Copyright © 2002, 2003 Simon Josefsson.
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.1 or any later version published by the Free Software Foundation; with the Invariant Sections being "Commercial Support", the Front-Cover texts being “A GNU Manual”, and with the Back-Cover Texts being “You have freedom to copy and modify this GNU Manual, like GNU software”. A copy of the license is included in the section entitled "GNU Free Documentation License".
GNU SASL is an implementation of the Simple Authentication and Security Layer framework and a few common SASL mechanisms. SASL is used by network servers (e.g., IMAP, SMTP) to request authentication from clients, and in clients to authenticate against servers.
GNU SASL contains of a library (`libgsasl'), a command line utility (`gsasl') to access the library from the shell, and a manual. The library includes support for the framework (with authentication functions and application data privacy and integrity functions) and at least partial support for the CRAM-MD5, EXTERNAL, GSSAPI, ANONYMOUS, PLAIN, SECURID, DIGEST-MD5, LOGIN, NTLM mechanisms.
The library is easily ported because it does not do network communication by itself, but rather leaves it up to the calling application. The library is flexible with regards to the authorization infrastructure used, as it utilizes callbacks into the application to decide whether a user is authorized or not. GNU SASL has been ported to many Unix flavors.
This manual documents the `Libgsasl' library programming interface. All functions and data types provided by the library are explained.
The reader is assumed to possess basic familiarity with SASL and network programming in C or C++.
This manual can be used in several ways. If read from the beginning to the end, it gives a good introduction into the library and how it can be used in an application. Forward references are included where necessary. Later on, the manual can be used as a reference manual to get just the information needed about any particular interface of the library. Experienced programmers might want to start looking at the examples at the end of the manual, and then only read up those parts of the interface which are unclear.
`Libgsasl' might have a couple of advantages over other libraries doing a similar job.
Note that the library do not implement any policy to decide whether a certain user is “authenticated” or “authorized” or not. Rather, it uses callbacks back into the application to answer these questions.
This section describes SASL from a protocol point of view.
The Simple Authentication and Security Layer (SASL) is a method for adding authentication support to connection-based protocols. A protocol includes a command for identifying and authenticating a user to a server and for optionally negotiating a security layer for subsequent protocol interactions.
The command has a required argument identifying a SASL mechanism. SASL mechanisms are named by strings, from 1 to 20 characters in length, consisting of upper-case letters, digits, hyphens, and/or underscores.
If a server supports the requested mechanism, it initiates an authentication protocol exchange. This consists of a series of server challenges and client responses that are specific to the requested mechanism. The challenges and responses are defined by the mechanisms as binary tokens of arbitrary length. The protocol's profile then specifies how these binary tokens are then encoded for transfer over the connection.
After receiving the authentication command or any client response, a server may issue a challenge, indicate failure, or indicate completion. The protocol's profile specifies how the server indicates which of the above it is doing.
After receiving a challenge, a client may issue a response or abort the exchange. The protocol's profile specifies how the client indicates which of the above it is doing.
During the authentication protocol exchange, the mechanism performs authentication, transmits an authorization identity (frequently known as a userid) from the client to server, and negotiates the use of a mechanism-specific security layer. If the use of a security layer is agreed upon, then the mechanism must also define or negotiate the maximum cipher-text buffer size that each side is able to receive.
The transmitted authorization identity may be different than the identity in the client's authentication credentials. This permits agents such as proxy servers to authenticate using their own credentials, yet request the access privileges of the identity for which they are proxying. With any mechanism, transmitting an authorization identity of the empty string directs the server to derive an authorization identity from the client's authentication credentials.
If use of a security layer is negotiated, it is applied to all subsequent data sent over the connection. The security layer takes effect immediately following the last response of the authentication exchange for data sent by the client and the completion indication for data sent by the server. Once the security layer is in effect, the protocol stream is processed by the security layer into buffers of cipher-text. Each buffer is transferred over the connection as a stream of octets prepended with a four octet field in network byte order that represents the length of the following buffer. The length of the cipher-text buffer must be no larger than the maximum size that was defined or negotiated by the other side.
Libgsasl has at some point in time been tested on the following platforms.
GCC 2.95.4 and GNU Make. This is the main development platform.
alphaev67-unknown-linux-gnu, alphaev6-unknown-linux-gnu,
arm-unknown-linux-gnu, hppa-unknown-linux-gnu,
hppa64-unknown-linux-gnu, i686-pc-linux-gnu,
ia64-unknown-linux-gnu, m68k-unknown-linux-gnu,
mips-unknown-linux-gnu, mipsel-unknown-linux-gnu,
powerpc-unknown-linux-gnu, s390-ibm-linux-gnu,
sparc-unknown-linux-gnu.
GCC 2.95.1 and GNU Make. armv4l-unknown-linux-gnu.
Tru64 UNIX C compiler and Tru64 Make. alphaev67-dec-osf5.1,
alphaev68-dec-osf5.1.
GCC 2.96 and GNU Make. alphaev6-unknown-linux-gnu,
alphaev67-unknown-linux-gnu.
GCC 3.0 and GNU Make. ia64-unknown-linux-gnu.
GCC 2.96 and GNU Make. alphaev6-unknown-linux-gnu,
alphaev67-unknown-linux-gnu, ia64-unknown-linux-gnu.
GCC 3.2 and GNU Make. i686-pc-linux-gnu.
GCC 2.96 and GNU Make. i686-pc-linux-gnu.
GCC 2.95.3 and GNU Make. i686-pc-linux-gnu.
GCC 3.2 and GNU Make. i686-pc-linux-gnu.
MIPS C compiler, IRIX Make. mips-sgi-irix6.5.
IBM C for AIX compiler, AIX Make. rs6000-ibm-aix4.3.2.0.
GCC 3.2, GNU make. i686-pc-cygwin.
HP-UX C compiler and HP Make. ia64-hp-hpux11.22,
hppa2.0w-hp-hpux11.11.
Sun WorkShop Compiler C 6.0 and SUN Make. sparc-sun-solaris2.8.
Sun Forte Developer 7 C compiler and GNU
Make. sparc-sun-solaris2.9.
GCC 2.95.3 and GNU Make. alpha-unknown-netbsd1.6,
i386-unknown-netbsdelf1.6.
GCC 2.95.3 and GNU Make. alpha-unknown-openbsd3.1,
i386-unknown-openbsd3.1.
GCC 2.95.4 and GNU Make. alpha-unknown-freebsd4.7,
i386-unknown-freebsd4.7.
If you use Libgsasl on, or port Libgsasl to, a new platform please report it to the author.
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 Drottningholmsv. 70 112 42 Stockholm Sweden E-mail: simon@josefsson.org
If your company provide support related to GNU SASL and would like to be mentioned here, contact the author (see Bug Reports).
The package can be downloaded from several places, including:
<http://josefsson.org/gsasl/releases/>
The latest version is stored in a file, e.g.,
gsasl-0.0.42.tar.gz where the 0.0.42 indicate the
highest version number.
