1 /* $OpenBSD: kex.c,v 1.105 2015/01/30 00:22:25 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 for (i = 0; i < PROPOSAL_MAX; i++) 233 free(proposal[i]); 234 free(proposal); 235 } 236 237 /* ARGSUSED */ 238 static int 239 kex_protocol_error(int type, u_int32_t seq, void *ctxt) 240 { 241 error("Hm, kex protocol error: type %d seq %u", type, seq); 242 return 0; 243 } 244 245 static void 246 kex_reset_dispatch(struct ssh *ssh) 247 { 248 ssh_dispatch_range(ssh, SSH2_MSG_TRANSPORT_MIN, 249 SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error); 250 ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit); 251 } 252 253 int 254 kex_send_newkeys(struct ssh *ssh) 255 { 256 int r; 257 258 kex_reset_dispatch(ssh); 259 if ((r = sshpkt_start(ssh, SSH2_MSG_NEWKEYS)) != 0 || 260 (r = sshpkt_send(ssh)) != 0) 261 return r; 262 debug("SSH2_MSG_NEWKEYS sent"); 263 debug("expecting SSH2_MSG_NEWKEYS"); 264 ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_input_newkeys); 265 return 0; 266 } 267 268 static int 269 kex_input_newkeys(int type, u_int32_t seq, void *ctxt) 270 { 271 struct ssh *ssh = ctxt; 272 struct kex *kex = ssh->kex; 273 int r; 274 275 debug("SSH2_MSG_NEWKEYS received"); 276 ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_protocol_error); 277 if ((r = sshpkt_get_end(ssh)) != 0) 278 return r; 279 kex->done = 1; 280 sshbuf_reset(kex->peer); 281 /* sshbuf_reset(kex->my); */ 282 kex->flags &= ~KEX_INIT_SENT; 283 free(kex->name); 284 kex->name = NULL; 285 return 0; 286 } 287 288 int 289 kex_send_kexinit(struct ssh *ssh) 290 { 291 u_char *cookie; 292 struct kex *kex = ssh->kex; 293 int r; 294 295 if (kex == NULL) 296 return SSH_ERR_INTERNAL_ERROR; 297 if (kex->flags & KEX_INIT_SENT) 298 return 0; 299 kex->done = 0; 300 301 /* generate a random cookie */ 302 if (sshbuf_len(kex->my) < KEX_COOKIE_LEN) 303 return SSH_ERR_INVALID_FORMAT; 304 if ((cookie = sshbuf_mutable_ptr(kex->my)) == NULL) 305 return SSH_ERR_INTERNAL_ERROR; 306 arc4random_buf(cookie, KEX_COOKIE_LEN); 307 308 if ((r = sshpkt_start(ssh, SSH2_MSG_KEXINIT)) != 0 || 309 (r = sshpkt_putb(ssh, kex->my)) != 0 || 310 (r = sshpkt_send(ssh)) != 0) 311 return r; 312 debug("SSH2_MSG_KEXINIT sent"); 313 kex->flags |= KEX_INIT_SENT; 314 return 0; 315 } 316 317 /* ARGSUSED */ 318 int 319 kex_input_kexinit(int type, u_int32_t seq, void *ctxt) 320 { 321 struct ssh *ssh = ctxt; 322 struct kex *kex = ssh->kex; 323 const u_char *ptr; 324 u_int i; 325 size_t dlen; 326 int r; 327 328 debug("SSH2_MSG_KEXINIT received"); 329 if (kex == NULL) 330 return SSH_ERR_INVALID_ARGUMENT; 331 332 ptr = sshpkt_ptr(ssh, &dlen); 333 if ((r = sshbuf_put(kex->peer, ptr, dlen)) != 0) 334 return r; 335 336 /* discard packet */ 337 for (i = 0; i < KEX_COOKIE_LEN; i++) 338 if ((r = sshpkt_get_u8(ssh, NULL)) != 0) 339 return r; 340 for (i = 0; i < PROPOSAL_MAX; i++) 341 if ((r = sshpkt_get_string(ssh, NULL, NULL)) != 0) 342 return r; 343 /* 344 * XXX RFC4253 sec 7: "each side MAY guess" - currently no supported 345 * KEX method has the server move first, but a server might be using 346 * a custom method or one that we otherwise don't support. We should 347 * be prepared to remember first_kex_follows here so we can eat a 348 * packet later. 