1 /* $OpenBSD: ssh_api.c,v 1.6 2016/05/02 10:26:04 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 "ssh1.h" /* For SSH_MSG_NONE */ 21 #include "ssh_api.h" 22 #include "compat.h" 23 #include "log.h" 24 #include "authfile.h" 25 #include "sshkey.h" 26 #include "misc.h" 27 #include "ssh1.h" 28 #include "ssh2.h" 29 #include "version.h" 30 #include "myproposal.h" 31 #include "ssherr.h" 32 #include "sshbuf.h" 33 34 #include <string.h> 35 36 int _ssh_exchange_banner(struct ssh *); 37 int _ssh_send_banner(struct ssh *, char **); 38 int _ssh_read_banner(struct ssh *, char **); 39 int _ssh_order_hostkeyalgs(struct ssh *); 40 int _ssh_verify_host_key(struct sshkey *, struct ssh *); 41 struct sshkey *_ssh_host_public_key(int, int, struct ssh *); 42 struct sshkey *_ssh_host_private_key(int, int, struct ssh *); 43 int _ssh_host_key_sign(struct sshkey *, struct sshkey *, 44 u_char **, size_t *, const u_char *, size_t, const char *, u_int); 45 46 /* 47 * stubs for the server side implementation of kex. 48 * disable privsep so our stubs will never be called. 49 */ 50 int use_privsep = 0; 51 int mm_sshkey_sign(struct sshkey *, u_char **, u_int *, 52 u_char *, u_int, char *, u_int); 53 DH *mm_choose_dh(int, int, int); 54 55 /* Define these two variables here so that they are part of the library */ 56 u_char *session_id2 = NULL; 57 u_int session_id2_len = 0; 58 59 int 60 mm_sshkey_sign(struct sshkey *key, u_char **sigp, u_int *lenp, 61 u_char *data, u_int datalen, char *alg, u_int compat) 62 { 63 return (-1); 64 } 65 66 DH * 67 mm_choose_dh(int min, int nbits, int max) 68 { 69 return (NULL); 70 } 71 72 /* API */ 73 74 int 75 ssh_init(struct ssh **sshp, int is_server, struct kex_params *kex_params) 76 { 77 char *myproposal[PROPOSAL_MAX] = { KEX_CLIENT }; 78 struct ssh *ssh; 79 char **proposal; 80 static int called; 81 int r; 82 83 if (!called) { 84 #ifdef WITH_OPENSSL 85 OpenSSL_add_all_algorithms(); 86 #endif /* WITH_OPENSSL */ 87 called = 1; 88 } 89 90 if ((ssh = ssh_packet_set_connection(NULL, -1, -1)) == NULL) 91 return SSH_ERR_ALLOC_FAIL; 92 if (is_server) 93 ssh_packet_set_server(ssh); 94 95 /* Initialize key exchange */ 96 proposal = kex_params ? kex_params->proposal : myproposal; 97 if ((r = kex_new(ssh, proposal, &ssh->kex)) != 0) { 98 ssh_free(ssh); 99 return r; 100 } 101 ssh->kex->server = is_server; 102 if (is_server) { 103 #ifdef WITH_OPENSSL 104 ssh->kex->kex[KEX_DH_GRP1_SHA1] = kexdh_server; 105 ssh->kex->kex[KEX_DH_GRP14_SHA1] = kexdh_server; 106 ssh->kex->kex[KEX_DH_GRP14_SHA256] = kexdh_server; 107 ssh->kex->kex[KEX_DH_GRP16_SHA512] = kexdh_server; 108 ssh->kex->kex[KEX_DH_GRP18_SHA512] = kexdh_server; 109 ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_server; 110 ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_server; 111 # ifdef OPENSSL_HAS_ECC 112 ssh->kex->kex[KEX_ECDH_SHA2] = kexecdh_server; 113 # endif 114 #endif /* WITH_OPENSSL */ 115 ssh->kex->kex[KEX_C25519_SHA256] = kexc25519_server; 