1 /* $OpenBSD: ssh_api.c,v 1.22 2020/10/18 11:32:02 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 <sys/types.h> 19 20 #include <stdio.h> 21 #include <stdlib.h> 22 23 #include "ssh_api.h" 24 #include "compat.h" 25 #include "log.h" 26 #include "authfile.h" 27 #include "sshkey.h" 28 #include "misc.h" 29 #include "ssh2.h" 30 #include "version.h" 31 #include "myproposal.h" 32 #include "ssherr.h" 33 #include "sshbuf.h" 34 35 #include <string.h> 36 37 int _ssh_exchange_banner(struct ssh *); 38 int _ssh_send_banner(struct ssh *, struct sshbuf *); 39 int _ssh_read_banner(struct ssh *, struct sshbuf *); 40 int _ssh_order_hostkeyalgs(struct ssh *); 41 int _ssh_verify_host_key(struct sshkey *, struct ssh *); 42 struct sshkey *_ssh_host_public_key(int, int, struct ssh *); 43 struct sshkey *_ssh_host_private_key(int, int, struct ssh *); 44 int _ssh_host_key_sign(struct ssh *, struct sshkey *, struct sshkey *, 45 u_char **, size_t *, const u_char *, size_t, const char *); 46 47 /* 48 * stubs for the server side implementation of kex. 49 * disable privsep so our stubs will never be called. 50 */ 51 int use_privsep = 0; 52 int mm_sshkey_sign(struct sshkey *, u_char **, u_int *, 53 const u_char *, u_int, const char *, const char *, const char *, u_int); 54 55 #ifdef WITH_OPENSSL 56 DH *mm_choose_dh(int, int, int); 57 #endif 58 59 /* Define these two variables here so that they are part of the library */ 60 u_char *session_id2 = NULL; 61 u_int session_id2_len = 0; 62 63 int 64 mm_sshkey_sign(struct sshkey *key, u_char **sigp, u_int *lenp, 65 const u_char *data, u_int datalen, const char *alg, 66 const char *sk_provider, const char *sk_pin, u_int compat) 67 { 68 return (-1); 69 } 70 71 #ifdef WITH_OPENSSL 72 DH * 73 mm_choose_dh(int min, int nbits, int max) 74 { 75 return (NULL); 76 } 77 #endif 78 79 /* API */ 80 81 int 82 ssh_init(struct ssh **sshp, int is_server, struct kex_params *kex_params) 83 { 84 char *myproposal[PROPOSAL_MAX] = { KEX_CLIENT }; 85 struct ssh *ssh; 86 char **proposal; 87 static int called; 88 int r; 89 90 if (!called) { 91 #ifdef WITH_OPENSSL 92 OpenSSL_add_all_algorithms(); 93 #endif 94 called = 1; 95 } 96 97 if ((ssh = ssh_packet_set_connection(NULL, -1, -1)) == NULL) 98 return SSH_ERR_ALLOC_FAIL; 99 if (is_server) 100 ssh_packet_set_server(ssh); 101 102 /* Initialize key exchange */ 103 proposal = kex_params ? kex_params->proposal : myproposal; 104 if ((r = kex_ready(ssh, proposal)) != 0) { 105 ssh_free(ssh); 106 return r; 107 } 108 ssh->kex->server = is_server; 109 if (is_server) { 110 #ifdef WITH_OPENSSL 111 ssh->kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_server; 112 ssh->kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_server; 113 ssh->kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_server; 114 ssh->kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_server; 115 ssh->kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_server; 116 ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_server; 117 ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_server; 