plain/server.c

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/* server.c --- SASL mechanism PLAIN as defined in RFC 2595, server side.
 * Copyright (C) 2002-2024 Simon Josefsson
 *
 * This file is part of GNU SASL Library.
 *
 * GNU SASL Library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public License
 * as published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * GNU SASL Library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with GNU SASL Library; if not, write to the Free
 * Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA 02110-1301, USA.
 *
 */
 
#include <config.h>
 
/* Get specification. */
#include "plain.h"
 
/* Get memcpy, memchr, strlen. */
#include <string.h>
 
/* Get malloc, free. */
#include <stdlib.h>
 
int
_gsasl_plain_server_step (Gsasl_session *sctx,
                          void *mech_data _GL_UNUSED,
                          const char *input, size_t input_len,
                          char **output, size_t *output_len)
{
  const char *authzidptr = input;
  char *authidptr = NULL;
  char *passwordptr = NULL;
  char *passwdz = NULL, *passprep = NULL, *authidprep = NULL;
  int res;
 
  *output_len = 0;
  *output = NULL;
 
  if (input_len == 0)
    return GSASL_NEEDS_MORE;
 
  /* Parse input. */
  {
    size_t tmplen;
 
    authidptr = memchr (input, 0, input_len - 1);
    if (authidptr)
      {
        authidptr++;
        passwordptr = memchr (authidptr, 0, input_len - strlen (input) - 1);
        if (passwordptr)
          passwordptr++;
        else
          return GSASL_MECHANISM_PARSE_ERROR;
      }
    else
      return GSASL_MECHANISM_PARSE_ERROR;
 
    /* As the NUL (U+0000) character is used as a deliminator, the NUL
       (U+0000) character MUST NOT appear in authzid, authcid, or passwd
       productions. */
    tmplen = input_len - (size_t) (passwordptr - input);
    if (memchr (passwordptr, 0, tmplen))
      return GSASL_MECHANISM_PARSE_ERROR;
  }
 
  /* Store authid, after preparing it... */
  {
    res = gsasl_saslprep (authidptr, GSASL_ALLOW_UNASSIGNED,
                          &authidprep, NULL);
    if (res != GSASL_OK)
      return res;
 
    res = gsasl_property_set (sctx, GSASL_AUTHID, authidprep);
    if (res != GSASL_OK)
      return res;
 
    /* Store authzid, if absent, use SASLprep(authcid). */
    if (*authzidptr == '\0')
      res = gsasl_property_set (sctx, GSASL_AUTHZID, authidprep);
    else
      res = gsasl_property_set (sctx, GSASL_AUTHZID, authzidptr);
    if (res != GSASL_OK)
      return res;
 
    free (authidprep);
  }
 
  /* Store passwd, after preparing it... */
  {
    size_t passwdzlen = input_len - (size_t) (passwordptr - input);
 
    /* Need to zero terminate password... */
    passwdz = malloc (passwdzlen + 1);
    if (passwdz == NULL)
      return GSASL_MALLOC_ERROR;
    memcpy (passwdz, passwordptr, passwdzlen);
    passwdz[passwdzlen] = '\0';
 
    res = gsasl_saslprep (passwdz, GSASL_ALLOW_UNASSIGNED, &passprep, NULL);
    free (passwdz);
    if (res != GSASL_OK)
      return res;
 
    res = gsasl_property_set (sctx, GSASL_PASSWORD, passprep);
    if (res != GSASL_OK)
      return res;
  }
 
  /* Authorization.  Let application verify credentials internally,
     but fall back to deal with it locally... */
  res = gsasl_callback (NULL, sctx, GSASL_VALIDATE_SIMPLE);
  if (res == GSASL_NO_CALLBACK)
    {
      const char *key;
      char *normkey;
 
      gsasl_property_free (sctx, GSASL_PASSWORD);
 
      /* The following will invoke a GSASL_PASSWORD callback. */
      key = gsasl_property_get (sctx, GSASL_PASSWORD);
      if (!key)
        {
          free (passprep);
          return GSASL_NO_PASSWORD;
        }
 
      /* Unassigned code points are not permitted. */
      res = gsasl_saslprep (key, 0, &normkey, NULL);
      if (res != GSASL_OK)
        {
          free (passprep);
          return res;
        }
 
      if (strcmp (normkey, passprep) == 0)
        res = GSASL_OK;
      else
        res = GSASL_AUTHENTICATION_ERROR;
 
      free (normkey);
    }
  free (passprep);
 
  return res;
}