1 /* $OpenBSD: kex.c,v 1.106 2015/04/17 13:25:52 djm Exp $ */ 2 /* 3 * Copyright (c) 2000, 2001 Markus Friedl. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 17 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 24 */ 25 26 #include "includes.h" 27 28 #include <sys/param.h> /* MAX roundup */ 29 30 #include <signal.h> 31 #include <stdarg.h> 32 #include <stdio.h> 33 #include <stdlib.h> 34 #include <string.h> 35 36 #ifdef WITH_OPENSSL 37 #include <openssl/crypto.h> 38 #endif 39 40 #include "ssh2.h" 41 #include "packet.h" 42 #include "compat.h" 43 #include "cipher.h" 44 #include "sshkey.h" 45 #include "kex.h" 46 #include "log.h" 47 #include "mac.h" 48 #include "match.h" 49 #include "misc.h" 50 #include "dispatch.h" 51 #include "monitor.h" 52 #include "roaming.h" 53 54 #include "ssherr.h" 55 #include "sshbuf.h" 56 #include "digest.h" 57 58 #if OPENSSL_VERSION_NUMBER >= 0x00907000L 59 # if defined(HAVE_EVP_SHA256) 60 # define evp_ssh_sha256 EVP_sha256 61 # else 62 extern const EVP_MD *evp_ssh_sha256(void); 63 # endif 64 #endif 65 66 /* prototype */ 67 static int kex_choose_conf(struct ssh *); 68 static int kex_input_newkeys(int, u_int32_t, void *); 69 70 struct kexalg { 71 char *name; 72 u_int type; 73 int ec_nid; 74 int hash_alg; 75 }; 76 static const struct kexalg kexalgs[] = { 77 #ifdef WITH_OPENSSL 78 { KEX_DH1, KEX_DH_GRP1_SHA1, 0, SSH_DIGEST_SHA1 }, 79 { KEX_DH14, KEX_DH_GRP14_SHA1, 0, SSH_DIGEST_SHA1 }, 80 { KEX_DHGEX_SHA1, KEX_DH_GEX_SHA1, 0, SSH_DIGEST_SHA1 }, 81 #ifdef HAVE_EVP_SHA256 82 { KEX_DHGEX_SHA256, KEX_DH_GEX_SHA256, 0, SSH_DIGEST_SHA256 }, 83 #endif /* HAVE_EVP_SHA256 */ 84 #ifdef OPENSSL_HAS_ECC 85 { KEX_ECDH_SHA2_NISTP256, KEX_ECDH_SHA2, 86 NID_X9_62_prime256v1, SSH_DIGEST_SHA256 }, 87 { KEX_ECDH_SHA2_NISTP384, KEX_ECDH_SHA2, NID_secp384r1, 88 SSH_DIGEST_SHA384 }, 89 # ifdef OPENSSL_HAS_NISTP521 90 { KEX_ECDH_SHA2_NISTP521, KEX_ECDH_SHA2, NID_secp521r1, 91 SSH_DIGEST_SHA512 }, 92 # endif /* OPENSSL_HAS_NISTP521 */ 93 #endif /* OPENSSL_HAS_ECC */ 94 #endif /* WITH_OPENSSL */ 95 #if defined(HAVE_EVP_SHA256) || !defined(WITH_OPENSSL) 96 { KEX_CURVE25519_SHA256, KEX_C25519_SHA256, 0, SSH_DIGEST_SHA256 }, 97 #endif /* HAVE_EVP_SHA256 || !WITH_OPENSSL */ 98 { NULL, -1, -1, -1}, 99 }; 100 101 char * 102 kex_alg_list(char sep) 103 { 104 char *ret = NULL, *tmp; 105 size_t nlen, rlen = 0; 106 const struct kexalg *k; 107 108 for (k = kexalgs; k->name != NULL; k++) { 109 if (ret != NULL) 110 ret[rlen++] = sep; 111 nlen = strlen(k->name); 112 if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) { 113 free(ret); 114 return NULL; 115 } 116 ret = tmp; 117 memcpy(ret + rlen, k->name, nlen + 1); 118 rlen += nlen; 119 } 120 return ret; 121 } 122 123 static const struct kexalg * 124 kex_alg_by_name(const char *name) 125 { 126 const