1 /* $NetBSD: kex.c,v 1.10 2015/04/03 23:58:19 christos Exp $ */ 2 /* $OpenBSD: kex.c,v 1.105 2015/01/30 00:22:25 djm Exp $ */ 3 /* 4 * Copyright (c) 2000, 2001 Markus Friedl. All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25 */ 26 27 #include "includes.h" 28 __RCSID("$NetBSD: kex.c,v 1.10 2015/04/03 23:58:19 christos Exp $"); 29 #include <sys/param.h> /* MAX roundup */ 30 31 #include <signal.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 "canohost.h" 53 #include "roaming.h" 54 55 #include "ssherr.h" 56 #include "sshbuf.h" 57 #include "digest.h" 58 59 /* prototype */ 60 static int kex_choose_conf(struct ssh *); 61 static int kex_input_newkeys(int, u_int32_t, void *); 62 63 struct kexalg { 64 const char *name; 65 u_int type; 66 int ec_nid; 67 int hash_alg; 68 }; 69 static const struct kexalg kexalgs[] = { 70 #ifdef WITH_OPENSSL 71 { KEX_DH1, KEX_DH_GRP1_SHA1, 0, SSH_DIGEST_SHA1 }, 72 { KEX_DH14, KEX_DH_GRP14_SHA1, 0, SSH_DIGEST_SHA1 }, 73 { KEX_DHGEX_SHA1, KEX_DH_GEX_SHA1, 0, SSH_DIGEST_SHA1 }, 74 { KEX_DHGEX_SHA256, KEX_DH_GEX_SHA256, 0, SSH_DIGEST_SHA256 }, 75 { KEX_ECDH_SHA2_NISTP256, KEX_ECDH_SHA2, 76 NID_X9_62_prime256v1, SSH_DIGEST_SHA256 }, 77 { KEX_ECDH_SHA2_NISTP384, KEX_ECDH_SHA2, NID_secp384r1, 78 SSH_DIGEST_SHA384 }, 79 { KEX_ECDH_SHA2_NISTP521, KEX_ECDH_SHA2, NID_secp521r1, 80 SSH_DIGEST_SHA512 }, 81 #endif 82 { KEX_CURVE25519_SHA256, KEX_C25519_SHA256, 0, SSH_DIGEST_SHA256 }, 83 { NULL, (u_int)-1, -1, -1}, 84 }; 85 86 char * 87 kex_alg_list(char sep) 88 { 89 char *ret = NULL, *tmp; 90 size_t nlen, rlen = 0; 91 const struct kexalg *k; 92 93 for (k = kexalgs; k->name != NULL; k++) { 94 if (ret != NULL) 95 ret[rlen++] = sep; 96 nlen = strlen(k->name); 97 if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) { 98 free(ret); 99 return NULL; 100 } 101 ret = tmp; 102 memcpy(ret + rlen, k->name, nlen + 1); 103 rlen += nlen; 104 } 105 return ret; 106 } 107 108 static const struct kexalg * 109 kex_alg_by_name(const char *name) 110 { 111 const struct kexalg *k; 112 113 for (k = kexalgs; k->name != NULL; k++) { 114 if (strcmp(k->name, name) == 0) 115 return k; 116 } 117 return NULL; 118 } 119 120 /* Validate KEX method name list */ 121 int 122 kex_names_valid(const char *names) 123 { 124 char *s, *cp, *p; 125 126 if (names == NULL || strcmp(names, "") == 0) 127 return 0; 128 if ((s = cp = strdup(names)) == NULL) 129 return 0; 130 for ((p = strsep(&cp, ",")); p && *p != '\0'; 131 (p = strsep(&cp, ","))) { 132 if (kex_alg_by_name(p) == NULL) { 133 error("Unsupported KEX algorithm \"%.100s\"", p); 134 free(s); 135 return 0; 136 } 137 } 138 debug3("kex names ok: [%s]", names); 139 free(s); 140 return 1; 141 } 142 143 /* put algorithm proposal into buffer */ 144 int 145 kex_prop2buf(struct sshbuf *b, const char *proposal[PROPOSAL_MAX]) 