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         *hashtype = 0;
  67         *sighash = NULL;
  68
  69         switch (sig->data[0]) {
  70         case 2:
  71         case 3:
  72                 keyheader[0] = 0x99;
  73                 keyheader[1] = key->publickey->length >> 8;
  74                 keyheader[2] = key->publickey->length & 0xFF;
  75                 hashdata[0] = keyheader;
  76                 hashlen[0] = 3;
  77                 hashdata[1] = key->publickey->data;
  78                 hashlen[1] = key->publickey->length;
  79                 chunks = 2;
  80
  81                 *hashtype = sig->data[16];
  82
  83                 if (packet != NULL) {
  84                         if (packet->tag == OPENPGP_PACKET_PUBLICSUBKEY) {
  85                                 packetheader[0] = 0x99;
  86                                 packetheader[1] = packet->length >> 8;
  87                                 packetheader[2] = packet->length & 0xFF;
  88                                 hashdata[chunks] = packetheader;
  89                                 hashlen[chunks] = 3;
  90                                 chunks++;
  91                         }
  92
  93                         // TODO: Things other than UIDS/subkeys?
  94                         hashdata[chunks] = packet->data;
  95                         hashlen[chunks] = packet->length;
  96                         chunks++;
  97                 }
  98
  99                 hashdata[chunks] = &sig->data[2];
 100                 hashlen[chunks] = 5;
 101                 chunks++;
 102                 *sighash = &sig->data[17];
 103                 break;
 104         case 4:
 105                 keyheader[0] = 0x99;
 106                 keyheader[1] = key->publickey->length >> 8;
 107                 keyheader[2] = key->publickey->length & 0xFF;
 108                 hashdata[0] = keyheader;
 109                 hashlen[0] = 3;
 110                 hashdata[1] = key->publickey->data;
 111                 hashlen[1] = key->publickey->length;
 112                 chunks = 2;
 113
 114                 /* Check to see if this is an X509 based signature */
 115                 if (sig->data[2] == 0 || sig->data[2] == 100) {
 116                         size_t len;
 117
 118                         keyid = 0;
 119                         res = parse_subpackets(&sig->data[4],
 120                                                 sig->length - 4, &len,
 121                                                 &keyid, NULL);
 122                         if (res != ONAK_E_OK) {
 123                                 return res;
 124                         }
 125                         if (keyid == 0 &&
 126                                         /* No unhashed data */
 127                                         sig->data[4 + len] == 0 &&
 128                                         sig->data[5 + len] == 0 &&
 129                                         /* Dummy 0 checksum */
 130                                         sig->data[6 + len] == 0 &&
 131                                         sig->data[7 + len] == 0 &&
 132                                         /* Dummy MPI of 1 */
 133                                         sig->data[8 + len] == 0 &&
 134                                         sig->data[9 + len] == 1 &&
 135                                         sig->data[10 + len] == 1) {
 136                                 return ONAK_E_UNSUPPORTED_FEATURE;
 137                         }
 138                 }
 139
 140                 *hashtype = sig->data[3];
 141
 142                 if (packet != NULL) {
 143                         if (packet->tag == OPENPGP_PACKET_PUBLICSUBKEY) {
 144                                 packetheader[0] = 0x99;
 145                                 packetheader[1] = packet->length >> 8;
 146                                 packetheader[2] = packet->length & 0xFF;
 147                                 hashdata[chunks] = packetheader;
 148                                 hashlen[chunks] = 3;
 149                                 chunks++;
 150                         } else if (packet->tag == OPENPGP_PACKET_UID ||
 151                                         packet->tag == OPENPGP_PACKET_UAT) {
 152                                 packetheader[0] = (packet->tag ==
