1 /* $OpenBSD: ssh_api.c,v 1.9 2018/12/27 03:25:25 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 sshkey *, struct sshkey *, 44 u_char **, size_t *, const u_char *, size_t, const char *, u_int); 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] = kexdh_server; 103 ssh->kex->kex[KEX_DH_GRP14_SHA1] = kexdh_server; 104 ssh->kex->kex[KEX_DH_GRP14_SHA256] = kexdh_server; 105 ssh->kex->kex[KEX_DH_GRP16_SHA512] = kexdh_server; 106 ssh->kex->kex[KEX_DH_GRP18_SHA512] = kexdh_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] = kexecdh_server; 111 # endif 112 #endif /* WITH_OPENSSL */ 113 ssh->kex->kex[KEX_C25519_SHA256] = kexc25519_server; 114 ssh->kex->load_host_public_key=&_ssh_host_public_key; 115 ssh->kex->load_host_private_key=&_ssh_host_private_key; 116 ssh->kex->sign=&_ssh_host_key_sign; 117 } else { 118 #ifdef WITH_OPENSSL 119 ssh->kex->kex[KEX_DH_GRP1_SHA1] = kexdh_client; 120 ssh->kex->kex[KEX_DH_GRP14_SHA1] = kexdh_client; 121 ssh->kex->kex[KEX_DH_GRP14_SHA256] = kexdh_client; 122 ssh->kex->kex[KEX_DH_GRP16_SHA512] = kexdh_client; 123 ssh->kex->kex[KEX_DH_GRP18_SHA512] = kexdh_client; 124 ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_client; 125 ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_client; 126 # ifdef OPENSSL_HAS_ECC 127 ssh->kex->kex[KEX_ECDH_SHA2] = kexecdh_client; 128 # endif 129 #endif /* WITH_OPENSSL */ 130 ssh->kex->kex[KEX_C25519_SHA256] = kexc25519_client; 131 ssh->kex->verify_host_key =&_ssh_verify_host_key; 132 } 133 *sshp = ssh; 134 return 0; 135 } 136 137 void 138 ssh_free(struct ssh *ssh) 139 { 140 struct key_entry *k; 141 142 ssh_packet_close(ssh); 143 /* 144 * we've only created the public keys variants in case we 145 * are a acting as a server. 146 */ 147 while ((k = TAILQ_FIRST(&ssh->public_keys)) != NULL) { 148 TAILQ_REMOVE(&ssh->public_keys, k, next); 149 if (ssh->kex && ssh->kex->server) 150 sshkey_free(k->key); 151 free(k); 152 } 153 while ((k = TAILQ_FIRST(&ssh->private_keys)) != NULL) { 154 TAILQ_REMOVE(&ssh->private_keys, k, next); 155 free(k); 156 } 157 if (ssh->kex) 158 kex_free(ssh->kex); 159 free(ssh); 160 } 161 162 void 163 ssh_set_app_data(struct ssh *ssh, void *app_data) 164 { 165 ssh->app_data = app_data; 166 } 167 168 void * 169 ssh_get_app_data(struct ssh *ssh) 170 { 171 return ssh->app_data; 172 } 173 174 /* Returns < 0 on error, 0 otherwise */ 175 int 176 ssh_add_hostkey(struct ssh *ssh, struct sshkey *key) 177 { 178 struct sshkey *pubkey = NULL; 179 struct key_entry *k = NULL, *k_prv = NULL; 180 int r; 181 182 if (ssh->kex->server) { 183 if ((r = sshkey_from_private(key, &pubkey)) != 0) 184 return r; 185 if ((k = malloc(sizeof(*k))) == NULL || 186 (k_prv = malloc(sizeof(*k_prv))) == NULL) { 187 free(k); 188 sshkey_free(pubkey); 189 return SSH_ERR_ALLOC_FAIL; 190 } 191 k_prv->key = key; 192 TAILQ_INSERT_TAIL(&ssh->private_keys, k_prv, next); 193 194 /* add the public key, too */ 195 k->key = pubkey; 196 TAILQ_INSERT_TAIL(&ssh->public_keys, k, next); 197 r = 0; 198 } else { 199 if ((k = malloc(sizeof(*k))) == NULL) 200 return SSH_ERR_ALLOC_FAIL; 201 k->key = key; 202 TAILQ_INSERT_TAIL(&ssh->public_keys, k, next); 203 r = 0; 204 } 205 206 return r; 207 } 208 209 int 210 ssh_set_verify_host_key_callback(struct ssh *ssh, 