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