1 /* $OpenBSD: ssh_api.c,v 1.15 2019/01/21 10:38:54 djm 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 "ssh_api.h" 21 #include "compat.h" 22 #include "log.h" 23 #include "authfile.h" 24 #include "sshkey.h" 25 #include "misc.h" 26 #include "ssh2.h" 27 #include "version.h" 28 #include "myproposal.h" 29 #include "ssherr.h" 30 #include "sshbuf.h" 31 32 #include "openbsd-compat/openssl-compat.h" 33 34 #include <string.h> 35 36 int _ssh_exchange_banner(struct ssh *); 37 int _ssh_send_banner(struct ssh *, struct sshbuf *); 38 int _ssh_read_banner(struct ssh *, struct sshbuf *); 39 int _ssh_order_hostkeyalgs(struct ssh *); 40 int _ssh_verify_host_key(struct sshkey *, struct ssh *); 41 struct sshkey *_ssh_host_public_key(int, int, struct ssh *); 42 struct sshkey *_ssh_host_private_key(int, int, struct ssh *); 43 int _ssh_host_key_sign(struct ssh *, struct sshkey *, struct sshkey *, 44 u_char **, size_t *, const u_char *, size_t, const char *); 45 46 /* 47 * stubs for the server side implementation of kex. 48 * disable privsep so our stubs will never be called. 49 */ 50 int use_privsep = 0; 51 int mm_sshkey_sign(struct sshkey *, u_char **, u_int *, 52 u_char *, u_int, char *, u_int); 53 DH *mm_choose_dh(int, int, int); 54 55 /* Define these two variables here so that they are part of the library */ 56 u_char *session_id2 = NULL; 57 u_int session_id2_len = 0; 58 59 int 60 mm_sshkey_sign(struct sshkey *key, u_char **sigp, u_int *lenp, 61 u_char *data, u_int datalen, char *alg, u_int compat) 62 { 63 return (-1); 64 } 65 66 DH * 67 mm_choose_dh(int min, int nbits, int max) 68 { 69 return (NULL); 70 } 71 72 /* API */ 73 74 int 75 ssh_init(struct ssh **sshp, int is_server, struct kex_params *kex_params) 76 { 77 char *myproposal[PROPOSAL_MAX] = { KEX_CLIENT }; 78 struct ssh *ssh; 79 char **proposal; 80 static int called; 81 int r; 82 83 if (!called) { 84 seed_rng(); 85 called = 1; 86 } 87 88 if ((ssh = ssh_packet_set_connection(NULL, -1, -1)) == NULL) 89 return SSH_ERR_ALLOC_FAIL; 90 if (is_server) 91 ssh_packet_set_server(ssh); 92 93 /* Initialize key exchange */ 94 proposal = kex_params ? kex_params->proposal : myproposal; 95 if ((r = kex_ready(ssh, proposal)) != 0) { 96 ssh_free(ssh); 97 return r; 98 } 99 ssh->kex->server = is_server; 100 if (is_server) { 101 #ifdef WITH_OPENSSL 102 ssh->kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_server; 103 ssh->kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_server; 104 ssh->kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_server; 105 ssh->kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_server; 106 ssh->kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_server; 107 ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_server; 108 ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_server; 109 # ifdef OPENSSL_HAS_ECC 110 ssh->kex->kex[KEX_ECDH_SHA2] = kex_gen_server; 111 # endif 112 #endif /* WITH_OPENSSL */ 113 ssh->kex->kex[KEX_C25519_SHA256] = kex_gen_server; 114 ssh->kex->kex[KEX_KEM_SNTRUP4591761X25519_SHA512] = kex_gen_server; 115 ssh->kex->load_host_public_key=&_ssh_host_public_key; 116 