118 ssh->kex->kex[KEX_ECDH_SHA2] = kex_gen_server; 119 #endif /* WITH_OPENSSL */ 120 ssh->kex->kex[KEX_C25519_SHA256] = kex_gen_server; 121 ssh->kex->kex[KEX_KEM_SNTRUP4591761X25519_SHA512] = kex_gen_server; 122 ssh->kex->load_host_public_key=&_ssh_host_public_key; 123 ssh->kex->load_host_private_key=&_ssh_host_private_key; 124 ssh->kex->sign=&_ssh_host_key_sign; 125 } else { 126 #ifdef WITH_OPENSSL 127 ssh->kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_client; 128 ssh->kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_client; 129 ssh->kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_client; 130 ssh->kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_client; 131 ssh->kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_client; 132 ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_client; 133 ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_client; 134 ssh->kex->kex[KEX_ECDH_SHA2] = kex_gen_client; 135 #endif /* WITH_OPENSSL */ 136 ssh->kex->kex[KEX_C25519_SHA256] = kex_gen_client; 137 ssh->kex->kex[KEX_KEM_SNTRUP4591761X25519_SHA512] = kex_gen_client; 138 ssh->kex->verify_host_key =&_ssh_verify_host_key; 139 } 140 *sshp = ssh; 141 return 0; 142 } 143 144 void 145 ssh_free(struct ssh *ssh) 146 { 147 struct key_entry *k; 148 149 /* 150 * we've only created the public keys variants in case we 151 * are a acting as a server. 152 */ 153 while ((k = TAILQ_FIRST(&ssh->public_keys)) != NULL) { 154 TAILQ_REMOVE(&ssh->public_keys, k, next); 155 if (ssh->kex && ssh->kex->server) 156 sshkey_free(k->key); 157 free(k); 158 } 159 while ((k = TAILQ_FIRST(&ssh->private_keys)) != NULL) { 160 TAILQ_REMOVE(&ssh->private_keys, k, next); 161 free(k); 162 } 163 ssh_packet_close(ssh); 164 free(ssh); 165 } 166 167 void 168 ssh_set_app_data(struct ssh *ssh, void *app_data) 169 { 170 ssh->app_data = app_data; 171 } 172 173 void * 174 ssh_get_app_data(struct ssh *ssh) 175 { 176 return ssh->app_data; 177 } 178 179 /* Returns < 0 on error, 0 otherwise */ 180 int 181 ssh_add_hostkey(struct ssh *ssh, struct sshkey *key) 182 { 183 struct sshkey *pubkey = NULL; 184 struct key_entry *k = NULL, *k_prv = NULL; 185 int r; 186 187 if (ssh->kex->server) { 188 if ((r = sshkey_from_private(key, &pubkey)) != 0) 189 return r; 190 if ((k = malloc(sizeof(*k))) == NULL || 191 (k_prv = malloc(sizeof(*k_prv))) == NULL) { 192 free(k); 193 sshkey_free(pubkey); 194 return SSH_ERR_ALLOC_FAIL; 195 } 196 k_prv->key = key; 197 TAILQ_INSERT_TAIL(&ssh->private_keys, k_prv, next); 198 199 /* add the public key, too */ 200 k->key = pubkey; 201 TAILQ_INSERT_TAIL(&ssh->public_keys, k, next); 202 r = 0; 203 } else { 204 if ((k = malloc(sizeof(*k))) == NULL) 205 return SSH_ERR_ALLOC_FAIL; 206 k->key = key; 207 TAILQ_INSERT_TAIL(&ssh->public_keys, k, next); 208 r = 0; 209 } 210 211 return r; 212 } 213 214 int 215 ssh_set_verify_host_key_callback(struct ssh *ssh, 216 int (*cb)(struct sshkey *, struct ssh *)) 217 { 218 if (cb == NULL || ssh->kex == NULL) 219 return SSH_ERR_INVALID_ARGUMENT; 220 221 ssh->kex->verify_host_key = cb; 222 