Damien Miller | a664e87 | 2000-04-16 11:52:47 +1000 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (c) 2000 Markus Friedl. All rights reserved. |
| 3 | * |
| 4 | * Redistribution and use in source and binary forms, with or without |
| 5 | * modification, are permitted provided that the following conditions |
| 6 | * are met: |
| 7 | * 1. Redistributions of source code must retain the above copyright |
| 8 | * notice, this list of conditions and the following disclaimer. |
| 9 | * 2. Redistributions in binary form must reproduce the above copyright |
| 10 | * notice, this list of conditions and the following disclaimer in the |
| 11 | * documentation and/or other materials provided with the distribution. |
| 12 | * 3. All advertising materials mentioning features or use of this software |
| 13 | * must display the following acknowledgement: |
| 14 | * This product includes software developed by Markus Friedl. |
| 15 | * 4. The name of the author may not be used to endorse or promote products |
| 16 | * derived from this software without specific prior written permission. |
| 17 | * |
| 18 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
| 19 | * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
| 20 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
| 21 | * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
| 22 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
| 23 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| 24 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| 25 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| 26 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
| 27 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| 28 | */ |
| 29 | |
| 30 | #include "includes.h" |
Damien Miller | 30c3d42 | 2000-05-09 11:02:59 +1000 | [diff] [blame] | 31 | RCSID("$Id: kex.c,v 1.8 2000/05/09 01:03:01 damien Exp $"); |
Damien Miller | a664e87 | 2000-04-16 11:52:47 +1000 | [diff] [blame] | 32 | |
| 33 | #include "ssh.h" |
| 34 | #include "ssh2.h" |
| 35 | #include "xmalloc.h" |
| 36 | #include "buffer.h" |
| 37 | #include "bufaux.h" |
| 38 | #include "cipher.h" |
| 39 | #include "compat.h" |
| 40 | |
| 41 | #include <openssl/bn.h> |
| 42 | #include <openssl/dh.h> |
| 43 | |
| 44 | #include <openssl/crypto.h> |
| 45 | #include <openssl/bio.h> |
| 46 | #include <openssl/bn.h> |
| 47 | #include <openssl/dh.h> |
| 48 | #include <openssl/pem.h> |
| 49 | |
| 50 | #include "kex.h" |
| 51 | |
| 52 | Buffer * |
| 53 | kex_init(char *myproposal[PROPOSAL_MAX]) |
| 54 | { |
| 55 | char c = 0; |
| 56 | unsigned char cookie[16]; |
| 57 | u_int32_t rand = 0; |
| 58 | int i; |
| 59 | Buffer *ki = xmalloc(sizeof(*ki)); |
| 60 | for (i = 0; i < 16; i++) { |
| 61 | if (i % 4 == 0) |
| 62 | rand = arc4random(); |
| 63 | cookie[i] = rand & 0xff; |
| 64 | rand >>= 8; |
| 65 | } |
| 66 | buffer_init(ki); |
| 67 | buffer_append(ki, (char *)cookie, sizeof cookie); |
| 68 | for (i = 0; i < PROPOSAL_MAX; i++) |
| 69 | buffer_put_cstring(ki, myproposal[i]); |
