Illustration 1.1: Logical overview showing how applications use authentication mechanisms through an abstract interface.
This manual was last updated 22 May 2012 for version 1.8.0 of GNU SASL.
Copyright © 2002-2012 Simon Josefsson.
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled “GNU Free Documentation License”.
Appendices
Indices
This manual can be used in several ways. If read from the beginning to the end, it gives the reader an understanding of the SASL framework and the GNU SASL implementation, and how the GNU SASL library is 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.
SASL is a framework for application protocols, such as SMTP or IMAP, to add authentication support. For example, SASL is used to prove to the server who you are when you access an IMAP server to read your e-mail.
The SASL framework does not specify the technology used to perform the authentication, that is the responsibility for each SASL mechanism. Popular SASL mechanisms include CRAM-MD5 and GSSAPI (for Kerberos V5).
Typically a SASL negotiation works as follows. First the client requests authentication (possibly implicitly by connecting to the server). The server responds with a list of supported mechanisms. The client chose one of the mechanisms. The client and server then exchange data, one round-trip at a time, until authentication either succeeds or fails. After that, the client and server knows more about who is on the other end of the channel.
For example, in SMTP communication happens like this:
250-mail.example.com Hello pc.example.org [192.168.1.42], pleased to meet you
250-AUTH DIGEST-MD5 CRAM-MD5 LOGIN PLAIN
250 HELP
AUTH CRAM-MD5
334 PDk5MDgwNDEzMDUwNTUyMTE1NDQ5LjBAbG9jYWxob3N0Pg==
amFzIDBkZDRkODZkMDVjNjI4ODRkYzc3OTcwODE4ZGI5MGY3
235 2.0.0 OK Authenticated
Here the first three lines are sent by the server and contains the list of supported mechanisms (DIGEST-MD5, CRAM-MD5, etc). The next line is sent by the client to select the CRAM-MD5 mechanism. The server replies with a challenge, which is a message that can be generated by calling GNU SASL functions. The client replies with a response, which also is a message that can be generated by GNU SASL functions. Depending on the mechanism, there can be more than one round trip, so do not assume all authentication exchanges consists of one message from the server and one from the client. The server accepts the authentication. At that point it knows it is talking to a authenticated client, and the application protocol can continue.
Essentially, your application is responsible for implementing the framing protocol (e.g., SMTP or XMPP) according to the particular specifications. Your application uses GNU SASL to generate the authentication messages.
GNU SASL is an implementation of the Simple Authentication and Security Layer framework and a few common SASL mechanisms.
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 ANONYMOUS, CRAM-MD5,
DIGEST-MD5, EXTERNAL, GS2-KRB5, GSSAPI, LOGIN, NTLM, PLAIN,
SCRAM-SHA-1, SCRAM-SHA-1-PLUS, SAML20, OPENID20, and SECURID
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 utilizes 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 supports client and server mode, and the IMAP and SMTP protocols, fits in under 80kb on an Intel x86 platform, without any modifications to the code. (This figure was accurate as of version 1.1.)
The design of the library and the intended interaction between applications and the library through the official API is illustrated below.
Illustration 1.1: Logical overview showing how applications use authentication mechanisms through an abstract interface.
GNU SASL might have a couple of advantages over other libraries doing a similar job.
Note that the library does 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.
The GNU SASL library does not have any required external dependencies, but some optional features are enabled if you have a specific external library.
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://www.gnutls.org/) 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.
GNU SASL has at some point in time been tested on the following platforms. Daily online build reports are available at http://autobuild.josefsson.org/gsasl/.
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.
armv4l-unknown-linux-gnu.
alphaev67-dec-osf5.1,
alphaev68-dec-osf5.1.
alphaev6-unknown-linux-gnu,
alphaev67-unknown-linux-gnu.
ia64-unknown-linux-gnu.
alphaev6-unknown-linux-gnu,
alphaev67-unknown-linux-gnu, ia64-unknown-linux-gnu.
i686-pc-linux-gnu.
i686-pc-linux-gnu.
i686-pc-linux-gnu.
i686-pc-linux-gnu.
mips-sgi-irix6.5.
rs6000-ibm-aix4.3.2.0.
i686-pc-cygwin.
ia64-hp-hpux11.22,
hppa2.0w-hp-hpux11.11.
sparc-sun-solaris2.8.
sparc-sun-solaris2.9.
alpha-unknown-netbsd1.6,
i386-unknown-netbsdelf1.6.
alpha-unknown-openbsd3.1,
i386-unknown-openbsd3.1.
alpha-unknown-freebsd4.7,
i386-unknown-freebsd4.7.
m68k-uclinux-elf.
If you port GNU SASL to a new platform, please report it to the author so this list can be updated.
A mailing list where users may help each other exists, and you can reach it by sending e-mail to help-gsasl@gnu.org. 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/.
Commercial support is available for users of GNU SASL. The kind of support that can be purchased may include:
If you are interested, please write to:
Simon Josefsson Datakonsult AB Hagagatan 24 113 47 Stockholm Sweden E-mail: simon@josefsson.org
If your company provides support related to GNU SASL and would like to be mentioned here, contact the author (see Bug Reports).
The package can be downloaded from several places, including:
The latest version is stored in a file, e.g., ‘gsasl-1.8.0.tar.gz’ where the ‘1.8.0’ 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 downloads, configures, builds and install the package. You will need a few basic tools, such as ‘sh’, ‘make’ and ‘cc’.
$ wget -q ftp://ftp.gnu.org/gnu/gsasl/gsasl-1.8.0.tar.gz
$ tar xfz gsasl-1.8.0.tar.gz
$ cd gsasl-1.8.0/
$ ./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--disable-server, the function will return an error code.
--disable-obsolete--disable-anonymous--disable-external--disable-plain--disable-login--disable-securid--disable-ntlm--disable-cram-md5--disable-digest-md5--disable-gssapi--disable-gs2--enable-kerberos_v5--disable-scram-sha1--disable-saml20--disable-openid20--without-stringprepFor the complete list, refer to the output from configure
--help.
There are two ways to build GNU SASL on Windows: via MinGW or via Microsoft Visual Studio. Note that a binary release for Windows is available from http://josefsson.org/gnutls4win/.
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 (see 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 (see 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 Build
Project.
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. The code will attempt to use the Intel RND crypto
provider if it is installed, see lib/gl/gc-gnulib.c.
Building GNU SASL with support for Kerberos via GSS-API on Windows is straight forward if you use GNU GSS and GNU Shishi as the Kerberos implementation.
If you are using MIT Kerberos for Windows (KfW), getting GNU SASL to build with Kerberos support is not straightforward because KfW does not follow the GNU coding style and it has bugs that needs to be worked around. We provide instructions for this environment as well, in the hope that it will be useful for GNU SASL users.
Our instructions assumes you are building the software on a dpkg-based GNU/Linux systems (e.g., gNewSense) using the MinGW cross-compiler suite. These instructions were compiled for KfW version 3.2.2 which were the latest as of 2010-09-25.
We assume that you have installed a normal build environment including the MinGW cross-compiler. Download and unpack the KfW SDK like this:
$ mkdir ~/kfw
$ cd ~/kfw
$ wget -q http://web.mit.edu/kerberos/dist/kfw/3.2/kfw-3.2.2/kfw-3-2-2-sdk.zip
$ unzip kfw-3-2-2-sdk.zip
Fix a bug in the "win-mac.h" header inside KfW by replacing
#include <sys\foo.h> with #include <sys/foo.h>:
perl -pi -e 's,sys\\,sys/,' ~/kfw/kfw-3-2-2-final/inc/krb5/win-mac.h
Unpack your copy of GNU SASL:
$ wget -q ftp://alpha.gnu.org/gnu/gsasl/gsasl-1.8.0.tar.gz
$ tar xfz gsasl-1.8.0.tar.gz
$ cd gsasl-1.8.0
Configure GNU SASL like this:
$ lt_cv_deplibs_check_method=pass_all ./configure --host=i586-mingw32msvc --build=i686-pc-linux-gnu --with-gssapi-impl=kfw LDFLAGS="-L$HOME/kfw/kfw-3-2-2-final/lib/i386" CPPFLAGS="-I$HOME/kfw/kfw-3-2-2-final/inc/krb5 -DSSIZE_T_DEFINED"
The 'lt_cv_deplibs_check_method=pass_all' setting is required because
the KfW SDK does not ship with Libtool *.la files and is using
non-standard DLL names. The -DSSIZE_T_DEFINED is necessary
because the win-mac.h file would provide an incorrect duplicate
definitions of ssize_t otherwise. By passing
--with-gssapi-impl=kfw you activate other bug workarounds, such
as providing a GSS_C_NT_HOSTBASED_SERVICE symbol.
Build the software using:
$ make
If you have Wine installed and your kernel is able to invoke it automatically for Windows programs, you can run the self tests. This is recommended to make sure the build is sane.
$ make check
You may get error messages about missing DLLs, like this error:
err:module:import_dll Library gssapi32.dll (which is needed by L"Z:\\home\\jas\\src\\gsasl-1.5.2\\lib\\src\\.libs\\libgsasl-7.dll") not found
If that happens, you need to make sure that Wine can find the
appropriate DLL. The simplest solution is to copy the necessary DLLs
to ~/.wine/drive_c/windows/system32/.
You may now copy the following files onto the Windows machine (e.g., through a USB memory device):
lib/src/.libs/libgsasl-7.dll
src/.libs/gsasl.exe
The remaining steps are done on the Windows XP machine. Install KfW and configure it for your realm. To make sure KfW is working properly, acquire a user ticket and then remove it. For testing purposes, you may use the realm 'interop.josefsson.org' with KDC 'interop.josefsson.org' and username 'user' and password 'pass'.
Change to the directory where you placed the files above, and invoke a command like this:
gsasl.exe -d interop.josefsson.org
KfW should query you for a password, and the tool should negotiate authentication against the server using GS2-KRB5.
If you think you have found a bug in GNU SASL, please investigate it and report it.
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:
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 (see 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:
If you normally code using another coding standard, there is no problem, but you should use ‘indent’ to reformat the code (see GNU Indent) before submitting your work.
malloc return NULL,
should work although result in an error code.
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 (see Examples).
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 <gsasl.h>
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.
The library must be initialized before it can be used. The library is
initialized by calling gsasl_init (see 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 (see 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 Libgcrypt1, 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. Here is example code to initialize secure memory in your code:
#include <gcrypt.h>
...
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 applications, is not the biggest secure problem anyway). Note that the GNU SASL Library has not been audited to make sure it stores passwords or keys in secure memory.