146 { 147 u_int i; 148 int r; 149 150 sshbuf_reset(b); 151 152 /* 153 * add a dummy cookie, the cookie will be overwritten by 154 * kex_send_kexinit(), each time a kexinit is set 155 */ 156 for (i = 0; i < KEX_COOKIE_LEN; i++) { 157 if ((r = sshbuf_put_u8(b, 0)) != 0) 158 return r; 159 } 160 for (i = 0; i < PROPOSAL_MAX; i++) { 161 if ((r = sshbuf_put_cstring(b, proposal[i])) != 0) 162 return r; 163 } 164 if ((r = sshbuf_put_u8(b, 0)) != 0 || /* first_kex_packet_follows */ 165 (r = sshbuf_put_u32(b, 0)) != 0) /* uint32 reserved */ 166 return r; 167 return 0; 168 } 169 170 /* parse buffer and return algorithm proposal */ 171 int 172 kex_buf2prop(struct sshbuf *raw, int *first_kex_follows, char ***propp) 173 { 174 struct sshbuf *b = NULL; 175 u_char v; 176 u_int i; 177 char **proposal = NULL; 178 int r; 179 180 *propp = NULL; 181 if ((proposal = calloc(PROPOSAL_MAX, sizeof(char *))) == NULL) 182 return SSH_ERR_ALLOC_FAIL; 183 if ((b = sshbuf_fromb(raw)) == NULL) { 184 r = SSH_ERR_ALLOC_FAIL; 185 goto out; 186 } 187 if ((r = sshbuf_consume(b, KEX_COOKIE_LEN)) != 0) /* skip cookie */ 188 goto out; 189 /* extract kex init proposal strings */ 190 for (i = 0; i < PROPOSAL_MAX; i++) { 191 if ((r = sshbuf_get_cstring(b, &(proposal[i]), NULL)) != 0) 192 goto out; 193 debug2("kex_parse_kexinit: %s", proposal[i]); 194 } 195 /* first kex follows / reserved */ 196 if ((r = sshbuf_get_u8(b, &v)) != 0 || 197 (r = sshbuf_get_u32(b, &i)) != 0) 198 goto out; 199 if (first_kex_follows != NULL) 200 *first_kex_follows = i; 201 debug2("kex_parse_kexinit: first_kex_follows %d ", v); 202 debug2("kex_parse_kexinit: reserved %u ", i); 203 r = 0; 204 *propp = proposal; 205 out: 206 if (r != 0 && proposal != NULL) 207 kex_prop_free(proposal); 208 sshbuf_free(b); 209 return r; 210 } 211 212 void 213 kex_prop_free(char **proposal) 214 { 215 u_int i; 216 217 for (i = 0; i < PROPOSAL_MAX; i++) 218 free(proposal[i]); 219 free(proposal); 220 } 221 222 /* ARGSUSED */ 223 static int 224 kex_protocol_error(int type, u_int32_t seq, void *ctxt) 225 { 226 error("Hm, kex protocol error: type %d seq %u", type, seq); 227 return 0; 228 } 229 230 static void 231 kex_reset_dispatch(struct ssh *ssh) 232 { 233 ssh_dispatch_range(ssh, SSH2_MSG_TRANSPORT_MIN, 234 SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error); 235 ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit); 236 } 237 238 int 239 kex_send_newkeys(struct ssh *ssh) 240 { 241 int r; 242 243 kex_reset_dispatch(ssh); 244 if ((r = sshpkt_start(ssh, SSH2_MSG_NEWKEYS)) != 0 || 245 (r = sshpkt_send(ssh)) != 0) 246 return r; 247 debug("SSH2_MSG_NEWKEYS sent"); 248 debug("expecting SSH2_MSG_NEWKEYS"); 249 ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_input_newkeys); 250 return 0; 251 } 252 253 static int 254 