1 /* $OpenBSD: ssh_api.c,v 1.28 2024/01/09 21:39:14 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 int 60 mm_sshkey_sign(struct sshkey *key, u_char **sigp, u_int *lenp, 61 const u_char *data, u_int datalen, const char *alg, 62 const char *sk_provider, const char *sk_pin, u_int compat) 63 { 64 return (-1); 65 } 66 67 #ifdef WITH_OPENSSL 68 DH * 69 mm_choose_dh(int min, int nbits, int max) 70 { 71 return (NULL); 72 } 73 #endif 74 75 /* API */ 76 77 int 78 ssh_init(struct ssh **sshp, int is_server, struct kex_params *kex_params) 79 { 80 char *myproposal[PROPOSAL_MAX] = { KEX_CLIENT }; 81 char *populated[PROPOSAL_MAX]; 82 struct ssh *ssh; 83 char **proposal; 84 static int called; 85 int r; 86 87 if (!called) { 88 #ifdef WITH_OPENSSL 89 OpenSSL_add_all_algorithms(); 90 #endif 91 called = 1; 92 } 93 94 if ((ssh = ssh_packet_set_connection(NULL, -1, -1)) == NULL) 95 return SSH_ERR_ALLOC_FAIL; 96 if (is_server) 97 ssh_packet_set_server(ssh); 98 99 /* Initialize key exchange */ 100 proposal = kex_params ? kex_params->proposal : myproposal; 101 kex_proposal_populate_entries(ssh, populated, 102 proposal[PROPOSAL_KEX_ALGS], 103 proposal[PROPOSAL_ENC_ALGS_CTOS], 104 proposal[PROPOSAL_MAC_ALGS_CTOS], 105 proposal[PROPOSAL_COMP_ALGS_CTOS], 106 proposal[PROPOSAL_SERVER_HOST_KEY_ALGS]); 107 r = kex_ready(ssh, populated); 108 kex_proposal_free_entries(populated); 109 if (r != 0) { 110 ssh_free(ssh); 111 return r; 112 } 113 114 ssh->kex->server = is_server; 115 if (is_server) { 116 #ifdef WITH_OPENSSL 117 ssh->kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_server; 118 ssh->kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_server; 119 ssh->kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_server; 120 ssh->kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_server; 121 ssh->kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_server; 122 ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_server; 123 ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_server; 124 ssh->kex->kex[KEX_ECDH_SHA2] = kex_gen_server; 125 #endif /* WITH_OPENSSL */ 126 ssh->kex->kex[KEX_C25519_SHA256] = kex_gen_server; 127 ssh->kex->kex[KEX_KEM_SNTRUP761X25519_SHA512] = kex_gen_server; 128 ssh->kex->load_host_public_key=&_ssh_host_public_key; 129 ssh->kex->load_host_private_key=&_ssh_host_private_key; 130 ssh->kex->sign=&_ssh_host_key_sign; 131 } else { 132 #ifdef WITH_OPENSSL 133 ssh->kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_client; 134 ssh->kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_client; 135 ssh->kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_client; 136 ssh->kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_client; 137 ssh->kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_client; 138 ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_client; 139 ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_client; 140 ssh->kex->kex[KEX_ECDH_SHA2] = kex_gen_client; 141 #endif /* WITH_OPENSSL */ 142 ssh->kex->kex[KEX_C25519_SHA256] = kex_gen_client; 143 ssh->kex->kex[KEX_KEM_SNTRUP761X25519_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 if (ssh == NULL) 156 return; 157 158 /* 159 * we've only created the public keys variants in case we 160 * are a acting as a server. 