sigcheck.c

   1 /*
   2  * sigcheck.c - routines to check OpenPGP signatures
   3  *
   4  * Copyright 2012 Jonathan McDowell <noodles@earth.li>
   5  *
   6  * This program is free software: you can redistribute it and/or modify it
   7  * under the terms of the GNU General Public License as published by the Free
   8  * Software Foundation; version 2 of the License.
   9  *
  10  * This program is distributed in the hope that it will be useful, but WITHOUT
  11  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  12  * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
  13  * more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along with
  16  * this program.  If not, see <https://www.gnu.org/licenses/>.
  17  */
  18
  19 #include <stdint.h>
  20
  21 #include "build-config.h"
  22 #include "decodekey.h"
  23 #include "keyid.h"
  24 #include "keystructs.h"
  25 #include "log.h"
  26 #include "openpgp.h"
  27 #include "sigcheck.h"
  28
  29 #ifdef HAVE_NETTLE
  30 #include <nettle/md5.h>
  31 #include <nettle/ripemd160.h>
  32 #include <nettle/sha.h>
  33 #else
  34 #include "md5.h"
  35 #include "sha1.h"
  36 #endif
  37 #include "sha1x.h"
  38
  39 onak_status_t calculate_packet_sighash(struct openpgp_publickey *key,
  40                         struct openpgp_packet *packet,
  41                         struct openpgp_packet *sig,
  42                         uint8_t *hashtype,
  43                         uint8_t *hash,
  44                         uint8_t **sighash)
  45 {
  46         size_t siglen, unhashedlen;
  47         struct sha1_ctx sha1_context;
  48         struct sha1x_ctx sha1x_context;
  49         struct md5_ctx md5_context;
  50 #ifdef HAVE_NETTLE
  51         struct ripemd160_ctx ripemd160_context;
  52         struct sha224_ctx sha224_context;
  53         struct sha256_ctx sha256_context;
  54         struct sha384_ctx sha384_context;
  55         struct sha512_ctx sha512_context;
  56 #endif
  57         uint8_t keyheader[5];
  58         uint8_t packetheader[5];
  59         uint8_t trailer[10];
  60         uint8_t *hashdata[8];
  61         size_t hashlen[8];
  62         int chunks, i;
  63         uint64_t keyid;
  64         onak_status_t res;
  65
  66         switch (sig->data[0]) {
  67         case 2:
  68         case 3:
  69                 keyheader[0] = 0x99;
  70                 keyheader[1] = key->publickey->length >> 8;
  71                 keyheader[2] = key->publickey->length & 0xFF;
  72                 hashdata[0] = keyheader;
  73                 hashlen[0] = 3;
  74                 hashdata[1] = key->publickey->data;
  75                 hashlen[1] = key->publickey->length;
  76                 chunks = 2;
  77
  78                 *hashtype = sig->data[16];
  79
  80                 if (packet != NULL) {
  81                         if (packet->tag == OPENPGP_PACKET_PUBLICSUBKEY) {
  82                                 packetheader[0] = 0x99;
  83                                 packetheader[1] = packet->length >> 8;
  84                                 packetheader[2] = packet->length & 0xFF;
  85                                 hashdata[chunks] = packetheader;
  86                                 hashlen[chunks] = 3;
  87                                 chunks++;
  88                         }
  89
  90                         // TODO: Things other than UIDS/subkeys?