116 ssh->kex->load_host_public_key=&_ssh_host_public_key; 117 ssh->kex->load_host_private_key=&_ssh_host_private_key; 118 ssh->kex->sign=&_ssh_host_key_sign; 119 } else { 120 #ifdef WITH_OPENSSL 121 ssh->kex->kex[KEX_DH_GRP1_SHA1] = kexdh_client; 122 ssh->kex->kex[KEX_DH_GRP14_SHA1] = kexdh_client; 123 ssh->kex->kex[KEX_DH_GRP14_SHA256] = kexdh_client; 124 ssh->kex->kex[KEX_DH_GRP16_SHA512] = kexdh_client; 125 ssh->kex->kex[KEX_DH_GRP18_SHA512] = kexdh_client; 126 ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_client; 127 ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_client; 128 # ifdef OPENSSL_HAS_ECC 129 ssh->kex->kex[KEX_ECDH_SHA2] = kexecdh_client; 130 # endif 131 #endif /* WITH_OPENSSL */ 132 ssh->kex->kex[KEX_C25519_SHA256] = kexc25519_client; 133 ssh->kex->verify_host_key =&_ssh_verify_host_key; 134 } 135 *sshp = ssh; 136 return 0; 137 } 138 139 void 140 ssh_free(struct ssh *ssh) 141 { 142 struct key_entry *k; 143 144 ssh_packet_close(ssh); 145 /* 146 * we've only created the public keys variants in case we 147 * are a acting as a server. 148 */ 149 while ((k = TAILQ_FIRST(&ssh->public_keys)) != NULL) { 150 TAILQ_REMOVE(&ssh->public_keys, k, next); 151 if (ssh->kex && ssh->kex->server) 152 sshkey_free(k->key); 153 free(k); 154 } 155 while ((k = TAILQ_FIRST(&ssh->private_keys)) != NULL) { 156 TAILQ_REMOVE(&ssh->private_keys, k, next); 157 free(k); 158 } 159 if (ssh->kex) 160 kex_free(ssh->kex); 161 free(ssh); 162 } 163 164 void 165 ssh_set_app_data(struct ssh *ssh, void *app_data) 166 { 167 ssh->app_data = app_data; 168 } 169 170 void * 171 ssh_get_app_data(struct ssh *ssh) 172 { 173 return ssh->app_data; 174 } 175 176 /* Returns < 0 on error, 0 otherwise */ 177 int 178 ssh_add_hostkey(struct ssh *ssh, struct sshkey *key) 179 { 180 struct sshkey *pubkey = NULL; 181 struct key_entry *k = NULL, *k_prv = NULL; 182 int r; 183 184 if (ssh->kex->server) { 185 if ((r = sshkey_from_private(key, &pubkey)) != 0) 186 return r; 187 if ((k = malloc(sizeof(*k))) == NULL || 188 (k_prv = malloc(sizeof(*k_prv))) == NULL) { 189 free(k); 190 sshkey_free(pubkey); 191 return SSH_ERR_ALLOC_FAIL; 192 } 193 k_prv->key = key; 194 TAILQ_INSERT_TAIL(&ssh->private_keys, k_prv, next); 195 196 /* add the public key, too */ 197 k->key = pubkey; 198 TAILQ_INSERT_TAIL(&ssh->public_keys, k, next); 199 r = 0; 200 } else { 201 if ((k = malloc(sizeof(*k))) == NULL) 202 return SSH_ERR_ALLOC_FAIL; 203 k->key = key; 204 TAILQ_INSERT_TAIL(&ssh->public_keys, k, next); 205 r = 0; 206 } 207 208 return r; 209 } 210 211 int 212 ssh_set_verify_host_key_callback(struct ssh *ssh, 213 int (*cb)(struct sshkey *, struct ssh *)) 214 { 215 if (cb == NULL || ssh->kex == NULL) 216 return SSH_ERR_INVALID_ARGUMENT; 217 218 ssh->kex->verify_host_key = cb; 219 220 return 0; 221 } 222 223 int 224 ssh_input_append(struct ssh *ssh, const u_char *data, size_t len) 225 { 226 return sshbuf_put(ssh_packet_get_input(ssh), data, len); 227 } 228 