13.3 Example 3

     /* client-mech.c --- Example SASL client, with a choice of mechanism to use.
      * Copyright (C) 2004-2012 Simon Josefsson
      *
      * This file is part of GNU SASL.
      *
      * 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 3 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, see <http://www.gnu.org/licenses/>.
      *
      */
     
     #include <config.h>
     #include <stdarg.h>
     #include <stdio.h>
     #include <stdlib.h>
     #include <string.h>
     
     #include <gsasl.h>
     
     static void
     client_authenticate (Gsasl_session * session)
     {
       char buf[BUFSIZ] = "";
       char *p;
       int rc;
     
       /* This loop mimics a protocol where the server send data first. */
     
       do
         {
           printf ("Input base64 encoded data from server:\n");
           p = fgets (buf, sizeof (buf) - 1, stdin);
           if (p == NULL)
     	{
     	  perror ("fgets");
     	  return;
     	}
           if (buf[strlen (buf) - 1] == '\n')
             buf[strlen (buf) - 1] = '\0';
     
           rc = gsasl_step64 (session, buf, &p);
     
           if (rc == GSASL_NEEDS_MORE || rc == GSASL_OK)
             {
               printf ("Output:\n%s\n", p);
               gsasl_free (p);
             }
         }
       while (rc == GSASL_NEEDS_MORE);
     
       printf ("\n");
     
       if (rc != GSASL_OK)
         {
           printf ("Authentication error (%d): %s\n", rc, gsasl_strerror (rc));
           return;
         }
     
       /* The client is done.  Here you would typically check if the server
          let the client in.  If not, you could try again. */
     
       printf ("If server accepted us, we're done.\n");
     }
     
     static const char *
     client_mechanism (Gsasl * ctx)
     {
       static char mech[GSASL_MAX_MECHANISM_SIZE + 1] = "";
       char mechlist[BUFSIZ] = "";
       const char *suggestion;
       char *p;
     
       printf ("Enter list of server supported mechanisms, separate by SPC:\n");
       p = fgets (mechlist, sizeof (mechlist) - 1, stdin);
       if (p == NULL)
         {
           perror ("fgets");
           return NULL;
         }
     
       suggestion = gsasl_client_suggest_mechanism (ctx, mechlist);
       if (suggestion)
         printf ("Library suggests use of `%s'.\n", suggestion);
     
       printf ("Enter mechanism to use:\n");
       p = fgets (mech, sizeof (mech) - 1, stdin);
       if (p == NULL)
         {
           perror ("fgets");
           return NULL;
         }
     
       mech[strlen (mech) - 1] = '\0';
     
       return mech;
     }
     
     static void
     client (Gsasl * ctx)
     {
       Gsasl_session *session;
       const char *mech;
       int rc;
     
       /* Find out which mechanism to use. */
       mech = client_mechanism (ctx);
     
       /* Create new authentication session. */
       if ((rc = gsasl_client_start (ctx, mech, &session)) != GSASL_OK)
         {
           printf ("Cannot initialize client (%d): %s\n", rc, gsasl_strerror (rc));
           return;
         }
     
       /* Set username and password in session handle.  This info will be
          lost when this session is deallocated below.  */
       gsasl_property_set (session, GSASL_AUTHID, "jas");
       gsasl_property_set (session, GSASL_PASSWORD, "secret");
     
       /* Do it. */
       client_authenticate (session);
     
       /* Cleanup. */
       gsasl_finish (session);
     }
     
     int
     main (int argc, char *argv[])
     {
       Gsasl *ctx = NULL;
       int rc;
     
       /* Initialize library. */
       if ((rc = gsasl_init (&ctx)) != GSASL_OK)
         {
           printf ("Cannot initialize libgsasl (%d): %s", rc, gsasl_strerror (rc));
           return 1;
         }
     
       /* Do it. */
       client (ctx);
     
       /* Cleanup. */
       gsasl_done (ctx);
     
       return 0;
     }