  91                         hashdata[chunks] = packet->data;
  92                         hashlen[chunks] = packet->length;
  93                         chunks++;
  94                 }
  95
  96                 hashdata[chunks] = &sig->data[2];
  97                 hashlen[chunks] = 5;
  98                 chunks++;
  99                 *sighash = &sig->data[17];
 100                 break;
 101         case 4:
 102                 keyheader[0] = 0x99;
 103                 keyheader[1] = key->publickey->length >> 8;
 104                 keyheader[2] = key->publickey->length & 0xFF;
 105                 hashdata[0] = keyheader;
 106                 hashlen[0] = 3;
 107                 hashdata[1] = key->publickey->data;
 108                 hashlen[1] = key->publickey->length;
 109                 chunks = 2;
 110
 111                 *hashtype = sig->data[3];
 112
 113                 /* Check to see if this is an X509 based signature */
 114                 if (sig->data[2] == 0 || sig->data[2] == 100) {
 115                         size_t len;
 116
 117                         keyid = 0;
 118                         res = parse_subpackets(&sig->data[4],
 119                                                 sig->length - 4, &len,
 120                                                 &keyid, NULL);
 121                         if (res != ONAK_E_OK) {
 122                                 return res;
 123                         }
 124                         if (keyid == 0 &&
 125                                         /* No unhashed data */
 126                                         sig->data[4 + len] == 0 &&
 127                                         sig->data[5 + len] == 0 &&
 128                                         /* Dummy 0 checksum */
 129                                         sig->data[6 + len] == 0 &&
 130                                         sig->data[7 + len] == 0 &&
 131                                         /* Dummy MPI of 1 */
 132                                         sig->data[8 + len] == 0 &&
 133                                         sig->data[9 + len] == 1 &&
 134                                         sig->data[10 + len] == 1) {
 135                                 return ONAK_E_UNSUPPORTED_FEATURE;
 136                         }
 137                 }
 138
 139                 if (packet != NULL) {
 140                         if (packet->tag == OPENPGP_PACKET_PUBLICSUBKEY) {
 141                                 packetheader[0] = 0x99;
 142                                 packetheader[1] = packet->length >> 8;
 143                                 packetheader[2] = packet->length & 0xFF;
 144                                 hashdata[chunks] = packetheader;
 145                                 hashlen[chunks] = 3;
 146                                 chunks++;
 147                         } else if (packet->tag == OPENPGP_PACKET_UID ||
 148                                         packet->tag == OPENPGP_PACKET_UAT) {
 149                                 packetheader[0] = (packet->tag ==
 150                                         OPENPGP_PACKET_UID) ?  0xB4 : 0xD1;
 151                                 packetheader[1] = packet->length >> 24;
 152                                 packetheader[2] = (packet->length >> 16) & 0xFF;
 153                                 packetheader[3] = (packet->length >> 8) & 0xFF;
 154                                 packetheader[4] = packet->length & 0xFF;
 155                                 hashdata[chunks] = packetheader;
 156                                 hashlen[chunks] = 5;
 157                                 chunks++;
 158                         }
 159                         hashdata[chunks] = packet->data;
 160                         hashlen[chunks] = packet->length;
 161                         chunks++;
 162                 }
 163
 164                 hashdata[chunks] = sig->data;
 165                 hashlen[chunks] = siglen = (sig->data[4] << 8) +
 166                         sig->data[5] + 6;;
 167                 if (siglen > sig->length) {
 168                         /* Signature data exceed packet length, bogus */
 169                         return ONAK_E_INVALID_PKT;
 170                 }
 171                 chunks++;
 172
 173                 trailer[0] = 4;
 174                 trailer[1] = 0xFF;
 175                 trailer[2] = siglen >> 24;
 176                 trailer[3] = (siglen >> 16) & 0xFF;
 177                 trailer[4] = (siglen >> 8) & 0xFF;
 178                 trailer[5] = siglen & 0xFF;
 179                 hashdata[chunks] = trailer;
 180                 hashlen[chunks] = 6;
 181                 chunks++;
 182
 183                 unhashedlen = (sig->data[siglen] << 8) +
 184                         sig->data[siglen + 1];
 185                 *sighash = &sig->data[siglen + unhashedlen + 2];
 186                 break;
 187         case 5:
 188                 keyheader[0] = 0x9A;
 189                 keyheader[1] = 0;
 190                 keyheader[2] = 0;
 191                 keyheader[3] = key->publickey->length >> 8;
 192                 keyheader[4] = key->publickey->length & 0xFF;
 193                 hashdata[0] = keyheader;
 194                 hashlen[0] = 5;
 195                 hashdata[1] = key->publickey->data;
 196                 hashlen[1] = key->publickey->length;
 197                 chunks = 2;
 198
 199                 *hashtype = sig->data[3];
 200
 201                 if (packet != NULL) {
 202                         if (packet->tag == OPENPGP_PACKET_PUBLICSUBKEY) {
 203                                 packetheader[0] = 0x9A;
 204                                 packetheader[1] = 0;
 205                                 packetheader[2] = 0;
 206                                 packetheader[3] = packet->length >> 8;
