1 /* $OpenBSD: ssh_api.c,v 1.19 2019/10/31 21:23:19 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 <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 const u_char *, u_int, const char *, const 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 const u_char *data, u_int datalen, const char *alg, const char *sk_provider, 70 u_int compat) 71 { 72 return (-1); 73 } 74 75 #ifdef WITH_OPENSSL 76 DH * 77 mm_choose_dh(int min, int nbits, int max) 78 { 79 return (NULL); 80 } 81 #endif 82 83 /* API */ 84 85 int 86 ssh_init(struct ssh **sshp, int is_server, struct kex_params *kex_params) 87 { 88 char *myproposal[PROPOSAL_MAX] = { KEX_CLIENT }; 89 struct ssh *ssh; 90 char **proposal; 91 static int called; 92 int r; 93 94 if (!called) { 95 seed_rng(); 96 called = 1; 97 } 98 99 if ((ssh = ssh_packet_set_connection(NULL, -1, -1)) == NULL) 100 return SSH_ERR_ALLOC_FAIL; 101 if (is_server) 102 ssh_packet_set_server(ssh); 103 104 /* Initialize key exchange */ 105 proposal = kex_params ? kex_params->proposal : myproposal; 106 if ((r = kex_ready(ssh, proposal)) != 0) { 107 ssh_free(ssh); 108 return r; 109 } 110 ssh->kex->server = is_server; 111 if (is_server) { 112 #ifdef WITH_OPENSSL 113 ssh->kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_server; 114 ssh->kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_server; 115 ssh->kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_server; 116 ssh->kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_server; 117 ssh->kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_server; 118 ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_server; 119 ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_server; 120 # ifdef OPENSSL_HAS_ECC 121 ssh->kex->kex[KEX_ECDH_SHA2] = kex_gen_server; 122 # endif 123 #endif /* WITH_OPENSSL */ 124 ssh->kex->kex[KEX_C25519_SHA256] = kex_gen_server; 125 ssh->kex->kex[KEX_KEM_SNTRUP4591761X25519_SHA512] = kex_gen_server; 126 ssh->kex->load_host_public_key=&_ssh_host_public_key; 127 ssh->kex->load_host_private_key=&_ssh_host_private_key; 128 ssh->kex->sign=&_ssh_host_key_sign; 129 } else { 130 #ifdef WITH_OPENSSL 131 ssh->kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_client; 132 ssh->kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_client; 133 ssh->kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_client; 134 ssh->kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_client; 135 ssh->kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_client; 136 ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_client; 137 ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_client; 138 # ifdef OPENSSL_HAS_ECC 139 ssh->kex->kex[KEX_ECDH_SHA2] = kex_gen_client; 140 # endif 141 #endif /* WITH_OPENSSL */ 142 ssh->kex->kex[KEX_C25519_SHA256] = kex_gen_client; 143 ssh->kex->kex[KEX_KEM_SNTRUP4591761X25519_SHA512] = kex_gen_client; 144 ssh->kex->verify_host_key =&_ssh_verify_host_key; 145 } 146 *sshp = ssh; 147 return 0; 148 } 149 150 void 151 ssh_free(struct ssh *ssh) 152 { 153 struct key_entry *k; 154 155 ssh_packet_close(ssh); 156 /* 157 * we've only created the public keys variants in case we 158 * are a acting as a server. 