Copyright © 2002 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 no Invariant Sections, with the Front-Cover texts being "A GNU Manual," and with the Back-Cover Texts as in (a) below. A copy of the license is included in the section entitled "GNU Free Documentation License."(a) The FSF's Back-Cover Text is: "You have freedom to copy and modify this GNU Manual, like GNU software. Copies published by the Free Software Foundation raise funds for GNU development."
Appendices
Indices
`Libgsasl' is a library that provides a Simple Authentication and Security Layer (SASL) interface for applications. Included are also a set of well known SASL mechanisms.
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.
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 not. Rather, it uses callbacks back into the application to answer these questions.
This section describes SASL from a protocol point of view1.
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.
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'.
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 that the the version of the library is at minimum the one
given as a string in req_version and return the actual
version string of the library; return NULL if the condition is not
met. If |
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
`Liblibgsasl' 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 `Liblibgsasl' libararies (in particular, the -llibgsasl
option). The example shows how to link foo.o with the `Liblibgsasl'
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`
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)
break;
write_to_client(output);
input = read_from_client();
}
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 MIT's GSSAPI Kerberos 5 library 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;
}
|
| int gsasl_init (Gsasl_ctx ** 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. GSASL_OK iff successful, otherwise GSASL_MALLOC_ERROR. |
| void gsasl_done (Gsasl_ctx * 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_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. 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. Returns GSASL_OK if successful, or error code. |
| int gsasl_client_support_p (Gsasl_ctx * ctx, const char * name) | Function |
|
ctx: libgsasl handle. name: name of SASL mechanism. Returns 1 if the libgsasl client supports the named mechanism, otherwise 0. |
| int gsasl_server_support_p (Gsasl_ctx * ctx, const char * name) | Function |
|
ctx: libgsasl handle. name: name of SASL mechanism. Returns 1 if the libgsasl server supports the named mechanism, otherwise 0. |
| const char * gsasl_client_suggest_mechanism (Gsasl_ctx * ctx, const char * mechlist) | Function |
|
ctx: libgsasl handle. mechlist: input character array with SASL mechanism names, separated by invalid characters (e.g. SPC). 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 * ctx, const char * mechlist) | Function |
|
ctx: libgsasl handle. mechlist: input character array with SASL mechanism names, separated by invalid characters (e.g. SPC). Returns name of "best" SASL mechanism supported by the libgsasl server which is present in the input string. |
| Gsasl_ctx * gsasl_client_ctx_get (Gsasl_session_ctx * cctx) | Function |
|
cctx: libgsasl client handle Returns the libgsasl handle given a libgsasl client handle. |
| Gsasl_ctx * gsasl_server_ctx_get (Gsasl_session_ctx * sctx) | Function |
|
Returns the libgsasl handle given a libgsasl server handle. |
| void gsasl_application_data_set (Gsasl_ctx * ctx, void * application_data) | Function |
|
ctx: libgsasl handle. application_data: opaque pointer to application specific data. Store application specific data in the libgsasl handle. The application data can be later (for instance, inside a callback) be retrieved by calling gsasl_application_data_get(). It is normally used by the application to maintain state between the main program and the callback. |
| void * gsasl_application_data_get (Gsasl_ctx * ctx) | Function |
|
ctx: libgsasl handle. Retrieve application specific data from libgsasl handle. The application data is set using gsasl_application_data_set(). It is normally used by the application to maintain state between the main program and the callback. Returns the application specific data, or NULL. |
| void gsasl_client_application_data_set (Gsasl_session_ctx * cctx, void * application_data) | Function |
