1 /* $OpenBSD: kex.c,v 1.109 2015/07/30 00:01:34 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 #include <openssl/dh.h> 39 #endif 40 41 #include "ssh2.h" 42 #include "packet.h" 43 #include "compat.h" 44 #include "cipher.h" 45 #include "sshkey.h" 46 #include "kex.h" 47 #include "log.h" 48 #include "mac.h" 49 #include "match.h" 50 #include "misc.h" 51 #include "dispatch.h" 52 #include "monitor.h" 53 #include "roaming.h" 54 55 #include "ssherr.h" 56 #include "sshbuf.h" 57 #include "digest.h" 58 59 #if OPENSSL_VERSION_NUMBER >= 0x00907000L 60 # if defined(HAVE_EVP_SHA256) 61 # define evp_ssh_sha256 EVP_sha256 62 # else 63 extern const EVP_MD *evp_ssh_sha256(void); 64 # endif 65 #endif 66 67 /* prototype */ 68 static int kex_choose_conf(struct ssh *); 69 static int kex_input_newkeys(int, u_int32_t, void *); 70 71 struct kexalg { 72 char *name; 73 u_int type; 74 int ec_nid; 75 int hash_alg; 76 }; 77 static const struct kexalg kexalgs[] = { 78 #ifdef WITH_OPENSSL 79 { KEX_DH1, KEX_DH_GRP1_SHA1, 0, SSH_DIGEST_SHA1 }, 80 { KEX_DH14, KEX_DH_GRP14_SHA1, 0, SSH_DIGEST_SHA1 }, 81 { KEX_DHGEX_SHA1, KEX_DH_GEX_SHA1, 0, SSH_DIGEST_SHA1 }, 82 #ifdef HAVE_EVP_SHA256 83 { KEX_DHGEX_SHA256, KEX_DH_GEX_SHA256, 0, SSH_DIGEST_SHA256 }, 84 #endif /* HAVE_EVP_SHA256 */ 85 #ifdef OPENSSL_HAS_ECC 86 { KEX_ECDH_SHA2_NISTP256, KEX_ECDH_SHA2, 87 NID_X9_62_prime256v1, SSH_DIGEST_SHA256 }, 88 { KEX_ECDH_SHA2_NISTP384, KEX_ECDH_SHA2, NID_secp384r1, 89 SSH_DIGEST_SHA384 }, 90 # ifdef OPENSSL_HAS_NISTP521 91 { KEX_ECDH_SHA2_NISTP521, KEX_ECDH_SHA2, NID_secp521r1, 92 SSH_DIGEST_SHA512 }, 93 # endif /* OPENSSL_HAS_NISTP521 */ 94 #endif /* OPENSSL_HAS_ECC */ 95 #endif /* WITH_OPENSSL */ 96 #if defined(HAVE_EVP_SHA256) || !defined(WITH_OPENSSL) 97 { KEX_CURVE25519_SHA256, KEX_C25519_SHA256, 0, SSH_DIGEST_SHA256 }, 98 #endif /* HAVE_EVP_SHA256 || !WITH_OPENSSL */ 99 { NULL, -1, -1, -1}, 100 }; 101 102 char * 103 kex_alg_list(char sep) 104 { 105 char *ret = NULL, *tmp; 106 size_t nlen, rlen = 0; 107 const struct kexalg *k; 108 109 for (k = kexalgs; k->name != NULL; k++) { 110 if (ret != NULL) 111 ret[rlen++] = sep; 112 nlen = strlen(k->name); 113 if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) { 114 free(ret); 115 return NULL; 116 } 117 ret = tmp; 118 memcpy(ret + rlen, k->name, nlen + 1); 119 rlen += nlen; 120 } 121 return ret; 122 } 123 124 static const struct kexalg * 125 kex_alg_by_name(const char *name) 126 { 127 const struct kexalg *k; 128 129 for (k = kexalgs; k->name != NULL; k++) { 130 if (strcmp(k->name, name) == 0) 131 return k; 132 } 133 return NULL; 134 } 135 136 /* Validate KEX method name list */ 137 int 138 kex_names_valid(const char *names) 139 { 140 char *s, *cp, *p; 141 142 if (names == NULL || strcmp(names, "") == 0) 143 return 0; 144 if ((s = cp = strdup(names)) == NULL) 145 return 0; 146 for ((p = strsep(&cp, ",")); p && *p != '\0'; 147 (p = strsep(&cp, ","))) { 148 if (kex_alg_by_name(p) == NULL) { 149 error("Unsupported KEX algorithm \"%.100s\"", p); 150 free(s); 151 return 0; 152 } 153 } 154 debug3("kex names ok: [%s]", names); 155 free(s); 156 return 1; 157 } 158 159 /* 160 * Concatenate algorithm names, avoiding duplicates in the process. 