ssh->kex->load_host_private_key=&_ssh_host_private_key; 117 ssh->kex->sign=&_ssh_host_key_sign; 118 } else { 119 #ifdef WITH_OPENSSL 120 ssh->kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_client; 121 ssh->kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_client; 122 ssh->kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_client; 123 ssh->kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_client; 124 ssh->kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_client; 125 ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_client; 126 ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_client; 127 # ifdef OPENSSL_HAS_ECC 128 ssh->kex->kex[KEX_ECDH_SHA2] = kex_gen_client; 129 # endif 130 #endif /* WITH_OPENSSL */ 131 ssh->kex->kex[KEX_C25519_SHA256] = kex_gen_client; 132 ssh->kex->kex[KEX_KEM_SNTRUP4591761X25519_SHA512] = kex_gen_client; 133 ssh->kex->verify_host_key =&_ssh_verify_host_key; 134 } 135 *sshp = ssh; 136 return 0; 137 } 138 139 void 140 ssh_free(struct ssh *ssh) 141 { 142 struct key_entry *k; 143 144 ssh_packet_close(ssh); 145 /* 146 * we've only created the public keys variants in case we 147 * are a acting as a server. 148 */ 149 while ((k = TAILQ_FIRST(&ssh->public_keys)) != NULL) { 150 TAILQ_REMOVE(&ssh->public_keys, k, next); 151 if (ssh->kex && ssh->kex->server) 152 sshkey_free(k->key); 153 free(k); 154 } 155 while ((k = TAILQ_FIRST(&ssh->private_keys)) != NULL) { 156 TAILQ_REMOVE(&ssh->private_keys, k, next); 157 free(k); 158 } 159 if (ssh->kex) 160 kex_free(ssh->kex); 161 free(ssh); 162 } 163 164 void 165 ssh_set_app_data(struct ssh *ssh, void *app_data) 166 { 167 ssh->app_data = app_data; 168 } 169 170 void * 171 ssh_get_app_data(struct ssh *ssh) 172 { 173 return ssh->app_data; 174 } 175 176 /* Returns < 0 on error, 0 otherwise */ 177 int 178 ssh_add_hostkey(struct ssh *ssh, struct sshkey *key) 179 { 180 struct sshkey *pubkey = NULL; 181 struct key_entry *k = NULL, *k_prv = NULL; 182 int r; 183 184 if (ssh->kex->server) { 185 if ((r = sshkey_from_private(key, &pubkey)) != 0) 186 return r; 187 if ((k = malloc(sizeof(*k))) == NULL || 188 (k_prv = malloc(sizeof(*k_prv))) == NULL) { 189 free(k); 190 sshkey_free(pubkey); 191 return SSH_ERR_ALLOC_FAIL; 192 } 193 k_prv->key = key; 194 TAILQ_INSERT_TAIL(&ssh->private_keys, k_prv, next); 195 196 /* add the public key, too */ 197 k->key = pubkey; 198 TAILQ_INSERT_TAIL(&ssh->public_keys, k, next); 199 r = 0; 200 } else { 201 if ((k = malloc(sizeof(*k))) == NULL) 202 return SSH_ERR_ALLOC_FAIL; 203 k->key = key; 204 TAILQ_INSERT_TAIL(&ssh->public_keys, k, next); 205 r = 0; 206 } 207 208 return r; 209 } 210 211 int 212 ssh_set_verify_host_key_callback(struct ssh *ssh, 213 int (*cb)(struct sshkey *, struct ssh *)) 214 { 215 if (cb == NULL || ssh->kex == NULL) 216 return SSH_ERR_INVALID_ARGUMENT; 217 218 ssh->kex->verify_host_key = cb; 219 220 return 0; 221 } 222 223 int 224 ssh_input_append(struct ssh *ssh, const u_char *data, size_t len) 225 { 226 return sshbuf_put(ssh_packet_get_input(ssh), data, len); 227 } 228 229 int 230 ssh_packet_next(struct ssh *ssh, u_char *typep) 231 { 232 int r; 233 u_int32_t seqnr; 234 u_char type; 235 236 /* 237 * Try to read a packet. Return SSH_MSG_NONE if no packet or not 238 * enough data. 239 */ 240 *typep = SSH_MSG_NONE; 241 if (sshbuf_len(ssh->kex->client_version) == 0 || 242 sshbuf_len(ssh->kex->server_version) == 0) 243 return _ssh_exchange_banner(ssh); 244 /* 245 * If we enough data and a dispatch function then 246 * call the function and get the next packet. 