223 return 0; 224 } 225 226 int 227 ssh_input_append(struct ssh *ssh, const u_char *data, size_t len) 228 { 229 return sshbuf_put(ssh_packet_get_input(ssh), data, len); 230 } 231 232 int 233 ssh_packet_next(struct ssh *ssh, u_char *typep) 234 { 235 int r; 236 u_int32_t seqnr; 237 u_char type; 238 239 /* 240 * Try to read a packet. Return SSH_MSG_NONE if no packet or not 241 * enough data. 242 */ 243 *typep = SSH_MSG_NONE; 244 if (sshbuf_len(ssh->kex->client_version) == 0 || 245 sshbuf_len(ssh->kex->server_version) == 0) 246 return _ssh_exchange_banner(ssh); 247 /* 248 * If we enough data and a dispatch function then 249 * call the function and get the next packet. 250 * Otherwise return the packet type to the caller so it 251 * can decide how to go on. 252 * 253 * We will only call the dispatch function for: 254 * 20-29 Algorithm negotiation 255 * 30-49 Key exchange method specific (numbers can be reused for 256 * different authentication methods) 257 */ 258 for (;;) { 259 if ((r = ssh_packet_read_poll2(ssh, &type, &seqnr)) != 0) 260 return r; 261 if (type > 0 && type < DISPATCH_MAX && 262 type >= SSH2_MSG_KEXINIT && type <= SSH2_MSG_TRANSPORT_MAX && 263 ssh->dispatch[type] != NULL) { 264 if ((r = (*ssh->dispatch[type])(type, seqnr, ssh)) != 0) 265 return r; 266 } else { 267 *typep = type; 268 return 0; 269 } 270 } 271 } 272 273 const u_char * 274 ssh_packet_payload(struct ssh *ssh, size_t *lenp) 275 { 276 return sshpkt_ptr(ssh, lenp); 277 } 278 279 int 280 ssh_packet_put(struct ssh *ssh, int type, const u_char *data, size_t len) 281 { 282 int r; 283 284 if ((r = sshpkt_start(ssh, type)) != 0 || 285 (r = sshpkt_put(ssh, data, len)) != 0 || 286 (r = sshpkt_send(ssh)) != 0) 287 return r; 288 return 0; 289 } 290 291 const u_char * 292 ssh_output_ptr(struct ssh *ssh, size_t *len) 293 { 294 struct sshbuf *output = ssh_packet_get_output(ssh); 295 296 *len = sshbuf_len(output); 297 return sshbuf_ptr(output); 298 } 299 300 int 301 ssh_output_consume(struct ssh *ssh, size_t len) 302 { 303 return sshbuf_consume(ssh_packet_get_output(ssh), len); 304 } 305 306 int 307 ssh_output_space(struct ssh *ssh, size_t len) 308 { 309 return (0 == sshbuf_check_reserve(ssh_packet_get_output(ssh), len)); 310 } 311 312 int 313 ssh_input_space(struct ssh *ssh, size_t len) 314 { 315 return (0 == sshbuf_check_reserve(ssh_packet_get_input(ssh), len)); 316 } 317 318 /* Read other side's version identification. */ 319 int 320 _ssh_read_banner(struct ssh *ssh, struct sshbuf *banner) 321 { 322 struct sshbuf *input = ssh_packet_get_input(ssh); 323 const char *mismatch = "Protocol mismatch.\r\n"; 324 const u_char *s = sshbuf_ptr(input); 325 u_char c; 326 char *cp = NULL, *remote_version = NULL; 327 int r = 0, remote_major, remote_minor, expect_nl; 328 size_t n, j; 329 330 for (j = n = 0;;) { 331 sshbuf_reset(banner); 332 expect_nl = 0; 333 for (;;) { 334 if (j >= sshbuf_len(input)) 335 return 0; /* insufficient data in input buf */ 336 c = s[j++]; 337 if (c == '\r') { 338 expect_nl = 1; 339 continue; 340 } 341 if (c == '\n') 342 break; 343 if (expect_nl) 344 goto bad; 345 if ((r = sshbuf_put_u8(banner, c)) != 0) 346 return r; 347 if (sshbuf_len(banner) > SSH_MAX_BANNER_LEN) 348 goto bad; 349 } 350 if (sshbuf_len(banner) >= 4 && 351 memcmp(sshbuf_ptr(banner), "SSH-", 4) == 0) 352 break; 353 debug_f("%.