| 70 | buffer_append(ki, &c, 1); /* boolean first_kex_packet_follows */ |
| 71 | buffer_put_int(ki, 0); /* uint32 0 (reserved for future extension) */ |
| 72 | return ki; |
| 73 | } |
| 74 | |
| 75 | /* diffie-hellman-group1-sha1 */ |
| 76 | |
| 77 | int |
| 78 | dh_pub_is_valid(DH *dh, BIGNUM *dh_pub) |
| 79 | { |
| 80 | int i; |
| 81 | int n = BN_num_bits(dh_pub); |
| 82 | int bits_set = 0; |
| 83 | |
| 84 | /* we only accept g==2 */ |
| 85 | if (!BN_is_word(dh->g, 2)) { |
| 86 | log("invalid DH base != 2"); |
| 87 | return 0; |
| 88 | } |
| 89 | if (dh_pub->neg) { |
| 90 | log("invalid public DH value: negativ"); |
| 91 | return 0; |
| 92 | } |
| 93 | for (i = 0; i <= n; i++) |
| 94 | if (BN_is_bit_set(dh_pub, i)) |
| 95 | bits_set++; |
| 96 | debug("bits set: %d/%d", bits_set, BN_num_bits(dh->p)); |
| 97 | |
| 98 | /* if g==2 and bits_set==1 then computing log_g(dh_pub) is trivial */ |
| 99 | if (bits_set > 1 && (BN_cmp(dh_pub, dh->p) == -1)) |
| 100 | return 1; |
| 101 | log("invalid public DH value (%d/%d)", bits_set, BN_num_bits(dh->p)); |
| 102 | return 0; |
| 103 | } |
| 104 | |
| 105 | DH * |
| 106 | dh_new_group1() |
| 107 | { |
| 108 | static char *group1 = |
| 109 | "FFFFFFFF" "FFFFFFFF" "C90FDAA2" "2168C234" "C4C6628B" "80DC1CD1" |
| 110 | "29024E08" "8A67CC74" "020BBEA6" "3B139B22" "514A0879" "8E3404DD" |
| 111 | "EF9519B3" "CD3A431B" "302B0A6D" "F25F1437" "4FE1356D" "6D51C245" |
| 112 | "E485B576" "625E7EC6" "F44C42E9" "A637ED6B" "0BFF5CB6" "F406B7ED" |
| 113 | "EE386BFB" "5A899FA5" "AE9F2411" "7C4B1FE6" "49286651" "ECE65381" |
| 114 | "FFFFFFFF" "FFFFFFFF"; |
| 115 | DH *dh; |
| 116 | int ret, tries = 0; |
| 117 | dh = DH_new(); |
| 118 | if(dh == NULL) |
| 119 | fatal("DH_new"); |
| 120 | ret = BN_hex2bn(&dh->p, group1); |
| 121 | if(ret<0) |
| 122 | fatal("BN_hex2bn"); |
| 123 | dh->g = BN_new(); |
| 124 | if(dh->g == NULL) |
| 125 | fatal("DH_new g"); |
| 126 | BN_set_word(dh->g, 2); |
| 127 | do { |
| 128 | if (DH_generate_key(dh) == 0) |
| 129 | fatal("DH_generate_key"); |
| 130 | if (tries++ > 10) |
| 131 | fatal("dh_new_group1: too many bad keys: giving up"); |
| 132 | } while (!dh_pub_is_valid(dh, dh->pub_key)); |
| 133 | return dh; |
| 134 | } |
| 135 | |
| 136 | void |
| 137 | bignum_print(BIGNUM *b) |
| 138 | { |
| 139 | BN_print_fp(stderr,b); |
| 140 | } |
| 141 | |
| 142 | void |
| 143 | dump_digest(unsigned char *digest, int len) |
| 144 | { |
| 145 | int i; |
| 146 | for (i = 0; i< len; i++){ |
| 147 | fprintf(stderr, "%02x", digest[i]); |
| 148 | if(i%2!=0) |
| 149 | fprintf(stderr, " "); |
| 150 | } |
| 151 | fprintf(stderr, "\n"); |
| 152 | } |
| 153 | |
| 154 | unsigned char * |
| 155 | kex_hash( |
| 156 | char *client_version_string, |
| 157 | char *server_version_string, |
| 158 | char *ckexinit, int ckexinitlen, |
| 159 | char *skexinit, int skexinitlen, |
| 160 | char *serverhostkeyblob, int sbloblen, |
| 161 | BIGNUM *client_dh_pub, |
| 162 | BIGNUM *server_dh_pub, |
| 163 | BIGNUM *shared_secret) |
| 164 | { |
| 165 | Buffer b; |
| 166 | static unsigned char digest[EVP_MAX_MD_SIZE]; |