struct kexalg *k; 127 128 for (k = kexalgs; k->name != NULL; k++) { 129 if (strcmp(k->name, name) == 0) 130 return k; 131 } 132 return NULL; 133 } 134 135 /* Validate KEX method name list */ 136 int 137 kex_names_valid(const char *names) 138 { 139 char *s, *cp, *p; 140 141 if (names == NULL || strcmp(names, "") == 0) 142 return 0; 143 if ((s = cp = strdup(names)) == NULL) 144 return 0; 145 for ((p = strsep(&cp, ",")); p && *p != '\0'; 146 (p = strsep(&cp, ","))) { 147 if (kex_alg_by_name(p) == NULL) { 148 error("Unsupported KEX algorithm \"%.100s\"", p); 149 free(s); 150 return 0; 151 } 152 } 153 debug3("kex names ok: [%s]", names); 154 free(s); 155 return 1; 156 } 157 158 /* put algorithm proposal into buffer */ 159 int 160 kex_prop2buf(struct sshbuf *b, char *proposal[PROPOSAL_MAX]) 161 { 162 u_int i; 163 int r; 164 165 sshbuf_reset(b); 166 167 /* 168 * add a dummy cookie, the cookie will be overwritten by 169 * kex_send_kexinit(), each time a kexinit is set 170 */ 171 for (i = 0; i < KEX_COOKIE_LEN; i++) { 172 if ((r = sshbuf_put_u8(b, 0)) != 0) 173 return r; 174 } 175 for (i = 0; i < PROPOSAL_MAX; i++) { 176 if ((r = sshbuf_put_cstring(b, proposal[i])) != 0) 177 return r; 178 } 179 if ((r = sshbuf_put_u8(b, 0)) != 0 || /* first_kex_packet_follows */ 180 (r = sshbuf_put_u32(b, 0)) != 0) /* uint32 reserved */ 181 return r; 182 return 0; 183 } 184 185 /* parse buffer and return algorithm proposal */ 186 int 187 kex_buf2prop(struct sshbuf *raw, int *first_kex_follows, char ***propp) 188 { 189 struct sshbuf *b = NULL; 190 u_char v; 191 u_int i; 192 char **proposal = NULL; 193 int r; 194 195 *propp = NULL; 196 if ((proposal = calloc(PROPOSAL_MAX, sizeof(char *))) == NULL) 197 return SSH_ERR_ALLOC_FAIL; 198 if ((b = sshbuf_fromb(raw)) == NULL) { 199 r = SSH_ERR_ALLOC_FAIL; 200 goto out; 201 } 202 if ((r = sshbuf_consume(b, KEX_COOKIE_LEN)) != 0) /* skip cookie */ 203 goto out; 204 /* extract kex init proposal strings */ 205 for (i = 0; i < PROPOSAL_MAX; i++) { 206 if ((r = sshbuf_get_cstring(b, &(proposal[i]), NULL)) != 0) 207 goto out; 208 debug2("kex_parse_kexinit: %s", proposal[i]); 209 } 210 /* first kex follows / reserved */ 211 if ((r = sshbuf_get_u8(b, &v)) != 0 || 212 (r = sshbuf_get_u32(b, &i)) != 0) 213 goto out; 214 if (first_kex_follows != NULL) 215 *first_kex_follows = i; 216 debug2("kex_parse_kexinit: first_kex_follows %d ", v); 217 debug2("kex_parse_kexinit: reserved %u ", i); 218 r = 0; 219 *propp = proposal; 220 out: 221 if (r != 0 && proposal != NULL) 222 kex_prop_free(proposal); 223 sshbuf_free(b); 224 return r; 225 } 226 227 void 228 kex_prop_free(char **proposal) 229 { 230 u_int i; 231 232 if (proposal == NULL) 233 return; 234 for (i = 0; i < PROPOSAL_MAX; i++) 235 free(proposal[i]); 236 free(proposal); 237 } 238 239 /* ARGSUSED */ 240 static int 241 kex_protocol_error(int type, u_int32_t seq, void *ctxt) 242 { 243 error("Hm, kex protocol error: type %d seq %u", type, seq); 244 return 0; 245 } 246 247 static void 248 kex_reset_dispatch(struct ssh *ssh) 249 { 250 ssh_dispatch_range(ssh, SSH2_MSG_TRANSPORT_MIN, 251 SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error); 252 ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit); 253 } 254 255 int 256 kex_send_newkeys(struct ssh *ssh) 257 { 258 int r; 259 260 kex_reset_dispatch(ssh); 261 if ((r = sshpkt_start(ssh, SSH2_MSG_NEWKEYS)) != 0 || 262 (r = sshpkt_send(ssh)) != 0) 263 return r; 264 debug("SSH2_MSG_NEWKEYS sent"); 265 debug("expecting SSH2_MSG_NEWKEYS"); 266 ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_input_newkeys); 267 return 0; 268 } 269 270 static int 271 kex_input_newkeys(int type, u_int32_t seq, void *ctxt) 272 { 273 struct ssh *ssh = ctxt; 274 struct kex *kex = ssh->kex; 275 int r; 276 277 debug("SSH2_MSG_NEWKEYS received"); 278 ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_protocol_error); 279 if ((r = sshpkt_get_end(ssh)) != 0) 280 return r; 281 kex->done = 1; 282 sshbuf_reset(kex->peer); 283 /* sshbuf_reset(kex->my); */ 284 kex->flags &= ~KEX_INIT_SENT; 285 free(kex->name); 286 kex->name = NULL; 287 return 0; 288 } 289 290 int 291 kex_send_kexinit(struct ssh *ssh) 292 { 293 u_char *cookie; 294 struct kex *kex = ssh->kex; 295 int r; 296 297 if (kex == NULL) 298 return SSH_ERR_INTERNAL_ERROR; 299 if (kex->flags & KEX_INIT_SENT) 300 return 0; 301 kex->done = 0; 302 303 /* generate a random cookie */ 304 if (sshbuf_len(kex->my) < KEX_COOKIE_LEN) 305 return SSH_ERR_INVALID_FORMAT; 306 if ((cookie = sshbuf_mutable_ptr(kex->my)) == NULL) 307 return SSH_ERR_INTERNAL_ERROR; 308 arc4random_buf(cookie, KEX_COOKIE_LEN); 309 310 if ((r = sshpkt_start(ssh, SSH2_MSG_KEXINIT)) != 0 || 311 (r = sshpkt_putb(ssh, kex->my)) != 0 || 312 (r = sshpkt_send(ssh)) != 0) 313 return r; 314 debug("SSH2_MSG_KEXINIT sent"); 315 kex->flags |= KEX_INIT_SENT; 316 return 0; 317 } 318 319 /* ARGSUSED */ 320 int 321 kex_input_kexinit(int type, u_int32_t seq, void *ctxt) 322 { 323 struct ssh *ssh = ctxt; 324 struct kex *kex = ssh->kex; 325 const u_char *ptr; 326 u_int i; 327 size_t dlen; 328 int r; 329 330 debug("SSH2_MSG_KEXINIT received"); 331 if (kex == NULL) 332 return SSH_ERR_INVALID_ARGUMENT; 333 334 ptr = sshpkt_ptr(ssh, &dlen); 335 if ((r = sshbuf_put(kex->peer, ptr, dlen)) != 0) 336 return r; 337 338 /* discard packet */ 339 for (i = 0; i < KEX_COOKIE_LEN; i++) 340 if ((r = sshpkt_get_u8(ssh, NULL)) != 0) 341 return r; 342 for (i = 0; i < PROPOSAL_MAX; i++) 343 if ((r = sshpkt_get_string(ssh, NULL, NULL)) != 0) 344 return r; 345 /* 346 * XXX RFC4253 sec 7: "each side MAY guess" - currently no supported 347 * KEX method has the server move first, but a server might be using 348 * a custom method or one that we otherwise don't support. We should 349 * be prepared to remember first_kex_follows here so we can eat a 350 * packet later. 