1 /* $NetBSD: ssh_api.c,v 1.10 2020/02/27 00:24:40 christos Exp $ */ 2 /* $OpenBSD: ssh_api.c,v 1.19 2019/10/31 21:23:19 djm Exp $ */ 3 /* 4 * Copyright (c) 2012 Markus Friedl. All rights reserved. 5 * 6 * Permission to use, copy, modify, and distribute this software for any 7 * purpose with or without fee is hereby granted, provided that the above 8 * copyright notice and this permission notice appear in all copies. 9 * 10 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 11 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 12 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 13 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 14 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 15 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 16 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 17 */ 18 19 #include "includes.h" 20 __RCSID("$NetBSD: ssh_api.c,v 1.10 2020/02/27 00:24:40 christos Exp $"); 21 22 #include <sys/types.h> 23 24 #include <stdio.h> 25 #include <stdlib.h> 26 27 #include "ssh_api.h" 28 #include "compat.h" 29 #include "log.h" 30 #include "authfile.h" 31 #include "sshkey.h" 32 #include "misc.h" 33 #include "ssh2.h" 34 #include "version.h" 35 #include "myproposal.h" 36 #include "ssherr.h" 37 #include "sshbuf.h" 38 39 #include <string.h> 40 41 int _ssh_exchange_banner(struct ssh *); 42 int _ssh_send_banner(struct ssh *, struct sshbuf *); 43 int _ssh_read_banner(struct ssh *, struct sshbuf *); 44 int _ssh_order_hostkeyalgs(struct ssh *); 45 int _ssh_verify_host_key(struct sshkey *, struct ssh *); 46 struct sshkey *_ssh_host_public_key(int, int, struct ssh *); 47 struct sshkey *_ssh_host_private_key(int, int, struct ssh *); 48 int _ssh_host_key_sign(struct ssh *, struct sshkey *, struct sshkey *, 49 u_char **, size_t *, const u_char *, size_t, const char *); 50 51 /* 52 * stubs for the server side implementation of kex. 53 * disable privsep so our stubs will never be called. 54 */ 55 int use_privsep = 0; 56 int mm_sshkey_sign(struct sshkey *, u_char **, u_int *, 57 const u_char *, u_int, const char *, const char *, u_int); 58 59 #ifdef WITH_OPENSSL 60 DH *mm_choose_dh(int, int, int); 61 #endif 62 63 /* Define these two variables here so that they are part of the library */ 64 u_char *session_id2 = NULL; 65 u_int session_id2_len = 0; 66 67 int 68 mm_sshkey_sign(struct sshkey *key, u_char **sigp, u_int *lenp, 69 const u_char *data, u_int datalen, const char *alg, const char *sk_provider, 70 u_int compat) 71 { 72 return (-1); 73 } 74 75 #ifdef WITH_OPENSSL 76 DH * 77 mm_choose_dh(int min, int nbits, int max) 78 { 79 return (NULL); 80 } 81 #endif 82 83 /* API */ 84 85 int 86 ssh_init(struct ssh **sshp, int is_server, struct kex_params *kex_params) 87 { 88 const char *myproposal[PROPOSAL_MAX] = { KEX_CLIENT }; 89 struct ssh *ssh; 90 const char **proposal; 91 static int called; 92 int r; 93 94 if (!called) { 95 #ifdef WITH_OPENSSL 96 OpenSSL_add_all_algorithms(); 97 #endif 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 ? __UNCONST(kex_params->proposal) : myproposal; 108 if ((r = kex_ready(ssh, proposal)) != 0) { 109 ssh_free(ssh); 110 return r; 111 } 112 ssh->kex->server = is_server; 113 if (is_server) { 114 #ifdef WITH_OPENSSL 115 ssh->kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_server; 