*s", (int)sshbuf_len(banner), 354 sshbuf_ptr(banner)); 355 /* Accept lines before banner only on client */ 356 if (ssh->kex->server || ++n > SSH_MAX_PRE_BANNER_LINES) { 357 bad: 358 if ((r = sshbuf_put(ssh_packet_get_output(ssh), 359 mismatch, strlen(mismatch))) != 0) 360 return r; 361 return SSH_ERR_NO_PROTOCOL_VERSION; 362 } 363 } 364 if ((r = sshbuf_consume(input, j)) != 0) 365 return r; 366 367 /* XXX remote version must be the same size as banner for sscanf */ 368 if ((cp = sshbuf_dup_string(banner)) == NULL || 369 (remote_version = calloc(1, sshbuf_len(banner))) == NULL) { 370 r = SSH_ERR_ALLOC_FAIL; 371 goto out; 372 } 373 374 /* 375 * Check that the versions match. In future this might accept 376 * several versions and set appropriate flags to handle them. 377 */ 378 if (sscanf(cp, "SSH-%d.%d-%[^\n]\n", 379 &remote_major, &remote_minor, remote_version) != 3) { 380 r = SSH_ERR_INVALID_FORMAT; 381 goto out; 382 } 383 debug("Remote protocol version %d.%d, remote software version %.100s", 384 remote_major, remote_minor, remote_version); 385 386 ssh->compat = compat_datafellows(remote_version); 387 if (remote_major == 1 && remote_minor == 99) { 388 remote_major = 2; 389 remote_minor = 0; 390 } 391 if (remote_major != 2) 392 r = SSH_ERR_PROTOCOL_MISMATCH; 393 394 debug("Remote version string %.100s", cp); 395 out: 396 free(cp); 397 free(remote_version); 398 return r; 399 } 400 401 /* Send our own protocol version identification. */ 402 int 403 _ssh_send_banner(struct ssh *ssh, struct sshbuf *banner) 404 { 405 char *cp; 406 int r; 407 408 if ((r = sshbuf_putf(banner, "SSH-2.0-%.100s\r\n", SSH_VERSION)) != 0) 409 return r; 410 if ((r = sshbuf_putb(ssh_packet_get_output(ssh), banner)) != 0) 411 return r; 412 /* Remove trailing \r\n */ 413 if ((r = sshbuf_consume_end(banner, 2)) != 0) 414 return r; 415 if ((cp = sshbuf_dup_string(banner)) == NULL) 416 return SSH_ERR_ALLOC_FAIL; 417 debug("Local version string %.100s", cp); 418 free(cp); 419 return 0; 420 } 421 422 int 423 _ssh_exchange_banner(struct ssh *ssh) 424 { 425 struct kex *kex = ssh->kex; 426 int r; 427 428 /* 429 * if _ssh_read_banner() cannot parse a full version string 430 * it will return NULL and we end up calling it again. 431 */ 432 433 r = 0; 434 if (kex->server) { 435 if (sshbuf_len(ssh->kex->server_version) == 0) 436 r = _ssh_send_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_read_banner(ssh, ssh->kex->client_version); 441 } else { 442 if (sshbuf_len(ssh->kex->server_version) == 0) 443 r = _ssh_read_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_send_banner(ssh, ssh->kex->client_version); 448 } 449 if (r != 0) 450 return r; 451 /* start initial kex as soon as we have exchanged the banners */ 452 if (sshbuf_len(ssh->kex->server_version) != 0 && 453 