Table of Contents ***************** GNU Simple Authentication and Security Layer 1 Introduction 1.1 Getting Started 1.2 Features 1.3 SASL Overview 1.4 Requirements 1.5 Supported Platforms 1.6 Getting help 1.7 Commercial Support 1.8 Downloading and Installing 1.8.1 Installing under Windows 1.9 Bug Reports 1.10 Contributing 2 Preparation 2.1 Header 2.2 Initialization 2.3 Version Check 2.4 Building the source 2.5 Autoconf tests 2.5.1 Autoconf test via `pkg-config' 2.5.2 Standalone Autoconf test using Libtool 3 Using the Library 3.1 Choosing a mechanism 3.2 Using a callback 4 Properties 5 Mechanisms 5.1 The EXTERNAL mechanism 5.2 The ANONYMOUS mechanism 5.3 The PLAIN mechanism 5.4 The LOGIN mechanism 5.5 The CRAM-MD5 mechanism 5.6 The DIGEST-MD5 mechanism 5.7 The NTLM mechanism 5.8 The SECURID mechanism 5.9 The GSSAPI mechanism 5.10 The KERBEROS_V5 mechanism 6 Global Functions 7 Callback Functions 8 Property Functions 9 Session Functions 10 Utilities 11 Memory Handling 12 Error Handling 12.1 Error values 12.2 Error strings 13 Examples 13.1 Example 1 13.2 Example 2 13.3 Example 3 13.4 Example 4 14 Acknowledgements 15 Invoking gsasl Appendix A Protocol Clarifications A.1 Use of SASLprep in CRAM-MD5 A.2 Use of SASLprep in LOGIN Appendix B Old Functions B.1 Obsolete callback function prototypes Appendix C Copying Information C.1 GNU Free Documentation License C.2 GNU Lesser General Public License C.3 GNU General Public License Function and Data Index Concept Index GNU Simple Authentication and Security Layer ******************************************** This manual was last updated 11 April 2008 for version 0.2.27 of GNU SASL. Copyright (C) 2002, 2003, 2004, 2005, 2006, 2007, 2008 Simon Josefsson. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 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". 1 Introduction ************** GNU SASL is an implementation of the Simple Authentication and Security Layer framework and a few common SASL mechanisms. SASL is used by network servers (e.g., IMAP, SMTP) to request authentication from clients, and in clients to authenticate against servers. GNU SASL consists of a library (`libgsasl'), a command line utility (`gsasl') to access the library from the shell, and a manual. The library includes support for the framework (with authentication functions and application data privacy and integrity functions) and at least partial support for the CRAM-MD5, EXTERNAL, GSSAPI, ANONYMOUS, PLAIN, SECURID, DIGEST-MD5, LOGIN, and NTLM mechanisms. The library is easily ported because it does not do network communication by itself, but rather leaves it up to the calling application. The library is flexible with regards to the authorization infrastructure used, as it utilize a callback into the application to decide whether a user is authorized or not. GNU SASL is developed for the GNU/Linux system, but runs on over 20 platforms including most major Unix platforms and Windows, and many kind of devices including iPAQ handhelds and S/390 mainframes. GNU SASL is written in pure ANSI C89 to be portable to embedded and otherwise limited platforms. The entire library, with full support for ANONYMOUS, EXTERNAL, PLAIN, LOGIN and CRAM-MD5, and the front-end that support client and server mode, and the IMAP and SMTP protocols, fits in under 60kb on an Intel x86 platform, without any modifications to the code. (This figure was accurate as of version 0.0.13.) The library is licensed under the GNU Lesser General Public License version 2.1. The command-line application (src/), examples (examples/), self-test suite (tests/) are licensed under the GNU General Public License license version 3.0. The documentation (doc/) is licensed under the GNU Free Documentation License version 1.2. Illustration 1.1: Logical overview showing how applications use authentication mechanisms through an abstract interface. 1.1 Getting Started =================== This manual documents the GNU SASL Library programming interface. All functions and data types provided by the library are explained. The reader is assumed to possess basic familiarity with SASL and network programming in C or C++. This manual can be used in several ways. If read from the beginning to the end, it gives a good introduction into the library and how it can be used in an application. Forward references are included where necessary. Later on, the manual can be used as a reference manual to get just the information needed about any particular interface of the library. Experienced programmers might want to start looking at the examples at the end of the manual, and then only read up those parts of the interface which are unclear. 1.2 Features ============ GNU SASL might have a couple of advantages over other libraries doing a similar job. It's Free Software Anybody can use, modify, and redistribute it under the terms of the GNU General Public License version 3.0. The library can also be distributed under the GNU Lesser General Public License version 2.1. It's thread-safe No global variables are used and multiple library handles and session handles may be used in parallel. It's internationalized It handles non-ASCII username and passwords and user visible strings used in the library (error messages) can be translated into the users' language. It's portable It should work on all Unix like operating systems, including Windows. The library itself should be portable to any C89 system, not even POSIX is required. Note that the library do not implement any policy to decide whether a certain user is "authenticated" or "authorized" or not. Rather, it uses a callback into the application to answer these questions. 1.3 SASL Overview ================= This section describes SASL from a protocol point of view. The Simple Authentication and Security Layer (SASL) is a method for adding authentication support to connection-based protocols. A protocol includes a command for identifying and authenticating a user to a server and for optionally negotiating a security layer for subsequent protocol interactions. The command has a required argument identifying a SASL mechanism. SASL mechanisms are named by strings, from 1 to 20 characters in length, consisting of upper-case letters, digits, hyphens, and/or underscores. If a server supports the requested mechanism, it initiates an authentication protocol exchange. This consists of a series of server challenges and client responses that are specific to the requested mechanism. The challenges and responses are defined by the mechanisms as binary tokens of arbitrary length. The protocol's profile then specifies how these binary tokens are then encoded for transfer over the connection. After receiving the authentication command or any client response, a server may issue a challenge, indicate failure, or indicate completion. The protocol's profile specifies how the server indicates which of the above it is doing. After receiving a challenge, a client may issue a response or abort the exchange. The protocol's profile specifies how the client indicates which of the above it is doing. During the authentication protocol exchange, the mechanism performs authentication, transmits an authorization identity (frequently known as a userid) from the client to server, and negotiates the use of a mechanism-specific security layer. If the use of a security layer is agreed upon, then the mechanism must also define or negotiate the maximum cipher-text buffer size that each side is able to receive. The transmitted authorization identity may be different than the identity in the client's authentication credentials. This permits agents such as proxy servers to authenticate using their own credentials, yet request the access privileges of the identity for which they are proxying. With any mechanism, transmitting an authorization identity of the empty string directs the server to derive an authorization identity from the client's authentication credentials. If use of a security layer is negotiated, it is applied to all subsequent data sent over the connection. The security layer takes effect immediately following the last response of the authentication exchange for data sent by the client and the completion indication for data sent by the server. Once the security layer is in effect, the protocol stream is processed by the security layer into buffers of cipher-text. Each buffer is transferred over the connection as a stream of octets prepended with a four octet field in network byte order that represents the length of the following buffer. The length of the cipher-text buffer must be no larger than the maximum size that was defined or negotiated by the other side. 1.4 Requirements ================ The GNU SASL library does not have any required external dependencies, but some optional features are enabled if you have a specific external library. LibNTLM The NTLM mechanism requires the library LibNTLM, `http://josefsson.org/libntlm/'. GSS-API The GSS-API mechanism requires a GSS-API library, such as GNU GSS (`http://josefsson.org/gss/'), MIT Kerberos or Heimdal. LibIDN Processing of non-ASCII username and passwords requires the SASLprep implementation in GNU LibIDN (`http://josefsson.org/libidn/'). This is needed for full conformance with the latest SASL protocol drafts, but is optional in the library for improved portability. Libgcrypt The GNU SASL library ships with its own cryptographic implementation, but it can use the one in libgcrypt (`http://www.gnupg.org/') instead, if it is available. This is typically useful for desktop machines which have libgcrypt installed. The command-line interface to GNU SASL requires a POSIX or Windows platform for network connectivity. The command-line tool can make use of GnuTLS (`http://josefsson.org/gnutls/') to support the STARTTLS modes of IMAP and SMTP, but GnuTLS is not required. Note that the library does not need a POSIX platform or network connectivity. 1.5 Supported Platforms ======================= GNU SASL has at some point in time been tested on the following platforms. 1. Debian GNU/Linux 3.0 (Woody) GCC 2.95.4 and GNU Make. This is the main development platform. `alphaev67-unknown-linux-gnu', `alphaev6-unknown-linux-gnu', `arm-unknown-linux-gnu', `hppa-unknown-linux-gnu', `hppa64-unknown-linux-gnu', `i686-pc-linux-gnu', `ia64-unknown-linux-gnu', `m68k-unknown-linux-gnu', `mips-unknown-linux-gnu', `mipsel-unknown-linux-gnu', `powerpc-unknown-linux-gnu', `s390-ibm-linux-gnu', `sparc-unknown-linux-gnu'. 2. Debian GNU/Linux 2.1 GCC 2.95.1 and GNU Make. `armv4l-unknown-linux-gnu'. 3. Tru64 UNIX Tru64 UNIX C compiler and Tru64 Make. `alphaev67-dec-osf5.1', `alphaev68-dec-osf5.1'. 4. SuSE Linux 7.1 GCC 2.96 and GNU Make. `alphaev6-unknown-linux-gnu', `alphaev67-unknown-linux-gnu'. 5. SuSE Linux 7.2a GCC 3.0 and GNU Make. `ia64-unknown-linux-gnu'. 6. RedHat Linux 7.2 GCC 2.96 and GNU Make. `alphaev6-unknown-linux-gnu', `alphaev67-unknown-linux-gnu', `ia64-unknown-linux-gnu'. 7. RedHat Linux 8.0 GCC 3.2 and GNU Make. `i686-pc-linux-gnu'. 8. RedHat Advanced Server 2.1 GCC 2.96 and GNU Make. `i686-pc-linux-gnu'. 9. Slackware Linux 8.0.01 GCC 2.95.3 and GNU Make. `i686-pc-linux-gnu'. 10. Mandrake Linux 9.0 GCC 3.2 and GNU Make. `i686-pc-linux-gnu'. 11. IRIX 6.5 MIPS C compiler, IRIX Make. `mips-sgi-irix6.5'. 12. AIX 4.3.2 IBM C for AIX compiler, AIX Make. `rs6000-ibm-aix4.3.2.0'. 13. Microsoft Windows 2000 (Cygwin) GCC 3.2, GNU make. `i686-pc-cygwin'. 14. HP-UX 11 HP-UX C compiler and HP Make. `ia64-hp-hpux11.22', `hppa2.0w-hp-hpux11.11'. 15. SUN Solaris 2.8 Sun WorkShop Compiler C 6.0 and SUN Make. `sparc-sun-solaris2.8'. 16. SUN Solaris 2.9 Sun Forte Developer 7 C compiler and GNU Make. `sparc-sun-solaris2.9'. 17. NetBSD 1.6 GCC 2.95.3 and GNU Make. `alpha-unknown-netbsd1.6', `i386-unknown-netbsdelf1.6'. 18. OpenBSD 3.1 and 3.2 GCC 2.95.3 and GNU Make. `alpha-unknown-openbsd3.1', `i386-unknown-openbsd3.1'. 19. FreeBSD 4.7 GCC 2.95.4 and GNU Make. `alpha-unknown-freebsd4.7', `i386-unknown-freebsd4.7'. 20. Cross compiled to uClinux/uClibc on Motorola Coldfire. GCC 3.4 and GNU Make `m68k-uclinux-elf'. If you port GNU SASL to a new platform, please report it to the author so this list can be updated. 1.6 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-gsasl'. 1.7 Commercial Support ====================== Commercial support is available for users of GNU SASL. The kind of support that can be purchased may include: * Implement new features. Such as a new SASL mechanism. * Port GNU SASL to new platforms. This could include porting to an embedded platforms that may need memory or size optimization. * Integrating SASL as a security environment in your existing project. * System design of components related to SASL. If you are interested, please write to: Simon Josefsson Datakonsult Hagagatan 24 113 47 Stockholm Sweden E-mail: simon@josefsson.org If your company provide support related to GNU SASL and would like to be mentioned here, contact the author (*note Bug Reports::). 1.8 Downloading and Installing ============================== The package can be downloaded from several places, including: `http://josefsson.org/gsasl/releases/' The latest version is stored in a file, e.g., `gsasl-0.2.27.tar.gz' where the `0.2.27' value is the highest version number in the directory. 