kex_input_newkeys(int type, u_int32_t seq, void *ctxt) 255 { 256 struct ssh *ssh = ctxt; 257 struct kex *kex = ssh->kex; 258 int r; 259 260 debug("SSH2_MSG_NEWKEYS received"); 261 ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_protocol_error); 262 if ((r = sshpkt_get_end(ssh)) != 0) 263 return r; 264 kex->done = 1; 265 sshbuf_reset(kex->peer); 266 /* sshbuf_reset(kex->my); */ 267 kex->flags &= ~KEX_INIT_SENT; 268 free(kex->name); 269 kex->name = NULL; 270 return 0; 271 } 272 273 int 274 kex_send_kexinit(struct ssh *ssh) 275 { 276 u_char *cookie; 277 struct kex *kex = ssh->kex; 278 int r; 279 280 if (kex == NULL) 281 return SSH_ERR_INTERNAL_ERROR; 282 if (kex->flags & KEX_INIT_SENT) 283 return 0; 284 kex->done = 0; 285 286 /* generate a random cookie */ 287 if (sshbuf_len(kex->my) < KEX_COOKIE_LEN) 288 return SSH_ERR_INVALID_FORMAT; 289 if ((cookie = sshbuf_mutable_ptr(kex->my)) == NULL) 290 return SSH_ERR_INTERNAL_ERROR; 291 arc4random_buf(cookie, KEX_COOKIE_LEN); 292 293 if ((r = sshpkt_start(ssh, SSH2_MSG_KEXINIT)) != 0 || 294 (r = sshpkt_putb(ssh, kex->my)) != 0 || 295 (r = sshpkt_send(ssh)) != 0) 296 return r; 297 debug("SSH2_MSG_KEXINIT sent"); 298 kex->flags |= KEX_INIT_SENT; 299 return 0; 300 } 301 302 /* ARGSUSED */ 303 int 304 kex_input_kexinit(int type, u_int32_t seq, void *ctxt) 305 { 306 struct ssh *ssh = ctxt; 307 struct kex *kex = ssh->kex; 308 const u_char *ptr; 309 u_int i; 310 size_t dlen; 311 int r; 312 313 debug("SSH2_MSG_KEXINIT received"); 314 if (kex == NULL) 315 return SSH_ERR_INVALID_ARGUMENT; 316 317 ptr = sshpkt_ptr(ssh, &dlen); 318 if ((r = sshbuf_put(kex->peer, ptr, dlen)) != 0) 319 return r; 320 321 /* discard packet */ 322 for (i = 0; i < KEX_COOKIE_LEN; i++) 323 if ((r = sshpkt_get_u8(ssh, NULL)) != 0) 324 return r; 325 for (i = 0; i < PROPOSAL_MAX; i++) 326 if ((r = sshpkt_get_string(ssh, NULL, NULL)) != 0) 327 return r; 328 /* 329 * XXX RFC4253 sec 7: "each side MAY guess" - currently no supported 330 * KEX method has the server move first, but a server might be using 331 * a custom method or one that we otherwise don't support. We should 332 * be prepared to remember first_kex_follows here so we can eat a 333 * packet later. 334 * XXX2 - RFC4253 is kind of ambiguous on what first_kex_follows means 335 * for cases where the server *doesn't* go first. I guess we should 336 * ignore it when it is set for these cases, which is what we do now. 337 */ 338 if ((r = sshpkt_get_u8(ssh, NULL)) != 0 || /* first_kex_follows */ 339 (r = sshpkt_get_u32(ssh, NULL)) != 0 || /* reserved */ 340 (r = sshpkt_get_end(ssh)) != 0) 341 return r; 342 343 if (!