@deftypefun {void} {gnutls_srp_set_client_credentials_function} (gnutls_srp_client_credentials_t         @var{cred}, gnutls_srp_client_credentials_function         * @var{func})
@var{cred}: is a @code{gnutls_srp_server_credentials_t}  type.

@var{func}: is the callback function

This function can be used to set a callback to retrieve the
username and password for client SRP authentication.  The
callback's function form is:

int (*callback)(gnutls_session_t, char** username, char**password);

The  @code{username} and  @code{password} must be allocated using
@code{gnutls_malloc()} .

The  @code{username} should be an ASCII string or UTF-8
string. In case of a UTF-8 string it is recommended to be following
the PRECIS framework for usernames (rfc8265). The password can
be in ASCII format, or normalized using @code{gnutls_utf8_password_normalize()} .

The callback function will be called once per handshake before the
initial hello message is sent.

The callback should not return a negative error code the second
time called, since the handshake procedure will be aborted.

The callback function should return 0 on success.
-1 indicates an error.
@end deftypefun