116 ssh->kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_server; 117 ssh->kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_server; 118 ssh->kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_server; 119 ssh->kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_server; 120 ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_server; 121 ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_server; 122 ssh->kex->kex[KEX_ECDH_SHA2] = kex_gen_server; 123 #endif /* WITH_OPENSSL */ 124 ssh->kex->kex[KEX_C25519_SHA256] = kex_gen_server; 125 ssh->kex->kex[KEX_KEM_SNTRUP4591761X25519_SHA512] = kex_gen_server; 126 ssh->kex->load_host_public_key=&_ssh_host_public_key; 127 ssh->kex->load_host_private_key=&_ssh_host_private_key; 128 ssh->kex->sign=&_ssh_host_key_sign; 129 } else { 130 #ifdef WITH_OPENSSL 131 ssh->kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_client; 132 ssh->kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_client; 133 ssh->kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_client; 134 ssh->kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_client; 135 ssh->kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_client; 136 ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_client; 137 ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_client; 138 ssh->kex->kex[KEX_ECDH_SHA2] = kex_gen_client; 139 #endif /* WITH_OPENSSL */ 140 ssh->kex->kex[KEX_C25519_SHA256] = kex_gen_client; 141 ssh->kex->kex[KEX_KEM_SNTRUP4591761X25519_SHA512] = kex_gen_client; 142 ssh->kex->verify_host_key =&_ssh_verify_host_key; 143 } 144 *sshp = ssh; 145 return 0; 146 } 147 148 void 149 ssh_free(struct ssh *ssh) 150 { 151 struct key_entry *k; 152 153 ssh_packet_close(ssh); 154 /* 155 * we've only created the public keys variants in case we 156 * are a acting as a server. 157 */ 158 while ((k = TAILQ_FIRST(&ssh->public_keys)) != NULL) { 159 TAILQ_REMOVE(&ssh->public_keys, k, next); 160 if (ssh->kex && ssh->kex->server) 161 sshkey_free(k->key); 162 free(k); 163 } 164 while ((k = TAILQ_FIRST(&ssh->private_keys)) != NULL) { 165 TAILQ_REMOVE(&ssh->private_keys, k, next); 166 free(k); 167 } 168 if (ssh->kex) 169 kex_free(ssh->kex); 170 free(ssh); 171 } 172 173 void 174 ssh_set_app_data(struct ssh *ssh, void *app_data) 175 { 176 ssh->app_data = app_data; 177 } 178 179 void * 180 ssh_get_app_data(struct ssh *ssh) 181 { 182 return ssh->app_data; 183 } 184 185 /* Returns < 0 on error, 0 otherwise */ 186 int 187 ssh_add_hostkey(struct ssh *ssh, struct sshkey *key) 188 { 189 struct sshkey *pubkey = NULL; 190 struct key_entry *k = NULL, *k_prv = NULL; 191 int r; 192 193 if (ssh->kex->server) { 194 if ((r = sshkey_from_private(key, &pubkey)) != 0) 195 return r; 196 if ((k = malloc(sizeof(*k))) == NULL || 197 (k_prv = malloc(sizeof(*k_prv))) == NULL) { 198 free(k); 199 sshkey_free(pubkey); 200 return SSH_ERR_ALLOC_FAIL; 201 } 202 k_prv->key = key; 203 TAILQ_INSERT_TAIL(&ssh->private_keys, k_prv, next); 204 205 /* add the public key, too */ 206 k->key = pubkey; 207 TAILQ_INSERT_TAIL(&ssh->public_keys, k, next); 208 r = 0; 209 } else { 210 if ((k = malloc(sizeof(*k))) == NULL) 211 return SSH_ERR_ALLOC_FAIL; 212 k->key = key; 213 TAILQ_INSERT_TAIL(&ssh->public_keys, k, next); 