159 */ 160 while ((k = TAILQ_FIRST(&ssh->public_keys)) != NULL) { 161 TAILQ_REMOVE(&ssh->public_keys, k, next); 162 if (ssh->kex && ssh->kex->server) 163 sshkey_free(k->key); 164 free(k); 165 } 166 while ((k = TAILQ_FIRST(&ssh->private_keys)) != NULL) { 167 TAILQ_REMOVE(&ssh->private_keys, k, next); 168 free(k); 169 } 170 if (ssh->kex) 171 kex_free(ssh->kex); 172 free(ssh); 173 } 174 175 void 176 ssh_set_app_data(struct ssh *ssh, void *app_data) 177 { 178 ssh->app_data = app_data; 179 } 180 181 void * 182 ssh_get_app_data(struct ssh *ssh) 183 { 184 return ssh->app_data; 185 } 186 187 /* Returns < 0 on error, 0 otherwise */ 188 int 189 ssh_add_hostkey(struct ssh *ssh, struct sshkey *key) 190 { 191 struct sshkey *pubkey = NULL; 192 struct key_entry *k = NULL, *k_prv = NULL; 193 int r; 194 195 if (ssh->kex->server) { 196 if ((r = sshkey_from_private(key, &pubkey)) != 0) 197 return r; 198 if ((k = malloc(sizeof(*k))) == NULL || 199 (k_prv = malloc(sizeof(*k_prv))) == NULL) { 200 free(k); 201 sshkey_free(pubkey); 202 return SSH_ERR_ALLOC_FAIL; 203 } 204 k_prv->key = key; 205 TAILQ_INSERT_TAIL(&ssh->private_keys, k_prv, next); 206 207 /* add the public key, too */ 208 k->key = pubkey; 209 TAILQ_INSERT_TAIL(&ssh->public_keys, k, next); 210 r = 0; 211 } else { 212 if ((k = malloc(sizeof(*k))) == NULL) 213 return SSH_ERR_ALLOC_FAIL; 214 k->key = key; 215 TAILQ_INSERT_TAIL(&ssh->public_keys, k, next); 216 r = 0; 217 } 218 219 return r; 220 } 221 222 int 223 ssh_set_verify_host_key_callback(struct ssh *ssh, 224 int (*cb)(struct sshkey *, struct ssh *)) 225 { 226 if (cb == NULL || ssh->kex == NULL) 227 return SSH_ERR_INVALID_ARGUMENT; 228 229 ssh->kex->verify_host_key = cb; 230 231 return 0; 232 } 233 234 int 235 ssh_input_append(struct ssh *ssh, const u_char *data, size_t len) 236 { 237 return sshbuf_put(ssh_packet_get_input(ssh), data, len); 238 } 239 240 int 241 ssh_packet_next(struct ssh *ssh, u_char *typep) 242 { 243 int r; 244 u_int32_t seqnr; 245 u_char type; 246 247 /* 248 * Try to read a packet. Return SSH_MSG_NONE if no packet or not 249 * enough data. 250 */ 251 *typep = SSH_MSG_NONE; 252 if (sshbuf_len(ssh->kex->client_version) == 0 || 253 sshbuf_len(ssh->kex->server_version) == 0) 254 return _ssh_exchange_banner(ssh); 255 /* 256 * If we enough data and a dispatch function then 257 * call the function and get the next packet. 258 * Otherwise return the packet type to the caller so it 259 * can decide how to go on. 260 * 261 * We will only call the dispatch function for: 262 * 20-29 Algorithm negotiation 263 * 30-49 Key exchange method specific (numbers can be reused for 264 * different authentication methods) 265 */ 266 for (;;) { 267 if ((r = ssh_packet_read_poll2(ssh, &type, &seqnr)) != 0) 268 return r; 269 if (type > 0 && type < DISPATCH_MAX && 270 type >= SSH2_MSG_KEXINIT && type <= SSH2_MSG_TRANSPORT_MAX && 271 ssh->dispatch[type] != NULL) { 272 if ((r = (*ssh->dispatch[type])(type, seqnr, ssh)) != 0) 273 return r; 274 } else { 275 *typep = type; 276 return 0; 277 } 278 } 279 } 280 281 const u_char * 282 ssh_packet_payload(struct ssh *ssh, size_t *lenp) 283 { 284 return sshpkt_ptr(ssh, lenp); 285 } 286 287 int 288 ssh_packet_put(struct ssh *ssh, int type, const u_char *data, size_t len) 289 { 290 int r; 291 292 if ((r = sshpkt_start(ssh, type)) != 0 || 293 (r = sshpkt_put(ssh, data, len)) != 0 || 294 (r = sshpkt_send(ssh)) != 0) 295 return r; 296 return 0; 297 } 298 299 const u_char * 300 ssh_output_ptr(struct ssh *ssh, size_t *len) 301 { 302 struct sshbuf *output = ssh_packet_get_output(ssh); 303 304 *len = sshbuf_len(output); 305 return sshbuf_ptr(output); 306 } 307 308 int 309 ssh_output_consume(struct ssh *ssh, size_t len) 310 { 311 return sshbuf_consume(ssh_packet_get_output(ssh), len); 312 } 313 314 int 315 ssh_output_space(struct ssh *ssh, size_t len) 316 { 317 return (0 == sshbuf_check_reserve(ssh_packet_get_output(ssh), len)); 318 } 319 320 int 321 ssh_input_space(struct ssh *ssh, size_t len) 322 { 323 return (0 == sshbuf_check_reserve(ssh_packet_get_input(ssh), len)); 324 } 325 326 /* Read other side's version identification. */ 327 int 328 _ssh_read_banner(struct ssh *ssh, struct sshbuf *banner) 329 { 330 struct sshbuf *input = ssh_packet_get_input(ssh); 331 const char *mismatch = "Protocol mismatch.