1 /* $OpenBSD: ssh_api.c,v 1.24 2020/12/29 00:59:15 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_SNTRUP761X25519_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_SNTRUP761X25519_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 if (ssh == NULL) 150 return; 151 152 /* 153 * we've only created the public keys variants in case we 154 * are a acting as a server. 155 */ 156 while ((k = TAILQ_FIRST(&ssh->public_keys)) != NULL) { 157 TAILQ_REMOVE(&ssh->public_keys, k, next); 158 if (ssh->kex && ssh->kex->server) 159 sshkey_free(k->key); 160 free(k); 161 } 162 while ((k = TAILQ_FIRST(&ssh->private_keys)) != NULL) { 163 TAILQ_REMOVE(&ssh->private_keys, k, next); 164 free(k); 165 } 166 ssh_packet_close(ssh); 167 free(ssh); 168 } 169 170 void 171 ssh_set_app_data(struct ssh *ssh, void *app_data) 172 { 173 ssh->app_data = app_data; 174 } 175 176 void * 177 ssh_get_app_data(struct ssh *ssh) 178 { 179 return ssh->app_data; 180 } 181 182 /* Returns < 0 on error, 0 otherwise */ 183 int 184 ssh_add_hostkey(struct ssh *ssh, struct sshkey *key) 185 { 186 struct sshkey *pubkey = NULL; 187 struct key_entry *k = NULL, *k_prv = NULL; 188 int r; 189 190 if (ssh->kex->server) { 191 if ((r = sshkey_from_private(key, &pubkey)) != 0) 192 return r; 193 if ((k = malloc(sizeof(*k))) == NULL || 194 (k_prv = malloc(sizeof(*k_prv))) == NULL) { 195 free(k); 196 sshkey_free(pubkey); 197 return SSH_ERR_ALLOC_FAIL; 198 } 199 k_prv->key = key; 200 TAILQ_INSERT_TAIL(&ssh->private_keys, k_prv, next); 201 202 /* add the public key, too */ 203 k->key = pubkey; 204 TAILQ_INSERT_TAIL(&ssh->public_keys, k, next); 205 r = 0; 206 } else { 207 if ((k = malloc(sizeof(*k))) == NULL) 208 return SSH_ERR_ALLOC_FAIL; 209 k->key = key; 210 TAILQ_INSERT_TAIL(&ssh->public_keys, k, next); 211 r = 0; 212 } 213 214 return r; 215 } 216 217 int 218 ssh_set_verify_host_key_callback(struct ssh *ssh, 219 int (*cb)(struct sshkey *, struct ssh *)) 220 { 221 if (cb == NULL || ssh->kex == NULL) 222 return SSH_ERR_INVALID_ARGUMENT; 223 224 ssh->kex->verify_host_key = cb; 225 226 return 0; 227 } 228 229 int 230 ssh_input_append(struct ssh *ssh, const u_char *data, size_t len) 231 { 232 return sshbuf_put(ssh_packet_get_input(ssh), data, len); 233 } 234 235 int 236 ssh_packet_next(struct ssh *ssh, u_char *typep) 237 { 238 int r; 239 u_int32_t seqnr; 240 u_char type; 241 242 /* 243 * Try to read a packet. Return SSH_MSG_NONE if no packet or not 244 * enough data. 245 */ 246 *typep = SSH_MSG_NONE; 247 if (sshbuf_len(ssh->kex->client_version) == 0 || 248 sshbuf_len(ssh->kex->server_version) == 0) 249 return _ssh_exchange_banner(ssh); 250 /* 251 * If we enough data and a dispatch function then 252 * call the function and get the next packet. 253 * Otherwise return the packet type to the caller so it 254 * can decide how to go on. 255 * 256 * We will only call the dispatch function for: 257 * 20-29 Algorithm negotiation 258 * 30-49 Key exchange method specific (numbers can be reused for 259 * different authentication methods) 260 */ 261 for (;;) { 262 if ((r = ssh_packet_read_poll2(ssh, &type, &seqnr)) != 0) 263 return r; 264 if (type > 0 && type < DISPATCH_MAX && 265 type >= SSH2_MSG_KEXINIT && type <= SSH2_MSG_TRANSPORT_MAX && 266 ssh->dispatch[type] != NULL) { 267 if ((r = (*ssh->dispatch[type])(type, seqnr, ssh)) != 0) 268 return r; 269 } else { 270 *typep = type; 271 return 0; 272 } 273 } 274 } 275 276 const u_char * 277 ssh_packet_payload(struct ssh *ssh, size_t *lenp) 278 { 279 return sshpkt_ptr(ssh, lenp); 280 } 281 282 int 283 ssh_packet_put(struct ssh *ssh, int type, const u_char *data, size_t len) 284 { 285 int r; 286 287 if ((r = sshpkt_start(ssh, type)) != 0 || 288 (r = sshpkt_put(ssh, data, len)) != 0 || 289 (r = sshpkt_send(ssh)) != 0) 290 return r; 291 return 0; 292 } 293 294 const u_char * 295 ssh_output_ptr(struct ssh *ssh, size_t *len) 296 { 297 struct sshbuf *output = ssh_packet_get_output(ssh); 298 299 *len = sshbuf_len(output); 300 return sshbuf_ptr(output); 301 } 302 303 int 304 ssh_output_consume(struct ssh *ssh, size_t len) 305 { 306 return sshbuf_consume(ssh_packet_get_output(ssh), len); 307 } 308 309 int 310 ssh_output_space(struct ssh *ssh, size_t len) 311 { 312 return (0 == sshbuf_check_reserve(ssh_packet_get_output(ssh), len)); 313 } 314 315 int 316 ssh_input_space(struct ssh *ssh, size_t len) 317 { 318 return (0 == sshbuf_check_reserve(ssh_packet_get_input(ssh), len)); 319 } 320 321 /* Read other side's version identification. */ 322 int 323 _ssh_read_banner(struct ssh *ssh, struct sshbuf *banner) 324 { 325 struct sshbuf *input = ssh_packet_get_input(ssh); 326 const char *mismatch = "Protocol mismatch.\r\n"; 327 const u_char *s = sshbuf_ptr(input); 328 u_char c; 329 char *cp = NULL, *remote_version = NULL; 330 int r = 0, remote_major, remote_minor, expect_nl; 331 size_t n, j; 332 333 for (j = n = 0;;) { 334 sshbuf_reset(banner); 335 expect_nl = 0; 336 for (;;) { 337 if (j >= sshbuf_len(input)) 338 return 0; /* insufficient data in input buf */ 339 c = s[j++]; 340 if (c == '\r') { 341 expect_nl = 1; 342 continue; 343 } 344 if (c == '\n') 345 break; 346 if (expect_nl) 347 goto bad; 348 if ((r = sshbuf_put_u8(banner, c)) != 0) 349 return r; 350 if (sshbuf_len(banner) > SSH_MAX_BANNER_LEN) 351 goto bad; 352 } 353 if (sshbuf_len(banner) >= 4 && 354 memcmp(sshbuf_ptr(banner), "SSH-", 4) == 0) 355 break; 356 debug_f("%.*s", (int)sshbuf_len(banner), 357 sshbuf_ptr(banner)); 358 /* Accept lines before banner only on client */ 359 if (ssh->kex->server || ++n > SSH_MAX_PRE_BANNER_LINES) { 360 bad: 361 if ((r = sshbuf_put(ssh_packet_get_output(ssh), 362 mismatch, strlen(mismatch))) != 0) 363 return r; 364 return SSH_ERR_NO_PROTOCOL_VERSION; 365 } 366 } 367 if ((r = sshbuf_consume(input, j)) != 0) 368 return r; 369 370 /* XXX remote version must be the same size as banner for sscanf */ 371 if ((cp = sshbuf_dup_string(banner)) == NULL || 372 (remote_version = calloc(1, sshbuf_len(banner))) == NULL) { 373 r = SSH_ERR_ALLOC_FAIL; 374 goto out; 375 } 376 377 /* 378 * Check that the versions match. In future this might accept 379 * several versions and set appropriate flags to handle them. 380 */ 381 if (sscanf(cp, "SSH-%d.%d-%[^\n]\n", 382 &remote_major, &remote_minor, remote_version) != 3) { 383 r = SSH_ERR_INVALID_FORMAT; 384 goto out; 385 } 386 debug("Remote protocol version %d.%d, remote software version %.100s", 387 remote_major, remote_minor, remote_version); 388 389 ssh->compat = compat_datafellows(remote_version); 390 if (remote_major == 1 && remote_minor == 99) { 391 remote_major = 2; 392 remote_minor = 0; 393 } 394 if (remote_major != 2) 395 r = SSH_ERR_PROTOCOL_MISMATCH; 396 397 debug("Remote version string %.100s", cp); 398 out: 399 free(cp); 400 free(remote_version); 401 return r; 402 } 403 404 /* Send our own protocol version identification. */ 405 int 406 _ssh_send_banner(struct ssh *ssh, struct sshbuf *banner) 407 { 408 char *cp; 409 int r; 410 411 if ((r = sshbuf_putf(banner, "SSH-2.0-%.100s\r\n", SSH_VERSION)) != 0) 412 return r; 413 if ((r = sshbuf_putb(ssh_packet_get_output(ssh), banner)) != 0) 414 return r; 415 /* Remove trailing \r\n */ 416 if ((r = sshbuf_consume_end(banner, 2)) != 0) 417 return r; 418 if ((cp = sshbuf_dup_string(banner)) == NULL) 419 return SSH_ERR_ALLOC_FAIL; 420 debug("Local version string %.100s", cp); 421 free(cp); 422 return 0; 423 } 424 425 int 426 _ssh_exchange_banner(struct ssh *ssh) 427 { 428 struct kex *kex = ssh->kex; 429 int r; 430 431 /* 432 * if _ssh_read_banner() cannot parse a full version string 433 * it will return NULL and we end up calling it again. 