|
application_data: opaque pointer to application specific data. Store application specific data in the libgsasl client handle. The application data can be later (for instance, inside a callback) be retrieved by calling gsasl_client_application_data_get(). It is normally used by the application to maintain state between the main program and the callback. |
| void * gsasl_client_application_data_get (Gsasl_session_ctx * cctx) | Function |
|
Retrieve application specific data from libgsasl client handle. The application data is set using gsasl_client_application_data_set(). It is normally used by the application to maintain state between the main program and the callback. Returns the application specific data, or NULL. |
| void gsasl_server_application_data_set (Gsasl_session_ctx * sctx, void * application_data) | Function |
|
application_data: opaque pointer to application specific data. Store application specific data in the libgsasl server handle. The application data can be later (for instance, inside a callback) be retrieved by calling gsasl_server_application_data_get(). It is normally used by the application to maintain state between the main program and the callback. |
| void * gsasl_server_application_data_get (Gsasl_session_ctx * sctx) | Function |
|
Retrieve application specific data from libgsasl server handle. The application data is set using gsasl_server_application_data_set(). It is normally used by the application to maintain state between the main program and the callback. Returns the application specific data, or NULL. |
| void gsasl_client_callback_authentication_id_set (Gsasl_ctx * 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_get(). |
| Gsasl_client_callback_authentication_id gsasl_client_callback_authentication_id_get (Gsasl_ctx * ctx) | Function |
|
ctx: libgsasl handle. Return the callback earlier set by calling gsasl_client_callback_authentication_id_set(). |
| void gsasl_client_callback_authorization_id_set (Gsasl_ctx * 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_get(). |
| Gsasl_client_callback_authorization_id gsasl_client_callback_authorization_id_get (Gsasl_ctx * ctx) | Function |
|
ctx: libgsasl handle. Return the callback earlier set by calling gsasl_client_callback_authorization_id_set(). |
| void gsasl_client_callback_password_set (Gsasl_ctx * 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_get(). |
| Gsasl_client_callback_password gsasl_client_callback_password_get (Gsasl_ctx * ctx) | Function |
|
ctx: libgsasl handle. Return the callback earlier set by calling gsasl_client_callback_password_set(). |
| void gsasl_client_callback_passcode_set (Gsasl_ctx * 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_get(). |
| Gsasl_client_callback_passcode gsasl_client_callback_passcode_get (Gsasl_ctx * ctx) | Function |
|
ctx: libgsasl handle. Return the callback earlier set by calling gsasl_client_callback_passcode_set(). |
| void gsasl_client_callback_pin_set (Gsasl_ctx * 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_get(). |
| Gsasl_client_callback_pin gsasl_client_callback_pin_get (Gsasl_ctx * ctx) | Function |
|
ctx: libgsasl handle. Return the callback earlier set by calling gsasl_client_callback_pin_set(). |
| void gsasl_client_callback_service_set (Gsasl_ctx * 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_get(). |
| Gsasl_client_callback_service gsasl_client_callback_service_get (Gsasl_ctx * ctx) | Function |
|
ctx: libgsasl handle. Return the callback earlier set by calling gsasl_client_callback_service_set(). |
| void gsasl_client_callback_anonymous_set (Gsasl_ctx * 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_get(). |
| Gsasl_client_callback_anonymous gsasl_client_callback_anonymous_get (Gsasl_ctx * ctx) | Function |
|
ctx: libgsasl handle. Return the callback earlier set by calling gsasl_client_callback_anonymous_set(). |
| void gsasl_client_callback_qop_set (Gsasl_ctx * 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_get(). |
| Gsasl_client_callback_qop gsasl_client_callback_qop_get (Gsasl_ctx * ctx) | Function |
|
ctx: libgsasl handle. Return the callback earlier set by calling gsasl_client_callback_qop_set(). |
| void gsasl_client_callback_maxbuf_set (Gsasl_ctx * 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_get(). |
| Gsasl_client_callback_maxbuf gsasl_client_callback_maxbuf_get (Gsasl_ctx * ctx) | Function |