(kex->flags & KEX_INIT_SENT)) 344 if ((r = kex_send_kexinit(ssh)) != 0) 345 return r; 346 if ((r = kex_choose_conf(ssh)) != 0) 347 return r; 348 349 if (kex->kex_type < KEX_MAX && kex->kex[kex->kex_type] != NULL) 350 return (kex->kex[kex->kex_type])(ssh); 351 352 return SSH_ERR_INTERNAL_ERROR; 353 } 354 355 int 356 kex_new(struct ssh *ssh, const char *proposal[PROPOSAL_MAX], struct kex **kexp) 357 { 358 struct kex *kex; 359 int r; 360 361 *kexp = NULL; 362 if ((kex = calloc(1, sizeof(*kex))) == NULL) 363 return SSH_ERR_ALLOC_FAIL; 364 if ((kex->peer = sshbuf_new()) == NULL || 365 (kex->my = sshbuf_new()) == NULL) { 366 r = SSH_ERR_ALLOC_FAIL; 367 goto out; 368 } 369 if ((r = kex_prop2buf(kex->my, proposal)) != 0) 370 goto out; 371 kex->done = 0; 372 kex_reset_dispatch(ssh); 373 r = 0; 374 *kexp = kex; 375 out: 376 if (r != 0) 377 kex_free(kex); 378 return r; 379 } 380 381 void 382 kex_free_newkeys(struct newkeys *newkeys) 383 { 384 if (newkeys == NULL) 385 return; 386 if (newkeys->enc.key) { 387 explicit_bzero(newkeys->enc.key, newkeys->enc.key_len); 388 free(newkeys->enc.key); 389 newkeys->enc.key = NULL; 390 } 391 if (newkeys->enc.iv) { 392 explicit_bzero(newkeys->enc.iv, newkeys->enc.block_size); 393 free(newkeys->enc.iv); 394 newkeys->enc.iv = NULL; 395 } 396 free(newkeys->enc.name); 397 explicit_bzero(&newkeys->enc, sizeof(newkeys->enc)); 398 free(newkeys->comp.name); 399 explicit_bzero(&newkeys->comp, sizeof(newkeys->comp)); 400 mac_clear(&newkeys->mac); 401 if (newkeys->mac.key) { 402 explicit_bzero(newkeys->mac.key, newkeys->mac.key_len); 403 free(newkeys->mac.key); 404 newkeys->mac.key = NULL; 405 } 406 free(newkeys->mac.name); 407 explicit_bzero(&newkeys->mac, sizeof(newkeys->mac)); 408 explicit_bzero(newkeys, sizeof(*newkeys)); 409 free(newkeys); 410 } 411 412 void 413 kex_free(struct kex *kex) 414 { 415 u_int mode; 416 417 #ifdef WITH_OPENSSL 418 if (kex->dh) 419 DH_free(kex->dh); 420 if (kex->ec_client_key) 421 EC_KEY_free(kex->ec_client_key); 422 #endif 423 for (mode = 0; mode < MODE_MAX; mode++) { 424 kex_free_newkeys(kex->newkeys[mode]); 425 kex->newkeys[mode] = NULL; 426 } 427 sshbuf_free(kex->peer); 428 sshbuf_free(kex->my); 429 free(kex->session_id); 430 free(kex->client_version_string); 431 free(kex->server_version_string); 432 free(kex); 433 } 434 435 int 436 kex_setup(struct ssh *ssh, const char *proposal[PROPOSAL_MAX]) 437 { 438 int r; 439 440 if ((r = kex_new(ssh, proposal, &ssh->kex)) != 0) 441 return r; 442 if ((r = kex_send_kexinit(ssh)) != 0) { /* we start */ 443 kex_free(ssh->kex); 444 ssh->kex = NULL; 445 return r; 446 } 447 return 0; 448 } 449 450 static int 451 choose_enc(struct sshenc *enc, char *client, char *server) 452 { 453 char *name = match_list(client, server, NULL); 454 455 if (name == NULL) 456 return SSH_ERR_NO_CIPHER_ALG_MATCH; 457 if ((enc->cipher = cipher_by_name(name)) == NULL) 458 return SSH_ERR_INTERNAL_ERROR; 459 enc->name = name; 460 enc->enabled = 0; 461 enc->iv = NULL; 462 enc->iv_len = cipher_ivlen(enc->cipher); 463 enc->key = NULL; 464 enc->key_len = cipher_keylen(enc->cipher); 465 enc->block_size = cipher_blocksize(enc->cipher); 466 return 0; 467 } 468 469 static int 470 choose_mac(struct ssh *ssh, struct sshmac *mac, char *client, char *server) 471 { 472 char *name = match_list(client, server, NULL); 473 474 if (name == NULL) 475 return SSH_ERR_NO_MAC_ALG_MATCH; 476 if (mac_setup(mac, name) < 0) 477 return SSH_ERR_INTERNAL_ERROR; 478 /* truncate the key */ 479 if (ssh->compat & SSH_BUG_HMAC) 480 mac->key_len = 16; 481 mac->name = name; 482 mac->key = NULL; 483 mac->enabled = 0; 484 return 0; 485 } 486 487 static int 488 choose_comp(struct sshcomp *comp, char *client, char *server) 489 { 490 char *name = match_list(client, server, NULL); 491 492 if (name == NULL) 493 return SSH_ERR_NO_COMPRESS_ALG_MATCH; 494 if (strcmp(name, "zlib@openssh.com") == 0) { 495 comp->type = COMP_DELAYED; 496 } else if (strcmp(name, "zlib") == 0) { 497 comp->type = COMP_ZLIB; 498 } else if (strcmp(name, "none") == 0) { 499 comp->type = COMP_NONE; 500 } else { 501 return SSH_ERR_INTERNAL_ERROR; 502 } 503 comp->name = name; 504 return 0; 505 } 506 507 static int 508 choose_kex(struct kex *k, char *client, char *server) 509 { 510 const struct kexalg *kexalg; 511 512 k->name = match_list(client, server, NULL); 513 514 if (k->name == NULL) 515 return SSH_ERR_NO_KEX_ALG_MATCH; 516 if ((kexalg = kex_alg_by_name(k->name)) == NULL) 517 return SSH_ERR_INTERNAL_ERROR; 518 k->kex_type = kexalg->type; 519 k->hash_alg = kexalg->hash_alg; 520 k->ec_nid = kexalg->ec_nid; 521 return 0; 522 } 523 524 static int 525 choose_hostkeyalg(struct kex *k, char *client, char *server) 526 { 527 char *hostkeyalg = match_list(client, server, NULL); 528 529 if (hostkeyalg == NULL) 530 return SSH_ERR_NO_HOSTKEY_ALG_MATCH; 531 k->hostkey_type = sshkey_type_from_name(hostkeyalg); 532 if (k->hostkey_type == KEY_UNSPEC) 533 return SSH_ERR_INTERNAL_ERROR; 534 k->hostkey_nid = sshkey_ecdsa_nid_from_name(hostkeyalg); 535 free(hostkeyalg); 536 return 0; 537 } 538 539 static int 540 proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX]) 541 { 542 static int check[] = { 543 PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1 544 }; 545 int *idx; 546 char *p; 547 548 for (idx = &check[0]; *idx != -1; idx++) { 549 if ((p = strchr(my[*idx], ',')) != NULL) 550 *p = '\0'; 551 if ((p = strchr(peer[*idx], ',')) != NULL) 552 *p = '\0'; 553 if (strcmp(my[*idx], peer[*idx]) != 0) { 554 debug2("proposal mismatch: my %s peer %s", 555 my[*idx], peer[*idx]); 556 return (0); 557 } 558 } 559 debug2("proposals match"); 560 return (1); 561 } 562 563 static int 564 kex_choose_conf(struct ssh *ssh) 565 { 566 struct kex *kex = ssh->kex; 567 struct newkeys *newkeys; 568 char **my = NULL, **peer = NULL; 569 char **cprop, **sprop; 570 int nenc, nmac, ncomp; 571 u_int mode, ctos, need, dh_need, authlen; 572 int log_flag = 0; 573 int r, first_kex_follows; 574 575 if ((r = kex_buf2prop(kex->my, NULL, &my)) != 0 || 576 (r = kex_buf2prop(kex->peer, &first_kex_follows, &peer)) != 0) 577 goto out; 578 579 if (kex->server) { 580 cprop=peer; 581 sprop=my; 582 } else { 583 cprop=my; 584 sprop=peer; 585 } 586 587 /* Check whether server offers roaming */ 588 if (!kex->server) { 589 char *roaming = match_list(KEX_RESUME, 590 peer[PROPOSAL_KEX_ALGS], NULL); 591 592 if (roaming) { 593 kex->roaming = 1; 594 free(roaming); 595 } 596 } 597 598 /* Algorithm Negotiation */ 599 for (mode = 0; mode < MODE_MAX; mode++) { 600 if ((newkeys = calloc(1, sizeof(*newkeys))) == NULL) { 601 r = SSH_ERR_ALLOC_FAIL; 602 goto out; 603 } 604 kex->newkeys[mode] = newkeys; 605 ctos = (!kex->server && mode == MODE_OUT) || 606 (kex->server && mode == MODE_IN); 607 nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC; 608 nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC; 609 ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC; 610 if ((r = choose_enc(&newkeys->enc, cprop[nenc], 611 sprop[nenc])) != 0) 612 goto out; 613 authlen = cipher_authlen(newkeys->enc.cipher); 614 /* ignore mac for authenticated encryption */ 615 if (authlen == 0 && 616 (r = choose_mac(ssh, &newkeys->mac, cprop[nmac], 617 sprop[nmac])) != 0) 618 goto out; 619 if ((r = choose_comp(&newkeys->comp, cprop[ncomp], 620 sprop[ncomp])) != 0) 621 goto out; 622 debug("REQUESTED ENC.NAME is '%s'", newkeys->enc.name); 623 if (strcmp(newkeys->enc.name, "none") == 0) { 624 int auth_flag; 625 626 auth_flag = ssh_packet_authentication_state(); 627 debug("Requesting NONE. Authflag is %d", auth_flag); 628 if (auth_flag == 1) { 629 debug("None requested post authentication."); 630 } else { 631 fatal("Pre-authentication none cipher requests are not allowed."); 632 } 633 } 634 debug("kex: %s %s %s %s", 635 ctos ? "client->server" : "server->client", 636 newkeys->enc.name, 637 authlen == 0 ? newkeys->mac.name : "<implicit>", 638 newkeys->comp.name); 639 /* client starts withctos = 0 && log flag = 0 and no log*/ 640 /* 2nd client pass ctos=1 and flag = 1 so no log*/ 641 /* server starts with ctos =1 && log_flag = 0 so log */ 642 /* 2nd sever pass ctos = 1 && log flag = 1 so no log*/ 643 /* -cjr*/ 644 if (ctos && !log_flag) { 645 logit("SSH: Server;Ltype: Kex;Remote: %s-%d;Enc: %s;MAC: %s;Comp: %s", 646 get_remote_ipaddr(), 647 get_remote_port(), 648 newkeys->enc.name, 649 newkeys->mac.name, 650 newkeys->comp.name); 651 } 652 log_flag = 1; 653 } 654 if ((r = choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], 655 sprop[PROPOSAL_KEX_ALGS])) != 0 || 656 (r = choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS], 