lib/gssapi/krb5/unwrap.c

   1 /*
   2  * Copyright (c) 1997 - 2002 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_get_remotekey(const gss_ctx_id_t context_handle,
  40                        krb5_keyblock **key)
  41 {
  42     krb5_keyblock *skey;
  43
  44     krb5_auth_con_getremotesubkey(gssapi_krb5_context,
  45                                   context_handle->auth_context,
  46                                   &skey);
  47     if(skey == NULL)
  48         krb5_auth_con_getlocalsubkey(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     *key = skey;
  58     return 0;
  59 }
  60
  61 static OM_uint32
  62 unwrap_des
  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             krb5_keyblock *key
  70            )
  71 {
  72   u_char *p, *pad;
  73   size_t len;
  74   MD5_CTX md5;
  75   u_char hash[16], seq_data[8];
  76   des_key_schedule schedule;
  77   des_cblock deskey;
  78   des_cblock zero;
  79   int i;
  80   int32_t seq_number;
  81   size_t padlength;
  82   OM_uint32 ret;
  83   int cstate;
  84
  85   p = input_message_buffer->value;
  86   ret = gssapi_krb5_verify_header (&p,
  87                                    input_message_buffer->length,
  88                                    "\x02\x01");
  89   if (ret) {
  90       *minor_status = 0;
  91       return ret;
  92   }
  93
  94   if (memcmp (p, "\x00\x00", 2) != 0)
  95     return GSS_S_BAD_SIG;
  96   p += 2;
  97   if (memcmp (p, "\x00\x00", 2) == 0) {
  98       cstate = 1;
  99   } else if (memcmp (p, "\xFF\xFF", 2) == 0) {
 100       cstate = 0;
 101   } else
 102       return GSS_S_BAD_MIC;
 103   p += 2;
 104   if(conf_state != NULL)
 105       *conf_state = cstate;
 106   if (memcmp (p, "\xff\xff", 2) != 0)
 107     return GSS_S_DEFECTIVE_TOKEN;
 108   p += 2;
 109   p += 16;
 110
 111   len = p - (u_char *)input_message_buffer->value;
 112
 113   if(cstate) {
 114       /* decrypt data */
 115       memcpy (&deskey, key->keyvalue.data, sizeof(deskey));
 116
 117       for (i = 0; i < sizeof(deskey); ++i)
 118           deskey[i] ^= 0xf0;
 119       des_set_key (&deskey, schedule);
 120       memset (&zero, 0, sizeof(zero));
 121       des_cbc_encrypt ((void *)p,
 122                        (void *)p,
 123                        input_message_buffer->length - len,
 124                        schedule,
 125                        &zero,
 126                        DES_DECRYPT);
 127
 128       memset (deskey, 0, sizeof(deskey));
 129       memset (schedule, 0, sizeof(schedule));
 130   }
 131   /* check pad */
 132
 133   pad = (u_char *)input_message_buffer->value + input_message_buffer->length - 1;
 134   padlength = *pad;
 135
 136   for (i = padlength; i > 0 && *pad == padlength; i--, pad--)
 137     ;
 138   if (i != 0)
 139     return GSS_S_BAD_MIC;
 140
 141   MD5_Init (&md5);
 142   MD5_Update (&md5, p - 24, 8);
 143   MD5_Update (&md5, p, input_message_buffer->length - len);
 144   MD5_Final (hash, &md5);
 145
 146   memset (&zero, 0, sizeof(zero));
 147   memcpy (&deskey, key->keyvalue.data, sizeof(deskey));
 148   des_set_key (&deskey, schedule);
 149   des_cbc_cksum ((void *)hash, (void *)hash, sizeof(hash),
 150                  schedule, &zero);
 151   if (memcmp (p - 8, hash, 8) != 0)
 152     return GSS_S_BAD_MIC;
 153
 154   /* verify sequence number */
 155
 156   krb5_auth_getremoteseqnumber (gssapi_krb5_context,
 157                                 context_handle->auth_context,
 158                                 &seq_number);
 159   seq_data[0] = (seq_number >> 0)  & 0xFF;
 160   seq_data[1] = (seq_number >> 8)  & 0xFF;
 161   seq_data[2] = (seq_number >> 16) & 0xFF;
 162   seq_data[3] = (seq_number >> 24) & 0xFF;
 163   memset (seq_data + 4,
 164           (context_handle->more_flags & LOCAL) ? 0xFF : 0,
 165           4);
 166
 167   p -= 16;
 168   des_set_key (&deskey, schedule);
 169   des_cbc_encrypt ((void *)p, (void *)p, 8,
 170                    schedule, (des_cblock *)hash, DES_DECRYPT);
 171
 172   memset (deskey, 0, sizeof(deskey));