229 int 230 ssh_packet_next(struct ssh *ssh, u_char *typep) 231 { 232 int r; 233 u_int32_t seqnr; 234 u_char type; 235 236 /* 237 * Try to read a packet. Return SSH_MSG_NONE if no packet or not 238 * enough data. 239 */ 240 *typep = SSH_MSG_NONE; 241 if (ssh->kex->client_version_string == NULL || 242 ssh->kex->server_version_string == NULL) 243 return _ssh_exchange_banner(ssh); 244 /* 245 * If we enough data and a dispatch function then 246 * call the function and get the next packet. 247 * Otherwise return the packet type to the caller so it 248 * can decide how to go on. 249 * 250 * We will only call the dispatch function for: 251 * 20-29 Algorithm negotiation 252 * 30-49 Key exchange method specific (numbers can be reused for 253 * different authentication methods) 254 */ 255 for (;;) { 256 if ((r = ssh_packet_read_poll2(ssh, &type, &seqnr)) != 0) 257 return r; 258 if (type > 0 && type < DISPATCH_MAX && 259 type >= SSH2_MSG_KEXINIT && type <= SSH2_MSG_TRANSPORT_MAX && 260 ssh->dispatch[type] != NULL) { 261 if ((r = (*ssh->dispatch[type])(type, seqnr, ssh)) != 0) 262 return r; 263 } else { 264 *typep = type; 265 return 0; 266 } 267 } 268 } 269 270 const u_char * 271 ssh_packet_payload(struct ssh *ssh, size_t *lenp) 272 { 273 return sshpkt_ptr(ssh, lenp); 274 } 275 276 int 277 ssh_packet_put(struct ssh *ssh, int type, const u_char *data, size_t len) 278 { 279 int r; 280 281 if ((r = sshpkt_start(ssh, type)) != 0 || 282 (r = sshpkt_put(ssh, data, len)) != 0 || 283 (r = sshpkt_send(ssh)) != 0) 284 return r; 285 return 0; 286 } 287 288 const u_char * 289 ssh_output_ptr(struct ssh *ssh, size_t *len) 290 { 291 struct sshbuf *output = ssh_packet_get_output(ssh); 292 293 *len = sshbuf_len(output); 294 return sshbuf_ptr(output); 295 } 296 297 int 298 ssh_output_consume(struct ssh *ssh, size_t len) 299 { 300 return sshbuf_consume(ssh_packet_get_output(ssh), len); 301 } 302 303 int 304 ssh_output_space(struct ssh *ssh, size_t len) 305 { 306 return (0 == sshbuf_check_reserve(ssh_packet_get_output(ssh), len)); 307 } 308 309 int 310 ssh_input_space(struct ssh *ssh, size_t len) 311 { 312 return (0 == sshbuf_check_reserve(ssh_packet_get_input(ssh), len)); 313 } 314 315 /* Read other side's version identification. */ 316 int 317 _ssh_read_banner(struct ssh *ssh, char **bannerp) 318 { 319 struct sshbuf *input; 320 const char *s; 321 char buf[256], remote_version[256]; /* must be same size! */ 322 const char *mismatch = "Protocol mismatch.\r\n"; 323 int r, remote_major, remote_minor; 324 size_t i, n, j, len; 325 326 *bannerp = NULL; 327 input = ssh_packet_get_input(ssh); 328 len = sshbuf_len(input); 329 s = (const char *)sshbuf_ptr(input); 330 for (j = n = 0;;) { 331 for (i = 0; i < sizeof(buf) - 1; i++) { 332 if (j >= len) 333 return (0); 334 buf[i] = s[j++]; 335 if (buf[i] == '\r') { 336 buf[i] = '\n'; 337 buf[i + 1] = 0; 338 continue; /**XXX wait for \n */ 339 } 340 if (buf[i] == '\n') { 341 buf[i + 1] = 0; 342 