247 * Otherwise return the packet type to the caller so it 248 * can decide how to go on. 249 * 250 * We will only call the dispatch function for: 251 * 20-29 Algorithm negotiation 252 * 30-49 Key exchange method specific (numbers can be reused for 253 * different authentication methods) 254 */ 255 for (;;) { 256 if ((r = ssh_packet_read_poll2(ssh, &type, &seqnr)) != 0) 257 return r; 258 if (type > 0 && type < DISPATCH_MAX && 259 type >= SSH2_MSG_KEXINIT && type <= SSH2_MSG_TRANSPORT_MAX && 260 ssh->dispatch[type] != NULL) { 261 if ((r = (*ssh->dispatch[type])(type, seqnr, ssh)) != 0) 262 return r; 263 } else { 264 *typep = type; 265 return 0; 266 } 267 } 268 } 269 270 const u_char * 271 ssh_packet_payload(struct ssh *ssh, size_t *lenp) 272 { 273 return sshpkt_ptr(ssh, lenp); 274 } 275 276 int 277 ssh_packet_put(struct ssh *ssh, int type, const u_char *data, size_t len) 278 { 279 int r; 280 281 if ((r = sshpkt_start(ssh, type)) != 0 || 282 (r = sshpkt_put(ssh, data, len)) != 0 || 283 (r = sshpkt_send(ssh)) != 0) 284 return r; 285 return 0; 286 } 287 288 const u_char * 289 ssh_output_ptr(struct ssh *ssh, size_t *len) 290 { 291 struct sshbuf *output = ssh_packet_get_output(ssh); 292 293 *len = sshbuf_len(output); 294 return sshbuf_ptr(output); 295 } 296 297 int 298 ssh_output_consume(struct ssh *ssh, size_t len) 299 { 300 return sshbuf_consume(ssh_packet_get_output(ssh), len); 301 } 302 303 int 304 ssh_output_space(struct ssh *ssh, size_t len) 305 { 306 return (0 == sshbuf_check_reserve(ssh_packet_get_output(ssh), len)); 307 } 308 309 int 310 ssh_input_space(struct ssh *ssh, size_t len) 311 { 312 return (0 == sshbuf_check_reserve(ssh_packet_get_input(ssh), len)); 313 } 314 315 /* Read other side's version identification. */ 316 int 317 _ssh_read_banner(struct ssh *ssh, struct sshbuf *banner) 318 { 319 struct sshbuf *input = ssh_packet_get_input(ssh); 320 const char *mismatch = "Protocol mismatch.\r\n"; 321 const u_char *s = sshbuf_ptr(input); 322 u_char c; 323 char *cp, *remote_version; 324 int r, remote_major, remote_minor, expect_nl; 325 size_t n, j; 326 327 for (j = n = 0;;) { 328 sshbuf_reset(banner); 329 expect_nl = 0; 330 for (;;) { 331 if (j >= sshbuf_len(input)) 332 return 0; /* insufficient data in input buf */ 333 c = s[j++]; 334 if (c == '\r') { 335 expect_nl = 1; 336 continue; 337 } 338 if (c == '\n') 339 break; 340 if (expect_nl) 341 goto bad; 342 if ((r = sshbuf_put_u8(banner, c)) != 0) 343 return r; 344 if (sshbuf_len(banner) > SSH_MAX_BANNER_LEN) 345 goto bad; 346 } 347 if (sshbuf_len(banner) >= 4 && 348 memcmp(sshbuf_ptr(banner), "SSH-", 4) == 0) 349 break; 350 if ((cp = sshbuf_dup_string(banner)) == NULL) 351 return