 173   memset (schedule, 0, sizeof(schedule));
 174
 175   if (memcmp (p, seq_data, 8) != 0) {
 176     return GSS_S_BAD_MIC;
 177   }
 178
 179   krb5_auth_con_setremoteseqnumber (gssapi_krb5_context,
 180                                 context_handle->auth_context,
 181                                 ++seq_number);
 182
 183   /* copy out data */
 184
 185   output_message_buffer->length = input_message_buffer->length
 186     - len - padlength - 8;
 187   output_message_buffer->value  = malloc(output_message_buffer->length);
 188   if(output_message_buffer->length != 0 && output_message_buffer->value == NULL)
 189       return GSS_S_FAILURE;
 190   memcpy (output_message_buffer->value,
 191           p + 24,
 192           output_message_buffer->length);
 193   return GSS_S_COMPLETE;
 194 }
 195
 196 static OM_uint32
 197 unwrap_des3
 198            (OM_uint32 * minor_status,
 199             const gss_ctx_id_t context_handle,
 200             const gss_buffer_t input_message_buffer,
 201             gss_buffer_t output_message_buffer,
 202             int * conf_state,
 203             gss_qop_t * qop_state,
 204             krb5_keyblock *key
 205            )
 206 {
 207   u_char *p, *pad;
 208   size_t len;
 209   u_char seq[8];
 210   krb5_data seq_data;
 211   u_char cksum[20];
 212   int i;
 213   int32_t seq_number;
 214   size_t padlength;
 215   OM_uint32 ret;
 216   int cstate;
 217   krb5_crypto crypto;
 218   Checksum csum;
 219   int cmp;
 220
 221   p = input_message_buffer->value;
 222   ret = gssapi_krb5_verify_header (&p,
 223                                    input_message_buffer->length,
 224                                    "\x02\x01");
 225   if (ret) {
 226       *minor_status = 0;
 227       return ret;
 228   }
 229
 230   if (memcmp (p, "\x04\x00", 2) != 0) /* HMAC SHA1 DES3_KD */
 231     return GSS_S_BAD_SIG;
 232   p += 2;
 233   if (memcmp (p, "\x02\x00", 2) == 0) {
 234     cstate = 1;
 235   } else if (memcmp (p, "\xff\xff", 2) == 0) {
 236     cstate = 0;
 237   } else
 238     return GSS_S_BAD_MIC;
 239   p += 2;
 240   if(conf_state != NULL)
 241     *conf_state = cstate;
 242   if (memcmp (p, "\xff\xff", 2) != 0)
 243     return GSS_S_DEFECTIVE_TOKEN;
 244   p += 2;
 245   p += 28;
 246
 247   len = p - (u_char *)input_message_buffer->value;
 248
 249   if(cstate) {
 250       /* decrypt data */
 251       krb5_data tmp;
 252
 253       ret = krb5_crypto_init(gssapi_krb5_context, key,
 254                              ETYPE_DES3_CBC_NONE, &crypto);
 255       if (ret) {
 256           gssapi_krb5_set_error_string ();
 257           *minor_status = ret;
 258           return GSS_S_FAILURE;
 259       }
 260       ret = krb5_decrypt(gssapi_krb5_context, crypto, KRB5_KU_USAGE_SEAL,
 261                          p, input_message_buffer->length - len, &tmp);
 262       krb5_crypto_destroy(gssapi_krb5_context, crypto);
 263       if (ret) {
 264           gssapi_krb5_set_error_string ();
 265           *minor_status = ret;
 266           return GSS_S_FAILURE;
 267       }
 268       assert (tmp.length == input_message_buffer->length - len);
 269
 270       memcpy (p, tmp.data, tmp.length);
 271       krb5_data_free(&tmp);
 272   }
 273   /* check pad */
 274
 275   pad = (u_char *)input_message_buffer->value + input_message_buffer->length - 1;
 276   padlength = *pad;
 277
 278   for (i = padlength; i > 0 && *pad == padlength; i--, pad--)
 279     ;
 280   if (i != 0)
 281     return GSS_S_BAD_MIC;
 282
 283   /* verify sequence number */
 284
 285   krb5_auth_getremoteseqnumber (gssapi_krb5_context,
 286                                 context_handle->auth_context,
 287                                 &seq_number);
 288   seq[0] = (seq_number >> 0)  & 0xFF;
 289   seq[1] = (seq_number >> 8)  & 0xFF;
 290   seq[2] = (seq_number >> 16) & 0xFF;
 291   seq[3] = (seq_number >> 24) & 0xFF;
 292   memset (seq + 4,
 293           (context_handle->more_flags & LOCAL) ? 0xFF : 0,
 294           4);
 295
 296   p -= 28;
 297
 298   ret = krb5_crypto_init(gssapi_krb5_context, key,