351 * XXX2 - RFC4253 is kind of ambiguous on what first_kex_follows means 352 * for cases where the server *doesn't* go first. I guess we should 353 * ignore it when it is set for these cases, which is what we do now. 354 */ 355 if ((r = sshpkt_get_u8(ssh, NULL)) != 0 || /* first_kex_follows */ 356 (r = sshpkt_get_u32(ssh, NULL)) != 0 || /* reserved */ 357 (r = sshpkt_get_end(ssh)) != 0) 358 return r; 359 360 if (!(kex->flags & KEX_INIT_SENT)) 361 if ((r = kex_send_kexinit(ssh)) != 0) 362 return r; 363 if ((r = kex_choose_conf(ssh)) != 0) 364 return r; 365 366 if (kex->kex_type < KEX_MAX && kex->kex[kex->kex_type] != NULL) 367 return (kex->kex[kex->kex_type])(ssh); 368 369 return SSH_ERR_INTERNAL_ERROR; 370 } 371 372 int 373 kex_new(struct ssh *ssh, char *proposal[PROPOSAL_MAX], struct kex **kexp) 374 { 375 struct kex *kex; 376 int r; 377 378 *kexp = NULL; 379 if ((kex = calloc(1, sizeof(*kex))) == NULL) 380 return SSH_ERR_ALLOC_FAIL; 381 if ((kex->peer = sshbuf_new()) == NULL || 382 (kex->my = sshbuf_new()) == NULL) { 383 r = SSH_ERR_ALLOC_FAIL; 384 goto out; 385 } 386 if ((r = kex_prop2buf(kex->my, proposal)) != 0) 387 goto out; 388 kex->done = 0; 389 kex_reset_dispatch(ssh); 390 r = 0; 391 *kexp = kex; 392 out: 393 if (r != 0) 394 kex_free(kex); 395 return r; 396 } 397 398 void 399 kex_free_newkeys(struct newkeys *newkeys) 400 { 401 if (newkeys == NULL) 402 return; 403 if (newkeys->enc.key) { 404 explicit_bzero(newkeys->enc.key, newkeys->enc.key_len); 405 free(newkeys->enc.key); 406 newkeys->enc.key = NULL; 407 } 408 if (newkeys->enc.iv) { 409 explicit_bzero(newkeys->enc.iv, newkeys->enc.block_size); 410 free(newkeys->enc.iv); 411 newkeys->enc.iv = NULL; 412 } 413 free(newkeys->enc.name); 414 explicit_bzero(&newkeys->enc, sizeof(newkeys->enc)); 415 free(newkeys->comp.name); 416 explicit_bzero(&newkeys->comp, sizeof(newkeys->comp)); 417 mac_clear(&newkeys->mac); 418 if (newkeys->mac.key) { 419 explicit_bzero(newkeys->mac.key, newkeys->mac.key_len); 420 free(newkeys->mac.key); 421 newkeys->mac.key = NULL; 422 } 423 free(newkeys->mac.name); 424 explicit_bzero(&newkeys->mac, sizeof(newkeys->mac)); 425 explicit_bzero(newkeys, sizeof(*newkeys)); 426 free(newkeys); 427 } 428 429 void 430 kex_free(struct kex *kex) 431 { 432 u_int mode; 433 434 #ifdef WITH_OPENSSL 435 if (kex->dh) 436 DH_free(kex->dh); 437 #ifdef OPENSSL_HAS_ECC 438 if (kex->ec_client_key) 439 EC_KEY_free(kex->ec_client_key); 440 #endif /* OPENSSL_HAS_ECC */ 441 #endif /* WITH_OPENSSL */ 442 for (mode = 0; mode < MODE_MAX; mode++) { 443 