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. Here is an example terminal session that download, configure, build and install the package. You will need a few basic tools, such as `sh', `make' and `cc'. $ wget -q http://josefsson.org/gsasl/releases/gsasl-0.2.27.tar.gz $ tar xfz gsasl-0.2.27.tar.gz $ cd gsasl-0.2.27/ $ ./configure ... $ make ... $ make install ... After that gsasl should be properly installed and ready for use. A few `configure' options may be relevant, summarized in the table. `--disable-client' `--disable-server' If your target system require a minimal implementation, you may wish to disable the client or the server part of the code. This do not remove symbols from the library, so if you attempt to call an application that uses server functions in a library built with `--disable-server', the function will return an error code. `--disable-obsolete' This remove backwards compatibility (*note Old Functions::). Use if you want to limit the size of the library. `--disable-anonymous' `--disable-external' `--disable-plain' `--disable-login' `--disable-securid' `--disable-ntlm' `--disable-cram-md5' `--disable-digest-md5' `--disable-gssapi' `--enable-kerberos_v5' Disable or enable individual mechanisms (*note Mechanisms::). `--without-stringprep' Disable internationalized string processing. Note that this will result in a SASL library that is only compatible with RFC 2222. For the complete list, refer to the output from `configure --help'. 1.8.1 Installing under Windows ------------------------------ There are two ways to build GNU SASL on Windows: via MinGW or via Visual Studio C++. With MinGW, you can build a GNU SASL DLL and use it from other applications. After installing MinGW (`http://mingw.org/') follow the generic installation instructions (*note Downloading and Installing::). The DLL is installed by default. For information on how to use the DLL in other applications, see: `http://www.mingw.org/mingwfaq.shtml#faq-msvcdll'. You can build GNU SASL as a native Visual Studio C++ project. This allows you to build the code for other platforms that VS supports, such as Windows Mobile. You need Visual Studio 2005 or later. First download and unpack the archive as described in the generic installation instructions (*note Downloading and Installing::). Don't run `./configure'. Instead, start Visual Studio and open the project file `lib/win32/libgsasl.sln' inside the GNU SASL directory. You should be able to build the project using VS. Output libraries will be written into the `lib/win32/lib' (or `lib/win32/lib/debug' for Debug versions) folder. Warning! Unless you build GNU SASL linked with libgcrypt, GNU SASL uses the Windows function `CryptGenRandom' for generating cryptographic random data. The function is known to have some security weaknesses. See `http://eprint.iacr.org/2007/419' for more information. 1.9 Bug Reports =============== If you think you have found a bug in GNU SASL, please investigate it and report it. * Please make sure that the bug is really in GNU SASL, 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-gsasl@gnu.org' 1.10 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 (*note GNU Coding Standards: (standards)top.). If you normally code using another coding standard, there is no problem, but you should use `indent' to reformat the code (*note GNU Indent: (indent)top.) 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. 2 Preparation ************* To use GNU SASL, you have to perform some changes to your sources and the build system. The necessary changes are small and explained in the following sections. At the end of this chapter, it is described how the library is initialized, and how the requirements of the library are verified. A faster way to find out how to adapt your application for use with GNU SASL may be to look at the examples at the end of this manual (*note Examples::). 2.1 Header ========== All interfaces (data types and functions) of the library are defined in the header file `gsasl.h'. You must include this in all programs using the library, either directly or through some other header file, like this: #include The name space is `gsasl_*' for function names, `Gsasl*' for data types and `GSASL_*' for other symbols. In addition the same name prefixes with one prepended underscore are reserved for internal use and should never be used by an application. 2.2 Initialization ================== The library must be initialized before it can be used. The library is initialized by calling `gsasl_init' (*note Global Functions::). The resources allocated by the initialization process can be released if the application no longer has a need to call `Libgsasl' functions, this is done by calling `gsasl_done'. For example: int main (int argc, char *argv[]) { Gsasl *ctx = NULL; int rc; ... rc = gsasl_init (&ctx); if (rc != GSASL_OK) { printf ("SASL initialization failure (%d): %s\n", rc, gsasl_strerror (rc)); return 1; } ... In order to make error messages from `gsasl_strerror' be translated (*note Top: (gettext)Top.) the application must set the current locale using `setlocale' before calling `gsasl_init'. For example: int main (int argc, char *argv[]) { Gsasl *ctx = NULL; int rc; ... setlocale (LC_ALL, ""); ... rc = gsasl_init (&ctx); if (rc != GSASL_OK) { printf (gettext ("SASL initialization failure (%d): %s\n"), rc, gsasl_strerror (rc)); return 1; } ... In order to take advantage of the secure memory features in Libgcrypt(1), you need to initialize secure memory in your application, and for some platforms even make your application setuid root. See the Libgcrypt documentation for more information. Example code to initialize secure memory in your code: #include ... int main (int argc, char *argv[]) { Gsasl *ctx = NULL; int rc; ... /* Check version of libgcrypt. */ if (!gcry_check_version (GCRYPT_VERSION)) die ("version mismatch\n"); /* Allocate a pool of 16k secure memory. This also drops priviliges on some systems. */ gcry_control (GCRYCTL_INIT_SECMEM, 16384, 0); /* Tell Libgcrypt that initialization has completed. */ gcry_control (GCRYCTL_INITIALIZATION_FINISHED, 0); ... rc = gsasl_init (&ctx); if (rc != GSASL_OK) { printf ("SASL initialization failure (%d): %s\n", rc, gsasl_strerror (rc)); return 1; } ... If you do not do this, keying material will not be allocated in secure memory (which for most application is not the biggest secure problem anyway). Note that the GNU SASL Library has not been audited to make sure it only ever stores passwords or keys in secure memory. ---------- Footnotes ---------- (1) Note that GNU SASL normally use its own internal implementation of the cryptographic functions. Take care to verify that GNU SASL really use Libgcrypt, if this is what you want. 2.3 Version Check ================= It is often desirable to check that the version of the library 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. gsasl_check_version ------------------- -- Function: const char * gsasl_check_version (const char * REQ_VERSION) REQ_VERSION: version string to compare with, or NULL. Check library version. See `GSASL_VERSION' for a suitable `req_version' string. *Return value:* Check that the 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. The normal way to use the function is to put something similar to the following early in your `main': if (!gsasl_check_version (GSASL_VERSION)) { printf ("gsasl_check_version failed:\n" "Header file incompatible with shared library.\n"); exit(1); } 2.4 Building the source ======================= If you want to compile a source file including the `gsasl.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 libgsasl'. The following example shows how it can be used at the command line: gcc -c foo.c `pkg-config libgsasl --cflags` Adding the output of `pkg-config libgsasl --cflags' to the compilers command line will ensure that the compiler can find the `gsasl.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 libgsasl' can be used. For convenience, this option also outputs all other options that are required to link the program with the `libgsasl' libarary (for instance, the `-lidn' option). The example shows how to link `foo.o' with the `libgsasl' library to a program `foo'. gcc -o foo foo.o `pkg-config libgsasl --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 libgsasl --cflags --libs` 2.5 Autoconf tests ================== If you work on a project that uses Autoconf (*note GNU Autoconf: (autoconf)top.) to help find installed libraries, the suggestions in the previous section are not the entire story. There are a few methods to detect and incorporate the GNU SASL Library into your Autoconf based package. The preferred approach, is to use Libtool in your project, and use the normal Autoconf header file and library tests. 2.5.1 Autoconf test via `pkg-config' ------------------------------------ If your audience is a typical GNU/Linux desktop, you can often assume they have the `pkg-config' tool installed, in which you can use its Autoconf M4 macro to find and set up your package for use with Libgsasl. The following illustrate this scenario. AC_ARG_ENABLE(gsasl, AC_HELP_STRING([--disable-gsasl], [don't use GNU SASL]), gsasl=$enableval) if test "$gsal" != "no" ; then PKG_CHECK_MODULES(GSASL, libgsasl >= 0.2.27, [gsasl=yes], [gsasl=no]) if test "$gsasl" != "yes" ; then sal=no AC_MSG_WARN([Cannot find GNU SASL, disabling]) else gsasl=yes AC_DEFINE(USE_GSASL, 1, [Define to 1 if you want GNU SASL.]) fi fi AC_MSG_CHECKING([if GNU SASL should be used]) AC_MSG_RESULT($gsasl) 2.5.2 Standalone Autoconf test using Libtool -------------------------------------------- If your package uses Libtool(*note GNU Libtool: (libtool)top.), you can use the normal Autoconf tests to find Libgsasl and rely on the Libtool dependency tracking to include the proper dependency libraries (e.g., Libidn). The following illustrate this scenario. AC_CHECK_HEADER(gsasl.h, AC_CHECK_LIB(gsasl, gsasl_check_version, [gsasl=yes AC_SUBST(GSASL_LIBS, -lgsasl)], gsasl=no), gsasl=no) AC_ARG_ENABLE(gsasl, AC_HELP_STRING([--disable-gsasl], [don't use GNU SASL]), gsasl=$enableval) if test "$gsasl" != "no" ; then AC_DEFINE(USE_SASL, 1, [Define to 1 if you want GNU SASL.]) else AC_MSG_WARN([Cannot find GNU SASL, diabling]) fi AC_MSG_CHECKING([if GNU SASL should be used]) AC_MSG_RESULT($gsasl) 3 Using the Library ******************* Your application's use of the library can be roughly modeled into the following steps: initialize the library, optionally specify the callback, perform the authentication, and finally clean up. The following image illustrate this. The third step may look the most complex, but for a simple client it will actually not involve any code. If your application need to handle several concurrent clients, or if it is a server that need to serve many clients simultaneous, things do get a bit more complicated. For illustration, we will write a simple client. Writing a server would be similar, the only difference is that, later on, instead of supplying username or passwords, you need to decide whether someone should be allowed to log in or not. The code for what we have discussed so far make up our `main' function in our client (*note Example 1::): int main (int argc, char *argv[]) { Gsasl *ctx = NULL; int rc; if ((rc = gsasl_init (&ctx)) != GSASL_OK) { printf ("Cannot initialize libgsasl (%d): %s", rc, gsasl_strerror (rc)); return 1; } client (ctx); gsasl_done (ctx); return 0; } Here, the call to the function `client' correspond to the third step in the image above. For a more complicated application, that have several clients running simultaneous, instead of simply calling `client', it may have created new threads for each session, and call `client' within each thread. The library is thread safe. An actual authentication session is more complicated than what we have seen so far. The steps that make up it are: decide which mechanism to use, start the session, optionally specify the callback, optionally set any properties, perform the authentication loop, and clean up. Naturally, your application will start to talk its own protocol (e.g., SMTP or IMAP) after these steps have concluded. The authentication loop is based on sending tokens (typically short messages encoded in base 64) back and forth between the client and server. It continue until authentication succeeds or there is an error. The format of the data to transfer, the number of iterations in the loop, and other details are specified by each mechanism. The goal of the library is to isolate your application from the details of all different mechanisms. Note that the library do not send data to the server itself, but return it in an buffer. You must send it to the server yourself, according to an application protocol profile. For example, the SASL application protocol profile for SMTP is described in RFC 2554. The following image illustrate the steps we have been talking about. We will now show the implementation of the `client' function used before. void client (Gsasl *ctx) { Gsasl_session *session; const char *mech = "PLAIN"; int rc; /* Create new authentication session. */ if ((rc = gsasl_client_start (ctx, mech, &session)) != GSASL_OK) { printf ("Cannot initialize client (%d): %s\n", rc, gsasl_strerror (rc)); return; } /* Set username and password in session handle. This info will be lost when this session is deallocated below. */ gsasl_property_set (session, GSASL_AUTHID, "jas"); gsasl_property_set (session, GSASL_PASSWORD, "secret"); /* Do it. */ client_authenticate (ctx, session); /* Cleanup. */ gsasl_finish (session); } This function is responsible for deciding which mechanism to use. In this case, the `PLAIN' mechanism is hard coded, but you will see later how this can be made more flexible. The function create a new session, store the username and password in the session handle, then call another function `client_authenticate' to handle the authentication loop, and end by cleaning up. Let's continue with the implementation of `client_authenticate'. void client_authenticate (Gsasl * ctx, Gsasl_session * session) { char buf[BUFSIZ] = ""; char *p; int rc; /* This loop mimic a protocol where the server get to send data first. */ do { printf ("Input base64 encoded data from server:\n"); fgets (buf, sizeof (buf) - 1, stdin); if (buf[strlen (buf) - 1] == '\n') buf[strlen (buf) - 1] = '\0'; rc = gsasl_step64 (session, buf, &p); if (rc == GSASL_NEEDS_MORE || rc == GSASL_OK) { printf ("Output:\n%s\n", p); free (p); } } while (rc == GSASL_NEEDS_MORE); printf ("\n"); if (rc != GSASL_OK) { printf ("Authentication error (%d): %s\n", rc, gsasl_strerror (rc)); return; } /* The client is done. Here you would typically check if the server let the client in. If not, you could try again. */ printf ("If server accepted us, we're done.