The package is then extracted, configured and built like many other
packages that use Autoconf. For detailed information on configuring
and building it, refer to the INSTALL file that is part of the
distribution archive.
Here is an example terminal session that download, configure, build
and install the package. You will need a few basic tools, such as
sh, make and cc.
$ wget -q http://josefsson.org/gsasl/releases/gsasl-0.0.8.tar.gz
$ tar xfz gsasl-0.0.8.tar.gz
$ cd gsasl-0.0.8/
$ ./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-anonymous
--disable-external
--disable-plain
--disable-login
--disable-securid
--disable-ntlm
--disable-cram-md5
--disable-digest-md5
--disable-gssapi
--disable-kerberos_v5
--without-stringprep
For the complete list, refer to the output from configure
--help.
If you think you have found a bug in Libgsasl, 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:
bug-gsasl@gnu.orgIf 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.
diff -u.
To use `Libgsasl', 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 `Libgsasl' 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 of `Libgsasl' 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.
`Libgsasl' 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.
In order to take advantage of the internationalisation features in
`Libgsasl', such as translated error messages, the application must
set the current locale using setlocale before initializing
`Libgsasl'.
In order to take advantage of the secure memory features in `Libgcrypt', which subsequently makes sensitive key material used in `Libgsasl' be allocated in secure memory, you need to initialize secure memory in your application, and for some platforms even make your application setuid root. See the libgcrypt documentation for more information. Example code to initialize secure memory in your code:
#include <gcrypt.h>
...
int
main (int argc, char *argv[])
{
...
/* 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);
...
If you do not do this, keying material will not be allocated in secure memory, which for most application is not the biggest secure problem. Note that `Libgsasl' has not been audited to make sure it only ever stores passwords or keys in secure memory.
It is often desirable to check that the version of `Libgsasl' used is indeed one which fits all requirements. Even with binary compatibility new features may have been introduced but due to problem with the dynamic linker an old version is actually used. So you may want to check that the version is okay right after program startup.
| const char * gsasl_check_version (const char * req_version) | Function |
|
req_version: version string to compare with, or NULL
Check library version. Return value: Check that the the version of the library is at
minimum the one given as a string in |
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, `Libgsasl' uses the
external package pkg-config that knows the path to the
include file and other configuration options. The options that need
to be added to the compiler invocation at compile time are output by
the --cflags option to pkg-config libgsasl. The
following example shows how it can be used at the command line:
gcc -c foo.c `pkg-config libgsasl --cflags`
Adding the output of pkg-config libgsasl --cflags to the
compilers command line will ensure that the compiler can find the
`gsasl.h' header file.
A similar problem occurs when linking the program with the library.
Again, the compiler has to find the library files. For this to work,
the path to the library files has to be added to the library search path
(via the -L option). For this, the option --libs to
pkg-config libgsasl can be used. For convenience, this option
also outputs all other options that are required to link the program
with the `libgsasl' libarary (for instance, the -lidn
option). The example shows how to link foo.o with the `libgsasl'
library to a program foo.
gcc -o foo foo.o `pkg-config libgsasl --libs`
Of course you can also combine both examples to a single command by
specifying both options to pkg-config:
gcc -o foo foo.c `pkg-config libgsasl --cflags --libs`
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 Libgsasl 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.
pkg-configIf your audience is a typical GNU/Linux desktop, you can often assume
they have the pkg-config tool installed, in which you can use
its Autoconf M4 macro to find and set up your package for use with
Libgsasl. The following illustrate this scenario.
AC_ARG_ENABLE(gsasl,
AC_HELP_STRING([--disable-gsasl], [don't use GNU SASL]),
gsasl=$enableval)
if test "$gsal" != "no" ; then
PKG_CHECK_MODULES(GSASL, libgsasl >= 0.0.8,
[gsasl=yes],
[gsasl=no])
if test "$gsasl" != "yes" ; then
sal=no
AC_MSG_WARN([Cannot find GNU SASL, disabling])
else
gsasl=yes
AC_DEFINE(USE_GSASL, 1, [Define to 1 if you want GNU SASL.])
fi
fi
AC_MSG_CHECKING([if GNU SASL should be used])
AC_MSG_RESULT($gsasl)
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 illustrate this scenario.
AC_CHECK_HEADER(gsasl.h,
AC_CHECK_LIB(gsasl, gsasl_check_version,
[gsasl=yes AC_SUBST(GSASL_LIBS, -lgsasl)],
gsasl=no),
gsasl=no)
AC_ARG_ENABLE(gsasl,
AC_HELP_STRING([--disable-gsasl], [don't use GNU SASL]),
gsasl=$enableval)
if test "$gsasl" != "no" ; then
AC_DEFINE(USE_SASL, 1, [Define to 1 if you want GNU SASL.])
else
AC_MSG_WARN([Cannot find GNU SASL, diabling])
fi
AC_MSG_CHECKING([if GNU SASL should be used])
AC_MSG_RESULT($gsasl)
After initialization of the library, the core part of the library is run within a loop until it has finished. The library is handed input from the other protocol entity and results in output which is to be sent to the other entity, or an error code. The library does not send data to the server itself, but only return it in buffers. The main interface to the library uses binary data, but since many common protocols uses Base 64 encoded data, a wrapper around the main function is also provided.
The following pseudo code illustrates how the library is used in a simple client. All the functions used are explained later on in this manual.
main()
{
Gsasl_ctx *ctx;
Gsasl_session_ctx *cctx;
char *input, output[BUFFERSIZE];
size_t output_len;
int rc;
rc = gsasl_init (&ctx);
if (rc != GSASL_OK)
die(gsasl_strerror(rc));
/* XXX Set callbacks here */
/* Read supported SASL mechanism from server */
input = read_from_client();
/* Select a good mechanism */
mech = gsasl_client_suggest_mechanism (ctx, input);
if (mech == NULL)
die("Cannot find any commonly agreed SASL mechanism...");
/* Start to use it */
res = gsasl_client_start (ctx, mech, &cctx);
if (res != GSASL_OK)
die(gsasl_strerror (rc));
input = NULL;
do
{
/* Do one SASL step and unless we're done, send the output to
server and read new data from server */
rc = gsasl_client_step_base64 (cctx, input, output, BUFFERSIZE);
if (rc != GSASL_NEEDS_MORE && rc != GSASL_OK)
break;
write_to_server(output);
if (rc == GSASL_OK)
break;
input = read_from_server();
}
while (rc == GSASL_NEEDS_MORE);
if (rc != GSASL_OK)
die("Authentication failed... %s\n", gsasl_strerror(rc);
/* Client is now authenticated -- proceed with actual protocol... */
gsasl_client_finish (cctx);
gsasl_done (ctx);
}
Notice the XXX comment that said you should specify the callbacks to
use there. `Libgsasl' depend on callbacks to implement user
interaction (in the client) and user validation (in the server). If
you don't specify any callbacks, very few mechanisms will be supported
(like EXTERNAL that don't need any additional information,
see EXTERNAL). Since we are building a simple client, we define
callbacks which are used by several SASL mechanisms to get username
and password. We start by defining the function for querying the
username, following the prototype for
Gsasl_client_callback_authentication_id for the LOGIN mechanism
(see LOGIN) .