|
ctx: libgsasl handle. Return the callback earlier set by calling gsasl_client_callback_maxbuf_set(). |
| void gsasl_server_callback_validate_set (Gsasl_ctx * 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_get(). |
| Gsasl_server_callback_validate gsasl_server_callback_validate_get (Gsasl_ctx * ctx) | Function |
|
ctx: libgsasl handle. Return the callback earlier set by calling gsasl_server_callback_validate_set(). |
| void gsasl_server_callback_retrieve_set (Gsasl_ctx * 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_get(). |
| Gsasl_server_callback_retrieve gsasl_server_callback_retrieve_get (Gsasl_ctx * ctx) | Function |
|
ctx: libgsasl handle. Return the callback earlier set by calling gsasl_server_callback_retrieve_set(). |
| void gsasl_server_callback_cram_md5_set (Gsasl_ctx * 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_get(). |
| Gsasl_server_callback_cram_md5 gsasl_server_callback_cram_md5_get (Gsasl_ctx * ctx) | Function |
|
ctx: libgsasl handle. Return the callback earlier set by calling gsasl_server_callback_cram_md5_set(). |
| void gsasl_server_callback_digest_md5_set (Gsasl_ctx * 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_get(). |
| Gsasl_server_callback_digest_md5 gsasl_server_callback_digest_md5_get (Gsasl_ctx * ctx) | Function |
|
ctx: libgsasl handle. Return the callback earlier set by calling gsasl_server_callback_digest_md5_set(). |
| void gsasl_server_callback_external_set (Gsasl_ctx * 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_get(). |
| Gsasl_server_callback_external gsasl_server_callback_external_get (Gsasl_ctx * ctx) | Function |
|
ctx: libgsasl handle. Return the callback earlier set by calling gsasl_server_callback_external_set(). |
| void gsasl_server_callback_anonymous_set (Gsasl_ctx * 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_get(). |
| Gsasl_server_callback_anonymous gsasl_server_callback_anonymous_get (Gsasl_ctx * ctx) | Function |
|
ctx: libgsasl handle. Return the callback earlier set by calling gsasl_server_callback_anonymous_set(). |
| void gsasl_server_callback_realm_set (Gsasl_ctx * 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_get(). |
| Gsasl_server_callback_realm gsasl_server_callback_realm_get (Gsasl_ctx * ctx) | Function |
|
ctx: libgsasl handle. Return the callback earlier set by calling gsasl_server_callback_realm_set(). |
| void gsasl_server_callback_qop_set (Gsasl_ctx * 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_get(). |
| Gsasl_server_callback_qop gsasl_server_callback_qop_get (Gsasl_ctx * ctx) | Function |
|
ctx: libgsasl handle. Return the callback earlier set by calling gsasl_server_callback_qop_set(). |
| void gsasl_server_callback_maxbuf_set (Gsasl_ctx * 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_get(). |
| Gsasl_server_callback_maxbuf gsasl_server_callback_maxbuf_get (Gsasl_ctx * ctx) | Function |
|
ctx: libgsasl handle. Return the callback earlier set by calling gsasl_server_callback_maxbuf_set(). |
| void gsasl_server_callback_cipher_set (Gsasl_ctx * 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_get(). |
| Gsasl_server_callback_cipher gsasl_server_callback_cipher_get (Gsasl_ctx * ctx) | Function |
|
ctx: libgsasl handle. Return the callback earlier set by calling gsasl_server_callback_cipher_set(). |
| void gsasl_server_callback_securid_set (Gsasl_ctx * 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_get(). |
| Gsasl_server_callback_securid gsasl_server_callback_securid_get (Gsasl_ctx * ctx) | Function |
|
ctx: libgsasl handle. Return the callback earlier set by calling gsasl_server_callback_securid_set(). |
| void gsasl_server_callback_gssapi_set (Gsasl_ctx * 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 krb5_userok()). The function should return GSASL_OK if the user should be permitted access, or an error code such as GSASL_AUTHENTICATION_ERROR on failure. The function can be later retrieved using gsasl_server_callback_gssapi_get(). |
| Gsasl_server_callback_gssapi gsasl_server_callback_gssapi_get (Gsasl_ctx * ctx) | Function |
|
ctx: libgsasl handle. Return the callback earlier set by calling gsasl_server_callback_gssapi_set(). |
| void gsasl_server_callback_service_set (Gsasl_ctx * 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_get(). |
| Gsasl_server_callback_service gsasl_server_callback_service_get (Gsasl_ctx * ctx) | Function |
