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