161 */ 162 while ((k = TAILQ_FIRST(&ssh->public_keys)) != NULL) { 163 TAILQ_REMOVE(&ssh->public_keys, k, next); 164 if (ssh->kex && ssh->kex->server) 165 sshkey_free(k->key); 166 free(k); 167 } 168 while ((k = TAILQ_FIRST(&ssh->private_keys)) != NULL) { 169 TAILQ_REMOVE(&ssh->private_keys, k, next); 170 free(k); 171 } 172 ssh_packet_close(ssh); 173 free(ssh); 174 } 175 176 void 177 ssh_set_app_data(struct ssh *ssh, void *app_data) 178 { 179 ssh->app_data = app_data; 180 } 181 182 void * 183 ssh_get_app_data(struct ssh *ssh) 184 { 185 return ssh->app_data; 186 } 187 188 /* Returns < 0 on error, 0 otherwise */ 189 int 190 ssh_add_hostkey(struct ssh *ssh, struct sshkey *key) 191 { 192 struct sshkey *pubkey = NULL; 193 struct key_entry *k = NULL, *k_prv = NULL; 194 int r; 195 196 if (ssh->kex->server) { 197 if ((r = sshkey_from_private(key, &pubkey)) != 0) 198 return r; 199 if ((k = malloc(sizeof(*k))) == NULL || 200 (k_prv = malloc(sizeof(*k_prv))) == NULL) { 201 free(k); 202 sshkey_free(pubkey); 203 return SSH_ERR_ALLOC_FAIL; 204 } 205 k_prv->key = key; 206 TAILQ_INSERT_TAIL(&ssh->private_keys, k_prv, next); 207 208 /* add the public key, too */ 209 k->key = pubkey; 210 TAILQ_INSERT_TAIL(&ssh->public_keys, k, next); 211 r = 0; 212 } else { 213 if ((k = malloc(sizeof(*k))) == NULL) 214 return SSH_ERR_ALLOC_FAIL; 215 k->key = key; 216 TAILQ_INSERT_TAIL(&ssh->public_keys, k, next); 217 r = 0; 218 } 219 220 return r; 221 } 222 223 int 224 ssh_set_verify_host_key_callback(struct ssh *ssh, 225 int (*cb)(struct sshkey *, struct ssh *)) 226 { 227 if (cb == NULL || ssh->kex == NULL) 228 return SSH_ERR_INVALID_ARGUMENT; 229 230 ssh->kex->verify_host_key = cb; 231 232 return 0; 233 } 234 235 int 236 ssh_input_append(struct ssh *ssh, const u_char *data, size_t len) 237 { 238 return sshbuf_put(ssh_packet_get_input(ssh), data, len); 239 } 240 241 int 242 ssh_packet_next(struct ssh *ssh, u_char *typep) 243 { 244 int r; 245 u_int32_t seqnr; 246 u_char type; 247 248 /* 249 * Try to read a packet. Return SSH_MSG_NONE if no packet or not 250 * enough data. 251 */ 252 *typep = SSH_MSG_NONE; 253 if (sshbuf_len(ssh->kex->client_version) == 0 || 254 sshbuf_len(ssh->kex->server_version) == 0) 255 return _ssh_exchange_banner(ssh); 256 /* 257 * If we enough data and a dispatch function then 258 * call the function and get the next packet. 259 * Otherwise return the packet type to the caller so it 260 * can decide how to go on. 261 * 262 * We will only call the dispatch function for: 263 * 20-29 Algorithm negotiation 264 * 30-49 Key exchange method specific (numbers can be reused for 265 * different authentication methods) 266 */ 267 for (;;) { 268 if ((r = ssh_packet_read_poll2(ssh, &type, &seqnr)) != 0) 269 return r; 270 if (type > 0 && type < DISPATCH_MAX && 271 type >= SSH2_MSG_KEXINIT && type <= SSH2_MSG_TRANSPORT_MAX && 272 ssh->dispatch[type] != NULL) { 273 if ((r = (*ssh->dispatch[type])(type, seqnr, ssh)) != 0) 274 return r; 275 } else { 276 *typep = type; 277 return 0; 278 } 279 } 280 } 281 282 const u_char * 283 ssh_packet_payload(struct ssh *ssh, size_t *lenp) 284 { 285 return sshpkt_ptr(ssh, lenp); 286 } 287 288 int 289 ssh_packet_put(struct ssh *ssh, int type, const u_char *data, size_t len) 290 { 291 int r; 292 293 if ((r = sshpkt_start(ssh, type)) != 0 || 294 (r = sshpkt_put(ssh, data, len)) != 0 || 295 (r = sshpkt_send(ssh)) != 0) 296 return r; 297 return 0; 298 } 299 300 const u_char * 301 ssh_output_ptr(struct ssh *ssh, size_t *len) 302 { 303 struct sshbuf *output = ssh_packet_get_output(ssh); 304 305 *len = sshbuf_len(output); 306 return sshbuf_ptr(output); 307 } 308 309 int 310 ssh_output_consume(struct ssh *ssh, size_t len) 311 { 312 return sshbuf_consume(ssh_packet_get_output(ssh), len); 313 } 314 315 int 316 ssh_output_space(struct ssh *ssh, size_t len) 317 { 318 return (0 == sshbuf_check_reserve(ssh_packet_get_output(ssh), len)); 319 } 320 321 int 322 ssh_input_space(struct ssh *ssh, size_t len) 323 { 324 return (0 == sshbuf_check_reserve(ssh_packet_get_input(ssh), len)); 325 } 326 327 /* Read other side's version identification. */ 328 int 329 _ssh_read_banner(struct ssh *ssh, struct sshbuf *banner) 330 { 331 struct sshbuf *input = ssh_packet_get_input(ssh); 332 const char *mismatch = "Protocol mismatch.