\n"); } This last function need to be discussed in some detail. First, you should be aware that there are two versions of this function, that differ in a subtle way. The version above (*note Example 2::) is used for application profiles where the server send data first. For some mechanisms, this may waste a roundtrip, because the server need input from the client to proceed. Therefor, today the recommended approach is to permit client to send data first (*note Example 1::). Which version you should use depend on which application protocol you are implementing. Further, you should realize that it is bad programming style to use a fixed size buffer. On GNU systems, you may use the `getline' functions instead of `fgets'. However, in practice, there are few mechanisms that use very large tokens. In typical configurations, the mechanism with the largest tokens (GSSAPI) can use at least 500 bytes. A fixed buffer size of 8192 bytes may thus be sufficient for now. But don't say I didn't warn you, when a future mechanism doesn't work in your application, because of a fixed size buffer. The `gsasl_step64' (and of course also `gasl_step') return two non-error return codes. `GSASL_OK' is used for success, indicating that the library consider the authentication finished. That may include a successful server authentication, depending on the mechanism. You must not let the client continue to the application protocol part unless you receive `GSASL_OK' from these functions. In particular, don't be fooled into believing authentication were successful if the server reply "OK" but these function has failed with an error. The server may have been hacked, and could be tricking you into sending confidential data, without having successfully authenticated the server. The non-error return code `GSASL_NEEDS_MORE' is used to signal to your application that you should send the output token to the peer, and wait for a new token, and do another iteration. If the server conclude the authentication process, with no data, you should call `gsasl_step64' (or `gsasl_step') specifying a zero-length token. If the functions (`gsasl_step' and `gsasl_step64') return any non-error code, the content of the output buffer is undefined. Otherwise, it is the callers responsibility to deallocate the buffer, by calling `free'. Note that in some situations, where the buffer is empty, `NULL' is returned as the buffer value. You should treat this as an empty buffer. 3.1 Choosing a mechanism ======================== Our earlier code was hard coded to use a specific mechanism. This is rarely a good idea. Instead, it is recommended to select the best mechanism available from the list of mechanism supported by the server. Note that without TLS or similar, the list may have been maliciously altered, by an attacker. This means that you should abort if you cannot find any mechanism that exceeds your minimum security level. There is a function `gsasl_client_suggest_mechanism' (*note Global Functions::) that will try to pick the "best" available mechanism from a list of mechanisms. Our simple interactive example client (*note Example 3::) include the following function to decide which mechanism to use. Note that the code doesn't blindly use what is returned from `gsasl_client_suggest_mechanism', but rather let some logic (in this case the user, through an interactive query) decide which mechanism is acceptable. const char *client_mechanism (Gsasl *ctx) { static char mech[GSASL_MAX_MECHANISM_SIZE + 1] = ""; char mechlist[BUFSIZ] = ""; const char *suggestion; printf ("Enter list of mechanism that server support, separate by SPC:\n"); fgets (mechlist, sizeof (mechlist) - 1, stdin); suggestion = gsasl_client_suggest_mechanism (ctx, mechlist); if (suggestion) printf ("Library suggest use of `%s'.\n", suggestion); printf ("Enter mechanism to use:\n"); fgets (mech, sizeof (mech) - 1, stdin); mech[strlen (mech) - 1] = '\0'; return mech; } When running this example code, it might look like in the following output. Enter list of mechanism that server support, separate by SPC: CRAM-MD5 DIGEST-MD5 GSSAPI FOO BAR Library suggest use of `GSSAPI'. Enter mechanism to use: CRAM-MD5 Input base64 encoded data from server: Zm5vcmQ= Output: amFzIDkyY2U1NWE5MTM2ZTY4NzEyMTUyZTFjYmFmNjVkZjgx If server accepted us, we're done. 3.2 Using a callback ==================== Our earlier code specified the username and password before the authentication loop, as in: gsasl_property_set (ctx, GSASL_AUTHID, "jas"); gsasl_property_set (ctx, GSASL_PASSWORD, "secret"); This may work for simple mechanisms, that only ever need an username and a password. But some mechanism require more information, such as an authorization identity, a special PIN or passcode, a realm, a hostname, a service name, or an anonymous identifier. Querying the user for all that information, without knowing exactly which of it is really needed will result in a poor user interface. The user should not have to input private information, if it isn't required. The approach is a bad idea for another reason. What if the server abort the authentication process? Then your application have already queried the user for a username and password. It would be better if you only asked the user for this information, annoying to input, when it is known to be needed. A better approach to this problem is to use a callback. Then the mechanism may query your application whenever it need some information, like the username and password. It will only do this at the precise step in the authentication when the information is actually needed. Further, if the user abort, e.g., a password prompt, the mechanism is directly informed of this (because it invoked the callback), and could recover somehow. Our final example (*note Example 4::) specify a callback function, inside `main' as below. /* Set the callback handler for the library. */ gsasl_callback_set (ctx, callback); The function itself is implemented as follows. int callback (Gsasl * ctx, Gsasl_session * sctx, Gsasl_property prop) { char buf[BUFSIZ] = ""; int rc = GSASL_NO_CALLBACK; /* Get user info from user. */ printf ("Callback invoked, for property %d.\n", prop); switch (prop) { case GSASL_PASSCODE: printf ("Enter passcode:\n"); fgets (buf, sizeof (buf) - 1, stdin); buf[strlen (buf) - 1] = '\0'; gsasl_property_set (sctx, GSASL_PASSCODE, buf); rc = GSASL_OK; break; case GSASL_AUTHID: printf ("Enter username:\n"); fgets (buf, sizeof (buf) - 1, stdin); buf[strlen (buf) - 1] = '\0'; gsasl_property_set (sctx, GSASL_AUTHID, buf); rc = GSASL_OK; break; default: printf ("Unknown property! Don't worry.\n"); break; } return rc; } Again, it is bad style to use a fixed size buffer. Mmm'kay. Which properties you should handle is up to you. If you don't know how to respond to a certain property, simply return `GSASL_NO_CALLBACK'. The basic properties to support are authentication identity (`GSASL_AUTHID'), authorization identity (`GSASL_AUTHZID'), and password (`GSASL_PASSWORD'). See *Note Properties::, for the list of all properties, and what your callback should (ideally) do for them, and which properties each mechanism require in order to work. 4 Properties ************ Properties with associated data: * `GSASL_AUTHID' The authentication identity. * `GSASL_AUTHZID' The authorization identity. * `GSASL_PASSWORD' The password of the authentication identity. * `GSASL_ANONYMOUS_TOKEN' The anonymous token. This is typically the email address of the user. * `GSASL_SERVICE' The registered GSSAPI service name of the application service, e.g. "imap". While the names are registered for GSSAPI, other mechanisms such as DIGEST-MD5 may also use this. * `GSASL_HOSTNAME' Should be the local host name of the machine. * `GSASL_GSSAPI_DISPLAY_NAME' Contain the GSSAPI "display name", set by the server GSSAPI mechanism. Typically you retrieve this property in your callback, when invoked for `GSASL_VALIDATE_GSSAPI'. * `GSASL_REALM' The name of the authentication domain. This is used by several mechanisms, including DIGEST-MD5, GSS-API, KERBEROS_V5 and NTLM. * `GSASL_PASSCODE' The SecurID passcode. * `GSASL_PIN' The SecurID personal identification number (PIN). * `GSASL_SUGGESTED_PIN' A SecurID personal identification number (PIN) suggested by the server. Abstract properties, used to trigger the callback, typically used in servers to validate client credentials: * `GSASL_VALIDATE_SIMPLE' You may retrieve GSASL_AUTHID, GSASL_AUTHZID and GSASL_PASSWORD and use them to make an authentication and authorization decision. * `GSASL_VALIDATE_EXTERNAL' Used by EXTERNAL mechanism on the server side to validate the client. The GSASL_AUTHID will contain the authorization identity of the client. * `GSASL_VALIDATE_ANONYMOUS' Used by ANONYMOUS mechanism on the server side to validate the client. The GSASL_ANONYMOUS_TOKEN will contain token that identity the client. * `GSASL_VALIDATE_GSSAPI' Used by the GSSAPI mechanism on the server side, to validate the client. You may retrieve the authorization identity from GSASL_AUTHZID and the GSS-API display name from GSASL_GSSAPI_DISPLAY_NAME. * `GSASL_VALIDATE_SECURID' Used by SECURID mechanism on the server side to validate client. The GSASL_AUTHID, GSASL_AUTHZID, GSASL_PASSCODE, and GSASL_PIN will be set. It can return GSASL_SECURID_SERVER_NEED_ADDITIONAL_PASSCODE to ask the client to supply another passcode, and GSASL_SECURID_SERVER_NEED_NEW_PIN to require the client to supply a new PIN code. 5 Mechanisms ************ Different SASL mechanisms have different requirements on the application using it. To handle these differences the library can use a callback function into your application in several different ways. Some mechanisms, such as `PLAIN', are simple to explain and use. The client callback query the user for a username and password. The server callback hand the username and password into any local policy deciding authentication system (such as `/etc/passwd' via PAM). Mechanism such as `CRAM-MD5' and `DIGEST-MD5' uses hashed passwords. The client callback behaviour is the same as for PLAIN. However, the server do not receive the plain text password over the network but rather a hash of it. Existing policy deciding systems like PAM cannot handle this, so the server callback for these mechanisms are more complicated. Further, mechanisms like GSSAPI (Kerberos 5) assume a specific authentication system. In theory this means that the SASL library would not need to interact with the application, but rather call this specific authentication system directly. However, some callbacks are supported anyway, to modify the behaviour of how the specific authentication system is used (i.e., to handle "super-user" login as some other user). Some mechanisms, like `EXTERNAL' and `ANONYMOUS' are entirely dependent on callbacks. 5.1 The EXTERNAL mechanism ========================== The EXTERNAL mechanism is used to authenticate a user to a server based on out-of-band authentication. EXTERNAL is typically used over TLS authenticated channels. Note that in the server, you need to make sure that TLS actually authenticated the client successfully. It is normally not sufficient that TLS is used, since they also support anonymous modes. In the client, this mechanism is always enabled, and will send the `GSASL_AUTHZID' property as the authorization name to the server, if the property is set. If the property is not set, the empty authorization name is sent. You need not implement a callback. In the server, this mechanism will invoke the `GSASL_VALIDATE_EXTERNAL' callback to decide whether the client is authenticated and authorized to log in. Your callback can retrieve the `GSASL_AUTHZID' property to inspect the requested authorization name from the client. 5.2 The ANONYMOUS mechanism =========================== The ANONYMOUS mechanism is used to "authenticate" clients to anonymous services; or rather, just indicate that the client wishes to use the service anonymously. The client sends a token, usually her email address, which serve the purpose of some trace information suitable for log files. The token is not permitted to be empty. In the client, this mechanism is always enabled, and will send the `GSASL_ANONYMOUS_TOKEN' property as the trace information to the server. In the server, this mechanism will invoke the `GSASL_VALIDATE_ANONYMOUS' callback to decide whether the client should be permitted to log in. Your callback can retrieve the `GSASL_ANONYMOUS_TOKEN' property to, for example, save it in a log file. The token is normally not used to decide whether the client should be permitted to log in or not. 5.3 The PLAIN mechanism ======================= The PLAIN mechanism uses username and password to authenticate users. Two user names are relevant. The first, the authentication identity, indicate the credential holder, i.e., whom the provided password belongs to. The second, the authorization identity, is typically empty, to indicate that the user requests to log on to the server as herself. However, if the authorization identity is not empty, the server should decide whether the authenticated user may log on as the authorization identity. Normally, only "super-user" accounts such as `admin' or similar should be allowed this. In the client, this mechanism is always enabled, and require the `GSASL_AUTHID' and `GSASL_PASSWORD' properties. If set, `GSASL_AUTHZID' will also be used. In the server, the mechanism is always enabled. Two approaches to authenticate and authorize the client is provided. In the first approach, the server side of the mechanism will invoke the `GSASL_VALIDATE_SIMPLE' callback property to decide whether the client should be accepted or not. The callback may inspect the `GSASL_AUTHID', `GSASL_AUTHID', and `GSASL_PASSWORD' properties. These properties values will be normalized. If the first approach fails (because, e.g., your callback return `GSASL_NO_CALLBACK' to signal that it does not implement `GSASL_VALIDATE_SIMPLE') the mechanism will continue to query the application for a password, via the `GSASL_PASSWORD' property. Your callback may use the `GSASL_AUTHID' and `GSASL_AUTHZID' properties to select the proper password. The password is then normalized and compared to the client credential. Which approach to use? If your database store hashed passwords, you have no option, but must use the first approach. If passwords in your user database are stored in prepared (SASLprep) form, the first approach will be faster. If you do not have prepared passwords available, you can use the second approach to make sure the password is prepared properly before comparison. 