1 /* $OpenBSD: ssh_api.c,v 1.8 2017/04/30 23:13:25 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 "ssh_api.h" 21 #include "compat.h" 22 #include "log.h" 23 #include "authfile.h" 24 #include "sshkey.h" 25 #include "misc.h" 26 #include "ssh2.h" 27 #include "version.h" 28 #include "myproposal.h" 29 #include "ssherr.h" 30 #include "sshbuf.h" 31 32 #include <string.h> 33 34 int _ssh_exchange_banner(struct ssh *); 35 int _ssh_send_banner(struct ssh *, char **); 36 int _ssh_read_banner(struct ssh *, char **); 37 int _ssh_order_hostkeyalgs(struct ssh *); 38 int _ssh_verify_host_key(struct sshkey *, struct ssh *); 39 struct sshkey *_ssh_host_public_key(int, int, struct ssh *); 40 struct sshkey *_ssh_host_private_key(int, int, struct ssh *); 41 int _ssh_host_key_sign(struct sshkey *, struct sshkey *, 42 u_char **, size_t *, const u_char *, size_t, const char *, u_int); 43 44 /* 45 * stubs for the server side implementation of kex. 46 * disable privsep so our stubs will never be called. 47 */ 48 int use_privsep = 0; 49 int mm_sshkey_sign(struct sshkey *, u_char **, u_int *, 50 u_char *, u_int, char *, u_int); 51 DH *mm_choose_dh(int, int, int); 52 53 /* Define these two variables here so that they are part of the library */ 54 u_char *session_id2 = NULL; 55 u_int session_id2_len = 0; 56 57 int 58 mm_sshkey_sign(struct sshkey *key, u_char **sigp, u_int *lenp, 59 u_char *data, u_int datalen, char *alg, u_int compat) 60 { 61 return (-1); 62 } 63 64 DH * 65 mm_choose_dh(int min, int nbits, int max) 66 { 67 return (NULL); 68 } 69 70 /* API */ 71 72 int 73 ssh_init(struct ssh **sshp, int is_server, struct kex_params *kex_params) 74 { 75 char *myproposal[PROPOSAL_MAX] = { KEX_CLIENT }; 76 struct ssh *ssh; 77 char **proposal; 78 static int called; 79 int r; 80 81 if (!called) { 82 #ifdef WITH_OPENSSL 83 OpenSSL_add_all_algorithms(); 84 #endif /* WITH_OPENSSL */ 85 called = 1; 86 } 87 88 if ((ssh = ssh_packet_set_connection(NULL, -1, -1)) == NULL) 89 return SSH_ERR_ALLOC_FAIL; 90 if (is_server) 91 ssh_packet_set_server(ssh); 92 93 /* Initialize key exchange */ 94 proposal = kex_params ? kex_params->proposal : myproposal; 95 if ((r = kex_new(ssh, proposal, &ssh->kex)) != 0) { 96 ssh_free(ssh); 97 return r; 98 } 99 ssh->kex->server = is_server; 100 if (is_server) { 101 #ifdef WITH_OPENSSL 102 ssh->kex->kex[KEX_DH_GRP1_SHA1] = kexdh_server; 103 ssh->kex->kex[KEX_DH_GRP14_SHA1] = kexdh_server; 104 ssh->kex->kex[KEX_DH_GRP14_SHA256] = kexdh_server; 105 ssh->kex->kex[KEX_DH_GRP16_SHA512] = kexdh_server; 106 ssh->kex->kex[KEX_DH_GRP18_SHA512] = kexdh_server; 107 ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_server; 108 ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_server; 109 # ifdef OPENSSL_HAS_ECC 110 ssh->kex->kex[KEX_ECDH_SHA2] = kexecdh_server; 111 # endif 112 #endif /* WITH_OPENSSL */ 113 ssh->kex->kex[KEX_C25519_SHA256] = kexc25519_server; 114 ssh->kex->load_host_public_key=&_ssh_host_public_key; 