kex_free_newkeys(kex->newkeys[mode]); 444 kex->newkeys[mode] = NULL; 445 } 446 sshbuf_free(kex->peer); 447 sshbuf_free(kex->my); 448 free(kex->session_id); 449 free(kex->client_version_string); 450 free(kex->server_version_string); 451 free(kex); 452 } 453 454 int 455 kex_setup(struct ssh *ssh, char *proposal[PROPOSAL_MAX]) 456 { 457 int r; 458 459 if ((r = kex_new(ssh, proposal, &ssh->kex)) != 0) 460 return r; 461 if ((r = kex_send_kexinit(ssh)) != 0) { /* we start */ 462 kex_free(ssh->kex); 463 ssh->kex = NULL; 464 return r; 465 } 466 return 0; 467 } 468 469 static int 470 choose_enc(struct sshenc *enc, char *client, char *server) 471 { 472 char *name = match_list(client, server, NULL); 473 474 if (name == NULL) 475 return SSH_ERR_NO_CIPHER_ALG_MATCH; 476 if ((enc->cipher = cipher_by_name(name)) == NULL) 477 return SSH_ERR_INTERNAL_ERROR; 478 enc->name = name; 479 enc->enabled = 0; 480 enc->iv = NULL; 481 enc->iv_len = cipher_ivlen(enc->cipher); 482 enc->key = NULL; 483 enc->key_len = cipher_keylen(enc->cipher); 484 enc->block_size = cipher_blocksize(enc->cipher); 485 return 0; 486 } 487 488 static int 489 choose_mac(struct ssh *ssh, struct sshmac *mac, char *client, char *server) 490 { 491 char *name = match_list(client, server, NULL); 492 493 if (name == NULL) 494 return SSH_ERR_NO_MAC_ALG_MATCH; 495 if (mac_setup(mac, name) < 0) 496 return SSH_ERR_INTERNAL_ERROR; 497 /* truncate the key */ 498 if (ssh->compat & SSH_BUG_HMAC) 499 mac->key_len = 16; 500 mac->name = name; 501 mac->key = NULL; 502 mac->enabled = 0; 503 return 0; 504 } 505 506 static int 507 choose_comp(struct sshcomp *comp, char *client, char *server) 508 { 509 char *name = match_list(client, server, NULL); 510 511 if (name == NULL) 512 return SSH_ERR_NO_COMPRESS_ALG_MATCH; 513 if (strcmp(name, "zlib@openssh.com") == 0) { 514 comp->type = COMP_DELAYED; 515 } else if (strcmp(name, "zlib") == 0) { 516 comp->type = COMP_ZLIB; 517 } else if (strcmp(name, "none") == 0) { 518 comp->type = COMP_NONE; 519 } else { 520 return SSH_ERR_INTERNAL_ERROR; 521 } 522 comp->name = name; 523 return 0; 524 } 525 526 static int 527 choose_kex(struct kex *k, char *client, char *server) 528 { 529 const struct kexalg *kexalg; 530 531 k->name = match_list(client, server, NULL); 532 533 if (k->name == NULL) 534 return SSH_ERR_NO_KEX_ALG_MATCH; 535 if ((kexalg = kex_alg_by_name(k->name)) == NULL) 536 return SSH_ERR_INTERNAL_ERROR; 537 k->kex_type = kexalg->type; 538 k->hash_alg = kexalg->hash_alg; 539 k->ec_nid = kexalg->ec_nid; 540 return 0; 541 } 542 543 static int 544 choose_hostkeyalg(struct kex *k, char *client, char *server) 545 { 546 char *hostkeyalg = match_list(client, server, NULL); 547 548 if (hostkeyalg == NULL) 549 return SSH_ERR_NO_HOSTKEY_ALG_MATCH; 550 k->hostkey_type = sshkey_type_from_name(hostkeyalg); 551 if (k->hostkey_type == KEY_UNSPEC) 552 return SSH_ERR_INTERNAL_ERROR; 553 k->hostkey_nid = sshkey_ecdsa_nid_from_name(hostkeyalg); 554 free(hostkeyalg); 555 return 0; 556 } 557 558 static int 559 proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX]) 560 { 561 static int check[] = { 562 PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1 563 }; 564 int *idx; 565 char *p; 566 567 for (idx = &check[0]; *idx != -1; idx++) { 568 if ((p = strchr(my[*idx], ',')) != NULL) 569 *p = '\0'; 570 if ((p = strchr(peer[*idx], ',')) != NULL) 571 *p = '\0'; 572 if (strcmp(my[*idx], peer[*idx]) != 0) { 573 debug2("proposal mismatch: my %s peer %s", 574 my[*idx], peer[*idx]); 575 return (0); 576 } 577 } 578 debug2("proposals match"); 579 return (1); 580 } 581 582 static int 583 kex_choose_conf(struct ssh *ssh) 584 { 585 struct kex *kex = ssh->kex; 586 struct newkeys *newkeys; 587 char **my = NULL, **peer = NULL; 588 char **cprop, **sprop; 589 int nenc, nmac, ncomp; 590 u_int mode, ctos, need, dh_need, authlen; 591 int r, first_kex_follows; 592 593 if ((r = kex_buf2prop(kex->my, NULL, &my)) != 0 || 594 (r = kex_buf2prop(kex->peer, &first_kex_follows, &peer)) != 0) 595 goto out; 596 597 if (kex->server) { 598 cprop=peer; 599 sprop=my; 600 } else { 601 cprop=my; 602 sprop=peer; 603 } 604 605 /* Check whether server offers roaming */ 606 if (!kex->server) { 607 char *roaming = match_list(KEX_RESUME, 608 peer[PROPOSAL_KEX_ALGS], NULL); 609 610 if (roaming) { 611 kex->roaming = 1; 612 free(roaming); 613 } 614 } 615 616 /* Algorithm Negotiation */ 617 for (mode = 0; mode < MODE_MAX; mode++) { 618 if ((newkeys = calloc(1, sizeof(*newkeys))) == NULL) { 619 r = SSH_ERR_ALLOC_FAIL; 620 goto out; 621 } 622 kex->newkeys[mode] = newkeys; 623 ctos = (!kex->server && mode == MODE_OUT) || 624 (kex->server && mode == MODE_IN); 625 nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC; 626 nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC; 627 ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC; 628 if ((r = choose_enc(&newkeys->enc, cprop[nenc], 629 sprop[nenc])) != 0) 630 goto out; 631 authlen = cipher_authlen(newkeys->enc.cipher); 632 /* ignore mac for authenticated encryption */ 633 if (authlen == 0 && 634 (r = choose_mac(ssh, &newkeys->mac, cprop[nmac], 635 sprop[nmac])) != 0) 636 goto out; 637 if ((r = choose_comp(&newkeys->comp, cprop[ncomp], 638 sprop[ncomp])) != 0) 639 goto out; 640 debug("kex: %s %s %s %s", 641 ctos ? "client->server" : "server->client", 642 newkeys->enc.name, 643 authlen == 0 ? newkeys->mac.name : "<implicit>", 644 newkeys->comp.name); 645 } 646 if ((r = choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], 647 sprop[PROPOSAL_KEX_ALGS])) != 0 || 648 (r = choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS], 