1 /* $OpenBSD: ssh_api.c,v 1.18 2019/09/13 04:36:43 dtucker Exp $ */ 2 /* 3 * Copyright (c) 2012 Markus Friedl. All rights reserved. 4 * 5 * Permission to use, copy, modify, and distribute this software for any 6 * purpose with or without fee is hereby granted, provided that the above 7 * copyright notice and this permission notice appear in all copies. 8 * 9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 15 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 16 */ 17 18 #include "includes.h" 19 20 #include <sys/types.h> 21 22 #include <stdio.h> 23 #include <stdlib.h> 24 25 #include "ssh_api.h" 26 #include "compat.h" 27 #include "log.h" 28 #include "authfile.h" 29 #include "sshkey.h" 30 #include "misc.h" 31 #include "ssh2.h" 32 #include "version.h" 33 #include "myproposal.h" 34 #include "ssherr.h" 35 #include "sshbuf.h" 36 37 #include "openbsd-compat/openssl-compat.h" 38 39 #include <string.h> 40 41 int _ssh_exchange_banner(struct ssh *); 42 int _ssh_send_banner(struct ssh *, struct sshbuf *); 43 int _ssh_read_banner(struct ssh *, struct sshbuf *); 44 int _ssh_order_hostkeyalgs(struct ssh *); 45 int _ssh_verify_host_key(struct sshkey *, struct ssh *); 46 struct sshkey *_ssh_host_public_key(int, int, struct ssh *); 47 struct sshkey *_ssh_host_private_key(int, int, struct ssh *); 48 int _ssh_host_key_sign(struct ssh *, struct sshkey *, struct sshkey *, 49 u_char **, size_t *, const u_char *, size_t, const char *); 50 51 /* 52 * stubs for the server side implementation of kex. 53 * disable privsep so our stubs will never be called. 54 */ 55 int use_privsep = 0; 56 int mm_sshkey_sign(struct sshkey *, u_char **, u_int *, 57 u_char *, u_int, char *, u_int); 58 59 #ifdef WITH_OPENSSL 60 DH *mm_choose_dh(int, int, int); 61 #endif 62 63 /* Define these two variables here so that they are part of the library */ 64 u_char *session_id2 = NULL; 65 u_int session_id2_len = 0; 66 67 int 68 mm_sshkey_sign(struct sshkey *key, u_char **sigp, u_int *lenp, 69 u_char *data, u_int datalen, char *alg, u_int compat) 70 { 71 return (-1); 72 } 73 74 #ifdef WITH_OPENSSL 75 DH * 76 mm_choose_dh(int min, int nbits, int max) 77 { 78 return (NULL); 79 } 80 #endif 81 82 /* API */ 83 84 int 85 ssh_init(struct ssh **sshp, int is_server, struct kex_params *kex_params) 86 { 87 char *myproposal[PROPOSAL_MAX] = { KEX_CLIENT }; 88 struct ssh *ssh; 89 char **proposal; 90 static int called; 91 int r; 92 93 if (!called) { 94 seed_rng(); 95 called = 1; 96 } 97 98 if ((ssh = ssh_packet_set_connection(NULL, -1, -1)) == NULL) 99 return SSH_ERR_ALLOC_FAIL; 100 if (is_server) 101 ssh_packet_set_server(ssh); 102 103 /* Initialize key exchange */ 104 proposal = kex_params ? kex_params->proposal : myproposal; 105 if ((r = kex_ready(ssh, proposal)) != 0) { 106 ssh_free(ssh); 107 return r; 108 } 109 ssh->kex->server = is_server; 110 if (is_server) { 111 #ifdef WITH_OPENSSL 112 ssh->kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_server; 113 ssh->kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_server; 114 ssh->kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_server; 115 ssh->kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_server; 116 ssh->kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_server; 