115 ssh->kex->load_host_private_key=&_ssh_host_private_key; 116 ssh->kex->sign=&_ssh_host_key_sign; 117 } else { 118 #ifdef WITH_OPENSSL 119 ssh->kex->kex[KEX_DH_GRP1_SHA1] = kexdh_client; 120 ssh->kex->kex[KEX_DH_GRP14_SHA1] = kexdh_client; 121 ssh->kex->kex[KEX_DH_GRP14_SHA256] = kexdh_client; 122 ssh->kex->kex[KEX_DH_GRP16_SHA512] = kexdh_client; 123 ssh->kex->kex[KEX_DH_GRP18_SHA512] = kexdh_client; 124 ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_client; 125 ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_client; 126 # ifdef OPENSSL_HAS_ECC 127 ssh->kex->kex[KEX_ECDH_SHA2] = kexecdh_client; 128 # endif 129 #endif /* WITH_OPENSSL */ 130 ssh->kex->kex[KEX_C25519_SHA256] = kexc25519_client; 131 ssh->kex->verify_host_key =&_ssh_verify_host_key; 132 } 133 *sshp = ssh; 134 return 0; 135 } 136 137 void 138 ssh_free(struct ssh *ssh) 139 { 140 struct key_entry *k; 141 142 ssh_packet_close(ssh); 143 /* 144 * we've only created the public keys variants in case we 145 * are a acting as a server. 146 */ 147 while ((k = TAILQ_FIRST(&ssh->public_keys)) != NULL) { 148 TAILQ_REMOVE(&ssh->public_keys, k, next); 149 if (ssh->kex && ssh->kex->server) 150 sshkey_free(k->key); 151 free(k); 152 } 153 while ((k = TAILQ_FIRST(&ssh->private_keys)) != NULL) { 154 TAILQ_REMOVE(&ssh->private_keys, k, next); 155 free(k); 156 } 157 if (ssh->kex) 158 kex_free(ssh->kex); 159 free(ssh); 160 } 161 162 void 163 ssh_set_app_data(struct ssh *ssh, void *app_data) 164 { 165 ssh->app_data = app_data; 166 } 167 168 void * 169 ssh_get_app_data(struct ssh *ssh) 170 { 171 return ssh->app_data; 172 } 173 174 /* Returns < 0 on error, 0 otherwise */ 175 int 176 ssh_add_hostkey(struct ssh *ssh, struct sshkey *key) 177 { 178 struct sshkey *pubkey = NULL; 179 struct key_entry *k = NULL, *k_prv = NULL; 180 int r; 181 182 if (ssh->kex->server) { 183 if ((r = sshkey_from_private(key, &pubkey)) != 0) 184 return r; 185 if ((k = malloc(sizeof(*k))) == NULL || 186 (k_prv = malloc(sizeof(*k_prv))) == NULL) { 187 free(k); 188 sshkey_free(pubkey); 189 return SSH_ERR_ALLOC_FAIL; 190 } 191 k_prv->key = key; 192 TAILQ_INSERT_TAIL(&ssh->private_keys, k_prv, next); 193 194 /* add the public key, too */ 195 k->key = pubkey; 196 TAILQ_INSERT_TAIL(&ssh->public_keys, k, next); 197 r = 0; 198 } else { 199 if ((k = malloc(sizeof(*k))) == NULL) 200 return SSH_ERR_ALLOC_FAIL; 201 k->key = key; 202 TAILQ_INSERT_TAIL(&ssh->public_keys, k, next); 203 r = 0; 204 } 205 206 return r; 207 } 208 209 int 210 ssh_set_verify_host_key_callback(struct ssh *ssh, 211 int (*cb)(struct sshkey *, struct ssh *)) 212 { 213 if (cb == NULL || ssh->kex == NULL) 214 return SSH_ERR_INVALID_ARGUMENT; 215 216 ssh->kex->verify_host_key = cb; 217 218 return 0; 219 } 220 221 int 222 ssh_input_append(struct ssh *ssh, const u_char *data, size_t len) 223 { 224 return sshbuf_put(ssh_packet_get_input(ssh), data, len); 225 } 226 227 int 228 ssh_packet_next(struct