sshbuf_len(ssh->kex->client_version) != 0) { 454 if ((r = _ssh_order_hostkeyalgs(ssh)) != 0 || 455 (r = kex_send_kexinit(ssh)) != 0) 456 return r; 457 } 458 return 0; 459 } 460 461 struct sshkey * 462 _ssh_host_public_key(int type, int nid, struct ssh *ssh) 463 { 464 struct key_entry *k; 465 466 debug3_f("need %d", type); 467 TAILQ_FOREACH(k, &ssh->public_keys, next) { 468 debug3_f("check %s", 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 struct sshkey * 477 _ssh_host_private_key(int type, int nid, struct ssh *ssh) 478 { 479 struct key_entry *k; 480 481 debug3_f("need %d", type); 482 TAILQ_FOREACH(k, &ssh->private_keys, next) { 483 debug3_f("check %s", sshkey_type(k->key)); 484 if (k->key->type == type && 485 (type != KEY_ECDSA || k->key->ecdsa_nid == nid)) 486 return (k->key); 487 } 488 return (NULL); 489 } 490 491 int 492 _ssh_verify_host_key(struct sshkey *hostkey, struct ssh *ssh) 493 { 494 struct key_entry *k; 495 496 debug3_f("need %s", sshkey_type(hostkey)); 497 TAILQ_FOREACH(k, &ssh->public_keys, next) { 498 debug3_f("check %s", sshkey_type(k->key)); 499 if (sshkey_equal_public(hostkey, k->key)) 500 return (0); /* ok */ 501 } 502 return (-1); /* failed */ 503 } 504 505 /* offer hostkey algorithms in kexinit depending on registered keys */ 506 int 507 _ssh_order_hostkeyalgs(struct ssh *ssh) 508 { 509 struct key_entry *k; 510 char *orig, *avail, *oavail = NULL, *alg, *replace = NULL; 511 char **proposal; 512 size_t maxlen; 513 int ktype, r; 514 515 /* XXX we de-serialize ssh->kex->my, modify it, and change it */ 516 if ((r = kex_buf2prop(ssh->kex->my, NULL, &proposal)) != 0) 517 return r; 518 orig = proposal[PROPOSAL_SERVER_HOST_KEY_ALGS]; 519 if ((oavail = avail = strdup(orig)) == NULL) { 520 r = SSH_ERR_ALLOC_FAIL; 521 goto out; 522 } 523 maxlen = strlen(avail) + 1; 524 if ((replace = calloc(1, maxlen)) == NULL) { 525 r = SSH_ERR_ALLOC_FAIL; 526 goto out; 527 } 528 *replace = '\0'; 529 while ((alg = strsep(&avail, ",")) && *alg != '\0') { 530 if ((ktype = sshkey_type_from_name(alg)) == KEY_UNSPEC) 531 continue; 532 TAILQ_FOREACH(k, &ssh->public_keys, next) { 533 if (k->key->type == ktype || 534 (sshkey_is_cert(k->key) && k->key->type == 535 sshkey_type_plain(ktype))) { 536 if (*replace != '\0') 537 strlcat(replace, ",", maxlen); 538 strlcat(replace, alg, maxlen); 539 break; 540 } 541 } 542 } 543 if (*replace != '\0') { 544 debug2_f("orig/%d %s", ssh->kex->server, orig); 545 debug2_f("replace/%d %s", ssh->kex->server, replace); 546 free(orig); 547 proposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = replace; 548 replace = NULL; /* owned by proposal */ 549 r = kex_prop2buf(ssh->kex->my, proposal); 550 } 551 out: 552 free(oavail); 553 free(replace); 554 kex_prop_free(proposal); 555 return r; 556 } 557 558 int 559 _ssh_host_key_sign(struct ssh *ssh, struct sshkey *privkey, 560 struct sshkey *pubkey, u_char **signature, size_t *slen, 561 const u_char *data, size_t dlen, const char *alg) 562 { 563 return sshkey_sign(privkey, signature, slen, data, dlen, 564 alg, NULL, NULL, ssh->compat); 565 } 566