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 may actually be used. So you may want to check that the version is okay right after program startup.
req_version: version string to compare with, or NULL.
Check GNU SASL Library version.
See
GSASL_VERSIONfor a suitablereq_versionstring.This function is one of few in the library that can be used without a successful call to
gsasl_init().Return value: Check that the version of the library is at minimum the one given as a string in
req_versionand 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);
}
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 compiler 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 library (for instance, the ‘-lidn’ option). The example shows how to link foo.o with the 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`
If you work on a project that uses Autoconf (see GNU Autoconf) 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.
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 example illustrates this scenario.
AC_ARG_ENABLE(gsasl,
AC_HELP_STRING([--disable-gsasl], [don't use GNU SASL]),
gsasl=$enableval)
if test "$gsasl" != "no" ; then
PKG_CHECK_MODULES(GSASL, libgsasl >= 1.8.0,
[gsasl=yes],
[gsasl=no])
if test "$gsasl" != "yes" ; then
gsasl=no
AC_MSG_WARN([Cannot find GNU SASL, disabling])
else
gsasl=yes
AC_DEFINE(USE_GSASL, 1, [Define to 1 if you want GNU SASL.])
fi
fi
AC_MSG_CHECKING([if GNU SASL should be used])
AC_MSG_RESULT($gsasl)
If your package uses Libtool (see GNU Libtool), 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 example illustrates 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)
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 illustrates this.
The third step may look complex, but for a simple client it will actually not involve any code. If your application needs to handle several concurrent clients, or if it is a server that needs 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 a username and password, 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 the main function in our client
(see 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, having several clients running
simultaneous, instead of a simple call to 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. These are the steps: 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 continues until authentication succeeds or an error occurs. The format of the data to be transferred, 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 does not send data to the server itself, but returns it in an buffer. You must send it to the server, following an application protocol profile. For example, the SASL application protocol profile for SMTP is described in RFC 2554.
The following image illustrates 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 (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 creates a new
session, then it stores the username and password in the session
handle, then it calls another function client_authenticate to
handle the authentication loop, and finally it cleans up up. Let's
continue with the implementation of client_authenticate.
void client_authenticate (Gsasl_session * session)
{
char buf[BUFSIZ] = "";
char *p;
int rc;
/* This loop mimics a protocol where the server sends 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 needs 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 (see Example 2) is used for application profiles where the server sends data first. For some mechanisms, this may waste a roundtrip, because the server needs input from the client to proceed. Therefor, today the recommended approach is to permit client to send data first (see Example 1). Which version you should use depends 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 function gsasl_step64 (and of course also gasl_step)
returns two non-error return codes. GSASL_OK is used for
success, indicating that the library considers 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 replies “OK” but these
functions have 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
concludes 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.
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 mechanisms 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
(see Global Functions) that will try to pick the “best”
available mechanism from a list of mechanisms. Our simple interactive
example client (see Example 3) includes 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, rather it
lets 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 server supported mechanisms, separate by SPC:\n");
fgets (mechlist, sizeof (mechlist) - 1, stdin);
suggestion = gsasl_client_suggest_mechanism (ctx, mechlist);
if (suggestion)
printf ("Library suggests 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 server supported mechanisms, separate by SPC:
CRAM-MD5 DIGEST-MD5 GSSAPI FOO BAR
Library suggests 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.
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 need only a username and a password. But some mechanism requires 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 aborts the authentication process? Then your application has 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 needs 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 aborts, e.g., a password prompt, the mechanism is directly informed of this (because it invoked the callback), and could recover somehow.
Our final example (see Example 4) specifies 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 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.
The library uses a concept called “properties” to request and pass
data between the application and the individual authentication
mechanisms. The application can set property values using the
gsasl_property_set function. If a mechanism needs a property
value the application has not yet provided, this is handled through a
callback. The application provides a callback, using
gsasl_callback_set, which will be invoked with a property
parameter. The callback should set the property before returning, or
fail. See Callback Functions, for more information.
There are two kind of properties. The first, a “data property” is
the simplest to understand because it normally refers to short
strings. For example, the property called GSASL_AUTHID
correspond to the username string, e.g., simon.
The latter properties, called “logical properties”, are used by the
server to make a authentication decision, and is used as a way to get
the application callback invoked. For example, the property
GSASL_VALIDATE_SIMPLE is used by the server-side part of
mechanisms like PLAIN. The purpose is to ask the server
application to decide whether the user should be authenticated
successfully or not. The callback typically look at other property
fields, such as GSASL_AUTHID and GSASL_PASSWORD, and
compare those values with external information (for example data
stored in a database or on a LDAP server) and then return OK or not.
Warning: Don't expect that all mechanisms invoke one of the logical properties in the server mode. For example, the CRAM-MD5 and SCRAM-SHA-1 mechanisms will use the data properties (i.e., username and password) provided by the application to internally decide whether to successfully authenticate the user. User authorization decisions needs to be made by the application outside of the SASL mechanism negotiation.
The logical properties are currently only used by servers, but data properties are used by both client and servers. It makes sense to think about the latter category as ‘server properties’ but the reverse is not valid nor useful.
The semantics associated with a data property is different when it is
used in client context and in the server context. For example, in the
client context, the application is expected to set the property
GSASL_AUTHID to signal to the mechanism the username to use,
but in the server context, the GSASL_AUTHID property is set by
the mechanism and can be used by the application (in the callback) to
find out what username the client provided.
Below is a list of all properties and an explanation for each. First is the list of data properties:
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.
GSASL_DIGEST_MD5_HASHED_PASSWORD
For the DIGEST-MD5 mechanism, this is a hashed password. It is used in servers to avoid storing clear-text credentials.
GSASL_QOPS
The DIGEST-MD5 server query for this property to get the set of
quality of protection (QOP) values to advertise. The property holds
strings with comma separated keywords denoting the set of qops to use,
for example qop-auth, qop-int. Valid keywords are
qop-auth, qop-int, and qop-conf.
GSASL_QOP
The DIGEST-MD5 client query for this property to get the quality of
protection (QOP) values to request. The property value is one of the
keywords for GSASL_QOPS. The client must chose one of the QOP
values offered by the server (which may be inspected through the
GSASL_QOPS property).
GSASL_SCRAM_SALTED_PASSWORD
The SCRAM-SHA-1 client requests this property from the application,
and the value should be 40 character long hex-encoded string with the
user's hashed password. Note that the value is different for the same
password for each value of the GSASL_SCRAM_ITER and
GSASL_SCRAM_ITER properties. The property can be used to avoid
storing a clear-text credential in the client. If the property is not
available, the client will ask for the GSASL_PASSWORD property
instead.
GSASL_SCRAM_ITER
GSASL_SCRAM_ITER
In the server, the application can set these properties to influence
the hash iteration count and hash salt to use when deriving the
password. The default hash iteration count is 4096 and normally you
should not need to use a lower setting. The salt should be a random
string. In the client, the SCRAM-SHA-1 mechanism set these properties
before asking for asking the application to provide a
GSASL_SCRAM_SALTED_PASSWORD value.
GSASL_CB_TLS_UNIQUE
This property holds base64 encoded tls-unique channel binding
data. As a hint, if you use GnuTLS, the API
gnutls_session_channel_binding can be used to extract channel
bindings for a session.
GSASL_SAML20_IDP_IDENTIFIER
This property holds the SAML identifier of the user. The SAML20
mechanism in client mode will send it to the other end for
identification purposes, and in server mode it will be accessible in
the GSASL_SAML20_REDIRECT_URL callback.
GSASL_SAML20_REDIRECT_URL
This property holds the SAML redirect URL that the server wants the
client to access. It will be available in the
GSASL_SAML20_AUTHENTICATE_IN_BROWSER callback for the client.
GSASL_OPENID20_REDIRECT_URL
This property holds the SAML redirect URL that the server wants the
client to access. It will be available in the
GSASL_OPENID20_AUTHENTICATE_IN_BROWSER callback for the client.
GSASL_OPENID20_OUTCOME_DATA
OpenID 2.0 authentication outcome data. This is either the OpenID
SREG values or a value list starting with "openid.error=" to
signal error.
Next follows a list of data properties used to trigger the callback, typically used in servers to validate client credentials:
GSASL_VALIDATE_SIMPLE
Used by multiple mechanisms in server mode. The callback may retrieve
the GSASL_AUTHID, GSASL_AUTHZID and
GSASL_PASSWORD property values 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 and GS2-KRB5 mechanisms 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.
GSASL_VALIDATE_SAML20
Used by the SAML20 mechanism on the server side to request that the
application perform authentication. The callback should return
GSASL_OK if the user should be permitted access, and
GSASL_AUTHENTICATION_ERROR (or another error code) otherwise.
GSASL_VALIDATE_OPENID20
Used by the OPENID20 mechanism on the server side to request that the
application perform authentication. The callback should return
GSASL_OK if the user should be permitted access, and
GSASL_AUTHENTICATION_ERROR (or another error code) otherwise.
GSASL_SAML20_AUTHENTICATE_IN_BROWSER
Used by the SAML20 mechanism in the client side to request that the
client should launch the SAML redirect URL (the
GSASL_SAML20_REDIRECT_URL property) in a browser to continue
with authentication.
GSASL_OPENID20_AUTHENTICATE_IN_BROWSER
Used by the OPENID20 mechanism in the client side to request that the
client should launch the OpenID redirect URL (the
GSASL_OPENID20_REDIRECT_URL property) in a browser to continue
with authentication.
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 queries the user for a username and password. The server callback hands the username and password into any local policy deciding authentication system (such as /etc/passwd via PAM).
Mechanism such as ‘CRAM-MD5’ and ‘SCRAM-SHA-1’ uses hashed passwords. The client callback behaviour is the same as for PLAIN. However, the server does 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/GS2-KRB5 (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.
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 to use TLS, since it also supports anonymous modes.
In the client, this mechanism is always enabled, and it 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 request the
GSASL_VALIDATE_EXTERNAL callback property 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.
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.
The PLAIN mechanism uses username and password to authenticate users. Two user names are relevant. The first, the authentication identity, indicates 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 are provided.
In the first approach, the server side of the mechanism will request
the GSASL_VALIDATE_SIMPLE callback property to decide whether
the client should be accepted or not. The callback may inspect the
GSASL_AUTHID, GSASL_AUTHZID, and GSASL_PASSWORD
properties. These property values will be normalized.
If the first approach fails (because, e.g., your callback returns
‘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 stores 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.