|
ctx: libgsasl handle. Return the callback earlier set by calling gsasl_server_callback_service_set(). |
| int gsasl_client_start (Gsasl_ctx * ctx, const char * mech, Gsasl_session_ctx ** xctx) | Function |
|
ctx: libgsasl handle. mech: name of SASL mechanism. xctx: pointer to client handle. This functions initiates a client SASL authentication. This function must be called before any other gsasl_client_*() function is called. Returns GSASL_OK if successful, or error code. |
| int gsasl_server_start (Gsasl_ctx * ctx, const char * mech, Gsasl_session_ctx ** xctx) | Function |
|
ctx: libgsasl handle. mech: name of SASL mechanism. xctx: pointer to server handle. This functions initiates a server SASL authentication. This function must be called before any other gsasl_server_*() function is called. Returns GSASL_OK if successful, or error code. |
| int gsasl_client_step (Gsasl_session_ctx * xctx, const char * input, size_t input_len, char * output, size_t * output_len) | Function |
|
xctx: 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. 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 * xctx, const char * input, size_t input_len, char * output, size_t * output_len) | Function |
|
xctx: 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. 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 * xctx, const char * b64input, char * b64output, size_t b64output_len) | Function |
|
xctx: libgsasl client handle. b64input: input base64 encoded byte array. b64output: output base64 encoded byte array. b64output_len: size of output base64 encoded byte array. This is a simple wrapper around gsasl_client_step() that base64 decodes the input and base64 encodes the output. See gsasl_client_step(). |
| int gsasl_server_step_base64 (Gsasl_session_ctx * xctx, const char * b64input, char * b64output, size_t b64output_len) | Function |
|
xctx: libgsasl server handle. b64input: input base64 encoded byte array. b64output: output base64 encoded byte array. b64output_len: size of output base64 encoded byte array. This is a simple wrapper around gsasl_server_step() that base64 decodes the input and base64 encodes the output. See gsasl_server_step(). |
| void gsasl_client_finish (Gsasl_session_ctx * xctx) | Function |
|
xctx: libgsasl client handle. Destroy a libgsasl client handle. The handle must not be used with other libgsasl functions after this call. |
| void gsasl_server_finish (Gsasl_session_ctx * xctx) | Function |
|
xctx: libgsasl server handle. Destroy a libgsasl server handle. The handle must not be used with other libgsasl functions after this call. |
| int gsasl_encode (Gsasl_session_ctx * xctx, const char * input, size_t input_len, char * output, size_t * output_len) | Function |
|
xctx: 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. Returns GSASL_OK if encoding was successful, otherwise an error code. |
| int gsasl_decode (Gsasl_session_ctx * xctx, const char * input, size_t input_len, char * output, size_t * output_len) | Function |
|
xctx: 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. Returns GSASL_OK if encoding was successful, otherwise an error code. |
| int gsasl_base64_encode (unsigned 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. Returns the number of data bytes stored at the target, or -1 on error. |
| int gsasl_base64_decode (char const * src, unsigned 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. Returns the number of data bytes stored at the target, or -1 on error. |
| void gsasl_hexdump (FILE * fh, const char * buffer, size_t len) | Function |
|
fh: file handle buffer: input byte array len: size of input byte array Print a byte array to given file handle, mostly for debugging purposes. |
| 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 GSASL_OK if output buffer contains the password, GSASL_AUTHENTICATION_ERROR if the user could not be found, or other error code. |
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.
| const char * gsasl_strerror (int err) | Function |
|
err: libgsasl error code Returns a pointer to a statically allocated string containing a description of the error with the error value err. This string can be used to output a diagnostic message to the user. |
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;
}
Simon Josefsson created the library autumn 2002 when he really should have been studying mathematics.