int
callback_username (Gsasl_session_ctx *ctx,
char *out,
size_t *outlen)
{
char username[BUFFERSIZE];
if (out == NULL)
*outlen = BUFFERSIZE;
else
{
fprintf(stdout, "Enter username: ");
fgets(username, BUFFERSIZE, stdin);
*outlen = strlen(BUFFERSIZE);
}
return GSASL_OK;
}
As you can see, this is a simplistic function that reads a username
from the user. The callback for entering the password is similar and
follows the Gsasl_client_callback_password prototype:
int
callback_password (Gsasl_session_ctx *ctx,
char *out,
size_t *outlen)
{
char password[BUFFERSIZE];
if (out == NULL)
*outlen = BUFFERSIZE;
else
{
fprintf(stdout, "Enter password: ");
fgets(password, BUFFERSIZE, stdin);
*outlen = strlen(BUFFERSIZE);
}
return GSASL_OK;
}
In reality, the program should probably inhibit echo of the password to the terminal, but that is left as an exercise for the reader.
Now having implemented the callbacks, we are ready to replace the XXX comment with real code that set the callbacks (see Callback Functions). The following does it.
gsasl_client_callback_authentication_id_set(ctx, callback_username);
gsasl_client_callback_authorization_id_set(ctx, callback_username);
gsasl_client_callback_password_set(ctx, callback_password);
Notice that we use the same callback for the authentication identity and the authorization identity. In reality, this may be too simplistic, but will do for an example.
The simple client is now complete, and will be able to support SASL mechanisms such as PLAIN and CRAM-MD5.
Implementing a server is very similar to the client, the only
difference is that you use gsasl_server_* functions instead of
gsasl_client_* and instead of implementing
Gsasl_client_* callbacks implement some Gsasl_server_*
callbacks. See each mechanism (see Mechanisms) for details on
which callbacks are required and their prototype.
A note for server authors is in place, on the optional initial client
output (discussed in section 5.1 of RFC 2222). In a server looking
similar to the code above, the first call to
gsasl_server_step_base64 would have a input set to NULL.
The mechanisms interprete this as your protocol do not support initial
client output. If the protocol in which you implement SASL supports
initial client output, the first call to
gsasl_server_step_base64 should include a real buffer with the
initial client data.
One note for client authors is in place. The code above aborts processing if `Libgsasl' did not come out of the loop with a GSASL_OK exit code. It is a mistake to not require this, and instead only look at what the server is sending you. Even if the server said you are authenticated, it does not always mean that the SASL mechanism is satisfied. This is specifically true for SASL client mechanisms which perform server authentication. Thus, if you only trust what the server replied instead of requireing a GSASL_OK result, you may open up for fake servers. Don't shortcut the loop with a positive server response.
Different SASL mechanisms have different requirements on the
application using it. Some simpler mechanisms, such as LOGIN and
PLAIN, are straight forward to hook into existing authentication
systems (such as /etc/passwd via PAM). The client callback for
these mechanisms is easy to implement, the user is simply queried for
the username and password. The server callbacks pass on the username
and password into the policy deciding authentication system
(e.g. PAM).
Other mechanism like CRAM-MD5, DIGEST-MD5, and SRP uses hashed passwords. The client callback are the same as for PLAIN and LOGIN. However, the server do not receive the plaintext password via the network but rather a hash of it. Existing policy deciding systems like PAM cannot handle this, so the server callback for these mechanisms are more complicated.
Further mechanisms like GSSAPI (Kerberos 5) assume a specific authentication system. In theory this means that `Libgsasl' 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.
Special mechanisms like EXTERNAL and ANONYMOUS are entirely dependent on callbacks.
The EXTERNAL mechanism is used to authenticate a user to SASL when SASL is used in an environment which has already authenticated the user. It is often used within TLS or IPSEC protected channels.
This mechanism is only enabled in the server if you implement the callback below and set them in the library (see Callback Functions). It is always enabled in the client as there are no client callbacks.
| int (*Gsasl_server_callback_external) (Gsasl_session_ctx * ctx) | Prototype |
|
ctx: libgsasl handle. Type of callback function the application implements. It should
return |
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.
This mechanism is only enabled in the client and server if you implement the respectively callbacks below and set them in the library (see Callback Functions).
| int (*Gsasl_client_callback_anonymous) (Gsasl_session_ctx * ctx, char * out, size_t * outlen) | Prototype |
|
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 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. |
| int (*Gsasl_server_callback_anonymous) (Gsasl_session_ctx * ctx, const char * token) | Prototype |
|
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 |
The PLAIN mechanism uses username (authentication identity and authorization identity) and password to authenticate users. Two ways of validating the user is provided, either by having the SASL mechanism retrieve the raw password from the application and perform the validation internally, or by calling the application with authentication identity, authorization identity and password and let it decide. If both the validating and the retrieving callbacks are specified by the application, the validating one will be used.
This mechanism is only enabled in the client and server if you implement the respectively callbacks below and set them in the library (see Callback Functions).
| int (*Gsasl_client_callback_authorization_id) (Gsasl_session_ctx * ctx, char * out, size_t * outlen) | Prototype |
|
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 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. |
| int (*Gsasl_client_callback_authentication_id) (Gsasl_session_ctx * ctx, char * out, size_t * outlen) | Prototype |
|
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 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. |
| int (*Gsasl_client_callback_password) (Gsasl_session_ctx * ctx, char * out, size_t * outlen) | Prototype |
|
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 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. |
| int (*Gsasl_server_callback_validate) (Gsasl_session_ctx * ctx, char * authorization_id, char * authentication_id, char * password) | Prototype |
|
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. |
| int (*Gsasl_server_callback_retrieve) (Gsasl_session_ctx * ctx, char * authentication_id, char * authorization_id, char * realm, char * key, size_t * keylen) | Prototype |
|
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. |
The LOGIN mechanism uses username (authorization identity only) and password to authenticate users. Two ways of validating the user is provided, either by having the SASL mechanism retrieve the raw password from the application and perform the validation internally, or by calling the application with authorization identity and password and let it decide. If both the validating and the retrieving callbacks are specified by the application, the validating one will be used.
This mechanism is only enabled in the client and server if you implement the respectively callbacks below and set them in the library (see Callback Functions).
| int (*Gsasl_client_callback_authorization_id) (Gsasl_session_ctx * ctx, char * out, size_t * outlen) | Prototype |
|
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 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. |
| int (*Gsasl_client_callback_password) (Gsasl_session_ctx * ctx, char * out, size_t * outlen) | Prototype |
|
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 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. |
| int (*Gsasl_server_callback_validate) (Gsasl_session_ctx * ctx, char * authorization_id, char * authentication_id, char * password) | Prototype |
|
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. |
| int (*Gsasl_server_callback_retrieve) (Gsasl_session_ctx * ctx, char * authentication_id, char * authorization_id, char * realm, char * key, size_t * keylen) | Prototype |
|
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. |
The CRAM-MD5 mechanism uses username (authorization identity only) and password to authenticate users. Only a hashed password is transfered, which means that you cannot use normal policy deciding authentication systems such as PAM which do not support extraction of passwords. Two ways of validating the user is provided, either by having the SASL mechanism retrieve the raw password from the application and perform the validation internally, or by calling the application with the CRAM-MD5 challenge and response and let it decide. If both the validating and the retrieving callbacks are specified by the application, the validating one will be used.