211 int (*cb)(struct sshkey *, struct ssh *)) 212 { 213 if (cb == NULL || ssh->kex == NULL) 214 return SSH_ERR_INVALID_ARGUMENT; 215 216 ssh->kex->verify_host_key = cb; 217 218 return 0; 219 } 220 221 int 222 ssh_input_append(struct ssh *ssh, const u_char *data, size_t len) 223 { 224 return sshbuf_put(ssh_packet_get_input(ssh), data, len); 225 } 226 227 int 228 ssh_packet_next(struct ssh *ssh, u_char *typep) 229 { 230 int r; 231 u_int32_t seqnr; 232 u_char type; 233 234 /* 235 * Try to read a packet. Return SSH_MSG_NONE if no packet or not 236 * enough data. 237 */ 238 *typep = SSH_MSG_NONE; 239 if (sshbuf_len(ssh->kex->client_version) == 0 || 240 sshbuf_len(ssh->kex->server_version) == 0) 241 return _ssh_exchange_banner(ssh); 242 /* 243 * If we enough data and a dispatch function then 244 * call the function and get the next packet. 245 * Otherwise return the packet type to the caller so it 246 * can decide how to go on. 247 * 248 * We will only call the dispatch function for: 249 * 20-29 Algorithm negotiation 250 * 30-49 Key exchange method specific (numbers can be reused for 251 * different authentication methods) 252 */ 253 for (;;) { 254 if ((r = ssh_packet_read_poll2(ssh, &type, &seqnr)) != 0) 255 return r; 256 if (type > 0 && type < DISPATCH_MAX && 257 type >= SSH2_MSG_KEXINIT && type <= SSH2_MSG_TRANSPORT_MAX && 258 ssh->dispatch[type] != NULL) { 259 if ((r = (*ssh->dispatch[type])(type, seqnr, ssh)) != 0) 260 return r; 261 } else { 262 *typep = type; 263 return 0; 264 } 265 } 266 } 267 268 const u_char * 269 ssh_packet_payload(struct ssh *ssh, size_t *lenp) 270 { 271 return sshpkt_ptr(ssh, lenp); 272 } 273 274 int 275 ssh_packet_put(struct ssh *ssh, int type, const u_char *data, size_t len) 276 { 277 int r; 278 279 if ((r = sshpkt_start(ssh, type)) != 0 || 280 (r = sshpkt_put(ssh, data, len)) != 0 || 281 (r = sshpkt_send(ssh)) != 0) 282 return r; 283 return 0; 284 } 285 286 const u_char * 287 ssh_output_ptr(struct ssh *ssh, size_t *len) 288 { 289 struct sshbuf *output = ssh_packet_get_output(ssh); 290 291 *len = sshbuf_len(output); 292 return sshbuf_ptr(output); 293 } 294 295 int 296 ssh_output_consume(struct ssh *ssh, size_t len) 297 { 298 return sshbuf_consume(ssh_packet_get_output(ssh), len); 299 } 300 301 int 302 ssh_output_space(struct ssh *ssh, size_t len) 303 { 304 return (0 == sshbuf_check_reserve(ssh_packet_get_output(ssh), len)); 305 } 306 307 int 308 ssh_input_space(struct ssh *ssh, size_t len) 309 { 310 return (0 == sshbuf_check_reserve(ssh_packet_get_input(ssh), len)); 311 } 312 313 /* Read other side's version identification. */ 314 int 315 _ssh_read_banner(struct ssh *ssh, struct sshbuf *banner) 316 { 317 struct sshbuf *input = ssh_packet_get_input(ssh); 318 const char *mismatch = "Protocol mismatch.