1 /* $NetBSD: ssh_api.c,v 1.4 2016/08/02 13:45:12 christos Exp $ */ 2 /* $OpenBSD: ssh_api.c,v 1.7 2016/05/04 14:22:33 markus 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 1.4 2016/08/02 13:45:12 christos Exp $"); 21 22 #include "ssh1.h" /* For SSH_MSG_NONE */ 23 #include "ssh_api.h" 24 #include "compat.h" 25 #include "log.h" 26 #include "authfile.h" 27 #include "sshkey.h" 28 #include "misc.h" 29 #include "ssh2.h" 30 #include "version.h" 31 #include "myproposal.h" 32 #include "ssherr.h" 33 #include "sshbuf.h" 34 35 #include <string.h> 36 37 int _ssh_exchange_banner(struct ssh *); 38 int _ssh_send_banner(struct ssh *, char **); 39 int _ssh_read_banner(struct ssh *, char **); 40 int _ssh_order_hostkeyalgs(struct ssh *); 41 int _ssh_verify_host_key(struct sshkey *, struct ssh *); 42 struct sshkey *_ssh_host_public_key(int, int, struct ssh *); 43 struct sshkey *_ssh_host_private_key(int, int, struct ssh *); 44 int _ssh_host_key_sign(struct sshkey *, struct sshkey *, 45 u_char **, size_t *, const u_char *, size_t, const char *, u_int); 46 47 /* 48 * stubs for the server side implementation of kex. 49 * disable privsep so our stubs will never be called. 50 */ 51 int use_privsep = 0; 52 int mm_sshkey_sign(struct sshkey *, u_char **, u_int *, 53 u_char *, u_int, char *, u_int); 54 DH *mm_choose_dh(int, int, int); 55 56 /* Define these two variables here so that they are part of the library */ 57 u_char *session_id2 = NULL; 58 u_int session_id2_len = 0; 59 60 int 61 mm_sshkey_sign(struct sshkey *key, u_char **sigp, u_int *lenp, 62 u_char *data, u_int datalen, char *alg, u_int compat) 63 { 64 return (-1); 65 } 66 67 DH * 68 mm_choose_dh(int min, int nbits, int max) 69 { 70 return (NULL); 71 } 72 73 /* API */ 74 75 int 76 ssh_init(struct ssh **sshp, int is_server, struct kex_params *kex_params) 77 { 78 const char *myproposal[PROPOSAL_MAX] = { KEX_CLIENT }; 79 struct ssh *ssh; 80 const char **proposal; 81 static int called; 82 int r; 83 84 if (!called) { 85 OpenSSL_add_all_algorithms(); 86 called = 1; 87 } 88 89 if ((ssh = ssh_packet_set_connection(NULL, -1, -1)) == NULL) 90 return SSH_ERR_ALLOC_FAIL; 91 if (is_server) 92 ssh_packet_set_server(ssh); 93 94 /* Initialize key exchange */ 95 proposal = kex_params ? (const char **)(void *)kex_params->proposal : myproposal; 96 if ((r = kex_new(ssh, proposal, &ssh->kex)) != 0) { 97 ssh_free(ssh); 98 return r; 99 } 100 ssh->kex->server = is_server; 101 if (is_server) { 102 #ifdef WITH_OPENSSL 103 ssh->kex->kex[KEX_DH_GRP1_SHA1] = kexdh_server; 104 ssh->kex->kex[KEX_DH_GRP14_SHA1] = kexdh_server; 105 ssh->kex->kex[KEX_DH_GRP14_SHA256] = kexdh_server; 106 ssh->kex->kex[KEX_DH_GRP16_SHA512] = kexdh_server; 107 ssh->kex->kex[KEX_DH_GRP18_SHA512] = kexdh_server; 108 ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_server; 109 ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_server; 110 ssh->kex->kex[KEX_ECDH_SHA2] = kexecdh_server; 111 #endif /* WITH_OPENSSL */ 112 