1 /* $OpenBSD: ssh_api.c,v 1.32 2024/10/18 05:14:51 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 "dh.h" 29 #include "misc.h" 30 #include "ssh2.h" 31 #include "version.h" 32 #include "myproposal.h" 33 #include "ssherr.h" 34 #include "sshbuf.h" 35 36 #include <string.h> 37 38 int _ssh_exchange_banner(struct ssh *); 39 int _ssh_send_banner(struct ssh *, struct sshbuf *); 40 int _ssh_read_banner(struct ssh *, struct sshbuf *); 41 int _ssh_order_hostkeyalgs(struct ssh *); 42 int _ssh_verify_host_key(struct sshkey *, struct ssh *); 43 struct sshkey *_ssh_host_public_key(int, int, struct ssh *); 44 struct sshkey *_ssh_host_private_key(int, int, struct ssh *); 45 int _ssh_host_key_sign(struct ssh *, struct sshkey *, struct sshkey *, 46 u_char **, size_t *, const u_char *, size_t, const char *); 47 48 /* 49 * stubs for privsep calls in the server side implementation of kex. 50 */ 51 int mm_sshkey_sign(struct sshkey *, u_char **, u_int *, 52 const u_char *, u_int, const char *, const char *, const char *, u_int); 53 54 #ifdef WITH_OPENSSL 55 DH *mm_choose_dh(int, int, int); 56 #endif 57 58 int 59 mm_sshkey_sign(struct sshkey *key, u_char **sigp, u_int *lenp, 60 const u_char *data, u_int datalen, const char *alg, 61 const char *sk_provider, const char *sk_pin, u_int compat) 62 { 63 size_t slen = 0; 64 int ret; 65 66 ret = sshkey_sign(key, sigp, &slen, data, datalen, alg, 67 sk_provider, sk_pin, compat); 68 *lenp = slen; 69 return ret; 70 } 71 72 #ifdef WITH_OPENSSL 73 DH * 74 mm_choose_dh(int min, int nbits, int max) 75 { 76 return choose_dh(min, nbits, max); 77 } 78 #endif 79 80 /* API */ 81 82 int 83 ssh_init(struct ssh **sshp, int is_server, struct kex_params *kex_params) 84 { 85 char *myproposal[PROPOSAL_MAX] = { KEX_CLIENT }; 86 char *populated[PROPOSAL_MAX]; 87 struct ssh *ssh; 88 char **proposal; 89 static int called; 90 int r; 91 92 if (!called) { 93 #ifdef WITH_OPENSSL 94 OpenSSL_add_all_algorithms(); 95 #endif 96 called = 1; 97 } 98 99 if ((ssh = ssh_packet_set_connection(NULL, -1, -1)) == NULL) 100 return SSH_ERR_ALLOC_FAIL; 101 if (is_server) 102 ssh_packet_set_server(ssh); 103 104 /* Initialize key exchange */ 105 proposal = kex_params ? kex_params->proposal : myproposal; 106 kex_proposal_populate_entries(ssh, populated, 107 proposal[PROPOSAL_KEX_ALGS], 108 proposal[PROPOSAL_ENC_ALGS_CTOS], 109 proposal[PROPOSAL_MAC_ALGS_CTOS], 110 proposal[PROPOSAL_COMP_ALGS_CTOS], 111 proposal[PROPOSAL_SERVER_HOST_KEY_ALGS]); 112 r = kex_ready(ssh, populated); 113 kex_proposal_free_entries(populated); 114 if (r != 0) { 115 ssh_free(ssh); 116 return r; 117 } 118 119 ssh->kex->server = is_server; 120 if (is_server) { 121 #ifdef WITH_OPENSSL 122 ssh->kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_server; 123 ssh->kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_server; 124 ssh->kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_server; 125 ssh->kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_server; 126 ssh->kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_server; 127 ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_server; 128 ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_server; 129 