161 * Caller must free returned string. 162 */ 163 char * 164 kex_names_cat(const char *a, const char *b) 165 { 166 char *ret = NULL, *tmp = NULL, *cp, *p; 167 size_t len; 168 169 if (a == NULL || *a == '\0') 170 return NULL; 171 if (b == NULL || *b == '\0') 172 return strdup(a); 173 if (strlen(b) > 1024*1024) 174 return NULL; 175 len = strlen(a) + strlen(b) + 2; 176 if ((tmp = cp = strdup(b)) == NULL || 177 (ret = calloc(1, len)) == NULL) { 178 free(tmp); 179 return NULL; 180 } 181 strlcpy(ret, a, len); 182 for ((p = strsep(&cp, ",")); p && *p != '\0'; (p = strsep(&cp, ","))) { 183 if (match_list(ret, p, NULL) != NULL) 184 continue; /* Algorithm already present */ 185 if (strlcat(ret, ",", len) >= len || 186 strlcat(ret, p, len) >= len) { 187 free(tmp); 188 free(ret); 189 return NULL; /* Shouldn't happen */ 190 } 191 } 192 free(tmp); 193 return ret; 194 } 195 196 /* 197 * Assemble a list of algorithms from a default list and a string from a 198 * configuration file. The user-provided string may begin with '+' to 199 * indicate that it should be appended to the default. 200 */ 201 int 202 kex_assemble_names(const char *def, char **list) 203 { 204 char *ret; 205 206 if (list == NULL || *list == NULL || **list == '\0') { 207 *list = strdup(def); 208 return 0; 209 } 210 if (**list != '+') { 211 return 0; 212 } 213 214 if ((ret = kex_names_cat(def, *list + 1)) == NULL) 215 return SSH_ERR_ALLOC_FAIL; 216 free(*list); 217 *list = ret; 218 return 0; 219 } 220 221 /* put algorithm proposal into buffer */ 222 int 223 kex_prop2buf(struct sshbuf *b, char *proposal[PROPOSAL_MAX]) 224 { 225 u_int i; 226 int r; 227 228 sshbuf_reset(b); 229 230 /* 231 * add a dummy cookie, the cookie will be overwritten by 232 * kex_send_kexinit(), each time a kexinit is set 233 */ 234 for (i = 0; i < KEX_COOKIE_LEN; i++) { 235 if ((r = sshbuf_put_u8(b, 0)) != 0) 236 return r; 237 } 238 for (i = 0; i < PROPOSAL_MAX; i++) { 239 if ((r = sshbuf_put_cstring(b, proposal[i])) != 0) 240 return r; 241 } 242 if ((r = sshbuf_put_u8(b, 0)) != 0 || /* first_kex_packet_follows */ 243 (r = sshbuf_put_u32(b, 0)) != 0) /* uint32 reserved */ 244 return r; 245 return 0; 246 } 247 248 /* parse buffer and return algorithm proposal */ 249 int 250 kex_buf2prop(struct sshbuf *raw, int *first_kex_follows, char ***propp) 251 { 252 struct sshbuf *b = NULL; 253 u_char v; 254 u_int i; 255 char **proposal = NULL; 256 int r; 257 258 *propp = NULL; 259 if ((proposal = calloc(PROPOSAL_MAX, sizeof(char *))) == NULL) 260 return SSH_ERR_ALLOC_FAIL; 261 if ((b = sshbuf_fromb(raw)) == NULL) { 262 r = SSH_ERR_ALLOC_FAIL; 263 goto out; 264 } 265 if ((r = sshbuf_consume(b, KEX_COOKIE_LEN)) != 0) /* skip cookie */ 266 goto out; 267 /* extract kex init proposal strings */ 268 for (i = 0; i < PROPOSAL_MAX; i++) { 269 if ((r = sshbuf_get_cstring(b, &(proposal[i]), NULL)) != 0) 270 goto out; 271 debug2("kex_parse_kexinit: %s", proposal[i]); 272 } 273 /* first kex follows / reserved */ 274 if ((r = sshbuf_get_u8(b, &v)) != 0 || /* first_kex_follows */ 275 (r = sshbuf_get_u32(b, &i)) != 0) /* reserved */ 276 goto out; 277 if (first_kex_follows != NULL) 278 *first_kex_follows = v; 279 debug2("first_kex_follows %d ", v); 280 debug2("reserved %u ", i); 281 r = 0; 282 *propp = proposal; 283 out: 284 if (r != 0 && proposal != NULL) 285 kex_prop_free(proposal); 286 sshbuf_free(b); 287 return r; 288 } 289 290 void 291 kex_prop_free(char **proposal) 292 { 293 u_int i; 294 295 if (proposal == NULL) 296 return; 297 for (i = 0; i < PROPOSAL_MAX; i++) 298 free(proposal[i]); 299 free(proposal); 300 } 301 302 /* ARGSUSED */ 303 static int 304 kex_protocol_error(int type, u_int32_t seq, void *ctxt) 305 { 306 error("Hm, kex protocol error: type %d seq %u", type, seq); 307 return 0; 308 } 309 310 static void 311 kex_reset_dispatch(struct ssh *ssh) 312 { 313 ssh_dispatch_range(ssh, SSH2_MSG_TRANSPORT_MIN, 314 SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error); 315 ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit); 316 } 317 318 int 319 kex_send_newkeys(struct ssh *ssh) 320 { 321 int r; 322 323 kex_reset_dispatch(ssh); 324 if ((r = sshpkt_start(ssh, SSH2_MSG_NEWKEYS)) != 0 || 325 (r = sshpkt_send(ssh)) != 0) 326 return r; 327 debug("SSH2_MSG_NEWKEYS sent"); 328 debug("expecting SSH2_MSG_NEWKEYS"); 329 ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_input_newkeys); 330 return 0; 331 } 332 333 static int 334 kex_input_newkeys(int type, u_int32_t seq, void *ctxt) 335 { 336 struct ssh *ssh = ctxt; 337 struct kex *kex = ssh->kex; 338 int r; 339 340 debug("SSH2_MSG_NEWKEYS received"); 341 ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_protocol_error); 342 if ((r = sshpkt_get_end(ssh)) != 0) 343 return r; 344 kex->done = 1; 345 sshbuf_reset(kex->peer); 346 /* sshbuf_reset(kex->my); */ 347 kex->flags &= ~KEX_INIT_SENT; 348 free(kex->name); 349 kex->name = NULL; 350 return 0; 351 } 352 353 int 354 kex_send_kexinit(struct ssh *ssh) 355 { 356 u_char *cookie; 357 struct kex *kex = ssh->kex; 358 int r; 359 360 if (kex == NULL) 361 return SSH_ERR_INTERNAL_ERROR; 362 if (kex->flags & KEX_INIT_SENT) 363 return 0; 364 kex->done = 0; 365 366 /* generate a random cookie */ 367 if (sshbuf_len(kex->my) < KEX_COOKIE_LEN) 368 return SSH_ERR_INVALID_FORMAT; 369 if ((cookie = sshbuf_mutable_ptr(kex->my)) == NULL) 370 return SSH_ERR_INTERNAL_ERROR; 371 arc4random_buf(cookie, KEX_COOKIE_LEN); 372 373 if ((r = sshpkt_start(ssh, SSH2_MSG_KEXINIT)) != 0 || 374 (r = sshpkt_putb(ssh, kex->my)) != 0 || 375 (r = sshpkt_send(ssh)) != 0) 376 return r; 377 debug("SSH2_MSG_KEXINIT sent"); 378 kex->flags |= KEX_INIT_SENT; 379 return 0; 380 } 381 382 /* ARGSUSED */ 383 int 384 kex_input_kexinit(int type, u_int32_t seq, void *ctxt) 385 { 386 struct ssh *ssh = ctxt; 387 struct kex *kex = ssh->kex; 