ssh->kex->kex[KEX_C25519_SHA256] = kexc25519_server; 113 ssh->kex->load_host_public_key=&_ssh_host_public_key; 114 ssh->kex->load_host_private_key=&_ssh_host_private_key; 115 ssh->kex->sign=&_ssh_host_key_sign; 116 } else { 117 #ifdef WITH_OPENSSL 118 ssh->kex->kex[KEX_DH_GRP1_SHA1] = kexdh_client; 119 ssh->kex->kex[KEX_DH_GRP14_SHA1] = kexdh_client; 120 ssh->kex->kex[KEX_DH_GRP14_SHA256] = kexdh_client; 121 ssh->kex->kex[KEX_DH_GRP16_SHA512] = kexdh_client; 122 ssh->kex->kex[KEX_DH_GRP18_SHA512] = kexdh_client; 123 ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_client; 124 ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_client; 125 ssh->kex->kex[KEX_ECDH_SHA2] = kexecdh_client; 126 #endif /* WITH_OPENSSL */ 127 ssh->kex->kex[KEX_C25519_SHA256] = kexc25519_client; 128 ssh->kex->verify_host_key =&_ssh_verify_host_key; 129 } 130 *sshp = ssh; 131 return 0; 132 } 133 134 void 135 ssh_free(struct ssh *ssh) 136 { 137 struct key_entry *k; 138 139 ssh_packet_close(ssh); 140 /* 141 * we've only created the public keys variants in case we 142 * are a acting as a server. 143 */ 144 while ((k = TAILQ_FIRST(&ssh->public_keys)) != NULL) { 145 TAILQ_REMOVE(&ssh->public_keys, k, next); 146 if (ssh->kex && ssh->kex->server) 147 sshkey_free(k->key); 148 free(k); 149 } 150 while ((k = TAILQ_FIRST(&ssh->private_keys)) != NULL) { 151 TAILQ_REMOVE(&ssh->private_keys, k, next); 152 free(k); 153 } 154 if (ssh->kex) 155 kex_free(ssh->kex); 156 free(ssh); 157 } 158 159 void 160 ssh_set_app_data(struct ssh *ssh, void *app_data) 161 { 162 ssh->app_data = app_data; 163 } 164 165 void * 166 ssh_get_app_data(struct ssh *ssh) 167 { 168 return ssh->app_data; 169 } 170 171 /* Returns < 0 on error, 0 otherwise */ 172 int 173 ssh_add_hostkey(struct ssh *ssh, struct sshkey *key) 174 { 175 struct sshkey *pubkey = NULL; 176 struct key_entry *k = NULL, *k_prv = NULL; 177 int r; 178 179 if (ssh->kex->server) { 180 if ((r = sshkey_from_private(key, &pubkey)) != 0) 181 return r; 182 if ((k = malloc(sizeof(*k))) == NULL || 183 (k_prv = malloc(sizeof(*k_prv))) == NULL) { 184 free(k); 185 sshkey_free(pubkey); 186 return SSH_ERR_ALLOC_FAIL; 187 } 188 k_prv->key = key; 189 TAILQ_INSERT_TAIL(&ssh->private_keys, k_prv, next); 190 191 /* add the public key, too */ 192 k->key = pubkey; 193 TAILQ_INSERT_TAIL(&ssh->public_keys, k, next); 194 r = 0; 195 } else { 196 if ((k = malloc(sizeof(*k))) == NULL) 197 return SSH_ERR_ALLOC_FAIL; 198 k->key = key; 199 TAILQ_INSERT_TAIL(&ssh->public_keys, k, next); 200 r = 0; 201 } 202 203 return r; 204 } 205 206 int 207 ssh_set_verify_host_key_callback(struct ssh *ssh, 208 int (*cb)(struct sshkey *, struct ssh *)) 209 { 210 if (cb == NULL || ssh->kex == NULL) 211 return SSH_ERR_INVALID_ARGUMENT; 212 213 ssh->kex->verify_host_key = cb; 214 215 return 0; 216 } 217 218 int 219 ssh_input_append(struct ssh *ssh, const u_char *data, size_t len) 220 { 221 return sshbuf_put(ssh_packet_get_input(ssh), data, len); 222 } 223 