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13.2 Example 2

/* client-serverfirst.c --- Example SASL client, where server send data first.
 * Copyright (C) 2004-2019 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 void
client (Gsasl * ctx)
{
  Gsasl_session *session;
  const char *mech = "CRAM-MD5";
  int rc;

  /* 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;
}

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