388 const u_char *ptr; 389 u_int i; 390 size_t dlen; 391 int r; 392 393 debug("SSH2_MSG_KEXINIT received"); 394 if (kex == NULL) 395 return SSH_ERR_INVALID_ARGUMENT; 396 397 ptr = sshpkt_ptr(ssh, &dlen); 398 if ((r = sshbuf_put(kex->peer, ptr, dlen)) != 0) 399 return r; 400 401 /* discard packet */ 402 for (i = 0; i < KEX_COOKIE_LEN; i++) 403 if ((r = sshpkt_get_u8(ssh, NULL)) != 0) 404 return r; 405 for (i = 0; i < PROPOSAL_MAX; i++) 406 if ((r = sshpkt_get_string(ssh, NULL, NULL)) != 0) 407 return r; 408 /* 409 * XXX RFC4253 sec 7: "each side MAY guess" - currently no supported 410 * KEX method has the server move first, but a server might be using 411 * a custom method or one that we otherwise don't support. We should 412 * be prepared to remember first_kex_follows here so we can eat a 413 * packet later. 414 * XXX2 - RFC4253 is kind of ambiguous on what first_kex_follows means 415 * for cases where the server *doesn't* go first. I guess we should 416 * ignore it when it is set for these cases, which is what we do now. 417 */ 418 if ((r = sshpkt_get_u8(ssh, NULL)) != 0 || /* first_kex_follows */ 419 (r = sshpkt_get_u32(ssh, NULL)) != 0 || /* reserved */ 420 (r = sshpkt_get_end(ssh)) != 0) 421 return r; 422 423 if (!(kex->flags & KEX_INIT_SENT)) 424 if ((r = kex_send_kexinit(ssh)) != 0) 425 return r; 426 if ((r = kex_choose_conf(ssh)) != 0) 427 return r; 428 429 if (kex->kex_type < KEX_MAX && kex->kex[kex->kex_type] != NULL) 430 return (kex->kex[kex->kex_type])(ssh); 431 432 return SSH_ERR_INTERNAL_ERROR; 433 } 434 435 int 436 kex_new(struct ssh *ssh, char *proposal[PROPOSAL_MAX], struct kex **kexp) 437 { 438 struct kex *kex; 439 int r; 440 441 *kexp = NULL; 442 if ((kex = calloc(1, sizeof(*kex))) == NULL) 443 return SSH_ERR_ALLOC_FAIL; 444 if ((kex->peer = sshbuf_new()) == NULL || 445 (kex->my = sshbuf_new()) == NULL) { 446 r = SSH_ERR_ALLOC_FAIL; 447 goto out; 448 } 449 if ((r = kex_prop2buf(kex->my, proposal)) != 0) 450 goto out; 451 kex->done = 0; 452 kex_reset_dispatch(ssh); 453 r = 0; 454 *kexp = kex; 455 out: 456 if (r != 0) 457 kex_free(kex); 458 return r; 459 } 460 461 void 462 kex_free_newkeys(struct newkeys *newkeys) 463 { 464 if (newkeys == NULL) 465 return; 466 if (newkeys->enc.key) { 467 explicit_bzero(newkeys->enc.key, newkeys->enc.key_len); 468 free(newkeys->enc.key); 469 newkeys->enc.key = NULL; 470 } 471 if (newkeys->enc.iv) { 472 explicit_bzero(newkeys->enc.iv, newkeys->enc.block_size); 473 free(newkeys->enc.iv); 474 newkeys->enc.iv = NULL; 475 } 476 free(newkeys->enc.name); 477 explicit_bzero(&newkeys->enc, sizeof(newkeys->enc)); 478 free(newkeys->comp.name); 479 explicit_bzero(&newkeys->comp, sizeof(newkeys->comp)); 480 mac_clear(&newkeys->mac); 481 if (newkeys->mac.key) { 482 explicit_bzero(newkeys->mac.key, newkeys->mac.key_len); 483 free(newkeys->mac.key); 484 newkeys->mac.key = NULL; 485 } 486 free(newkeys->mac.name); 487 explicit_bzero(&newkeys->mac, sizeof(newkeys->mac)); 488 explicit_bzero(newkeys, sizeof(*newkeys)); 