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