117 ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_server; 118 ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_server; 119 # ifdef OPENSSL_HAS_ECC 120 ssh->kex->kex[KEX_ECDH_SHA2] = kex_gen_server; 121 # endif 122 #endif /* WITH_OPENSSL */ 123 ssh->kex->kex[KEX_C25519_SHA256] = kex_gen_server; 124 ssh->kex->kex[KEX_KEM_SNTRUP4591761X25519_SHA512] = kex_gen_server; 125 ssh->kex->load_host_public_key=&_ssh_host_public_key; 126 ssh->kex->load_host_private_key=&_ssh_host_private_key; 127 ssh->kex->sign=&_ssh_host_key_sign; 128 } else { 129 #ifdef WITH_OPENSSL 130 ssh->kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_client; 131 ssh->kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_client; 132 ssh->kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_client; 133 ssh->kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_client; 134 ssh->kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_client; 135 ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_client; 136 ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_client; 137 # ifdef OPENSSL_HAS_ECC 138 ssh->kex->kex[KEX_ECDH_SHA2] = kex_gen_client; 139 # endif 140 #endif /* WITH_OPENSSL */ 141 ssh->kex->kex[KEX_C25519_SHA256] = kex_gen_client; 142 ssh->kex->kex[KEX_KEM_SNTRUP4591761X25519_SHA512] = kex_gen_client; 143 ssh->kex->verify_host_key =&_ssh_verify_host_key; 144 } 145 *sshp = ssh; 146 return 0; 147 } 148 149 void 150 ssh_free(struct ssh *ssh) 151 { 152 struct key_entry *k; 153 154 ssh_packet_close(ssh); 155 /* 156 * we've only created the public keys variants in case we 157 * are a acting as a server. 158 */ 159 while ((k = TAILQ_FIRST(&ssh->public_keys)) != NULL) { 160 TAILQ_REMOVE(&ssh->public_keys, k, next); 161 if (ssh->kex && ssh->kex->server) 162 sshkey_free(k->key); 163 free(k); 164 } 165 while ((k = TAILQ_FIRST(&ssh->private_keys)) != NULL) { 166 TAILQ_REMOVE(&ssh->private_keys, k, next); 167 free(k); 168 } 169 if (ssh->kex) 170 kex_free(ssh->kex); 171 free(ssh); 172 } 173 174 void 175 ssh_set_app_data(struct ssh *ssh, void *app_data) 176 { 177 ssh->app_data = app_data; 178 } 179 180 void * 181 ssh_get_app_data(struct ssh *ssh) 182 { 183 return ssh->app_data; 184 } 185 186 /* Returns < 0 on error, 0 otherwise */ 187 int 188 ssh_add_hostkey(struct ssh *ssh, struct sshkey *key) 189 { 190 struct sshkey *pubkey = NULL; 191 struct key_entry *k = NULL, *k_prv = NULL; 192 int r; 193 194 if (ssh->kex->server) { 195 if ((r = sshkey_from_private(key, &pubkey)) != 0) 196 return r; 197 if ((k = malloc(sizeof(*k))) == NULL || 198 (k_prv = malloc(sizeof(*k_prv))) == NULL) { 199 free(k); 200 sshkey_free(pubkey); 201 return SSH_ERR_ALLOC_FAIL; 202 } 203 k_prv->key = key; 204 TAILQ_INSERT_TAIL(&ssh->private_keys, k_prv, next); 205 206 /* add the public key, too */ 207 k->key = pubkey; 208 TAILQ_INSERT_TAIL(&ssh->public_keys, k, next); 209 r = 0; 210 } else { 211 if ((k = malloc(sizeof(*k))) == NULL) 212 return SSH_ERR_ALLOC_FAIL; 213 k->key = key; 214 TAILQ_INSERT_TAIL(&ssh->public_keys, k, next); 215 r = 0; 216 } 217 218 return r; 219 } 220 221 int 222 ssh_set_verify_host_key_callback(struct ssh *ssh, 223 int (*cb)(struct sshkey *, struct ssh *)) 224 { 225 if (cb == NULL || ssh->kex == NULL) 226 return SSH_ERR_INVALID_ARGUMENT; 227 228 ssh->kex->verify_host_key = cb; 229 230 return 0; 231 } 232 233 int 234 ssh_input_append(struct ssh *ssh, const u_char *data, size_t len) 235 { 236 return sshbuf_put(ssh_packet_get_input(ssh), data, len); 237 } 238 239 int 240 ssh_packet_next(struct ssh *ssh, u_char *typep) 241 { 242 int r; 243 u_int32_t seqnr; 244 u_char type; 245 246 /* 247 * Try to read a packet. Return SSH_MSG_NONE if no packet or not 248 * enough data. 249 */ 250 *typep = SSH_MSG_NONE; 251 if (sshbuf_len(ssh->kex->client_version) == 0 || 252 sshbuf_len(ssh->kex->server_version) == 0) 253 return _ssh_exchange_banner(ssh); 254 /* 255 * If we enough data and a dispatch function then 256 * call the function and get the next packet. 257 * Otherwise return the packet type to the caller so it 258 * can decide how to go on. 259 * 260 * We will only call the dispatch function for: 261 * 20-29 Algorithm negotiation 262 * 30-49 Key exchange method specific (numbers can be reused for 263 * different authentication methods) 264 */ 265 for (;;) { 266 if ((r = ssh_packet_read_poll2(ssh, &type, &seqnr)) != 0) 267 return r; 268 if (type > 0 && type < DISPATCH_MAX && 269 type >= SSH2_MSG_KEXINIT && type <= SSH2_MSG_TRANSPORT_MAX && 270 ssh->dispatch[type] != NULL) { 271 if ((r = (*ssh->dispatch[type])(type, seqnr, ssh)) != 0) 272 return r; 273 } else { 274 *typep = type; 275 return 0; 276 } 277 } 278 } 279 280 const u_char * 281 ssh_packet_payload(struct ssh *ssh, size_t *lenp) 282 { 283 return sshpkt_ptr(ssh, lenp); 284 } 285 286 int 287 ssh_packet_put(struct ssh *ssh, int type, const u_char *data, size_t len) 288 { 289 int r; 290 291 if ((r = sshpkt_start(ssh, type)) != 0 || 292 (r = sshpkt_put(ssh, data, len)) != 0 || 293 (r = sshpkt_send(ssh)) != 0) 294 return r; 295 return 0; 296 } 297 298 const u_char * 299 ssh_output_ptr(struct ssh *ssh, size_t *len) 300 { 301 struct sshbuf *output = ssh_packet_get_output(ssh); 302 303 *len = sshbuf_len(output); 304 return sshbuf_ptr(output); 305 } 306 307 int 308 ssh_output_consume(struct ssh *ssh, size_t len) 309 { 310 return sshbuf_consume(ssh_packet_get_output(ssh), len); 311 } 312 313 int 314 ssh_output_space(struct ssh *ssh, size_t len) 315 { 316 return (0 == sshbuf_check_reserve(ssh_packet_get_output(ssh), len)); 317 } 318 319 int 320 ssh_input_space(struct ssh *ssh, size_t len) 321 { 322 return (0 == sshbuf_check_reserve(ssh_packet_get_input(ssh), len)); 323 } 324 325 /* Read other side's version identification. */ 326 int 327 _ssh_read_banner(struct ssh *ssh, struct sshbuf *banner) 328 { 329 struct sshbuf *input = ssh_packet_get_input(ssh); 330 const char *mismatch = "Protocol mismatch.\r\n"; 331 const u_char *s = sshbuf_ptr(input); 332 u_char c; 333 char *cp = NULL, *remote_version = NULL; 334 int r = 0, remote_major, remote_minor, expect_nl; 335 size_t n, j; 336 337 for (j = n = 0;;) { 338 sshbuf_reset(banner); 339 expect_nl = 0; 340 for (;;) { 341 if (j >= sshbuf_len(input)) 342 return 0; /* insufficient data in input buf */ 343 c = s[j++]; 344 if (c == '\r') { 345 expect_nl = 1; 346 continue; 347 } 348 if (c == '\n') 349 break; 350 if (expect_nl) 351 goto bad; 352 if ((r = sshbuf_put_u8(banner, c)) != 0) 353 return r; 354 if (sshbuf_len(banner) > SSH_MAX_BANNER_LEN) 355 goto bad; 356 } 357 if (sshbuf_len(banner) >= 4 && 358 memcmp(sshbuf_ptr(banner), "SSH-", 4) == 0) 359 break; 360 debug("%s: %.