5.4 The LOGIN mechanism ======================= The LOGIN mechanism is a non-standard mechanism, and is similar to the PLAIN mechanism except that LOGIN lack the support for authorization identities. Always use PLAIN instead of LOGIN in new applications. The callback behaviour is the same as for PLAIN, except that `GSASL_AUTHZID' is not used nor required, and that the server do not normalize the password using SASLprep. *Note Use of SASLprep in LOGIN::, for a proposed clarification of the interpretation of a hypothetical LOGIN specification. 5.5 The CRAM-MD5 mechanism ========================== The CRAM-MD5 is a widely used, but officially deprecated (apparently in favor of DIGEST-MD5), challenge-response mechanism that transfer hashed passwords instead of clear text passwords. For insecure channels (e.g., when TLS is not used), it is safer than PLAIN. The CRAM-MD5 mechanism do not support authorization identities; making the relationship between CRAM-MD5 and DIGEST-MD5 similar to the relationship between LOGIN and PLAIN. The disadvantage with hashed passwords is that the server cannot use normal authentication infrastructures such as PAM, because the server must have access to the correct password in order to validate an authentication attempt. In the client, this mechanism is always enabled, and require the `GSASL_AUTHID' and `GSASL_PASSWORD' properties. In the server, the mechanism will invoke the `GSASL_PASSWORD' callback, which may use the `GSASL_AUTHID' property to determine which users' password should be used. The `GSASL_AUTHID' will be in normalized form. The server will then normalize the returned password, and compare the client response with the computed correct response, and accept the user accordingly. *Note Use of SASLprep in CRAM-MD5::, for a clarification on the interpretation of the CRAM-MD5 specification that this implementation rely on. 5.6 The DIGEST-MD5 mechanism ============================ The DIGEST-MD5 mechanism is based on repeated hashing using MD5, which after the MD5 break may be argued to be weaker than HMAC-MD5, but supports more features. For example, authorization identities and data integrity and privacy protection are supported. Like CRAM-MD5, only a hashed password is transfered. Consequently, DIGEST-MD5 need access to the correct password (although it may be hashed, another improvement compared to CRAM-MD5) to verify the client response. Alas, this make it impossible to use, e.g., PAM on the server side. In the client, this mechanism is always enabled, and require the `GSASL_AUTHID', `GSASL_PASSWORD', `GSASL_SERVICE', and `GSASL_HOSTNAME' properties. If set, `GSASL_AUTHZID' and `GSASL_REALM' will also be used. In the server, the mechanism will invoke the `GSASL_PASSWORD' callback, which may use the `GSASL_AUTHID', `GSASL_AUTHZID' and `GSASL_REALM' properties to determine which users' password should be used. The server will then compare the client response with a computed correct response, and accept the user accordingly. Currently only the authentication quality of service is implemented. In other words, payload integrity or privacy protection are not supported. Consequently, there are no properties for the maximum buffer size, quality of protection, and cipher fields. 5.7 The NTLM mechanism ====================== The NTLM is a non-standard mechanism. Do not use it in new applications, and do not expect it to be secure. Currently only the client side is supported. In the client, this mechanism is always enabled, and require the `GSASL_AUTHID' and `GSASL_PASSWORD' properties. It will set the `domain' field in the NTLM request to the value of `GSASL_REALM'. Some servers reportedly need non-empty but arbitrary values in that field. 5.8 The SECURID mechanism ========================= The SECURID mechanism uses authentication and authorization identity together with a passcode from a hardware token to authenticate users. In the client, this mechanism is always enabled, and require the `GSASL_AUTHID' and `GSASL_PASSCODE' properties. If set, `GSASL_AUTHZID' will also be used. If the server requests it, the `GSASL_PIN' property is also required, and its callback may inspect the `GSASL_SUGGESTED_PIN' property to discover a server-provided PIN to use. In the server, this mechanism will invoke the `GSASL_VALIDATE_SECURID' callback. The callback may inspect the `GSASL_AUTHID', `GSASL_AUTHZID', and `GSASL_PASSCODE' properties. The callback can return `GSASL_SECURID_SERVER_NEED_ADDITIONAL_PASSCODE' to ask for another additional passcode from the client. The callback can return `GSASL_SECURID_SERVER_NEED_NEW_PIN' to ask for a new PIN code from the client, in which case it may also set the `GSASL_SUGGESTED_PIN' property to indicate a recommended new PIN. If the callbacks has invoked again, after having returned `GSASL_SECURID_SERVER_NEED_NEW_PIN', it may also inspect the `GSASL_PIN' property, in addition to the other properties, to find out the client selected PIN code. 5.9 The GSSAPI mechanism ======================== GSS-API is a framework, similar to SASL, for authentication. The GSSAPI mechanism only support the Kerberos 5 GSS-API mechanism, though. (A new SASL mechanism to support non-Kerberos 5 GSS-API mechanisms may be supported in the future.) In the client, the mechanism is enabled only if the user has acquired credentials (i.e., a ticket granting ticket), and require the `GSASL_AUTHID', `GSASL_SERVICE', and `GSASL_HOSTNAME' properties. In the server, the mechanism require the `GSASL_SERVICE', and `GSASL_HOSTNAME' properties, and will invoke the `GSASL_VALIDATE_GSSAPI' callback in order to validate the user. The callback may inspect the `GSASL_AUTHZID' and `GSASL_GSSAPI_DISPLAY_NAME' properties to decide whether to authorize the user. Note that authentication is performed by the GSS-API library. XXX: explain more about quality of service, maximum buffer size, etc. 5.10 The KERBEROS_V5 mechanism ============================== The KERBEROS_V5 is an experimental mechanism, the protocol specification is available on the GNU SASL homepage. It can operate in three modes, non-infrastructure mode, infrastructure mode and proxied infrastructure mode. Currently only non-infrastructure mode is supported. In the non-infrastructure mode, it works as a superset of most features provided by PLAIN, CRAM-MD5, DIGEST-MD5 and GSSAPI while at the same time building on what is believed to be proven technology (the RFC 1510 network security system). In the non-infrastructure mode, the client must specify (via callbacks) the name of the user, and optionally the server name and realm. The server must be able to retrieve passwords given the name of the user. In the infrastructure mode (proxied or otherwise), it allows clients and servers to authenticate via SASL in an RFC 1510 environment, using a trusted third party, a "Key Distribution Central". In the normal mode, clients aquire tickets out of band and then invokes a one roundtrip AP-REQ and AP-REP exchange. In the proxied mode, which can be used by clients without IP addresses or without connectivity to the KDC (e.g., when the KDC is IPv4 and the client is IPV6-only), the client uses the server to proxy ticket requests and finishes with the AP-REQ/AP-REP exchange. In infrastructure mode (proxied or otherwise), the client nor server need to implement any callbacks (this will likely change later, to allow a server to authorize users, similar to the GSSAPI callback). XXX: update when implementation has matured 6 Global Functions ****************** gsasl_init ---------- -- Function: int gsasl_init (Gsasl ** CTX) CTX: pointer to libgsasl handle. This functions initializes libgsasl. The handle pointed to by ctx is valid for use with other libgsasl functions iff this function is successful. It also register all builtin SASL mechanisms, using `gsasl_register()'. *Return value:* GSASL_OK iff successful, otherwise `GSASL_MALLOC_ERROR'. gsasl_done ---------- -- Function: void gsasl_done (Gsasl * CTX) CTX: libgsasl handle. This function destroys a libgsasl handle. The handle must not be used with other libgsasl functions after this call. gsasl_client_mechlist --------------------- -- Function: int gsasl_client_mechlist (Gsasl * CTX, char ** OUT) CTX: libgsasl handle. OUT: newly allocated output character array. Return a newly allocated string containing SASL names, separated by space, of mechanisms supported by the libgsasl client. `out' is allocated by this function, and it is the responsibility of caller to deallocate it. *Return value:* Returns `GSASL_OK' if successful, or error code. gsasl_server_mechlist --------------------- -- Function: int gsasl_server_mechlist (Gsasl * CTX, char ** OUT) CTX: libgsasl handle. OUT: newly allocated output character array. Return a newly allocated string containing SASL names, separated by space, of mechanisms supported by the libgsasl server. `out' is allocated by this function, and it is the responsibility of caller to deallocate it. *Return value:* Returns `GSASL_OK' if successful, or error code. gsasl_client_support_p ---------------------- -- Function: int gsasl_client_support_p (Gsasl * CTX, const char * NAME) CTX: libgsasl handle. NAME: name of SASL mechanism. Decide whether there is client-side support for a specified mechanism. *Return value:* Returns 1 if the libgsasl client supports the named mechanism, otherwise 0. gsasl_server_support_p ---------------------- -- Function: int gsasl_server_support_p (Gsasl * CTX, const char * NAME) CTX: libgsasl handle. NAME: name of SASL mechanism. Decide whether there is server-side support for a specified mechanism. *Return value:* Returns 1 if the libgsasl server supports the named mechanism, otherwise 0. gsasl_client_suggest_mechanism ------------------------------ -- Function: const char * gsasl_client_suggest_mechanism (Gsasl * CTX, const char * MECHLIST) CTX: libgsasl handle. MECHLIST: input character array with SASL mechanism names, separated by invalid characters (e.g. SPC). Given a list of mechanisms, suggest which to use. *Return value:* Returns name of "best" SASL mechanism supported by the libgsasl client which is present in the input string. gsasl_register -------------- -- Function: int gsasl_register (Gsasl * CTX, const Gsasl_mechanism * MECH) CTX: pointer to libgsasl handle. MECH: plugin structure with information about plugin. This function initialize given mechanism, and if successful, add it to the list of plugins that is used by the library. *Return value:* `GSASL_OK' iff successful, otherwise `GSASL_MALLOC_ERROR'. *Since:* 0.2.0 7 Callback Functions ******************** The callback is used by mechanisms to retrieve information, such as username and password, from the application. In a server, the callback is used to decide whether a user is permitted to log in or not. You tell the library of your callback function by calling `gsasl_callback_set'. Since your callback may need to access to data from other parts of your application, there are hooks to store and retrieve application specific pointers. This avoid the use of global variables in your application, which wouldn't be thread safe. You store a pointer to some information (opaque from the point of view of the library) by calling `gsasl_callback_hook_set' and can later retrieve this data in your callback by calling `gsasl_callback_hook_get'. gsasl_callback_set ------------------ -- Function: void gsasl_callback_set (Gsasl * CTX, Gsasl_callback_function CB) CTX: handle received from `gsasl_init()'. CB: pointer to function implemented by application. Store the pointer to the application provided callback in the library handle. The callback will be used, via `gsasl_callback()', by mechanisms to discover various parameters (such as username and passwords). The callback function will be called with a Gsasl_property value indicating the requested behaviour. For example, for `GSASL_ANONYMOUS_TOKEN', the function is expected to invoke gsasl_property_set(`CTX', `GSASL_ANONYMOUS_TOKEN', "token") where "token" is the anonymous token the application wishes the SASL mechanism to use. See the manual for the meaning of all parameters. *Since:* 0.2.0 gsasl_callback -------------- -- Function: int gsasl_callback (Gsasl * CTX, Gsasl_session * SCTX, Gsasl_property PROP) CTX: handle received from `gsasl_init()', may be `NULL' to derive it from `sctx'. SCTX: session handle. PROP: enumerated value of Gsasl_property type. Invoke the application callback. The `prop' value indicate what the callback is expected to do. For example, for `GSASL_ANONYMOUS_TOKEN', the function is expected to invoke gsasl_property_set(`SCTX', `GSASL_ANONYMOUS_TOKEN', "token") where "token" is the anonymous token the application wishes the SASL mechanism to use. See the manual for the meaning of all parameters. Note that if no callback has been set by