data (gnutls_session_t SESSION, const void * SESSION_DATA, size_t SESSION_DATA_SIZE) SESSION: is a `gnutls_session_t' structure. SESSION_DATA: is a pointer to space to hold the session. SESSION_DATA_SIZE: is the session's size Sets all session parameters, in order to resume a previously established session. The session data given must be the one returned by `gnutls_session_get_data()'. This function should be called before `gnutls_handshake()'. Keep in mind that session resuming is advisory. The server may choose not to resume the session, thus a full handshake will be performed. *Returns:* On success, `GNUTLS_E_SUCCESS' (0) is returned, otherwise an error code is returned. gnutls_session_set_ptr ---------------------- -- Function: void gnutls_session_set_ptr (gnutls_session_t SESSION, void * PTR) SESSION: is a `gnutls_session_t' structure. PTR: is the user pointer This function will set (associate) the user given pointer `ptr' to the session structure. This is pointer can be accessed with `gnutls_session_get_ptr()'. gnutls_session_ticket_enable_client ----------------------------------- -- Function: int gnutls_session_ticket_enable_client (gnutls_session_t SESSION) SESSION: is a `gnutls_session_t' structure. Request that the client should attempt session resumption using SessionTicket. *Returns:* On success, `GNUTLS_E_SUCCESS' (0) is returned, or an error code. *Since:* 2.10.0 gnutls_session_ticket_enable_server ----------------------------------- -- Function: int gnutls_session_ticket_enable_server (gnutls_session_t SESSION, const gnutls_datum_t * KEY) SESSION: is a `gnutls_session_t' structure. KEY: key to encrypt session parameters. Request that the server should attempt session resumption using SessionTicket. `key' must be initialized with `gnutls_session_ticket_key_generate()'. *Returns:* On success, `GNUTLS_E_SUCCESS' (0) is returned, or an error code. *Since:* 2.10.0 gnutls_session_ticket_key_generate ---------------------------------- -- Function: int gnutls_session_ticket_key_generate (gnutls_datum_t * KEY) KEY: is a pointer to a `gnutls_datum_t' which will contain a newly created key. Generate a random key to encrypt security parameters within SessionTicket. *Returns:* On success, `GNUTLS_E_SUCCESS' (0) is returned, or an error code. *Since:* 2.10.0 gnutls_set_default_export_priority ---------------------------------- -- Function: int gnutls_set_default_export_priority (gnutls_session_t SESSION) SESSION: is a `gnutls_session_t' structure. Sets some default priority on the ciphers, key exchange methods, macs and compression methods. This function also includes weak algorithms. *This is the same as calling:* gnutls_priority_set_direct (session, "EXPORT", NULL); This function is kept around for backwards compatibility, but because of its wide use it is still fully supported. If you wish to allow users to provide a string that specify which ciphers to use (which is recommended), you should use `gnutls_priority_set_direct()' or `gnutls_priority_set()' instead. *Returns:* `GNUTLS_E_SUCCESS' on success, or an error code. gnutls_set_default_priority --------------------------- -- Function: int gnutls_set_default_priority (gnutls_session_t SESSION) SESSION: is a `gnutls_session_t' structure. Sets some default priority on the ciphers, key exchange methods, macs and compression methods. *This is the same as calling:* gnutls_priority_set_direct (session, "NORMAL", NULL); This function is kept around for backwards compatibility, but because of its wide use it is still fully supported. If you wish to allow users to provide a string that specify which ciphers to use (which is recommended), you should use `gnutls_priority_set_direct()' or `gnutls_priority_set()' instead. *Returns:* `GNUTLS_E_SUCCESS' on success, or an error code. gnutls_sign_algorithm_get_name ------------------------------ -- Function: const char * gnutls_sign_algorithm_get_name (gnutls_sign_algorithm_t SIGN) SIGN: is a sign algorithm Convert a `gnutls_sign_algorithm_t' value to a string. *Returns:* a string that contains the name of the specified sign algorithm, or `NULL'. gnutls_sign_algorithm_get_requested ----------------------------------- -- Function: int gnutls_sign_algorithm_get_requested (gnutls_session_t SESSION, size_t INDX, gnutls_sign_algorithm_t * ALGO) SESSION: is a `gnutls_session_t' structure. INDX: is an index of the signature algorithm to return ALGO: the returned certificate type will be stored there Returns the signature algorithm specified by index that was requested by the peer. If