\r\n"; 333 const u_char *s = sshbuf_ptr(input); 334 u_char c; 335 char *cp = NULL, *remote_version = NULL; 336 int r = 0, remote_major, remote_minor, expect_nl; 337 size_t n, j; 338 339 for (j = n = 0;;) { 340 sshbuf_reset(banner); 341 expect_nl = 0; 342 for (;;) { 343 if (j >= sshbuf_len(input)) 344 return 0; /* insufficient data in input buf */ 345 c = s[j++]; 346 if (c == '\r') { 347 expect_nl = 1; 348 continue; 349 } 350 if (c == '\n') 351 break; 352 if (expect_nl) 353 goto bad; 354 if ((r = sshbuf_put_u8(banner, c)) != 0) 355 return r; 356 if (sshbuf_len(banner) > SSH_MAX_BANNER_LEN) 357 goto bad; 358 } 359 if (sshbuf_len(banner) >= 4 && 360 memcmp(sshbuf_ptr(banner), "SSH-", 4) == 0) 361 break; 362 debug_f("%.*s", (int)sshbuf_len(banner), 363 sshbuf_ptr(banner)); 364 /* Accept lines before banner only on client */ 365 if (ssh->kex->server || ++n > SSH_MAX_PRE_BANNER_LINES) { 366 bad: 367 if ((r = sshbuf_put(ssh_packet_get_output(ssh), 368 mismatch, strlen(mismatch))) != 0) 369 return r; 370 return SSH_ERR_NO_PROTOCOL_VERSION; 371 } 372 } 373 if ((r = sshbuf_consume(input, j)) != 0) 374 return r; 375 376 /* XXX remote version must be the same size as banner for sscanf */ 377 if ((cp = sshbuf_dup_string(banner)) == NULL || 378 (remote_version = calloc(1, sshbuf_len(banner))) == NULL) { 379 r = SSH_ERR_ALLOC_FAIL; 380 goto out; 381 } 382 383 /* 384 * Check that the versions match. In future this might accept 385 * several versions and set appropriate flags to handle them. 386 */ 387 if (sscanf(cp, "SSH-%d.%d-%[^\n]\n", 388 &remote_major, &remote_minor, remote_version) != 3) { 389 r = SSH_ERR_INVALID_FORMAT; 390 goto out; 391 } 392 debug("Remote protocol version %d.%d, remote software version %.100s", 393 remote_major, remote_minor, remote_version); 394 395 compat_banner(ssh, remote_version); 396 if (remote_major == 1 && remote_minor == 99) { 397 remote_major = 2; 398 remote_minor = 0; 399 } 400 if (remote_major != 2) 401 r = SSH_ERR_PROTOCOL_MISMATCH; 402 403 debug("Remote version string %.100s", cp); 404 out: 405 free(cp); 406 free(remote_version); 407 return r; 408 } 409 410 /* Send our own protocol version identification. */ 411 int 412 _ssh_send_banner(struct ssh *ssh, struct sshbuf *banner) 413 { 414 char *cp; 415 int r; 416 417 if ((r = sshbuf_putf(banner, "SSH-2.0-%.100s\r\n", SSH_VERSION)) != 0) 418 return r; 419 if ((r = sshbuf_putb(ssh_packet_get_output(ssh), banner)) != 0) 420 return r; 421 /* Remove trailing \r\n */ 422 if ((r = sshbuf_consume_end(banner, 2)) != 0) 423 return r; 424 if ((cp = sshbuf_dup_string(banner)) == NULL) 425 return SSH_ERR_ALLOC_FAIL; 426 debug("Local version string %.100s", cp); 427 free(cp); 428 return 0; 429 } 430 431 int 432 _ssh_exchange_banner(struct ssh *ssh) 433 { 434 struct kex *kex = ssh->kex; 435 int r; 436 437 /* 438 * if _ssh_read_banner() cannot parse a full version string 439 * it will return NULL and we end up calling it again. 