the application, but the obsolete callback interface has been used, this function will translate the old callback interface into the new. This interface should be sufficient to invoke all callbacks, both new and old. *Return value:* Returns whatever the application callback return, or `GSASL_NO_CALLBACK' if no application was known. *Since:* 0.2.0 gsasl_callback_hook_set ----------------------- -- Function: void gsasl_callback_hook_set (Gsasl * CTX, void * HOOK) CTX: libgsasl handle. HOOK: opaque pointer to application specific data. Store application specific data in the libgsasl handle. The application data can be later (for instance, inside a callback) be retrieved by calling `gsasl_callback_hook_get()'. This is normally used by the application to maintain a global state between the main program and callbacks. *Since:* 0.2.0 gsasl_callback_hook_get ----------------------- -- Function: void * gsasl_callback_hook_get (Gsasl * CTX) CTX: libgsasl handle. Retrieve application specific data from libgsasl handle. The application data is set using `gsasl_callback_hook_set()'. This is normally used by the application to maintain a global state between the main program and callbacks. *Return value:* Returns the application specific data, or `NULL'. *Since:* 0.2.0 gsasl_session_hook_set ---------------------- -- Function: void gsasl_session_hook_set (Gsasl_session * SCTX, void * HOOK) SCTX: libgsasl session handle. HOOK: opaque pointer to application specific data. Store application specific data in the libgsasl session handle. The application data can be later (for instance, inside a callback) be retrieved by calling `gsasl_session_hook_get()'. This is normally used by the application to maintain a per-session state between the main program and callbacks. *Since:* 0.2.14 gsasl_session_hook_get ---------------------- -- Function: void * gsasl_session_hook_get (Gsasl_session * SCTX) SCTX: libgsasl session handle. Retrieve application specific data from libgsasl session handle. The application data is set using `gsasl_callback_hook_set()'. This is normally used by the application to maintain a per-session state between the main program and callbacks. *Return value:* Returns the application specific data, or `NULL'. *Since:* 0.2.14 8 Property Functions ******************** gsasl_property_set ------------------ -- Function: void gsasl_property_set (Gsasl_session * SCTX, Gsasl_property PROP, const char * DATA) SCTX: session handle. PROP: enumerated value of Gsasl_property type, indicating the type of data in `data'. DATA: zero terminated character string to store. Make a copy of `data' and store it in the session handle for the indicated property `prop'. You can immediately deallocate `data' after calling this function, without affecting the data stored in the session handle. *Since:* 0.2.0 gsasl_property_set_raw ---------------------- -- Function: void gsasl_property_set_raw (Gsasl_session * SCTX, Gsasl_property PROP, const char * DATA, size_t LEN) SCTX: session handle. PROP: enumerated value of Gsasl_property type, indicating the type of data in `data'. DATA: character string to store. LEN: length of character string to store. Make a copy of `len' sized `data' and store a zero terminated version of it in the session handle for the indicated property `prop'. You can immediately deallocate `data' after calling this function, without affecting the data stored in the session handle. Except for the length indicator, this function is identical to gsasl_property_set. *Since:* 0.2.0 gsasl_property_fast ------------------- -- Function: const char * gsasl_property_fast (Gsasl_session * SCTX, Gsasl_property PROP) SCTX: session handle. PROP: enumerated value of Gsasl_property type, indicating the type of data in `data'. Retrieve the data stored in the session handle for given property `prop'. The pointer is to live data, and must not be deallocated or modified in any way. This function will not invoke the application callback. *Return value:* Return property value, if known, or `NULL' if no value known. *Since:* 0.2.0 gsasl_property_get ------------------ -- Function: const char * gsasl_property_get (Gsasl_session * SCTX, Gsasl_property PROP) SCTX: session handle. PROP: enumerated value of Gsasl_property type, indicating the type of data in `data'. Retrieve the data stored in the session handle for given property `prop', possibly invoking the application callback to get the value. The pointer is to live data, and must not be deallocated or modified in any way. This function will invoke the application callback, using `gsasl_callback()', when a property value is not known. If no value is known, and no callback is specified or if the callback fail to return data, and if any obsolete callback functions has been set by the application, this function will try to call these obsolete callbacks, and store the returned data as the corresponding property. This behaviour of this function will be removed when the obsolete callback interfaces are removed. *Return value:* Return data for property, or `NULL' if no value known. *Since:* 0.2.0 9 Session Functions ******************* gsasl_client_start ------------------ -- Function: int gsasl_client_start (Gsasl * CTX, const char * MECH, Gsasl_session ** SCTX) CTX: libgsasl handle. MECH: name of SASL mechanism. SCTX: pointer to client handle. This functions initiates a client SASL authentication. This function must be called before any other gsasl_client_*() function is called. *Return value:* Returns `GSASL_OK' if successful, or error code. gsasl_server_start ------------------ -- Function: int gsasl_server_start (Gsasl * CTX, const char * MECH, Gsasl_session ** SCTX) CTX: libgsasl handle. MECH: name of SASL mechanism. SCTX: pointer to server handle. This functions initiates a server SASL authentication. This function must be called before any other gsasl_server_*() function is called. *Return value:* Returns `GSASL_OK' if successful, or error code. gsasl_step ---------- -- Function: int gsasl_step (Gsasl_session * SCTX, const char * INPUT, size_t INPUT_LEN, char ** OUTPUT, size_t * OUTPUT_LEN) SCTX: libgsasl session handle. INPUT: input byte array. INPUT_LEN: size of input byte array. OUTPUT: newly allocated output byte array. OUTPUT_LEN: pointer to output variable with size of output byte array. Perform one step of SASL authentication. This reads data from the other end (from `input' and `input_len'), processes it (potentially invoking callbacks to the application), and writes data to server (into newly allocated variable `output' and `output_len' that indicate the length of `output'). The contents of the `output' buffer is unspecified if this functions returns anything other than `GSASL_OK' or `GSASL_NEEDS_MORE'. If this function return `GSASL_OK' or `GSASL_NEEDS_MORE', however, the `output' buffer is allocated by this function, and it is the responsibility of caller to deallocate it by calling free (`output'). *Return value:* Returns `GSASL_OK' if authenticated terminated successfully, `GSASL_NEEDS_MORE' if more data is needed, or error code. gsasl_step64 ------------ -- Function: int gsasl_step64 (Gsasl_session * SCTX, const char * B64INPUT, char ** B64OUTPUT) SCTX: libgsasl client handle. B64INPUT: input base64 encoded byte array. B64OUTPUT: newly allocated output base64 encoded byte array. This is a simple wrapper around `gsasl_step()' that base64 decodes the input and base64 encodes the output. The contents of the `b64output' buffer is unspecified if this functions returns anything other than `GSASL_OK' or `GSASL_NEEDS_MORE'. If this function return `GSASL_OK' or `GSASL_NEEDS_MORE', however, the `b64output' buffer is allocated by this function, and it is the responsibility of caller to deallocate it by calling free (`b64output'). *Return value:* Returns `GSASL_OK' if authenticated terminated successfully, `GSASL_NEEDS_MORE' if more data is needed, or error code. gsasl_finish ------------ -- Function: void gsasl_finish (Gsasl_session * SCTX) SCTX: libgsasl session handle. Destroy a libgsasl client or server handle. The handle must not be used with other libgsasl functions after this call. gsasl_encode ------------ -- Function: int gsasl_encode (Gsasl_session * SCTX, const char * INPUT, size_t INPUT_LEN, char ** OUTPUT, size_t * OUTPUT_LEN) SCTX: libgsasl session handle. INPUT: input byte array. INPUT_LEN: size of input byte array. OUTPUT: newly allocated output byte array. OUTPUT_LEN: size of output byte array. Encode data according to negotiated SASL mechanism. This might mean that data is integrity or privacy protected. The `output' buffer is allocated by this function, and it is the responsibility of caller to deallocate it by calling free(`output'). *Return value:* Returns `GSASL_OK' if encoding was successful, otherwise an error code. gsasl_decode ------------ -- Function: int gsasl_decode (Gsasl_session * SCTX, const char * INPUT, size_t INPUT_LEN, char ** OUTPUT, size_t * OUTPUT_LEN) SCTX: libgsasl session handle. INPUT: input byte array. INPUT_LEN: size of input byte array. OUTPUT: newly allocated output byte array. OUTPUT_LEN: size of output byte array. Decode data according to negotiated SASL mechanism. This might mean that data is integrity or privacy protected. The `output' buffer is allocated by this function, and it is the responsibility of caller to deallocate it by calling free(`output'). *Return value:* Returns `GSASL_OK' if encoding was successful, otherwise an error code. 10 Utilities ************ gsasl_saslprep -------------- -- Function: int gsasl_saslprep (const char * IN, Gsasl_saslprep_flags FLAGS, char ** OUT, int * STRINGPREPRC) IN: a UTF-8 encoded string. FLAGS: any SASLprep flag, e.g., `GSASL_ALLOW_UNASSIGNED'. OUT: on exit, contains newly allocated output string. STRINGPREPRC: if non-NULL, will hold precise stringprep return code. Prepare string using SASLprep. On success, the `out' variable must be deallocated by the caller. *Return value:* Returns `GSASL_OK' on success, or `GSASL_SASLPREP_ERROR' on error. *Since:* 0.2.3 gsasl_base64_to --------------- -- Function: int gsasl_base64_to (const char * IN, size_t INLEN, char ** OUT, size_t * OUTLEN) IN: input byte array INLEN: size of input byte array OUT: pointer to newly allocated output byte array OUTLEN: pointer to size of newly allocated output byte array Encode data as base64. The string is zero terminated, and `outlen' holds the length excluding the terminating zero. The `out' buffer must be deallocated by the caller. *Return value:* Returns `GSASL_OK' on success, or `GSASL_MALLOC_ERROR' if input was too large or memory allocation fail. *Since:* 0.2.2 gsasl_base64_from ----------------- -- Function: int gsasl_base64_from (const char * IN, size_t INLEN, char ** OUT, size_t * OUTLEN) IN: input byte array INLEN: size of input byte array OUT: pointer to newly allocated output byte array OUTLEN: pointer to size of newly allocated output byte array Decode Base64 data. The `out' buffer must be deallocated by the caller. *Return value:* Returns `GSASL_OK' on success, `GSASL_BASE64_ERROR' if input was invalid, and `GSASL_MALLOC_ERROR' on memory allocation errors. *Since:* 0.2.2 gsasl_simple_getpass -------------------- -- Function: int gsasl_simple_getpass (const char * FILENAME, const char * USERNAME, char ** KEY) FILENAME: filename of file containing passwords. USERNAME: username string. KEY: newly allocated output character array. Retrieve password for user from specified file. The buffer `key' contain the password if this function is successful. The caller is responsible for deallocating it. The file should be on the UoW "MD5 Based Authentication" format, which means it is in text format with comments denoted by # first on the line, with user entries looking as "usernameTABpassword". This function removes CR and LF at the end of lines before processing. TAB, CR, and LF denote ASCII values 9, 13, and 10, respectively. *Return value:* Return `GSASL_OK' if output buffer contains the password, `GSASL_AUTHENTICATION_ERROR' if the user could not be found, or other error code. gsasl_nonce ----------- -- Function: int gsasl_nonce (char * DATA, size_t DATALEN) DATA: output array to be filled with unpredictable random data. DATALEN: size of output array. Store unpredictable data of given size in the provided buffer. *Return value:* Returns `GSASL_OK' iff successful. gsasl_random ------------ -- Function: int gsasl_random (char * DATA, size_t DATALEN) DATA: output array to be filled with strong random data. DATALEN: size of output array. Store cryptographically strong random data of given size in the provided buffer. *Return value:* Returns `GSASL_OK' iff successful. gsasl_md5 --------- -- Function: int gsasl_md5 (const char * IN, size_t INLEN, char * OUT[16]) IN: input character array of data to hash. INLEN: length of input character array of data to hash. Compute hash of data using MD5. The `out' buffer must be deallocated by the caller. *Return value:* Returns `GSASL_OK' iff successful. gsasl_hmac_md5 -------------- -- Function: int gsasl_hmac_md5 (const char * KEY, size_t KEYLEN, const char * IN, size_t INLEN, char * OUTHASH[16]) KEY: input character array with key to use. KEYLEN: length of input character array with key to use. IN: input character array of data to hash. INLEN: length of input character array of data to hash. Compute keyed checksum of data using HMAC-MD5. The `outhash' buffer must be deallocated by the caller. *Return value:* Returns `GSASL_OK' iff successful. 