1 /* $OpenBSD: ssh_api.c,v 1.31 2024/09/09 02:39:57 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->kex[KEX_KEM_MLKEM768X25519_SHA256] = kex_gen_server; 138 ssh->kex->load_host_public_key=&_ssh_host_public_key; 139 ssh->kex->load_host_private_key=&_ssh_host_private_key; 140 ssh->kex->sign=&_ssh_host_key_sign; 141 } else { 142 #ifdef WITH_OPENSSL 143 ssh->kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_client; 144 ssh->kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_client; 145 ssh->kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_client; 146 ssh->kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_client; 147 ssh->kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_client; 148 ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_client; 149 ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_client; 150 # ifdef OPENSSL_HAS_ECC 151 ssh->kex->kex[KEX_ECDH_SHA2] = kex_gen_client; 152 # endif 153 #endif /* WITH_OPENSSL */ 154 ssh->kex->kex[KEX_C25519_SHA256] = kex_gen_client; 155 ssh->kex->kex[KEX_KEM_SNTRUP761X25519_SHA512] = kex_gen_client; 156 ssh->kex->kex[KEX_KEM_MLKEM768X25519_SHA256] = kex_gen_client; 157 ssh->kex->verify_host_key =&_ssh_verify_host_key; 158 } 159 *sshp = ssh; 160 return 0; 161 } 162 163 void 164 ssh_free(struct ssh *ssh) 165 { 166 struct key_entry *k; 167 168 if (ssh == NULL) 169 return; 170 171 /* 172 * we've only created the public keys variants in case we 173 * are a acting as a server. 174 */ 175 while ((k = TAILQ_FIRST(&ssh->public_keys)) != NULL) { 176 TAILQ_REMOVE(&ssh->public_keys, k, next); 177 if (ssh->kex && ssh->kex->server) 178 sshkey_free(k->key); 179 free(k); 180 } 181 while ((k = TAILQ_FIRST(&ssh->private_keys)) != NULL) { 182 TAILQ_REMOVE(&ssh->private_keys, k, next); 183 free(k); 184 } 185 ssh_packet_close(ssh); 186 free(ssh); 187 } 188 189 void 190 ssh_set_app_data(struct ssh *ssh, void *app_data) 191 { 192 ssh->app_data = app_data; 193 } 194 195 void * 196 ssh_get_app_data(struct ssh *ssh) 197 { 198 return ssh->app_data; 199 } 200 201 /* Returns < 0 on error, 0 otherwise */ 202 int 203 ssh_add_hostkey(struct ssh *ssh, struct sshkey *key) 204 { 205 struct sshkey *pubkey = NULL; 206 struct key_entry *k = NULL, *k_prv = NULL; 207 int r; 208 209 if (ssh->kex->server) { 210 if ((r = sshkey_from_private(key, &pubkey)) != 0) 211 return r; 212 if ((k = malloc(sizeof(*k))) == NULL || 213 (k_prv = malloc(sizeof(*k_prv))) == NULL) { 214 free(k); 215 sshkey_free(pubkey); 216 return SSH_ERR_ALLOC_FAIL; 217 } 218 k_prv->key = key; 219 TAILQ_INSERT_TAIL(&ssh->private_keys, k_prv, next); 220 221 /* add the public key, too */ 222 k->key = pubkey; 223 TAILQ_INSERT_TAIL(&ssh->public_keys, k, next); 224 r = 0; 225 } else { 226 if ((k = malloc(sizeof(*k))) == NULL) 227 return SSH_ERR_ALLOC_FAIL; 228 k->key = key; 229 TAILQ_INSERT_TAIL(&ssh->public_keys, k, next); 230 r = 0; 231 } 232 233 return r; 234 } 235 236 int 237 ssh_set_verify_host_key_callback(struct ssh *ssh, 238 int (*cb)(struct sshkey *, struct ssh *)) 239 { 240 if (cb == NULL || ssh->kex == NULL) 241 return SSH_ERR_INVALID_ARGUMENT; 242 243 ssh->kex->verify_host_key = cb; 244 245 return 