break; 343 } 344 } 345 buf[sizeof(buf) - 1] = 0; 346 if (strncmp(buf, "SSH-", 4) == 0) 347 break; 348 debug("ssh_exchange_identification: %s", buf); 349 if (ssh->kex->server || ++n > 65536) { 350 if ((r = sshbuf_put(ssh_packet_get_output(ssh), 351 mismatch, strlen(mismatch))) != 0) 352 return r; 353 return SSH_ERR_NO_PROTOCOL_VERSION; 354 } 355 } 356 if ((r = sshbuf_consume(input, j)) != 0) 357 return r; 358 359 /* 360 * Check that the versions match. In future this might accept 361 * several versions and set appropriate flags to handle them. 362 */ 363 if (sscanf(buf, "SSH-%d.%d-%[^\n]\n", 364 &remote_major, &remote_minor, remote_version) != 3) 365 return SSH_ERR_INVALID_FORMAT; 366 debug("Remote protocol version %d.%d, remote software version %.100s", 367 remote_major, remote_minor, remote_version); 368 369 ssh->compat = compat_datafellows(remote_version); 370 if (remote_major == 1 && remote_minor == 99) { 371 remote_major = 2; 372 remote_minor = 0; 373 } 374 if (remote_major != 2) 375 return SSH_ERR_PROTOCOL_MISMATCH; 376 enable_compat20(); 377 chop(buf); 378 debug("Remote version string %.100s", buf); 379 if ((*bannerp = strdup(buf)) == NULL) 380 return SSH_ERR_ALLOC_FAIL; 381 return 0; 382 } 383 384 /* Send our own protocol version identification. */ 385 int 386 _ssh_send_banner(struct ssh *ssh, char **bannerp) 387 { 388 char buf[256]; 389 int r; 390 391 snprintf(buf, sizeof buf, "SSH-2.0-%.100s\r\n", SSH_VERSION); 392 if ((r = sshbuf_put(ssh_packet_get_output(ssh), buf, strlen(buf))) != 0) 393 return r; 394 chop(buf); 395 debug("Local version string %.100s", buf); 396 if ((*bannerp = strdup(buf)) == NULL) 397 return SSH_ERR_ALLOC_FAIL; 398 return 0; 399 } 400 401 int 402 _ssh_exchange_banner(struct ssh *ssh) 403 { 404 struct kex *kex = ssh->kex; 405 int r; 406 407 /* 408 * if _ssh_read_banner() cannot parse a full version string 409 * it will return NULL and we end up calling it again. 410 */ 411 412 r = 0; 413 if (kex->server) { 414 if (kex->server_version_string == NULL) 415 r = _ssh_send_banner(ssh, &kex->server_version_string); 416 if (r == 0 && 417 kex->server_version_string != NULL && 418 kex->client_version_string == NULL) 419 r = _ssh_read_banner(ssh, &kex->client_version_string); 420 } else { 421 if (kex->server_version_string == NULL) 422 r = _ssh_read_banner(ssh, &kex->server_version_string); 423 if (r == 0 && 424 kex->server_version_string != NULL && 425 kex->client_version_string == NULL) 426 r = _ssh_send_banner(ssh, &kex->client_version_string); 427 } 428 if (r != 0) 429 return r; 430 /* start initial kex as soon as we have exchanged the banners */ 431 if (kex->server_version_string != NULL && 432 kex->client_version_string != NULL) { 433 if ((r = _ssh_order_hostkeyalgs(ssh)) != 0 || 434 (r = kex_send_kexinit(ssh)) != 0) 435 return r; 436 } 437 return 0; 438 } 439 440 struct sshkey * 441 _ssh_host_public_key(int type, int nid, struct ssh *ssh) 442 { 443 struct key_entry *k; 444 445 