ssh->kex->kex[KEX_ECDH_SHA2] = kex_gen_server; 130 #endif /* WITH_OPENSSL */ 131 ssh->kex->kex[KEX_C25519_SHA256] = kex_gen_server; 132 ssh->kex->kex[KEX_KEM_SNTRUP761X25519_SHA512] = kex_gen_server; 133 ssh->kex->kex[KEX_KEM_MLKEM768X25519_SHA256] = kex_gen_server; 134 ssh->kex->load_host_public_key=&_ssh_host_public_key; 135 ssh->kex->load_host_private_key=&_ssh_host_private_key; 136 ssh->kex->sign=&_ssh_host_key_sign; 137 } else { 138 #ifdef WITH_OPENSSL 139 ssh->kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_client; 140 ssh->kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_client; 141 ssh->kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_client; 142 ssh->kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_client; 143 ssh->kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_client; 144 ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_client; 145 ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_client; 146 ssh->kex->kex[KEX_ECDH_SHA2] = kex_gen_client; 147 #endif /* WITH_OPENSSL */ 148 ssh->kex->kex[KEX_C25519_SHA256] = kex_gen_client; 149 ssh->kex->kex[KEX_KEM_SNTRUP761X25519_SHA512] = kex_gen_client; 150 ssh->kex->kex[KEX_KEM_MLKEM768X25519_SHA256] = kex_gen_client; 151 ssh->kex->verify_host_key =&_ssh_verify_host_key; 152 } 153 *sshp = ssh; 154 return 0; 155 } 156 157 void 158 ssh_free(struct ssh *ssh) 159 { 160 struct key_entry *k; 161 162 if (ssh == NULL) 163 return; 164 165 /* 166 * we've only created the public keys variants in case we 167 * are a acting as a server. 168 */ 169 while ((k = TAILQ_FIRST(&ssh->public_keys)) != NULL) { 170 TAILQ_REMOVE(&ssh->public_keys, k, next); 171 if (ssh->kex && ssh->kex->server) 172 sshkey_free(k->key); 173 free(k); 174 } 175 while ((k = TAILQ_FIRST(&ssh->private_keys)) != NULL) { 176 TAILQ_REMOVE(&ssh->private_keys, k, next); 177 free(k); 178 } 179 ssh_packet_close(ssh); 180 free(ssh); 181 } 182 183 void 184 ssh_set_app_data(struct ssh *ssh, void *app_data) 185 { 186 ssh->app_data = app_data; 187 } 188 189 void * 190 ssh_get_app_data(struct ssh *ssh) 191 { 192 return ssh->app_data; 193 } 194 195 /* Returns < 0 on error, 0 otherwise */ 196 int 197 ssh_add_hostkey(struct ssh *ssh, struct sshkey *key) 198 { 199 struct sshkey *pubkey = NULL; 200 struct key_entry *k = NULL, *k_prv = NULL; 201 int r; 202 203 if (ssh->kex->server) { 204 if ((r = sshkey_from_private(key, &pubkey)) != 0) 205 return r; 206 if ((k = malloc(sizeof(*k))) == NULL || 207 (k_prv = malloc(sizeof(*k_prv))) == NULL) { 208 free(k); 209 sshkey_free(pubkey); 210 return SSH_ERR_ALLOC_FAIL; 211 } 212 k_prv->key = key; 213 TAILQ_INSERT_TAIL(&ssh->private_keys, k_prv, next); 214 215 /* add the public key, too */ 216 k->key = pubkey; 217 TAILQ_INSERT_TAIL(&ssh->public_keys, k, next); 218 r = 0; 219 } else { 220 if ((k = malloc(sizeof(*k))) == NULL) 221 return SSH_ERR_ALLOC_FAIL; 222 k->key = key; 223 TAILQ_INSERT_TAIL(&ssh->public_keys, k, next); 224 r = 0; 225 } 226 227 return r; 228 } 229 230 int 231 ssh_set_verify_host_key_callback(struct ssh *ssh, 232 int (*cb)(struct sshkey *, struct ssh *)) 233 { 234 if (cb == NULL || ssh->kex == NULL) 235 return SSH_ERR_INVALID_ARGUMENT; 236 237 ssh->kex->verify_host_key = cb; 238 239 return 0; 240 } 241 242 int 243 ssh_input_append(struct ssh *ssh, const u_char *data, size_t len) 244 { 245 return sshbuf_put(ssh_packet_get_input(ssh), data, len); 246 } 247 248 int 249 ssh_packet_next(struct ssh *ssh, u_char *typep) 250 { 251 int r; 252 u_int32_t seqnr; 253 u_char type; 254 255 /* 256 * Try to read a packet. Return SSH_MSG_NONE if no packet or not 257 * enough data. 258 */ 259 *typep = SSH_MSG_NONE; 260 if (sshbuf_len(ssh->kex->client_version) == 0 || 261 sshbuf_len(ssh->kex->server_version) == 0) 262 return _ssh_exchange_banner(ssh); 263 /* 264 * If we enough data and a dispatch function then 265 * call the function and get the next packet. 266 * Otherwise return the packet type to the caller so it 267 * can decide how to go on. 268 * 269 * We will only call the dispatch function for: 270 * 20-29 Algorithm negotiation 271 * 30-49 Key exchange method specific (numbers can be reused for 272 * different authentication methods) 273 */ 274 for (;;) { 275 if ((r = ssh_packet_read_poll2(ssh, &type, &seqnr)) != 0) 276 return r; 277 if (type > 0 && type < DISPATCH_MAX && 278 type >= SSH2_MSG_KEXINIT && type <= SSH2_MSG_TRANSPORT_MAX && 279 ssh->dispatch[type] != NULL) { 280 if ((r = (*ssh->dispatch[type])(type, seqnr, ssh)) != 0) 281 return r; 282 } else { 283 *typep = type; 284 return 0; 285 } 286 } 287 } 288 289 const u_char * 290 ssh_packet_payload(struct ssh *ssh, size_t *lenp) 291 { 292 return sshpkt_ptr(ssh, lenp); 293 } 294 295 int 296 ssh_packet_put(struct ssh *ssh, int type, const u_char *data, size_t len) 297 { 298 int r; 299 300 if ((r = sshpkt_start(ssh, type)) != 0 || 301 (r = sshpkt_put(ssh, data, len)) != 0 || 302 (r = sshpkt_send(ssh)) != 0) 303 return r; 304 return 0; 305 } 306 307 const u_char * 308 ssh_output_ptr(struct ssh *ssh, size_t *len) 309 { 310 struct sshbuf *output = ssh_packet_get_output(ssh); 311 312 *len = sshbuf_len(output); 313 return sshbuf_ptr(output); 314 } 315 316 int 317 ssh_output_consume(struct ssh *ssh, size_t len) 318 { 319 return sshbuf_consume(ssh_packet_get_output(ssh), len); 320 } 321 322 int 323 ssh_output_space(struct ssh *ssh, size_t len) 324 { 325 return (0 == sshbuf_check_reserve(ssh_packet_get_output(ssh), len)); 326 } 327 328 int 329 ssh_input_space(struct ssh *ssh, size_t len) 330 { 331 return (0 == sshbuf_check_reserve(ssh_packet_get_input(ssh), len)); 332 } 333 334 /* Read other side's version identification. */ 335 int 336 _ssh_read_banner(struct ssh *ssh, struct sshbuf *banner) 337 { 338 struct sshbuf *input = ssh_packet_get_input(ssh); 339 const char *mismatch = "Protocol mismatch.\r\n"; 340 const u_char *s = sshbuf_ptr(input); 341 u_char c; 342 char *cp = NULL, *remote_version = NULL; 343 int r = 0, remote_major, remote_minor, expect_nl; 344 size_t n, j; 345 346 for (j = n = 0;;) { 347 sshbuf_reset(banner); 348 expect_nl = 0; 349 for (;;) { 350 if (j >= sshbuf_len(input)) 351 return 0; /* insufficient data in input buf */ 352 c = s[j++]; 353 if (c == '\r') { 354 expect_nl = 1; 355 continue; 356 } 357 if (c == '\n') 358 break; 359 if (expect_nl) 360 goto bad; 361 if ((r = sshbuf_put_u8(banner, c)) != 0) 362 return r; 363 if (sshbuf_len(banner) > SSH_MAX_BANNER_LEN) 364 goto bad; 365 } 366 if (sshbuf_len(banner) >= 4 && 367 memcmp(sshbuf_ptr(banner), "SSH-", 4) == 0) 368 break; 369 debug_f("%.