The LOGIN mechanism is a non-standard mechanism, and is similar to the PLAIN mechanism except that LOGIN lacks 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 neither used nor required, and that the server
does not normalize the password using SASLprep.
See Use of SASLprep in LOGIN, for a proposed clarification of the interpretation of a hypothetical LOGIN specification.
The CRAM-MD5 is a widely used, but officially deprecated (apparently in favor of DIGEST-MD5), challenge-response mechanism that transfers 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 does 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 it requires the
GSASL_AUTHID and GSASL_PASSWORD properties.
In the server, the mechanism will require the GSASL_PASSWORD
callback property, 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.
See Use of SASLprep in CRAM-MD5, for a clarification on the interpretation of the CRAM-MD5 specification that this implementation rely on.
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 transferred. Consequently, DIGEST-MD5 needs access to the correct password (although it may be hashed, another improvement compared to CRAM-MD5) to verify the client response. Alas, this makes it impossible to use, e.g., PAM on the server side.
In the client, this mechanism is always enabled, and it requires 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 first request the
GSASL_DIGEST_MD5_HASHED_PASSWORD callback property to get the
user's hashed password. If the callback doesn't supply a hashed
password, the GSASL_PASSWORD callback property will be
requested. Both callbacks 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.
The server uses the GSASL_QOPS callback to get the set of
quality of protection values to use. By default, it advertises
support for authentication (qop-auth) only. You can use the
callback, for example, to make the server advertise support for
authentication with integrity layers.
The client uses the GSASL_QOP callback to get the quality of
protection value to request. The client must choose one of the QOP
values offered by the server (which may be inspected through the
GSASL_QOPS property). If the client does not return a value,
qop-auth is used by default.
The SCRAM-SHA-1 mechanism is designed to provide (almost) the same capabilities as CRAM-MD5 and DIGEST-MD5 but use modern cryptographic techniques such as HMAC-SHA-1 hashing and PKCS#5 PBKDF2 key derivation. SCRAM-SHA-1 supports authorization identities. Like CRAM-MD5 and DIGEST-MD5, only a hashed password is transferred. Consequently, SCRAM-SHA-1 needs access to the correct password to verify the client response. Channel bindings are supported through the SCRAM-SHA-1-PLUS mechanism.
In the client, the non-PLUS mechanism is always enabled, and it
requires the GSASL_AUTHID property, and either
GSASL_PASSWORD or GSASL_SCRAM_SALTED_PASSWORD. When the
GSASL_CB_TLS_UNIQUE property is available, the SCRAM-SHA-1-PLUS
mechanism is also available and it will negotiate channel bindings
when the server also supports it. If set, GSASL_AUTHZID will
be used by the client. To be able to return the proper
GSASL_SCRAM_SALTED_PASSWORD value, the client needs to check
the GSASL_SCRAM_ITER and GSASL_SCRAM_SALT values which
are available when the GSASL_SCRAM_SALTED_PASSWORD property is
queried for.
In the server, the mechanism will require the GSASL_PASSWORD
callback property, 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. The
server may also set the GSASL_SCRAM_ITER and
GSASL_SCRAM_SALT properties to influence the values to be used
by clients to derive a key from a password. When the
GSASL_CB_TLS_UNIQUE property is set, the SCRAM-SHA-1-PLUS
mechanism is supported and is used to negotiate channel bindings.
The GSASL_CB_TLS_UNIQUE property signal that this side of the
authentication supports channel bindings. Setting the property will
enable the SCRAM-SHA-1-PLUS mechanism. For clients, this also
instructs the SCRAM-SHA-1 mechanism to tell servers that the client
believes the server does not support channel bindings if it is used
(remember that clients should otherwise have chosen the
SCRAM-SHA-1-PLUS mechanism instead of the SCRAM-SHA-1 mechanism). For
servers, it means the SCRAM-SHA-1 mechanism will refuse to
authenticate against a client that signals that it believes the server
does not support channel bindings.
The SCRAM-SHA-1-PLUS mechanism will never complete authentication successfully if channel bindings are not confirmed.
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 it requires 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.
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 it requires 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 is 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.
The GSSAPI mechanism allows you to authenticate using Kerberos V5. The mechanism was originally designed to allow for any GSS-API mechanism to be used, but problems with the protocol made it unpractical and it is today restricted for use with Kerberos V5. See the GS2 mechanism (see GS2-KRB5) for a general solution.
In the client, the mechanism is enabled only if the user has acquired
credentials (i.e., a ticket granting ticket), and it requires the
GSASL_AUTHID, GSASL_SERVICE, and GSASL_HOSTNAME
properties.
In the server, the mechanism requires the GSASL_SERVICE and
GSASL_HOSTNAME properties, and it will invoke the
GSASL_VALIDATE_GSSAPI callback property 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.
GS2 is a protocol bridge between GSS-API and SASL, and allows every GSS-API mechanism that supports mutual authentication and channel bindings to be used as a SASL mechanism. Currently we support the GS2-KRB5 mechanism, for Kerberos V5 authentication, however our GS2 implementation is flexible enough to easily support other GSS-API mechanism if any gains popularity.
In the client, the mechanism is enabled only if the user has acquired
credentials (i.e., a ticket granting ticket), and it requires the
GSASL_AUTHID, GSASL_SERVICE, and GSASL_HOSTNAME
properties.
In the server, the mechanism requires the GSASL_SERVICE and
GSASL_HOSTNAME properties, and it will invoke the
GSASL_VALIDATE_GSSAPI callback property 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.
The GS2 framework supports a variant of each mechanism, called the PLUS variant, which can also bind the authentication to a secure channel through channel bindings. Currently this is not supported by GNU SASL.
The SAML20 mechanism makes it possible to use SAML in SASL, in a way that offloads the authentication exchange to an external browser. The protocol implemented is as specified in RFC 6595.
The mechanism makes use of the following properties: GSASL_AUTHZID,
GSASL_SAML20_IDP_IDENTIFIER, GSASL_SAML20_REDIRECT_URL,
GSASL_SAML20_AUTHENTICATE_IN_BROWSER and
GSASL_VALIDATE_SAML20.
In client mode, the mechanism will retrieve the GSASL_AUTHZID and
GSASL_SAML20_IDP_IDENTIFIER properties and form a request to the
server. The server will respond with a redirect URL stored in the
GSASL_SAML20_REDIRECT_URL property, which the client can retrieve
from the GSASL_SAML20_AUTHENTICATE_IN_BROWSER callback. The
intention is that the client launches a browser to the given URL, and
then proceeds with authentication. The server responds whether
authentication was successful or not.
In server mode, the mechanism will invoke the
GSASL_SAML20_REDIRECT_URL callback and the application can
inspect the GSASL_AUTHZID and GSASL_SAML20_IDP_IDENTIFIER
properties when forming the redirect URL. The URL is passed to the
client which will hopefully complete authentication in the browser. The
server callback GSASL_VALIDATE_SAML20 should check whether the
authentication attempt was successful.
Note that SAML itself is not implemented by the GNU SASL library. On
the client side, no SAML knowledge is needed, it is only required on the
server side. The client only needs to be able to start a browser
accessing the redirect URL. The server side is expected to call a SAML
library of your choice to generate the AuthRequest and to implement an
AssertionConsumerService to validate the AuthResponse. There is a
complete proof-of-concept example of a SMTP server with SAML 2.0 support
distributed with GNU SASL in the examples/saml20/ sub-directory. It
uses the Lasso SAML implementation (http://lasso.entrouvert.org/).
The example may be used as inspiration for your own server
implementation. The gsasl command line client supports SAML20 as
a client.
The OPENID20 mechanism makes it possible to use OpenID in SASL, in a way that offloads the authentication exchange to an external browser. The protocol implemented is as specified in RFC 6616.
The mechanism makes use of the following properties:
GSASL_AUTHID (for the OpenID User-Supplied Identifier),
GSASL_AUTHZID, GSASL_OPENID20_REDIRECT_URL,
GSASL_OPENID20_OUTCOME_DATA,
GSASL_OPENID20_AUTHENTICATE_IN_BROWSER, and
GSASL_VALIDATE_OPENID20.
In the client, the mechanism is enabled by default. The
GSASL_AUTHID property is required and should contain the
User-Supplied OpenID Identifier (for example
http://josefsson.org). If set, GSASL_AUTHZID will be
used by the client. The client will be invoked with the
GSASL_OPENID20_AUTHENTICATE_IN_BROWSER callback to perform the
OpenID authentication in a web browser. The callback can retrieve the
GSASL_OPENID20_REDIRECT_URL property to find out the URL to
redirect the user to. After authentication, the client can retrieve
the GSASL_OPENID20_OUTCOME_DATA property with the OpenID Simple
Registry (SREG) attributes sent by the server (they are not always
sent).
In the server, the mechanism is enabled by default. The server will
request the GSASL_OPENID20_REDIRECT_URL property, and your
callback may inspect the GSASL_AUTHID to find the OpenID
User-Supplied Identifier. The server callback should perform OpenID
discovery and return the URL to redirect the user to. After this, the
user would access the URL and proceed with authentication in the
browser. The server is invoked with the
GSASL_VALIDATE_OPENID20 callback to perform the actual
validation of the authentication. Usually the callback will perform
some IPC communication with an OpenID consumer running in a web
server. The callback should return GSASL_OK on successful
authentication and GSASL_AUTHENTICATION_ERROR on authentication
errors, or any other error code. If the server received some OpenID
Simple Registry (SREG) attributes from the OpenID Identity Provider,
it may use the GSASL_OPENID20_OUTCOME_DATA property to send
these to the client.
Note that OpenID itself is not implemented by the GNU SASL library. On
the client side, no OpenID knowledge is required, it is only required on
the server side. The client only needs to be able to start a browser
accessing the redirect URL. The server side is expected to use an
OpenID library of your choice to generate the redirect URL and to
implement the Service Provider to validate the response from the IdP.
There is a complete proof-of-concept example with a SMTP server with
OpenID 2.0 support distributed with GNU SASL in the examples/openid20/
sub-directory. It uses the JanRain PHP5 OpenID implementation. The
example may be used as inspiration for your own server implementation.
The gsasl command line client supports OPENID20 as a client.
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 acquire 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), neither 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
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.
ctx: libgsasl handle.
This function destroys a libgsasl handle. The handle must not be used with other libgsasl functions after this call.
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.
outis allocated by this function, and it is the responsibility of caller to deallocate it.Return value: Returns
GSASL_OKif successful, or error code.
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.
outis allocated by this function, and it is the responsibility of caller to deallocate it.Return value: Returns
GSASL_OKif successful, or error code.
