1 /* $OpenBSD: ssh_api.c,v 1.29 2024/05/17 00:30:24 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 <sys/types.h> 21 22 #include <stdio.h> 23 #include <stdlib.h> 24 25 #include "ssh_api.h" 26 #include "compat.h" 27 #include "log.h" 28 #include "authfile.h" 29 #include "sshkey.h" 30 #include "dh.h" 31 #include "misc.h" 32 #include "ssh2.h" 33 #include "version.h" 34 #include "myproposal.h" 35 #include "ssherr.h" 36 #include "sshbuf.h" 37 38 #include "openbsd-compat/openssl-compat.h" 39 40 #include <string.h> 41 42 int _ssh_exchange_banner(struct ssh *); 43 int _ssh_send_banner(struct ssh *, struct sshbuf *); 44 int _ssh_read_banner(struct ssh *, struct sshbuf *); 45 int _ssh_order_hostkeyalgs(struct ssh *); 46 int _ssh_verify_host_key(struct sshkey *, struct ssh *); 47 struct sshkey *_ssh_host_public_key(int, int, struct ssh *); 48 struct sshkey *_ssh_host_private_key(int, int, struct ssh *); 49 int _ssh_host_key_sign(struct ssh *, struct sshkey *, struct sshkey *, 50 u_char **, size_t *, const u_char *, size_t, const char *); 51 52 /* 53 * stubs for privsep calls in the server side implementation of kex. 54 */ 55 int mm_sshkey_sign(struct sshkey *, u_char **, u_int *, 56 const u_char *, u_int, const char *, const char *, const char *, u_int); 57 58 #ifdef WITH_OPENSSL 59 DH *mm_choose_dh(int, int, int); 60 #endif 61 62 int 63 mm_sshkey_sign(struct sshkey *key, u_char **sigp, u_int *lenp, 64 const u_char *data, u_int datalen, const char *alg, 65 const char *sk_provider, const char *sk_pin, u_int compat) 66 { 67 size_t slen = 0; 68 int ret; 69 70 ret = sshkey_sign(key, sigp, &slen, data, datalen, alg, 71 sk_provider, sk_pin, compat); 72 *lenp = slen; 73 return ret; 74 } 75 76 #ifdef WITH_OPENSSL 77 DH * 78 mm_choose_dh(int min, int nbits, int max) 79 { 80 return choose_dh(min, nbits, max); 81 } 82 #endif 83 84 /* API */ 85 86 int 87 ssh_init(struct ssh **sshp, int is_server, struct kex_params *kex_params) 88 { 89 char *myproposal[PROPOSAL_MAX] = { KEX_CLIENT }; 90 char *populated[PROPOSAL_MAX]; 91 struct ssh *ssh; 92 char **proposal; 93 static int called; 94 int r; 95 96 if (!called) { 97 seed_rng(); 98 called = 1; 99 } 100 101 if ((ssh = ssh_packet_set_connection(NULL, -1, -1)) == NULL) 102 return SSH_ERR_ALLOC_FAIL; 103 if (is_server) 104 ssh_packet_set_server(ssh); 105 106 /* Initialize key exchange */ 107 proposal = kex_params ? kex_params->proposal : myproposal; 108 kex_proposal_populate_entries(ssh, populated, 109 proposal[PROPOSAL_KEX_ALGS], 110 proposal[PROPOSAL_ENC_ALGS_CTOS], 111 proposal[PROPOSAL_MAC_ALGS_CTOS], 112 proposal[PROPOSAL_COMP_ALGS_CTOS], 113 proposal[PROPOSAL_SERVER_HOST_KEY_ALGS]); 114 r = kex_ready(ssh, populated); 115 kex_proposal_free_entries(populated); 116 if (r != 0) { 117 ssh_free(ssh); 118 return r; 119 } 120 121 ssh->kex->server = is_server; 122 if (is_server) { 123 #ifdef WITH_OPENSSL 124 ssh->kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_server; 125 ssh->kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_server; 126 ssh->kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_server; 127 ssh->kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_server; 128 ssh->kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_server; 