\r\n"; 332 const u_char *s = sshbuf_ptr(input); 333 u_char c; 334 char *cp = NULL, *remote_version = NULL; 335 int r = 0, remote_major, remote_minor, expect_nl; 336 size_t n, j; 337 338 for (j = n = 0;;) { 339 sshbuf_reset(banner); 340 expect_nl = 0; 341 for (;;) { 342 if (j >= sshbuf_len(input)) 343 return 0; /* insufficient data in input buf */ 344 c = s[j++]; 345 if (c == '\r') { 346 expect_nl = 1; 347 continue; 348 } 349 if (c == '\n') 350 break; 351 if (expect_nl) 352 goto bad; 353 if ((r = sshbuf_put_u8(banner, c)) != 0) 354 return r; 355 if (sshbuf_len(banner) > SSH_MAX_BANNER_LEN) 356 goto bad; 357 } 358 if (sshbuf_len(banner) >= 4 && 359 memcmp(sshbuf_ptr(banner), "SSH-", 4) == 0) 360 break; 361 debug("%s: %.*s", __func__, (int)sshbuf_len(banner), 362 sshbuf_ptr(banner)); 363 /* Accept lines before banner only on client */ 364 if (ssh->kex->server || ++n > SSH_MAX_PRE_BANNER_LINES) { 365 bad: 366 if ((r = sshbuf_put(ssh_packet_get_output(ssh), 367 mismatch, strlen(mismatch))) != 0) 368 return r; 369 return SSH_ERR_NO_PROTOCOL_VERSION; 370 } 371 } 372 if ((r = sshbuf_consume(input, j)) != 0) 373 return r; 374 375 /* XXX remote version must be the same size as banner for sscanf */ 376 if ((cp = sshbuf_dup_string(banner)) == NULL || 377 (remote_version = calloc(1, sshbuf_len(banner))) == NULL) { 378 r = SSH_ERR_ALLOC_FAIL; 379 goto out; 380 } 381 382 /* 383 * Check that the versions match. In future this might accept 384 * several versions and set appropriate flags to handle them. 385 */ 386 if (sscanf(cp, "SSH-%d.%d-%[^\n]\n", 387 &remote_major, &remote_minor, remote_version) != 3) { 388 r = SSH_ERR_INVALID_FORMAT; 389 goto out; 390 } 391 debug("Remote protocol version %d.%d, remote software version %.100s", 392 remote_major, remote_minor, remote_version); 393 394 ssh->compat = compat_datafellows(remote_version); 395 if (remote_major == 1 && remote_minor == 99) { 396 remote_major = 2; 397 remote_minor = 0; 398 } 399 if (remote_major != 2) 400 r = SSH_ERR_PROTOCOL_MISMATCH; 401 402 debug("Remote version string %.100s", cp); 403 out: 404 free(cp); 405 free(remote_version); 406 return r; 407 } 408 409 /* Send our own protocol version identification. */ 410 int 411 _ssh_send_banner(struct ssh *ssh, struct sshbuf *banner) 412 { 413 char *cp; 414 int r; 415 416 if ((r = sshbuf_putf(banner, "SSH-2.0-%.100s\r\n", SSH_VERSION)) != 0) 417 return r; 418 if ((r = sshbuf_putb(ssh_packet_get_output(ssh), banner)) != 0) 419 return r; 420 /* Remove trailing \r\n */ 421 if ((r = sshbuf_consume_end(banner, 2)) != 0) 422 return r; 423 if ((cp = sshbuf_dup_string(banner)) == NULL) 424 return SSH_ERR_ALLOC_FAIL; 425 debug("Local version string %.100s", cp); 426 free(cp); 427 return 0; 428 } 429 430 int 431 _ssh_exchange_banner(struct ssh *ssh) 432 { 433 struct kex *kex = ssh->kex; 434 int r; 435 436 /* 437 * if _ssh_read_banner() cannot parse a full version string 438 * it will return NULL and we end up calling it again. 