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.
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.
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, or NULL if no supported mechanism is found.
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_OKiff successful, otherwiseGSASL_MALLOC_ERROR.Since: 0.2.0
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 access to data from other parts of your
application, there are hooks to store and retrieve application
specific pointers. This avoids the use of global variables, 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.
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, forGSASL_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
ctx: handle received from
gsasl_init(), may be NULL to derive it fromsctx.sctx: session handle.
prop: enumerated value of Gsasl_property type.
Invoke the application callback. The
propvalue indicate what the callback is expected to do. For example, forGSASL_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 returns, or
GSASL_NO_CALLBACKif no application was known.Since: 0.2.0
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
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
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
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
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
dataand store it in the session handle for the indicated propertyprop.You can immediately deallocate
dataafter calling this function, without affecting the data stored in the session handle.Since: 0.2.0
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
lensizeddataand store a zero terminated version of it in the session handle for the indicated propertyprop.You can immediately deallocate
dataafter 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
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
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
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_OKif successful, or error code.
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_OKif successful, or error code.
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
inputandinput_len), processes it (potentially invoking callbacks to the application), and writes data to server (into newly allocated variableoutputandoutput_lenthat indicate the length ofoutput).The contents of the
outputbuffer is unspecified if this functions returns anything other thanGSASL_OKorGSASL_NEEDS_MORE. If this function returnGSASL_OKorGSASL_NEEDS_MORE, however, theoutputbuffer is allocated by this function, and it is the responsibility of caller to deallocate it by calling free (output).Return value: Returns
GSASL_OKif authenticated terminated successfully,GSASL_NEEDS_MOREif more data is needed, or error code.
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
b64outputbuffer is unspecified if this functions returns anything other thanGSASL_OKorGSASL_NEEDS_MORE. If this function returnGSASL_OKorGSASL_NEEDS_MORE, however, theb64outputbuffer is allocated by this function, and it is the responsibility of caller to deallocate it by calling free (b64output).Return value: Returns
GSASL_OKif authenticated terminated successfully,GSASL_NEEDS_MOREif more data is needed, or error code.
sctx: libgsasl session handle.
Destroy a libgsasl client or server handle. The handle must not be used with other libgsasl functions after this call.
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
outputbuffer is allocated by this function, and it is the responsibility of caller to deallocate it by calling free(output).Return value: Returns
GSASL_OKif encoding was successful, otherwise an error code.
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
outputbuffer is allocated by this function, and it is the responsibility of caller to deallocate it by calling free(output).Return value: Returns
GSASL_OKif encoding was successful, otherwise an error code.
sctx: libgsasl session handle.
This function returns the name of the SASL mechanism used in the session.
Return value: Returns a zero terminated character array with the name of the SASL mechanism, or NULL if not known.
Since: 0.2.28
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
outvariable must be deallocated by the caller.Return value: Returns
GSASL_OKon success, orGSASL_SASLPREP_ERRORon error.Since: 0.2.3
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
outlenholds the length excluding the terminating zero. Theoutbuffer must be deallocated by the caller.Return value: Returns
GSASL_OKon success, orGSASL_MALLOC_ERRORif input was too large or memory allocation fail.Since: 0.2.2
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
outbuffer must be deallocated by the caller.Return value: Returns
GSASL_OKon success,GSASL_BASE64_ERRORif input was invalid, andGSASL_MALLOC_ERRORon memory allocation errors.Since: 0.2.2
filename: filename of file containing passwords.
username: username string.
key: newly allocated output character array.
Retrieve password for user from specified file. The buffer
keycontain 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_OKif output buffer contains the password,GSASL_AUTHENTICATION_ERRORif the user could not be found, or other error code.
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_OKiff successful.
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_OKiff successful.
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
outbuffer must be deallocated by the caller.Return value: Returns
GSASL_OKiff successful.
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
outhashbuffer must be deallocated by the caller.Return value: Returns
GSASL_OKiff successful.
in: input character array of data to hash.
inlen: length of input character array of data to hash.
Compute hash of data using SHA1. The
outbuffer must be deallocated by the caller.Return value: Returns
GSASL_OKiff successful.Since: 1.3
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-SHA1. The
outhashbuffer must be deallocated by the caller.Return value: Returns
GSASL_OKiff successful.Since: 1.3
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
Most functions in the GNU SASL Library return 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.
Errors are returned as int values.
The value of the symbol GSASL_OK is guaranteed to always be
0, and all other error codes are guaranteed to be non-0,
so you may use that information to build boolean expressions involving
return codes. Otherwise, an application should not depend on the
particular value for error codes, and are encouraged to use the
constants even for GSASL_OK to improve readability. Possible
values are:
GSASL_OKGSASL_NEEDS_MOREGSASL_UNKNOWN_MECHANISMGSASL_MECHANISM_CALLED_TOO_MANY_TIMESGSASL_TOO_SMALL_BUFFERGSASL_FOPEN_ERRORGSASL_FCLOSE_ERRORGSASL_MALLOC_ERRORGSASL_BASE64_ERRORGSASL_CRYPTO_ERRORGSASL_NEED_CLIENT_ANONYMOUS_CALLBACKGSASL_NEED_CLIENT_PASSWORD_CALLBACKGSASL_NEED_CLIENT_PASSCODE_CALLBACKGSASL_NEED_CLIENT_PIN_CALLBACKGSASL_NEED_CLIENT_AUTHORIZATION_ID_CALLBACKGSASL_NEED_CLIENT_AUTHENTICATION_ID_CALLBACKGSASL_NEED_CLIENT_SERVICE_CALLBACKGSASL_NEED_SERVER_VALIDATE_CALLBACKGSASL_NEED_SERVER_CRAM_MD5_CALLBACKGSASL_NEED_SERVER_DIGEST_MD5_CALLBACKGSASL_NEED_SERVER_EXTERNAL_CALLBACKGSASL_NEED_SERVER_ANONYMOUS_CALLBACKGSASL_NEED_SERVER_REALM_CALLBACKGSASL_NEED_SERVER_SECURID_CALLBACKGSASL_NEED_SERVER_SERVICE_CALLBACKGSASL_NEED_SERVER_GSSAPI_CALLBACKGSASL_NEED_SERVER_RETRIEVE_CALLBACKGSASL_UNICODE_NORMALIZATION_ERRORGSASL_SASLPREP_ERRORGSASL_MECHANISM_PARSE_ERRORGSASL_AUTHENTICATION_ERRORGSASL_CANNOT_GET_CTXGSASL_INTEGRITY_ERRORGSASL_NO_MORE_REALMSGSASL_NO_CLIENT_CODEGSASL_NO_SERVER_CODEGSASL_GSSAPI_RELEASE_BUFFER_ERRORGSASL_GSSAPI_IMPORT_NAME_ERRORGSASL_GSSAPI_INIT_SEC_CONTEXT_ERRORGSASL_GSSAPI_ACCEPT_SEC_CONTEXT_ERRORGSASL_GSSAPI_UNWRAP_ERRORGSASL_GSSAPI_WRAP_ERRORGSASL_GSSAPI_ACQUIRE_CRED_ERRORGSASL_GSSAPI_DISPLAY_NAME_ERRORGSASL_GSSAPI_UNSUPPORTED_PROTECTION_ERRORGSASL_KERBEROS_V5_INIT_ERRORGSASL_KERBEROS_V5_INTERNAL_ERRORGSASL_SECURID_SERVER_NEED_ADDITIONAL_PASSCODEGSASL_SECURID_SERVER_NEED_NEW_PINGSASL_INVALID_HANDLEGSASL_NO_CALLBACKGSASL_NO_ANONYMOUS_TOKENGSASL_NO_AUTHIDGSASL_NO_AUTHZIDGSASL_NO_PASSWORDGSASL_NO_PASSCODEGSASL_NO_PINGSASL_NO_SERVICEGSASL_NO_HOSTNAMEGSASL_GSSAPI_ENCAPSULATE_TOKEN_ERRORGSASL_GSSAPI_DECAPSULATE_TOKEN_ERRORGSASL_GSSAPI_INQUIRE_MECH_FOR_SASLNAME_ERRORGSASL_GSSAPI_TEST_OID_SET_MEMBER_ERRORGSASL_GSSAPI_RELEASE_OID_SET_ERRORGSASL_NO_CB_TLS_UNIQUEGSASL_NO_SAML20_IDP_IDENTIFIERGSASL_NO_SAML20_REDIRECT_URLGSASL_NO_OPENID20_REDIRECT_URLerr: libgsasl error code
Convert return code to human readable string explanation of the reason for the particular error code.
This string can be used to output a diagnostic message to the user.
This function is one of few in the library that can be used without a successful call to
gsasl_init().Return value: Returns a pointer to a statically allocated string containing an explanation of the error code
err.
err: libgsasl error code
Convert return code to human readable string representing the error code symbol itself. For example, gsasl_strerror_name(
GSASL_OK) returns the string "GSASL_OK".This string can be used to output a diagnostic message to the user.
This function is one of few in the library that can be used without a successful call to
gsasl_init().Return value: Returns a pointer to a statically allocated string containing a string version of the error code
err, or NULL if the error code is not known.Since: 0.2.29
This chapter contains example code which illustrates how the GNU SASL Library can be used when writing your own application.
/* client.c --- Example SASL client.
* Copyright (C) 2004-2012 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 <http://www.gnu.org/licenses/>.
*
*/
#include <config.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <gsasl.h>
static void
client_authenticate (Gsasl_session * session)
{
char buf[BUFSIZ] = "";
char *p;
int rc;
/* This loop mimics 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);
gsasl_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");
p = fgets (buf, sizeof (buf) - 1, stdin);
if (p == NULL)
{
perror ("fgets");
return;
}
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 (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;
}
/* client-serverfirst.c --- Example SASL client, where server send data first.
* Copyright (C) 2004-2012 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 <http://www.gnu.org/licenses/>.
*
*/
#include <config.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <gsasl.h>
static void
client_authenticate (Gsasl_session * session)
{
char buf[BUFSIZ] = "";
char *p;
int rc;
/* This loop mimics a protocol where the server send data first. */
do
{
printf ("Input base64 encoded data from server:\n");
p = fgets (buf, sizeof (buf) - 1, stdin);
if (p == NULL)
{
perror ("fgets");
return;
}
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);
gsasl_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 (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;
}
/* client-mech.c --- Example SASL client, with a choice of mechanism to use.
* Copyright (C) 2004-2012 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 <http://www.gnu.org/licenses/>.
