1 /* $NetBSD: ssh_api.c,v 1.7 2017/10/07 19:39:19 christos Exp $ */ 2 /* $OpenBSD: ssh_api.c,v 1.8 2017/04/30 23:13:25 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 1.7 2017/10/07 19:39:19 christos Exp $"); 21 22 #include "ssh_api.h" 23 #include "compat.h" 24 #include "log.h" 25 #include "authfile.h" 26 #include "sshkey.h" 27 #include "misc.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 const char *myproposal[PROPOSAL_MAX] = { KEX_CLIENT }; 78 struct ssh *ssh; 79 const char **proposal; 80 static int called; 81 int r; 82 83 if (!called) { 84 OpenSSL_add_all_algorithms(); 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 ? (const char **)(void *)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 ssh->kex->kex[KEX_ECDH_SHA2] = kexecdh_server; 110 #endif /* WITH_OPENSSL */ 111 ssh->kex->kex[KEX_C25519_SHA256] = kexc25519_server; 112 ssh->kex->load_host_public_key=&_ssh_host_public_key; 113 ssh->kex->load_host_private_key=&_ssh_host_private_key; 114 ssh->kex->sign=&_ssh_host_key_sign; 115 } else { 116 #ifdef WITH_OPENSSL 117 ssh->kex->kex[KEX_DH_GRP1_SHA1] = kexdh_client; 118 ssh->kex->kex[KEX_DH_GRP14_SHA1] = kexdh_client; 119 ssh->kex->kex[KEX_DH_GRP14_SHA256] = kexdh_client; 120 ssh->kex->kex[KEX_DH_GRP16_SHA512] = kexdh_client; 121 ssh->kex->kex[KEX_DH_GRP18_SHA512] = kexdh_client; 122 ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_client; 123 ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_client; 124 ssh->kex->kex[KEX_ECDH_SHA2] = kexecdh_client; 125 #endif /* WITH_OPENSSL */ 126 ssh->kex->kex[KEX_C25519_SHA256] = kexc25519_client; 127 ssh->kex->verify_host_key =&_ssh_verify_host_key; 128 } 129 *sshp = ssh; 130 return 0; 131 } 132 133 void 134 ssh_free(struct ssh *ssh) 135 { 136 struct key_entry *k; 137 138 ssh_packet_close(ssh); 139 /* 140 * we've only created the public keys variants in case we 141 * are a acting as a server. 142 */ 143 while ((k = TAILQ_FIRST(&ssh->public_keys)) != NULL) { 144 TAILQ_REMOVE(&ssh->public_keys, k, next); 145 if (ssh->kex && ssh->kex->server) 146 sshkey_free(k->key); 147 free(k); 148 } 149 while ((k = TAILQ_FIRST(&ssh->private_keys)) != NULL) { 150 TAILQ_REMOVE(&ssh->private_keys, k, next); 151 free(k); 152 } 153 if (ssh->kex) 154 kex_free(ssh->kex); 155 free(ssh); 156 } 157 158 void 159 ssh_set_app_data(struct ssh *ssh, void *app_data) 160 { 161 ssh->app_data = app_data; 162 } 163 164 void * 165 ssh_get_app_data(struct ssh *ssh) 166 { 167 return ssh->app_data; 168 } 169 170 /* Returns < 0 on error, 0 otherwise */ 171 int 172 ssh_add_hostkey(struct ssh *ssh, struct sshkey *key) 173 { 174 struct sshkey *pubkey = NULL; 175 struct key_entry *k = NULL, *k_prv = NULL; 176 int r; 177 178 if (ssh->kex->server) { 179 if ((r = sshkey_from_private(key, &pubkey)) != 0) 180 return r; 181 if ((k = malloc(sizeof(*k))) == NULL || 182 (k_prv = malloc(sizeof(*k_prv))) == NULL) { 183 free(k); 184 sshkey_free(pubkey); 