| 167 | EVP_MD *evp_md = EVP_sha1(); |
| 168 | EVP_MD_CTX md; |
| 169 | |
| 170 | buffer_init(&b); |
| 171 | buffer_put_string(&b, client_version_string, strlen(client_version_string)); |
| 172 | buffer_put_string(&b, server_version_string, strlen(server_version_string)); |
| 173 | |
| 174 | /* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */ |
| 175 | buffer_put_int(&b, ckexinitlen+1); |
| 176 | buffer_put_char(&b, SSH2_MSG_KEXINIT); |
| 177 | buffer_append(&b, ckexinit, ckexinitlen); |
| 178 | buffer_put_int(&b, skexinitlen+1); |
| 179 | buffer_put_char(&b, SSH2_MSG_KEXINIT); |
| 180 | buffer_append(&b, skexinit, skexinitlen); |
| 181 | |
| 182 | buffer_put_string(&b, serverhostkeyblob, sbloblen); |
| 183 | buffer_put_bignum2(&b, client_dh_pub); |
| 184 | buffer_put_bignum2(&b, server_dh_pub); |
| 185 | buffer_put_bignum2(&b, shared_secret); |
| 186 | |
| 187 | #ifdef DEBUG_KEX |
| 188 | buffer_dump(&b); |
| 189 | #endif |
| 190 | |
| 191 | EVP_DigestInit(&md, evp_md); |
| 192 | EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b)); |
| 193 | EVP_DigestFinal(&md, digest, NULL); |
| 194 | |
| 195 | buffer_free(&b); |
| 196 | |
| 197 | #ifdef DEBUG_KEX |
| 198 | dump_digest(digest, evp_md->md_size); |
| 199 | #endif |
| 200 | return digest; |
| 201 | } |
| 202 | |
| 203 | unsigned char * |
| 204 | derive_key(int id, int need, char unsigned *hash, BIGNUM *shared_secret) |
| 205 | { |
| 206 | Buffer b; |
| 207 | EVP_MD *evp_md = EVP_sha1(); |
| 208 | EVP_MD_CTX md; |
| 209 | char c = id; |
| 210 | int have; |
| 211 | int mdsz = evp_md->md_size; |
| 212 | unsigned char *digest = xmalloc(((need+mdsz-1)/mdsz)*mdsz); |
| 213 | |
| 214 | buffer_init(&b); |
| 215 | buffer_put_bignum2(&b, shared_secret); |
| 216 | |
| 217 | EVP_DigestInit(&md, evp_md); |
| 218 | EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b)); /* shared_secret K */ |
| 219 | EVP_DigestUpdate(&md, hash, mdsz); /* transport-06 */ |
| 220 | EVP_DigestUpdate(&md, &c, 1); /* key id */ |
| 221 | EVP_DigestUpdate(&md, hash, mdsz); /* session id */ |
| 222 | EVP_DigestFinal(&md, digest, NULL); |
| 223 | |
| 224 | /* expand */ |
| 225 | for (have = mdsz; need > have; have += mdsz) { |
| 226 | EVP_DigestInit(&md, evp_md); |
| 227 | EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b)); |
| 228 | EVP_DigestUpdate(&md, hash, mdsz); |
| 229 | EVP_DigestUpdate(&md, digest, have); |
| 230 | EVP_DigestFinal(&md, digest + have, NULL); |
| 231 | } |
| 232 | buffer_free(&b); |
| 233 | #ifdef DEBUG_KEX |
| 234 | fprintf(stderr, "Digest '%c'== ", c); |
| 235 | dump_digest(digest, need); |
| 236 | #endif |
| 237 | return digest; |
| 238 | } |
| 239 | |
| 240 | #define NKEYS 6 |
| 241 | |
| 242 | #define MAX_PROP 20 |
| 243 | #define SEP "," |
| 244 | |
| 245 | char * |
| 246 | get_match(char *client, char *server) |
| 247 | { |
| 248 | char *sproposals[MAX_PROP]; |
| 249 | char *p; |
| 250 | int i, j, nproposals; |
| 251 | |
| 252 | for ((p = strtok(server, SEP)), i=0; p; (p = strtok(NULL, SEP)), i++) { |
