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, write to the Free Software Foundation, Inc., 51
  17  * Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  */
  19
  20 #include <stdint.h>
  21
  22 #include "config.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
  38 int check_packet_sighash(struct openpgp_publickey *key,
  39                         struct openpgp_packet *packet,
  40                         struct openpgp_packet *sig)
  41 {
  42         uint8_t hashtype;
  43         uint8_t *sighash;
  44         size_t siglen, unhashedlen;
  45         struct sha1_ctx sha1_context;
  46         struct md5_ctx md5_context;
  47 #ifdef NETTLE_WITH_RIPEMD160
  48         struct ripemd160_ctx ripemd160_context;
  49 #endif
  50 #ifdef NETTLE_WITH_SHA224
  51         struct sha224_ctx sha224_context;
  52 #endif
  53 #ifdef NETTLE_WITH_SHA256
  54         struct sha256_ctx sha256_context;
  55 #endif
  56 #ifdef NETTLE_WITH_SHA384
  57         struct sha384_ctx sha384_context;
  58 #endif
  59 #ifdef NETTLE_WITH_SHA512
  60         struct sha512_ctx sha512_context;
  61 #endif
  62         uint8_t keyheader[3];
  63         uint8_t packetheader[5];
  64         uint8_t v4trailer[6];
  65         uint8_t hash[64];
  66         uint8_t *hashdata[8];
  67         size_t hashlen[8];
  68         int chunks, i;
  69         uint64_t keyid;
  70
  71         keyheader[0] = 0x99;
  72         keyheader[1] = key->publickey->length >> 8;
  73         keyheader[2] = key->publickey->length & 0xFF;
  74         hashdata[0] = keyheader;
  75         hashlen[0] = 3;
  76         hashdata[1] = key->publickey->data;
  77         hashlen[1] = key->publickey->length;
  78         chunks = 2;
  79
  80         switch (sig->data[0]) {
  81         case 2:
  82         case 3:
  83                 hashtype = sig->data[16];
  84
  85                 if (packet != NULL) {
  86                         if (packet->tag == OPENPGP_PACKET_PUBLICSUBKEY) {
  87                                 packetheader[0] = 0x99;
  88                                 packetheader[1] = packet->length >> 8;
  89                                 packetheader[2] = packet->length & 0xFF;
  90                                 hashdata[chunks] = packetheader;
  91                                 hashlen[chunks] = 3;
  92                                 chunks++;
  93                         }
  94
  95                         // TODO: Things other than UIDS/subkeys?
  96                         hashdata[chunks] = packet->data;
  97                         hashlen[chunks] = packet->length;
  98                         chunks++;
  99                 }
 100
 101                 hashdata[chunks] = &sig->data[2];
 102                 hashlen[chunks] = 5;
 103                 chunks++;
 104                 sighash = &sig->data[17];
 105                 break;
 106         case 4:
 107                 hashtype = sig->data[3];
 108
 109                 if (packet != NULL) {
 110                         if (packet->tag == OPENPGP_PACKET_PUBLICSUBKEY) {
 111                                 packetheader[0] = 0x99;
 112                                 packetheader[1] = packet->length >> 8;
 113                                 packetheader[2] = packet->length & 0xFF;
 114                                 hashdata[chunks] = packetheader;
 115                                 hashlen[chunks] = 3;
 116                                 chunks++;
 117                         } else if (packet->tag == OPENPGP_PACKET_UID ||
 118                                         packet->tag == OPENPGP_PACKET_UAT) {
 119                                 packetheader[0] = (packet->tag ==
 120                                         OPENPGP_PACKET_UID) ?  0xB4 : 0xD1;
 121                                 packetheader[1] = packet->length >> 24;
 122                                 packetheader[2] = (packet->length >> 16) & 0xFF;
 123                                 packetheader[3] = (packet->length >> 8) & 0xFF;
 124                                 packetheader[4] = packet->length & 0xFF;
 125                                 hashdata[chunks] = packetheader;
 126                                 hashlen[chunks] = 5;
 127                                 chunks++;
 128                         }
 129                         hashdata[chunks] = packet->data;
 130                         hashlen[chunks] = packet->length;
 131                         chunks++;
 132                 }
 133
 134                 hashdata[chunks] = sig->data;
 135                 hashlen[chunks] = siglen = (sig->data[4] << 8) +
 136                         sig->data[5] + 6;;
 137                 chunks++;
 138
 139                 v4trailer[0] = 4;
 140                 v4trailer[1] = 0xFF;
 141                 v4trailer[2] = siglen >> 24;
 142                 v4trailer[3] = (siglen >> 16) & 0xFF;