*s", (int)sshbuf_len(banner), 370 sshbuf_ptr(banner)); 371 /* Accept lines before banner only on client */ 372 if (ssh->kex->server || ++n > SSH_MAX_PRE_BANNER_LINES) { 373 bad: 374 if ((r = sshbuf_put(ssh_packet_get_output(ssh), 375 mismatch, strlen(mismatch))) != 0) 376 return r; 377 return SSH_ERR_NO_PROTOCOL_VERSION; 378 } 379 } 380 if ((r = sshbuf_consume(input, j)) != 0) 381 return r; 382 383 /* XXX remote version must be the same size as banner for sscanf */ 384 if ((cp = sshbuf_dup_string(banner)) == NULL || 385 (remote_version = calloc(1, sshbuf_len(banner))) == NULL) { 386 r = SSH_ERR_ALLOC_FAIL; 387 goto out; 388 } 389 390 /* 391 * Check that the versions match. In future this might accept 392 * several versions and set appropriate flags to handle them. 393 */ 394 if (sscanf(cp, "SSH-%d.%d-%[^\n]\n", 395 &remote_major, &remote_minor, remote_version) != 3) { 396 r = SSH_ERR_INVALID_FORMAT; 397 goto out; 398 } 399 debug("Remote protocol version %d.%d, remote software version %.100s", 400 remote_major, remote_minor, remote_version); 401 402 compat_banner(ssh, remote_version); 403 if (remote_major == 1 && remote_minor == 99) { 404 remote_major = 2; 405 remote_minor = 0; 406 } 407 if (remote_major != 2) 408 r = SSH_ERR_PROTOCOL_MISMATCH; 409 410 debug("Remote version string %.100s", cp); 411 out: 412 free(cp); 413 free(remote_version); 414 return r; 415 } 416 417 /* Send our own protocol version identification. */ 418 int 419 _ssh_send_banner(struct ssh *ssh, struct sshbuf *banner) 420 { 421 char *cp; 422 int r; 423 424 if ((r = sshbuf_putf(banner, "SSH-2.0-%.100s\r\n", SSH_VERSION)) != 0) 425 return r; 426 if ((r = sshbuf_putb(ssh_packet_get_output(ssh), banner)) != 0) 427 return r; 428 /* Remove trailing \r\n */ 429 if ((r = sshbuf_consume_end(banner, 2)) != 0) 430 return r; 431 if ((cp = sshbuf_dup_string(banner)) == NULL) 432 return SSH_ERR_ALLOC_FAIL; 433 debug("Local version string %.100s", cp); 434 free(cp); 435 return 0; 436 } 437 438 int 439 _ssh_exchange_banner(struct ssh *ssh) 440 { 441 struct kex *kex = ssh->kex; 442 int r; 443 444 /* 445 * if _ssh_read_banner() cannot parse a full version string 446 * it will return NULL and we end up calling it again. 447 */ 448 449 r = 0; 450 if (kex->server) { 451 if (sshbuf_len(ssh->kex->server_version) == 0) 452 r = _ssh_send_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_read_banner(ssh, ssh->kex->client_version); 457 } else { 458 if (sshbuf_len(ssh->kex->server_version) == 0) 459 r = _ssh_read_banner(ssh, ssh->kex->server_version); 460 if (r == 0 && 461 sshbuf_len(ssh->kex->server_version) != 0 && 462 sshbuf_len(ssh->kex->client_version) == 0) 463 r = _ssh_send_banner(ssh, ssh->kex->client_version); 464 } 465 if (r != 0) 466 return r; 467 /* start initial kex as soon as we have exchanged the banners */ 468 if (sshbuf_len(ssh->kex->server_version) != 0 && 469 sshbuf_len(ssh->kex->client_version) != 0) { 470 if ((r = _ssh_order_hostkeyalgs(ssh)) != 0 || 471 (r = kex_send_kexinit(ssh)) != 0) 472 return r; 473 } 474 return 0; 