224 int 225 ssh_packet_next(struct ssh *ssh, u_char *typep) 226 { 227 int r; 228 u_int32_t seqnr; 229 u_char type; 230 231 /* 232 * Try to read a packet. Return SSH_MSG_NONE if no packet or not 233 * enough data. 234 */ 235 *typep = SSH_MSG_NONE; 236 if (ssh->kex->client_version_string == NULL || 237 ssh->kex->server_version_string == NULL) 238 return _ssh_exchange_banner(ssh); 239 /* 240 * If we enough data and a dispatch function then 241 * call the function and get the next packet. 242 * Otherwise return the packet type to the caller so it 243 * can decide how to go on. 244 * 245 * We will only call the dispatch function for: 246 * 20-29 Algorithm negotiation 247 * 30-49 Key exchange method specific (numbers can be reused for 248 * different authentication methods) 249 */ 250 for (;;) { 251 if ((r = ssh_packet_read_poll2(ssh, &type, &seqnr)) != 0) 252 return r; 253 if (type > 0 && type < DISPATCH_MAX && 254 type >= SSH2_MSG_KEXINIT && type <= SSH2_MSG_TRANSPORT_MAX && 255 ssh->dispatch[type] != NULL) { 256 if ((r = (*ssh->dispatch[type])(type, seqnr, ssh)) != 0) 257 return r; 258 } else { 259 *typep = type; 260 return 0; 261 } 262 } 263 } 264 265 const u_char * 266 ssh_packet_payload(struct ssh *ssh, size_t *lenp) 267 { 268 return sshpkt_ptr(ssh, lenp); 269 } 270 271 int 272 ssh_packet_put(struct ssh *ssh, int type, const u_char *data, size_t len) 273 { 274 int r; 275 276 if ((r = sshpkt_start(ssh, type)) != 0 || 277 (r = sshpkt_put(ssh, data, len)) != 0 || 278 (r = sshpkt_send(ssh)) != 0) 279 return r; 280 return 0; 281 } 282 283 const u_char * 284 ssh_output_ptr(struct ssh *ssh, size_t *len) 285 { 286 struct sshbuf *output = ssh_packet_get_output(ssh); 287 288 *len = sshbuf_len(output); 289 return sshbuf_ptr(output); 290 } 291 292 int 293 ssh_output_consume(struct ssh *ssh, size_t len) 294 { 295 return sshbuf_consume(ssh_packet_get_output(ssh), len); 296 } 297 298 int 299 ssh_output_space(struct ssh *ssh, size_t len) 300 { 301 return (0 == sshbuf_check_reserve(ssh_packet_get_output(ssh), len)); 302 } 303 304 int 305 ssh_input_space(struct ssh *ssh, size_t len) 306 { 307 return (0 == sshbuf_check_reserve(ssh_packet_get_input(ssh), len)); 308 } 309 310 /* Read other side's version identification. */ 311 int 312 _ssh_read_banner(struct ssh *ssh, char **bannerp) 313 { 314 struct sshbuf *input; 315 const char *s; 316 char buf[256], remote_version[256]; /* must be same size! */ 317 const char *mismatch = "Protocol mismatch.\r\n"; 318 int r, remote_major, remote_minor; 319 size_t i, n, j, len; 320 321 *bannerp = NULL; 322 input = ssh_packet_get_input(ssh); 323 len = sshbuf_len(input); 324 s = (const char *)sshbuf_ptr(input); 325 for (j = n = 0;;) { 326 for (i = 0; i < sizeof(buf) - 1; i++) { 327 if (j >= len) 328 return (0); 329 buf[i] = s[j++]; 330 if (buf[i] == '\r') { 331 buf[i] = '\n'; 332 buf[i + 1] = 0; 333 continue; /**XXX wait for \n */ 334 } 335 if (buf[i] == '\n') { 336 buf[i + 1] = 0; 337 break; 338 } 339 } 340 buf[sizeof(buf) - 1] = 0; 341 if (strncmp(buf, "SSH-", 4) == 0) 342 break; 343 debug("ssh_exchange_identification: %s", buf); 344 if (ssh->kex->server || ++n > 65536) { 345 if ((r = sshbuf_put(ssh_packet_get_output(ssh), 346 mismatch, strlen(mismatch))) != 0) 347 return r; 348 return SSH_ERR_NO_PROTOCOL_VERSION; 349 } 350 } 351 if ((r = sshbuf_consume(input, j)) != 0) 352 return r; 353 354 /* 355 * Check that the versions match. In future this might accept 356 * several versions and set appropriate flags to handle them. 357 */ 358 if (sscanf(buf, "SSH-%d.%d-%[^\n]\n", 359 &remote_major, &remote_minor, remote_version) != 3) 360 return SSH_ERR_INVALID_FORMAT; 361 debug("Remote protocol version %d.%d, remote software version %.100s", 362 remote_major, remote_minor, remote_version); 363 364 ssh->compat = compat_datafellows(remote_version); 365 if (remote_major == 1 && remote_minor == 99) { 366 remote_major = 2; 367 remote_minor = 0; 368 } 369 if (remote_major != 2) 370 return SSH_ERR_PROTOCOL_MISMATCH; 371 enable_compat20(); 372 chop(buf); 373 debug("Remote version string %.100s", buf); 374 if ((*bannerp = strdup(buf)) == NULL) 375 return SSH_ERR_ALLOC_FAIL; 376 return 0; 377 } 378 379 /* Send our own protocol version identification. */ 380 int 381 _ssh_send_banner(struct ssh *ssh, char **bannerp) 382 { 383 char buf[256]; 384 int r; 385 386 snprintf(buf, sizeof buf, "SSH-2.0-%.100s\r\n", SSH_VERSION); 387 if ((r = sshbuf_put(ssh_packet_get_output(ssh), buf, strlen(buf))) != 0) 388 return r; 389 chop(buf); 390 debug("Local version string %.100s", buf); 391 if ((*bannerp = strdup(buf)) == NULL) 392 return SSH_ERR_ALLOC_FAIL; 393 return 0; 394 } 395 396 int 397 _ssh_exchange_banner(struct ssh *ssh) 398 { 399 struct kex *kex = ssh->kex; 400 int r; 401 402 /* 403 * if _ssh_read_banner() cannot parse a full version string 404 * it will return NULL and we end up calling it again. 405 */ 406 407 r = 0; 408 if (kex->server) { 409 if (kex->server_version_string == NULL) 410 r = _ssh_send_banner(ssh, &kex->server_version_string); 411 if (r == 0 && 412 kex->server_version_string != NULL && 413 kex->client_version_string == NULL) 414 r = _ssh_read_banner(ssh, &kex->client_version_string); 415 } else { 416 if (kex->server_version_string == NULL) 417 r = _ssh_read_banner(ssh, &kex->server_version_string); 418 if (r == 0 && 419 kex->server_version_string != NULL && 420 kex->client_version_string == NULL) 421 r = _ssh_send_banner(ssh, &kex->client_version_string); 422 } 423 if (r != 0) 424 return r; 425 /* start initial kex as soon as we have exchanged the banners */ 426 if (kex->server_version_string != NULL && 427 kex->client_version_string != NULL) { 428 if ((r = _ssh_order_hostkeyalgs(ssh)) != 0 || 429 (r = kex_send_kexinit(ssh)) != 0) 430 return r; 431 } 432 return 0; 433 } 434 435 struct sshkey * 436 _ssh_host_public_key(int type, int nid, struct ssh *ssh) 437 { 438 struct key_entry *k; 439 440 debug3("%s: need %d", __func__, type); 441 TAILQ_FOREACH(k, &ssh->public_keys, next) { 442 debug3("%s: check %s", __func__, sshkey_type(k->key)); 443 if (k->key->type == type && 444 (type != KEY_ECDSA || k->key->ecdsa_nid == nid)) 445 return (k->key); 446 } 447 return (NULL); 448 } 449 450 struct sshkey * 451 _ssh_host_private_key(int type, int nid, struct ssh *ssh) 452 { 453 struct key_entry *k; 454 455 debug3("%s: need %d", __func__, type); 456 TAILQ_FOREACH(k, &ssh->private_keys, next) { 457 debug3("%s: check %s", __func__, sshkey_type(k->key)); 458 if (k->key->type == type && 459 (type != KEY_ECDSA || k->key->ecdsa_nid == nid)) 460 return (k->key); 461 } 462 return (NULL); 463 } 464 465 int 466 _ssh_verify_host_key(struct sshkey *hostkey, struct ssh *ssh) 467 { 468 struct key_entry *k; 469 470 debug3("%s: need %s", __func__, sshkey_type(hostkey)); 471 TAILQ_FOREACH(k, &ssh->public_keys, next) { 472 debug3("%s: check %s", __func__, sshkey_type(k->key)); 473 if (sshkey_equal_public(hostkey, k->key)) 474 return (0); /* ok */ 475 } 476 return (-1); /* failed */ 477 } 478 479 /* offer hostkey algorithms in kexinit depending on registered keys */ 480 int 481 _ssh_order_hostkeyalgs(struct ssh *ssh) 482 { 483 struct key_entry *k; 484 char *orig, *avail, *oavail = NULL, *alg, *replace = NULL; 485 char **proposal; 486 size_t maxlen; 487 int ktype, r; 488 489 /* XXX we de-serialize ssh->kex->my, modify it, and change it */ 490 if ((r = kex_buf2prop(ssh->kex->my, NULL, &proposal)) != 0) 491 return r; 492 orig = proposal[PROPOSAL_SERVER_HOST_KEY_ALGS]; 493 if ((oavail = avail = strdup(orig)) == NULL) { 494 r = SSH_ERR_ALLOC_FAIL; 495 goto out; 496 } 497 maxlen = strlen(avail) + 1; 498 if ((replace = calloc(1, maxlen)) == NULL) { 499 r = SSH_ERR_ALLOC_FAIL; 500 goto out; 501 } 502 *replace = '\0'; 503 while ((alg = strsep(&avail, ",")) && *alg != '\0') { 504 if ((ktype = sshkey_type_from_name(alg)) == KEY_UNSPEC) 505 continue; 506 TAILQ_FOREACH(k, &ssh->public_keys, next) { 507 if (k->key->type == ktype || 508 (sshkey_is_cert(k->key) && k->key->type == 509 sshkey_type_plain(ktype))) { 510 if (*replace != '\0') 511 strlcat(replace, ",", maxlen); 512 strlcat(replace, alg, maxlen); 513 break; 514 } 515 } 516 } 517 if (*replace != '\0') { 518 debug2("%s: orig/%d %s", __func__, ssh->kex->server, orig); 519 debug2("%s: replace/%d %s", __func__, ssh->kex->server, replace); 520 free(orig); 521 proposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = replace; 522 replace = NULL; /* owned by proposal */ 523 r = kex_prop2buf(ssh->kex->my, (const char **)(void *)proposal); 524 } 525 out: 526 free(oavail); 527 free(replace); 528 kex_prop_free(proposal); 529 return r; 530 } 531 532 int 533 _ssh_host_key_sign(struct sshkey *privkey, struct sshkey *pubkey, 534 u_char **signature, size_t *slen, const u_char *data, size_t dlen, 535 const char *alg, u_int compat) 536 { 537 return sshkey_sign(privkey, signature, slen, data, dlen, alg, compat); 538 } 539