440 */ 441 442 r = 0; 443 if (kex->server) { 444 if (sshbuf_len(ssh->kex->server_version) == 0) 445 r = _ssh_send_banner(ssh, ssh->kex->server_version); 446 if (r == 0 && 447 sshbuf_len(ssh->kex->server_version) != 0 && 448 sshbuf_len(ssh->kex->client_version) == 0) 449 r = _ssh_read_banner(ssh, ssh->kex->client_version); 450 } else { 451 if (sshbuf_len(ssh->kex->server_version) == 0) 452 r = _ssh_read_banner(ssh, ssh->kex->server_version); 453 if (r == 0 && 454 sshbuf_len(ssh->kex->server_version) != 0 && 455 sshbuf_len(ssh->kex->client_version) == 0) 456 r = _ssh_send_banner(ssh, ssh->kex->client_version); 457 } 458 if (r != 0) 459 return r; 460 /* start initial kex as soon as we have exchanged the banners */ 461 if (sshbuf_len(ssh->kex->server_version) != 0 && 462 sshbuf_len(ssh->kex->client_version) != 0) { 463 if ((r = _ssh_order_hostkeyalgs(ssh)) != 0 || 464 (r = kex_send_kexinit(ssh)) != 0) 465 return r; 466 } 467 return 0; 468 } 469 470 struct sshkey * 471 _ssh_host_public_key(int type, int nid, struct ssh *ssh) 472 { 473 struct key_entry *k; 474 475 debug3_f("need %d", type); 476 TAILQ_FOREACH(k, &ssh->public_keys, next) { 477 debug3_f("check %s", sshkey_type(k->key)); 478 if (k->key->type == type && 479 (type != KEY_ECDSA || k->key->ecdsa_nid == nid)) 480 return (k->key); 481 } 482 return (NULL); 483 } 484 485 struct sshkey * 486 _ssh_host_private_key(int type, int nid, struct ssh *ssh) 487 { 488 struct key_entry *k; 489 490 debug3_f("need %d", type); 491 TAILQ_FOREACH(k, &ssh->private_keys, next) { 492 debug3_f("check %s", sshkey_type(k->key)); 493 if (k->key->type == type && 494 (type != KEY_ECDSA || k->key->ecdsa_nid == nid)) 495 return (k->key); 496 } 497 return (NULL); 498 } 499 500 int 501 _ssh_verify_host_key(struct sshkey *hostkey, struct ssh *ssh) 502 { 503 struct key_entry *k; 504 505 debug3_f("need %s", sshkey_type(hostkey)); 506 TAILQ_FOREACH(k, &ssh->public_keys, next) { 507 debug3_f("check %s", sshkey_type(k->key)); 508 if (sshkey_equal_public(hostkey, k->key)) 509 return (0); /* ok */ 510 } 511 return (-1); /* failed */ 512 } 513 514 /* offer hostkey algorithms in kexinit depending on registered keys */ 515 int 516 _ssh_order_hostkeyalgs(struct ssh *ssh) 517 { 518 struct key_entry *k; 519 char *orig, *avail, *oavail = NULL, *alg, *replace = NULL; 520 char **proposal; 521 size_t maxlen; 522 int ktype, r; 523 524 /* XXX we de-serialize ssh->kex->my, modify it, and change it */ 525 if ((r = kex_buf2prop(ssh->kex->my, NULL, &proposal)) != 0) 526 return r; 527 orig = proposal[PROPOSAL_SERVER_HOST_KEY_ALGS]; 528 if ((oavail = avail = strdup(orig)) == NULL) { 529 r = SSH_ERR_ALLOC_FAIL; 530 goto out; 531 } 532 maxlen = strlen(avail) + 1; 533 if ((replace = calloc(1, maxlen)) == NULL) { 534 r = SSH_ERR_ALLOC_FAIL; 535 goto out; 536 } 537 *replace = '\0'; 538 while ((alg = strsep(&avail, ",")) && *alg != '\0') { 539 if ((ktype = sshkey_type_from_name(alg)) == KEY_UNSPEC) 540 continue; 541 TAILQ_FOREACH(k, &ssh->public_keys, next) { 542 if (k->key->type == ktype || 543 (sshkey_is_cert(k->key) && k->key->type == 544 sshkey_type_plain(ktype))) { 545 if (*replace != '\0') 546 strlcat(replace, ",", maxlen); 547 strlcat(replace, alg, maxlen); 548 break; 549 } 550 } 551 } 552 if (*replace != '\0') { 553 debug2_f("orig/%d %s", ssh->kex->server, orig); 554 debug2_f("replace/%d %s", ssh->kex->server, replace); 555 free(orig); 556 proposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = replace; 557 replace = NULL; /* owned by proposal */ 558 r = kex_prop2buf(ssh->kex->my, proposal); 559 } 560 out: 561 free(oavail); 562 free(replace); 563 kex_prop_free(proposal); 564 return r; 565 } 566 567 int 568 _ssh_host_key_sign(struct ssh *ssh, struct sshkey *privkey, 569 struct sshkey *pubkey, u_char **signature, size_t *slen, 570 const u_char *data, size_t dlen, const char *alg) 571 { 572 return sshkey_sign(privkey, signature, slen, data, dlen, 573 alg, NULL, NULL, ssh->compat); 574 } 575