While not documented in the original CRAM-MD5 specification, this implementation normalizes the username and the authorization identity using the Unicode 3.2 NFKC form according to the proposed update of CRAM-MD5.
This mechanism is only enabled in the client and server if you implement the respectively callbacks below and set them in the library (see Callback Functions).
| int (*Gsasl_client_callback_authorization_id) (Gsasl_session_ctx * ctx, char * out, size_t * outlen) | Prototype |
|
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 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. |
| int (*Gsasl_client_callback_password) (Gsasl_session_ctx * ctx, char * out, size_t * outlen) | Prototype |
|
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 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. |
| int (*Gsasl_server_callback_retrieve) (Gsasl_session_ctx * ctx, char * authentication_id, char * authorization_id, char * realm, char * key, size_t * keylen) | Prototype |
|
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. |
| int (*Gsasl_server_callback_cram_md5) (Gsasl_session_ctx * ctx, char * username, char * challenge, char * response) | Prototype |
|
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. |
The DIGEST-MD5 mechanism is based on the same cryptographic operation as CRAM-MD5 but supports more features, such as an authorization identity (proxy authentication) and cryptographic protection of data. Like CRAM-MD5, only a hashed password is transfered, which means that you cannot use e.g. PAM as a backend since it does not support extraction of passwords. Two ways of validating the user is provided, either by having the SASL mechanism retrieve the raw password from the application and perform the validation internally, or by having the SASL mechanism retrieve a hashed version of the secret. The advantage of using the latter method is that you do not need to store plain text user passwords on the server, but rather a one-way hash of the username, realm and password. Still, this one-way hash of the secret should be handled the same way as a clear text password. The advantage is that if someone steals the one-way hash she cannot immediately read users' password. If both the callbacks are specified by the application, the one which retrieve the secret hash will be used.
While not documented in the original DIGEST-MD5 specification, this implementation normalizes the username and the authentication identity using the Unicode 3.2 NFKC form according to the proposed update of DIGEST-MD5.
This mechanism is only enabled in the client and server if you implement the respectively callbacks below and set them in the library (see Callback Functions).
| int (*Gsasl_client_callback_authentication_id) (Gsasl_session_ctx * ctx, char * out, size_t * outlen) | Prototype |
|
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 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. |
| int (*Gsasl_client_callback_authorization_id) (Gsasl_session_ctx * ctx, char * out, size_t * outlen) | Prototype |
|
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 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. |
| int (*Gsasl_client_callback_password) (Gsasl_session_ctx * ctx, char * out, size_t * outlen) | Prototype |
|
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 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. |
| int (*Gsasl_client_callback_service) (Gsasl_session_ctx * ctx, char * service, size_t * servicelen, char * hostname, size_t * hostnamelen, char * servicename, size_t * servicenamelen) | Prototype |
|
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. |
| int (*Gsasl_server_callback_retrieve) (Gsasl_session_ctx * ctx, char * authentication_id, char * authorization_id, char * realm, char * key, size_t * keylen) | Prototype |
|
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. |
| int (*Gsasl_server_callback_digest_md5) (Gsasl_session_ctx * ctx, char * username, char * realm, char * secrethash) | Prototype |
|
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. |
The NTLM mechanism uses username (authorization identity only) and password to authenticate users. Only the client side is implemented. This mechanism is only enabled in the client if you implement the callbacks below and set them in the library (see Callback Functions).
Note: Libntlm uses assert in some places, it may thus crash
your client if it is given bad input.
| int (*Gsasl_client_callback_authorization_id) (Gsasl_session_ctx * ctx, char * out, size_t * outlen) | Prototype |
|
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 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. |
| int (*Gsasl_client_callback_password) (Gsasl_session_ctx * ctx, char * out, size_t * outlen) | Prototype |
|
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 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. |
The SECURID mechanism uses authentication and authorization identity and a passcode from a hardware token to authenticate users. This mechanism is only enabled in the client and server if you implement the respectively callbacks below and set them in the library (see Callback Functions).
| int (*Gsasl_client_callback_authentication_id) (Gsasl_session_ctx * ctx, char * out, size_t * outlen) | Prototype |
|
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 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. |
| int (*Gsasl_client_callback_authorization_id) (Gsasl_session_ctx * ctx, char * out, size_t * outlen) | Prototype |
|
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 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. |
| int (*Gsasl_client_callback_passcode) (Gsasl_session_ctx * ctx, char * out, size_t * outlen) | Prototype |
|
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 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. |
| int (*Gsasl_server_callback_validate) (Gsasl_session_ctx * ctx, char * authentication_id, char * authorization_id, char * passcode, char * pin, char * suggestpin, size_t * suggestpinlen) | Prototype |
|
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. |
The GSSAPI mechanism uses a framework similar to SASL for authenticating the user. While GSSAPI can be implemented using many techniques, libgsasl currently links with GSS, Heimdal or MIT Kerberos and is limited to Kerberos 5 only. The GSSAPI client mechanism assumes the user acquired credentials (kerberos tickets) before it is invoked (it will fail if this has not been done). The client need (via callbacks) the name of the service and the name of the user. The server needs the name of the service and a function that authorizes a user. This mechanism is only enabled in the client and server if you implement the respectively callbacks below and set them in the library (see Callback Functions).
| int (*Gsasl_client_callback_authentication_id) (Gsasl_session_ctx * ctx, char * out, size_t * outlen) | Prototype |
|
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 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. |
| int (*Gsasl_client_callback_service) (Gsasl_session_ctx * ctx, char * service, size_t * servicelen, char * hostname, size_t * hostnamelen, char * servicename, size_t * servicenamelen) | Prototype |
|
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. |
| int (*Gsasl_server_callback_service) (Gsasl_session_ctx * ctx, char * service, size_t * servicelen, char * hostname, size_t * hostnamelen) | Prototype |
|
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. |
| int (*Gsasl_server_callback_gssapi) (Gsasl_session_ctx * ctx, char * clientname, char * authentication_id) | Prototype |
|
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;
}
|
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). The non-infrastructure mode is chosen when the Gsasl_client_callback_authorization_id callback prototype is implemented by the application. In non-infrastructure mode, the client must specify (via callbacks) the name of the user, and optionally the server name and realm. The server must be able to retrieve passwords given the name of the user.