the specified index has no data available this function returns `GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE'. If the negotiated TLS version does not support signature algorithms then `GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE' will be returned even for the first index. The first index is 0. This function is useful in the certificate callback functions to assist in selecting the correct certificate. *Returns:* On success, `GNUTLS_E_SUCCESS' (0) is returned, otherwise an error code is returned. *Since:* 2.10.0 gnutls_sign_callback_get ------------------------ -- Function: gnutls_sign_func gnutls_sign_callback_get (gnutls_session_t SESSION, void ** USERDATA) SESSION: is a gnutls session USERDATA: if non-`NULL', will be set to abstract callback pointer. Retrieve the callback function, and its userdata pointer. *Returns:* The function pointer set by `gnutls_sign_callback_set()', or if not set, `NULL'. *Deprecated:* Use the PKCS 11 interfaces instead. gnutls_sign_callback_set ------------------------ -- Function: void gnutls_sign_callback_set (gnutls_session_t SESSION, gnutls_sign_func SIGN_FUNC, void * USERDATA) SESSION: is a gnutls session SIGN_FUNC: function pointer to application's sign callback. USERDATA: void pointer that will be passed to sign callback. Set the callback function. The function must have this prototype: typedef int (*gnutls_sign_func) (gnutls_session_t session, void *userdata, gnutls_certificate_type_t cert_type, const gnutls_datum_t * cert, const gnutls_datum_t * hash, gnutls_datum_t * signature); The `userdata' parameter is passed to the `sign_func' verbatim, and can be used to store application-specific data needed in the callback function. See also `gnutls_sign_callback_get()'. *Deprecated:* Use the PKCS 11 interfaces instead. gnutls_sign_get_id ------------------ -- Function: gnutls_sign_algorithm_t gnutls_sign_get_id (const char * NAME) NAME: is a MAC algorithm name The names are compared in a case insensitive way. *Returns:* return a `gnutls_sign_algorithm_t' value corresponding to the specified cipher, or `GNUTLS_SIGN_UNKNOWN' on error. gnutls_sign_get_name -------------------- -- Function: const char * gnutls_sign_get_name (gnutls_sign_algorithm_t ALGORITHM) ALGORITHM: is a public key signature algorithm Convert a `gnutls_sign_algorithm_t' value to a string. *Returns:* a pointer to a string that contains the name of the specified public key signature algorithm, or `NULL'. *Since:* 2.6.0 gnutls_sign_list ---------------- -- Function: const gnutls_sign_algorithm_t * gnutls_sign_list ( VOID) Get a list of supported public key signature algorithms. *Returns:* a zero-terminated list of `gnutls_sign_algorithm_t' integers indicating the available ciphers. gnutls_srp_allocate_client_credentials -------------------------------------- -- Function: int gnutls_srp_allocate_client_credentials (gnutls_srp_client_credentials_t * SC) SC: is a pointer to a `gnutls_srp_server_credentials_t' structure. This structure is complex enough to manipulate directly thus this helper function is provided in order to allocate it. *Returns:* On success, `GNUTLS_E_SUCCESS' (0) is returned, or an error code. gnutls_srp_allocate_server_credentials -------------------------------------- -- Function: int gnutls_srp_allocate_server_credentials (gnutls_srp_server_credentials_t * SC) SC: is a pointer to a `gnutls_srp_server_credentials_t' structure. This structure is complex enough to manipulate directly thus this helper function is provided in order to allocate it. *Returns:* On success, `GNUTLS_E_SUCCESS' (0) is returned, or an error code. gnutls_srp_base64_decode_alloc ------------------------------ -- Function: int gnutls_srp_base64_decode_alloc (const gnutls_datum_t * B64_DATA, gnutls_datum_t * RESULT) B64_DATA: contains the encoded data RESULT: the place where decoded data lie This function will decode the given encoded data. The decoded data will be allocated, and stored into result. It will decode using the base64 algorithm as used in libsrp. You should use `gnutls_free()' to free the returned data. Warning! This base64 encoding is not the "standard" encoding, so do not use it for non-SRP purposes. *Returns:* 0 on success, or an error code. gnutls_srp_base64_decode ------------------------ -- Function: int gnutls_srp_base64_decode (const gnutls_datum_t * B64_DATA, char * RESULT, size_t * RESULT_SIZE) B64_DATA: contain the encoded data RESULT: the place where decoded data will be copied RESULT_SIZE: holds the size of the result This function