439 */ 440 441 r = 0; 442 if (kex->server) { 443 if (sshbuf_len(ssh->kex->server_version) == 0) 444 r = _ssh_send_banner(ssh, ssh->kex->server_version); 445 if (r == 0 && 446 sshbuf_len(ssh->kex->server_version) != 0 && 447 sshbuf_len(ssh->kex->client_version) == 0) 448 r = _ssh_read_banner(ssh, ssh->kex->client_version); 449 } else { 450 if (sshbuf_len(ssh->kex->server_version) == 0) 451 r = _ssh_read_banner(ssh, ssh->kex->server_version); 452 if (r == 0 && 453 sshbuf_len(ssh->kex->server_version) != 0 && 454 sshbuf_len(ssh->kex->client_version) == 0) 455 r = _ssh_send_banner(ssh, ssh->kex->client_version); 456 } 457 if (r != 0) 458 return r; 459 /* start initial kex as soon as we have exchanged the banners */ 460 if (sshbuf_len(ssh->kex->server_version) != 0 && 461 sshbuf_len(ssh->kex->client_version) != 0) { 462 if ((r = _ssh_order_hostkeyalgs(ssh)) != 0 || 463 (r = kex_send_kexinit(ssh)) != 0) 464 return r; 465 } 466 return 0; 467 } 468 469 struct sshkey * 470 _ssh_host_public_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->public_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 struct sshkey * 485 _ssh_host_private_key(int type, int nid, struct ssh *ssh) 486 { 487 struct key_entry *k; 488 489 debug3("%s: need %d", __func__, type); 490 TAILQ_FOREACH(k, &ssh->private_keys, next) { 491 debug3("%s: check %s", __func__, sshkey_type(k->key)); 492 if (k->key->type == type && 493 (type != KEY_ECDSA || k->key->ecdsa_nid == nid)) 494 return (k->key); 495 } 496 return (NULL); 497 } 498 499 int 500 _ssh_verify_host_key(struct sshkey *hostkey, struct ssh *ssh) 501 { 502 struct key_entry *k; 503 504 debug3("%s: need %s", __func__, sshkey_type(hostkey)); 505 TAILQ_FOREACH(k, &ssh->public_keys, next) { 506 debug3("%s: check %s", __func__, sshkey_type(k->key)); 507 if (sshkey_equal_public(hostkey, k->key)) 508 return (0); /* ok */ 509 } 510 return (-1); /* failed */ 511 } 512 513 /* offer hostkey algorithms in kexinit depending on registered keys */ 514 int 515 _ssh_order_hostkeyalgs(struct ssh *ssh) 516 { 517 struct key_entry *k; 518 char *orig, *avail, *oavail = NULL, *alg, *replace = NULL; 519 char **proposal; 520 size_t maxlen; 521 int ktype, r; 522 523 /* XXX we de-serialize ssh->kex->my, modify it, and change it */ 524 if ((r = kex_buf2prop(ssh->kex->my, NULL, &proposal)) != 0) 525 return r; 526 orig = proposal[PROPOSAL_SERVER_HOST_KEY_ALGS]; 527 if ((oavail = avail = strdup(orig)) == NULL) { 528 r = SSH_ERR_ALLOC_FAIL; 529 goto out; 530 } 531 maxlen = strlen(avail) + 1; 532 if ((replace = calloc(1, maxlen)) == NULL) { 533 r = SSH_ERR_ALLOC_FAIL; 534 goto out; 535 } 536 *replace = '\0'; 537 while ((alg = strsep(&avail, ",")) && *alg != '\0') { 538 if ((ktype = sshkey_type_from_name(alg)) == KEY_UNSPEC) 539 continue; 540 TAILQ_FOREACH(k, &ssh->public_keys, next) { 541 if (k->key->type == ktype || 542 (sshkey_is_cert(k->key) && k->key->type == 543 sshkey_type_plain(ktype))) { 544 if (*replace != '\0') 545 strlcat(replace, ",", maxlen); 546 strlcat(replace, alg, maxlen); 547 break; 548 } 549 } 550 } 551 if (*replace != '\0') { 552 debug2("%s: orig/%d %s", __func__, ssh->kex->server, orig); 553 debug2("%s: replace/%d %s", __func__, ssh->kex->server, replace); 554 free(orig); 555 proposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = replace; 556 replace = NULL; /* owned by proposal */ 557 r = kex_prop2buf(ssh->kex->my, proposal); 558 } 559 out: 560 free(oavail); 561 free(replace); 562 kex_prop_free(proposal); 563 return r; 564 } 565 566 int 567 _ssh_host_key_sign(struct ssh *ssh, struct sshkey *privkey, 568 struct sshkey *pubkey, u_char **signature, size_t *slen, 569 const u_char *data, size_t dlen, const char *alg) 570 { 571 return sshkey_sign(privkey, signature, slen, data, dlen, 572 alg, NULL, ssh->compat); 573 } 574