In the infrastructure mode (proxied or otherwise), it allows clients and servers to authenticate via SASL in an RFC 1510 environment, using a trusted third party, a “Key Distribution Central”. In the normal mode, clients aquire tickets out of band and then invokes a one roundtrip AP-REQ and AP-REP exchange. In the proxied mode, which can be used by clients without IP addresses or without connectivity to the KDC (e.g., when the KDC is IPv4 and the client is IPV6-only), the client uses the server to proxy ticket requests and finishes with the AP-REQ/AP-REP exchange. In infrastructure mode (proxied or otherwise), the client nor server need to implement any callbacks (this will likely change later, to allow a server to authorize users, similar to the GSSAPI callback).
| int (*Gsasl_client_callback_authentication_id) (Gsasl_session_ctx * ctx, char * out, size_t * outlen) | Prototype |
|
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 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. |
| int (*Gsasl_client_callback_authorization_id) (Gsasl_session_ctx * ctx, char * out, size_t * outlen) | Prototype |
|
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 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. |
| int (*Gsasl_client_callback_password) (Gsasl_session_ctx * ctx, char * out, size_t * outlen) | Prototype |
|
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 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. |
| int (*Gsasl_server_callback_retrieve) (Gsasl_session_ctx * ctx, char * authentication_id, char * authorization_id, char * realm, char * key, size_t * keylen) | Prototype |
|
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. |
| int gsasl_init (Gsasl ** ctx) | Function |
|
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. Return value: GSASL_OK iff successful, otherwise GSASL_MALLOC_ERROR. |
| void gsasl_done (Gsasl * ctx) | Function |
|
ctx: libgsasl handle.
This function destroys a libgsasl handle. The handle must not be used with other libgsasl functions after this call. |
| int gsasl_client_mechlist (Gsasl * ctx, char ** out) | Function |
|
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. Return value: Returns GSASL_OK if successful, or error code. |
| int gsasl_server_mechlist (Gsasl * ctx, char ** out) | Function |
|
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. Return value: Returns GSASL_OK if successful, or error code. |
| int gsasl_client_support_p (Gsasl * ctx, const char * name) | Function |
|
ctx: libgsasl handle.
name: name of SASL mechanism. Return value: Returns 1 if the libgsasl client supports the named mechanism, otherwise 0. |
| int gsasl_server_support_p (Gsasl * ctx, const char * name) | Function |
|
ctx: libgsasl handle.
name: name of SASL mechanism. Return value: Returns 1 if the libgsasl server supports the named mechanism, otherwise 0. |
| const char * gsasl_client_suggest_mechanism (Gsasl * ctx, const char * mechlist) | Function |
|
ctx: libgsasl handle.
mechlist: input character array with SASL mechanism names, separated by invalid characters (e.g. SPC). Return value: Returns name of "best" SASL mechanism supported by the libgsasl client which is present in the input string. |
| const char * gsasl_server_suggest_mechanism (Gsasl * ctx, const char * mechlist) | Function |
|
ctx: libgsasl handle.
mechlist: input character array with SASL mechanism names, separated by invalid characters (e.g. SPC). Return value: Returns name of "best" SASL mechanism supported by the libgsasl server which is present in the input string. |
| Gsasl * gsasl_ctx_get (Gsasl_session * sctx) | Function |
|
sctx: libgsasl session handle
Return value: Returns the libgsasl handle given a libgsasl session handle. |
| void gsasl_application_data_set (Gsasl * ctx, void * appdata) | Function |
|
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 |
| void * gsasl_application_data_get (Gsasl * ctx) | Function |
|
ctx: libgsasl handle.
Retrieve application specific data from libgsasl handle. The
application data is set using Return value: Returns the application specific data, or NULL. |
| void gsasl_appinfo_set (Gsasl_session * sctx, void * appdata) | Function |
|
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 |
| void * gsasl_appinfo_get (Gsasl_session * sctx) | Function |
|
sctx: libgsasl client handle.
Retrieve application specific data from libgsasl session
handle. The application data is set using
Return value: Returns the application specific data, or NULL. |
| void gsasl_server_callback_validate_set (Gsasl * ctx, Gsasl_server_callback_validate cb) | Function |
|
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 gsasl_server_callback_validate_get (Gsasl * ctx) | Function |
|
ctx: libgsasl handle.
Return value: Returns the callback earlier set by calling
|
| void gsasl_server_callback_retrieve_set (Gsasl * ctx, Gsasl_server_callback_retrieve cb) | Function |
|
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 gsasl_server_callback_retrieve_get (Gsasl * ctx) | Function |
|
ctx: libgsasl handle.
Return value: Returns the callback earlier set by calling
|
| void gsasl_server_callback_cram_md5_set (Gsasl * ctx, Gsasl_server_callback_cram_md5 cb) | Function |
|
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 gsasl_server_callback_cram_md5_get (Gsasl * ctx) | Function |
|
ctx: libgsasl handle.
Return value: Returns the callback earlier set by calling
|
| void gsasl_server_callback_digest_md5_set (Gsasl * ctx, Gsasl_server_callback_digest_md5 cb) | Function |
|
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 gsasl_server_callback_digest_md5_get (Gsasl * ctx) | Function |
|
ctx: libgsasl handle.
Return value: Return the callback earlier set by calling
|
| void gsasl_server_callback_external_set (Gsasl * ctx, Gsasl_server_callback_external cb) | Function |
|
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 gsasl_server_callback_external_get (Gsasl * ctx) | Function |
|
ctx: libgsasl handle.
Return value: Returns the callback earlier set by calling
|
| void gsasl_server_callback_anonymous_set (Gsasl * ctx, Gsasl_server_callback_anonymous cb) | Function |
|
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 gsasl_server_callback_anonymous_get (Gsasl * ctx) | Function |
|
ctx: libgsasl handle.
Return value: Returns the callback earlier set by calling
|
| void gsasl_server_callback_realm_set (Gsasl * ctx, Gsasl_server_callback_realm cb) | Function |
|
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 gsasl_server_callback_realm_get (Gsasl * ctx) | Function |
|
ctx: libgsasl handle.
Return value: Returns the callback earlier set by calling
|
| void gsasl_server_callback_qop_set (Gsasl * ctx, Gsasl_server_callback_qop cb) | Function |
|
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 gsasl_server_callback_qop_get (Gsasl * ctx) | Function |
|
ctx: libgsasl handle.
Return value: Returns the callback earlier set by calling
|
| void gsasl_server_callback_maxbuf_set (Gsasl * ctx, Gsasl_server_callback_maxbuf cb) | Function |
|
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 gsasl_server_callback_maxbuf_get (Gsasl * ctx) | Function |
|
ctx: libgsasl handle.
Return value: Returns the callback earlier set by calling
|
| void gsasl_server_callback_cipher_set (Gsasl * ctx, Gsasl_server_callback_cipher cb) | Function |
|
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 gsasl_server_callback_cipher_get (Gsasl * ctx) | Function |
|
ctx: libgsasl handle.
Return value: Returns the callback earlier set by calling
|
| void gsasl_server_callback_securid_set (Gsasl * ctx, Gsasl_server_callback_securid cb) | Function |
|
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 gsasl_server_callback_securid_get (Gsasl * ctx) | Function |
|
ctx: libgsasl handle.