SSH_ERR_ALLOC_FAIL; 352 debug("%s: %s", __func__, cp); 353 free(cp); 354 /* Accept lines before banner only on client */ 355 if (ssh->kex->server || ++n > SSH_MAX_PRE_BANNER_LINES) { 356 bad: 357 if ((r = sshbuf_put(ssh_packet_get_output(ssh), 358 mismatch, strlen(mismatch))) != 0) 359 return r; 360 return SSH_ERR_NO_PROTOCOL_VERSION; 361 } 362 } 363 if ((r = sshbuf_consume(input, j)) != 0) 364 return r; 365 366 if ((cp = sshbuf_dup_string(banner)) == NULL) 367 return SSH_ERR_ALLOC_FAIL; 368 /* XXX remote version must be the same size as banner for sscanf */ 369 if ((remote_version = calloc(1, sshbuf_len(banner))) == NULL) 370 return SSH_ERR_ALLOC_FAIL; 371 372 /* 373 * Check that the versions match. In future this might accept 374 * several versions and set appropriate flags to handle them. 375 */ 376 if (sscanf(cp, "SSH-%d.%d-%[^\n]\n", 377 &remote_major, &remote_minor, remote_version) != 3) 378 return SSH_ERR_INVALID_FORMAT; 379 debug("Remote protocol version %d.%d, remote software version %.100s", 380 remote_major, remote_minor, remote_version); 381 382 ssh->compat = compat_datafellows(remote_version); 383 if (remote_major == 1 && remote_minor == 99) { 384 remote_major = 2; 385 remote_minor = 0; 386 } 387 if (remote_major != 2) 388 return SSH_ERR_PROTOCOL_MISMATCH; 389 debug("Remote version string %.100s", cp); 390 free(cp); 391 return 0; 392 } 393 394 /* Send our own protocol version identification. */ 395 int 396 _ssh_send_banner(struct ssh *ssh, struct sshbuf *banner) 397 { 398 char *cp; 399 int r; 400 401 if ((r = sshbuf_putf(banner, "SSH-2.0-%.100s\r\n", SSH_VERSION)) != 0) 402 return r; 403 if ((r = sshbuf_putb(ssh_packet_get_output(ssh), banner)) != 0) 404 return r; 405 /* Remove trailing \r\n */ 406 if ((r = sshbuf_consume_end(banner, 2)) != 0) 407 return r; 408 if ((cp = sshbuf_dup_string(banner)) == NULL) 409 return SSH_ERR_ALLOC_FAIL; 410 debug("Local version string %.100s", cp); 411 free(cp); 412 return 0; 413 } 414 415 int 416 _ssh_exchange_banner(struct ssh *ssh) 417 { 418 struct kex *kex = ssh->kex; 419 int r; 420 421 /* 422 * if _ssh_read_banner() cannot parse a full version string 423 * it will return NULL and we end up calling it again. 424 */ 425 426 r = 0; 427 if (kex->server) { 428 if (sshbuf_len(ssh->kex->server_version) == 0) 429 r = _ssh_send_banner(ssh, ssh->kex->server_version); 430 if (r == 0 && 431 sshbuf_len(ssh->kex->server_version) != 0 && 432 sshbuf_len(ssh->kex->client_version) == 0) 433 r = _ssh_read_banner(ssh, ssh->kex->client_version); 434 } else { 435 if (sshbuf_len(ssh->kex->server_version) == 0) 436 r = _ssh_read_banner(ssh, ssh->kex->server_version); 437 if (r == 0 && 438 sshbuf_len(ssh->kex->server_version) != 0 && 439 sshbuf_len(ssh->kex->client_version) == 0) 440 r = _ssh_send_banner(ssh, ssh->kex->client_version); 441 } 442 if (r != 0) 443 return r; 444 /* start initial kex as soon as we have exchanged the banners */ 445 if (sshbuf_len(ssh->kex->server_version) != 0 && 446 sshbuf_len(ssh->kex->client_version) != 0) { 447 if ((r = _ssh_order_hostkeyalgs(ssh)) != 0 || 448 (r = kex_send_kexinit(ssh)) != 0) 449 return r; 450 } 451 return 0; 452 } 453 454 struct sshkey * 455 _ssh_host_public_key(int type, int nid, struct ssh *ssh) 456 { 457 struct key_entry *k; 458 459 debug3("%s: need %d", __func__, type); 460 TAILQ_FOREACH(k, &ssh->public_keys, next) { 461 debug3("%s: check %s", __func__, sshkey_type(k->key)); 462 if (k->key->type == type && 463 (type != KEY_ECDSA || k->key->ecdsa_nid == nid)) 464 return (k->key); 465 } 466 return (NULL); 467 } 468 469 struct sshkey * 470 _ssh_host_private_key(int type, int nid, struct ssh *ssh) 471 { 472 struct key_entry *k; 473 474 debug3("%s: need %d", __func__, type); 475 TAILQ_FOREACH(k, &ssh->private_keys, next) { 476 debug3("%s: check %s", __func__, sshkey_type(k->key)); 477 if (k->key->type == type && 478 (type != KEY_ECDSA || k->key->ecdsa_nid == nid)) 479 return (k->key); 480 } 481 return (NULL); 482 } 483 484 int 485 _ssh_verify_host_key(struct sshkey *hostkey, struct ssh *ssh) 486 { 487 struct key_entry *k; 488 489 debug3("%s: need %s", __func__, sshkey_type(hostkey)); 490 TAILQ_FOREACH(k, &ssh->public_keys, next) { 491 debug3("%s: check %s", __func__, sshkey_type(k->key)); 492 if (sshkey_equal_public(hostkey, k->key)) 493 return (0); /* ok */ 494 } 495 return (-1); /* failed */ 496 } 497 498 /* offer hostkey algorithms in kexinit depending on registered keys */ 499 int 500 _ssh_order_hostkeyalgs(struct ssh *ssh) 501 { 502 struct key_entry *k; 503 char *orig, *avail, *oavail = NULL, *alg, *replace = NULL; 504 char **proposal; 505 size_t maxlen; 506 int ktype, r; 507 508 /* XXX we de-serialize ssh->kex->my, modify it, and change it */ 509 if ((r = kex_buf2prop(ssh->kex->my, NULL, &proposal)) != 0) 510 return r; 511 orig = proposal[PROPOSAL_SERVER_HOST_KEY_ALGS]; 512 if ((oavail = avail = strdup(orig)) == NULL) { 513 r = SSH_ERR_ALLOC_FAIL; 514 goto out; 515 } 516 maxlen = strlen(avail) + 1; 517 if ((replace = calloc(1, maxlen)) == NULL) { 518 r = SSH_ERR_ALLOC_FAIL; 519 goto out; 520 } 521 *replace = '\0'; 522 while ((alg = strsep(&avail, ",")) && *alg != '\0') { 523 if ((ktype = sshkey_type_from_name(alg)) == KEY_UNSPEC) 524 continue; 525 TAILQ_FOREACH(k, &ssh->public_keys, next) { 526 if (k->key->type == ktype || 527 (sshkey_is_cert(k->key) && k->key->type == 528 sshkey_type_plain(ktype))) { 529 if (*replace != '\0') 530 strlcat(replace, ",", maxlen); 531 strlcat(replace, alg, maxlen); 532 break; 533 } 534 } 535 } 536 if (*replace != '\0') { 537 debug2("%s: orig/%d %s", __func__, ssh->kex->server, orig); 538 debug2("%s: replace/%d %s", __func__, ssh->kex->server, replace); 539 free(orig); 540 proposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = replace; 541 replace = NULL; /* owned by proposal */ 542 r = kex_prop2buf(ssh->kex->my, proposal); 543 } 544 out: 545 free(oavail); 546 free(replace); 547 kex_prop_free(proposal); 548 return r; 549 } 550 551 int 552 _ssh_host_key_sign(struct ssh *ssh, struct sshkey *privkey, 553 struct sshkey *pubkey, u_char **signature, size_t *slen, 554 const u_char *data, size_t dlen, const char *alg) 555 { 556 return sshkey_sign(privkey, signature, slen, data, dlen, 557 alg, ssh->compat); 558 } 559