489 free(newkeys); 490 } 491 492 void 493 kex_free(struct kex *kex) 494 { 495 u_int mode; 496 497 #ifdef WITH_OPENSSL 498 if (kex->dh) 499 DH_free(kex->dh); 500 #ifdef OPENSSL_HAS_ECC 501 if (kex->ec_client_key) 502 EC_KEY_free(kex->ec_client_key); 503 #endif /* OPENSSL_HAS_ECC */ 504 #endif /* WITH_OPENSSL */ 505 for (mode = 0; mode < MODE_MAX; mode++) { 506 kex_free_newkeys(kex->newkeys[mode]); 507 kex->newkeys[mode] = NULL; 508 } 509 sshbuf_free(kex->peer); 510 sshbuf_free(kex->my); 511 free(kex->session_id); 512 free(kex->client_version_string); 513 free(kex->server_version_string); 514 free(kex->failed_choice); 515 free(kex); 516 } 517 518 int 519 kex_setup(struct ssh *ssh, char *proposal[PROPOSAL_MAX]) 520 { 521 int r; 522 523 if ((r = kex_new(ssh, proposal, &ssh->kex)) != 0) 524 return r; 525 if ((r = kex_send_kexinit(ssh)) != 0) { /* we start */ 526 kex_free(ssh->kex); 527 ssh->kex = NULL; 528 return r; 529 } 530 return 0; 531 } 532 533 static int 534 choose_enc(struct sshenc *enc, char *client, char *server) 535 { 536 char *name = match_list(client, server, NULL); 537 538 if (name == NULL) 539 return SSH_ERR_NO_CIPHER_ALG_MATCH; 540 if ((enc->cipher = cipher_by_name(name)) == NULL) 541 return SSH_ERR_INTERNAL_ERROR; 542 enc->name = name; 543 enc->enabled = 0; 544 enc->iv = NULL; 545 enc->iv_len = cipher_ivlen(enc->cipher); 546 enc->key = NULL; 547 enc->key_len = cipher_keylen(enc->cipher); 548 enc->block_size = cipher_blocksize(enc->cipher); 549 return 0; 550 } 551 552 static int 553 choose_mac(struct ssh *ssh, struct sshmac *mac, char *client, char *server) 554 { 555 char *name = match_list(client, server, NULL); 556 557 if (name == NULL) 558 return SSH_ERR_NO_MAC_ALG_MATCH; 559 if (mac_setup(mac, name) < 0) 560 return SSH_ERR_INTERNAL_ERROR; 561 /* truncate the key */ 562 if (ssh->compat & SSH_BUG_HMAC) 563 mac->key_len = 16; 564 mac->name = name; 565 mac->key = NULL; 566 mac->enabled = 0; 567 return 0; 568 } 569 570 static int 571 choose_comp(struct sshcomp *comp, char *client, char *server) 572 { 573 char *name = match_list(client, server, NULL); 574 575 if (name == NULL) 576 return SSH_ERR_NO_COMPRESS_ALG_MATCH; 577 if (strcmp(name, "zlib (at) openssh.com") == 0) { 578 comp->type = COMP_DELAYED; 579 } else if (strcmp(name, "zlib") == 0) { 580 comp->type = COMP_ZLIB; 581 } else if (strcmp(name, "none") == 0) { 582 comp->type = COMP_NONE; 583 } else { 584 return SSH_ERR_INTERNAL_ERROR; 585 } 586 comp->name = name; 587 return 0; 588 } 589 590 static int 591 choose_kex(struct kex *k, char *client, char *server) 592 { 593 const struct kexalg *kexalg; 594 595 k->name = match_list(client, server, NULL); 596 597 if (k->name == NULL) 598 return SSH_ERR_NO_KEX_ALG_MATCH; 599 if ((kexalg = kex_alg_by_name(k->name)) == NULL) 600 return SSH_ERR_INTERNAL_ERROR; 601 k->kex_type = kexalg->type; 602 k->hash_alg = kexalg->hash_alg; 603 k->ec_nid = kexalg->ec_nid; 604 return 0; 605 } 606 607 static int 608 choose_hostkeyalg(struct kex *k, char *client, char *server) 609 { 610 char *hostkeyalg = match_list(client, server, NULL); 611 612 if (hostkeyalg == NULL) 613 return SSH_ERR_NO_HOSTKEY_ALG_MATCH; 614 k->hostkey_type = sshkey_type_from_name(hostkeyalg); 615 if (k->hostkey_type == KEY_UNSPEC) 616 return SSH_ERR_INTERNAL_ERROR; 617 k->hostkey_nid = sshkey_ecdsa_nid_from_name(hostkeyalg); 618 free(hostkeyalg); 619 return 0; 620 } 621 622 static int 623 proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX]) 624 { 625 static int check[] = { 626 PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1 627 }; 628 int *idx; 629 char *p; 630 631 for (idx = &check[0]; *idx != -1; idx++) { 632 if ((p = strchr(my[*idx], ',')) != NULL) 633 *p = '\0'; 634 if ((p = strchr(peer[*idx], ',')) != NULL) 635 *p = '\0'; 636 if (strcmp(my[*idx], peer[*idx]) != 0) { 637 debug2("proposal mismatch: my %s peer %s", 638 my[*idx], peer[*idx]); 639 return (0); 640 } 641 } 642 debug2("proposals match"); 643 return (1); 644 } 645 646 static int 647 kex_choose_conf(struct ssh *ssh) 648 { 649 struct kex *kex = ssh->kex; 650 struct newkeys *newkeys; 651 char **my = NULL, **peer = NULL; 652 char **cprop, **sprop; 653 int nenc, nmac, ncomp; 654 u_int mode, ctos, need, dh_need, authlen; 655 int r, first_kex_follows; 656 657 if ((r = kex_buf2prop(kex->my, NULL, &my)) != 0 || 658 (r = kex_buf2prop(kex->peer, &first_kex_follows, &peer)) != 0) 659 goto out; 660 661 if (kex->server) { 662 cprop=peer; 663 sprop=my; 664 } else { 665 cprop=my; 666 sprop=peer; 667 } 668 669 /* Check whether server offers roaming */ 670 if (!kex->server) { 671 char *roaming = match_list(KEX_RESUME, 672 peer[PROPOSAL_KEX_ALGS], NULL); 673 674 if (roaming) { 675 kex->roaming = 1; 676 free(roaming); 677 } 678 } 679 680 /* Algorithm Negotiation */ 681 for (mode = 0; mode < MODE_MAX; mode++) { 682 if ((newkeys = calloc(1, sizeof(*newkeys))) == NULL) { 683 r = SSH_ERR_ALLOC_FAIL; 684 goto out; 685 } 686 kex->newkeys[mode] = newkeys; 687 ctos = (!kex->server && mode == MODE_OUT) || 688 (kex->server && mode == MODE_IN); 689 nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC; 690 nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC; 691 ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC; 692 if ((r = choose_enc(&newkeys->enc, cprop[nenc], 693 sprop[nenc])) != 0) { 694 kex->failed_choice = peer[nenc]; 695 peer[nenc] = NULL; 696 goto out; 697 } 698 authlen = cipher_authlen(newkeys->enc.cipher); 699 /* ignore mac for authenticated encryption */ 700 if (authlen == 0 && 701 (r = choose_mac(ssh, &newkeys->mac, cprop[nmac], 702 sprop[nmac])) != 0) { 703 kex->failed_choice = peer[nmac]; 704 peer[nmac] = NULL; 705 goto out; 706 } 707 if ((r = choose_comp(&newkeys->comp, cprop[ncomp], 708 sprop[ncomp])) != 0) { 709 kex->failed_choice = peer[ncomp]; 710 peer[ncomp] = NULL; 711 goto out; 712 } 713 debug("kex: %s %s %s %s", 714 ctos ? "client->server" : "server->client", 715 newkeys->enc.name, 716 authlen == 0 ? newkeys->mac.name : "<implicit>", 