lib/gssapi/krb5/unwrap.c

   1 /*
   2  * Copyright (c) 1997, 1998 Kungliga Tekniska Högskolan
   3  * (Royal Institute of Technology, Stockholm, Sweden).
   4  * All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  *
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  *
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  *
  17  * 3. All advertising materials mentioning features or use of this software
  18  *    must display the following acknowledgement:
  19  *      This product includes software developed by Kungliga Tekniska
  20  *      Högskolan and its contributors.
  21  *
  22  * 4. Neither the name of the Institute nor the names of its contributors
  23  *    may be used to endorse or promote products derived from this software
  24  *    without specific prior written permission.
  25  *
  26  * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
  27  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  28  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  29  * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
  30  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  31  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  32  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  33  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  34  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  35  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  36  * SUCH DAMAGE.
  37  */
  38
  39 #include "gssapi_locl.h"
  40
  41 RCSID("$Id$");
  42
  43 OM_uint32
  44 gss_krb5_getsomekey(const gss_ctx_id_t context_handle,
  45                     des_cblock *key)
  46 {
  47     /* XXX this is ugly, and probably incorrect... */
  48     krb5_keyblock *skey;
  49     krb5_auth_con_getlocalsubkey(gssapi_krb5_context,
  50                                  context_handle->auth_context,
  51                                  &skey);
  52     if(skey == NULL)
  53         krb5_auth_con_getremotesubkey(gssapi_krb5_context,
  54                                       context_handle->auth_context,
  55                                       &skey);
  56     if(skey == NULL)
  57         krb5_auth_con_getkey(gssapi_krb5_context,
  58                              context_handle->auth_context,
  59                              &skey);
  60     if(skey == NULL)
  61         return GSS_S_FAILURE;
  62     memcpy(key, skey->keyvalue.data, sizeof(*key));
  63     krb5_free_keyblock(gssapi_krb5_context, skey);
  64     return 0;
  65 }
  66
  67 OM_uint32 gss_unwrap
  68            (OM_uint32 * minor_status,
  69             const gss_ctx_id_t context_handle,
  70             const gss_buffer_t input_message_buffer,
  71             gss_buffer_t output_message_buffer,
  72             int * conf_state,
  73             gss_qop_t * qop_state
  74            )
  75 {
  76   u_char *p, *pad;
  77   size_t len;
  78   struct md5 md5;
  79   u_char hash[16], seq_data[8];
  80   des_key_schedule schedule;
  81   des_cblock key;
  82   des_cblock zero;
  83   int i;
  84   int32_t seq_number;
  85   size_t padlength;
  86   OM_uint32 ret;
  87   int cstate;
  88
  89   p = input_message_buffer->value;
  90   ret = gssapi_krb5_verify_header (&p,
  91                                    input_message_buffer->length,
  92                                    "\x02\x01");
  93   if (ret)
  94       return ret;
  95
  96   if (memcmp (p, "\x00\x00", 2) != 0)
  97     return GSS_S_BAD_SIG;
  98   p += 2;
  99   if (memcmp (p, "\x00\x00", 2) == 0) {
 100       cstate = 1;
 101   } else if (memcmp (p, "\xFF\xFF", 2) == 0) {
 102       cstate = 0;
 103   } else
 104       return GSS_S_BAD_MIC;
 105   p += 2;
 106   if(conf_state != NULL)
 107       *conf_state = cstate;
 108   if (memcmp (p, "\xff\xff", 2) != 0)
 109     return GSS_S_DEFECTIVE_TOKEN;
 110   p += 2;
 111   p += 16;
 112
 113   len = p - (u_char *)input_message_buffer->value;
 114
 115   if(cstate) {
 116       /* decrypt data */
 117       gss_krb5_getsomekey(context_handle, &key);
 118       for (i = 0; i < sizeof(key); ++i)
 119           key[i] ^= 0xf0;
 120       des_set_key (&key, schedule);
 121       memset (&zero, 0, sizeof(zero));
 122       des_cbc_encrypt ((des_cblock *)p,
 123                        (des_cblock *)p,
 124                        input_message_buffer->length - len,
 125                        schedule,
 126                        &zero,
 127                        DES_DECRYPT);
 128
 129       memset (key, 0, sizeof(key));
 130       memset (schedule, 0, sizeof(schedule));
 131   }
 132   /* check pad */
 133
 134   pad = (u_char *)input_message_buffer->value + input_message_buffer->length - 1;
 135   padlength = *pad;
 136
 137   for (i = padlength; i > 0 && *pad == padlength; i--, pad--)
 138     ;
 139   if (i != 0)
 140     return GSS_S_BAD_MIC;
 141
 142   md5_init (&md5);
 143   md5_update (&md5, p - 24, 8);
 144   md5_update (&md5, p, input_message_buffer->length - len);
 145   md5_finito (&md5, hash);
 146
 147   memset (&zero, 0, sizeof(zero));
 148   gss_krb5_getsomekey(context_handle, &key);
 149   des_set_key (&key, schedule);
 150   des_cbc_cksum ((des_cblock *)hash,
 151                  (des_cblock *)hash, sizeof(hash), schedule, &zero);
 152   if (memcmp (p - 8, hash, 8) != 0)
 153     return GSS_S_BAD_MIC;
 154
 155   /* verify sequence number */
 156
 157   krb5_auth_getremoteseqnumber (gssapi_krb5_context,
 158                                 context_handle->auth_context,
 159                                 &seq_number);
 160   seq_data[0] = (seq_number >> 0)  & 0xFF;
 161   seq_data[1] = (seq_number >> 8)  & 0xFF;
 162   seq_data[2] = (seq_number >> 16) & 0xFF;
 163   seq_data[3] = (seq_number >> 24) & 0xFF;
 164   memset (seq_data + 4,
 165           (context_handle->more_flags & LOCAL) ? 0xFF : 0,
 166           4);
 167
 168   p -= 16;
 169   des_set_key (&key, schedule);
 170   des_cbc_encrypt ((des_cblock *)p, (des_cblock *)p, 8,
 171                    schedule, (des_cblock *)hash, DES_DECRYPT);
 172
 173   memset (key, 0, sizeof(key));
 174   memset (schedule, 0, sizeof(schedule));
 175
 176   if (memcmp (p, seq_data, 8) != 0) {
 177     return GSS_S_BAD_MIC;
 178   }
 179
 180   krb5_auth_setremoteseqnumber (gssapi_krb5_context,
 181                                 context_handle->auth_context,
 182                                 ++seq_number);
 183
 184   /* copy out data */
 185
 186   output_message_buffer->length = input_message_buffer->length
 187     - len - 8 - padlength;
 188   output_message_buffer->value  = malloc(output_message_buffer->length);
 189   if(output_message_buffer->length != 0 && output_message_buffer->value == NULL)
 190       return GSS_S_FAILURE;
 191   memcpy (output_message_buffer->value,
 192           p + 24,
 193           output_message_buffer->length);
 194   return GSS_S_COMPLETE;
 195 }