1 /* $NetBSD: ssh_api.c,v 1.18 2024/09/24 21:32:19 christos Exp $ */ 2 /* $OpenBSD: ssh_api.c,v 1.31 2024/09/09 02:39:57 djm Exp $ */ 3 4 /* 5 * Copyright (c) 2012 Markus Friedl. All rights reserved. 6 * 7 * Permission to use, copy, modify, and distribute this software for any 8 * purpose with or without fee is hereby granted, provided that the above 9 * copyright notice and this permission notice appear in all copies. 10 * 11 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 12 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 13 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 14 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 15 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 16 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 17 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 18 */ 19 20 #include "includes.h" 21 __RCSID("$NetBSD: ssh_api.c,v 1.18 2024/09/24 21:32:19 christos Exp $"); 22 23 #include <sys/types.h> 24 25 #include <stdio.h> 26 #include <stdlib.h> 27 28 #include "ssh_api.h" 29 #include "compat.h" 30 #include "log.h" 31 #include "authfile.h" 32 #include "sshkey.h" 33 #include "dh.h" 34 #include "misc.h" 35 #include "ssh2.h" 36 #include "version.h" 37 #include "myproposal.h" 38 #include "ssherr.h" 39 #include "sshbuf.h" 40 41 #include <string.h> 42 43 int _ssh_exchange_banner(struct ssh *); 44 int _ssh_send_banner(struct ssh *, struct sshbuf *); 45 int _ssh_read_banner(struct ssh *, struct sshbuf *); 46 int _ssh_order_hostkeyalgs(struct ssh *); 47 int _ssh_verify_host_key(struct sshkey *, struct ssh *); 48 struct sshkey *_ssh_host_public_key(int, int, struct ssh *); 49 struct sshkey *_ssh_host_private_key(int, int, struct ssh *); 50 int _ssh_host_key_sign(struct ssh *, struct sshkey *, struct sshkey *, 51 u_char **, size_t *, const u_char *, size_t, const char *); 52 53 /* 54 * stubs for privsep calls in the server side implementation of kex. 55 */ 56 int mm_sshkey_sign(struct sshkey *, u_char **, u_int *, 57 const u_char *, u_int, const char *, const char *, const char *, u_int); 58 59 #ifdef WITH_OPENSSL 60 DH *mm_choose_dh(int, int, int); 61 #endif 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 size_t slen = 0; 69 int ret; 70 71 ret = sshkey_sign(key, sigp, &slen, data, datalen, alg, 72 sk_provider, sk_pin, compat); 73 *lenp = slen; 74 return ret; 75 } 76 77 #ifdef WITH_OPENSSL 78 DH * 79 mm_choose_dh(int min, int nbits, int max) 80 { 81 return choose_dh(min, nbits, max); 82 } 83 #endif 84 85 /* API */ 86 87 int 88 ssh_init(struct ssh **sshp, int is_server, struct kex_params *kex_params) 89 { 90 const char *myproposal[PROPOSAL_MAX] = { KEX_CLIENT }; 91 char *populated[PROPOSAL_MAX]; 92 struct ssh *ssh; 93 const char **proposal; 94 static int called; 95 int r; 96 97 if (!called) { 98 #ifdef WITH_OPENSSL 99 OpenSSL_add_all_algorithms(); 100 #endif 101 called = 1; 102 } 103 104 if ((ssh = ssh_packet_set_connection(NULL, -1, -1)) == NULL) 105 return SSH_ERR_ALLOC_FAIL; 106 if (is_server) 107 ssh_packet_set_server(ssh); 108 109 /* Initialize key exchange */ 110 proposal = kex_params ? __UNCONST(kex_params->proposal) : myproposal; 111 kex_proposal_populate_entries(ssh, populated, 112 