717 newkeys->comp.name); 718 } 719 if ((r = choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], 720 sprop[PROPOSAL_KEX_ALGS])) != 0) { 721 kex->failed_choice = peer[PROPOSAL_KEX_ALGS]; 722 peer[PROPOSAL_KEX_ALGS] = NULL; 723 goto out; 724 } 725 if ((r = choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS], 726 sprop[PROPOSAL_SERVER_HOST_KEY_ALGS])) != 0) { 727 kex->failed_choice = peer[PROPOSAL_SERVER_HOST_KEY_ALGS]; 728 peer[PROPOSAL_SERVER_HOST_KEY_ALGS] = NULL; 729 goto out; 730 } 731 need = dh_need = 0; 732 for (mode = 0; mode < MODE_MAX; mode++) { 733 newkeys = kex->newkeys[mode]; 734 need = MAX(need, newkeys->enc.key_len); 735 need = MAX(need, newkeys->enc.block_size); 736 need = MAX(need, newkeys->enc.iv_len); 737 need = MAX(need, newkeys->mac.key_len); 738 dh_need = MAX(dh_need, cipher_seclen(newkeys->enc.cipher)); 739 dh_need = MAX(dh_need, newkeys->enc.block_size); 740 dh_need = MAX(dh_need, newkeys->enc.iv_len); 741 dh_need = MAX(dh_need, newkeys->mac.key_len); 742 } 743 /* XXX need runden? */ 744 kex->we_need = need; 745 kex->dh_need = dh_need; 746 747 /* ignore the next message if the proposals do not match */ 748 if (first_kex_follows && !proposals_match(my, peer) && 749 !(ssh->compat & SSH_BUG_FIRSTKEX)) 750 ssh->dispatch_skip_packets = 1; 751 r = 0; 752 out: 753 kex_prop_free(my); 754 kex_prop_free(peer); 755 return r; 756 } 757 758 static int 759 derive_key(struct ssh *ssh, int id, u_int need, u_char *hash, u_int hashlen, 760 const struct sshbuf *shared_secret, u_char **keyp) 761 { 762 struct kex *kex = ssh->kex; 763 struct ssh_digest_ctx *hashctx = NULL; 764 char c = id; 765 u_int have; 766 size_t mdsz; 767 u_char *digest; 768 int r; 769 770 if ((mdsz = ssh_digest_bytes(kex->hash_alg)) == 0) 771 return SSH_ERR_INVALID_ARGUMENT; 772 if ((digest = calloc(1, roundup(need, mdsz))) == NULL) { 773 r = SSH_ERR_ALLOC_FAIL; 774 goto out; 775 } 776 777 /* K1 = HASH(K || H || "A" || session_id) */ 778 if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL || 779 ssh_digest_update_buffer(hashctx, shared_secret) != 0 || 780 ssh_digest_update(hashctx, hash, hashlen) != 0 || 781 ssh_digest_update(hashctx, &c, 1) != 0 || 782 ssh_digest_update(hashctx, kex->session_id, 783 kex->session_id_len) != 0 || 784 ssh_digest_final(hashctx, digest, mdsz) != 0) { 785 r = SSH_ERR_LIBCRYPTO_ERROR; 786 goto out; 787 } 788 ssh_digest_free(hashctx); 789 hashctx = NULL; 790 791 /* 792 * expand key: 793 * Kn = HASH(K || H || K1 || K2 || ... || Kn-1) 794 * Key = K1 || K2 || ... || Kn 795 */ 796 for (have = mdsz; need > have; have += mdsz) { 797 if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL || 798 ssh_digest_update_buffer(hashctx, shared_secret) != 0 || 799 ssh_digest_update(hashctx, hash, hashlen) != 0 || 800 ssh_digest_update(hashctx, digest, have) != 0 || 801 ssh_digest_final(hashctx, digest + have, mdsz) != 0) { 802 r = SSH_ERR_LIBCRYPTO_ERROR; 803 goto out; 804 } 805 ssh_digest_free(hashctx); 806 hashctx = NULL; 807 } 808 #ifdef