214 r = 0; 215 } 216 217 return r; 218 } 219 220 int 221 ssh_set_verify_host_key_callback(struct ssh *ssh, 222 int (*cb)(struct sshkey *, struct ssh *)) 223 { 224 if (cb == NULL || ssh->kex == NULL) 225 return SSH_ERR_INVALID_ARGUMENT; 226 227 ssh->kex->verify_host_key = cb; 228 229 return 0; 230 } 231 232 int 233 ssh_input_append(struct ssh *ssh, const u_char *data, size_t len) 234 { 235 return sshbuf_put(ssh_packet_get_input(ssh), data, len); 236 } 237 238 int 239 ssh_packet_next(struct ssh *ssh, u_char *typep) 240 { 241 int r; 242 u_int32_t seqnr; 243 u_char type; 244 245 /* 246 * Try to read a packet. Return SSH_MSG_NONE if no packet or not 247 * enough data. 248 */ 249 *typep = SSH_MSG_NONE; 250 if (sshbuf_len(ssh->kex->client_version) == 0 || 251 sshbuf_len(ssh->kex->server_version) == 0) 252 return _ssh_exchange_banner(ssh); 253 /* 254 * If we enough data and a dispatch function then 255 * call the function and get the next packet. 256 * Otherwise return the packet type to the caller so it 257 * can decide how to go on. 258 * 259 * We will only call the dispatch function for: 260 * 20-29 Algorithm negotiation 261 * 30-49 Key exchange method specific (numbers can be reused for 262 * different authentication methods) 263 */ 264 for (;;) { 265 if ((r = ssh_packet_read_poll2(ssh, &type, &seqnr)) != 0) 266 return r; 267 if (type > 0 && type < DISPATCH_MAX && 268 type >= SSH2_MSG_KEXINIT && type <= SSH2_MSG_TRANSPORT_MAX && 269 ssh->dispatch[type] != NULL) { 270 if ((r = (*ssh->dispatch[type])(type, seqnr, ssh)) != 0) 271 return r; 272 } else { 273 *typep = type; 274 return 0; 275 } 276 } 277 } 278 279 const u_char * 280 ssh_packet_payload(struct ssh *ssh, size_t *lenp) 281 { 282 return sshpkt_ptr(ssh, lenp); 283 } 284 285 int 286 ssh_packet_put(struct ssh *ssh, int type, const u_char *data, size_t len) 287 { 288 int r; 289 290 if ((r = sshpkt_start(ssh, type)) != 0 || 291 (r = sshpkt_put(ssh, data, len)) != 0 || 292 (r = sshpkt_send(ssh)) != 0) 293 return r; 294 return 0; 295 } 296 297 const u_char * 298 ssh_output_ptr(struct ssh *ssh, size_t *len) 299 { 300 struct sshbuf *output = ssh_packet_get_output(ssh); 301 302 *len = sshbuf_len(output); 303 return sshbuf_ptr(output); 304 } 305 306 int 307 ssh_output_consume(struct ssh *ssh, size_t len) 308 { 309 return sshbuf_consume(ssh_packet_get_output(ssh), len); 310 } 311 312 int 313 ssh_output_space(struct ssh *ssh, size_t len) 314 { 315 return (0 == sshbuf_check_reserve(ssh_packet_get_output(ssh), len)); 316 } 317 318 int 319 ssh_input_space(struct ssh *ssh, size_t len) 320 { 321 return (0 == sshbuf_check_reserve(ssh_packet_get_input(ssh), len)); 322 } 323 324 /* Read other side's version identification. */ 325 int 326 _ssh_read_banner(struct ssh *ssh, struct sshbuf *banner) 327 { 328 struct sshbuf *input = ssh_packet_get_input(ssh); 329 const char *mismatch = "Protocol mismatch.\r\n"; 330 const u_char *s = sshbuf_ptr(input); 331 u_char c; 332 char *cp = NULL, *remote_version = NULL; 333 int r = 0, remote_major, remote_minor, expect_nl; 334 size_t n, j; 335 336 for (j = n = 0;;) { 337 sshbuf_reset(banner); 338 expect_nl = 0; 339 for (;;) { 340 if (j >= sshbuf_len(input)) 341 return 0; /* insufficient data in input buf */ 342 c = s[j++]; 343 if (c == '\r') { 344 expect_nl = 1; 345 continue; 346 } 347 if (c == '\n') 348 break; 349 if (expect_nl) 350 goto bad; 351 if ((r = sshbuf_put_u8(banner, c)) != 0) 352 return r; 353 if (sshbuf_len(banner) > SSH_MAX_BANNER_LEN) 354 goto bad; 355 } 356 if (sshbuf_len(banner) >= 4 && 357 memcmp(sshbuf_ptr(banner), "SSH-", 4) == 0) 358 break; 359 debug("%s: %.