349 * XXX2 - RFC4253 is kind of ambiguous on what first_kex_follows means 350 * for cases where the server *doesn't* go first. I guess we should 351 * ignore it when it is set for these cases, which is what we do now. 352 */ 353 if ((r = sshpkt_get_u8(ssh, NULL)) != 0 || /* first_kex_follows */ 354 (r = sshpkt_get_u32(ssh, NULL)) != 0 || /* reserved */ 355 (r = sshpkt_get_end(ssh)) != 0) 356 return r; 357 358 if (!(kex->flags & KEX_INIT_SENT)) 359 if ((r = kex_send_kexinit(ssh)) != 0) 360 return r; 361 if ((r = kex_choose_conf(ssh)) != 0) 362 return r; 363 364 if (kex->kex_type < KEX_MAX && kex->kex[kex->kex_type] != NULL) 365 return (kex->kex[kex->kex_type])(ssh); 366 367 return SSH_ERR_INTERNAL_ERROR; 368 } 369 370 int 371 kex_new(struct ssh *ssh, char *proposal[PROPOSAL_MAX], struct kex **kexp) 372 { 373 struct kex *kex; 374 int r; 375 376 *kexp = NULL; 377 if ((kex = calloc(1, sizeof(*kex))) == NULL) 378 return SSH_ERR_ALLOC_FAIL; 379 if ((kex->peer = sshbuf_new()) == NULL || 380 (kex->my = sshbuf_new()) == NULL) { 381 r = SSH_ERR_ALLOC_FAIL; 382 goto out; 383 } 384 if ((r = kex_prop2buf(kex->my, proposal)) != 0) 385 goto out; 386 kex->done = 0; 387 kex_reset_dispatch(ssh); 388 r = 0; 389 *kexp = kex; 390 out: 391 if (r != 0) 392 kex_free(kex); 393 return r; 394 } 395 396 void 397 kex_free_newkeys(struct newkeys *newkeys) 398 { 399 if (newkeys == NULL) 400 return; 401 if (newkeys->enc.key) { 402 explicit_bzero(newkeys->enc.key, newkeys->enc.key_len); 403 free(newkeys->enc.key); 404 newkeys->enc.key = NULL; 405 } 406 if (newkeys->enc.iv) { 407 explicit_bzero(newkeys->enc.iv, newkeys->enc.block_size); 408 free(newkeys->enc.iv); 409 newkeys->enc.iv = NULL; 410 } 411 free(newkeys->enc.name); 412 explicit_bzero(&newkeys->enc, sizeof(newkeys->enc)); 413 free(newkeys->comp.name); 414 explicit_bzero(&newkeys->comp, sizeof(newkeys->comp)); 415 mac_clear(&newkeys->mac); 416 if (newkeys->mac.key) { 417 explicit_bzero(newkeys->mac.key, newkeys->mac.key_len); 418 free(newkeys->mac.key); 419 newkeys->mac.key = NULL; 420 } 421 free(newkeys->mac.name); 422 explicit_bzero(&newkeys->mac, sizeof(newkeys->mac)); 423 explicit_bzero(newkeys, sizeof(*newkeys)); 424 free(newkeys); 425 } 426 427 void 428 kex_free(struct kex *kex) 429 { 430 u_int mode; 431 432 #ifdef WITH_OPENSSL 433 if (kex->dh) 434 DH_free(kex->dh); 435 #ifdef OPENSSL_HAS_ECC 436 if (kex->ec_client_key) 437 