| 253 | if (i < MAX_PROP) |
| 254 | sproposals[i] = p; |
| 255 | else |
| 256 | break; |
| 257 | } |
| 258 | nproposals = i; |
| 259 | |
| 260 | for ((p = strtok(client, SEP)), i=0; p; (p = strtok(NULL, SEP)), i++) { |
| 261 | for (j = 0; j < nproposals; j++) |
| 262 | if (strcmp(p, sproposals[j]) == 0) |
| 263 | return xstrdup(p); |
| 264 | } |
| 265 | return NULL; |
| 266 | } |
| 267 | void |
| 268 | choose_enc(Enc *enc, char *client, char *server) |
| 269 | { |
| 270 | char *name = get_match(client, server); |
| 271 | if (name == NULL) |
| 272 | fatal("no matching cipher found: client %s server %s", client, server); |
| 273 | enc->type = cipher_number(name); |
| 274 | |
| 275 | switch (enc->type) { |
| 276 | case SSH_CIPHER_3DES_CBC: |
| 277 | enc->key_len = 24; |
| 278 | enc->iv_len = 8; |
| 279 | enc->block_size = 8; |
| 280 | break; |
| 281 | case SSH_CIPHER_BLOWFISH_CBC: |
| 282 | case SSH_CIPHER_CAST128_CBC: |
| 283 | enc->key_len = 16; |
| 284 | enc->iv_len = 8; |
| 285 | enc->block_size = 8; |
| 286 | break; |
| 287 | case SSH_CIPHER_ARCFOUR: |
| 288 | enc->key_len = 16; |
| 289 | enc->iv_len = 0; |
| 290 | enc->block_size = 8; |
| 291 | break; |
| 292 | default: |
| 293 | fatal("unsupported cipher %s", name); |
| 294 | } |
| 295 | enc->name = name; |
| 296 | enc->enabled = 0; |
| 297 | enc->iv = NULL; |
| 298 | enc->key = NULL; |
| 299 | } |
| 300 | void |
| 301 | choose_mac(Mac *mac, char *client, char *server) |
| 302 | { |
| 303 | char *name = get_match(client, server); |
| 304 | if (name == NULL) |
| 305 | fatal("no matching mac found: client %s server %s", client, server); |
| 306 | if (strcmp(name, "hmac-md5") == 0) { |
| 307 | mac->md = EVP_md5(); |
| 308 | } else if (strcmp(name, "hmac-sha1") == 0) { |
| 309 | mac->md = EVP_sha1(); |
| 310 | } else if (strcmp(name, "hmac-ripemd160@openssh.com") == 0) { |
| 311 | mac->md = EVP_ripemd160(); |
| 312 | } else { |
| 313 | fatal("unsupported mac %s", name); |
| 314 | } |
| 315 | mac->name = name; |
| 316 | mac->mac_len = mac->md->md_size; |
Damien Miller | 30c3d42 | 2000-05-09 11:02:59 +1000 | [diff] [blame] | 317 | mac->key_len = (datafellows & SSH_BUG_HMAC) ? 16 : mac->mac_len; |
Damien Miller | a664e87 | 2000-04-16 11:52:47 +1000 | [diff] [blame] | 318 | mac->key = NULL; |
| 319 | mac->enabled = 0; |
| 320 | } |
| 321 | void |
| 322 | choose_comp(Comp *comp, char *client, char *server) |
| 323 | { |
| 324 | char *name = get_match(client, server); |
| 325 | if (name == NULL) |
| 326 | fatal("no matching comp found: client %s server %s", client, server); |
| 327 | if (strcmp(name, "zlib") == 0) { |
| 328 | comp->type = 1; |
| 329 | } else if (strcmp(name, "none") == 0) { |
| 330 | comp->type = 0; |
| 331 | } else { |
| 332 | fatal("unsupported comp %s", name); |
| 333 | } |
| 334 | comp->name = name; |
| 335 | } |
| 336 | void |
| 337 | choose_kex(Kex *k, char *client, char *server) |
| 338 | { |
| 339 | k->name = get_match(client, server); |
| 340 | if (k->name == NULL) |
| 341 | fatal("no kex alg"); |
| 342 | if (strcmp(k->name, KEX_DH1) != 0) |