The makefiles, manuals, etc borrowed much from Libgcrypt written by Werner Koch.
Cryptographic functions for some SASL mechanisms uses Libgcrypt written by Werner Koch. The NTLM mechanism uses Libntlm written by Grant Edwards and uses code from Samba written by Andrew Tridgell. The GSSAPI mechanism uses Kerberos written by MIT.
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Each version is given a distinguishing version number. If the Library specifies a version number of this License which applies to it and "any later version", you have the option of following the terms and conditions either of that version or of any later version published by the Free Software Foundation. If the Library does not specify a license version number, you may choose any version ever published by the Free Software Foundation.
If you develop a new library, and you want it to be of the greatest possible use to the public, we recommend making it free software that everyone can redistribute and change. You can do so by permitting redistribution under these terms (or, alternatively, under the terms of the ordinary General Public License).
To apply these terms, attach the following notices to the library. It is
safest to attach them to the start of each source file to most effectively
convey the exclusion of warranty; and each file should have at least the
"copyright" line and a pointer to where the full notice is found.
one line to give the library's name and an idea of what it does. Copyright (C) year name of author This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.
Also add information on how to contact you by electronic and paper mail.
You should also get your employer (if you work as a programmer) or your
school, if any, to sign a "copyright disclaimer" for the library, if
necessary. Here is a sample; alter the names:
Yoyodyne, Inc., hereby disclaims all copyright interest in the library `Frob' (a library for tweaking knobs) written by James Random Hacker. signature of Ty Coon, 1 April 1990 Ty Coon, President of Vice
That's all there is to it!
Copyright © 1989, 1991 Free Software Foundation, Inc. 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed.
The licenses for most software are designed to take away your freedom to share and change it. By contrast, the GNU General Public License is intended to guarantee your freedom to share and change free software--to make sure the software is free for all its users. This General Public License applies to most of the Free Software Foundation's software and to any other program whose authors commit to using it. (Some other Free Software Foundation software is covered by the GNU Library General Public License instead.) You can apply it to your programs, too.
When we speak of free software, we are referring to freedom, not price. Our General Public Licenses are designed to make sure that you have the freedom to distribute copies of free software (and charge for this service if you wish), that you receive source code or can get it if you want it, that you can change the software or use pieces of it in new free programs; and that you know you can do these things.
To protect your rights, we need to make restrictions that forbid anyone to deny you these rights or to ask you to surrender the rights. These restrictions translate to certain responsibilities for you if you distribute copies of the software, or if you modify it.
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We protect your rights with two steps: (1) copyright the software, and (2) offer you this license which gives you legal permission to copy, distribute and/or modify the software.
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The precise terms and conditions for copying, distribution and modification follow.
Activities other than copying, distribution and modification are not covered by this License; they are outside its scope. The act of running the Program is not restricted, and the output from the Program is covered only if its contents constitute a work based on the Program (independent of having been made by running the Program). Whether that is true depends on what the Program does.
You may charge a fee for the physical act of transferring a copy, and you may at your option offer warranty protection in exchange for a fee.
These requirements apply to the modified work as a whole. If identifiable sections of that work are not derived from the Program, and can be reasonably considered independent and separate works in themselves, then this License, and its terms, do not apply to those sections when you distribute them as separate works. But when you distribute the same sections as part of a whole which is a work based on the Program, the distribution of the whole must be on the terms of this License, whose permissions for other licensees extend to the entire whole, and thus to each and every part regardless of who wrote it.
Thus, it is not the intent of this section to claim rights or contest your rights to work written entirely by you; rather, the intent is to exercise the right to control the distribution of derivative or collective works based on the Program.