will decode the given encoded data, using the base64 encoding found in libsrp. Note that `b64_data' should be null terminated. Warning! This base64 encoding is not the "standard" encoding, so do not use it for non-SRP purposes. *Returns:* `GNUTLS_E_SHORT_MEMORY_BUFFER' if the buffer given is not long enough, or 0 on success. gnutls_srp_base64_encode_alloc ------------------------------ -- Function: int gnutls_srp_base64_encode_alloc (const gnutls_datum_t * DATA, gnutls_datum_t * RESULT) DATA: contains the raw data RESULT: will hold the newly allocated encoded data This function will convert the given data to printable data, using the base64 encoding. This is the encoding used in SRP password files. This function will allocate the required memory to hold the encoded data. You should use `gnutls_free()' to free the returned data. Warning! This base64 encoding is not the "standard" encoding, so do not use it for non-SRP purposes. *Returns:* 0 on success, or an error code. gnutls_srp_base64_encode ------------------------ -- Function: int gnutls_srp_base64_encode (const gnutls_datum_t * DATA, char * RESULT, size_t * RESULT_SIZE) DATA: contain the raw data RESULT: the place where base64 data will be copied RESULT_SIZE: holds the size of the result This function will convert the given data to printable data, using the base64 encoding, as used in the libsrp. This is the encoding used in SRP password files. If the provided buffer is not long enough GNUTLS_E_SHORT_MEMORY_BUFFER is returned. Warning! This base64 encoding is not the "standard" encoding, so do not use it for non-SRP purposes. *Returns:* `GNUTLS_E_SHORT_MEMORY_BUFFER' if the buffer given is not long enough, or 0 on success. gnutls_srp_free_client_credentials ---------------------------------- -- Function: void gnutls_srp_free_client_credentials (gnutls_srp_client_credentials_t SC) SC: is a `gnutls_srp_client_credentials_t' structure. This structure is complex enough to manipulate directly thus this helper function is provided in order to free (deallocate) it. gnutls_srp_free_server_credentials ---------------------------------- -- Function: void gnutls_srp_free_server_credentials (gnutls_srp_server_credentials_t SC) SC: is a `gnutls_srp_server_credentials_t' structure. This structure is complex enough to manipulate directly thus this helper function is provided in order to free (deallocate) it. gnutls_srp_server_get_username ------------------------------ -- Function: const char * gnutls_srp_server_get_username (gnutls_session_t SESSION) SESSION: is a gnutls session This function will return the username of the peer. This should only be called in case of SRP authentication and in case of a server. Returns NULL in case of an error. *Returns:* SRP username of the peer, or NULL in case of error. gnutls_srp_set_client_credentials_function ------------------------------------------ -- Function: void gnutls_srp_set_client_credentials_function (gnutls_srp_client_credentials_t CRED, gnutls_srp_client_credentials_function * FUNC) CRED: is a `gnutls_srp_server_credentials_t' structure. FUNC: is the callback function This function can be used to set a callback to retrieve the username and password for client SRP authentication. The callback's function form is: int (*callback)(gnutls_session_t, char** username, char**password); The `username' and `password' must be allocated using `gnutls_malloc()'. `username' and `password' should be ASCII strings or UTF-8 strings prepared using the "SASLprep" profile of "stringprep". The callback function will be called once per handshake before the initial hello message is sent. The callback should not return a negative error code the second time called, since the handshake procedure will be aborted. The callback function should return 0 on success. -1 indicates an error. gnutls_srp_set_client_credentials --------------------------------- -- Function: int gnutls_srp_set_client_credentials (gnutls_srp_client_credentials_t RES, const char * USERNAME, const char * PASSWORD) RES: is a `gnutls_srp_client_credentials_t' structure. USERNAME: is the user's userid PASSWORD: is the user's password This function sets the username and password, in a `gnutls_srp_client_credentials_t' structure. Those will be used in SRP authentication. `username' and `password' should be ASCII strings or UTF-8 strings prepared using the "SASLprep" profile of "stringprep". *Returns:* On success, `GNUTLS_E_SUCCESS' (0) is returned, or an error code. gnutls_srp_set_prime_bits ------------------------- -- Function: void