0; 246 } 247 248 int 249 ssh_input_append(struct ssh *ssh, const u_char *data, size_t len) 250 { 251 return sshbuf_put(ssh_packet_get_input(ssh), data, len); 252 } 253 254 int 255 ssh_packet_next(struct ssh *ssh, u_char *typep) 256 { 257 int r; 258 u_int32_t seqnr; 259 u_char type; 260 261 /* 262 * Try to read a packet. Return SSH_MSG_NONE if no packet or not 263 * enough data. 264 */ 265 *typep = SSH_MSG_NONE; 266 if (sshbuf_len(ssh->kex->client_version) == 0 || 267 sshbuf_len(ssh->kex->server_version) == 0) 268 return _ssh_exchange_banner(ssh); 269 /* 270 * If we enough data and a dispatch function then 271 * call the function and get the next packet. 272 * Otherwise return the packet type to the caller so it 273 * can decide how to go on. 274 * 275 * We will only call the dispatch function for: 276 * 20-29 Algorithm negotiation 277 * 30-49 Key exchange method specific (numbers can be reused for 278 * different authentication methods) 279 */ 280 for (;;) { 281 if ((r = ssh_packet_read_poll2(ssh, &type, &seqnr)) != 0) 282 return r; 283 if (type > 0 && type < DISPATCH_MAX && 284 type >= SSH2_MSG_KEXINIT && type <= SSH2_MSG_TRANSPORT_MAX && 285 ssh->dispatch[type] != NULL) { 286 if ((r = (*ssh->dispatch[type])(type, seqnr, ssh)) != 0) 287 return r; 288 } else { 289 *typep = type; 290 return 0; 291 } 292 } 293 } 294 295 const u_char * 296 ssh_packet_payload(struct ssh *ssh, size_t *lenp) 297 { 298 return sshpkt_ptr(ssh, lenp); 299 } 300 301 int 302 ssh_packet_put(struct ssh *ssh, int type, const u_char *data, size_t len) 303 { 304 int r; 305 306 if ((r = sshpkt_start(ssh, type)) != 0 || 307 (r = sshpkt_put(ssh, data, len)) != 0 || 308 (r = sshpkt_send(ssh)) != 0) 309 return r; 310 return 0; 311 } 312 313 const u_char * 314 ssh_output_ptr(struct ssh *ssh, size_t *len) 315 { 316 struct sshbuf *output = ssh_packet_get_output(ssh); 317 318 *len = sshbuf_len(output); 319 return sshbuf_ptr(output); 320 } 321 322 int 323 ssh_output_consume(struct ssh *ssh, size_t len) 324 { 325 return sshbuf_consume(ssh_packet_get_output(ssh), len); 326 } 327 328 int 329 ssh_output_space(struct ssh *ssh, size_t len) 330 { 331 return (0 == sshbuf_check_reserve(ssh_packet_get_output(ssh), len)); 332 } 333 334 int 335 ssh_input_space(struct ssh *ssh, size_t len) 336 { 337 return (0 == sshbuf_check_reserve(ssh_packet_get_input(ssh), len)); 338 } 339 340 /* Read other side's version identification. */ 341 int 342 _ssh_read_banner(struct ssh *ssh, struct sshbuf *banner) 343 { 344 struct sshbuf *input = ssh_packet_get_input(ssh); 345 const char *mismatch = "Protocol mismatch.\r\n"; 346 const u_char *s = sshbuf_ptr(input); 347 u_char c; 348 char *cp = NULL, *remote_version = NULL; 349 int r = 0, remote_major, remote_minor, expect_nl; 350 size_t n, j; 351 352 for (j = n = 0;;) { 353 sshbuf_reset(banner); 354 expect_nl = 0; 355 for (;;) { 356 if (j >= sshbuf_len(input)) 357 return 0; /* insufficient data in input buf */ 358 c = s[j++]; 359 if (c == '\r') { 360 expect_nl = 1; 361 continue; 362 } 363 if (c == '\n') 364 break; 365 if (expect_nl) 366 goto bad; 367 if ((r = sshbuf_put_u8(banner, c)) != 0) 368 return r; 369 if (sshbuf_len(banner) > SSH_MAX_BANNER_LEN) 370 goto bad; 371 } 372 if (sshbuf_len(banner) >= 4 && 373 memcmp(sshbuf_ptr(banner), "SSH-", 4) == 0) 374 break; 375 debug_f("%.