ssh *ssh, u_char *typep) 229 { 230 int r; 231 u_int32_t seqnr; 232 u_char type; 233 234 /* 235 * Try to read a packet. Return SSH_MSG_NONE if no packet or not 236 * enough data. 237 */ 238 *typep = SSH_MSG_NONE; 239 if (ssh->kex->client_version_string == NULL || 240 ssh->kex->server_version_string == NULL) 241 return _ssh_exchange_banner(ssh); 242 /* 243 * If we enough data and a dispatch function then 244 * call the function and get the next packet. 245 * Otherwise return the packet type to the caller so it 246 * can decide how to go on. 247 * 248 * We will only call the dispatch function for: 249 * 20-29 Algorithm negotiation 250 * 30-49 Key exchange method specific (numbers can be reused for 251 * different authentication methods) 252 */ 253 for (;;) { 254 if ((r = ssh_packet_read_poll2(ssh, &type, &seqnr)) != 0) 255 return r; 256 if (type > 0 && type < DISPATCH_MAX && 257 type >= SSH2_MSG_KEXINIT && type <= SSH2_MSG_TRANSPORT_MAX && 258 ssh->dispatch[type] != NULL) { 259 if ((r = (*ssh->dispatch[type])(type, seqnr, ssh)) != 0) 260 return r; 261 } else { 262 *typep = type; 263 return 0; 264 } 265 } 266 } 267 268 const u_char * 269 ssh_packet_payload(struct ssh *ssh, size_t *lenp) 270 { 271 return sshpkt_ptr(ssh, lenp); 272 } 273 274 int 275 ssh_packet_put(struct ssh *ssh, int type, const u_char *data, size_t len) 276 { 277 int r; 278 279 if ((r = sshpkt_start(ssh, type)) != 0 || 280 (r = sshpkt_put(ssh, data, len)) != 0 || 281 (r = sshpkt_send(ssh)) != 0) 282 return r; 283 return 0; 284 } 285 286 const u_char * 287 ssh_output_ptr(struct ssh *ssh, size_t *len) 288 { 289 struct sshbuf *output = ssh_packet_get_output(ssh); 290 291 *len = sshbuf_len(output); 292 return sshbuf_ptr(output); 293 } 294 295 int 296 ssh_output_consume(struct ssh *ssh, size_t len) 297 { 298 return sshbuf_consume(ssh_packet_get_output(ssh), len); 299 } 300 301 int 302 ssh_output_space(struct ssh *ssh, size_t len) 303 { 304 return (0 == sshbuf_check_reserve(ssh_packet_get_output(ssh), len)); 305 } 306 307 int 308 ssh_input_space(struct ssh *ssh, size_t len) 309 { 310 return (0 == sshbuf_check_reserve(ssh_packet_get_input(ssh), len)); 311 } 312 313 /* Read other side's version identification. */ 314 int 315 _ssh_read_banner(struct ssh *ssh, char **bannerp) 316 { 317 struct sshbuf *input; 318 const char *s; 319 char buf[256], remote_version[256]; /* must be same size! */ 320 const char *mismatch = "Protocol mismatch.\r\n"; 321 int r, remote_major, remote_minor; 322 size_t i, n, j, len; 323 324 *bannerp = NULL; 325 input = ssh_packet_get_input(ssh); 326 len = sshbuf_len(input); 327 s = (const char *)sshbuf_ptr(input); 328 for (j = n = 0;;) { 329 for (i = 0; i < sizeof(buf) - 1; i++) { 330 if (j >= len) 331 return (0); 332 buf[i] = s[j++]; 333 if (buf[i] == '\r') { 334 buf[i] = '\n'; 335 buf[i + 1] = 0; 336 continue; /**XXX wait for \n */ 337 } 338 if (buf[i] == '\n') { 339 buf[i + 1] = 0; 340 break; 341 } 342 } 343 buf[sizeof(buf) - 1] = 0; 344 if (strncmp(buf, "SSH-", 4) == 0) 345 break; 346 debug("ssh_exchange_identification: %s", buf); 347 if (ssh->kex->server || ++n > 65536) { 348 if ((r = sshbuf_put(ssh_packet_get_output(ssh), 349 mismatch, strlen(mismatch))) != 0) 350 return r; 351 return SSH_ERR_NO_PROTOCOL_VERSION; 352 } 353 } 354 if ((r = sshbuf_consume(input, j)) != 0) 355 return r; 356 357 /* 358 * Check that the versions match. In future this might accept 359 * several versions and set appropriate flags to handle them. 360 */ 361 if (sscanf(buf, "SSH-%d.%d-%[^\n]\n", 362 &remote_major, &remote_minor, remote_version) != 3) 363 return SSH_ERR_INVALID_FORMAT; 364 debug("Remote protocol version %d.%d, remote software version %.100s", 365 remote_major, remote_minor, remote_version); 366 367 ssh->compat = compat_datafellows(remote_version); 368 if (remote_major == 1 && remote_minor == 99) { 369 remote_major = 2; 370 remote_minor = 0; 371 } 372 if (remote_major != 2) 373 return SSH_ERR_PROTOCOL_MISMATCH; 374 chop(buf); 375 debug("Remote version string %.100s", buf); 376 if ((*bannerp = strdup(buf)) == NULL) 377 return SSH_ERR_ALLOC_FAIL; 378 return 0; 379 } 380 381 /* Send our own protocol version identification. */ 382 int 383 _ssh_send_banner(struct ssh *ssh, char **bannerp) 384 { 385 char buf[256]; 386 int r; 387 388 snprintf(buf, sizeof buf, "SSH-2.0-%.100s\r\n", SSH_VERSION); 389 if ((r = sshbuf_put(ssh_packet_get_output(ssh), buf, strlen(buf))) != 0) 390 return r; 391 chop(buf); 392 debug("Local version string %.100s", buf); 393 if ((*bannerp = strdup(buf)) == NULL) 394 return SSH_ERR_ALLOC_FAIL; 395 return 0; 396 } 397 398 int 399 _ssh_exchange_banner(struct ssh *ssh) 400 { 401 struct kex *kex = ssh->kex; 402 int r; 403 404 /* 405 * if _ssh_read_banner() cannot parse a full version string 406 * it will return NULL and we end up calling it again. 407 */ 408 409 r = 0; 410 if (kex->server) { 411 if (kex->server_version_string == NULL) 412 r = _ssh_send_banner(ssh, &kex->server_version_string); 413 if (r == 0 && 414 kex->server_version_string != NULL && 415 kex->client_version_string == NULL) 416 r = _ssh_read_banner(ssh, &kex->client_version_string); 417 } else { 418 if (kex->server_version_string == NULL) 419 r = _ssh_read_banner(ssh, &kex->server_version_string); 420 if (r == 0 && 421 kex->server_version_string != NULL && 422 kex->client_version_string == NULL) 423 r = _ssh_send_banner(ssh, &kex->client_version_string); 424 } 425 if (r != 0) 426 return r; 427 /* start initial kex as soon as we have exchanged the banners */ 428 if (kex->server_version_string != NULL && 429 kex->client_version_string != NULL) { 430 if ((r = _ssh_order_hostkeyalgs(ssh)) != 0 || 431 (r = kex_send_kexinit(ssh)) != 0) 432 return r; 433 } 434 return 0; 435 } 436 437 struct sshkey * 438 _ssh_host_public_key(int type, int nid, struct ssh *ssh) 439 { 440 struct key_entry *k; 441 442 debug3("%s: need %d", __func__, type); 443 TAILQ_FOREACH(k, &ssh->public_keys, next) { 444 debug3("%s: check %s", __func__, sshkey_type(k->key)); 445 if (k->key->type == type && 446 (type != KEY_ECDSA || k->key->ecdsa_nid == nid)) 447 return (k->key); 448 } 449 return (NULL); 450 } 451 452 struct sshkey * 453 _ssh_host_private_key(int type, int nid, struct ssh *ssh) 454 { 455 struct key_entry *k; 456 457 debug3("%s: need %d", __func__, type); 458 TAILQ_FOREACH(k, &ssh->private_keys, next) { 459 debug3("%s: check %s", __func__, sshkey_type(k->key)); 460 if (k->key->type == type && 461 (type != KEY_ECDSA || k->key->ecdsa_nid == nid)) 462 return (k->key); 463 } 464 return (NULL); 465 } 466 467 int 468 _ssh_verify_host_key(struct sshkey *hostkey, struct ssh *ssh) 469 { 470 struct key_entry *k; 471 472 debug3("%s: need %s", __func__, sshkey_type(hostkey)); 473 TAILQ_FOREACH(k, &ssh->public_keys, next) { 474 debug3("%s: check %s", __func__, sshkey_type(k->key)); 475 if (sshkey_equal_public(hostkey, k->key)) 476 return (0); /* ok */ 477 } 478 return (-1); /* failed */ 479 } 480 481 /* offer hostkey algorithms in kexinit depending on registered keys */ 482 int 483 _ssh_order_hostkeyalgs(struct ssh *ssh) 484 { 485 struct key_entry *k; 486 char *orig, *avail, *oavail = NULL, *alg, *replace = NULL; 487 char **proposal; 488 size_t maxlen; 489 int ktype, r; 490 491 /* XXX we de-serialize ssh->kex->my, modify it, and change it */ 492 if ((r = kex_buf2prop(ssh->kex->my, NULL, &proposal)) != 0) 493 return r; 494 orig = proposal[PROPOSAL_SERVER_HOST_KEY_ALGS]; 495 if ((oavail = avail = strdup(orig)) == NULL) { 496 r = SSH_ERR_ALLOC_FAIL; 497 goto out; 498 } 499 maxlen = strlen(avail) + 1; 500 if ((replace = calloc(1, maxlen)) == NULL) { 501 r = SSH_ERR_ALLOC_FAIL; 502 goto out; 503 } 504 *replace = '\0'; 505 while ((alg = strsep(&avail, ",")) && *alg != '\0') { 506 if ((ktype = sshkey_type_from_name(alg)) == KEY_UNSPEC) 507 continue; 508 TAILQ_FOREACH(k, &ssh->public_keys, next) { 509 if (k->key->type == ktype || 510 (sshkey_is_cert(k->key) && k->key->type == 511 sshkey_type_plain(ktype))) { 512 if (*replace != '\0') 513 strlcat(replace, ",", maxlen); 514 strlcat(replace, alg, maxlen); 515 break; 516 } 517 } 518 } 519 if (*replace != '\0') { 520 debug2("%s: orig/%d %s", __func__, ssh->kex->server, orig); 521 debug2("%s: replace/%d %s", __func__, ssh->kex->server, replace); 522 free(orig); 523 proposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = replace; 524 replace = NULL; /* owned by proposal */ 525 r = kex_prop2buf(ssh->kex->my, proposal); 526 } 527 out: 528 free(oavail); 529 free(replace); 530 kex_prop_free(proposal); 531 return r; 532 } 533 534 int 535 _ssh_host_key_sign(struct sshkey *privkey, struct sshkey *pubkey, 536 u_char **signature, size_t *slen, const u_char *data, size_t dlen, 537 const char *alg, u_int compat) 538 { 539 return sshkey_sign(privkey, signature, slen, data, dlen, alg, compat); 540 } 541