DEBUG_KEX 809 fprintf(stderr, "key '%c'== ", c); 810 dump_digest("key", digest, need); 811 #endif 812 *keyp = digest; 813 digest = NULL; 814 r = 0; 815 out: 816 if (digest) 817 free(digest); 818 ssh_digest_free(hashctx); 819 return r; 820 } 821 822 #define NKEYS 6 823 int 824 kex_derive_keys(struct ssh *ssh, u_char *hash, u_int hashlen, 825 const struct sshbuf *shared_secret) 826 { 827 struct kex *kex = ssh->kex; 828 u_char *keys[NKEYS]; 829 u_int i, j, mode, ctos; 830 int r; 831 832 for (i = 0; i < NKEYS; i++) { 833 if ((r = derive_key(ssh, 'A'+i, kex->we_need, hash, hashlen, 834 shared_secret, &keys[i])) != 0) { 835 for (j = 0; j < i; j++) 836 free(keys[j]); 837 return r; 838 } 839 } 840 for (mode = 0; mode < MODE_MAX; mode++) { 841 ctos = (!kex->server && mode == MODE_OUT) || 842 (kex->server && mode == MODE_IN); 843 kex->newkeys[mode]->enc.iv = keys[ctos ? 0 : 1]; 844 kex->newkeys[mode]->enc.key = keys[ctos ? 2 : 3]; 845 kex->newkeys[mode]->mac.key = keys[ctos ? 4 : 5]; 846 } 847 return 0; 848 } 849 850 #ifdef WITH_OPENSSL 851 int 852 kex_derive_keys_bn(struct ssh *ssh, u_char *hash, u_int hashlen, 853 const BIGNUM *secret) 854 { 855 struct sshbuf *shared_secret; 856 int r; 857 858 if ((shared_secret = sshbuf_new()) == NULL) 859 return SSH_ERR_ALLOC_FAIL; 860 if ((r = sshbuf_put_bignum2(shared_secret, secret)) == 0) 861 r = kex_derive_keys(ssh, hash, hashlen, shared_secret); 862 sshbuf_free(shared_secret); 863 return r; 864 } 865 #endif 866 867 #ifdef WITH_SSH1 868 int 869 derive_ssh1_session_id(BIGNUM *host_modulus, BIGNUM *server_modulus, 870 u_int8_t cookie[8], u_int8_t id[16]) 871 { 872 u_int8_t hbuf[2048], sbuf[2048], obuf[SSH_DIGEST_MAX_LENGTH]; 873 struct ssh_digest_ctx *hashctx = NULL; 874 size_t hlen, slen; 875 int r; 876 877 hlen = BN_num_bytes(host_modulus); 878 slen = BN_num_bytes(server_modulus); 879 if (hlen < (512 / 8) || (u_int)hlen > sizeof(hbuf) || 880 slen < (512 / 8) || (u_int)slen > sizeof(sbuf)) 881 return SSH_ERR_KEY_BITS_MISMATCH; 882 if (BN_bn2bin(host_modulus, hbuf) <= 0 || 883 BN_bn2bin(server_modulus, sbuf) <= 0) { 884 r = SSH_ERR_LIBCRYPTO_ERROR; 885 goto out; 886 } 887 if ((hashctx = ssh_digest_start(SSH_DIGEST_MD5)) == NULL) { 888 r = SSH_ERR_ALLOC_FAIL; 889 goto out; 890 } 891 if (ssh_digest_update(hashctx, hbuf, hlen) != 0 || 892 ssh_digest_update(hashctx, sbuf, slen) != 0 || 893 ssh_digest_update(hashctx, cookie, 8) != 0 || 894 ssh_digest_final(hashctx, obuf, sizeof(obuf)) != 0) { 895 r = SSH_ERR_LIBCRYPTO_ERROR; 896 goto out; 897 } 898 memcpy(id, obuf, ssh_digest_bytes(SSH_DIGEST_MD5)); 899 r = 0; 900 out: 901 ssh_digest_free(hashctx); 902 explicit_bzero(hbuf, sizeof(hbuf)); 903 explicit_bzero(sbuf, sizeof(sbuf)); 904 explicit_bzero(obuf, sizeof(obuf)); 905 return r; 906 } 907 #endif 908 909 #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH) 910 void 911 dump_digest(char *msg, u_char *digest, int len) 912 { 913 fprintf(stderr, "%s\n", msg); 914 sshbuf_dump_data(digest, len, stderr); 915 } 916 #endif 917