649 sprop[PROPOSAL_SERVER_HOST_KEY_ALGS])) != 0) 650 goto out; 651 need = dh_need = 0; 652 for (mode = 0; mode < MODE_MAX; mode++) { 653 newkeys = kex->newkeys[mode]; 654 need = MAX(need, newkeys->enc.key_len); 655 need = MAX(need, newkeys->enc.block_size); 656 need = MAX(need, newkeys->enc.iv_len); 657 need = MAX(need, newkeys->mac.key_len); 658 dh_need = MAX(dh_need, cipher_seclen(newkeys->enc.cipher)); 659 dh_need = MAX(dh_need, newkeys->enc.block_size); 660 dh_need = MAX(dh_need, newkeys->enc.iv_len); 661 dh_need = MAX(dh_need, newkeys->mac.key_len); 662 } 663 /* XXX need runden? */ 664 kex->we_need = need; 665 kex->dh_need = dh_need; 666 667 /* ignore the next message if the proposals do not match */ 668 if (first_kex_follows && !proposals_match(my, peer) && 669 !(ssh->compat & SSH_BUG_FIRSTKEX)) 670 ssh->dispatch_skip_packets = 1; 671 r = 0; 672 out: 673 kex_prop_free(my); 674 kex_prop_free(peer); 675 return r; 676 } 677 678 static int 679 derive_key(struct ssh *ssh, int id, u_int need, u_char *hash, u_int hashlen, 680 const struct sshbuf *shared_secret, u_char **keyp) 681 { 682 struct kex *kex = ssh->kex; 683 struct ssh_digest_ctx *hashctx = NULL; 684 char c = id; 685 u_int have; 686 size_t mdsz; 687 u_char *digest; 688 int r; 689 690 if ((mdsz = ssh_digest_bytes(kex->hash_alg)) == 0) 691 return SSH_ERR_INVALID_ARGUMENT; 692 if ((digest = calloc(1, roundup(need, mdsz))) == NULL) { 693 r = SSH_ERR_ALLOC_FAIL; 694 goto out; 695 } 696 697 /* K1 = HASH(K || H || "A" || session_id) */ 698 if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL || 699 ssh_digest_update_buffer(hashctx, shared_secret) != 0 || 700 ssh_digest_update(hashctx, hash, hashlen) != 0 || 701 ssh_digest_update(hashctx, &c, 1) != 0 || 702 ssh_digest_update(hashctx, kex->session_id, 703 kex->session_id_len) != 0 || 704 ssh_digest_final(hashctx, digest, mdsz) != 0) { 705 r = SSH_ERR_LIBCRYPTO_ERROR; 706 goto out; 707 } 708 ssh_digest_free(hashctx); 709 hashctx = NULL; 710 711 /* 712 * expand key: 713 * Kn = HASH(K || H || K1 || K2 || ... || Kn-1) 714 * Key = K1 || K2 || ... || Kn 715 */ 716 for (have = mdsz; need > have; have += mdsz) { 717 if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL || 718 ssh_digest_update_buffer(hashctx, shared_secret) != 0 || 719 ssh_digest_update(hashctx, hash, hashlen) != 0 || 720 ssh_digest_update(hashctx, digest, have) != 0 || 721 ssh_digest_final(hashctx, digest + have, mdsz) != 0) { 722 r = SSH_ERR_LIBCRYPTO_ERROR; 723 goto out; 724 } 725 ssh_digest_free(hashctx); 726 hashctx = NULL; 727 } 728 #ifdef DEBUG_KEX 729 fprintf(stderr, "key '%c'== ", c); 730 dump_digest("key", digest, need); 731 #endif 732 *keyp = digest; 733 digest = NULL; 734 r = 0; 735 out: 736 if (digest) 737 free(digest); 738 ssh_digest_free(hashctx); 