EC_KEY_free(kex->ec_client_key); 438 #endif /* OPENSSL_HAS_ECC */ 439 #endif /* WITH_OPENSSL */ 440 for (mode = 0; mode < MODE_MAX; mode++) { 441 kex_free_newkeys(kex->newkeys[mode]); 442 kex->newkeys[mode] = NULL; 443 } 444 sshbuf_free(kex->peer); 445 sshbuf_free(kex->my); 446 free(kex->session_id); 447 free(kex->client_version_string); 448 free(kex->server_version_string); 449 free(kex); 450 } 451 452 int 453 kex_setup(struct ssh *ssh, char *proposal[PROPOSAL_MAX]) 454 { 455 int r; 456 457 if ((r = kex_new(ssh, proposal, &ssh->kex)) != 0) 458 return r; 459 if ((r = kex_send_kexinit(ssh)) != 0) { /* we start */ 460 kex_free(ssh->kex); 461 ssh->kex = NULL; 462 return r; 463 } 464 return 0; 465 } 466 467 static int 468 choose_enc(struct sshenc *enc, char *client, char *server) 469 { 470 char *name = match_list(client, server, NULL); 471 472 if (name == NULL) 473 return SSH_ERR_NO_CIPHER_ALG_MATCH; 474 if ((enc->cipher = cipher_by_name(name)) == NULL) 475 return SSH_ERR_INTERNAL_ERROR; 476 enc->name = name; 477 enc->enabled = 0; 478 enc->iv = NULL; 479 enc->iv_len = cipher_ivlen(enc->cipher); 480 enc->key = NULL; 481 enc->key_len = cipher_keylen(enc->cipher); 482 enc->block_size = cipher_blocksize(enc->cipher); 483 return 0; 484 } 485 486 static int 487 choose_mac(struct ssh *ssh, struct sshmac *mac, char *client, char *server) 488 { 489 char *name = match_list(client, server, NULL); 490 491 if (name == NULL) 492 return SSH_ERR_NO_MAC_ALG_MATCH; 493 if (mac_setup(mac, name) < 0) 494 return SSH_ERR_INTERNAL_ERROR; 495 /* truncate the key */ 496 if (ssh->compat & SSH_BUG_HMAC) 497 mac->key_len = 16; 498 mac->name = name; 499 mac->key = NULL; 500 mac->enabled = 0; 501 return 0; 502 } 503 504 static int 505 choose_comp(struct sshcomp *comp, char *client, char *server) 506 { 507 char *name = match_list(client, server, NULL); 508 509 if (name == NULL) 510 return SSH_ERR_NO_COMPRESS_ALG_MATCH; 511 if (strcmp(name, "zlib@openssh.com") == 0) { 512 comp->type = COMP_DELAYED; 513 } else if (strcmp(name, "zlib") == 0) { 514 comp->type = COMP_ZLIB; 515 } else if (strcmp(name, "none") == 0) { 516 comp->type = COMP_NONE; 517 } else { 518 return SSH_ERR_INTERNAL_ERROR; 519 } 520 comp->name = name; 521 return 0; 522 } 523 524 static int 525 choose_kex(struct kex *k, char *client, char *server) 526 { 527 const struct kexalg *kexalg; 528 529 k->name = match_list(client, server, NULL); 530 531 if (k->name == NULL) 532 return SSH_ERR_NO_KEX_ALG_MATCH; 533 if ((kexalg = kex_alg_by_name(k->name)) == NULL) 534 return SSH_ERR_INTERNAL_ERROR; 535 k->kex_type = kexalg->type; 536 k->hash_alg = kexalg->hash_alg; 537 k->ec_nid = kexalg->ec_nid; 538 return 0; 539 } 540 541 static int 542 choose_hostkeyalg(struct kex *k, char *client, char *server) 543 { 544 char *hostkeyalg = match_list(client, server, NULL); 545 546 