debug3("%s: need %d", __func__, type); 446 TAILQ_FOREACH(k, &ssh->public_keys, next) { 447 debug3("%s: check %s", __func__, sshkey_type(k->key)); 448 if (k->key->type == type && 449 (type != KEY_ECDSA || k->key->ecdsa_nid == nid)) 450 return (k->key); 451 } 452 return (NULL); 453 } 454 455 struct sshkey * 456 _ssh_host_private_key(int type, int nid, struct ssh *ssh) 457 { 458 struct key_entry *k; 459 460 debug3("%s: need %d", __func__, type); 461 TAILQ_FOREACH(k, &ssh->private_keys, next) { 462 debug3("%s: check %s", __func__, sshkey_type(k->key)); 463 if (k->key->type == type && 464 (type != KEY_ECDSA || k->key->ecdsa_nid == nid)) 465 return (k->key); 466 } 467 return (NULL); 468 } 469 470 int 471 _ssh_verify_host_key(struct sshkey *hostkey, struct ssh *ssh) 472 { 473 struct key_entry *k; 474 475 debug3("%s: need %s", __func__, sshkey_type(hostkey)); 476 TAILQ_FOREACH(k, &ssh->public_keys, next) { 477 debug3("%s: check %s", __func__, sshkey_type(k->key)); 478 if (sshkey_equal_public(hostkey, k->key)) 479 return (0); /* ok */ 480 } 481 return (-1); /* failed */ 482 } 483 484 /* offer hostkey algorithms in kexinit depending on registered keys */ 485 int 486 _ssh_order_hostkeyalgs(struct ssh *ssh) 487 { 488 struct key_entry *k; 489 char *orig, *avail, *oavail = NULL, *alg, *replace = NULL; 490 char **proposal; 491 size_t maxlen; 492 int ktype, r; 493 494 /* XXX we de-serialize ssh->kex->my, modify it, and change it */ 495 if ((r = kex_buf2prop(ssh->kex->my, NULL, &proposal)) != 0) 496 return r; 497 orig = proposal[PROPOSAL_SERVER_HOST_KEY_ALGS]; 498 if ((oavail = avail = strdup(orig)) == NULL) { 499 r = SSH_ERR_ALLOC_FAIL; 500 goto out; 501 } 502 maxlen = strlen(avail) + 1; 503 if ((replace = calloc(1, maxlen)) == NULL) { 504 r = SSH_ERR_ALLOC_FAIL; 505 goto out; 506 } 507 *replace = '\0'; 508 while ((alg = strsep(&avail, ",")) && *alg != '\0') { 509 if ((ktype = sshkey_type_from_name(alg)) == KEY_UNSPEC) 510 continue; 511 TAILQ_FOREACH(k, &ssh->public_keys, next) { 512 if (k->key->type == ktype || 513 (sshkey_is_cert(k->key) && k->key->type == 514 sshkey_type_plain(ktype))) { 515 if (*replace != '\0') 516 strlcat(replace, ",", maxlen); 517 strlcat(replace, alg, maxlen); 518 break; 519 } 520 } 521 } 522 if (*replace != '\0') { 523 debug2("%s: orig/%d %s", __func__, ssh->kex->server, orig); 524 debug2("%s: replace/%d %s", __func__, ssh->kex->server, replace); 525 free(orig); 526 proposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = replace; 527 replace = NULL; /* owned by proposal */ 528 r = kex_prop2buf(ssh->kex->my, proposal); 529 } 530 out: 531 free(oavail); 532 free(replace); 533 kex_prop_free(proposal); 534 return r; 535 } 536 537 int 538 _ssh_host_key_sign(struct sshkey *privkey, struct sshkey *pubkey, 539 u_char **signature, size_t *slen, const u_char *data, size_t dlen, 540 const char *alg, u_int compat) 541 { 542 return sshkey_sign(privkey, signature, slen, data, dlen, alg, compat); 543 } 544