 153                                         OPENPGP_PACKET_UID) ?  0xB4 : 0xD1;
 154                                 packetheader[1] = packet->length >> 24;
 155                                 packetheader[2] = (packet->length >> 16) & 0xFF;
 156                                 packetheader[3] = (packet->length >> 8) & 0xFF;
 157                                 packetheader[4] = packet->length & 0xFF;
 158                                 hashdata[chunks] = packetheader;
 159                                 hashlen[chunks] = 5;
 160                                 chunks++;
 161                         }
 162                         hashdata[chunks] = packet->data;
 163                         hashlen[chunks] = packet->length;
 164                         chunks++;
 165                 }
 166
 167                 hashdata[chunks] = sig->data;
 168                 hashlen[chunks] = siglen = (sig->data[4] << 8) +
 169                         sig->data[5] + 6;;
 170                 if (siglen > sig->length) {
 171                         /* Signature data exceed packet length, bogus */
 172                         return ONAK_E_INVALID_PKT;
 173                 }
 174                 chunks++;
 175
 176                 trailer[0] = 4;
 177                 trailer[1] = 0xFF;
 178                 trailer[2] = siglen >> 24;
 179                 trailer[3] = (siglen >> 16) & 0xFF;
 180                 trailer[4] = (siglen >> 8) & 0xFF;
 181                 trailer[5] = siglen & 0xFF;
 182                 hashdata[chunks] = trailer;
 183                 hashlen[chunks] = 6;
 184                 chunks++;
 185
 186                 unhashedlen = (sig->data[siglen] << 8) +
 187                         sig->data[siglen + 1];
 188                 *sighash = &sig->data[siglen + unhashedlen + 2];
 189                 break;
 190         case 5:
 191                 keyheader[0] = 0x9A;
 192                 keyheader[1] = 0;
 193                 keyheader[2] = 0;
 194                 keyheader[3] = key->publickey->length >> 8;
 195                 keyheader[4] = key->publickey->length & 0xFF;
 196                 hashdata[0] = keyheader;
 197                 hashlen[0] = 5;
 198                 hashdata[1] = key->publickey->data;
 199                 hashlen[1] = key->publickey->length;
 200                 chunks = 2;
 201
 202                 *hashtype = sig->data[3];
 203
 204                 if (packet != NULL) {
 205                         if (packet->tag == OPENPGP_PACKET_PUBLICSUBKEY) {
 206                                 packetheader[0] = 0x9A;
 207                                 packetheader[1] = 0;
 208                                 packetheader[2] = 0;
 209                                 packetheader[3] = packet->length >> 8;
 210                                 packetheader[4] = packet->length & 0xFF;
 211                                 hashdata[chunks] = packetheader;
 212                                 hashlen[chunks] = 5;
 213                                 chunks++;
 214                         } else if (packet->tag == OPENPGP_PACKET_UID ||
 215                                         packet->tag == OPENPGP_PACKET_UAT) {
 216                                 packetheader[0] = (packet->tag ==
 217                                         OPENPGP_PACKET_UID) ?  0xB4 : 0xD1;
 218                                 packetheader[1] = packet->length >> 24;
 219                                 packetheader[2] = (packet->length >> 16) & 0xFF;
 220                                 packetheader[3] = (packet->length >> 8) & 0xFF;
 221                                 packetheader[4] = packet->length & 0xFF;
 222                                 hashdata[chunks] = packetheader;
 223                                 hashlen[chunks] = 5;
 224                                 chunks++;
 225                         }
 226                         hashdata[chunks] = packet->data;
 227                         hashlen[chunks] = packet->length;
 228                         chunks++;
 229                 }
 230
 231                 hashdata[chunks] = sig->data;
 232                 hashlen[chunks] = siglen = (sig->data[4] << 8) +
 233                         sig->data[5] + 6;;
 234                 if (siglen > sig->length) {