proposal[PROPOSAL_KEX_ALGS], 113 proposal[PROPOSAL_ENC_ALGS_CTOS], 114 proposal[PROPOSAL_MAC_ALGS_CTOS], 115 proposal[PROPOSAL_COMP_ALGS_CTOS], 116 proposal[PROPOSAL_SERVER_HOST_KEY_ALGS]); 117 r = kex_ready(ssh, populated); 118 kex_proposal_free_entries(populated); 119 if (r != 0) { 120 ssh_free(ssh); 121 return r; 122 } 123 124 ssh->kex->server = is_server; 125 if (is_server) { 126 #ifdef WITH_OPENSSL 127 ssh->kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_server; 128 ssh->kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_server; 129 ssh->kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_server; 130 ssh->kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_server; 131 ssh->kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_server; 132 ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_server; 133 ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_server; 134 ssh->kex->kex[KEX_ECDH_SHA2] = kex_gen_server; 135 #endif /* WITH_OPENSSL */ 136 ssh->kex->kex[KEX_C25519_SHA256] = kex_gen_server; 137 ssh->kex->kex[KEX_KEM_SNTRUP761X25519_SHA512] = kex_gen_server; 138 ssh->kex->kex[KEX_KEM_MLKEM768X25519_SHA256] = kex_gen_server; 139 ssh->kex->load_host_public_key=&_ssh_host_public_key; 140 ssh->kex->load_host_private_key=&_ssh_host_private_key; 141 ssh->kex->sign=&_ssh_host_key_sign; 142 } else { 143 #ifdef WITH_OPENSSL 144 ssh->kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_client; 145 ssh->kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_client; 146 ssh->kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_client; 147 ssh->kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_client; 148 ssh->kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_client; 149 ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_client; 150 ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_client; 151 ssh->kex->kex[KEX_ECDH_SHA2] = kex_gen_client; 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->kex[KEX_KEM_MLKEM768X25519_SHA256] = kex_gen_client; 156 ssh->kex->verify_host_key =&_ssh_verify_host_key; 157 } 158 *sshp = ssh; 159 return 0; 160 } 161 162 void 163 ssh_free(struct ssh *ssh) 164 { 165 struct key_entry *k; 166 167 if (ssh == NULL) 168 return; 169 170 /* 171 * we've only created the public keys variants in case we 172 * are a acting as a server. 173 */ 174 while ((k = TAILQ_FIRST(&ssh->public_keys)) != NULL) { 175 TAILQ_REMOVE(&ssh->public_keys, k, next); 176 if (ssh->kex && ssh->kex->server) 177 sshkey_free(k->key); 178 free(k); 179 } 180 while ((k = TAILQ_FIRST(&ssh->private_keys)) != NULL) { 181 TAILQ_REMOVE(&ssh->private_keys, k, next); 182 free(k); 183 } 184 ssh_packet_close(ssh); 185 free(ssh); 186 } 187 188 void 189 ssh_set_app_data(struct ssh *ssh, void *app_data) 190 { 191 ssh->app_data = app_data; 192 } 193 194 void * 195 ssh_get_app_data(struct ssh *ssh) 196 { 197 return ssh->app_data; 198 } 199 200 /* Returns < 0 on error, 0 otherwise */ 201 int 202 ssh_add_hostkey(struct ssh *ssh, struct sshkey *key) 203 { 204 struct sshkey *pubkey = NULL; 205 struct key_entry *k = NULL, *k_prv = NULL; 206 int r; 207 208 if (ssh->kex->server) { 209 if ((r = sshkey_from_private(key, &pubkey)) != 0) 210 return r; 211 if ((k = malloc(sizeof(*k))) == NULL || 212 (k_prv = malloc(sizeof(*k_prv))) == NULL) { 213 free(k); 214 sshkey_free(pubkey); 215 return SSH_ERR_ALLOC_FAIL; 216 } 217 k_prv->key = key; 218 TAILQ_INSERT_TAIL(&ssh->private_keys, k_prv, next); 219 220 /* add the public key, too */ 221 k->key = pubkey; 222 TAILQ_INSERT_TAIL(&ssh->public_keys, k, next); 223 r = 0; 224 } else { 225 if ((k = malloc(sizeof(*k))) == NULL) 226 return SSH_ERR_ALLOC_FAIL; 227 k->key = key; 228 TAILQ_INSERT_TAIL(&ssh->public_keys, k, next); 229 r = 0; 230 } 231 232 return r; 233 } 234 235 int 236 ssh_set_verify_host_key_callback(struct ssh *ssh, 237 int (*cb)(struct sshkey *, struct ssh *)) 238 { 239 if (cb == NULL || ssh->kex == NULL) 240 return SSH_ERR_INVALID_ARGUMENT; 241 242 ssh->kex->verify_host_key = cb; 243 244 return 0; 245 } 246 247 int 248 ssh_input_append(struct ssh *ssh, const u_char *data, size_t len) 249 { 250 return sshbuf_put(ssh_packet_get_input(ssh), data, len); 251 } 252 253 int 254 ssh_packet_next(struct ssh *ssh, u_char *typep) 255 { 256 int r; 257 u_int32_t seqnr; 258 u_char type; 259 260 /* 261 * Try to read a packet. Return SSH_MSG_NONE if no packet or not 262 * enough data. 263 */ 264 *typep = SSH_MSG_NONE; 265 if (sshbuf_len(ssh->kex->client_version) == 0 || 266 sshbuf_len(ssh->kex->server_version) == 0) 267 return _ssh_exchange_banner(ssh); 268 /* 269 * If we enough data and a dispatch function then 270 * call the function and get the next packet. 271 * Otherwise return the packet type to the caller so it 272 * can decide how to go on. 273 * 274 * We will only call the dispatch function for: 275 * 20-29 Algorithm negotiation 276 * 30-49 Key exchange method specific (numbers can be reused for 277 * different authentication methods) 278 */ 279 for (;;) { 280 if ((r = ssh_packet_read_poll2(ssh, &type, &seqnr)) != 0) 281 return r; 282 if (type > 0 && type < DISPATCH_MAX && 283 type >= SSH2_MSG_KEXINIT && type <= SSH2_MSG_TRANSPORT_MAX && 284 ssh->dispatch[type] != NULL) { 285 if ((r = (*ssh->dispatch[type])(type, seqnr, ssh)) != 0) 286 return r; 287 } else { 288 *typep = type; 289 return 0; 290 } 291 } 292 } 293 294 const u_char * 295 ssh_packet_payload(struct ssh *ssh, size_t *lenp) 296 { 297 return sshpkt_ptr(ssh, lenp); 298 } 299 300 int 301 ssh_packet_put(struct ssh *ssh, int type, const u_char *data, size_t len) 302 { 303 int r; 304 305 if ((r = sshpkt_start(ssh, type)) != 0 || 306 (r = sshpkt_put(ssh, data, len)) != 0 || 307 (r = sshpkt_send(ssh)) != 0) 308 return r; 309 return 0; 310 } 311 312 const u_char * 313 ssh_output_ptr(struct ssh *ssh, size_t *len) 314 { 315 struct sshbuf *output = ssh_packet_get_output(ssh); 316 317 *len = sshbuf_len(output); 318 return sshbuf_ptr(output); 319 } 320 321 int 322 ssh_output_consume(struct ssh *ssh, size_t len) 323 { 324 return sshbuf_consume(ssh_packet_get_output(ssh), len); 325 } 326 327 int 328 ssh_output_space(struct ssh *ssh, size_t len) 329 { 330 return (0 == sshbuf_check_reserve(ssh_packet_get_output(ssh), len)); 331 } 332 333 int 334 ssh_input_space(struct ssh *ssh, size_t len) 335 { 336 return (0 == sshbuf_check_reserve(ssh_packet_get_input(ssh), len)); 337 } 338 339 /* Read other side's version identification. */ 340 int 341 _ssh_read_banner(struct ssh *ssh, struct sshbuf *banner) 342 { 343 struct sshbuf *input = ssh_packet_get_input(ssh); 344 const char *mismatch = "Protocol mismatch.