129 ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_server; 130 ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_server; 131 # ifdef OPENSSL_HAS_ECC 132 ssh->kex->kex[KEX_ECDH_SHA2] = kex_gen_server; 133 # endif 134 #endif /* WITH_OPENSSL */ 135 ssh->kex->kex[KEX_C25519_SHA256] = kex_gen_server; 136 ssh->kex->kex[KEX_KEM_SNTRUP761X25519_SHA512] = kex_gen_server; 137 ssh->kex->load_host_public_key=&_ssh_host_public_key; 138 ssh->kex->load_host_private_key=&_ssh_host_private_key; 139 ssh->kex->sign=&_ssh_host_key_sign; 140 } else { 141 #ifdef WITH_OPENSSL 142 ssh->kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_client; 143 ssh->kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_client; 144 ssh->kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_client; 145 ssh->kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_client; 146 ssh->kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_client; 147 ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_client; 148 ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_client; 149 # ifdef OPENSSL_HAS_ECC 150 ssh->kex->kex[KEX_ECDH_SHA2] = kex_gen_client; 151 # endif 152 #endif /* WITH_OPENSSL */ 153 ssh->kex->kex[KEX_C25519_SHA256] = kex_gen_client; 154 ssh->kex->kex[KEX_KEM_SNTRUP761X25519_SHA512] = kex_gen_client; 155 ssh->kex->verify_host_key =&_ssh_verify_host_key; 156 } 157 *sshp = ssh; 158 return 0; 159 } 160 161 void 162 ssh_free(struct ssh *ssh) 163 { 164 struct key_entry *k; 165 166 if (ssh == NULL) 167 return; 168 169 /* 170 * we've only created the public keys variants in case we 171 * are a acting as a server. 172 */ 173 while ((k = TAILQ_FIRST(&ssh->public_keys)) != NULL) { 174 TAILQ_REMOVE(&ssh->public_keys, k, next); 175 if (ssh->kex && ssh->kex->server) 176 sshkey_free(k->key); 177 free(k); 178 } 179 while ((k = TAILQ_FIRST(&ssh->private_keys)) != NULL) { 180 TAILQ_REMOVE(&ssh->private_keys, k, next); 181 free(k); 182 } 183 ssh_packet_close(ssh); 184 free(ssh); 185 } 186 187 void 188 ssh_set_app_data(struct ssh *ssh, void *app_data) 189 { 190 ssh->app_data = app_data; 191 } 192 193 void * 194 ssh_get_app_data(struct ssh *ssh) 195 { 196 return ssh->app_data; 197 } 198 199 /* Returns < 0 on error, 0 otherwise */ 200 int 201 ssh_add_hostkey(struct ssh *ssh, struct sshkey *key) 202 { 203 struct sshkey *pubkey = NULL; 204 struct key_entry *k = NULL, *k_prv = NULL; 205 int r; 206 207 if (ssh->kex->server) { 208 if ((r = sshkey_from_private(key, &pubkey)) != 0) 209 return r; 210 if ((k = malloc(sizeof(*k))) == NULL || 211 (k_prv = malloc(sizeof(*k_prv))) == NULL) { 212 free(k); 213 sshkey_free(pubkey); 214 return SSH_ERR_ALLOC_FAIL; 215 } 216 k_prv->key = key; 217 TAILQ_INSERT_TAIL(&ssh->private_keys, k_prv, next); 218 219 /* add the public key, too */ 220 k->key = pubkey; 221 TAILQ_INSERT_TAIL(&ssh->public_keys, k, next); 222 r = 0; 223 } else { 224 if ((k = malloc(sizeof(*k))) == NULL) 225 return SSH_ERR_ALLOC_FAIL; 226 k->key = key; 227 TAILQ_INSERT_TAIL(&ssh->public_keys, k, next); 228 r = 0; 229 } 230 231 return r; 232 } 233 234 int 235 ssh_set_verify_host_key_callback(struct ssh *ssh, 236 int (*cb)(struct sshkey *, struct ssh *)) 237 { 238 if (cb == NULL || ssh->kex == NULL) 239 return SSH_ERR_INVALID_ARGUMENT; 240 241 ssh->kex->verify_host_key = cb; 242 243 return 0; 244 } 245 246 int 247 ssh_input_append(struct ssh *ssh, const u_char *data, size_t len) 248 { 249 return sshbuf_put(ssh_packet_get_input(ssh), data, len); 250 } 251 252 int 253 ssh_packet_next(struct ssh *ssh, u_char *typep) 254 { 255 int r; 256 u_int32_t seqnr; 257 u_char type; 258 259 /* 260 * Try to read a packet. Return SSH_MSG_NONE if no packet or not 261 * enough data. 262 */ 263 *typep = SSH_MSG_NONE; 264 if (sshbuf_len(ssh->kex->client_version) == 0 || 265 sshbuf_len(ssh->kex->server_version) == 0) 266 return _ssh_exchange_banner(ssh); 267 /* 268 * If we enough data and a dispatch function then 269 * call the function and get the next packet. 270 * Otherwise return the packet type to the caller so it 271 * can decide how to go on. 272 * 273 * We will only call the dispatch function for: 274 * 20-29 Algorithm negotiation 275 * 30-49 Key exchange method specific (numbers can be reused for 276 * different authentication methods) 277 */ 278 for (;;) { 279 if ((r = ssh_packet_read_poll2(ssh, &type, &seqnr)) != 0) 280 return r; 281 if (type > 0 && type < DISPATCH_MAX && 282 type >= SSH2_MSG_KEXINIT && type <= SSH2_MSG_TRANSPORT_MAX && 283 ssh->dispatch[type] != NULL) { 284 if ((r = (*ssh->dispatch[type])(type, seqnr, ssh)) != 0) 285 return r; 286 } else { 287 *typep = type; 288 return 0; 289 } 290 } 291 } 292 293 const u_char * 294 ssh_packet_payload(struct ssh *ssh, size_t *lenp) 295 { 296 return sshpkt_ptr(ssh, lenp); 297 } 298 299 int 300 ssh_packet_put(struct ssh *ssh, int type, const u_char *data, size_t len) 301 { 302 int r; 303 304 if ((r = sshpkt_start(ssh, type)) != 0 || 305 (r = sshpkt_put(ssh, data, len)) != 0 || 306 (r = sshpkt_send(ssh)) != 0) 307 return r; 308 return 0; 309 } 310 311 const u_char * 312 ssh_output_ptr(struct ssh *ssh, size_t *len) 313 { 314 struct sshbuf *output = ssh_packet_get_output(ssh); 315 316 *len = sshbuf_len(output); 317 return sshbuf_ptr(output); 318 } 319 320 int 321 ssh_output_consume(struct ssh *ssh, size_t len) 322 { 323 return sshbuf_consume(ssh_packet_get_output(ssh), len); 324 } 325 326 int 327 ssh_output_space(struct ssh *ssh, size_t len) 328 { 329 return (0 == sshbuf_check_reserve(ssh_packet_get_output(ssh), len)); 330 } 331 332 int 333 ssh_input_space(struct ssh *ssh, size_t len) 334 { 335 return (0 == sshbuf_check_reserve(ssh_packet_get_input(ssh), len)); 336 } 337 338 /* Read other side's version identification. */ 339 int 340 _ssh_read_banner(struct ssh *ssh, struct sshbuf *banner) 341 { 342 struct sshbuf *input = ssh_packet_get_input(ssh); 343 const char *mismatch = "Protocol mismatch.\r\n"; 344 const u_char *s = sshbuf_ptr(input); 345 u_char c; 346 char *cp = NULL, *remote_version = NULL; 347 int r = 0, remote_major, remote_minor, expect_nl; 348 size_t n, j; 349 350 for (j = n = 0;;) { 351 sshbuf_reset(banner); 352 expect_nl = 0; 353 for (;;) { 354 if (j >= sshbuf_len(input)) 355 return 0; /* insufficient data in input buf */ 356 c = s[j++]; 357 if (c == '\r') { 358 expect_nl = 1; 359 continue; 360 } 361 if (c == '\n') 362 break; 363 if (expect_nl) 364 goto bad; 365 if ((r = sshbuf_put_u8(banner, c)) != 0) 366 return r; 367 if (sshbuf_len(banner) > SSH_MAX_BANNER_LEN) 368 goto bad; 369 } 370 if (sshbuf_len(banner) >= 4 && 371 memcmp(sshbuf_ptr(banner), "SSH-", 4) == 0) 372 break; 373 debug_f("%.