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# sasl_server_start - Begin an authentication negotiation

## Synopsis

    #include <sasl/sasl.h>

    int sasl_server_start(sasl_conn_t * conn,
                 const char * mech,
                 const char * clientin,
                 unsigned clientinlen,
                 const char ** serverout,
                 unsigned * serveroutlen);

## Description

int sasl_server_start(sasl_conn_t * conn,
const char * mech,
const char * clientin,
unsigned * clientinlen,
const char ** serverout,
unsigned * serveroutlen);

  sasl_server_start() begins the authentication with the mechanism specified with mech. This fails if the mechanism is not supported.

  Parameters

    - conn – is the SASL connection context

    - mech – is the mechanism name that the client requested

    - clientin – is the client initial response, NULL if the protocol lacks support for client‐send‐first or if the other end did not have an initial send. Note that no initial client send is distinct from an initial send of a null string, and the protocol MUST account for this difference.

    - clientinlen – is the length of initial response

    - serverout – is created by the plugin library. It is the initial server response to send to the client. This is allocated/freed by the library and it is the job of the client to send it over the network to the server. Also protocol specific encoding (such as base64 encoding) must needs to be done by the server.

    - serveroutlen – is set to the length of initial server challenge

## Return Value

SASL callback functions should return SASL return codes. See sasl.h for a complete list. `SASL_OK` is returned if the authentication is complete and the user is authenticated. `SASL_CONTINUE` is returned if one or more steps are still required in the authentication.

All other return values indicate errors and should be handled or the authentication session should be quit.

## See Also

RFC 4422,:saslman:sasl(3), sasl_server_init(3), sasl_server_new(3), sasl_server_step(3), sasl_errors(3)