*s", (int)sshbuf_len(banner), 376 sshbuf_ptr(banner)); 377 /* Accept lines before banner only on client */ 378 if (ssh->kex->server || ++n > SSH_MAX_PRE_BANNER_LINES) { 379 bad: 380 if ((r = sshbuf_put(ssh_packet_get_output(ssh), 381 mismatch, strlen(mismatch))) != 0) 382 return r; 383 return SSH_ERR_NO_PROTOCOL_VERSION; 384 } 385 } 386 if ((r = sshbuf_consume(input, j)) != 0) 387 return r; 388 389 /* XXX remote version must be the same size as banner for sscanf */ 390 if ((cp = sshbuf_dup_string(banner)) == NULL || 391 (remote_version = calloc(1, sshbuf_len(banner))) == NULL) { 392 r = SSH_ERR_ALLOC_FAIL; 393 goto out; 394 } 395 396 /* 397 * Check that the versions match. In future this might accept 398 * several versions and set appropriate flags to handle them. 399 */ 400 if (sscanf(cp, "SSH-%d.%d-%[^\n]\n", 401 &remote_major, &remote_minor, remote_version) != 3) { 402 r = SSH_ERR_INVALID_FORMAT; 403 goto out; 404 } 405 debug("Remote protocol version %d.%d, remote software version %.100s", 406 remote_major, remote_minor, remote_version); 407 408 compat_banner(ssh, remote_version); 409 if (remote_major == 1 && remote_minor == 99) { 410 remote_major = 2; 411 remote_minor = 0; 412 } 413 if (remote_major != 2) 414 r = SSH_ERR_PROTOCOL_MISMATCH; 415 416 debug("Remote version string %.100s", cp); 417 out: 418 free(cp); 419 free(remote_version); 420 return r; 421 } 422 423 /* Send our own protocol version identification. */ 424 int 425 _ssh_send_banner(struct ssh *ssh, struct sshbuf *banner) 426 { 427 char *cp; 428 int r; 429 430 if ((r = sshbuf_putf(banner, "SSH-2.0-%.100s\r\n", SSH_VERSION)) != 0) 431 return r; 432 if ((r = sshbuf_putb(ssh_packet_get_output(ssh), banner)) != 0) 433 return r; 434 /* Remove trailing \r\n */ 435 if ((r = sshbuf_consume_end(banner, 2)) != 0) 436 return r; 437 if ((cp = sshbuf_dup_string(banner)) == NULL) 438 return SSH_ERR_ALLOC_FAIL; 439 debug("Local version string %.100s", cp); 440 free(cp); 441 return 0; 442 } 443 444 int 445 _ssh_exchange_banner(struct ssh *ssh) 446 { 447 struct kex *kex = ssh->kex; 448 int r; 449 450 /* 451 * if _ssh_read_banner() cannot parse a full version string 452 * it will return NULL and we end up calling it again. 453 */ 454 455 r = 0; 456 if (kex->server) { 457 if (sshbuf_len(ssh->kex->server_version) == 0) 458 r = _ssh_send_banner(ssh, ssh->kex->server_version); 459 if (r == 0 && 460 sshbuf_len(ssh->kex->server_version) != 0 && 461 sshbuf_len(ssh->kex->client_version) == 0) 462 r = _ssh_read_banner(ssh, ssh->kex->client_version); 463 } else { 464 if (sshbuf_len(ssh->kex->server_version) == 0) 465 r = _ssh_read_banner(ssh, ssh->kex->server_version); 466 if (r == 0 && 467 sshbuf_len(ssh->kex->server_version) != 0 && 468 sshbuf_len(ssh->kex->client_version) == 0) 469 r = _ssh_send_banner(ssh, ssh->kex->client_version); 470 } 471 if (r != 0) 472 return r; 473 /* start initial kex as soon as we have exchanged the banners */ 474 if (sshbuf_len(ssh->kex->server_version) != 0 && 475 sshbuf_len(ssh->kex->client_version) != 