*
*/
#include <config.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <gsasl.h>
static void
client_authenticate (Gsasl_session * session)
{
char buf[BUFSIZ] = "";
char *p;
int rc;
/* This loop mimics a protocol where the server send data first. */
do
{
printf ("Input base64 encoded data from server:\n");
p = fgets (buf, sizeof (buf) - 1, stdin);
if (p == NULL)
{
perror ("fgets");
return;
}
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);
gsasl_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;
char *p;
printf ("Enter list of server supported mechanisms, separate by SPC:\n");
p = fgets (mechlist, sizeof (mechlist) - 1, stdin);
if (p == NULL)
{
perror ("fgets");
return NULL;
}
suggestion = gsasl_client_suggest_mechanism (ctx, mechlist);
if (suggestion)
printf ("Library suggests use of `%s'.\n", suggestion);
printf ("Enter mechanism to use:\n");
p = fgets (mech, sizeof (mech) - 1, stdin);
if (p == NULL)
{
perror ("fgets");
return NULL;
}
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 (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;
}
/* client-callback.c --- Example SASL client, with callback for user info.
* Copyright (C) 2004-2012 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 <http://www.gnu.org/licenses/>.
*
*/
#include <config.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <gsasl.h>
static void
client_authenticate (Gsasl_session * session)
{
char buf[BUFSIZ] = "";
char *p;
int rc;
/* This loop mimics a protocol where the server send data first. */
do
{
printf ("Input base64 encoded data from server:\n");
p = fgets (buf, sizeof (buf) - 1, stdin);
if (p == NULL)
{
perror ("fgets");
return;
}
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);
gsasl_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 (session);
/* Cleanup. */
gsasl_finish (session);
}
static int
callback (Gsasl * ctx, Gsasl_session * sctx, Gsasl_property prop)
{
char buf[BUFSIZ] = "";
int rc = GSASL_NO_CALLBACK;
char *p;
/* Get user info from user. */
printf ("Callback invoked, for property %d.\n", prop);
switch (prop)
{
case GSASL_PASSCODE:
printf ("Enter passcode:\n");
p = fgets (buf, sizeof (buf) - 1, stdin);
if (p == NULL)
{
perror ("fgets");
break;
}
buf[strlen (buf) - 1] = '\0';
gsasl_property_set (sctx, GSASL_PASSCODE, buf);
rc = GSASL_OK;
break;
case GSASL_AUTHID:
printf ("Enter username:\n");
p = fgets (buf, sizeof (buf) - 1, stdin);
if (p == NULL)
{
perror ("fgets");
break;
}
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;
}
/* smtp-server.c --- Example SMTP server with SASL authentication
* Copyright (C) 2012 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 <http://www.gnu.org/licenses/>.
*
*/
/* This is a minimal SMTP server with GNU SASL authentication support.
The only valid password is "sesam". This server will complete
authentications using LOGIN, PLAIN, DIGEST-MD5, CRAM-MD5, and
SCRAM-SHA-1. It accepts an optional command line parameter
specifying the service name (i.e., a numerical port number or
/etc/services name). By default it listens on port "2000". */
#include <config.h>
#include <string.h>
#include <stdlib.h>
#include <stdarg.h>
#include <netdb.h>
#include <signal.h>
#include <gsasl.h>
static int
callback (Gsasl * ctx, Gsasl_session * sctx, Gsasl_property prop)
{
int rc = GSASL_NO_CALLBACK;
switch (prop)
{
case GSASL_PASSWORD:
gsasl_property_set (sctx, prop, "sesam");
rc = GSASL_OK;
break;
default:
/* You may want to log (at debug verbosity level) that an
unknown property was requested here, possibly after filtering
known rejected property requests. */
break;
}
return rc;
}
static ssize_t
gettrimline (char **line, size_t * n, FILE * fh)
{
ssize_t s = getline (line, n, fh);
if (s >= 2)
{
if ((*line)[strlen (*line) - 1] == '\n')
(*line)[strlen (*line) - 1] = '\0';
if ((*line)[strlen (*line) - 1] == '\r')
(*line)[strlen (*line) - 1] = '\0';
printf ("C: %s\n", *line);
}
return s;
}
#define print(fh, ...) \
printf ("S: "), printf (__VA_ARGS__), fprintf (fh, __VA_ARGS__)
static void
server_auth (FILE * fh, Gsasl_session * session)
{
char *line = NULL;
size_t n = 0;
char *p;
int rc;
/* The ordering and the type of checks in the following loop has to
be adapted for each protocol depending on its SASL properties.
SMTP is a "server-first" SASL protocol. This implementation do
not support piggy-backing of the initial client challenge nor
piggy-backing of the terminating server response. See RFC 2554
and RFC 4422 for terminology. That profile results in the
following loop structure. Ask on the help-gsasl list if you are
uncertain. */
do
{
rc = gsasl_step64 (session, line, &p);
if (rc == GSASL_NEEDS_MORE || (rc == GSASL_OK && p && *p))
{
print (fh, "334 %s\n", p);
gsasl_free (p);
if (gettrimline (&line, &n, fh) < 0)
{
print (fh, "221 localhost getline failure\n");
goto done;
}
}
}
while (rc == GSASL_NEEDS_MORE);
if (rc != GSASL_OK)
{
print (fh, "535 gsasl_step64 (%d): %s\n", rc, gsasl_strerror (rc));
goto done;
}
{
const char *authid = gsasl_property_fast (session, GSASL_AUTHID);
const char *authzid = gsasl_property_fast (session, GSASL_AUTHZID);
print (fh, "235 OK [authid: %s authzid: %s]\n",
authid ? authid : "N/A", authzid ? authzid : "N/A");
}
done:
free (line);
}
static void
smtp (FILE * fh, Gsasl * ctx)
{
char *line = NULL;
size_t n = 0;
int rc;
print (fh, "220 localhost ESMTP GNU SASL smtp-server\n");
while (gettrimline (&line, &n, fh) >= 0)
{
if (strncmp (line, "EHLO ", 5) == 0 || strncmp (line, "ehlo ", 5) == 0)
{
char *mechlist;
rc = gsasl_server_mechlist (ctx, &mechlist);
if (rc != GSASL_OK)
{
print (fh, "221 localhost gsasl_server_mechlist (%d): %s\n",
rc, gsasl_strerror (rc));
goto done;
}
print (fh, "250-localhost\n");
print (fh, "250 AUTH %s\n", mechlist);
gsasl_free (mechlist);
}
else if (strncmp (line, "AUTH ", 5) == 0
|| strncmp (line, "auth ", 5) == 0)
{
Gsasl_session *session = NULL;
if ((rc = gsasl_server_start (ctx, line + 5, &session)) != GSASL_OK)
{
print (fh, "221 localhost gsasl_server_start (%d): %s\n",
rc, gsasl_strerror (rc));
goto done;
}
server_auth (fh, session);
gsasl_finish (session);
}
else if (strncmp (line, "QUIT", 4) == 0
|| strncmp (line, "quit", 4) == 0)
{
print (fh, "221 localhost QUIT\n");
goto done;
}
else
print (fh, "500 unrecognized command\n");
}
print (fh, "221 localhost getline failure\n");
done:
free (line);
}
int
main (int argc, char *argv[])
{
const char *service = argc > 1 ? argv[1] : "2000";
volatile int run = 1;
struct addrinfo hints, *addrs;
int sockfd;
int rc;
int yes = 1;
Gsasl *ctx;
setvbuf (stdout, NULL, _IONBF, 0);
rc = gsasl_init (&ctx);
if (rc < 0)
{
printf ("gsasl_init (%d): %s\n", rc, gsasl_strerror (rc));
exit (EXIT_FAILURE);
}
printf ("%s [gsasl header %s library %s]\n",
argv[0], GSASL_VERSION, gsasl_check_version (NULL));
gsasl_callback_set (ctx, callback);
memset (&hints, 0, sizeof (hints));
hints.ai_flags = AI_PASSIVE | AI_ADDRCONFIG;
hints.ai_socktype = SOCK_STREAM;
rc = getaddrinfo (NULL, service, &hints, &addrs);
if (rc < 0)
{
printf ("getaddrinfo: %s\n", gai_strerror (rc));
exit (EXIT_FAILURE);
}
sockfd = socket (addrs->ai_family, addrs->ai_socktype, addrs->ai_protocol);
if (sockfd < 0)
{
perror ("socket");
exit (EXIT_FAILURE);
}
if (setsockopt (sockfd, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof (yes)) < 0)
{
perror ("setsockopt");
exit (EXIT_FAILURE);
}
rc = bind (sockfd, addrs->ai_addr, addrs->ai_addrlen);
if (rc < 0)
{
perror ("bind");
exit (EXIT_FAILURE);
}
freeaddrinfo (addrs);
rc = listen (sockfd, SOMAXCONN);
if (rc < 0)
{
perror ("listen");
exit (EXIT_FAILURE);
}
signal (SIGPIPE, SIG_IGN);
while (run)
{
struct sockaddr from;
socklen_t fromlen = sizeof (from);
char host[NI_MAXHOST];
int fd;
FILE *fh;
fd = accept (sockfd, &from, &fromlen);
if (fd < 0)
{
perror ("accept");
continue;
}
rc = getnameinfo (&from, fromlen, host, sizeof (host),
NULL, 0, NI_NUMERICHOST);
if (rc == 0)
printf ("connection from %s\n", host);
else
printf ("getnameinfo: %s\n", gai_strerror (rc));
fh = fdopen (fd, "w+");
if (!fh)
{
perror ("fdopen");
close (fd);
continue;
}
smtp (fh, ctx);
fclose (fh);
}
close (sockfd);
gsasl_done (ctx);
return 0;
}
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 and GS2-KRB5 mechanism uses a GSS-API implementation, such as GNU GSS by Simon Josefsson.
Gnulib is used to simplify portability.
This manual borrows text from the SASL specification.
GNU SASL (gsasl) – Command line interface to libgsasl.
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.
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.
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.
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).
These options modify the behaviour of the callbacks (see Callback Functions) in the library. The default is to 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=<qop-auth | qop-int | qop-conf>
How application payload will be protected.
"qop-auth" means no protection,
"qop-int" means integrity protection,
"qop-conf" means confidentiality.
Currently only used by DIGEST-MD5, where the
default is "qop-int".
-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 Force use of STARTTLS. The default is to use
STARTTLS when available. (default=off)
--no-starttls Unconditionally disable STARTTLS.
(default=off)
--no-cb Don't set any channel bindings. (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.
--priority Cipher priority string.
