/*
 * Copyright (c) 1997 - 2000 Kungliga Tekniska Högskolan
 * (Royal Institute of Technology, Stockholm, Sweden). 
 * All rights reserved. 
 *
 * Redistribution and use in source and binary forms, with or without 
 * modification, are permitted provided that the following conditions 
 * are met: 
 *
 * 1. Redistributions of source code must retain the above copyright 
 *    notice, this list of conditions and the following disclaimer. 
 *
 * 2. Redistributions in binary form must reproduce the above copyright 
 *    notice, this list of conditions and the following disclaimer in the 
 *    documentation and/or other materials provided with the distribution. 
 *
 * 3. Neither the name of the Institute nor the names of its contributors 
 *    may be used to endorse or promote products derived from this software 
 *    without specific prior written permission. 
 *
 * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND 
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE 
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 
 * SUCH DAMAGE. 
 */

#include "gssapi_locl.h"

RCSID("$Id: verify_mic.c,v 1.9 2000/01/25 23:14:47 assar Exp $");

OM_uint32 gss_verify_mic
           (OM_uint32 * minor_status,
            const gss_ctx_id_t context_handle,
            const gss_buffer_t message_buffer,
            const gss_buffer_t token_buffer,
            gss_qop_t * qop_state
	    )
{
  u_char *p;
  MD5_CTX md5;
  u_char hash[16], seq_data[8];
  des_key_schedule schedule;
  des_cblock key;
  des_cblock zero;
  int32_t seq_number;
  OM_uint32 ret;

  p = token_buffer->value;
  ret = gssapi_krb5_verify_header (&p,
				   token_buffer->length,
				   "\x01\x01");
  if (ret)
      return ret;

  if (memcmp(p, "\x00\x00", 2) != 0)
      return GSS_S_BAD_SIG;
  p += 2;
  if (memcmp (p, "\xff\xff\xff\xff", 4) != 0)
    return GSS_S_BAD_MIC;
  p += 4;
  p += 16;

  /* verify checksum */
  MD5Init (&md5);
  MD5Update (&md5, p - 24, 8);
  MD5Update (&md5, message_buffer->value,
	     message_buffer->length);
  MD5Final (hash, &md5);

  memset (&zero, 0, sizeof(zero));
#if 0
  memcpy (&key, context_handle->auth_context->key.keyvalue.data,
	  sizeof(key));
#endif
  memcpy (&key, context_handle->auth_context->remote_subkey->keyvalue.data,
	  sizeof(key));

  des_set_key (&key, schedule);
  des_cbc_cksum ((const void *)hash, (void *)hash, sizeof(hash),
		 schedule, &zero);
  if (memcmp (p - 8, hash, 8) != 0) {
    memset (key, 0, sizeof(key));
    memset (schedule, 0, sizeof(schedule));
    return GSS_S_BAD_MIC;
  }

  /* verify sequence number */
  
  krb5_auth_getremoteseqnumber (gssapi_krb5_context,
				context_handle->auth_context,
				&seq_number);
  seq_data[0] = (seq_number >> 0)  & 0xFF;
  seq_data[1] = (seq_number >> 8)  & 0xFF;
  seq_data[2] = (seq_number >> 16) & 0xFF;
  seq_data[3] = (seq_number >> 24) & 0xFF;
  memset (seq_data + 4,
	  (context_handle->more_flags & LOCAL) ? 0xFF : 0,
	  4);

  p -= 16;
  des_set_key (&key, schedule);
  des_cbc_encrypt ((const void *)p, (void *)p, 8,
		   schedule, (des_cblock *)hash, DES_DECRYPT);

  memset (key, 0, sizeof(key));
  memset (schedule, 0, sizeof(schedule));

  if (memcmp (p, seq_data, 8) != 0) {
    return GSS_S_BAD_MIC;
  }

  krb5_auth_setremoteseqnumber (gssapi_krb5_context,
				context_handle->auth_context,
				++seq_number);

  return GSS_S_COMPLETE;
}