if (hostkeyalg == NULL) 547 return SSH_ERR_NO_HOSTKEY_ALG_MATCH; 548 k->hostkey_type = sshkey_type_from_name(hostkeyalg); 549 if (k->hostkey_type == KEY_UNSPEC) 550 return SSH_ERR_INTERNAL_ERROR; 551 k->hostkey_nid = sshkey_ecdsa_nid_from_name(hostkeyalg); 552 free(hostkeyalg); 553 return 0; 554 } 555 556 static int 557 proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX]) 558 { 559 static int check[] = { 560 PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1 561 }; 562 int *idx; 563 char *p; 564 565 for (idx = &check[0]; *idx != -1; idx++) { 566 if ((p = strchr(my[*idx], ',')) != NULL) 567 *p = '\0'; 568 if ((p = strchr(peer[*idx], ',')) != NULL) 569 *p = '\0'; 570 if (strcmp(my[*idx], peer[*idx]) != 0) { 571 debug2("proposal mismatch: my %s peer %s", 572 my[*idx], peer[*idx]); 573 return (0); 574 } 575 } 576 debug2("proposals match"); 577 return (1); 578 } 579 580 static int 581 kex_choose_conf(struct ssh *ssh) 582 { 583 struct kex *kex = ssh->kex; 584 struct newkeys *newkeys; 585 char **my = NULL, **peer = NULL; 586 char **cprop, **sprop; 587 int nenc, nmac, ncomp; 588 u_int mode, ctos, need, dh_need, authlen; 589 int r, first_kex_follows; 590 591 if ((r = kex_buf2prop(kex->my, NULL, &my)) != 0 || 592 (r = kex_buf2prop(kex->peer, &first_kex_follows, &peer)) != 0) 593 goto out; 594 595 if (kex->server) { 596 cprop=peer; 597 sprop=my; 598 } else { 599 cprop=my; 600 sprop=peer; 601 } 602 603 /* Check whether server offers roaming */ 604 if (!kex->server) { 605 char *roaming = match_list(KEX_RESUME, 606 peer[PROPOSAL_KEX_ALGS], NULL); 607 608 if (roaming) { 609 kex->roaming = 1; 610 free(roaming); 611 } 612 } 613 614 /* Algorithm Negotiation */ 615 for (mode = 0; mode < MODE_MAX; mode++) { 616 if ((newkeys = calloc(1, sizeof(*newkeys))) == NULL) { 617 r = SSH_ERR_ALLOC_FAIL; 618 goto out; 619 } 620 kex->newkeys[mode] = newkeys; 621 ctos = (!kex->server && mode == MODE_OUT) || 622 (kex->server && mode == MODE_IN); 623 nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC; 624 nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC; 625 ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC; 626 if ((r = choose_enc(&newkeys->enc, cprop[nenc], 627 sprop[nenc])) != 0) 628 goto out; 629 authlen = cipher_authlen(newkeys->enc.cipher); 630 /* ignore mac for authenticated encryption */ 631 if (authlen == 0 && 632 (r = choose_mac(ssh, &newkeys->mac, cprop[nmac], 633 sprop[nmac])) != 0) 634 goto out; 635 if ((r = choose_comp(&newkeys->comp, cprop[ncomp], 636 sprop[ncomp])) != 0) 637 goto out; 638 debug("kex: %s %s %s %s", 639 ctos ? "client->server" : "server->client", 640 newkeys->enc.name, 641 authlen == 0 ? newkeys->mac.name : "<implicit>", 642 newkeys->comp.name); 643 } 644 if ((r = choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], 645 sprop[PROPOSAL_KEX_ALGS])) != 