 143                 v4trailer[4] = (siglen >> 8) & 0xFF;
 144                 v4trailer[5] = siglen & 0xFF;
 145                 hashdata[chunks] = v4trailer;
 146                 hashlen[chunks] = 6;
 147                 chunks++;
 148
 149                 unhashedlen = (sig->data[siglen] << 8) +
 150                         sig->data[siglen + 1];
 151                 sighash = &sig->data[siglen + unhashedlen + 2];
 152                 break;
 153         default:
 154                 get_keyid(key, &keyid);
 155                 logthing(LOGTHING_ERROR,
 156                         "Unknown signature version %d on 0x%016" PRIX64,
 157                         sig->data[0], keyid);
 158                 return -1;
 159         }
 160
 161         switch (hashtype) {
 162         case OPENPGP_HASH_MD5:
 163                 md5_init(&md5_context);
 164                 for (i = 0; i < chunks; i++) {
 165                         md5_update(&md5_context, hashlen[i], hashdata[i]);
 166                 }
 167                 md5_digest(&md5_context, 16, hash);
 168                 break;
 169         case OPENPGP_HASH_SHA1:
 170                 sha1_init(&sha1_context);
 171                 for (i = 0; i < chunks; i++) {
 172                         sha1_update(&sha1_context, hashlen[i], hashdata[i]);
 173                 }
 174                 sha1_digest(&sha1_context, 20, hash);
 175                 break;
 176         case OPENPGP_HASH_RIPEMD160:
 177 #ifdef NETTLE_WITH_RIPEMD160
 178                 ripemd160_init(&ripemd160_context);
 179                 for (i = 0; i < chunks; i++) {
 180                         ripemd160_update(&ripemd160_context, hashlen[i],
 181                                 hashdata[i]);
 182                 }
 183                 ripemd160_digest(&ripemd160_context, RIPEMD160_DIGEST_SIZE,
 184                         hash);
 185                 break;
 186 #else
 187                 logthing(LOGTHING_INFO, "RIPEMD160 support not available.");
 188                 return -1;
 189 #endif
 190         case OPENPGP_HASH_SHA224:
 191 #ifdef NETTLE_WITH_SHA224
 192                 sha224_init(&sha224_context);
 193                 for (i = 0; i < chunks; i++) {
 194                         sha224_update(&sha224_context, hashlen[i],
 195                                 hashdata[i]);
 196                 }
 197                 sha224_digest(&sha224_context, SHA224_DIGEST_SIZE, hash);
 198                 break;
 199 #else
 200                 logthing(LOGTHING_INFO, "SHA224 support not available.");
 201                 return -1;
 202 #endif
 203         case OPENPGP_HASH_SHA256:
 204 #ifdef NETTLE_WITH_SHA256
 205                 sha256_init(&sha256_context);
 206                 for (i = 0; i < chunks; i++) {
 207                         sha256_update(&sha256_context, hashlen[i],
 208                                 hashdata[i]);
 209                 }
 210                 sha256_digest(&sha256_context, SHA256_DIGEST_SIZE, hash);
 211                 break;
 212 #else
 213                 logthing(LOGTHING_INFO, "SHA256 support not available.");
 214                 return -1;
 215 #endif
 216         case OPENPGP_HASH_SHA384:
 217 #ifdef NETTLE_WITH_SHA384
 218                 sha384_init(&sha384_context);
 219                 for (i = 0; i < chunks; i++) {
 220                         sha384_update(&sha384_context, hashlen[i],
 221                                 hashdata[i]);
 222                 }
 223                 sha384_digest(&sha384_context, SHA384_DIGEST_SIZE, hash);
 224                 break;
 225 #else
 226                 logthing(LOGTHING_INFO, "SHA384 support not available.");
 227                 return -1;
 228 #endif
 229         case OPENPGP_HASH_SHA512:
 230 #ifdef NETTLE_WITH_SHA512
 231                 sha512_init(&sha512_context);
 232                 for (i = 0; i < chunks; i++) {
 233                         sha512_update(&sha512_context, hashlen[i],
 234                                 hashdata[i]);
 235                 }
 236                 sha512_digest(&sha512_context, SHA512_DIGEST_SIZE, hash);
 237                 break;
 238 #else
 239                 logthing(LOGTHING_INFO, "SHA512 support not available.");
 240                 return -1;
 241 #endif
 242         default:
 243                 get_keyid(key, &keyid);
 244                 logthing(LOGTHING_ERROR,
 245                         "Unsupported signature hash type %d on 0x%016" PRIX64,
 246                         hashtype,
 247                         keyid);
 248                 return -1;
 249         }
 250
 251         logthing(LOGTHING_DEBUG, "Hash type: %d, %d chunks, "
 252                 "calculated: %02X%02X / actual: %02X%02X\n",
 253                 hashtype, chunks,
 254                 hash[0], hash[1], sighash[0], sighash[1]);
 255
 256         return (hash[0] == sighash[0] && hash[1] == sighash[1]);
 257 }