\r\n"; 345 const u_char *s = sshbuf_ptr(input); 346 u_char c; 347 char *cp = NULL, *remote_version = NULL; 348 int r = 0, remote_major, remote_minor, expect_nl; 349 size_t n, j; 350 351 for (j = n = 0;;) { 352 sshbuf_reset(banner); 353 expect_nl = 0; 354 for (;;) { 355 if (j >= sshbuf_len(input)) 356 return 0; /* insufficient data in input buf */ 357 c = s[j++]; 358 if (c == '\r') { 359 expect_nl = 1; 360 continue; 361 } 362 if (c == '\n') 363 break; 364 if (expect_nl) 365 goto bad; 366 if ((r = sshbuf_put_u8(banner, c)) != 0) 367 return r; 368 if (sshbuf_len(banner) > SSH_MAX_BANNER_LEN) 369 goto bad; 370 } 371 if (sshbuf_len(banner) >= 4 && 372 memcmp(sshbuf_ptr(banner), "SSH-", 4) == 0) 373 break; 374 debug_f("%.*s", (int)sshbuf_len(banner), 375 sshbuf_ptr(banner)); 376 /* Accept lines before banner only on client */ 377 if (ssh->kex->server || ++n > SSH_MAX_PRE_BANNER_LINES) { 378 bad: 379 if ((r = sshbuf_put(ssh_packet_get_output(ssh), 380 mismatch, strlen(mismatch))) != 0) 381 return r; 382 return SSH_ERR_NO_PROTOCOL_VERSION; 383 } 384 } 385 if ((r = sshbuf_consume(input, j)) != 0) 386 return r; 387 388 /* XXX remote version must be the same size as banner for sscanf */ 389 if ((cp = sshbuf_dup_string(banner)) == NULL || 390 (remote_version = calloc(1, sshbuf_len(banner))) == NULL) { 391 r = SSH_ERR_ALLOC_FAIL; 392 goto out; 393 } 394 395 /* 396 * Check that the versions match. In future this might accept 397 * several versions and set appropriate flags to handle them. 398 */ 399 if (sscanf(cp, "SSH-%d.%d-%[^\n]\n", 400 &remote_major, &remote_minor, remote_version) != 3) { 401 r = SSH_ERR_INVALID_FORMAT; 402 goto out; 403 } 404 debug("Remote protocol version %d.%d, remote software version %.100s", 405 remote_major, remote_minor, remote_version); 406 407 compat_banner(ssh, remote_version); 408 if (remote_major == 1 && remote_minor == 99) { 409 remote_major = 2; 410 remote_minor = 0; 411 } 412 if (remote_major != 2) 413 r = SSH_ERR_PROTOCOL_MISMATCH; 414 415 debug("Remote version string %.100s", cp); 416 out: 417 free(cp); 418 free(remote_version); 419 return r; 420 } 421 422 /* Send our own protocol version identification. */ 423 int 424 _ssh_send_banner(struct ssh *ssh, struct sshbuf *banner) 425 { 426 char *cp; 427 int r; 428 429 if ((r = sshbuf_putf(banner, "SSH-2.0-%.100s\r\n", SSH_VERSION)) != 0) 430 return r; 431 if ((r = sshbuf_putb(ssh_packet_get_output(ssh), banner)) != 0) 432 return r; 433 /* Remove trailing \r\n */ 434 if ((r = sshbuf_consume_end(banner, 2)) != 0) 435 return r; 436 if ((cp = sshbuf_dup_string(banner)) == NULL) 437 return SSH_ERR_ALLOC_FAIL; 438 debug("Local version string %.100s", cp); 439 free(cp); 440 return 0; 441 } 442 443 int 444 _ssh_exchange_banner(struct ssh *ssh) 445 { 446 struct kex *kex = ssh->kex; 447 int r; 448 449 /* 450 * if _ssh_read_banner() cannot parse a full version string 451 * it will return NULL and we end up calling it again. 