.. saslman:: sasl_client_start(3)

.. _sasl-reference-manpages-library-sasl_client_start:


===========================================================
**sasl_client_start** - Begin an authentication negotiation
===========================================================

Synopsis
========

.. code-block:: C

    #include <sasl/sasl.h>

    int sasl_client_start(sasl_conn_t * conn,
            const char * mechlist,
            sasl_interact_t ** prompt_need,
            const char ** clientout,
            unsigned * clientoutlen,
            const char ** mech);

Description
===========

.. c:function::     int sasl_client_start(sasl_conn_t * conn,
        const char * mechlist,
        sasl_interact_t ** prompt_need,
        const char ** clientout,
        unsigned * clientoutlen,
        const char ** mech);

    **sasl_client_start()** selects a mechanism for authentication and starts the
    authentication session. The mechlist is the list of mechanisms the client
    might like to use. The mech‐ anisms in the list are not necessarily  supported
    by  the client  or  even  valid. SASL determines which of these to use based
    upon the security preferences specified earlier. The  list  of mechanisms is
    typically a list of mechanisms the server supports acquired from a capability
    request.

    If :c:macro:`SASL_INTERACT` is returned the library needs some values to  be
    filled  in  before it can proceed. The `prompt_need` structure will be filled in
    with requests. The application should  fulfill  these requests and call
    sasl_client_start again with identical parameters (the `prompt_need` parameter
    will  be  the  same pointer as before but filled in by the application).

    :param conn: is the SASL connection context

    :param mechlist: is a list of mechanisms the server has available.
        Punctuation is ignored.

    :param prompt_need:  is filled in with a list of prompts needed to
        continue (if necessary).

    :param clientout: is created. It is  the  initial
        client  response  to  send to the server. It is the job of
        the client to send it over the network to the server.  Any
        protocol  specific encoding (such as base64 encoding) necessary
        needs to be done by the client.

        If the protocol lacks client‐send‐first  capability,  then
        set clientout to NULL.

        If  there  is no initial client‐send, then \*clientout will
        be set to NULL on return.

    :param clientoutlen: length of `clientout`.

    :param mech: contains the name of the chosen  SASL
        mechanism  (on success)

Return Value
============

SASL  callback  functions should return SASL return codes.
See sasl.h for a complete list. :c:macro:`SASL_CONTINUE` indicates success
and that there are more steps needed in the authentication.

Other return codes indicate errors and should either be handled or the authentication
session should be quit.

See Also
========

:rfc:`4422`,:saslman:`sasl(3)`, :saslman:`sasl_callbacks(3)`,
:saslman:`sasl_client_init(3)`, :saslman:`sasl_client_new(3)`,
:saslman:`sasl_client_step(3)`, :saslman:`sasl_errors(3)`