 299                          ETYPE_DES3_CBC_NONE, &crypto);
 300   if (ret) {
 301       gssapi_krb5_set_error_string ();
 302       *minor_status = ret;
 303       return GSS_S_FAILURE;
 304   }
 305   {
 306       des_cblock ivec;
 307
 308       memcpy(&ivec, p + 8, 8);
 309       ret = krb5_decrypt_ivec (gssapi_krb5_context,
 310                                crypto,
 311                                KRB5_KU_USAGE_SEQ,
 312                                p, 8, &seq_data,
 313                                &ivec);
 314   }
 315   krb5_crypto_destroy (gssapi_krb5_context, crypto);
 316   if (ret) {
 317       gssapi_krb5_set_error_string ();
 318       *minor_status = ret;
 319       return GSS_S_FAILURE;
 320   }
 321   if (seq_data.length != 8) {
 322       krb5_data_free (&seq_data);
 323       return GSS_S_BAD_MIC;
 324   }
 325
 326   cmp = memcmp (seq, seq_data.data, seq_data.length);
 327   krb5_data_free (&seq_data);
 328   if (cmp != 0) {
 329       return GSS_S_BAD_MIC;
 330   }
 331
 332   krb5_auth_con_setremoteseqnumber (gssapi_krb5_context,
 333                                 context_handle->auth_context,
 334                                 ++seq_number);
 335
 336   /* verify checksum */
 337
 338   memcpy (cksum, p + 8, 20);
 339
 340   memcpy (p + 20, p - 8, 8);
 341
 342   csum.cksumtype = CKSUMTYPE_HMAC_SHA1_DES3;
 343   csum.checksum.length = 20;
 344   csum.checksum.data   = cksum;
 345
 346   ret = krb5_crypto_init(gssapi_krb5_context, key, 0, &crypto);
 347   if (ret) {
 348       gssapi_krb5_set_error_string ();
 349       *minor_status = ret;
 350       return GSS_S_FAILURE;
 351   }
 352
 353   ret = krb5_verify_checksum (gssapi_krb5_context, crypto,
 354                               KRB5_KU_USAGE_SIGN,
 355                               p + 20,
 356                               input_message_buffer->length - len + 8,
 357                               &csum);
 358   krb5_crypto_destroy (gssapi_krb5_context, crypto);
 359   if (ret) {
 360       gssapi_krb5_set_error_string ();
 361       *minor_status = ret;
 362       return GSS_S_FAILURE;
 363   }
 364
 365   /* copy out data */
 366
 367   output_message_buffer->length = input_message_buffer->length
 368     - len - padlength - 8;
 369   output_message_buffer->value  = malloc(output_message_buffer->length);
 370   if(output_message_buffer->length != 0 && output_message_buffer->value == NULL)
 371       return GSS_S_FAILURE;
 372   memcpy (output_message_buffer->value,
 373           p + 36,
 374           output_message_buffer->length);
 375   return GSS_S_COMPLETE;
 376 }
 377
 378 OM_uint32 gss_unwrap
 379            (OM_uint32 * minor_status,
 380             const gss_ctx_id_t context_handle,
 381             const gss_buffer_t input_message_buffer,
 382             gss_buffer_t output_message_buffer,
 383             int * conf_state,
 384             gss_qop_t * qop_state
 385            )
 386 {
 387   krb5_keyblock *key;
 388   OM_uint32 ret;
 389   krb5_keytype keytype;
 390
 391   if (qop_state != NULL)
 392       *qop_state = GSS_C_QOP_DEFAULT;
 393   ret = gss_krb5_get_remotekey(context_handle, &key);
 394   if (ret) {
 395       gssapi_krb5_set_error_string ();
 396       *minor_status = ret;
 397       return GSS_S_FAILURE;
 398   }
 399   krb5_enctype_to_keytype (gssapi_krb5_context, key->keytype, &keytype);
 400
 401   switch (keytype) {
 402   case KEYTYPE_DES :
 403       ret = unwrap_des (minor_status, context_handle,
 404                         input_message_buffer, output_message_buffer,
 405                         conf_state, qop_state, key);
 406       break;
 407   case KEYTYPE_DES3 :
 408       ret = unwrap_des3 (minor_status, context_handle,
 409                          input_message_buffer, output_message_buffer,
 410                          conf_state, qop_state, key);
 411       break;
 412   default :
 413       *minor_status = KRB5_PROG_ETYPE_NOSUPP;
 414       ret = GSS_S_FAILURE;
 415       break;
 416   }
 417   krb5_free_keyblock (gssapi_krb5_context, key);
 418   return ret;
 419 }