739 return r; 740 } 741 742 #define NKEYS 6 743 int 744 kex_derive_keys(struct ssh *ssh, u_char *hash, u_int hashlen, 745 const struct sshbuf *shared_secret) 746 { 747 struct kex *kex = ssh->kex; 748 u_char *keys[NKEYS]; 749 u_int i, j, mode, ctos; 750 int r; 751 752 for (i = 0; i < NKEYS; i++) { 753 if ((r = derive_key(ssh, 'A'+i, kex->we_need, hash, hashlen, 754 shared_secret, &keys[i])) != 0) { 755 for (j = 0; j < i; j++) 756 free(keys[j]); 757 return r; 758 } 759 } 760 for (mode = 0; mode < MODE_MAX; mode++) { 761 ctos = (!kex->server && mode == MODE_OUT) || 762 (kex->server && mode == MODE_IN); 763 kex->newkeys[mode]->enc.iv = keys[ctos ? 0 : 1]; 764 kex->newkeys[mode]->enc.key = keys[ctos ? 2 : 3]; 765 kex->newkeys[mode]->mac.key = keys[ctos ? 4 : 5]; 766 } 767 return 0; 768 } 769 770 #ifdef WITH_OPENSSL 771 int 772 kex_derive_keys_bn(struct ssh *ssh, u_char *hash, u_int hashlen, 773 const BIGNUM *secret) 774 { 775 struct sshbuf *shared_secret; 776 int r; 777 778 if ((shared_secret = sshbuf_new()) == NULL) 779 return SSH_ERR_ALLOC_FAIL; 780 if ((r = sshbuf_put_bignum2(shared_secret, secret)) == 0) 781 r = kex_derive_keys(ssh, hash, hashlen, shared_secret); 782 sshbuf_free(shared_secret); 783 return r; 784 } 785 #endif 786 787 #ifdef WITH_SSH1 788 int 789 derive_ssh1_session_id(BIGNUM *host_modulus, BIGNUM *server_modulus, 790 u_int8_t cookie[8], u_int8_t id[16]) 791 { 792 u_int8_t hbuf[2048], sbuf[2048], obuf[SSH_DIGEST_MAX_LENGTH]; 793 struct ssh_digest_ctx *hashctx = NULL; 794 size_t hlen, slen; 795 int r; 796 797 hlen = BN_num_bytes(host_modulus); 798 slen = BN_num_bytes(server_modulus); 799 if (hlen < (512 / 8) || (u_int)hlen > sizeof(hbuf) || 800 slen < (512 / 8) || (u_int)slen > sizeof(sbuf)) 801 return SSH_ERR_KEY_BITS_MISMATCH; 802 if (BN_bn2bin(host_modulus, hbuf) <= 0 || 803 BN_bn2bin(server_modulus, sbuf) <= 0) { 804 r = SSH_ERR_LIBCRYPTO_ERROR; 805 goto out; 806 } 807 if ((hashctx = ssh_digest_start(SSH_DIGEST_MD5)) == NULL) { 808 r = SSH_ERR_ALLOC_FAIL; 809 goto out; 810 } 811 if (ssh_digest_update(hashctx, hbuf, hlen) != 0 || 812 ssh_digest_update(hashctx, sbuf, slen) != 0 || 813 ssh_digest_update(hashctx, cookie, 8) != 0 || 814 ssh_digest_final(hashctx, obuf, sizeof(obuf)) != 0) { 815 r = SSH_ERR_LIBCRYPTO_ERROR; 816 goto out; 817 } 818 memcpy(id, obuf, ssh_digest_bytes(SSH_DIGEST_MD5)); 819 r = 0; 820 out: 821 ssh_digest_free(hashctx); 822 explicit_bzero(hbuf, sizeof(hbuf)); 823 explicit_bzero(sbuf, sizeof(sbuf)); 824 explicit_bzero(obuf, sizeof(obuf)); 825 return r; 826 } 827 #endif 828 829 #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH) 830 void 831 dump_digest(char *msg, u_char *digest, int len) 832 { 833 fprintf(stderr, "%s\n", msg); 834 sshbuf_dump_data(digest, len, stderr); 835 } 836 #endif 837