 207                                 packetheader[4] = packet->length & 0xFF;
 208                                 hashdata[chunks] = packetheader;
 209                                 hashlen[chunks] = 5;
 210                                 chunks++;
 211                         } else if (packet->tag == OPENPGP_PACKET_UID ||
 212                                         packet->tag == OPENPGP_PACKET_UAT) {
 213                                 packetheader[0] = (packet->tag ==
 214                                         OPENPGP_PACKET_UID) ?  0xB4 : 0xD1;
 215                                 packetheader[1] = packet->length >> 24;
 216                                 packetheader[2] = (packet->length >> 16) & 0xFF;
 217                                 packetheader[3] = (packet->length >> 8) & 0xFF;
 218                                 packetheader[4] = packet->length & 0xFF;
 219                                 hashdata[chunks] = packetheader;
 220                                 hashlen[chunks] = 5;
 221                                 chunks++;
 222                         }
 223                         hashdata[chunks] = packet->data;
 224                         hashlen[chunks] = packet->length;
 225                         chunks++;
 226                 }
 227
 228                 hashdata[chunks] = sig->data;
 229                 hashlen[chunks] = siglen = (sig->data[4] << 8) +
 230                         sig->data[5] + 6;;
 231                 if (siglen > sig->length) {
 232                         /* Signature data exceed packet length, bogus */
 233                         return ONAK_E_INVALID_PKT;
 234                 }
 235                 chunks++;
 236
 237                 trailer[0] = 5;
 238                 trailer[1] = 0xFF;
 239                 trailer[2] = 0;
 240                 trailer[3] = 0;
 241                 trailer[4] = 0;
 242                 trailer[5] = 0;
 243                 trailer[6] = siglen >> 24;
 244                 trailer[7] = (siglen >> 16) & 0xFF;
 245                 trailer[8] = (siglen >> 8) & 0xFF;
 246                 trailer[9] = siglen & 0xFF;
 247                 hashdata[chunks] = trailer;
 248                 hashlen[chunks] = 10;
 249                 chunks++;
 250
 251                 unhashedlen = (sig->data[siglen] << 8) +
 252                         sig->data[siglen + 1];
 253                 *sighash = &sig->data[siglen + unhashedlen + 2];
 254                 break;
 255         default:
 256                 return ONAK_E_UNSUPPORTED_FEATURE;
 257         }
 258
 259         switch (*hashtype) {
 260         case OPENPGP_HASH_MD5:
 261                 md5_init(&md5_context);
 262                 for (i = 0; i < chunks; i++) {
 263                         md5_update(&md5_context, hashlen[i], hashdata[i]);
 264                 }
 265                 md5_digest(&md5_context, 16, hash);
 266                 break;
 267         case OPENPGP_HASH_SHA1:
 268                 sha1_init(&sha1_context);
 269                 for (i = 0; i < chunks; i++) {
 270                         sha1_update(&sha1_context, hashlen[i], hashdata[i]);
 271                 }
 272                 sha1_digest(&sha1_context, 20, hash);
 273                 break;
 274         case OPENPGP_HASH_SHA1X:
 275                 sha1x_init(&sha1x_context);
 276                 for (i = 0; i < chunks; i++) {
 277                         sha1x_update(&sha1x_context, hashlen[i], hashdata[i]);
 278                 }
 279                 sha1x_digest(&sha1x_context, 20, hash);
 280                 break;
 281 #ifdef HAVE_NETTLE
 282         case OPENPGP_HASH_RIPEMD160:
 283                 ripemd160_init(&ripemd160_context);
 284                 for (i = 0; i < chunks; i++) {
 285                         ripemd160_update(&ripemd160_context, hashlen[i],
 286                                 hashdata[i]);
 287                 }
 288                 ripemd160_digest(&ripemd160_context, RIPEMD160_DIGEST_SIZE,
 289                         hash);
 290                 break;
 291         case OPENPGP_HASH_SHA224:
 292                 sha224_init(&sha224_context);
 293                 for (i = 0; i < chunks; i++) {
 294                         sha224_update(&sha224_context, hashlen[i],
 295                                 hashdata[i]);
 296                 }
 297                 sha224_digest(&sha224_context, SHA224_DIGEST_SIZE, hash);
 298                 break;
 299         case OPENPGP_HASH_SHA256:
 300                 sha256_init(&sha256_context);
 301                 for (i = 0; i < chunks; i++) {
 302                         sha256_update(&sha256_context, hashlen[i],
 303                                 hashdata[i]);
 304                 }
 305                 sha256_digest(&sha256_context, SHA256_DIGEST_SIZE, hash);
 306                 break;
 307         case OPENPGP_HASH_SHA384:
 308                 sha384_init(&sha384_context);
 309                 for (i = 0; i < chunks; i++) {
 310                         sha384_update(&sha384_context, hashlen[i],
 311                                 hashdata[i]);
 312                 }
 313                 sha384_digest(&sha384_context, SHA384_DIGEST_SIZE, hash);
 314                 break;
 315         case OPENPGP_HASH_SHA512:
 316                 sha512_init(&sha512_context);
 317                 for (i = 0; i < chunks; i++) {
 318                         sha512_update(&sha512_context, hashlen[i],
 319                                 hashdata[i]);
 320                 }
 321                 sha512_digest(&sha512_context, SHA512_DIGEST_SIZE, hash);
 322                 break;
 323 #endif
 324         default:
 325                 return ONAK_E_UNSUPPORTED_FEATURE;
 326         }
 327
 328         return ONAK_E_OK;
 329 }