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
This appendix contains clarifications to various SASL specification that we felt were necessary to include, if for nothing else it may serve as a guide for other implementers that worry about the same issues.
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 applies SASLprep to the password with the AllowUnassigned bit cleared.
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.
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.
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
outparameter.Return value: Returns
GSASL_OKif successful, or error code.Deprecated: Use
gsasl_client_mechlist()instead.
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
outparameter.Return value: Returns
GSASL_OKif successful, or error code.Deprecated: Use
gsasl_server_mechlist()instead.
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_OKif authenticated terminated successfully,GSASL_NEEDS_MOREif more data is needed, or error code.Deprecated: Use
gsasl_step()instead.
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_OKif authenticated terminated successfully,GSASL_NEEDS_MOREif more data is needed, or error code.Deprecated: Use
gsasl_step()instead.
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.
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.
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.
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.
sctx: libgsasl client handle
Get the libgsasl handle given a 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.
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()orgsasl_session_hook_set()instead.
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()orgsasl_session_hook_get()instead.
sctx: libgsasl server handle
Get the libgsasl handle given a 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.
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()orgsasl_session_hook_set()instead.
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()orgsasl_session_hook_get()instead.
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_OKiff successful.Deprecated: Use
gsasl_random()orgsasl_nonce()instead.
sctx: libgsasl session handle
Get the libgsasl handle given a 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.
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_OKif encoding was successful, otherwise an error code.Deprecated: Use
gsasl_encode()instead.Since: 0.2.0
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_OKif encoding was successful, otherwise an error code.Deprecated: Use
gsasl_decode()instead.Since: 0.2.0
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.
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.
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.
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.
ctx: libgsasl handle.
mechlist: input character array with SASL mechanism names, separated by invalid characters (e.g. SPC).
Get name of "best" SASL mechanism supported by the libgsasl server which is present in the input string.
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.
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 usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
ctx: libgsasl handle.
Get the callback earlier set by calling
gsasl_client_callback_authentication_id_set().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 usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
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 usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
ctx: libgsasl handle.
Get the callback earlier set by calling
gsasl_client_callback_authorization_id_set().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 usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
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 usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
ctx: libgsasl handle.
Get the callback earlier set by calling
gsasl_client_callback_password_set().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 usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
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 usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
ctx: libgsasl handle.
Get the callback earlier set by calling
gsasl_client_callback_passcode_set().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 usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
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 usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
ctx: libgsasl handle.
Get the callback earlier set by calling
gsasl_client_callback_pin_set().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 usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
ctx: libgsasl handle.
cb: callback function
Specify the callback function to use in the client to set the name of the service. The service buffer should be a registered GSSAPI host-based service name, hostname the name of the server. Servicename is used by DIGEST-MD5 and should be the name of generic server in case of a replicated service. The function can be later retrieved using
gsasl_client_callback_service_get().Deprecated: This function is part of the old callback interface. The new interface uses
gsasl_callback_set()to set the application callback, and usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
ctx: libgsasl handle.
Get the callback earlier set by calling
gsasl_client_callback_service_set().Return value: Returns the callback earlier set by calling
gsasl_client_callback_service_set().Deprecated: This function is part of the old callback interface. The new interface uses
gsasl_callback_set()to set the application callback, and usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
ctx: libgsasl handle.
cb: callback function
Specify the callback function to use in the client to set the anonymous token, which usually is the users email address. The function can be later retrieved using
gsasl_client_callback_anonymous_get().Deprecated: This function is part of the old callback interface. The new interface uses
gsasl_callback_set()to set the application callback, and usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
ctx: libgsasl handle.
Get the callback earlier set by calling
gsasl_client_callback_anonymous_set().Return value: Returns the callback earlier set by calling
gsasl_client_callback_anonymous_set().Deprecated: This function is part of the old callback interface. The new interface uses
gsasl_callback_set()to set the application callback, and usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
ctx: libgsasl handle.
cb: callback function
Specify the callback function to use in the client to determine the qop to use after looking at what the server offered. The function can be later retrieved using
gsasl_client_callback_qop_get().Deprecated: This function is part of the old callback interface. The new interface uses
gsasl_callback_set()to set the application callback, and usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
ctx: libgsasl handle.
Get the callback earlier set by calling
gsasl_client_callback_qop_set().Return value: Returns the callback earlier set by calling
gsasl_client_callback_qop_set().Deprecated: This function is part of the old callback interface. The new interface uses
gsasl_callback_set()to set the application callback, and usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
ctx: libgsasl handle.
cb: callback function
Specify the callback function to use in the client to inform the server of the largest buffer the client is able to receive when using the DIGEST-MD5 "auth-int" or "auth-conf" Quality of Protection (qop). If this directive is missing, the default value 65536 will be assumed. The function can be later retrieved using
gsasl_client_callback_maxbuf_get().Deprecated: This function is part of the old callback interface. The new interface uses
gsasl_callback_set()to set the application callback, and usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
ctx: libgsasl handle.
Get the callback earlier set by calling
gsasl_client_callback_maxbuf_set().Return value: Returns the callback earlier set by calling
gsasl_client_callback_maxbuf_set().Deprecated: This function is part of the old callback interface. The new interface uses
gsasl_callback_set()to set the application callback, and usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
ctx: libgsasl handle.
cb: callback function
Specify the callback function to use in the client to know which realm it belongs to. The realm is used by the server to determine which username and password to use. The function can be later retrieved using
gsasl_client_callback_realm_get().Deprecated: This function is part of the old callback interface. The new interface uses
gsasl_callback_set()to set the application callback, and usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
ctx: libgsasl handle.
Get the callback earlier set by calling
gsasl_client_callback_realm_set().Return value: Returns the callback earlier set by calling
gsasl_client_callback_realm_set().Deprecated: This function is part of the old callback interface. The new interface uses
gsasl_callback_set()to set the application callback, and usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
ctx: libgsasl handle.
cb: callback function
Specify the callback function to use in the server for deciding if user is authenticated using authentication identity, authorization identity and password. The function can be later retrieved using
gsasl_server_callback_validate_get().Deprecated: This function is part of the old callback interface. The new interface uses
gsasl_callback_set()to set the application callback, and usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
ctx: libgsasl handle.
Get the callback earlier set by calling
gsasl_server_callback_validate_set().Return value: Returns the callback earlier set by calling
gsasl_server_callback_validate_set().Deprecated: This function is part of the old callback interface. The new interface uses
gsasl_callback_set()to set the application callback, and usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
ctx: libgsasl handle.
cb: callback function
Specify the callback function to use in the server for deciding if user is authenticated using authentication identity, authorization identity and password. The function can be later retrieved using
gsasl_server_callback_retrieve_get().Deprecated: This function is part of the old callback interface. The new interface uses
gsasl_callback_set()to set the application callback, and usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
ctx: libgsasl handle.
Get the callback earlier set by calling
gsasl_server_callback_retrieve_set().Return value: Returns the callback earlier set by calling
gsasl_server_callback_retrieve_set().Deprecated: This function is part of the old callback interface. The new interface uses
gsasl_callback_set()to set the application callback, and usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
ctx: libgsasl handle.
cb: callback function
Specify the callback function to use in the server for deciding if user is authenticated using CRAM-MD5 challenge and response. The function can be later retrieved using
gsasl_server_callback_cram_md5_get().Deprecated: This function is part of the old callback interface. The new interface uses
gsasl_callback_set()to set the application callback, and usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
ctx: libgsasl handle.
Get the callback earlier set by calling
gsasl_server_callback_cram_md5_set().Return value: Returns the callback earlier set by calling
gsasl_server_callback_cram_md5_set().Deprecated: This function is part of the old callback interface. The new interface uses
gsasl_callback_set()to set the application callback, and usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
ctx: libgsasl handle.
cb: callback function
Specify the callback function to use in the server for retrieving the secret hash of the username, realm and password for use in the DIGEST-MD5 mechanism. The function can be later retrieved using
gsasl_server_callback_digest_md5_get().Deprecated: This function is part of the old callback interface. The new interface uses
gsasl_callback_set()to set the application callback, and usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
ctx: libgsasl handle.
Get the callback earlier set by calling
gsasl_server_callback_digest_md5_set().Return value: Return the callback earlier set by calling
gsasl_server_callback_digest_md5_set().Deprecated: This function is part of the old callback interface. The new interface uses
gsasl_callback_set()to set the application callback, and usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
ctx: libgsasl handle.
cb: callback function
Specify the callback function to use in the server for deciding if user is authenticated out of band. The function can be later retrieved using
gsasl_server_callback_external_get().Deprecated: This function is part of the old callback interface. The new interface uses
gsasl_callback_set()to set the application callback, and usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
ctx: libgsasl handle.
Get the callback earlier set by calling
gsasl_server_callback_external_set().Return value: Returns the callback earlier set by calling
gsasl_server_callback_external_set().Deprecated: This function is part of the old callback interface. The new interface uses
gsasl_callback_set()to set the application callback, and usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
ctx: libgsasl handle.
cb: callback function
Specify the callback function to use in the server for deciding if user is permitted anonymous access. The function can be later retrieved using
gsasl_server_callback_anonymous_get().Deprecated: This function is part of the old callback interface. The new interface uses
gsasl_callback_set()to set the application callback, and usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
ctx: libgsasl handle.
Get the callback earlier set by calling
gsasl_server_callback_anonymous_set().Return value: Returns the callback earlier set by calling
gsasl_server_callback_anonymous_set().Deprecated: This function is part of the old callback interface. The new interface uses
gsasl_callback_set()to set the application callback, and usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
ctx: libgsasl handle.
cb: callback function
Specify the callback function to use in the server to know which realm it serves. The realm is used by the user to determine which username and password to use. The function can be later retrieved using
gsasl_server_callback_realm_get().Deprecated: This function is part of the old callback interface. The new interface uses
gsasl_callback_set()to set the application callback, and usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
ctx: libgsasl handle.
Get the callback earlier set by calling
gsasl_server_callback_realm_set().Return value: Returns the callback earlier set by calling
gsasl_server_callback_realm_set().Deprecated: This function is part of the old callback interface. The new interface uses
gsasl_callback_set()to set the application callback, and usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
ctx: libgsasl handle.
cb: callback function
Specify the callback function to use in the server to know which quality of protection it accepts. The quality of protection eventually used is selected by the client though. It is currently used by the DIGEST-MD5 mechanism. The function can be later retrieved using
gsasl_server_callback_qop_get().Deprecated: This function is part of the old callback interface. The new interface uses
gsasl_callback_set()to set the application callback, and usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
ctx: libgsasl handle.