475 } 476 477 struct sshkey * 478 _ssh_host_public_key(int type, int nid, struct ssh *ssh) 479 { 480 struct key_entry *k; 481 482 debug3_f("need %d", type); 483 TAILQ_FOREACH(k, &ssh->public_keys, next) { 484 debug3_f("check %s", sshkey_type(k->key)); 485 if (k->key->type == type && 486 (type != KEY_ECDSA || k->key->ecdsa_nid == nid)) 487 return (k->key); 488 } 489 return (NULL); 490 } 491 492 struct sshkey * 493 _ssh_host_private_key(int type, int nid, struct ssh *ssh) 494 { 495 struct key_entry *k; 496 497 debug3_f("need %d", type); 498 TAILQ_FOREACH(k, &ssh->private_keys, next) { 499 debug3_f("check %s", sshkey_type(k->key)); 500 if (k->key->type == type && 501 (type != KEY_ECDSA || k->key->ecdsa_nid == nid)) 502 return (k->key); 503 } 504 return (NULL); 505 } 506 507 int 508 _ssh_verify_host_key(struct sshkey *hostkey, struct ssh *ssh) 509 { 510 struct key_entry *k; 511 512 debug3_f("need %s", sshkey_type(hostkey)); 513 TAILQ_FOREACH(k, &ssh->public_keys, next) { 514 debug3_f("check %s", sshkey_type(k->key)); 515 if (sshkey_equal_public(hostkey, k->key)) 516 return (0); /* ok */ 517 } 518 return (-1); /* failed */ 519 } 520 521 /* offer hostkey algorithms in kexinit depending on registered keys */ 522 int 523 _ssh_order_hostkeyalgs(struct ssh *ssh) 524 { 525 struct key_entry *k; 526 char *orig, *avail, *oavail = NULL, *alg, *replace = NULL; 527 char **proposal; 528 size_t maxlen; 529 int ktype, nid, r; 530 531 /* XXX we de-serialize ssh->kex->my, modify it, and change it */ 532 if ((r = kex_buf2prop(ssh->kex->my, NULL, &proposal)) != 0) 533 return r; 534 orig = proposal[PROPOSAL_SERVER_HOST_KEY_ALGS]; 535 if ((oavail = avail = strdup(orig)) == NULL) { 536 r = SSH_ERR_ALLOC_FAIL; 537 goto out; 538 } 539 maxlen = strlen(avail) + 1; 540 if ((replace = calloc(1, maxlen)) == NULL) { 541 r = SSH_ERR_ALLOC_FAIL; 542 goto out; 543 } 544 *replace = '\0'; 545 while ((alg = strsep(&avail, ",")) && *alg != '\0') { 546 if ((ktype = sshkey_type_from_name(alg)) == KEY_UNSPEC) 547 continue; 548 nid = sshkey_ecdsa_nid_from_name(alg); 549 TAILQ_FOREACH(k, &ssh->public_keys, next) { 550 if (k->key->type != ktype && 551 (!sshkey_is_cert(k->key) || 552 k->key->type != sshkey_type_plain(ktype))) 553 continue; 554 if (sshkey_type_plain(k->key->type) == KEY_ECDSA && 555 k->key->ecdsa_nid != nid) 556 continue; 557 /* Candidate */ 558 if (*replace != '\0') 559 strlcat(replace, ",", maxlen); 560 strlcat(replace, alg, maxlen); 561 break; 562 } 563 } 564 if (*replace != '\0') { 565 debug2_f("orig/%d %s", ssh->kex->server, orig); 566 debug2_f("replace/%d %s", ssh->kex->server, replace); 567 free(orig); 568 proposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = replace; 569 replace = NULL; /* owned by proposal */ 570 r = kex_prop2buf(ssh->kex->my, proposal); 571 } 572 out: 573 free(oavail); 574 free(replace); 575 kex_prop_free(proposal); 576 return r; 577 } 578 579 int 580 _ssh_host_key_sign(struct ssh *ssh, struct sshkey *privkey, 581 struct sshkey *pubkey, u_char **signature, size_t *slen, 582 const u_char *data, size_t dlen, const char *alg) 583 { 584 return sshkey_sign(privkey, signature, slen, data, dlen, 585 alg, NULL, NULL, ssh->compat); 586 } 587