*s", __func__, (int)sshbuf_len(banner), 361 sshbuf_ptr(banner)); 362 /* Accept lines before banner only on client */ 363 if (ssh->kex->server || ++n > SSH_MAX_PRE_BANNER_LINES) { 364 bad: 365 if ((r = sshbuf_put(ssh_packet_get_output(ssh), 366 mismatch, strlen(mismatch))) != 0) 367 return r; 368 return SSH_ERR_NO_PROTOCOL_VERSION; 369 } 370 } 371 if ((r = sshbuf_consume(input, j)) != 0) 372 return r; 373 374 /* XXX remote version must be the same size as banner for sscanf */ 375 if ((cp = sshbuf_dup_string(banner)) == NULL || 376 (remote_version = calloc(1, sshbuf_len(banner))) == NULL) { 377 r = SSH_ERR_ALLOC_FAIL; 378 goto out; 379 } 380 381 /* 382 * Check that the versions match. In future this might accept 383 * several versions and set appropriate flags to handle them. 384 */ 385 if (sscanf(cp, "SSH-%d.%d-%[^\n]\n", 386 &remote_major, &remote_minor, remote_version) != 3) { 387 r = SSH_ERR_INVALID_FORMAT; 388 goto out; 389 } 390 debug("Remote protocol version %d.%d, remote software version %.100s", 391 remote_major, remote_minor, remote_version); 392 393 ssh->compat = compat_datafellows(remote_version); 394 if (remote_major == 1 && remote_minor == 99) { 395 remote_major = 2; 396 remote_minor = 0; 397 } 398 if (remote_major != 2) 399 r = SSH_ERR_PROTOCOL_MISMATCH; 400 401 debug("Remote version string %.100s", cp); 402 out: 403 free(cp); 404 free(remote_version); 405 return r; 406 } 407 408 /* Send our own protocol version identification. */ 409 int 410 _ssh_send_banner(struct ssh *ssh, struct sshbuf *banner) 411 { 412 char *cp; 413 int r; 414 415 if ((r = sshbuf_putf(banner, "SSH-2.0-%.100s\r\n", SSH_VERSION)) != 0) 416 return r; 417 if ((r = sshbuf_putb(ssh_packet_get_output(ssh), banner)) != 0) 418 return r; 419 /* Remove trailing \r\n */ 420 if ((r = sshbuf_consume_end(banner, 2)) != 0) 421 return r; 422 if ((cp = sshbuf_dup_string(banner)) == NULL) 423 return SSH_ERR_ALLOC_FAIL; 424 debug("Local version string %.100s", cp); 425 free(cp); 426 return 0; 427 } 428 429 int 430 _ssh_exchange_banner(struct ssh *ssh) 431 { 432 struct kex *kex = ssh->kex; 433 int r; 434 435 /* 436 * if _ssh_read_banner() cannot parse a full version string 437 * it will return NULL and we end up calling it again. 438 */ 439 440 r = 0; 441 if (kex->server) { 442 if (sshbuf_len(ssh->kex->server_version) == 0) 443 r = _ssh_send_banner(ssh, ssh->kex->server_version); 444 if (r == 0 && 445 sshbuf_len(ssh->kex->server_version) != 0 && 446 sshbuf_len(ssh->kex->client_version) == 0) 447 r = _ssh_read_banner(ssh, ssh->kex->client_version); 448 } else { 449 if (sshbuf_len(ssh->kex->server_version) == 0) 450 r = _ssh_read_banner(ssh, ssh->kex->server_version); 451 if (r == 0 && 452 sshbuf_len(ssh->kex->server_version) != 0 && 453 sshbuf_len(ssh->kex->client_version) == 0) 454 r = _ssh_send_banner(ssh, ssh->kex->client_version); 455 } 456 if (r != 0) 457 return r; 458 /* start initial kex as soon as we have exchanged the banners */ 459 if (sshbuf_len(ssh->kex->server_version) != 0 && 460 sshbuf_len(ssh->kex->client_version) != 