Get the callback earlier set by calling
gsasl_server_callback_qop_set().Return value: Returns the callback earlier set by calling
gsasl_server_callback_qop_set().Deprecated: This function is part of the old callback interface. The new interface uses
gsasl_callback_set()to set the application callback, and usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
ctx: libgsasl handle.
cb: callback function
Specify the callback function to use in the server to inform the client of the largest buffer the server is able to receive when using the DIGEST-MD5 "auth-int" or "auth-conf" Quality of Protection (qop). If this directive is missing, the default value 65536 will be assumed. The function can be later retrieved using
gsasl_server_callback_maxbuf_get().Deprecated: This function is part of the old callback interface. The new interface uses
gsasl_callback_set()to set the application callback, and usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
ctx: libgsasl handle.
Get the callback earlier set by calling
gsasl_server_callback_maxbuf_set().Return value: Returns the callback earlier set by calling
gsasl_server_callback_maxbuf_set().Deprecated: This function is part of the old callback interface. The new interface uses
gsasl_callback_set()to set the application callback, and usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
ctx: libgsasl handle.
cb: callback function
Specify the callback function to use in the server to inform the client of the cipher suites supported. The DES and 3DES ciphers must be supported for interoperability. It is currently used by the DIGEST-MD5 mechanism. The function can be later retrieved using
gsasl_server_callback_cipher_get().Deprecated: This function is part of the old callback interface. The new interface uses
gsasl_callback_set()to set the application callback, and usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
ctx: libgsasl handle.
Get the callback earlier set by calling
gsasl_server_callback_cipher_set().Return value: Returns the callback earlier set by calling
gsasl_server_callback_cipher_set().Deprecated: This function is part of the old callback interface. The new interface uses
gsasl_callback_set()to set the application callback, and usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
ctx: libgsasl handle.
cb: callback function
Specify the callback function to use in the server for validating a user via the SECURID mechanism. The function should return GSASL_OK if user authenticated successfully, GSASL_SECURID_SERVER_NEED_ADDITIONAL_PASSCODE if it wants another passcode, GSASL_SECURID_SERVER_NEED_NEW_PIN if it wants a PIN change, or an error. When (and only when) GSASL_SECURID_SERVER_NEED_NEW_PIN is returned, suggestpin can be populated with a PIN code the server suggests, and suggestpinlen set to the length of the PIN. The function can be later retrieved using
gsasl_server_callback_securid_get().Deprecated: This function is part of the old callback interface. The new interface uses
gsasl_callback_set()to set the application callback, and usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
ctx: libgsasl handle.
Get the callback earlier set by calling
gsasl_server_callback_securid_set().Return value: Returns the callback earlier set by calling
gsasl_server_callback_securid_set().Deprecated: This function is part of the old callback interface. The new interface uses
gsasl_callback_set()to set the application callback, and usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
ctx: libgsasl handle.
cb: callback function
Specify the callback function to use in the server for checking if a GSSAPI user is authorized for username (by, e.g., calling krb5_kuserok). The function should return GSASL_OK if the user should be permitted access, or an error code such as GSASL_AUTHENTICATION_ERROR on failure. The function can be later retrieved using
gsasl_server_callback_gssapi_get().Deprecated: This function is part of the old callback interface. The new interface uses
gsasl_callback_set()to set the application callback, and usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
ctx: libgsasl handle.
Get the callback earlier set by calling
gsasl_server_callback_gssapi_set().Return value: Returns the callback earlier set by calling
gsasl_server_callback_gssapi_set().Deprecated: This function is part of the old callback interface. The new interface uses
gsasl_callback_set()to set the application callback, and usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
ctx: libgsasl handle.
cb: callback function
Specify the callback function to use in the server to set the name of the service. The service buffer should be a registered GSSAPI host-based service name, hostname the name of the server. The function can be later retrieved using
gsasl_server_callback_service_get().Deprecated: This function is part of the old callback interface. The new interface uses
gsasl_callback_set()to set the application callback, and usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
ctx: libgsasl handle.
Get the callback earlier set by calling
gsasl_server_callback_service_set().Return value: Returns the callback earlier set by calling
gsasl_server_callback_service_set().Deprecated: This function is part of the old callback interface. The new interface uses
gsasl_callback_set()to set the application callback, and usesgsasl_callback()orgsasl_property_get()to invoke the callback for certain properties.
in: a UTF-8 encoded string.
len: length of
str, in bytes, or -1 ifstris nul-terminated.Converts a string into canonical form, standardizing such issues as whether a character with an accent is represented as a base character and combining accent or as a single precomposed character.
The normalization mode is NFKC (ALL COMPOSE). It standardizes differences that do not affect the text content, such as the above-mentioned accent representation. It standardizes the "compatibility" characters in Unicode, such as SUPERSCRIPT THREE to the standard forms (in this case DIGIT THREE). Formatting information may be lost but for most text operations such characters should be considered the same. It returns a result with composed forms rather than a maximally decomposed form.
Return value: Return a newly allocated string, that is the NFKC normalized form of
str, or NULL on error.Deprecated: No replacement functionality in GNU SASL, use GNU Libidn instead. Note that in SASL, you most likely want to use SASLprep and not bare NFKC, see
gsasl_saslprep().
in: input ASCII or UTF-8 string with data to prepare according to SASLprep.
stringprep_rc: pointer to output variable with stringprep error code, or NULL to indicate that you don't care about it.
Process a Unicode string for comparison, according to the "SASLprep" stringprep profile. This function is intended to be used by Simple Authentication and Security Layer (SASL) mechanisms (such as PLAIN, CRAM-MD5, and DIGEST-MD5) as well as other protocols exchanging user names and/or passwords.
Return value: Return a newly allocated string that is the "SASLprep" processed form of the input string, or NULL on error, in which case
stringprep_rccontain the stringprep library error code.Deprecated: Use
gsasl_saslprep()instead.
in: input ASCII or UTF-8 string with data to prepare according to "trace".
stringprep_rc: pointer to output variable with stringprep error code, or NULL to indicate that you don't care about it.
Process a Unicode string for use as trace information, according to the "trace" stringprep profile. The profile is designed for use with the SASL ANONYMOUS Mechanism.
Return value: Return a newly allocated string that is the "trace" processed form of the input string, or NULL on error, in which case
stringprep_rccontain the stringprep library error code.Deprecated: No replacement functionality in GNU SASL, use GNU Libidn instead.
filename: filename of file containing passwords.
username: username string.
key: output character array.
keylen: input maximum size of output character array, on output contains actual length of output array.
Retrieve password for user from specified file. To find out how large the output array must be, call this function with out=NULL.
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.
Deprecated: Use
gsasl_simple_getpass()instead.
src: input byte array
srclength: size of input byte array
target: output byte array
targsize: size of output byte array
Encode data as base64. Converts characters, three at a time, starting at src into four base64 characters in the target area until the entire input buffer is encoded.
Return value: Returns the number of data bytes stored at the target, or -1 on error.
Deprecated: Use
gsasl_base64_to()instead.
src: input byte array
target: output byte array
targsize: size of output byte array
Decode Base64 data. Skips all whitespace anywhere. Converts characters, four at a time, starting at (or after) src from Base64 numbers into three 8 bit bytes in the target area.
Return value: Returns the number of data bytes stored at the target, or -1 on error.
Deprecated: Use
gsasl_base64_from()instead.
ctx: libgsasl handle.
out: output array with client token.
outlen: on input the maximum size of the output array, on output contains the actual size of the output array.
Type of callback function the application implements. It should populate the output array with some input from the user and set the output array length, and return
GSASL_OK, or fail with an error code.If OUT is NULL, the function should only populate the output length field with the length, and return GSASL_OK. This usage may be used by the caller to allocate the proper buffer size.
ctx: libgsasl handle.
ctx: output array with client token.
ctx: on input the maximum size of the output array, on output contains the actual size of the output array. If OUT is
Type of callback function the application implements. It should return
GSASL_OKif user should be permitted anonymous access, otherwiseGSASL_AUTHENTICATION_ERROR.
ctx: libgsasl handle.
out: output array with authentication identity.
outlen: on input the maximum size of the output array, on output contains the actual size of the output array.
Type of callback function the application implements. It should populate the output array with authentiction identity of user and set the output array length, and return
GSASL_OK, or fail with an error code. The authentication identity must be encoded in UTF-8, but need not be normalized in any way.If OUT is NULL, the function should only populate the output length field with the length, and return GSASL_OK. This usage may be used by the caller to allocate the proper buffer size.
ctx: libgsasl handle.
out: output array with authorization identity.
outlen: on input the maximum size of the output array, on output contains the actual size of the output array.
Type of callback function the application implements. It should populate the output array with authorization identity of user and set the output array length, and return
GSASL_OK, or fail with an error code. The authorization identity must be encoded in UTF-8, but need not be normalized in any way.If OUT is NULL, the function should only populate the output length field with the length, and return GSASL_OK. This usage may be used by the caller to allocate the proper buffer size.
ctx: libgsasl handle.
service: output array with name of service.
servicelen: on input the maximum size of the service output array, on output contains the actual size of the service output array.
hostname: output array with hostname of server.
hostnamelen: on input the maximum size of the hostname output array, on output contains the actual size of the hostname output array.
servicename: output array with generic name of server in case of replication (DIGEST-MD5 only).
servicenamelen: on input the maximum size of the servicename output array, on output contains the actual size of the servicename output array.
Type of callback function the application implements. It should retrieve the service (which should be a registered GSSAPI host based service name, such as “imap”) on the server, hostname of server (usually canoncial DNS hostname) and optionally generic service name of server in case of replication (e.g. “mail.example.org” when the hostname is “mx42.example.org”, see the RFC 2831 for more information). It should return GSASL_OK, or an error such as GSASL_AUTHENTICATION_ERROR if it fails.
If SERVICE, HOSTNAME or SERVICENAME is NULL, the function should only populate SERVICELEN, HOSTNAMELEN or SERVICENAMELEN with the output length of the respective field, and return GSASL_OK. This usage may be used by the caller to allocate the proper buffer size. Furthermore, SERVICENAMELEN may also be NULL, indicating that the mechanism is not interested in this field.
ctx: libgsasl handle.
username: input array with username.
challenge: input array with CRAM-MD5 challenge.
response: input array with CRAM-MD5 response.