gnutls_srp_set_prime_bits (gnutls_session_t SESSION, unsigned int BITS) SESSION: is a `gnutls_session_t' structure. BITS: is the number of bits This function sets the minimum accepted number of bits, for use in an SRP key exchange. If zero, the default 2048 bits will be used. In the client side it sets the minimum accepted number of bits. If a server sends a prime with less bits than that `GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER' will be returned by the handshake. This function has no effect in server side. *Since:* 2.6.0 gnutls_srp_set_server_credentials_file -------------------------------------- -- Function: int gnutls_srp_set_server_credentials_file (gnutls_srp_server_credentials_t RES, const char * PASSWORD_FILE, const char * PASSWORD_CONF_FILE) RES: is a `gnutls_srp_server_credentials_t' structure. PASSWORD_FILE: is the SRP password file (tpasswd) PASSWORD_CONF_FILE: is the SRP password conf file (tpasswd.conf) This function sets the password files, in a `gnutls_srp_server_credentials_t' structure. Those password files hold usernames and verifiers and will be used for SRP authentication. *Returns:* On success, `GNUTLS_E_SUCCESS' (0) is returned, or an error code. gnutls_srp_set_server_credentials_function ------------------------------------------ -- Function: void gnutls_srp_set_server_credentials_function (gnutls_srp_server_credentials_t CRED, gnutls_srp_server_credentials_function * FUNC) CRED: is a `gnutls_srp_server_credentials_t' structure. FUNC: is the callback function This function can be used to set a callback to retrieve the user's SRP credentials. The callback's function form is: int (*callback)(gnutls_session_t, const char* username, gnutls_datum_t* salt, gnutls_datum_t *verifier, gnutls_datum_t* g, gnutls_datum_t* n); `username' contains the actual username. The `salt', `verifier', `generator' and `prime' must be filled in using the `gnutls_malloc()'. For convenience `prime' and `generator' may also be one of the static parameters defined in extra.h. In case the callback returned a negative number then gnutls will assume that the username does not exist. In order to prevent attackers from guessing valid usernames, if a user does not exist, g and n values should be filled in using a random user's parameters. In that case the callback must return the special value (1). The callback function will only be called once per handshake. The callback function should return 0 on success, while -1 indicates an error. gnutls_srp_verifier ------------------- -- Function: int gnutls_srp_verifier (const char * USERNAME, const char * PASSWORD, const gnutls_datum_t * SALT, const gnutls_datum_t * GENERATOR, const gnutls_datum_t * PRIME, gnutls_datum_t * RES) USERNAME: is the user's name PASSWORD: is the user's password SALT: should be some randomly generated bytes GENERATOR: is the generator of the group PRIME: is the group's prime RES: where the verifier will be stored. This function will create an SRP verifier, as specified in RFC2945. The `prime' and `generator' should be one of the static parameters defined in gnutls/extra.h or may be generated using the libgcrypt functions `gcry_prime_generate()' and `gcry_prime_group_generator()'. The verifier will be allocated with `malloc' and will be stored in `res' using binary format. *Returns:* On success, `GNUTLS_E_SUCCESS' (0) is returned, or an error code. gnutls_strerror_name -------------------- -- Function: const char * gnutls_strerror_name (int ERROR) ERROR: is an error returned by a gnutls function. Return the GnuTLS error code define as a string. For example, gnutls_strerror_name (GNUTLS_E_DH_PRIME_UNACCEPTABLE) will return the string "GNUTLS_E_DH_PRIME_UNACCEPTABLE". *Returns:* A string corresponding to the symbol name of the error code. *Since:* 2.6.0 gnutls_strerror --------------- -- Function: const char * gnutls_strerror (int ERROR) ERROR: is a GnuTLS error code, a negative value This function is similar to strerror. The difference is that it accepts an error number returned by a gnutls function; In case of an unknown error a descriptive string is sent instead of `NULL'. Error codes are always a negative value. *Returns:* A string explaining the GnuTLS error message. gnutls_supplemental_get_name ---------------------------- -- Function: const char * gnutls_supplemental_get_name (gnutls_supplemental_data_format_type_t TYPE) TYPE: is a supplemental data format type Convert a `gnutls_supplemental_data_format_type_t' value to a string. *Returns:* a string that contains the name of the specified