0) { 461 if ((r = _ssh_order_hostkeyalgs(ssh)) != 0 || 462 (r = kex_send_kexinit(ssh)) != 0) 463 return r; 464 } 465 return 0; 466 } 467 468 struct sshkey * 469 _ssh_host_public_key(int type, int nid, struct ssh *ssh) 470 { 471 struct key_entry *k; 472 473 debug3("%s: need %d", __func__, type); 474 TAILQ_FOREACH(k, &ssh->public_keys, next) { 475 debug3("%s: check %s", __func__, sshkey_type(k->key)); 476 if (k->key->type == type && 477 (type != KEY_ECDSA || k->key->ecdsa_nid == nid)) 478 return (k->key); 479 } 480 return (NULL); 481 } 482 483 struct sshkey * 484 _ssh_host_private_key(int type, int nid, struct ssh *ssh) 485 { 486 struct key_entry *k; 487 488 debug3("%s: need %d", __func__, type); 489 TAILQ_FOREACH(k, &ssh->private_keys, next) { 490 debug3("%s: check %s", __func__, sshkey_type(k->key)); 491 if (k->key->type == type && 492 (type != KEY_ECDSA || k->key->ecdsa_nid == nid)) 493 return (k->key); 494 } 495 return (NULL); 496 } 497 498 int 499 _ssh_verify_host_key(struct sshkey *hostkey, struct ssh *ssh) 500 { 501 struct key_entry *k; 502 503 debug3("%s: need %s", __func__, sshkey_type(hostkey)); 504 TAILQ_FOREACH(k, &ssh->public_keys, next) { 505 debug3("%s: check %s", __func__, sshkey_type(k->key)); 506 if (sshkey_equal_public(hostkey, k->key)) 507 return (0); /* ok */ 508 } 509 return (-1); /* failed */ 510 } 511 512 /* offer hostkey algorithms in kexinit depending on registered keys */ 513 int 514 _ssh_order_hostkeyalgs(struct ssh *ssh) 515 { 516 struct key_entry *k; 517 char *orig, *avail, *oavail = NULL, *alg, *replace = NULL; 518 char **proposal; 519 size_t maxlen; 520 int ktype, r; 521 522 /* XXX we de-serialize ssh->kex->my, modify it, and change it */ 523 if ((r = kex_buf2prop(ssh->kex->my, NULL, &proposal)) != 0) 524 return r; 525 orig = proposal[PROPOSAL_SERVER_HOST_KEY_ALGS]; 526 if ((oavail = avail = strdup(orig)) == NULL) { 527 r = SSH_ERR_ALLOC_FAIL; 528 goto out; 529 } 530 maxlen = strlen(avail) + 1; 531 if ((replace = calloc(1, maxlen)) == NULL) { 532 r = SSH_ERR_ALLOC_FAIL; 533 goto out; 534 } 535 *replace = '\0'; 536 while ((alg = strsep(&avail, ",")) && *alg != '\0') { 537 if ((ktype = sshkey_type_from_name(alg)) == KEY_UNSPEC) 538 continue; 539 TAILQ_FOREACH(k, &ssh->public_keys, next) { 540 if (k->key->type == ktype || 541 (sshkey_is_cert(k->key) && k->key->type == 542 sshkey_type_plain(ktype))) { 543 if (*replace != '\0') 544 strlcat(replace, ",", maxlen); 545 strlcat(replace, alg, maxlen); 546 break; 547 } 548 } 549 } 550 if (*replace != '\0') { 551 debug2("%s: orig/%d %s", __func__, ssh->kex->server, orig); 552 debug2("%s: replace/%d %s", __func__, ssh->kex->server, replace); 553 free(orig); 554 proposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = replace; 555 replace = NULL; /* owned by proposal */ 556 r = kex_prop2buf(ssh->kex->my, proposal); 557 } 558 out: 559 free(oavail); 560 free(replace); 561 kex_prop_free(proposal); 562 return r; 563 } 564 565 int 566 _ssh_host_key_sign(struct ssh *ssh, struct sshkey *privkey, 567 struct sshkey *pubkey, u_char **signature, size_t *slen, 568 const u_char *data, size_t dlen, const char *alg) 569 { 570 return sshkey_sign(privkey, signature, slen, data, dlen, 571 alg, ssh->compat); 572 } 573