11 Memory Handling ****************** gsasl_free ---------- -- Function: void gsasl_free (void * PTR) PTR: memory pointer Invoke free(`ptr') to de-allocate memory pointer. Typically used on strings allocated by other libgsasl functions. This is useful on Windows where libgsasl is linked to one CRT and the application is linked to another CRT. Then malloc/free will not use the same heap. This happens if you build libgsasl using mingw32 and the application with Visual Studio. *Since:* 0.2.19 12 Error Handling ***************** Most functions in the GNU SASL Library are returning an error if they fail. For this reason, the application should always catch the error condition and take appropriate measures, for example by releasing the resources and passing the error up to the caller, or by displaying a descriptive message to the user and cancelling the operation. Some error values do not indicate a system error or an error in the operation, but the result of an operation that failed properly. 12.1 Error values ================= Errors are returned as an `int'. Except for the OK case an application should always use the constants instead of their numeric value. Applications are encouraged to use the constants even for OK as it improves readability. Possible values are: ``GSASL_OK'' This value indicates success. The value of this error is guaranteed to always be `0' so you may use it in boolean constructs. ``GSASL_NEEDS_MORE'' SASL mechanism needs more data ``GSASL_UNKNOWN_MECHANISM'' Unknown SASL mechanism ``GSASL_MECHANISM_CALLED_TOO_MANY_TIMES'' SASL mechanism called too many times ``GSASL_MALLOC_ERROR'' Memory allocation error in SASL library ``GSASL_BASE64_ERROR'' Base 64 coding error in SASL library ``GSASL_CRYPTO_ERROR'' Low-level crypto error in SASL library ``GSASL_GSSAPI_RELEASE_BUFFER_ERROR'' GSSAPI library could not deallocate memory in gss_release_buffer() in SASL library. This is a serious internal error. ``GSASL_GSSAPI_IMPORT_NAME_ERROR'' GSSAPI library could not understand a peer name in gss_import_name() in SASL library. This is most likely due to incorrect service and/or hostnames. ``GSASL_GSSAPI_INIT_SEC_CONTEXT_ERROR'' GSSAPI error in client while negotiating security context in gss_init_sec_context() in SASL library. This is most likely due insufficient credentials or malicious interactions. ``GSASL_GSSAPI_ACCEPT_SEC_CONTEXT_ERROR'' GSSAPI error in server while negotiating security context in gss_init_sec_context() in SASL library. This is most likely due insufficient credentials or malicious interactions. ``GSASL_GSSAPI_UNWRAP_ERROR'' GSSAPI error while decrypting or decoding data in gss_unwrap() in SASL library. This is most likely due to data corruption. ``GSASL_GSSAPI_WRAP_ERROR'' GSSAPI error while encrypting or encoding data in gss_wrap() in SASL library. ``GSASL_GSSAPI_ACQUIRE_CRED_ERROR'' GSSAPI error acquiring credentials in gss_acquire_cred() in SASL library. This is most likely due to not having the proper Kerberos key available in /etc/krb5.keytab on the server. ``GSASL_GSSAPI_DISPLAY_NAME_ERROR'' GSSAPI error creating a display name denoting the client in gss_display_name() in SASL library. This is probably because the client supplied bad data. ``GSASL_GSSAPI_UNSUPPORTED_PROTECTION_ERROR'' Other entity requested integrity or confidentiality protection in GSSAPI mechanism but this is currently not implemented. ``GSASL_MECHANISM_PARSE_ERROR'' SASL mechanism could not parse input ``GSASL_AUTHENTICATION_ERROR'' Error authenticating user ``GSASL_INTEGRITY_ERROR'' Integrity error in application payload ``GSASL_NO_CLIENT_CODE'' Client-side functionality not available in library (application error) ``GSASL_NO_SERVER_CODE'' Server-side functionality not available in library (application error) ``GSASL_NO_CALLBACK'' No callback specified by caller (application error). ``GSASL_NO_ANONYMOUS_TOKEN'' Authentication failed because the anonymous token was not provided. ``GSASL_NO_AUTHID'' Authentication failed because the authentication identity was not provided. ``GSASL_NO_AUTHZID'' Authentication failed because the authorization identity was not provided. ``GSASL_NO_PASSWORD'' Authentication failed because the password was not provided. ``GSASL_NO_PASSCODE'' Authentication failed because the passcode was not provided. ``GSASL_NO_PIN'' Authentication failed because the pin code was not provided. ``GSASL_NO_SERVICE'' Authentication failed because the service name was not provided. ``GSASL_NO_HOSTNAME'' Authentication failed because the host name was not provided. ``GSASL_SASLPREP_ERROR'' Could not prepare internationalized (non-ASCII) string. ``GSASL_TOO_SMALL_BUFFER'' SASL function needs larger buffer (internal error) ``GSASL_FOPEN_ERROR'' Could not open file in SASL library ``GSASL_FCLOSE_ERROR'' Could not close file in SASL library ``GSASL_CANNOT_GET_CTX'' Cannot get internal library handle (library error) ``GSASL_NEED_CLIENT_ANONYMOUS_CALLBACK'' SASL mechanism needs gsasl_client_callback_anonymous() callback (application error) ``GSASL_NEED_CLIENT_PASSWORD_CALLBACK'' SASL mechanism needs gsasl_client_callback_password() callback (application error) ``GSASL_NEED_CLIENT_PASSCODE_CALLBACK'' SASL mechanism needs gsasl_client_callback_passcode() callback (application error) ``GSASL_NEED_CLIENT_PIN_CALLBACK'' SASL mechanism needs gsasl_client_callback_pin() callback (application error) ``GSASL_NEED_CLIENT_AUTHORIZATION_ID_CALLBACK'' SASL mechanism needs gsasl_client_callback_authorization_id() callback (application error) ``GSASL_NEED_CLIENT_AUTHENTICATION_ID_CALLBACK'' SASL mechanism needs gsasl_client_callback_authentication_id() callback (application error) ``GSASL_NEED_CLIENT_SERVICE_CALLBACK'' SASL mechanism needs gsasl_client_callback_service() callback (application error) ``GSASL_NEED_SERVER_VALIDATE_CALLBACK'' SASL mechanism needs gsasl_server_callback_validate() callback (application error) ``GSASL_NEED_SERVER_CRAM_MD5_CALLBACK'' SASL mechanism needs gsasl_server_callback_cram_md5() callback (application error) ``GSASL_NEED_SERVER_DIGEST_MD5_CALLBACK'' SASL mechanism needs gsasl_server_callback_digest_md5() callback (application error) ``GSASL_NEED_SERVER_ANONYMOUS_CALLBACK'' SASL mechanism needs gsasl_server_callback_anonymous() callback (application error) ``GSASL_NEED_SERVER_EXTERNAL_CALLBACK'' SASL mechanism needs gsasl_server_callback_external() callback (application error) ``GSASL_NEED_SERVER_REALM_CALLBACK'' SASL mechanism needs gsasl_server_callback_realm() callback (application error) ``GSASL_NEED_SERVER_SECURID_CALLBACK'' SASL mechanism needs gsasl_server_callback_securid() callback (application error) ``GSASL_NEED_SERVER_SERVICE_CALLBACK'' SASL mechanism needs gsasl_server_callback_service() callback (application error) ``GSASL_NEED_SERVER_GSSAPI_CALLBACK'' SASL mechanism needs gsasl_server_callback_gssapi() callback (application error) ``GSASL_NEED_SERVER_RETRIEVE_CALLBACK'' SASL mechanism needs gsasl_server_callback_retrieve() callback (application error) ``GSASL_UNICODE_NORMALIZATION_ERROR'' Failed to perform Unicode Normalization on string. ``GSASL_NO_MORE_REALMS'' No more realms available (non-fatal) ``GSASL_INVALID_HANDLE'' The provided library handle was invalid (application error) 12.2 Error strings ================== gsasl_strerror -------------- -- Function: const char * gsasl_strerror (int ERR) ERR: libgsasl error code Convert return code to human readable string. *Return value:* Returns a pointer to a statically allocated string containing a description of the error with the error value `err'. This string can be used to output a diagnostic message to the user. 13 Examples *********** This chapter contains example code which illustrate how the GNU SASL Library can be used when writing your own application. 13.1 Example 1 ============== /* client.c --- Example SASL client. * Copyright (C) 2004, 2005, 2007 Simon Josefsson * * This file is part of GNU SASL. * * This program is free software: you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation, either version 3 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program. If not, see . * */ #include #include #include #include #include static void client_authenticate (Gsasl * ctx, Gsasl_session * session) { char buf[BUFSIZ] = ""; char *p; int rc; /* This loop mimic a protocol where the client send data first. */ do { /* Generate client output. */ rc = gsasl_step64 (session, buf, &p); if (rc == GSASL_NEEDS_MORE || rc == GSASL_OK) { /* If sucessful, print it. */ printf ("Output:\n%s\n", p); free (p); } if (rc == GSASL_NEEDS_MORE) { /* If the client need more data from server, get it here. */ printf ("Input base64 encoded data from server:\n"); fgets (buf, sizeof (buf) - 1, stdin); if (buf[strlen (buf) - 1] == '\n') buf[strlen (buf) - 1] = '\0'; } } while (rc == GSASL_NEEDS_MORE); printf ("\n"); if (rc != GSASL_OK) { printf ("Authentication error (%d): %s\n", rc, gsasl_strerror (rc)); return; } /* The client is done. Here you would typically check if the server let the client in. If not, you could try again. */ printf ("If server accepted us, we're done.\n"); } static void client (Gsasl * ctx) { Gsasl_session *session; const char *mech = "PLAIN"; int rc; /* Create new authentication session. */ if ((rc = gsasl_client_start (ctx, mech, &session)) != GSASL_OK) { printf ("Cannot initialize client (%d): %s\n", rc, gsasl_strerror (rc)); return; } /* Set username and password in session handle. This info will be lost when this session is deallocated below. */ gsasl_property_set (session, GSASL_AUTHID, "jas"); gsasl_property_set (session, GSASL_PASSWORD, "secret"); /* Do it. */ client_authenticate (ctx, session); /* Cleanup. */ gsasl_finish (session); } int main (int argc, char *argv[]) { Gsasl *ctx = NULL; int rc; /* Initialize library. */ if ((rc = gsasl_init (&ctx)) != GSASL_OK) { printf ("Cannot initialize libgsasl (%d): %s", rc, gsasl_strerror (rc)); return 1; } /* Do it. */ client (ctx); /* Cleanup. */ gsasl_done (ctx); return 0; } 13.2 Example 2 ============== /* client-serverfirst.c --- Example SASL client, where server send data first. * Copyright (C) 2004, 2005, 2007 Simon Josefsson * * This file is part of GNU SASL. * * This program is free software: you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation, either version 3 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program. If not, see . * */ #include #include #include #include #include static void client_authenticate (Gsasl * ctx, Gsasl_session * session) { char buf[BUFSIZ] = ""; char *p; int rc; /* This loop mimic a protocol where the server get to send data first. */ do { printf ("Input base64 encoded data from server:\n"); fgets (buf, sizeof (buf) - 1, stdin); if (buf[strlen (buf) - 1] == '\n') buf[strlen (buf) - 1] = '\0'; rc = gsasl_step64 (session, buf, &p); if (rc == GSASL_NEEDS_MORE || rc == GSASL_OK) { printf ("Output:\n%s\n", p); free (p); } } while (rc == GSASL_NEEDS_MORE); printf ("\n"); if (rc != GSASL_OK) { printf ("Authentication error (%d): %s\n", rc, gsasl_strerror (rc)); return; } /* The client is done. Here you would typically check if the server let the client in. If not, you could try again. */ printf ("If server accepted us, we're done.\n"); } static void client (Gsasl * ctx) { Gsasl_session *session; const char *mech = "CRAM-MD5"; int rc; /* Create new authentication session. */ if ((rc = gsasl_client_start (ctx, mech, &session)) != GSASL_OK) { printf ("Cannot initialize client (%d): %s\n", rc, gsasl_strerror (rc)); return; } /* Set username and password in session handle. This info will be lost when this session is deallocated below. */ gsasl_property_set (session, GSASL_AUTHID, "jas"); gsasl_property_set (session, GSASL_PASSWORD, "secret"); /* Do it. */ client_authenticate (ctx, session); /* Cleanup. */ gsasl_finish (session); } int main (int argc, char *argv[]) { Gsasl *ctx = NULL; int rc; /* Initialize library. */ if ((rc = gsasl_init (&ctx)) != GSASL_OK) { printf ("Cannot initialize libgsasl (%d): %s", rc, gsasl_strerror (rc)); return 1; } /* Do it. */ client (ctx); /* Cleanup. */ gsasl_done (ctx); return 0; } 13.3 Example 3 ============== /* client-mech.c --- Example SASL client, with a choice of mechanism to use. * Copyright (C) 2004, 2005, 2007 Simon Josefsson * * This file is part of GNU SASL. * * This program is free software: you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation, either version 3 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program. If not, see . * */ #include #include #include #include #include static void client_authenticate (Gsasl * ctx, Gsasl_session * session) { char buf[BUFSIZ] = ""; char *p; int rc; /* This loop mimic a protocol where the server get to send data first. */ do { printf ("Input base64 encoded data from server:\n"); fgets (buf, sizeof (buf) - 1, stdin); if (buf[strlen (buf) - 1] == '\n') buf[strlen (buf) - 1] = '\0'; rc = gsasl_step64 (session, buf, &p); if (rc == GSASL_NEEDS_MORE || rc == GSASL_OK) { printf ("Output:\n%s\n", p); free (p); } } while (rc == GSASL_NEEDS_MORE); printf ("\n"); if (rc != GSASL_OK) { printf ("Authentication error (%d): %s\n", rc, gsasl_strerror (rc)); return; } /* The client is done. Here you would typically check if the server let the client in. If not, you could try again. */ printf ("If server accepted us, we're done.\n"); } static const char * client_mechanism (Gsasl * ctx) { static char mech[GSASL_MAX_MECHANISM_SIZE + 1] = ""; char mechlist[BUFSIZ] = ""; const char *suggestion; printf ("Enter list of mechanism that server support, separate by SPC:\n"); fgets (mechlist, sizeof (mechlist) - 1, stdin); suggestion = gsasl_client_suggest_mechanism (ctx, mechlist); if (suggestion) printf ("Library suggest use of `%s'.