*s", __func__, (int)sshbuf_len(banner), 360 sshbuf_ptr(banner)); 361 /* Accept lines before banner only on client */ 362 if (ssh->kex->server || ++n > SSH_MAX_PRE_BANNER_LINES) { 363 bad: 364 if ((r = sshbuf_put(ssh_packet_get_output(ssh), 365 mismatch, strlen(mismatch))) != 0) 366 return r; 367 return SSH_ERR_NO_PROTOCOL_VERSION; 368 } 369 } 370 if ((r = sshbuf_consume(input, j)) != 0) 371 return r; 372 373 /* XXX remote version must be the same size as banner for sscanf */ 374 if ((cp = sshbuf_dup_string(banner)) == NULL || 375 (remote_version = calloc(1, sshbuf_len(banner))) == NULL) { 376 r = SSH_ERR_ALLOC_FAIL; 377 goto out; 378 } 379 380 /* 381 * Check that the versions match. In future this might accept 382 * several versions and set appropriate flags to handle them. 383 */ 384 if (sscanf(cp, "SSH-%d.%d-%[^\n]\n", 385 &remote_major, &remote_minor, remote_version) != 3) { 386 r = SSH_ERR_INVALID_FORMAT; 387 goto out; 388 } 389 debug("Remote protocol version %d.%d, remote software version %.100s", 390 remote_major, remote_minor, remote_version); 391 392 ssh->compat = compat_datafellows(remote_version); 393 if (remote_major == 1 && remote_minor == 99) { 394 remote_major = 2; 395 remote_minor = 0; 396 } 397 if (remote_major != 2) 398 r = SSH_ERR_PROTOCOL_MISMATCH; 399 400 debug("Remote version string %.100s", cp); 401 out: 402 free(cp); 403 free(remote_version); 404 return r; 405 } 406 407 /* Send our own protocol version identification. */ 408 int 409 _ssh_send_banner(struct ssh *ssh, struct sshbuf *banner) 410 { 411 char *cp; 412 int r; 413 414 if ((r = sshbuf_putf(banner, "SSH-2.0-%.100s\r\n", SSH_VERSION)) != 0) 415 return r; 416 if ((r = sshbuf_putb(ssh_packet_get_output(ssh), banner)) != 0) 417 return r; 418 /* Remove trailing \r\n */ 419 if ((r = sshbuf_consume_end(banner, 2)) != 0) 420 return r; 421 if ((cp = sshbuf_dup_string(banner)) == NULL) 422 return SSH_ERR_ALLOC_FAIL; 423 debug("Local version string %.100s", cp); 424 free(cp); 425 return 0; 426 } 427 428 int 429 _ssh_exchange_banner(struct ssh *ssh) 430 { 431 struct kex *kex = ssh->kex; 432 int r; 433 434 /* 435 * if _ssh_read_banner() cannot parse a full version string 436 * it will return NULL and we end up calling it again. 437 */ 438 439 r = 0; 440 if (kex->server) { 441 if (sshbuf_len(ssh->kex->server_version) == 0) 442 r = _ssh_send_banner(ssh, ssh->kex->server_version); 443 if (r == 0 && 444 sshbuf_len(ssh->kex->server_version) != 0 && 445 sshbuf_len(ssh->kex->client_version) == 0) 446 r = _ssh_read_banner(ssh, ssh->kex->client_version); 447 } else { 448 if (sshbuf_len(ssh->kex->server_version) == 0) 449 r = _ssh_read_banner(ssh, ssh->kex->server_version); 450 if (r == 0 && 451 sshbuf_len(ssh->kex->server_version) != 0 && 452 sshbuf_len(ssh->kex->client_version) == 0) 453 r = _ssh_send_banner(ssh, ssh->kex->client_version); 454 } 455 if (r != 0) 456 return r; 457 /* start initial kex as soon as we have