452 */ 453 454 r = 0; 455 if (kex->server) { 456 if (sshbuf_len(ssh->kex->server_version) == 0) 457 r = _ssh_send_banner(ssh, ssh->kex->server_version); 458 if (r == 0 && 459 sshbuf_len(ssh->kex->server_version) != 0 && 460 sshbuf_len(ssh->kex->client_version) == 0) 461 r = _ssh_read_banner(ssh, ssh->kex->client_version); 462 } else { 463 if (sshbuf_len(ssh->kex->server_version) == 0) 464 r = _ssh_read_banner(ssh, ssh->kex->server_version); 465 if (r == 0 && 466 sshbuf_len(ssh->kex->server_version) != 0 && 467 sshbuf_len(ssh->kex->client_version) == 0) 468 r = _ssh_send_banner(ssh, ssh->kex->client_version); 469 } 470 if (r != 0) 471 return r; 472 /* start initial kex as soon as we have exchanged the banners */ 473 if (sshbuf_len(ssh->kex->server_version) != 0 && 474 sshbuf_len(ssh->kex->client_version) != 0) { 475 if ((r = _ssh_order_hostkeyalgs(ssh)) != 0 || 476 (r = kex_send_kexinit(ssh)) != 0) 477 return r; 478 } 479 return 0; 480 } 481 482 struct sshkey * 483 _ssh_host_public_key(int type, int nid, struct ssh *ssh) 484 { 485 struct key_entry *k; 486 487 debug3_f("need %d", type); 488 TAILQ_FOREACH(k, &ssh->public_keys, next) { 489 debug3_f("check %s", sshkey_type(k->key)); 490 if (k->key->type == type && 491 (type != KEY_ECDSA || k->key->ecdsa_nid == nid)) 492 return (k->key); 493 } 494 return (NULL); 495 } 496 497 struct sshkey * 498 _ssh_host_private_key(int type, int nid, struct ssh *ssh) 499 { 500 struct key_entry *k; 501 502 debug3_f("need %d", type); 503 TAILQ_FOREACH(k, &ssh->private_keys, next) { 504 debug3_f("check %s", sshkey_type(k->key)); 505 if (k->key->type == type && 506 (type != KEY_ECDSA || k->key->ecdsa_nid == nid)) 507 return (k->key); 508 } 509 return (NULL); 510 } 511 512 int 513 _ssh_verify_host_key(struct sshkey *hostkey, struct ssh *ssh) 514 { 515 struct key_entry *k; 516 517 debug3_f("need %s", sshkey_type(hostkey)); 518 TAILQ_FOREACH(k, &ssh->public_keys, next) { 519 debug3_f("check %s", sshkey_type(k->key)); 520 if (sshkey_equal_public(hostkey, k->key)) 521 return (0); /* ok */ 522 } 523 return (-1); /* failed */ 524 } 525 526 /* offer hostkey algorithms in kexinit depending on registered keys */ 527 int 528 _ssh_order_hostkeyalgs(struct ssh *ssh) 529 { 530 struct key_entry *k; 531 char *orig, *avail, *oavail = NULL, *alg, *replace = NULL; 532 char **proposal; 533 size_t maxlen; 534 int ktype, r; 535 536 /* XXX we de-serialize ssh->kex->my, modify it, and change it */ 537 if ((r = kex_buf2prop(ssh->kex->my, NULL, &proposal)) != 0) 538 return r; 539 orig = proposal[PROPOSAL_SERVER_HOST_KEY_ALGS]; 540 if ((oavail = avail = strdup(orig)) == NULL) { 541 r = SSH_ERR_ALLOC_FAIL; 542 goto out; 543 } 544 maxlen = strlen(avail) + 1; 545 if ((replace = calloc(1, maxlen)) == NULL) { 546 r = SSH_ERR_ALLOC_FAIL; 547 goto out; 548 } 549 *replace = '\0'; 550 while ((alg = strsep(&avail, ",")) && *alg != '\0') { 551 if ((ktype = sshkey_type_from_name(alg)) == KEY_UNSPEC) 552 continue; 553 TAILQ_FOREACH(k, &ssh->public_keys, next) { 554 if (k->key->type == ktype || 555 (sshkey_is_cert(k->key) && k->key->type == 556 sshkey_type_plain(ktype))) { 557 if (*replace != '\0') 558 strlcat(replace, ",", maxlen); 559 strlcat(replace, alg, maxlen); 560 break; 561 } 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