Return value: Returns the callback earlier set by calling
|
| void gsasl_server_callback_gssapi_set (Gsasl * ctx, Gsasl_server_callback_gssapi cb) | Function |
|
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
|
| Gsasl_server_callback_gssapi gsasl_server_callback_gssapi_get (Gsasl * ctx) | Function |
|
ctx: libgsasl handle.
Return value: Returns the callback earlier set by calling
|
| void gsasl_server_callback_service_set (Gsasl * ctx, Gsasl_server_callback_service cb) | Function |
|
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 gsasl_server_callback_service_get (Gsasl * ctx) | Function |
|
ctx: libgsasl handle.
Return value: Returns the callback earlier set by calling
|
| void gsasl_client_callback_authentication_id_set (Gsasl * ctx, Gsasl_client_callback_authentication_id cb) | Function |
|
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 gsasl_client_callback_authentication_id_get (Gsasl * ctx) | Function |
|
ctx: libgsasl handle.
Return value: Returns the callback earlier set by calling
|
| void gsasl_client_callback_authorization_id_set (Gsasl * ctx, Gsasl_client_callback_authorization_id cb) | Function |
|
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 gsasl_client_callback_authorization_id_get (Gsasl * ctx) | Function |
|
ctx: libgsasl handle.
Return value: Returns the callback earlier set by calling
|
| void gsasl_client_callback_password_set (Gsasl * ctx, Gsasl_client_callback_password cb) | Function |
|
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 gsasl_client_callback_password_get (Gsasl * ctx) | Function |
|
ctx: libgsasl handle.
Return value: Returns the callback earlier set by calling
|
| void gsasl_client_callback_passcode_set (Gsasl * ctx, Gsasl_client_callback_passcode cb) | Function |
|
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 gsasl_client_callback_passcode_get (Gsasl * ctx) | Function |
|
ctx: libgsasl handle.
Return value: Returns the callback earlier set by calling
|
| void gsasl_client_callback_pin_set (Gsasl * ctx, Gsasl_client_callback_pin cb) | Function |
|
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 gsasl_client_callback_pin_get (Gsasl * ctx) | Function |
|
ctx: libgsasl handle.
Return value: Returns the callback earlier set by calling
|
| void gsasl_client_callback_service_set (Gsasl * ctx, Gsasl_client_callback_service cb) | Function |
|
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 gsasl_client_callback_service_get (Gsasl * ctx) | Function |
|
ctx: libgsasl handle.
Return value: Returns the callback earlier set by calling
|
| void gsasl_client_callback_anonymous_set (Gsasl * ctx, Gsasl_client_callback_anonymous cb) | Function |
|
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 gsasl_client_callback_anonymous_get (Gsasl * ctx) | Function |
|
ctx: libgsasl handle.
Return value: Returns the callback earlier set by calling
|
| void gsasl_client_callback_qop_set (Gsasl * ctx, Gsasl_client_callback_qop cb) | Function |
|
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 gsasl_client_callback_qop_get (Gsasl * ctx) | Function |
|
ctx: libgsasl handle.
Return value: Returns the callback earlier set by calling
|
| void gsasl_client_callback_maxbuf_set (Gsasl * ctx, Gsasl_client_callback_maxbuf cb) | Function |
|
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 gsasl_client_callback_maxbuf_get (Gsasl * ctx) | Function |
|
ctx: libgsasl handle.
Return value: Returns the callback earlier set by calling
|
| void gsasl_client_callback_realm_set (Gsasl * ctx, Gsasl_client_callback_realm cb) | Function |
|
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 gsasl_client_callback_realm_get (Gsasl * ctx) | Function |
|
ctx: libgsasl handle.
Return value: Returns the callback earlier set by calling
|
| int gsasl_client_start (Gsasl * ctx, const char * mech, Gsasl_session ** sctx) | Function |
|
ctx: libgsasl handle.
mech: name of SASL mechanism. sctx: pointer to client handle. This functions initiates a client SASL authentication. This function must be called before any other gsasl_client_*() function is called. Return value: Returns GSASL_OK if successful, or error code. |
| int gsasl_server_start (Gsasl * ctx, const char * mech, Gsasl_session ** sctx) | Function |
|
ctx: libgsasl handle.
mech: name of SASL mechanism. sctx: pointer to server handle. This functions initiates a server SASL authentication. This function must be called before any other gsasl_server_*() function is called. Return value: Returns GSASL_OK if successful, or error code. |
| int gsasl_step (Gsasl_session * sctx, const char * input, size_t input_len, char ** output, size_t * output_len) | Function |
|
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 The contents of the Return value: Returns GSASL_OK if authenticated terminated successfully, GSASL_NEEDS_MORE if more data is needed, or error code. |
| int gsasl_step64 (Gsasl_session * sctx, const char * b64input, char ** b64output) | Function |
|
sctx: libgsasl client handle.
b64input: input base64 encoded byte array. b64output: newly allocated output base64 encoded byte array. This is a simple wrapper around The contents of the Return value: Returns GSASL_OK if authenticated terminated successfully, GSASL_NEEDS_MORE if more data is needed, or error code. |
| void gsasl_finish (Gsasl_session * sctx) | Function |
|
sctx: libgsasl session handle.
Destroy a libgsasl client or server handle. The handle must not be used with other libgsasl functions after this call. |
| int gsasl_encode (Gsasl_session * sctx, const char * input, size_t input_len, char * output, size_t * output_len) | Function |
|
sctx: libgsasl session handle.
input: input byte array. input_len: size of input byte array. output: output byte array. output_len: size of output byte array. Encode data according to negotiated SASL mechanism. This might mean that data is integrity or privacy protected. Return value: Returns GSASL_OK if encoding was successful, otherwise an error code. |
| int gsasl_decode (Gsasl_session * sctx, const char * input, size_t input_len, char * output, size_t * output_len) | Function |
|
sctx: libgsasl session handle.
input: input byte array. input_len: size of input byte array. output: output byte array. output_len: size of output byte array. Decode data according to negotiated SASL mechanism. This might mean that data is integrity or privacy protected. Return value: Returns GSASL_OK if encoding was successful, otherwise an error code. |
| char * gsasl_stringprep_nfkc (const char * in, ssize_t len) | Function |
|
in: a UTF-8 encoded string.
len: length of 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 |
| char * gsasl_stringprep_saslprep (const char * in, int * stringprep_rc) | Function |
|
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 |
| char * gsasl_stringprep_trace (const char * in, int * stringprep_rc) | Function |
|
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 |
| int gsasl_base64_encode (char const * src, size_t srclength, char * target, size_t targsize) | Function |
|
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. |
| int gsasl_base64_decode (char const * src, char * target, size_t targsize) | Function |
|
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. |
| int gsasl_md5pwd_get_password (const char * filename, const char * username, char * key, size_t * keylen) | Function |
|
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 username\tpassword. This function removes \r and \n at the end of lines before processing. 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. |
| int gsasl_randomize (int strong, char * data, size_t datalen) | Function |
|
strong: 0 iff operation should not block, non-0 for very strong randomness.