\n", suggestion); printf ("Enter mechanism to use:\n"); fgets (mech, sizeof (mech) - 1, stdin); mech[strlen (mech) - 1] = '\0'; return mech; } static void client (Gsasl * ctx) { Gsasl_session *session; const char *mech; int rc; /* Find out which mechanism to use. */ mech = client_mechanism (ctx); /* Create new authentication session. */ if ((rc = gsasl_client_start (ctx, mech, &session)) != GSASL_OK) { printf ("Cannot initialize client (%d): %s\n", rc, gsasl_strerror (rc)); return; } /* Set username and password in session handle. This info will be lost when this session is deallocated below. */ gsasl_property_set (session, GSASL_AUTHID, "jas"); gsasl_property_set (session, GSASL_PASSWORD, "secret"); /* Do it. */ client_authenticate (ctx, session); /* Cleanup. */ gsasl_finish (session); } int main (int argc, char *argv[]) { Gsasl *ctx = NULL; int rc; /* Initialize library. */ if ((rc = gsasl_init (&ctx)) != GSASL_OK) { printf ("Cannot initialize libgsasl (%d): %s", rc, gsasl_strerror (rc)); return 1; } /* Do it. */ client (ctx); /* Cleanup. */ gsasl_done (ctx); return 0; } 13.4 Example 4 ============== /* client-callback.c --- Example SASL client, with callback for user info. * Copyright (C) 2004, 2005, 2007 Simon Josefsson * * This file is part of GNU SASL. * * This program is free software: you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation, either version 3 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program. If not, see . * */ #include #include #include #include #include static void client_authenticate (Gsasl * ctx, Gsasl_session * session) { char buf[BUFSIZ] = ""; char *p; int rc; /* This loop mimic a protocol where the server get to send data first. */ do { printf ("Input base64 encoded data from server:\n"); fgets (buf, sizeof (buf) - 1, stdin); if (buf[strlen (buf) - 1] == '\n') buf[strlen (buf) - 1] = '\0'; rc = gsasl_step64 (session, buf, &p); if (rc == GSASL_NEEDS_MORE || rc == GSASL_OK) { printf ("Output:\n%s\n", p); free (p); } } while (rc == GSASL_NEEDS_MORE); printf ("\n"); if (rc != GSASL_OK) { printf ("Authentication error (%d): %s\n", rc, gsasl_strerror (rc)); return; } /* The client is done. Here you would typically check if the server let the client in. If not, you could try again. */ printf ("If server accepted us, we're done.\n"); } static void client (Gsasl * ctx) { Gsasl_session *session; const char *mech = "SECURID"; int rc; /* Create new authentication session. */ if ((rc = gsasl_client_start (ctx, mech, &session)) != GSASL_OK) { printf ("Cannot initialize client (%d): %s\n", rc, gsasl_strerror (rc)); return; } /* Do it. */ client_authenticate (ctx, session); /* Cleanup. */ gsasl_finish (session); } static int callback (Gsasl * ctx, Gsasl_session * sctx, Gsasl_property prop) { char buf[BUFSIZ] = ""; int rc = GSASL_NO_CALLBACK; /* Get user info from user. */ printf ("Callback invoked, for property %d.\n", prop); switch (prop) { case GSASL_PASSCODE: printf ("Enter passcode:\n"); fgets (buf, sizeof (buf) - 1, stdin); buf[strlen (buf) - 1] = '\0'; gsasl_property_set (sctx, GSASL_PASSCODE, buf); rc = GSASL_OK; break; case GSASL_AUTHID: printf ("Enter username:\n"); fgets (buf, sizeof (buf) - 1, stdin); buf[strlen (buf) - 1] = '\0'; gsasl_property_set (sctx, GSASL_AUTHID, buf); rc = GSASL_OK; break; default: printf ("Unknown property! Don't worry.\n"); break; } return rc; } int main (int argc, char *argv[]) { Gsasl *ctx = NULL; int rc; /* Initialize library. */ if ((rc = gsasl_init (&ctx)) != GSASL_OK) { printf ("Cannot initialize libgsasl (%d): %s", rc, gsasl_strerror (rc)); return 1; } /* Set the callback handler for the library. */ gsasl_callback_set (ctx, callback); /* Do it. */ client (ctx); /* Cleanup. */ gsasl_done (ctx); return 0; } 14 Acknowledgements ******************* The makefiles, manuals, etc borrowed much from Libgcrypt written by Werner Koch. Cryptographic functions for some SASL mechanisms uses Libgcrypt by Werner Koch et al. The NTLM mechanism uses Libntlm by Grant Edwards et al, using code from Samba written by Andrew Tridgell, and now maintained by Simon Josefsson. The KERBEROS_V5 mechanism uses Shishi by Simon Josefsson. The GSSAPI mechanism uses a GSS-API implementation, such as GSSLib by Simon Josefsson. Gnulib is used to simplify portability. This manual borrows text from the SASL specification. 15 Invoking gsasl ***************** Name **** GNU SASL (gsasl) - Command line interface to libgsasl. Description *********** `gsasl' is the main program of GNU SASL. This section only lists the commands and options available. Mandatory or optional arguments to long options are also mandatory or optional for any corresponding short options. Commands ******** `gsasl' recognizes these commands: -c, --client Act as client (the default). --client-mechanisms Write name of supported client mechanisms separated by space to stdout. -s, --server Act as server. --server-mechanisms Write name of supported server mechanisms separated by space to stdout. Network Options *************** Normally the SASL negotiation is performed on the terminal, with reading from stdin and writing to stdout. It is also possible to perform the negotiation with a server over a TCP network connection. --connect=HOSTNAME[:SERVICE] Connect to TCP server and negotiate on stream instead of stdin/stdout. SERVICE is the protocol service, or an integer denoting the port, and defaults to 143 (imap) if not specified. Also sets the --hostname default. Miscellaneous Options: ********************** These parameters affect overall behaviour. -d, --application-data After authentication, read data from stdin and run it through the mechanism's security layer and print it base64 encoded to stdout. The default is to terminate after authentication. --imap Use a IMAP-like logon procedure (client only). Also sets the --service default to "imap". -m, --mechanism=STRING Mechanism to use. --no-client-first Disallow client to send data first (client only). SASL Mechanism Options ********************** These options modify the behaviour of the callbacks (*note Callback Functions::) in the library. The default is the query the user on the terminal. -n, --anonymous-token=STRING Token for anonymous authentication, usually mail address (ANONYMOUS only). -a, --authentication-id=STRING Identity of credential owner. -z, --authorization-id=STRING Identity to request service for. --disable-cleartext-validate Disable cleartext validate hook, forcing server to prompt for password. --enable-cram-md5-validate Validate CRAM-MD5 challenge and response interactively. --hostname=STRING Set the name of the server with the requested service. -p, --password=STRING Password for authentication (insecure for non-testing purposes). --passcode=NUMBER Passcode for authentication (SECURID only). --quality-of-protection= How application payload will be protected. "auth" means no protection, "auth-int" means integrity protection, "auth-conf" means integrity and confidentialiy protection. Currently only used by DIGEST-MD5, where the default is "auth-conf". -r, --realm=STRING Realm. Defaults to hostname. --service=STRING Set the requested service name (should be a registered GSSAPI host based service name). --service-name=STRING Set the generic server name in case of a replicated server (DIGEST-MD5 only). -x, --maxbuf=NUMBER Indicate maximum buffer size (DIGEST-MD5 only). STARTTLS options **************** --starttls Force use of STARTTLS. The default is to use STARTTLS when available. (default=off) --no-starttls Unconditionally disable STARTTLS. (default=off) --x509-ca-file=FILE File containing one or more X.509 Certificate Authorities certificates in PEM format, used to verify the certificate received from the server. If not specified, no verification of the remote server certificate will be done. --x509-cert-file=FILE File containing client X.509 certificate in PEM format. Used together with --x509-key-file to specify the certificate/key pair. --x509-key-file=FILE Private key for the client X.509 certificate in PEM format. Used together with --x509-key-file to specify the certificate/key pair. Other Options ************* These are some standard parameters. -q, --quiet, --silent Don't produce any diagnostic output. -v, --verbose Produce verbose output. -?, --help Give this help list --usage Give a short usage message -V, --version Print program version Appendix A Protocol Clarifications ********************************** This appendix contain clarification to various SASL specification that we felt were necessary to include, if for nothing else it may serve as a guide for other implementors that worry about the same issues. A.1 Use of SASLprep in CRAM-MD5 =============================== The specification, as of `draft-ietf-sasl-crammd5-04.txt', is silent on whether a SASL server implementation applying SASLprep on a password received from an external, non-SASL specific database (i.e., the passwords are not stored in SASLprep form in the database), should set or clear the AllowUnassigned bit. The motivation for the AU-bit in StringPrep/SASLprep is for stored vs query strings. It could be argued that in this situation the server can treat the external password either as a stored string (from a database) or as a query (the server uses the string as a query into the fixed HMAC-MD5 hash). The specification is also unclear on whether clients should set or clear the AllowUnassigned flag. In the server, GNU SASL apply SASLprep to the password with the AllowUnassigned bit cleared. A.2 Use of SASLprep in LOGIN ============================ The non-standard mechanism LOGIN presumably does not support non-ASCII. We suggest that the client should send unprepared UTF-8 and that the server apply SASLprep with the AllowUnassigned bit cleared on the received username and password. Appendix B Old Functions ************************ As GNU SASL is still under heavy development, some API functions have been found to be less useful. Those old API functions will be supported during a transition period. Refer to the NEWS file to find out since when a function has been deprecated. gsasl_client_listmech --------------------- -- Function: int gsasl_client_listmech (Gsasl * CTX, char * OUT, size_t * OUTLEN) CTX: libgsasl handle. OUT: output character array. OUTLEN: input maximum size of output character array, on output contains actual length of output array. Write SASL names, separated by space, of mechanisms supported by the libgsasl client to the output array. To find out how large the output array must be, call this function with a `NULL' `out' parameter. *Return value:* Returns `GSASL_OK' if successful, or error code. *Deprecated:* Use `gsasl_client_mechlist()' instead. gsasl_server_listmech --------------------- -- Function: int gsasl_server_listmech (Gsasl * CTX, char * OUT, size_t * OUTLEN) CTX: libgsasl handle. OUT: output character array. OUTLEN: input maximum size of output character array, on output contains actual length of output array. Write SASL names, separated by space, of mechanisms supported by the libgsasl server to the output array. To find out how large the output array must be, call this function with a `NULL' `out' parameter. *Return value:* Returns `GSASL_OK' if successful, or error code. *Deprecated:* Use `gsasl_server_mechlist()' instead. gsasl_client_step ----------------- -- Function: int gsasl_client_step (Gsasl_session * SCTX, const char * INPUT, size_t INPUT_LEN, char * OUTPUT, size_t * OUTPUT_LEN) SCTX: libgsasl client handle. INPUT: input byte array. INPUT_LEN: size of input byte array. OUTPUT: output byte array. OUTPUT_LEN: size of output byte array. Perform one step of SASL authentication in client. This reads data from server (specified with input and input_len), processes it (potentially invoking callbacks to the application), and writes data to server (into variables output and output_len). The contents of the output buffer is unspecified if this functions returns anything other than `GSASL_NEEDS_MORE'. *Return value:* Returns `GSASL_OK' if authenticated terminated successfully, `GSASL_NEEDS_MORE' if more data is needed, or error code. *Deprecated:* Use `gsasl_step()' instead. gsasl_server_step ----------------- -- Function: int gsasl_server_step (Gsasl_session * SCTX, const char * INPUT, size_t INPUT_LEN, char * OUTPUT, size_t * OUTPUT_LEN) SCTX: libgsasl server handle. INPUT: input byte array. INPUT_LEN: size of input byte array. OUTPUT: output byte array. OUTPUT_LEN: size of output byte array. Perform one step of SASL authentication in server. This reads data from client (specified with input and input_len), processes it (potentially invoking callbacks to the application), and writes data to client (into variables output and output_len). The contents of the output buffer is unspecified if this functions returns anything other than `GSASL_NEEDS_MORE'. *Return value:* Returns `GSASL_OK' if authenticated terminated successfully, `GSASL_NEEDS_MORE' if more data is needed, or error code. *Deprecated:* Use `gsasl_step()' instead. gsasl_client_step_base64 ------------------------ -- Function: int gsasl_client_step_base64 (Gsasl_session * SCTX, const char * B64INPUT, char * B64OUTPUT, size_t B64OUTPUT_LEN) SCTX: libgsasl client handle. B64INPUT: input base64 encoded byte array. B64OUTPUT: output base64 encoded byte array. B64OUTPUT_LEN: size of output base64 encoded byte array. This is a simple wrapper around `gsasl_client_step()' that base64 decodes the input and base64 encodes the output. *Return value:* See `gsasl_client_step()'. *Deprecated:* Use `gsasl_step64()' instead. gsasl_server_step_base64 ------------------------ -- Function: int gsasl_server_step_base64 (Gsasl_session * SCTX, const char * B64INPUT, char * B64OUTPUT, size_t B64OUTPUT_LEN) SCTX: libgsasl server handle. B64INPUT: input base64 encoded byte array. B64OUTPUT: output base64 encoded byte array. B64OUTPUT_LEN: size of output base64 encoded byte array. This is a simple wrapper around `gsasl_server_step()' that base64 decodes the input and base64 encodes the output. *Return value:* See `gsasl_server_step()'. *Deprecated:* Use `gsasl_step64()' instead. gsasl_client_finish ------------------- -- Function: void gsasl_client_finish (Gsasl_session * SCTX) SCTX: libgsasl client handle. Destroy a libgsasl client handle. The handle must not be used with other libgsasl functions after this call. *Deprecated:* Use `gsasl_finish()' instead. gsasl_server_finish ------------------- -- Function: void gsasl_server_finish (Gsasl_session * SCTX) SCTX: libgsasl server handle. Destroy a libgsasl server handle. The handle must not be used with other libgsasl functions after this call. *Deprecated:* Use `gsasl_finish()' instead. gsasl_client_ctx_get -------------------- -- Function: Gsasl * gsasl_client_ctx_get (Gsasl_session * SCTX) SCTX: libgsasl client handle *Return value:* Returns the libgsasl handle given a libgsasl client handle. *Deprecated:* This function is not useful with the new 0.2.0 API. gsasl_client_application_data_set --------------------------------- -- Function: void gsasl_client_application_data_set (Gsasl_session * SCTX, void * APPLICATION_DATA) SCTX: libgsasl client handle. APPLICATION_DATA: opaque pointer to application specific data. Store application specific data in the libgsasl client handle. The application data can be later (for instance, inside a callback) be retrieved by calling `gsasl_client_application_data_get()'. It is normally used by the application to maintain state between the main program and the callback. *Deprecated:* Use `gsasl_callback_hook_set()' or `gsasl_session_hook_set()' instead. gsasl_client_application_data_get --------------------------------- -- Function: void * gsasl_client_application_data_get (Gsasl_session * SCTX) SCTX: libgsasl client handle. Retrieve application specific data from libgsasl client handle. The application data is set using `gsasl_client_application_data_set()'. It is normally used by the application to maintain state between the main program and the callback. *Return value:* Returns the application specific data, or `NULL'. *Deprecated:* Use `gsasl_callback_hook_get()' or `gsasl_session_hook_get()' instead. gsasl_server_ctx_get -------------------- -- Function: Gsasl * gsasl_server_ctx_get (Gsasl_session * SCTX) SCTX: libgsasl server handle *Return value:* Returns the libgsasl handle given a libgsasl server handle. *Deprecated:* This function is not useful with the new 0.2.0 API. gsasl_server_application_data_set --------------------------------- -- Function: void gsasl_server_application_data_set (Gsasl_session * SCTX, void * APPLICATION_DATA) SCTX: libgsasl server handle. APPLICATION_DATA: opaque pointer to application specific data. Store application specific data in the libgsasl server handle. The application data can be later (for instance, inside a callback) be retrieved by calling `gsasl_server_application_data_get()'. It is normally used by the application to maintain state between the main program and the callback. *Deprecated:* Use `gsasl_callback_hook_set()' or `gsasl_session_hook_set()' instead. gsasl_server_application_data_get --------------------------------- -- Function: void * gsasl_server_application_data_get (Gsasl_session * SCTX) SCTX: libgsasl server handle. Retrieve application specific data from libgsasl server handle. The application data is set using `gsasl_server_application_data_set()'. It is normally used by the application to maintain state between the main program and the callback. *Return value:* Returns the application specific data, or `NULL'. *Deprecated:* Use `gsasl_callback_hook_get()' or `gsasl_session_hook_get()' instead. gsasl_randomize --------------- -- Function: int gsasl_randomize (int STRONG, char * DATA, size_t DATALEN) STRONG: 0 iff operation should not block, non-0 for very strong randomness. DATA: output array to be filled with random data. DATALEN: size of output array. Store cryptographically random data of given size in the provided buffer. *Return value:* Returns `GSASL_OK' iff successful. *Deprecated:* Use `gsasl_random()' or `gsasl_nonce()' instead. gsasl_ctx_get ------------- -- Function: Gsasl * gsasl_ctx_get (Gsasl_session * SCTX) SCTX: libgsasl session handle *Return value:* Returns the libgsasl handle given a libgsasl session handle. *Deprecated:* This function is not useful with the new 0.2.0 API. gsasl_encode_inline ------------------- -- Function: int gsasl_encode_inline (Gsasl_session * SCTX, const char * INPUT, size_t INPUT_LEN, char * OUTPUT, size_t * OUTPUT_LEN) SCTX: libgsasl session handle. INPUT: input byte array. INPUT_LEN: size of input byte array. OUTPUT: output byte array. OUTPUT_LEN: size of output byte array. Encode data according to negotiated SASL mechanism. This might mean that data is integrity or privacy protected. *Return value:* Returns `GSASL_OK' if encoding was successful, otherwise an error code. *Deprecated:* Use `gsasl_encode()' instead. *Since:* 0.2.0 gsasl_decode_inline ------------------- -- Function: int gsasl_decode_inline (Gsasl_session * SCTX, const char * INPUT, size_t INPUT_LEN, char * OUTPUT, size_t * OUTPUT_LEN) SCTX: libgsasl session handle. INPUT: input byte array. INPUT_LEN: size of input byte array. OUTPUT: output byte array. OUTPUT_LEN: size of output byte array. Decode data according to negotiated SASL mechanism. This might mean that data is integrity or privacy protected. *Return value:* Returns `GSASL_OK' if encoding was successful, otherwise an error code. *Deprecated:* Use `gsasl_decode()' instead. *Since:* 0.2.0 gsasl_application_data_set -------------------------- -- Function: void gsasl_application_data_set (Gsasl * CTX, void * APPDATA) CTX: libgsasl handle. APPDATA: opaque pointer to application specific data. Store application specific data in the libgsasl handle. The application data can be later (for instance, inside a callback) be retrieved by calling `gsasl_application_data_get()'. It is normally used by the application to maintain state between the main program and the callback. *Deprecated:* Use `gsasl_callback_hook_set()' instead. gsasl_application_data_get -------------------------- -- Function: void * gsasl_application_data_get (Gsasl * CTX) CTX: libgsasl handle. Retrieve application specific data from libgsasl handle. The application data is set using `gsasl_application_data_set()'. It is normally used by the application to maintain state between the main program and the callback. *Return value:* Returns the application specific data, or `NULL'. *Deprecated:* Use `gsasl_callback_hook_get()' instead. gsasl_appinfo_set ----------------- -- Function: void gsasl_appinfo_set (Gsasl_session * SCTX, void * APPDATA) SCTX: libgsasl session handle. APPDATA: opaque pointer to application specific data. Store application specific data in the libgsasl session handle. The application data can be later (for instance, inside a callback) be retrieved by calling `gsasl_appinfo_get()'. It is normally used by the application to maintain state between the main program and the callback. *Deprecated:* Use `gsasl_callback_hook_set()' instead. gsasl_appinfo_get ----------------- -- Function: void * gsasl_appinfo_get (Gsasl_session * SCTX) SCTX: libgsasl session handle. Retrieve application specific data from libgsasl session handle. The application data is set using `gsasl_appinfo_set()'. It is normally used by the application to maintain state between the main program and the callback. *Return value:* Returns the application specific data, or `NULL'. *Deprecated:* Use `gsasl_callback_hook_get()' instead. gsasl_server_suggest_mechanism ------------------------------ -- Function: const char * gsasl_server_suggest_mechanism (Gsasl * CTX, const char * MECHLIST) CTX: libgsasl handle. MECHLIST: input character array with SASL mechanism names, separated by invalid characters (e.g. SPC). *Return value:* Returns name of "best" SASL mechanism supported by the libgsasl server which is present in the input string. *Deprecated:* This function was never useful, since it is the client that chose which mechanism to use. gsasl_client_callback_authentication_id_set ------------------------------------------- -- Function: void gsasl_client_callback_authentication_id_set (Gsasl * CTX, Gsasl_client_callback_authentication_id CB) CTX: libgsasl handle. CB: callback function Specify the callback function to use in the client to set the authentication identity. The function can be later retrieved using `gsasl_client_callback_authentication_id_get()'. *Deprecated:* This function is part of the old callback interface. The new interface uses `gsasl_callback_set()' to set the application callback, and uses `gsasl_callback()' or `gsasl_property_get()' to invoke the callback for certain properties. gsasl_client_callback_authentication_id_get ------------------------------------------- -- Function: Gsasl_client_callback_authentication_id gsasl_client_callback_authentication_id_get (Gsasl * CTX) CTX: libgsasl handle. *Return value:* Returns the callback earlier set by calling `gsasl_client_callback_authentication_id_set()'. *Deprecated:* This function is part of the old callback interface. The new interface uses `gsasl_callback_set()' to set the application callback, and uses `gsasl_callback()' or `gsasl_property_get()' to invoke the callback for certain properties. gsasl_client_callback_authorization_id_set ------------------------------------------ -- Function: void gsasl_client_callback_authorization_id_set (Gsasl * CTX, Gsasl_client_callback_authorization_id CB) CTX: libgsasl handle. CB: callback function Specify the callback function to use in the client to set the authorization identity. The function can be later retrieved using `gsasl_client_callback_authorization_id_get()'. *Deprecated:* This function is part of the old callback interface. The new interface uses `gsasl_callback_set()' to set the application callback, and uses `gsasl_callback()' or `gsasl_property_get()' to invoke the callback for certain properties. gsasl_client_callback_authorization_id_get ------------------------------------------ -- Function: Gsasl_client_callback_authorization_id gsasl_client_callback_authorization_id_get (Gsasl * CTX) CTX: libgsasl handle. *Return value:* Returns the callback earlier set by calling `gsasl_client_callback_authorization_id_set()'. *Deprecated:* This function is part of the old callback interface. The new interface uses `gsasl_callback_set()' to set the application callback, and uses `gsasl_callback()' or `gsasl_property_get()' to invoke the callback for certain properties. gsasl_client_callback_password_set ---------------------------------- -- Function: void gsasl_client_callback_password_set (Gsasl * CTX, Gsasl_client_callback_password CB) CTX: libgsasl handle. CB: callback function Specify the callback function to use in the client to set the password. The function can be later retrieved using `gsasl_client_callback_password_get()'. *Deprecated:* This function is part of the old callback interface. The new interface uses `gsasl_callback_set()' to set the application callback, and uses `gsasl_callback()' or `gsasl_property_get()' to invoke the callback for certain properties. gsasl_client_callback_password_get ---------------------------------- -- Function: Gsasl_client_callback_password gsasl_client_callback_password_get (Gsasl * CTX) CTX: libgsasl handle. *Return value:* Returns the callback earlier set by calling `gsasl_client_callback_password_set()'. *Deprecated:* This function is part of the old callback interface. The new interface uses `gsasl_callback_set()' to set the application callback, and uses `gsasl_callback()' or `gsasl_property_get()' to invoke the callback for certain properties. gsasl_client_callback_passcode_set ---------------------------------- -- Function: void gsasl_client_callback_passcode_set (Gsasl * CTX, Gsasl_client_callback_passcode CB) CTX: libgsasl handle. CB: callback function Specify the callback function to use in the client to set the passcode. The function can be later retrieved using `gsasl_client_callback_passcode_get()'. *Deprecated:* This function is part of the old callback interface. The new interface uses `gsasl_callback_set()' to set the application callback, and uses `gsasl_callback()' or `gsasl_property_get()' to invoke the callback for certain properties. gsasl_client_callback_passcode_get ---------------------------------- -- Function: Gsasl_client_callback_passcode gsasl_client_callback_passcode_get (Gsasl * CTX) CTX: libgsasl handle. *Return value:* Returns the callback earlier set by calling `gsasl_client_callback_passcode_set()'. *Deprecated:* This function is part of the old callback interface. The new interface uses `gsasl_callback_set()' to set the application callback, and uses `gsasl_callback()' or `gsasl_property_get()' to invoke the callback for certain properties. gsasl_client_callback_pin_set ----------------------------- -- Function: void gsasl_client_callback_pin_set (Gsasl * CTX, Gsasl_client_callback_pin CB) CTX: libgsasl handle. CB: callback function Specify the callback function to use in the client to chose a new pin, possibly suggested by the server, for the SECURID mechanism. This is not normally invoked, but only when the server requests it. The function can be later retrieved using `gsasl_client_callback_pin_get()'. *Deprecated:* This function is part of the old callback interface. The new interface uses `gsasl_callback_set()' to set the application callback, and uses `gsasl_callback()' or `gsasl_property_get()' to invoke the callback for certain properties. gsasl_client_callback_pin_get ----------------------------- -- Function: Gsasl_client_callback_pin gsasl_client_callback_pin_get (Gsasl * CTX) CTX: libgsasl handle. *Return value:* Returns the callback earlier set by calling `gsasl_client_callback_pin_set()'. *Deprecated:* This function is part of the old callback interface. The new interface uses `gsasl_callback_set()' to set the application callback, and uses `gsasl_callback()' or `gsasl_property_get()' to invoke the callback for certain properties. gsasl_client_callback_service_set --------------------------------- -- Function: void gsasl_client_callback_service_set (Gsasl * CTX, Gsasl_client_callback_service CB) CTX: libgsasl handle. CB: callback function Specify the callback fu