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 #include "sha1x.h"
  38
  39 int check_packet_sighash(struct openpgp_publickey *key,
  40                         struct openpgp_packet *packet,
  41                         struct openpgp_packet *sig)
  42 {
  43         uint8_t hashtype;
  44         uint8_t *sighash;
  45         size_t siglen, unhashedlen;
  46         struct sha1_ctx sha1_context;
  47         struct sha1x_ctx sha1x_context;
  48         struct md5_ctx md5_context;
  49 #ifdef NETTLE_WITH_RIPEMD160
  50         struct ripemd160_ctx ripemd160_context;
  51 #endif
  52 #ifdef NETTLE_WITH_SHA224
  53         struct sha224_ctx sha224_context;
  54 #endif
  55 #ifdef NETTLE_WITH_SHA256
  56         struct sha256_ctx sha256_context;
  57 #endif
  58 #ifdef NETTLE_WITH_SHA384
  59         struct sha384_ctx sha384_context;
  60 #endif
  61 #ifdef NETTLE_WITH_SHA512
  62         struct sha512_ctx sha512_context;
  63 #endif
  64         uint8_t keyheader[3];
  65         uint8_t packetheader[5];
  66         uint8_t v4trailer[6];
  67         uint8_t hash[64];
  68         uint8_t *hashdata[8];
  69         size_t hashlen[8];
  70         int chunks, i;
  71         uint64_t keyid;
  72
  73         keyheader[0] = 0x99;
  74         keyheader[1] = key->publickey->length >> 8;
  75         keyheader[2] = key->publickey->length & 0xFF;
  76         hashdata[0] = keyheader;
  77         hashlen[0] = 3;
  78         hashdata[1] = key->publickey->data;
  79         hashlen[1] = key->publickey->length;
  80         chunks = 2;
  81
  82         switch (sig->data[0]) {
  83         case 2:
  84         case 3:
  85                 hashtype = sig->data[16];
  86
  87                 if (packet != NULL) {
  88                         if (packet->tag == OPENPGP_PACKET_PUBLICSUBKEY) {
  89                                 packetheader[0] = 0x99;
  90                                 packetheader[1] = packet->length >> 8;
  91                                 packetheader[2] = packet->length & 0xFF;
  92                                 hashdata[chunks] = packetheader;
  93                                 hashlen[chunks] = 3;
  94                                 chunks++;
  95                         }
  96
  97                         // TODO: Things other than UIDS/subkeys?
  98                         hashdata[chunks] = packet->data;
  99                         hashlen[chunks] = packet->length;
 100                         chunks++;
 101                 }
 102
 103                 hashdata[chunks] = &sig->data[2];
 104                 hashlen[chunks] = 5;
 105                 chunks++;
 106                 sighash = &sig->data[17];
 107                 break;
 108         case 4:
 109                 hashtype = sig->data[3];
 110
 111                 if (packet != NULL) {
 112                         if (packet->tag == OPENPGP_PACKET_PUBLICSUBKEY) {
 113                                 packetheader[0] = 0x99;
 114                                 packetheader[1] = packet->length >> 8;
 115                                 packetheader[2] = packet->length & 0xFF;
 116                                 hashdata[chunks] = packetheader;
 117                                 hashlen[chunks] = 3;
 118                                 chunks++;
 119                         } else if (packet->tag == OPENPGP_PACKET_UID ||
 120                                         packet->tag == OPENPGP_PACKET_UAT) {
 121                                 packetheader[0] = (packet->tag ==
 122                                         OPENPGP_PACKET_UID) ?  0xB4 : 0xD1;
 123                                 packetheader[1] = packet->length >> 24;
 124                                 packetheader[2] = (packet->length >> 16) & 0xFF;
 125                                 packetheader[3] = (packet->length >> 8) & 0xFF;
 126                                 packetheader[4] = packet->length & 0xFF;
 127                                 hashdata[chunks] = packetheader;
 128                                 hashlen[chunks] = 5;
 129                                 chunks++;
 130                         }
 131                         hashdata[chunks] = packet->data;
 132                         hashlen[chunks] = packet->length;
 133                         chunks++;
 134                 }
 135
 136                 hashdata[chunks] = sig->data;
 137                 hashlen[chunks] = siglen = (sig->data[4] << 8) +
 138                         sig->data[5] + 6;;
 139                 chunks++;
 140
 141                 v4trailer[0] = 4;
 142                 v4trailer[1] = 0xFF;
 143                 v4trailer[2] = siglen >> 24;
 144                 v4trailer[3] = (siglen >> 16) & 0xFF;
 145                 v4trailer[4] = (siglen >> 8) & 0xFF;
 146                 v4trailer[5] = siglen & 0xFF;
 147                 hashdata[chunks] = v4trailer;
 148                 hashlen[chunks] = 6;
 149                 chunks++;
 150