data: output array to be filled with random data. datalen: size of output array. Store cryptographically random data of given size in the provided buffer. Return value: Returns GSASL_OK iff successful. |
| int gsasl_md5 (const char * in, size_t inlen, char * out[MD5_DIGEST_SIZE]) | Function |
|
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 Return value: Returns GSASL_OK iff successful. |
| int gsasl_hmac_md5 (const char * key, size_t keylen, const char * in, size_t inlen, char * outhash[MD5_DIGEST_SIZE]) | Function |
|
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 Return value: Returns GSASL_OK iff successful. |
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.
| int gsasl_client_listmech (Gsasl_ctx * ctx, char * out, size_t * outlen) | Function |
|
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 out=NULL. Note that this function is obsolete and may be removed in the future. Return value: Returns GSASL_OK if successful, or error code. |
| int gsasl_server_listmech (Gsasl_ctx * ctx, char * out, size_t * outlen) | Function |
|
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 out=NULL. Note that this function is obsolete and may be removed in the future. Return value: Returns GSASL_OK if successful, or error code. |
| int gsasl_client_step (Gsasl_session_ctx * sctx, const char * input, size_t input_len, char * output, size_t * output_len) | Function |
|
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. Note that this function is obsolete and may be removed in the future. Return value: Returns GSASL_OK if authenticated terminated successfully, GSASL_NEEDS_MORE if more data is needed, or error code. |
| int gsasl_server_step (Gsasl_session_ctx * sctx, const char * input, size_t input_len, char * output, size_t * output_len) | Function |
|
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. Note that this function is obsolete and may be removed in the future. Return value: Returns GSASL_OK if authenticated terminated successfully, GSASL_NEEDS_MORE if more data is needed, or error code. |
| int gsasl_client_step_base64 (Gsasl_session_ctx * sctx, const char * b64input, char * b64output, size_t b64output_len) | Function |
|
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 Note that this function is obsolete and may be removed in the future. Return value: See |
| int gsasl_server_step_base64 (Gsasl_session_ctx * sctx, const char * b64input, char * b64output, size_t b64output_len) | Function |
|
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 Note that this function is obsolete and may be removed in the future. Return value: See |
| void gsasl_client_finish (Gsasl_session_ctx * sctx) | Function |
|
sctx: libgsasl client handle.
Destroy a libgsasl client handle. The handle must not be used with other libgsasl functions after this call. Note that this function is obsolete and may be removed in the future. |
| void gsasl_server_finish (Gsasl_session_ctx * sctx) | Function |
|
sctx: libgsasl server handle.
Destroy a libgsasl server handle. The handle must not be used with other libgsasl functions after this call. Note that this function is obsolete and may be removed in the future. |
| Gsasl_ctx * gsasl_client_ctx_get (Gsasl_session_ctx * sctx) | Function |
|
sctx: libgsasl client handle
Note that this function is obsolete and may be removed in the future. Return value: Returns the libgsasl handle given a libgsasl client handle. |
| void gsasl_client_application_data_set (Gsasl_session_ctx * sctx, void * application_data) | Function |
|
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 Note that this function is obsolete and may be removed in the future. |
| void * gsasl_client_application_data_get (Gsasl_session_ctx * sctx) | Function |
|
sctx: libgsasl client handle.
Retrieve application specific data from libgsasl client handle. The
application data is set using Note that this function is obsolete and may be removed in the future. Return value: Returns the application specific data, or NULL. |
| Gsasl_ctx * gsasl_server_ctx_get (Gsasl_session_ctx * sctx) | Function |
|
sctx: libgsasl server handle
Note that this function is obsolete and may be removed in the future. Return value: Returns the libgsasl handle given a libgsasl server handle. |
| void gsasl_server_application_data_set (Gsasl_session_ctx * sctx, void * application_data) | Function |
|
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 Note that this function is obsolete and may be removed in the future. |
| void * gsasl_server_application_data_get (Gsasl_session_ctx * sctx) | Function |
|
sctx: libgsasl server handle.
Retrieve application specific data from libgsasl server handle. The
application data is set using Note that this function is obsolete and may be removed in the future. Return value: Returns the application specific data, or NULL. |
Most functions in `Libgsasl' are returning an error if they fail. For this reason, the application should always catch the error condition and take appropriate measures, for example by releasing the resources and passing the error up to the caller, or by displaying a descriptive message to the user and cancelling the operation.
Some error values do not indicate a system error or an error in the operation, but the result of an operation that failed properly.
Errors are returned as an int. Except for the OK case an
application should always use the constants instead of their numeric
value. Applications are encouraged to use the constants even for OK
as it improves readability. Possible values are:
GSASL_OK
0 so you may use it in boolean constructs.
GSASL_NEEDS_MORE
GSASL_UNKNOWN_MECHANISM
GSASL_MECHANISM_CALLED_TOO_MANY_TIMES
GSASL_TOO_SMALL_BUFFER
GSASL_FOPEN_ERROR
GSASL_FCLOSE_ERROR
GSASL_MALLOC_ERROR
GSASL_BASE64_ERROR
GSASL_GCRYPT_ERROR
GSASL_GSSAPI_RELEASE_BUFFER_ERROR
GSASL_GSSAPI_IMPORT_NAME_ERROR
GSASL_GSSAPI_INIT_SEC_CONTEXT_ERROR
GSASL_GSSAPI_ACCEPT_SEC_CONTEXT_ERROR
GSASL_GSSAPI_UNWRAP_ERROR
GSASL_GSSAPI_WRAP_ERROR
GSASL_GSSAPI_ACQUIRE_CRED_ERROR
GSASL_GSSAPI_DISPLAY_NAME_ERROR
GSASL_GSSAPI_UNSUPPORTED_PROTECTION_ERROR
GSASL_NEED_CLIENT_ANONYMOUS_CALLBACK
GSASL_NEED_CLIENT_PASSWORD_CALLBACK
GSASL_NEED_CLIENT_PASSCODE_CALLBACK
GSASL_NEED_CLIENT_PIN_CALLBACK
GSASL_NEED_CLIENT_AUTHORIZATION_ID_CALLBACK
GSASL_NEED_CLIENT_AUTHENTICATION_ID_CALLBACK
GSASL_NEED_CLIENT_SERVICE_CALLBACK
GSASL_NEED_SERVER_VALIDATE_CALLBACK
GSASL_NEED_SERVER_CRAM_MD5_CALLBACK
GSASL_NEED_SERVER_DIGEST_MD5_CALLBACK
GSASL_NEED_SERVER_ANONYMOUS_CALLBACK
GSASL_NEED_SERVER_EXTERNAL_CALLBACK
GSASL_NEED_SERVER_REALM_CALLBACK
GSASL_NEED_SERVER_SECURID_CALLBACK
GSASL_NEED_SERVER_SERVICE_CALLBACK
GSASL_NEED_SERVER_GSSAPI_CALLBACK
GSASL_NEED_SERVER_RETRIEVE_CALLBACK
GSASL_MECHANISM_PARSE_ERROR
GSASL_AUTHENTICATION_ERROR
GSASL_CANNOT_GET_CTX
GSASL_INTEGRITY_ERROR
GSASL_NO_MORE_REALMS
GSASL_NO_CLIENT_CODE
GSASL_NO_SERVER_CODE
GSASL_INVALID_HANDLE
| const char * gsasl_strerror (int err) | Function |
|
err: libgsasl error code
Return value: Returns a pointer to a statically allocated string
containing a description of the error with the error value |
This chapter contains example code which illustrate how `Libgsasl' can be used when writing your own application.