exchanged the banners */ 458 if (sshbuf_len(ssh->kex->server_version) != 0 && 459 sshbuf_len(ssh->kex->client_version) != 0) { 460 if ((r = _ssh_order_hostkeyalgs(ssh)) != 0 || 461 (r = kex_send_kexinit(ssh)) != 0) 462 return r; 463 } 464 return 0; 465 } 466 467 struct sshkey * 468 _ssh_host_public_key(int type, int nid, struct ssh *ssh) 469 { 470 struct key_entry *k; 471 472 debug3("%s: need %d", __func__, type); 473 TAILQ_FOREACH(k, &ssh->public_keys, next) { 474 debug3("%s: check %s", __func__, sshkey_type(k->key)); 475 if (k->key->type == type && 476 (type != KEY_ECDSA || k->key->ecdsa_nid == nid)) 477 return (k->key); 478 } 479 return (NULL); 480 } 481 482 struct sshkey * 483 _ssh_host_private_key(int type, int nid, struct ssh *ssh) 484 { 485 struct key_entry *k; 486 487 debug3("%s: need %d", __func__, type); 488 TAILQ_FOREACH(k, &ssh->private_keys, next) { 489 debug3("%s: check %s", __func__, 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 int 498 _ssh_verify_host_key(struct sshkey *hostkey, struct ssh *ssh) 499 { 500 struct key_entry *k; 501 502 debug3("%s: need %s", __func__, sshkey_type(hostkey)); 503 TAILQ_FOREACH(k, &ssh->public_keys, next) { 504 debug3("%s: check %s", __func__, sshkey_type(k->key)); 505 if (sshkey_equal_public(hostkey, k->key)) 506 return (0); /* ok */ 507 } 508 return (-1); /* failed */ 509 } 510 511 /* offer hostkey algorithms in kexinit depending on registered keys */ 512 int 513 _ssh_order_hostkeyalgs(struct ssh *ssh) 514 { 515 struct key_entry *k; 516 char *orig, *avail, *oavail = NULL, *alg, *replace = NULL; 517 char **proposal; 518 size_t maxlen; 519 int ktype, r; 520 521 /* XXX we de-serialize ssh->kex->my, modify it, and change it */ 522 if ((r = kex_buf2prop(ssh->kex->my, NULL, &proposal)) != 0) 523 return r; 524 orig = proposal[PROPOSAL_SERVER_HOST_KEY_ALGS]; 525 if ((oavail = avail = strdup(orig)) == NULL) { 526 r = SSH_ERR_ALLOC_FAIL; 527 goto out; 528 } 529 maxlen = strlen(avail) + 1; 530 if ((replace = calloc(1, maxlen)) == NULL) { 531 r = SSH_ERR_ALLOC_FAIL; 532 goto out; 533 } 534 *replace = '\0'; 535 while ((alg = strsep(&avail, ",")) && *alg != '\0') { 536 if ((ktype = sshkey_type_from_name(alg)) == KEY_UNSPEC) 537 continue; 538 TAILQ_FOREACH(k, &ssh->public_keys, next) { 539 if (k->key->type == ktype || 540 (sshkey_is_cert(k->key) && k->key->type == 541 sshkey_type_plain(ktype))) { 542 if (*replace != '\0') 543 strlcat(replace, ",", maxlen); 544 strlcat(replace, alg, maxlen); 545 break; 546 } 547 } 548 } 549 if (*replace != '\0') { 550 debug2("%s: orig/%d %s", __func__, ssh->kex->server, orig); 551 debug2("%s: replace/%d %s", __func__, ssh->kex->server, replace); 552 free(orig); 553 proposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = replace; 554 replace = NULL; /* owned by proposal */ 555 r = kex_prop2buf(ssh->kex->my, (const char **)(void *)proposal); 556 } 557 out: 558 free(oavail); 559 free(replace); 560 kex_prop_free(proposal); 561 return r; 562 } 563 564 int 565 _ssh_host_key_sign(struct ssh *ssh, struct sshkey *privkey, 566 struct sshkey *pubkey, u_char **signature, size_t *slen, 567 const u_char *data, size_t dlen, const char *alg) 568 { 569 return sshkey_sign(privkey, signature, slen, data, dlen, 570 alg, NULL, ssh->compat); 571 } 572