657 sprop[PROPOSAL_SERVER_HOST_KEY_ALGS])) != 0) 658 goto out; 659 need = dh_need = 0; 660 for (mode = 0; mode < MODE_MAX; mode++) { 661 newkeys = kex->newkeys[mode]; 662 need = MAX(need, newkeys->enc.key_len); 663 need = MAX(need, newkeys->enc.block_size); 664 need = MAX(need, newkeys->enc.iv_len); 665 need = MAX(need, newkeys->mac.key_len); 666 dh_need = MAX(dh_need, cipher_seclen(newkeys->enc.cipher)); 667 dh_need = MAX(dh_need, newkeys->enc.block_size); 668 dh_need = MAX(dh_need, newkeys->enc.iv_len); 669 dh_need = MAX(dh_need, newkeys->mac.key_len); 670 } 671 /* XXX need runden? */ 672 kex->we_need = need; 673 kex->dh_need = dh_need; 674 675 /* ignore the next message if the proposals do not match */ 676 if (first_kex_follows && !proposals_match(my, peer) && 677 !(ssh->compat & SSH_BUG_FIRSTKEX)) 678 ssh->dispatch_skip_packets = 1; 679 r = 0; 680 out: 681 kex_prop_free(my); 682 kex_prop_free(peer); 683 return r; 684 } 685 686 static int 687 derive_key(struct ssh *ssh, int id, u_int need, u_char *hash, u_int hashlen, 688 const struct sshbuf *shared_secret, u_char **keyp) 689 { 690 struct kex *kex = ssh->kex; 691 struct ssh_digest_ctx *hashctx = NULL; 692 char c = id; 693 u_int have; 694 size_t mdsz; 695 u_char *digest; 696 int r; 697 698 if ((mdsz = ssh_digest_bytes(kex->hash_alg)) == 0) 699 return SSH_ERR_INVALID_ARGUMENT; 700 if ((digest = calloc(1, roundup(need, mdsz))) == NULL) { 701 r = SSH_ERR_ALLOC_FAIL; 702 goto out; 703 } 704 705 /* K1 = HASH(K || H || "A" || session_id) */ 706 if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL || 707 ssh_digest_update_buffer(hashctx, shared_secret) != 0 || 708 ssh_digest_update(hashctx, hash, hashlen) != 0 || 709 ssh_digest_update(hashctx, &c, 1) != 0 || 710 ssh_digest_update(hashctx, kex->session_id, 711 kex->session_id_len) != 0 || 712 ssh_digest_final(hashctx, digest, mdsz) != 0) { 713 r = SSH_ERR_LIBCRYPTO_ERROR; 714 goto out; 715 } 716 ssh_digest_free(hashctx); 717 hashctx = NULL; 718 719 /* 720 * expand key: 721 * Kn = HASH(K || H || K1 || K2 || ... || Kn-1) 722 * Key = K1 || K2 || ... || Kn 723 */ 724 for (have = mdsz; need > have; have += mdsz) { 725 if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL || 726 ssh_digest_update_buffer(hashctx, shared_secret) != 0 || 727 ssh_digest_update(hashctx, hash, hashlen) != 0 || 728 ssh_digest_update(hashctx, digest, have) != 0 || 729 ssh_digest_final(hashctx, digest + have, mdsz) != 0) { 730 r = SSH_ERR_LIBCRYPTO_ERROR; 731 goto out; 732 } 733 ssh_digest_free(hashctx); 734 hashctx = NULL; 735 } 736 #ifdef DEBUG_KEX 737 fprintf(stderr, "key '%c'== ", c); 738 dump_digest("key", digest, need); 739 #endif 740 *keyp = digest; 741 digest = NULL; 742 r = 0; 743 out: 744 if (digest) 745 free(digest); 746 