434 */ 435 436 r = 0; 437 if (kex->server) { 438 if (sshbuf_len(ssh->kex->server_version) == 0) 439 r = _ssh_send_banner(ssh, ssh->kex->server_version); 440 if (r == 0 && 441 sshbuf_len(ssh->kex->server_version) != 0 && 442 sshbuf_len(ssh->kex->client_version) == 0) 443 r = _ssh_read_banner(ssh, ssh->kex->client_version); 444 } else { 445 if (sshbuf_len(ssh->kex->server_version) == 0) 446 r = _ssh_read_banner(ssh, ssh->kex->server_version); 447 if (r == 0 && 448 sshbuf_len(ssh->kex->server_version) != 0 && 449 sshbuf_len(ssh->kex->client_version) == 0) 450 r = _ssh_send_banner(ssh, ssh->kex->client_version); 451 } 452 if (r != 0) 453 return r; 454 /* start initial kex as soon as we have exchanged the banners */ 455 if (sshbuf_len(ssh->kex->server_version) != 0 && 456 sshbuf_len(ssh->kex->client_version) != 0) { 457 if ((r = _ssh_order_hostkeyalgs(ssh)) != 0 || 458 (r = kex_send_kexinit(ssh)) != 0) 459 return r; 460 } 461 return 0; 462 } 463 464 struct sshkey * 465 _ssh_host_public_key(int type, int nid, struct ssh *ssh) 466 { 467 struct key_entry *k; 468 469 debug3_f("need %d", type); 470 TAILQ_FOREACH(k, &ssh->public_keys, next) { 471 debug3_f("check %s", sshkey_type(k->key)); 472 if (k->key->type == type && 473 (type != KEY_ECDSA || k->key->ecdsa_nid == nid)) 474 return (k->key); 475 } 476 return (NULL); 477 } 478 479 struct sshkey * 480 _ssh_host_private_key(int type, int nid, struct ssh *ssh) 481 { 482 struct key_entry *k; 483 484 debug3_f("need %d", type); 485 TAILQ_FOREACH(k, &ssh->private_keys, next) { 486 debug3_f("check %s", sshkey_type(k->key)); 487 if (k->key->type == type && 488 (type != KEY_ECDSA || k->key->ecdsa_nid == nid)) 489 return (k->key); 490 } 491 return (NULL); 492 } 493 494 int 495 _ssh_verify_host_key(struct sshkey *hostkey, struct ssh *ssh) 496 { 497 struct key_entry *k; 498 499 debug3_f("need %s", sshkey_type(hostkey)); 500 TAILQ_FOREACH(k, &ssh->public_keys, next) { 501 debug3_f("check %s", sshkey_type(k->key)); 502 if (sshkey_equal_public(hostkey, k->key)) 503 return (0); /* ok */ 504 } 505 return (-1); /* failed */ 506 } 507 508 /* offer hostkey algorithms in kexinit depending on registered keys */ 509 int 510 _ssh_order_hostkeyalgs(struct ssh *ssh) 511 { 512 struct key_entry *k; 513 char *orig, *avail, *oavail = NULL, *alg, *replace = NULL; 514 char **proposal; 515 size_t maxlen; 516 int ktype, r; 517 518 /* XXX we de-serialize ssh->kex->my, modify it, and change it */ 519 if ((r = kex_buf2prop(ssh->kex->my, NULL, &proposal)) != 0) 520 return r; 521 orig = proposal[PROPOSAL_SERVER_HOST_KEY_ALGS]; 522 if ((oavail = avail = strdup(orig)) == NULL) { 523 r = SSH_ERR_ALLOC_FAIL; 524 goto out; 525 } 526 maxlen = strlen(avail) + 1; 527 if ((replace = calloc(1, maxlen)) == NULL) { 528 r = SSH_ERR_ALLOC_FAIL; 529 goto out; 530 } 531 *replace = '\0'; 532 while ((alg = strsep(&avail, ",")) && *alg != '\0') { 533 if ((ktype = sshkey_type_from_name(alg)) == KEY_UNSPEC) 534 continue; 535 TAILQ_FOREACH(k, &ssh->public_keys, next) { 536 if (k->key->type == ktype || 537 (sshkey_is_cert(k->key) && k->key->type == 538 sshkey_type_plain(ktype))) { 539 if (*replace != '\0') 540 strlcat(replace, ",", maxlen); 541 strlcat(replace, alg, maxlen); 542 break; 543 } 544 } 545 } 546 if (*replace != '\0') { 547 debug2_f("orig/%d %s", ssh->kex->server, orig); 548 debug2_f("replace/%d %s", ssh->kex->server, replace); 549 free(orig); 550 proposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = replace; 551 replace = NULL; /* owned by proposal */ 552 r = kex_prop2buf(ssh->kex->my, proposal); 553 } 554 out: 555 free(oavail); 556 free(replace); 557 kex_prop_free(proposal); 558 return r; 559 } 560 561 int 562 _ssh_host_key_sign(struct ssh *ssh, struct sshkey *privkey, 563 struct sshkey *pubkey, u_char **signature, size_t *slen, 564 const u_char *data, size_t dlen, const char *alg) 565 { 566 return sshkey_sign(privkey, signature, slen, data, dlen, 567 alg, NULL, NULL, ssh->compat); 568 } 569