\r\n"; 319 const u_char *s = sshbuf_ptr(input); 320 u_char c; 321 char *cp, *remote_version; 322 int r, remote_major, remote_minor, expect_nl; 323 size_t n, j; 324 325 for (j = n = 0;;) { 326 sshbuf_reset(banner); 327 expect_nl = 0; 328 for (;;) { 329 if (j >= sshbuf_len(input)) 330 return 0; /* insufficient data in input buf */ 331 c = s[j++]; 332 if (c == '\r') { 333 expect_nl = 1; 334 continue; 335 } 336 if (c == '\n') 337 break; 338 if (expect_nl) 339 goto bad; 340 if ((r = sshbuf_put_u8(banner, c)) != 0) 341 return r; 342 if (sshbuf_len(banner) > SSH_MAX_BANNER_LEN) 343 goto bad; 344 } 345 if (sshbuf_len(banner) >= 4 && 346 memcmp(sshbuf_ptr(banner), "SSH-", 4) == 0) 347 break; 348 if ((cp = sshbuf_dup_string(banner)) == NULL) 349 return SSH_ERR_ALLOC_FAIL; 350 debug("%s: %s", __func__, cp); 351 free(cp); 352 /* Accept lines before banner only on client */ 353 if (ssh->kex->server || ++n > SSH_MAX_PRE_BANNER_LINES) { 354 bad: 355 if ((r = sshbuf_put(ssh_packet_get_output(ssh), 356 mismatch, strlen(mismatch))) != 0) 357 return r; 358 return SSH_ERR_NO_PROTOCOL_VERSION; 359 } 360 } 361 if ((r = sshbuf_consume(input, j)) != 0) 362 return r; 363 364 if ((cp = sshbuf_dup_string(banner)) == NULL) 365 return SSH_ERR_ALLOC_FAIL; 366 /* XXX remote version must be the same size as banner for sscanf */ 367 if ((remote_version = calloc(1, sshbuf_len(banner))) == NULL) 368 return SSH_ERR_ALLOC_FAIL; 369 370 /* 371 * Check that the versions match. In future this might accept 372 * several versions and set appropriate flags to handle them. 373 */ 374 if (sscanf(cp, "SSH-%d.%d-%[^\n]\n", 375 &remote_major, &remote_minor, remote_version) != 3) 376 return SSH_ERR_INVALID_FORMAT; 377 debug("Remote protocol version %d.%d, remote software version %.100s", 378 remote_major, remote_minor, remote_version); 379 380 ssh->compat = compat_datafellows(remote_version); 381 if (remote_major == 1 && remote_minor == 99) { 382 remote_major = 2; 383 remote_minor = 0; 384 } 385 if (remote_major != 2) 386 return SSH_ERR_PROTOCOL_MISMATCH; 387 debug("Remote version string %.100s", cp); 388 free(cp); 389 return 0; 390 } 391 392 /* Send our own protocol version identification. */ 393 int 394 _ssh_send_banner(struct ssh *ssh, struct sshbuf *banner) 395 { 396 char *cp; 397 int r; 398 399 if ((r = sshbuf_putf(banner, "SSH-2.0-%.100s\r\n", SSH_VERSION)) != 0) 400 return r; 401 if ((r = sshbuf_putb(ssh_packet_get_output(ssh), banner)) != 0) 402 return r; 403 /* Remove trailing \r\n */ 404 if ((r = sshbuf_consume_end(banner, 2)) != 0) 405 return r; 406 if ((cp = sshbuf_dup_string(banner)) == NULL) 407 return SSH_ERR_ALLOC_FAIL; 408 debug("Local version string %.100s", cp); 409 free(cp); 410 return 0; 411 } 412 413 int 414 _ssh_exchange_banner(struct ssh *ssh) 415 { 416 struct kex *kex = ssh->kex; 417 int r; 418 419 /* 420 * if _ssh_read_banner() cannot parse a full version string 421 * it will return NULL and we end up calling it again. 422 */ 423 424 r = 0; 425 if (kex->server) { 426 if (sshbuf_len(ssh->kex->server_version) == 0) 427 r = _ssh_send_banner(ssh, ssh->kex->server_version); 428 if (r == 0 && 429 sshbuf_len(ssh->kex->server_version) != 0 && 430 sshbuf_len(ssh->kex->client_version) == 0) 431 r = _ssh_read_banner(ssh, ssh->kex->client_version); 432 } else { 433 if (sshbuf_len(ssh->kex->server_version) == 0) 434 r = _ssh_read_banner(ssh, ssh->kex->server_version); 435 if (r == 0 && 436 sshbuf_len(ssh->kex->server_version) != 0 && 437 sshbuf_len(ssh->kex->client_version) == 0) 438 r = _ssh_send_banner(ssh, ssh->kex->client_version); 439 } 440 if (r != 0) 441 return r; 442 /* start initial kex as soon as we have exchanged the banners */ 443 if (sshbuf_len(ssh->kex->server_version) != 0 && 444 