ssh_digest_free(hashctx); 747 return r; 748 } 749 750 #define NKEYS 6 751 int 752 kex_derive_keys(struct ssh *ssh, u_char *hash, u_int hashlen, 753 const struct sshbuf *shared_secret) 754 { 755 struct kex *kex = ssh->kex; 756 u_char *keys[NKEYS]; 757 u_int i, j, mode, ctos; 758 int r; 759 760 for (i = 0; i < NKEYS; i++) { 761 if ((r = derive_key(ssh, 'A'+i, kex->we_need, hash, hashlen, 762 shared_secret, &keys[i])) != 0) { 763 for (j = 0; j < i; j++) 764 free(keys[j]); 765 return r; 766 } 767 } 768 for (mode = 0; mode < MODE_MAX; mode++) { 769 ctos = (!kex->server && mode == MODE_OUT) || 770 (kex->server && mode == MODE_IN); 771 kex->newkeys[mode]->enc.iv = keys[ctos ? 0 : 1]; 772 kex->newkeys[mode]->enc.key = keys[ctos ? 2 : 3]; 773 kex->newkeys[mode]->mac.key = keys[ctos ? 4 : 5]; 774 } 775 return 0; 776 } 777 778 #ifdef WITH_OPENSSL 779 int 780 kex_derive_keys_bn(struct ssh *ssh, u_char *hash, u_int hashlen, 781 const BIGNUM *secret) 782 { 783 struct sshbuf *shared_secret; 784 int r; 785 786 if ((shared_secret = sshbuf_new()) == NULL) 787 return SSH_ERR_ALLOC_FAIL; 788 if ((r = sshbuf_put_bignum2(shared_secret, secret)) == 0) 789 r = kex_derive_keys(ssh, hash, hashlen, shared_secret); 790 sshbuf_free(shared_secret); 791 return r; 792 } 793 #endif 794 795 #ifdef WITH_SSH1 796 int 797 derive_ssh1_session_id(BIGNUM *host_modulus, BIGNUM *server_modulus, 798 u_int8_t cookie[8], u_int8_t id[16]) 799 { 800 u_int8_t hbuf[2048], sbuf[2048], obuf[SSH_DIGEST_MAX_LENGTH]; 801 struct ssh_digest_ctx *hashctx = NULL; 802 size_t hlen, slen; 803 int r; 804 805 hlen = BN_num_bytes(host_modulus); 806 slen = BN_num_bytes(server_modulus); 807 if (hlen < (512 / 8) || (u_int)hlen > sizeof(hbuf) || 808 slen < (512 / 8) || (u_int)slen > sizeof(sbuf)) 809 return SSH_ERR_KEY_BITS_MISMATCH; 810 if (BN_bn2bin(host_modulus, hbuf) <= 0 || 811 BN_bn2bin(server_modulus, sbuf) <= 0) { 812 r = SSH_ERR_LIBCRYPTO_ERROR; 813 goto out; 814 } 815 if ((hashctx = ssh_digest_start(SSH_DIGEST_MD5)) == NULL) { 816 r = SSH_ERR_ALLOC_FAIL; 817 goto out; 818 } 819 if (ssh_digest_update(hashctx, hbuf, hlen) != 0 || 820 ssh_digest_update(hashctx, sbuf, slen) != 0 || 821 ssh_digest_update(hashctx, cookie, 8) != 0 || 822 ssh_digest_final(hashctx, obuf, sizeof(obuf)) != 0) { 823 r = SSH_ERR_LIBCRYPTO_ERROR; 824 goto out; 825 } 826 memcpy(id, obuf, ssh_digest_bytes(SSH_DIGEST_MD5)); 827 r = 0; 828 out: 829 ssh_digest_free(hashctx); 830 explicit_bzero(hbuf, sizeof(hbuf)); 831 explicit_bzero(sbuf, sizeof(sbuf)); 832 explicit_bzero(obuf, sizeof(obuf)); 833 return r; 834 } 835 #endif 836 837 #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH) 838 void 839 dump_digest(char *msg, u_char *digest, int len) 840 { 841 fprintf(stderr, "%s\n", msg); 842 sshbuf_dump_data(digest, len, stderr); 843 } 844 #endif 845