*s", (int)sshbuf_len(banner), 374 sshbuf_ptr(banner)); 375 /* Accept lines before banner only on client */ 376 if (ssh->kex->server || ++n > SSH_MAX_PRE_BANNER_LINES) { 377 bad: 378 if ((r = sshbuf_put(ssh_packet_get_output(ssh), 379 mismatch, strlen(mismatch))) != 0) 380 return r; 381 return SSH_ERR_NO_PROTOCOL_VERSION; 382 } 383 } 384 if ((r = sshbuf_consume(input, j)) != 0) 385 return r; 386 387 /* XXX remote version must be the same size as banner for sscanf */ 388 if ((cp = sshbuf_dup_string(banner)) == NULL || 389 (remote_version = calloc(1, sshbuf_len(banner))) == NULL) { 390 r = SSH_ERR_ALLOC_FAIL; 391 goto out; 392 } 393 394 /* 395 * Check that the versions match. In future this might accept 396 * several versions and set appropriate flags to handle them. 397 */ 398 if (sscanf(cp, "SSH-%d.%d-%[^\n]\n", 399 &remote_major, &remote_minor, remote_version) != 3) { 400 r = SSH_ERR_INVALID_FORMAT; 401 goto out; 402 } 403 debug("Remote protocol version %d.%d, remote software version %.100s", 404 remote_major, remote_minor, remote_version); 405 406 compat_banner(ssh, remote_version); 407 if (remote_major == 1 && remote_minor == 99) { 408 remote_major = 2; 409 remote_minor = 0; 410 } 411 if (remote_major != 2) 412 r = SSH_ERR_PROTOCOL_MISMATCH; 413 414 debug("Remote version string %.100s", cp); 415 out: 416 free(cp); 417 free(remote_version); 418 return r; 419 } 420 421 /* Send our own protocol version identification. */ 422 int 423 _ssh_send_banner(struct ssh *ssh, struct sshbuf *banner) 424 { 425 char *cp; 426 int r; 427 428 if ((r = sshbuf_putf(banner, "SSH-2.0-%.100s\r\n", SSH_VERSION)) != 0) 429 return r; 430 if ((r = sshbuf_putb(ssh_packet_get_output(ssh), banner)) != 0) 431 return r; 432 /* Remove trailing \r\n */ 433 if ((r = sshbuf_consume_end(banner, 2)) != 0) 434 return r; 435 if ((cp = sshbuf_dup_string(banner)) == NULL) 436 return SSH_ERR_ALLOC_FAIL; 437 debug("Local version string %.100s", cp); 438 free(cp); 439 return 0; 440 } 441 442 int 443 _ssh_exchange_banner(struct ssh *ssh) 444 { 445 struct kex *kex = ssh->kex; 446 int r; 447 448 /* 449 * if _ssh_read_banner() cannot parse a full version string 450 * it will return NULL and we end up calling it again. 451 */ 452 453 r = 0; 454 if (kex->server) { 455 if (sshbuf_len(ssh->kex->server_version) == 0) 456 r = _ssh_send_banner(ssh, ssh->kex->server_version); 457 if (r == 0 && 458 sshbuf_len(ssh->kex->server_version) != 0 && 459 sshbuf_len(ssh->kex->client_version) == 0) 460 r = _ssh_read_banner(ssh, ssh->kex->client_version); 461 } else { 462 if (sshbuf_len(ssh->kex->server_version) == 0) 463 r = _ssh_read_banner(ssh, ssh->kex->server_version); 464 if (r == 0 && 465 sshbuf_len(ssh->kex->server_version) != 0 && 466 sshbuf_len(ssh->kex->client_version) == 0) 467 r = _ssh_send_banner(ssh, ssh->kex->client_version); 468 } 469 if (r != 0) 470 return r; 471 /* start initial kex as soon as we have exchanged the banners */ 472 if (sshbuf_len(ssh->kex->server_version) != 