sshbuf_len(ssh->kex->client_version) != 0) { 445 if ((r = _ssh_order_hostkeyalgs(ssh)) != 0 || 446 (r = kex_send_kexinit(ssh)) != 0) 447 return r; 448 } 449 return 0; 450 } 451 452 struct sshkey * 453 _ssh_host_public_key(int type, int nid, struct ssh *ssh) 454 { 455 struct key_entry *k; 456 457 debug3("%s: need %d", __func__, type); 458 TAILQ_FOREACH(k, &ssh->public_keys, next) { 459 debug3("%s: check %s", __func__, sshkey_type(k->key)); 460 if (k->key->type == type && 461 (type != KEY_ECDSA || k->key->ecdsa_nid == nid)) 462 return (k->key); 463 } 464 return (NULL); 465 } 466 467 struct sshkey * 468 _ssh_host_private_key(int type, int nid, struct ssh *ssh) 469 { 470 struct key_entry *k; 471 472 debug3("%s: need %d", __func__, type); 473 TAILQ_FOREACH(k, &ssh->private_keys, next) { 474 debug3("%s: check %s", __func__, sshkey_type(k->key)); 475 if (k->key->type == type && 476 (type != KEY_ECDSA || k->key->ecdsa_nid == nid)) 477 return (k->key); 478 } 479 return (NULL); 480 } 481 482 int 483 _ssh_verify_host_key(struct sshkey *hostkey, struct ssh *ssh) 484 { 485 struct key_entry *k; 486 487 debug3("%s: need %s", __func__, sshkey_type(hostkey)); 488 TAILQ_FOREACH(k, &ssh->public_keys, next) { 489 debug3("%s: check %s", __func__, sshkey_type(k->key)); 490 if (sshkey_equal_public(hostkey, k->key)) 491 return (0); /* ok */ 492 } 493 return (-1); /* failed */ 494 } 495 496 /* offer hostkey algorithms in kexinit depending on registered keys */ 497 int 498 _ssh_order_hostkeyalgs(struct ssh *ssh) 499 { 500 struct key_entry *k; 501 char *orig, *avail, *oavail = NULL, *alg, *replace = NULL; 502 char **proposal; 503 size_t maxlen; 504 int ktype, r; 505 506 /* XXX we de-serialize ssh->kex->my, modify it, and change it */ 507 if ((r = kex_buf2prop(ssh->kex->my, NULL, &proposal)) != 0) 508 return r; 509 orig = proposal[PROPOSAL_SERVER_HOST_KEY_ALGS]; 510 if ((oavail = avail = strdup(orig)) == NULL) { 511 r = SSH_ERR_ALLOC_FAIL; 512 goto out; 513 } 514 maxlen = strlen(avail) + 1; 515 if ((replace = calloc(1, maxlen)) == NULL) { 516 r = SSH_ERR_ALLOC_FAIL; 517 goto out; 518 } 519 *replace = '\0'; 520 while ((alg = strsep(&avail, ",")) && *alg != '\0') { 521 if ((ktype = sshkey_type_from_name(alg)) == KEY_UNSPEC) 522 continue; 523 TAILQ_FOREACH(k, &ssh->public_keys, next) { 524 if (k->key->type == ktype || 525 (sshkey_is_cert(k->key) && k->key->type == 526 sshkey_type_plain(ktype))) { 527 if (*replace != '\0') 528 strlcat(replace, ",", maxlen); 529 strlcat(replace, alg, maxlen); 530 break; 531 } 532 } 533 } 534 if (*replace != '\0') { 535 debug2("%s: orig/%d %s", __func__, ssh->kex->server, orig); 536 debug2("%s: replace/%d %s", __func__, ssh->kex->server, replace); 537 free(orig); 538 proposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = replace; 539 replace = NULL; /* owned by proposal */ 540 r = kex_prop2buf(ssh->kex->my, proposal); 541 } 542 out: 543 free(oavail); 544 free(replace); 545 kex_prop_free(proposal); 546 return r; 547 } 548 549 int 550 _ssh_host_key_sign(struct sshkey *privkey, struct sshkey *pubkey, 551 u_char **signature, size_t *slen, const u_char *data, size_t dlen, 552 const char *alg, u_int compat) 553 { 554 return sshkey_sign(privkey, signature, slen, data, dlen, alg, compat); 555 } 556