In addition, mere aggregation of another work not based on the Program with the Program (or with a work based on the Program) on a volume of a storage or distribution medium does not bring the other work under the scope of this License.
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It is not the purpose of this section to induce you to infringe any patents or other property right claims or to contest validity of any such claims; this section has the sole purpose of protecting the integrity of the free software distribution system, which is implemented by public license practices. Many people have made generous contributions to the wide range of software distributed through that system in reliance on consistent application of that system; it is up to the author/donor to decide if he or she is willing to distribute software through any other system and a licensee cannot impose that choice.
This section is intended to make thoroughly clear what is believed to be a consequence of the rest of this License.
Each version is given a distinguishing version number. If the Program specifies a version number of this License which applies to it and "any later version", you have the option of following the terms and conditions either of that version or of any later version published by the Free Software Foundation. If the Program does not specify a version number of this License, you may choose any version ever published by the Free Software Foundation.
If you develop a new program, and you want it to be of the greatest possible use to the public, the best way to achieve this is to make it free software which everyone can redistribute and change under these terms.
To do so, attach the following notices to the program. It is safest
to attach them to the start of each source file to most effectively
convey the exclusion of warranty; and each file should have at least
the "copyright" line and a pointer to where the full notice is found.
one line to give the program's name and a brief idea of what it does. Copyright (C) yyyy name of author This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
Also add information on how to contact you by electronic and paper mail.
If the program is interactive, make it output a short notice like this
when it starts in an interactive mode:
Gnomovision version 69, Copyright (C) 19yy name of author Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type `show w'. This is free software, and you are welcome to redistribute it under certain conditions; type `show c' for details.
The hypothetical commands show w and show c should show
the appropriate parts of the General Public License. Of course, the
commands you use may be called something other than show w and
show c; they could even be mouse-clicks or menu items--whatever
suits your program.
You should also get your employer (if you work as a programmer) or your
school, if any, to sign a "copyright disclaimer" for the program, if
necessary. Here is a sample; alter the names:
Yoyodyne, Inc., hereby disclaims all copyright interest in the program `Gnomovision' (which makes passes at compilers) written by James Hacker. signature of Ty Coon, 1 April 1989 Ty Coon, President of Vice
This General Public License does not permit incorporating your program into proprietary programs. If your program is a subroutine library, you may consider it more useful to permit linking proprietary applications with the library. If this is what you want to do, use the GNU Library General Public License instead of this License.
(: GSSAPI, SECURID, NTLM, DIGEST-MD5, CRAM-MD5, LOGIN, PLAIN, ANONYMOUS, EXTERNAL
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: Callback Functions
gsasl_client_application_data_set: Callback 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_service_get: Callback Functions
gsasl_client_callback_service_set: Callback Functions
gsasl_client_ctx_get: Callback Functions
gsasl_client_finish: Session Functions
gsasl_client_listmech: Global Functions
gsasl_client_start: Session Functions
gsasl_client_step: Session Functions
gsasl_client_step_base64: Session Functions
gsasl_client_suggest_mechanism: Global Functions
gsasl_client_support_p: Global Functions
gsasl_decode: Session Functions
gsasl_done: Global Functions
gsasl_encode: Session Functions
gsasl_hexdump: Utilities
gsasl_init: Global Functions
gsasl_md5pwd_get_password: Utilities
gsasl_server_application_data_get: Callback Functions
gsasl_server_application_data_set: Callback 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: Callback Functions
gsasl_server_finish: Session Functions
gsasl_server_listmech: Global Functions
gsasl_server_start: Session Functions
gsasl_server_step: Session Functions
gsasl_server_step_base64: Session Functions
gsasl_server_suggest_mechanism: Global Functions
gsasl_server_support_p: Global Functions
gsasl_strerror: Error strings
The text is a lightly adapted version of the introduction section from RFC 2222 by John G. Myers, copyright 1997 by The Internet Society.