0 && 473 sshbuf_len(ssh->kex->client_version) != 0) { 474 if ((r = _ssh_order_hostkeyalgs(ssh)) != 0 || 475 (r = kex_send_kexinit(ssh)) != 0) 476 return r; 477 } 478 return 0; 479 } 480 481 struct sshkey * 482 _ssh_host_public_key(int type, int nid, struct ssh *ssh) 483 { 484 struct key_entry *k; 485 486 debug3_f("need %d", type); 487 TAILQ_FOREACH(k, &ssh->public_keys, next) { 488 debug3_f("check %s", sshkey_type(k->key)); 489 if (k->key->type == type && 490 (type != KEY_ECDSA || k->key->ecdsa_nid == nid)) 491 return (k->key); 492 } 493 return (NULL); 494 } 495 496 struct sshkey * 497 _ssh_host_private_key(int type, int nid, struct ssh *ssh) 498 { 499 struct key_entry *k; 500 501 debug3_f("need %d", type); 502 TAILQ_FOREACH(k, &ssh->private_keys, next) { 503 debug3_f("check %s", sshkey_type(k->key)); 504 if (k->key->type == type && 505 (type != KEY_ECDSA || k->key->ecdsa_nid == nid)) 506 return (k->key); 507 } 508 return (NULL); 509 } 510 511 int 512 _ssh_verify_host_key(struct sshkey *hostkey, struct ssh *ssh) 513 { 514 struct key_entry *k; 515 516 debug3_f("need %s", sshkey_type(hostkey)); 517 TAILQ_FOREACH(k, &ssh->public_keys, next) { 518 debug3_f("check %s", sshkey_type(k->key)); 519 if (sshkey_equal_public(hostkey, k->key)) 520 return (0); /* ok */ 521 } 522 return (-1); /* failed */ 523 } 524 525 /* offer hostkey algorithms in kexinit depending on registered keys */ 526 int 527 _ssh_order_hostkeyalgs(struct ssh *ssh) 528 { 529 struct key_entry *k; 530 char *orig, *avail, *oavail = NULL, *alg, *replace = NULL; 531 char **proposal; 532 size_t maxlen; 533 int ktype, r; 534 535 /* XXX we de-serialize ssh->kex->my, modify it, and change it */ 536 if ((r = kex_buf2prop(ssh->kex->my, NULL, &proposal)) != 0) 537 return r; 538 orig = proposal[PROPOSAL_SERVER_HOST_KEY_ALGS]; 539 if ((oavail = avail = strdup(orig)) == NULL) { 540 r = SSH_ERR_ALLOC_FAIL; 541 goto out; 542 } 543 maxlen = strlen(avail) + 1; 544 if ((replace = calloc(1, maxlen)) == NULL) { 545 r = SSH_ERR_ALLOC_FAIL; 546 goto out; 547 } 548 *replace = '\0'; 549 while ((alg = strsep(&avail, ",")) && *alg != '\0') { 550 if ((ktype = sshkey_type_from_name(alg)) == KEY_UNSPEC) 551 continue; 552 TAILQ_FOREACH(k, &ssh->public_keys, next) { 553 if (k->key->type == ktype || 554 (sshkey_is_cert(k->key) && k->key->type == 555 sshkey_type_plain(ktype))) { 556 if (*replace != '\0') 557 strlcat(replace, ",", maxlen); 558 strlcat(replace, alg, maxlen); 559 break; 560 } 561 } 562 } 563 if (*replace != '\0') { 564 debug2_f("orig/%d %s", ssh->kex->server, orig); 565 debug2_f("replace/%d %s", ssh->kex->server, replace); 566 free(orig); 567 proposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = replace; 568 replace = NULL; /* owned by proposal */ 569 r = kex_prop2buf(ssh->kex->my, proposal); 570 } 571 out: 572 free(oavail); 573 free(replace); 574 kex_prop_free(proposal); 575 return r; 576 } 577 578 int 579 _ssh_host_key_sign(struct ssh *ssh, struct sshkey *privkey, 580 struct sshkey *pubkey, u_char **signature, size_t *slen, 581 const u_char *data, size_t dlen, const char *alg) 582 { 583 return sshkey_sign(privkey, signature, slen, data, dlen, 584 alg, NULL, NULL, ssh->compat); 585 } 586