supplemental data format type, or `NULL' for unknown types. gnutls_transport_get_ptr2 ------------------------- -- Function: void gnutls_transport_get_ptr2 (gnutls_session_t SESSION, gnutls_transport_ptr_t * RECV_PTR, gnutls_transport_ptr_t * SEND_PTR) SESSION: is a `gnutls_session_t' structure. RECV_PTR: will hold the value for the pull function SEND_PTR: will hold the value for the push function Used to get the arguments of the transport functions (like PUSH and PULL). These should have been set using `gnutls_transport_set_ptr2()'. gnutls_transport_get_ptr ------------------------ -- Function: gnutls_transport_ptr_t gnutls_transport_get_ptr (gnutls_session_t SESSION) SESSION: is a `gnutls_session_t' structure. Used to get the first argument of the transport function (like PUSH and PULL). This must have been set using `gnutls_transport_set_ptr()'. *Returns:* first argument of the transport function. gnutls_transport_set_errno_function ----------------------------------- -- Function: void gnutls_transport_set_errno_function (gnutls_session_t SESSION, gnutls_errno_func ERRNO_FUNC) SESSION: is a `gnutls_session_t' structure. ERRNO_FUNC: a callback function similar to `write()' This is the function where you set a function to retrieve errno after a failed push or pull operation. errno_func is of the form, int (*gnutls_errno_func)(gnutls_transport_ptr_t); and should return the errno. gnutls_transport_set_errno -------------------------- -- Function: void gnutls_transport_set_errno (gnutls_session_t SESSION, int ERR) SESSION: is a `gnutls_session_t' structure. ERR: error value to store in session-specific errno variable. Store `err' in the session-specific errno variable. Useful values for `err' is EAGAIN and EINTR, other values are treated will be treated as real errors in the push/pull function. This function is useful in replacement push/pull functions set by gnutls_transport_set_push_function and gnutls_transport_set_pullpush_function under Windows, where the replacement push/pull may not have access to the same `errno' variable that is used by GnuTLS (e.g., the application is linked to msvcr71.dll and gnutls is linked to msvcrt.dll). If you don't have the `session' variable easily accessible from the push/pull function, and don't worry about thread conflicts, you can also use `gnutls_transport_set_global_errno()'. gnutls_transport_set_global_errno --------------------------------- -- Function: void gnutls_transport_set_global_errno (int ERR) ERR: error value to store in global errno variable. Store `err' in the global errno variable. Useful values for `err' is EAGAIN and EINTR, other values are treated will be treated as real errors in the push/pull function. This function is useful in replacement push/pull functions set by gnutls_transport_set_push_function and gnutls_transport_set_pullpush_function under Windows, where the replacement push/pull may not have access to the same `errno' variable that is used by GnuTLS (e.g., the application is linked to msvcr71.dll and gnutls is linked to msvcrt.dll). Whether this function is thread safe or not depends on whether the global variable errno is thread safe, some system libraries make it a thread-local variable. When feasible, using the guaranteed thread-safe `gnutls_transport_set_errno()' may be better. gnutls_transport_set_lowat -------------------------- -- Function: void gnutls_transport_set_lowat (gnutls_session_t SESSION, int NUM) SESSION: is a `gnutls_session_t' structure. NUM: is the low water value. Used to set the lowat value in order for select to check if there are pending data to socket buffer. Used only if you have changed the default low water value (default is 1). Normally you will not need that function. This function is only useful if using berkeley style sockets. Otherwise it must be called and set lowat to zero. gnutls_transport_set_ptr2 ------------------------- -- Function: void gnutls_transport_set_ptr2 (gnutls_session_t SESSION, gnutls_transport_ptr_t RECV_PTR, gnutls_transport_ptr_t SEND_PTR) SESSION: is a `gnutls_session_t' structure. RECV_PTR: is the value for the pull function SEND_PTR: is the value for the push function Used to set the first argument of the transport function (like PUSH and PULL). In berkeley style sockets this function will set the connection handle. With this function you can use two different pointers for receiving and sending. gnutls_transport_set_ptr ------------------------ -- Function: void gnutls_transport_set_ptr (gnutls_session_t SESSION, gnutls_transport_ptr_t