0) { 476 if ((r = _ssh_order_hostkeyalgs(ssh)) != 0 || 477 (r = kex_send_kexinit(ssh)) != 0) 478 return r; 479 } 480 return 0; 481 } 482 483 struct sshkey * 484 _ssh_host_public_key(int type, int nid, struct ssh *ssh) 485 { 486 struct key_entry *k; 487 488 debug3_f("need %d", type); 489 TAILQ_FOREACH(k, &ssh->public_keys, next) { 490 debug3_f("check %s", sshkey_type(k->key)); 491 if (k->key->type == type && 492 (type != KEY_ECDSA || k->key->ecdsa_nid == nid)) 493 return (k->key); 494 } 495 return (NULL); 496 } 497 498 struct sshkey * 499 _ssh_host_private_key(int type, int nid, struct ssh *ssh) 500 { 501 struct key_entry *k; 502 503 debug3_f("need %d", type); 504 TAILQ_FOREACH(k, &ssh->private_keys, next) { 505 debug3_f("check %s", sshkey_type(k->key)); 506 if (k->key->type == type && 507 (type != KEY_ECDSA || k->key->ecdsa_nid == nid)) 508 return (k->key); 509 } 510 return (NULL); 511 } 512 513 int 514 _ssh_verify_host_key(struct sshkey *hostkey, struct ssh *ssh) 515 { 516 struct key_entry *k; 517 518 debug3_f("need %s", sshkey_type(hostkey)); 519 TAILQ_FOREACH(k, &ssh->public_keys, next) { 520 debug3_f("check %s", sshkey_type(k->key)); 521 if (sshkey_equal_public(hostkey, k->key)) 522 return (0); /* ok */ 523 } 524 return (-1); /* failed */ 525 } 526 527 /* offer hostkey algorithms in kexinit depending on registered keys */ 528 int 529 _ssh_order_hostkeyalgs(struct ssh *ssh) 530 { 531 struct key_entry *k; 532 char *orig, *avail, *oavail = NULL, *alg, *replace = NULL; 533 char **proposal; 534 size_t maxlen; 535 int ktype, r; 536 537 /* XXX we de-serialize ssh->kex->my, modify it, and change it */ 538 if ((r = kex_buf2prop(ssh->kex->my, NULL, &proposal)) != 0) 539 return r; 540 orig = proposal[PROPOSAL_SERVER_HOST_KEY_ALGS]; 541 if ((oavail = avail = strdup(orig)) == NULL) { 542 r = SSH_ERR_ALLOC_FAIL; 543 goto out; 544 } 545 maxlen = strlen(avail) + 1; 546 if ((replace = calloc(1, maxlen)) == NULL) { 547 r = SSH_ERR_ALLOC_FAIL; 548 goto out; 549 } 550 *replace = '\0'; 551 while ((alg = strsep(&avail, ",")) && *alg != '\0') { 552 if ((ktype = sshkey_type_from_name(alg)) == KEY_UNSPEC) 553 continue; 554 TAILQ_FOREACH(k, &ssh->public_keys, next) { 555 if (k->key->type == ktype || 556 (sshkey_is_cert(k->key) && k->key->type == 557 sshkey_type_plain(ktype))) { 558 if (*replace != '\0') 559 strlcat(replace, ",", maxlen); 560 strlcat(replace, alg, maxlen); 561 break; 562 } 563 } 564 } 565 if (*replace != '\0') { 566 debug2_f("orig/%d %s", ssh->kex->server, orig); 567 debug2_f("replace/%d %s", ssh->kex->server, replace); 568 free(orig); 569 proposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = replace; 570 replace = NULL; /* owned by proposal */ 571 r = kex_prop2buf(ssh->kex->my, proposal); 572 } 573 out: 574 free(oavail); 575 free(replace); 576 kex_prop_free(proposal); 577 return r; 578 } 579 580 int 581 _ssh_host_key_sign(struct ssh *ssh, struct sshkey *privkey, 582 struct sshkey *pubkey, u_char **signature, size_t *slen, 583 const u_char *data, size_t dlen, const char *alg) 584 { 585 return sshkey_sign(privkey, signature, slen, data, dlen, 586 alg, NULL, NULL, ssh->compat); 587 } 588