This is the minimal program which uses `Libgsasl' (including internationalization features) without doing anything.
#include <locale.h>
#include <stdio.h>
#include <gsasl.h>
/* Build using the following command:
* gcc -o foo foo.c `libgsasl-config --cflags --libs`
*/
int
main (int argc, char *argv[])
{
Gsasl_ctx *ctx;
int res;
setlocale (LC_ALL, "");
if (gsasl_check_version(GSASL_VERSION) == NULL)
{
fprintf(stderr, "Libgsasl is %s expected %s\n",
gsasl_check_version(NULL), GSASL_VERSION);
return 1;
}
res = gsasl_init (&ctx);
if (res != GSASL_OK)
{
fprintf(stderr, "Cannot initialize libgsasl: %s\n",
gsasl_strerror(res));
return 1;
}
/* Do things here ... */
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 mechanism uses a GSS-API implementation, such as GSSLib by Simon Josefsson.
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.
--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 the query the user on the terminal.
-a, --authentication-id=STRING Identity of credential owner.
--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.
-n, --anonymous-token=STRING Token for anonymous authentication, usually
mail address (ANONYMOUS only).
-p, --password=STRING Password for authentication (insecure for
non-testing purposes).
--passcode=NUMBER Passcode for authentication (SECURID only).
--quality-of-protection=<auth | auth-int | auth-conf>
How application payload will be protected. "auth"
means no protection, "auth-int" means integrity
protection, "auth-conf" means integrity and
confidentialiy protection. Currently only used by
DIGEST-MD5, where the default is "auth-conf".
-r, --realm=STRING Realm (may be given more than once iff server).
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).
-z, --authorization-id=STRING Identity to request service for.
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
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gsasl: Invoking gsasl
(: KERBEROS_V5, GSSAPI, SECURID, NTLM, DIGEST-MD5, CRAM-MD5, LOGIN, PLAIN, ANONYMOUS, EXTERNAL
gsasl: Invoking gsasl
gsasl_appinfo_get: Callback Functions
gsasl_appinfo_set: Callback Functions
gsasl_application_data_get: Callback Functions
gsasl_application_data_set: Callback Functions
gsasl_base64_decode: Utilities
gsasl_base64_encode: Utilities
gsasl_check_version: Version Check
gsasl_client_application_data_get: Old Functions
gsasl_client_application_data_set: Old Functions
gsasl_client_callback_anonymous_get: Callback Functions
gsasl_client_callback_anonymous_set: Callback Functions
gsasl_client_callback_authentication_id_get: Callback Functions
gsasl_client_callback_authentication_id_set: Callback Functions
gsasl_client_callback_authorization_id_get: Callback Functions
gsasl_client_callback_authorization_id_set: Callback Functions
gsasl_client_callback_maxbuf_get: Callback Functions
gsasl_client_callback_maxbuf_set: Callback Functions
gsasl_client_callback_passcode_get: Callback Functions
gsasl_client_callback_passcode_set: Callback Functions
gsasl_client_callback_password_get: Callback Functions
gsasl_client_callback_password_set: Callback Functions
gsasl_client_callback_pin_get: Callback Functions
gsasl_client_callback_pin_set: Callback Functions
gsasl_client_callback_qop_get: Callback Functions
gsasl_client_callback_qop_set: Callback Functions
gsasl_client_callback_realm_get: Callback Functions
gsasl_client_callback_realm_set: Callback Functions
gsasl_client_callback_service_get: Callback Functions
gsasl_client_callback_service_set: Callback Functions
gsasl_client_ctx_get: Old Functions
gsasl_client_finish: Old Functions
gsasl_client_listmech: Old Functions
gsasl_client_mechlist: Global Functions
gsasl_client_start: Session Functions
gsasl_client_step: Old Functions
gsasl_client_step_base64: Old Functions
gsasl_client_suggest_mechanism: Global Functions
gsasl_client_support_p: Global Functions
gsasl_ctx_get: Callback Functions
gsasl_decode: Session Functions
gsasl_done: Global Functions
gsasl_encode: Session Functions
gsasl_finish: Session Functions
gsasl_hmac_md5: Utilities
gsasl_init: Global Functions
gsasl_md5: Utilities
gsasl_md5pwd_get_password: Utilities
gsasl_randomize: Utilities
gsasl_server_application_data_get: Old Functions
gsasl_server_application_data_set: Old Functions
gsasl_server_callback_anonymous_get: Callback Functions
gsasl_server_callback_anonymous_set: Callback Functions
gsasl_server_callback_cipher_get: Callback Functions
gsasl_server_callback_cipher_set: Callback Functions
gsasl_server_callback_cram_md5_get: Callback Functions
gsasl_server_callback_cram_md5_set: Callback Functions
gsasl_server_callback_digest_md5_get: Callback Functions
gsasl_server_callback_digest_md5_set: Callback Functions
gsasl_server_callback_external_get: Callback Functions
gsasl_server_callback_external_set: Callback Functions
gsasl_server_callback_gssapi_get: Callback Functions
gsasl_server_callback_gssapi_set: Callback Functions
gsasl_server_callback_maxbuf_get: Callback Functions
gsasl_server_callback_maxbuf_set: Callback Functions
gsasl_server_callback_qop_get: Callback Functions
gsasl_server_callback_qop_set: Callback Functions
gsasl_server_callback_realm_get: Callback Functions
gsasl_server_callback_realm_set: Callback Functions
gsasl_server_callback_retrieve_get: Callback Functions
gsasl_server_callback_retrieve_set: Callback Functions
gsasl_server_callback_securid_get: Callback Functions
gsasl_server_callback_securid_set: Callback Functions
gsasl_server_callback_service_get: Callback Functions
gsasl_server_callback_service_set: Callback Functions
gsasl_server_callback_validate_get: Callback Functions
gsasl_server_callback_validate_set: Callback Functions
gsasl_server_ctx_get: Old Functions
gsasl_server_finish: Old Functions
gsasl_server_listmech: Old Functions
gsasl_server_mechlist: Global Functions
gsasl_server_start: Session Functions
gsasl_server_step: Old Functions
gsasl_server_step_base64: Old Functions
gsasl_server_suggest_mechanism: Global Functions
gsasl_server_support_p: Global Functions
gsasl_step: Session Functions
gsasl_step64: Session Functions
gsasl_strerror: Error strings
gsasl_stringprep_nfkc: Utilities
gsasl_stringprep_saslprep: Utilities
gsasl_stringprep_trace: Utilities