0 || 646 (r = choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS], 647 sprop[PROPOSAL_SERVER_HOST_KEY_ALGS])) != 0) 648 goto out; 649 need = dh_need = 0; 650 for (mode = 0; mode < MODE_MAX; mode++) { 651 newkeys = kex->newkeys[mode]; 652 need = MAX(need, newkeys->enc.key_len); 653 need = MAX(need, newkeys->enc.block_size); 654 need = MAX(need, newkeys->enc.iv_len); 655 need = MAX(need, newkeys->mac.key_len); 656 dh_need = MAX(dh_need, cipher_seclen(newkeys->enc.cipher)); 657 dh_need = MAX(dh_need, newkeys->enc.block_size); 658 dh_need = MAX(dh_need, newkeys->enc.iv_len); 659 dh_need = MAX(dh_need, newkeys->mac.key_len); 660 } 661 /* XXX need runden? */ 662 kex->we_need = need; 663 kex->dh_need = dh_need; 664 665 /* ignore the next message if the proposals do not match */ 666 if (first_kex_follows && !proposals_match(my, peer) && 667 !(ssh->compat & SSH_BUG_FIRSTKEX)) 668 ssh->dispatch_skip_packets = 1; 669 r = 0; 670 out: 671 kex_prop_free(my); 672 kex_prop_free(peer); 673 return r; 674 } 675 676 static int 677 derive_key(struct ssh *ssh, int id, u_int need, u_char *hash, u_int hashlen, 678 const struct sshbuf *shared_secret, u_char **keyp) 679 { 680 struct kex *kex = ssh->kex; 681 struct ssh_digest_ctx *hashctx = NULL; 682 char c = id; 683 u_int have; 684 size_t mdsz; 685 u_char *digest; 686 int r; 687 688 if ((mdsz = ssh_digest_bytes(kex->hash_alg)) == 0) 689 return SSH_ERR_INVALID_ARGUMENT; 690 if ((digest = calloc(1, roundup(need, mdsz))) == NULL) { 691 r = SSH_ERR_ALLOC_FAIL; 692 goto out; 693 } 694 695 /* K1 = HASH(K || H || "A" || session_id) */ 696 if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL || 697 ssh_digest_update_buffer(hashctx, shared_secret) != 0 || 698 ssh_digest_update(hashctx, hash, hashlen) != 0 || 699 ssh_digest_update(hashctx, &c, 1) != 0 || 700 ssh_digest_update(hashctx, kex->session_id, 701 kex->session_id_len) != 0 || 702 ssh_digest_final(hashctx, digest, mdsz) != 0) { 703 r = SSH_ERR_LIBCRYPTO_ERROR; 704 goto out; 705 } 706 ssh_digest_free(hashctx); 707 hashctx = NULL; 708 709 /* 710 * expand key: 711 * Kn = HASH(K || H || K1 || K2 || ... || Kn-1) 712 * Key = K1 || K2 || ... || Kn 713 */ 714 for (have = mdsz; need > have; have += mdsz) { 715 if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL || 716 ssh_digest_update_buffer(hashctx, shared_secret) != 0 || 717 ssh_digest_update(hashctx, hash, hashlen) != 0 || 718 ssh_digest_update(hashctx, digest, have) != 0 || 719 ssh_digest_final(hashctx, digest + have, mdsz) != 0) { 720 r = SSH_ERR_LIBCRYPTO_ERROR; 721 goto out; 722 } 723 ssh_digest_free(hashctx); 724 hashctx = NULL; 725 } 726 #ifdef DEBUG_KEX 727 fprintf(stderr, "key '%c'== ", c); 728 dump_digest("key", digest, need); 729 #endif 730 *keyp = digest; 731 digest = NULL; 732 r = 0; 733 out: 734 if (digest) 735 