 151                 unhashedlen = (sig->data[siglen] << 8) +
 152                         sig->data[siglen + 1];
 153                 sighash = &sig->data[siglen + unhashedlen + 2];
 154                 break;
 155         default:
 156                 get_keyid(key, &keyid);
 157                 logthing(LOGTHING_ERROR,
 158                         "Unknown signature version %d on 0x%016" PRIX64,
 159                         sig->data[0], keyid);
 160                 return -1;
 161         }
 162
 163         switch (hashtype) {
 164         case OPENPGP_HASH_MD5:
 165                 md5_init(&md5_context);
 166                 for (i = 0; i < chunks; i++) {
 167                         md5_update(&md5_context, hashlen[i], hashdata[i]);
 168                 }
 169                 md5_digest(&md5_context, 16, hash);
 170                 break;
 171         case OPENPGP_HASH_SHA1:
 172                 sha1_init(&sha1_context);
 173                 for (i = 0; i < chunks; i++) {
 174                         sha1_update(&sha1_context, hashlen[i], hashdata[i]);
 175                 }
 176                 sha1_digest(&sha1_context, 20, hash);
 177                 break;
 178         case OPENPGP_HASH_RIPEMD160:
 179 #ifdef NETTLE_WITH_RIPEMD160
 180                 ripemd160_init(&ripemd160_context);
 181                 for (i = 0; i < chunks; i++) {
 182                         ripemd160_update(&ripemd160_context, hashlen[i],
 183                                 hashdata[i]);
 184                 }
 185                 ripemd160_digest(&ripemd160_context, RIPEMD160_DIGEST_SIZE,
 186                         hash);
 187                 break;
 188 #else
 189                 logthing(LOGTHING_INFO, "RIPEMD160 support not available.");
 190                 return -1;
 191 #endif
 192         case OPENPGP_HASH_SHA1X:
 193                 sha1x_init(&sha1x_context);
 194                 for (i = 0; i < chunks; i++) {
 195                         sha1x_update(&sha1x_context, hashlen[i], hashdata[i]);
 196                 }
 197                 sha1x_digest(&sha1x_context, 20, hash);
 198                 break;
 199         case OPENPGP_HASH_SHA224:
 200 #ifdef NETTLE_WITH_SHA224
 201                 sha224_init(&sha224_context);
 202                 for (i = 0; i < chunks; i++) {
 203                         sha224_update(&sha224_context, hashlen[i],
 204                                 hashdata[i]);
 205                 }
 206                 sha224_digest(&sha224_context, SHA224_DIGEST_SIZE, hash);
 207                 break;
 208 #else
 209                 logthing(LOGTHING_INFO, "SHA224 support not available.");
 210                 return -1;
 211 #endif
 212         case OPENPGP_HASH_SHA256:
 213 #ifdef NETTLE_WITH_SHA256
 214                 sha256_init(&sha256_context);
 215                 for (i = 0; i < chunks; i++) {
 216                         sha256_update(&sha256_context, hashlen[i],
 217                                 hashdata[i]);
 218                 }
 219                 sha256_digest(&sha256_context, SHA256_DIGEST_SIZE, hash);
 220                 break;
 221 #else
 222                 logthing(LOGTHING_INFO, "SHA256 support not available.");
 223                 return -1;
 224 #endif
 225         case OPENPGP_HASH_SHA384:
 226 #ifdef NETTLE_WITH_SHA384
 227                 sha384_init(&sha384_context);
 228                 for (i = 0; i < chunks; i++) {
 229                         sha384_update(&sha384_context, hashlen[i],
 230                                 hashdata[i]);
 231                 }
 232                 sha384_digest(&sha384_context, SHA384_DIGEST_SIZE, hash);
 233                 break;
 234 #else
 235                 logthing(LOGTHING_INFO, "SHA384 support not available.");
 236                 return -1;
 237 #endif
 238         case OPENPGP_HASH_SHA512:
 239 #ifdef NETTLE_WITH_SHA512
 240                 sha512_init(&sha512_context);
 241                 for (i = 0; i < chunks; i++) {
 242                         sha512_update(&sha512_context, hashlen[i],
 243                                 hashdata[i]);
 244                 }
 245                 sha512_digest(&sha512_context, SHA512_DIGEST_SIZE, hash);
 246                 break;
 247 #else
 248                 logthing(LOGTHING_INFO, "SHA512 support not available.");
 249                 return -1;
 250 #endif
 251         default:
 252                 get_keyid(key, &keyid);
 253                 logthing(LOGTHING_ERROR,
 254                         "Unsupported signature hash type %d on 0x%016" PRIX64,
 255                         hashtype,
 256                         keyid);
 257                 return -1;
 258         }
 259
 260         logthing(LOGTHING_DEBUG, "Hash type: %d, %d chunks, "
 261                 "calculated: %02X%02X / actual: %02X%02X",
 262                 hashtype, chunks,
 263                 hash[0], hash[1], sighash[0], sighash[1]);
 264
 265         return (hash[0] == sighash[0] && hash[1] == sighash[1]);
 266 }