PTR) SESSION: is a `gnutls_session_t' structure. PTR: is the value. Used to set the first argument of the transport function (like PUSH and PULL). In berkeley style sockets this function will set the connection handle. gnutls_transport_set_pull_function ---------------------------------- -- Function: void gnutls_transport_set_pull_function (gnutls_session_t SESSION, gnutls_pull_func PULL_FUNC) SESSION: is a `gnutls_session_t' structure. PULL_FUNC: a callback function similar to `read()' This is the function where you set a function for gnutls to receive data. Normally, if you use berkeley style sockets, do not need to use this function since the default (recv(2)) will probably be ok. PULL_FUNC is of the form, ssize_t (*gnutls_pull_func)(gnutls_transport_ptr_t, void*, size_t); gnutls_transport_set_push_function ---------------------------------- -- Function: void gnutls_transport_set_push_function (gnutls_session_t SESSION, gnutls_push_func PUSH_FUNC) SESSION: is a `gnutls_session_t' structure. PUSH_FUNC: a callback function similar to `write()' This is the function where you set a push function for gnutls to use in order to send data. If you are going to use berkeley style sockets, you do not need to use this function since the default (send(2)) will probably be ok. Otherwise you should specify this function for gnutls to be able to send data. PUSH_FUNC is of the form, ssize_t (*gnutls_push_func)(gnutls_transport_ptr_t, const void*, size_t); gnutls_transport_set_vec_push_function -------------------------------------- -- Function: void gnutls_transport_set_vec_push_function (gnutls_session_t SESSION, gnutls_vec_push_func VEC_FUNC) SESSION: is a `gnutls_session_t' structure. VEC_FUNC: a callback function similar to `writev()' This is the function where you set a push function for gnutls to use in order to send data. If you are going to use berkeley style sockets, you do not need to use this function since the default (send(2)) will probably be ok. Otherwise you should specify this function for gnutls to be able to send data. PUSH_FUNC is of the form, ssize_t (*gnutls_push_func)(gnutls_transport_ptr_t, const void*, size_t); gnutls_x509_crq_set_pubkey -------------------------- -- Function: int gnutls_x509_crq_set_pubkey (gnutls_x509_crq_t CRQ, gnutls_pubkey_t KEY) CRQ: should contain a `gnutls_x509_crq_t' structure KEY: holds a public key This function will set the public parameters from the given public key to the request. *Returns:* On success, `GNUTLS_E_SUCCESS' is returned, otherwise a negative error value. gnutls_x509_crt_import_pkcs11_url --------------------------------- -- Function: int gnutls_x509_crt_import_pkcs11_url (gnutls_x509_crt_t CRT, const char * URL, unsigned int FLAGS) CRT: A certificate of type `gnutls_x509_crt_t' URL: A PKCS 11 url FLAGS: One of GNUTLS_PKCS11_OBJ_* flags This function will import a PKCS 11 certificate directly from a token without involving the `gnutls_pkcs11_obj_t' structure. This function will fail if the certificate stored is not of X.509 type. *Returns:* On success, `GNUTLS_E_SUCCESS' is returned, otherwise a negative error value. gnutls_x509_crt_import_pkcs11 ----------------------------- -- Function: int gnutls_x509_crt_import_pkcs11 (gnutls_x509_crt_t CRT, gnutls_pkcs11_obj_t PKCS11_CRT) CRT: A certificate of type `gnutls_x509_crt_t' PKCS11_CRT: A PKCS 11 object that contains a certificate This function will import a PKCS 11 certificate to a `gnutls_x509_crt_t' structure. *Returns:* On success, `GNUTLS_E_SUCCESS' is returned, otherwise a negative error value. gnutls_x509_crt_list_import_pkcs11 ---------------------------------- -- Function: int gnutls_x509_crt_list_import_pkcs11 (gnutls_x509_crt_t * CERTS, unsigned int CERT_MAX, gnutls_pkcs11_obj_t * const OBJS, unsigned int FLAGS) CERTS: A list of certificates of type `gnutls_x509_crt_t' CERT_MAX: The maximum size of the list OBJS: A list of PKCS 11 objects FLAGS: 0 for now This function will import a PKCS 11 certificate list to a list of `gnutls_x509_crt_t' structure. These must not be initialized. *Returns:* On success, `GNUTLS_E_SUCCESS' is returned, otherwise a negative error value. gnutls_x509_crt_set_pubkey -------------------------- -- Function: int gnutls_x509_crt_set_pubkey (gnutls_x509_crt_t CRT, gnutls_pubkey_t KEY) CRT: should contain a `gnutls_x509_crt_t' structure KEY: holds a public key This function will set the public parameters from the given public key to the request. *Returns:* On success, `GNUTLS_E_SUCCESS' is returned, otherwise a negative error value.