Type of callback function the application implements. It should return GSASL_OK if and only if the validation of the provided credential was succesful. GSASL_AUTHENTICATION_ERROR is a good failure if authentication failed, but any available return code may be used.
ctx: libgsasl handle.
username: input array with authentication identity of user.
realm: input array with realm of user.
secrethash: output array that should contain hash of username, realm and password as described for the DIGEST-MD5 mechanism.
Type of callback function the application implements. It should retrieve the secret hash for the given user in given realm and return GSASL_OK, or an error such as GSASL_AUTHENTICATION_ERROR if it fails. The secrethash buffer is guaranteed to have size for the fixed length MD5 hash.
ctx: libgsasl handle.
Type of callback function the application implements. It should return
GSASL_OKif user is authenticated by out of band means, otherwiseGSASL_AUTHENTICATION_ERROR.
ctx: libgsasl handle.
clientname: input array with GSSAPI client name.
authentication_id: input array with authentication identity.
Type of callback function the application implements. It should return GSASL_OK if and only if the GSSAPI user is authorized to log on as the given authentication_id. GSASL_AUTHENTICATION_ERROR is a good failure if authentication failed, but any available return code may be used. This callback is usually implemented in the application as a call to krb5_kuserok(), such as:
int callback_gssapi (Gsasl_session_ctx *ctx, char *clientname, char *authentication_id) { int rc = GSASL_AUTHENTICATION_ERROR; krb5_principal p; krb5_context kcontext; krb5_init_context (&kcontext); if (krb5_parse_name (kcontext, clientname, &p) != 0) return -1; if (krb5_kuserok (kcontext, p, authentication_id)) rc = GSASL_OK; krb5_free_principal (kcontext, p); return rc; }
ctx: libgsasl handle.
out: output array with passcode.
outlen: on input the maximum size of the output array, on output contains the actual size of the output array.
Type of callback function the application implements. It should populate the output array with passcode of user and set the output array length, and return
GSASL_OK, or fail with an error code.If OUT is NULL, the function should only populate the output length field with the length, and return GSASL_OK. This usage may be used by the caller to allocate the proper buffer size.
ctx: libgsasl handle.
out: output array with password.
outlen: on input the maximum size of the output array, on output contains the actual size of the output array.
Type of callback function the application implements. It should populate the output array with password of user and set the output array length, and return
GSASL_OK, or fail with an error code. The password must be encoded in UTF-8, but need not be normalized in any way.If OUT is NULL, the function should only populate the output length field with the length, and return GSASL_OK. This usage may be used by the caller to allocate the proper buffer size.
ctx: libgsasl handle.
authentication_id: input array with authentication identity.
authorization_id: input array with authorization identity, or NULL.
realm: input array with realm of user, or NULL.
key: output array with key for authentication identity.
keylen: on input the maximum size of the key output array, on output contains the actual size of the key output array.
Type of callback function the application implements. It should retrieve the password for the indicated user and return GSASL_OK, or an error code such as GSASL_AUTHENTICATION_ERROR. The key must be encoded in UTF-8, but need not be normalized in any way.
If KEY is NULL, the function should only populate the KEYLEN output length field with the length, and return GSASL_OK. This usage may be used by the caller to allocate the proper buffer size.
ctx: libgsasl handle.
authorization_id: input array with authorization identity.
authentication_id: input array with authentication identity.
passcode: input array with passcode.
pin: input array with new pin (this may be NULL).
suggestpin: output array with new suggested PIN.
suggestpinlen: on input the maximum size of the output array, on output contains the actual size of the output array.
Type of callback function the application implements. It should return GSASL_OK if and only if the validation of the provided credential was succesful. GSASL_AUTHENTICATION_ERROR is a good failure if authentication failed, but any available return code may be used.
Two SECURID specific error codes also exists. The function can return GSASL_SECURID_SERVER_NEED_ADDITIONAL_PASSCODE to request that the client generate a new passcode. It can also return GSASL_SECURID_SERVER_NEED_NEW_PIN to request that the client generate a new PIN. If the server wishes to suggest a new PIN it can populate the SUGGESTPIN field.
If SUGGESTPIN is NULL, the function should only populate the output length field with the length, and return GSASL_OK. This usage may be used by the caller to allocate the proper buffer size.
ctx: libgsasl handle.
service: output array with name of service.
servicelen: on input the maximum size of the service output array, on output contains the actual size of the service output array.
hostname: output array with hostname of server.
hostnamelen: on input the maximum size of the hostname output array, on output contains the actual size of the hostname output array.
Type of callback function the application implements. It should retrieve the service (which should be a registered GSSAPI host based service name, such as “imap”) the server provides and hostname of server (usually canoncial DNS hostname). It should return GSASL_OK, or an error such as GSASL_AUTHENTICATION_ERROR if it fails.
If SERVICE or HOSTNAME is NULL, the function should only populate SERVICELEN or HOSTNAMELEN with the output length of the respective field, and return GSASL_OK. This usage may be used by the caller to allocate the proper buffer size.
ctx: libgsasl handle.
authorization_id: input array with authorization identity.
authentication_id: input array with authentication identity.
password: input array with password.
Type of callback function the application implements. It should return GSASL_OK if and only if the validation of the provided credential was succesful. GSASL_AUTHENTICATION_ERROR is a good failure if authentication failed, but any available return code may be used.
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(: Old Functionsgsasl: Invoking gsaslgsasl_appinfo_get: Old Functionsgsasl_appinfo_set: Old Functionsgsasl_application_data_get: Old Functionsgsasl_application_data_set: Old Functionsgsasl_base64_decode: Old Functionsgsasl_base64_encode: Old Functionsgsasl_base64_from: Utilitiesgsasl_base64_to: Utilitiesgsasl_callback: Callback Functionsgsasl_callback_hook_get: Callback Functionsgsasl_callback_hook_set: Callback Functionsgsasl_callback_set: Callback Functionsgsasl_check_version: Version Checkgsasl_client_application_data_get: Old Functionsgsasl_client_application_data_set: Old Functionsgsasl_client_callback_anonymous_get: Old Functionsgsasl_client_callback_anonymous_set: Old Functionsgsasl_client_callback_authentication_id_get: Old Functionsgsasl_client_callback_authentication_id_set: Old Functionsgsasl_client_callback_authorization_id_get: Old Functionsgsasl_client_callback_authorization_id_set: Old Functionsgsasl_client_callback_maxbuf_get: Old Functionsgsasl_client_callback_maxbuf_set: Old Functionsgsasl_client_callback_passcode_get: Old Functionsgsasl_client_callback_passcode_set: Old Functionsgsasl_client_callback_password_get: Old Functionsgsasl_client_callback_password_set: Old Functionsgsasl_client_callback_pin_get: Old Functionsgsasl_client_callback_pin_set: Old Functionsgsasl_client_callback_qop_get: Old Functionsgsasl_client_callback_qop_set: Old Functionsgsasl_client_callback_realm_get: Old Functionsgsasl_client_callback_realm_set: Old Functionsgsasl_client_callback_service_get: Old Functionsgsasl_client_callback_service_set: Old Functionsgsasl_client_ctx_get: Old Functionsgsasl_client_finish: Old Functionsgsasl_client_listmech: Old Functionsgsasl_client_mechlist: Global Functionsgsasl_client_start: Session Functionsgsasl_client_step: Old Functionsgsasl_client_step_base64: Old Functionsgsasl_client_suggest_mechanism: Global Functionsgsasl_client_support_p: Global Functionsgsasl_ctx_get: Old Functionsgsasl_decode: Session Functionsgsasl_decode_inline: Old Functionsgsasl_done: Global Functionsgsasl_encode: Session Functionsgsasl_encode_inline: Old Functionsgsasl_finish: Session Functionsgsasl_free: Memory Handlinggsasl_hmac_md5: Utilitiesgsasl_hmac_sha1: Utilitiesgsasl_init: Global Functionsgsasl_md5: Utilitiesgsasl_md5pwd_get_password: Old Functionsgsasl_mechanism_name: Session Functionsgsasl_nonce: Utilitiesgsasl_property_fast: Property Functionsgsasl_property_get: Property Functionsgsasl_property_set: Property Functionsgsasl_property_set_raw: Property Functionsgsasl_random: Utilitiesgsasl_randomize: Old Functionsgsasl_register: Global Functionsgsasl_saslprep: Utilitiesgsasl_server_application_data_get: Old Functionsgsasl_server_application_data_set: Old Functionsgsasl_server_callback_anonymous_get: Old Functionsgsasl_server_callback_anonymous_set: Old Functionsgsasl_server_callback_cipher_get: Old Functionsgsasl_server_callback_cipher_set: Old Functionsgsasl_server_callback_cram_md5_get: Old Functionsgsasl_server_callback_cram_md5_set: Old Functionsgsasl_server_callback_digest_md5_get: Old Functionsgsasl_server_callback_digest_md5_set: Old Functionsgsasl_server_callback_external_get: Old Functionsgsasl_server_callback_external_set: Old Functionsgsasl_server_callback_gssapi_get: Old Functionsgsasl_server_callback_gssapi_set: Old Functionsgsasl_server_callback_maxbuf_get: Old Functionsgsasl_server_callback_maxbuf_set: Old Functionsgsasl_server_callback_qop_get: Old Functionsgsasl_server_callback_qop_set: Old Functionsgsasl_server_callback_realm_get: Old Functionsgsasl_server_callback_realm_set: Old Functionsgsasl_server_callback_retrieve_get: Old Functionsgsasl_server_callback_retrieve_set: Old Functionsgsasl_server_callback_securid_get: Old Functionsgsasl_server_callback_securid_set: Old Functionsgsasl_server_callback_service_get: Old Functionsgsasl_server_callback_service_set: Old Functionsgsasl_server_callback_validate_get: Old Functionsgsasl_server_callback_validate_set: Old Functionsgsasl_server_ctx_get: Old Functionsgsasl_server_finish: Old Functionsgsasl_server_listmech: Old Functionsgsasl_server_mechlist: Global Functionsgsasl_server_start: Session Functionsgsasl_server_step: Old Functionsgsasl_server_step_base64: Old Functionsgsasl_server_suggest_mechanism: Old Functionsgsasl_server_support_p: Global Functionsgsasl_session_hook_get: Callback Functionsgsasl_session_hook_set: Callback Functionsgsasl_sha1: Utilitiesgsasl_simple_getpass: Utilitiesgsasl_step: Session Functionsgsasl_step64: Session Functionsgsasl_strerror: Error stringsgsasl_strerror_name: Error stringsgsasl_stringprep_nfkc: Old Functionsgsasl_stringprep_saslprep: Old Functionsgsasl_stringprep_trace: Old Functions[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.