 235                         /* Signature data exceed packet length, bogus */
 236                         return ONAK_E_INVALID_PKT;
 237                 }
 238                 chunks++;
 239
 240                 trailer[0] = 5;
 241                 trailer[1] = 0xFF;
 242                 trailer[2] = 0;
 243                 trailer[3] = 0;
 244                 trailer[4] = 0;
 245                 trailer[5] = 0;
 246                 trailer[6] = siglen >> 24;
 247                 trailer[7] = (siglen >> 16) & 0xFF;
 248                 trailer[8] = (siglen >> 8) & 0xFF;
 249                 trailer[9] = siglen & 0xFF;
 250                 hashdata[chunks] = trailer;
 251                 hashlen[chunks] = 10;
 252                 chunks++;
 253
 254                 unhashedlen = (sig->data[siglen] << 8) +
 255                         sig->data[siglen + 1];
 256                 *sighash = &sig->data[siglen + unhashedlen + 2];
 257                 break;
 258         default:
 259                 return ONAK_E_UNSUPPORTED_FEATURE;
 260         }
 261
 262         switch (*hashtype) {
 263         case OPENPGP_HASH_MD5:
 264                 md5_init(&md5_context);
 265                 for (i = 0; i < chunks; i++) {
 266                         md5_update(&md5_context, hashlen[i], hashdata[i]);
 267                 }
 268                 md5_digest(&md5_context, MD5_DIGEST_SIZE, hash);
 269                 break;
 270         case OPENPGP_HASH_SHA1:
 271                 sha1_init(&sha1_context);
 272                 for (i = 0; i < chunks; i++) {
 273                         sha1_update(&sha1_context, hashlen[i], hashdata[i]);
 274                 }
 275                 sha1_digest(&sha1_context, SHA1_DIGEST_SIZE, hash);
 276                 break;
 277         case OPENPGP_HASH_SHA1X:
 278                 sha1x_init(&sha1x_context);
 279                 for (i = 0; i < chunks; i++) {
 280                         sha1x_update(&sha1x_context, hashlen[i], hashdata[i]);
 281                 }
 282                 sha1x_digest(&sha1x_context, SHA1X_DIGEST_SIZE, hash);
 283                 break;
 284 #ifdef HAVE_NETTLE
 285         case OPENPGP_HASH_RIPEMD160:
 286                 ripemd160_init(&ripemd160_context);
 287                 for (i = 0; i < chunks; i++) {
 288                         ripemd160_update(&ripemd160_context, hashlen[i],
 289                                 hashdata[i]);
 290                 }
 291                 ripemd160_digest(&ripemd160_context, RIPEMD160_DIGEST_SIZE,
 292                         hash);
 293                 break;
 294         case OPENPGP_HASH_SHA224:
 295                 sha224_init(&sha224_context);
 296                 for (i = 0; i < chunks; i++) {
 297                         sha224_update(&sha224_context, hashlen[i],
 298                                 hashdata[i]);
 299                 }
 300                 sha224_digest(&sha224_context, SHA224_DIGEST_SIZE, hash);
 301                 break;
 302         case OPENPGP_HASH_SHA256:
 303                 sha256_init(&sha256_context);
 304                 for (i = 0; i < chunks; i++) {
 305                         sha256_update(&sha256_context, hashlen[i],
 306                                 hashdata[i]);
 307                 }
 308                 sha256_digest(&sha256_context, SHA256_DIGEST_SIZE, hash);
 309                 break;
 310         case OPENPGP_HASH_SHA384:
 311                 sha384_init(&sha384_context);
 312                 for (i = 0; i < chunks; i++) {
 313                         sha384_update(&sha384_context, hashlen[i],
 314                                 hashdata[i]);
 315                 }
 316                 sha384_digest(&sha384_context, SHA384_DIGEST_SIZE, hash);
 317                 break;
 318         case OPENPGP_HASH_SHA512:
 319                 sha512_init(&sha512_context);
 320                 for (i = 0; i < chunks; i++) {
 321                         sha512_update(&sha512_context, hashlen[i],
 322                                 hashdata[i]);
 323                 }
 324                 sha512_digest(&sha512_context, SHA512_DIGEST_SIZE, hash);
 325                 break;
 326 #endif
 327         default:
 328                 return ONAK_E_UNSUPPORTED_FEATURE;
 329         }
 330
 331         return ONAK_E_OK;
 332 }