| 343 | fatal("bad kex alg %s", k->name); |
| 344 | } |
| 345 | void |
| 346 | choose_hostkeyalg(Kex *k, char *client, char *server) |
| 347 | { |
| 348 | k->hostkeyalg = get_match(client, server); |
| 349 | if (k->hostkeyalg == NULL) |
| 350 | fatal("no hostkey alg"); |
| 351 | if (strcmp(k->hostkeyalg, KEX_DSS) != 0) |
| 352 | fatal("bad hostkey alg %s", k->hostkeyalg); |
| 353 | } |
| 354 | |
| 355 | Kex * |
| 356 | kex_choose_conf(char *cprop[PROPOSAL_MAX], char *sprop[PROPOSAL_MAX], int server) |
| 357 | { |
| 358 | int i; |
| 359 | int mode; |
| 360 | int ctos; /* direction: if true client-to-server */ |
| 361 | int need; |
| 362 | Kex *k; |
| 363 | |
| 364 | k = xmalloc(sizeof(*k)); |
| 365 | memset(k, 0, sizeof(*k)); |
| 366 | k->server = server; |
| 367 | |
| 368 | for (mode = 0; mode < MODE_MAX; mode++) { |
| 369 | int nenc, nmac, ncomp; |
| 370 | ctos = (!k->server && mode == MODE_OUT) || (k->server && mode == MODE_IN); |
| 371 | nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC; |
| 372 | nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC; |
| 373 | ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC; |
| 374 | choose_enc (&k->enc [mode], cprop[nenc], sprop[nenc]); |
| 375 | choose_mac (&k->mac [mode], cprop[nmac], sprop[nmac]); |
| 376 | choose_comp(&k->comp[mode], cprop[ncomp], sprop[ncomp]); |
| 377 | debug("kex: %s %s %s %s", |
| 378 | ctos ? "client->server" : "server->client", |
| 379 | k->enc[mode].name, |
| 380 | k->mac[mode].name, |
| 381 | k->comp[mode].name); |
| 382 | } |
| 383 | choose_kex(k, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]); |
| 384 | choose_hostkeyalg(k, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS], |
| 385 | sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]); |
| 386 | for (i = 0; i < PROPOSAL_MAX; i++) { |
| 387 | xfree(cprop[i]); |
| 388 | xfree(sprop[i]); |
| 389 | } |
| 390 | need = 0; |
| 391 | for (mode = 0; mode < MODE_MAX; mode++) { |
| 392 | if (need < k->enc[mode].key_len) |
| 393 | need = k->enc[mode].key_len; |
| 394 | if (need < k->enc[mode].iv_len) |
| 395 | need = k->enc[mode].iv_len; |
| 396 | if (need < k->mac[mode].key_len) |
| 397 | need = k->mac[mode].key_len; |
| 398 | } |
| 399 | /* need runden? */ |
| 400 | #define WE_NEED 32 |
| 401 | k->we_need = WE_NEED; |
| 402 | k->we_need = need; |
| 403 | return k; |
| 404 | } |
| 405 | |
| 406 | int |
| 407 | kex_derive_keys(Kex *k, unsigned char *hash, BIGNUM *shared_secret) |
| 408 | { |
| 409 | int i; |
| 410 | int mode; |
| 411 | int ctos; |
| 412 | unsigned char *keys[NKEYS]; |
| 413 | |
| 414 | for (i = 0; i < NKEYS; i++) |
| 415 | keys[i] = derive_key('A'+i, k->we_need, hash, shared_secret); |
| 416 | |
| 417 | for (mode = 0; mode < MODE_MAX; mode++) { |
| 418 | ctos = (!k->server && mode == MODE_OUT) || (k->server && mode == MODE_IN); |
| 419 | k->enc[mode].iv = keys[ctos ? 0 : 1]; |
| 420 | k->enc[mode].key = keys[ctos ? 2 : 3]; |
| 421 | k->mac[mode].key = keys[ctos ? 4 : 5]; |
| 422 | } |
| 423 | return 0; |
| 424 | } |