free(digest); 736 ssh_digest_free(hashctx); 737 return r; 738 } 739 740 #define NKEYS 6 741 int 742 kex_derive_keys(struct ssh *ssh, u_char *hash, u_int hashlen, 743 const struct sshbuf *shared_secret) 744 { 745 struct kex *kex = ssh->kex; 746 u_char *keys[NKEYS]; 747 u_int i, j, mode, ctos; 748 int r; 749 750 for (i = 0; i < NKEYS; i++) { 751 if ((r = derive_key(ssh, 'A'+i, kex->we_need, hash, hashlen, 752 shared_secret, &keys[i])) != 0) { 753 for (j = 0; j < i; j++) 754 free(keys[j]); 755 return r; 756 } 757 } 758 for (mode = 0; mode < MODE_MAX; mode++) { 759 ctos = (!kex->server && mode == MODE_OUT) || 760 (kex->server && mode == MODE_IN); 761 kex->newkeys[mode]->enc.iv = keys[ctos ? 0 : 1]; 762 kex->newkeys[mode]->enc.key = keys[ctos ? 2 : 3]; 763 kex->newkeys[mode]->mac.key = keys[ctos ? 4 : 5]; 764 } 765 return 0; 766 } 767 768 #ifdef WITH_OPENSSL 769 int 770 kex_derive_keys_bn(struct ssh *ssh, u_char *hash, u_int hashlen, 771 const BIGNUM *secret) 772 { 773 struct sshbuf *shared_secret; 774 int r; 775 776 if ((shared_secret = sshbuf_new()) == NULL) 777 return SSH_ERR_ALLOC_FAIL; 778 if ((r = sshbuf_put_bignum2(shared_secret, secret)) == 0) 779 r = kex_derive_keys(ssh, hash, hashlen, shared_secret); 780 sshbuf_free(shared_secret); 781 return r; 782 } 783 #endif 784 785 #ifdef WITH_SSH1 786 int 787 derive_ssh1_session_id(BIGNUM *host_modulus, BIGNUM *server_modulus, 788 u_int8_t cookie[8], u_int8_t id[16]) 789 { 790 u_int8_t hbuf[2048], sbuf[2048], obuf[SSH_DIGEST_MAX_LENGTH]; 791 struct ssh_digest_ctx *hashctx = NULL; 792 size_t hlen, slen; 793 int r; 794 795 hlen = BN_num_bytes(host_modulus); 796 slen = BN_num_bytes(server_modulus); 797 if (hlen < (512 / 8) || (u_int)hlen > sizeof(hbuf) || 798 slen < (512 / 8) || (u_int)slen > sizeof(sbuf)) 799 return SSH_ERR_KEY_BITS_MISMATCH; 800 if (BN_bn2bin(host_modulus, hbuf) <= 0 || 801 BN_bn2bin(server_modulus, sbuf) <= 0) { 802 r = SSH_ERR_LIBCRYPTO_ERROR; 803 goto out; 804 } 805 if ((hashctx = ssh_digest_start(SSH_DIGEST_MD5)) == NULL) { 806 r = SSH_ERR_ALLOC_FAIL; 807 goto out; 808 } 809 if (ssh_digest_update(hashctx, hbuf, hlen) != 0 || 810 ssh_digest_update(hashctx, sbuf, slen) != 0 || 811 ssh_digest_update(hashctx, cookie, 8) != 0 || 812 ssh_digest_final(hashctx, obuf, sizeof(obuf)) != 0) { 813 r = SSH_ERR_LIBCRYPTO_ERROR; 814 goto out; 815 } 816 memcpy(id, obuf, ssh_digest_bytes(SSH_DIGEST_MD5)); 817 r = 0; 818 out: 819 ssh_digest_free(hashctx); 820 explicit_bzero(hbuf, sizeof(hbuf)); 821 explicit_bzero(sbuf, sizeof(sbuf)); 822 explicit_bzero(obuf, sizeof(obuf)); 823 return r; 824 } 825 #endif 826 827 #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH) 828 void 829 dump_digest(char *msg, u_char *digest, int len) 830 { 831 fprintf(stderr, "%s\n", msg); 832 sshbuf_dump_data(digest, len, stderr); 833 } 834 #endif 835