185 return SSH_ERR_ALLOC_FAIL; 186 } 187 k_prv->key = key; 188 TAILQ_INSERT_TAIL(&ssh->private_keys, k_prv, next); 189 190 /* add the public key, too */ 191 k->key = pubkey; 192 TAILQ_INSERT_TAIL(&ssh->public_keys, k, next); 193 r = 0; 194 } else { 195 if ((k = malloc(sizeof(*k))) == NULL) 196 return SSH_ERR_ALLOC_FAIL; 197 k->key = key; 198 TAILQ_INSERT_TAIL(&ssh->public_keys, k, next); 199 r = 0; 200 } 201 202 return r; 203 } 204 205 int 206 ssh_set_verify_host_key_callback(struct ssh *ssh, 207 int (*cb)(struct sshkey *, struct ssh *)) 208 { 209 if (cb == NULL || ssh->kex == NULL) 210 return SSH_ERR_INVALID_ARGUMENT; 211 212 ssh->kex->verify_host_key = cb; 213 214 return 0; 215 } 216 217 int 218 ssh_input_append(struct ssh *ssh, const u_char *data, size_t len) 219 { 220 return sshbuf_put(ssh_packet_get_input(ssh), data, len); 221 } 222 223 int 224 ssh_packet_next(struct ssh *ssh, u_char *typep) 225 { 226 int r; 227 u_int32_t seqnr; 228 u_char type; 229 230 /* 231 * Try to read a packet. Return SSH_MSG_NONE if no packet or not 232 * enough data. 233 */ 234 *typep = SSH_MSG_NONE; 235 if (ssh->kex->client_version_string == NULL || 236 ssh->kex->server_version_string == NULL) 237 return _ssh_exchange_banner(ssh); 238 /* 239 * If we enough data and a dispatch function then 240 * call the function and get the next packet. 241 * Otherwise return the packet type to the caller so it 242 * can decide how to go on. 243 * 244 * We will only call the dispatch function for: 245 * 20-29 Algorithm negotiation 246 * 30-49 Key exchange method specific (numbers can be reused for 247 * different authentication methods) 248 */ 249 for (;;) { 250 if ((r = ssh_packet_read_poll2(ssh, &type, &seqnr)) != 0) 251 return r; 252 if (type > 0 && type < DISPATCH_MAX && 253 type >= SSH2_MSG_KEXINIT && type <= SSH2_MSG_TRANSPORT_MAX && 254 ssh->dispatch[type] != NULL) { 255 if ((r = (*ssh->dispatch[type])(type, seqnr, ssh)) != 0) 256 return r; 257 } else { 258 *typep = type; 259 return 0; 260 } 261 } 262 } 263 264 const u_char * 265 ssh_packet_payload(struct ssh *ssh, size_t *lenp) 266 { 267 return sshpkt_ptr(ssh, lenp); 268 } 269 270 int 271 ssh_packet_put(struct ssh *ssh, int type, const u_char *data, size_t len) 272 { 273 int r; 274 275 if ((r = sshpkt_start(ssh, type)) != 0 || 276 (r = sshpkt_put(ssh, data, len)) != 0 || 277 (r = sshpkt_send(ssh)) != 0) 278 return r; 279 return 0; 280 } 281 282 const u_char * 283 ssh_output_ptr(struct ssh *ssh, size_t *len) 284 { 285 struct sshbuf *output = ssh_packet_get_output(ssh); 286 287 *len = sshbuf_len(output); 288 return sshbuf_ptr(output); 289 } 290 291 int 292 ssh_output_consume(struct ssh *ssh, size_t len) 293 { 294 return sshbuf_consume(ssh_packet_get_output(ssh), len); 295 } 296 297 int 298 ssh_output_space(struct ssh *ssh, size_t len) 299 { 300 return (0 == sshbuf_check_reserve(ssh_packet_get_output(ssh), len)); 301 } 302 303 int 304 ssh_input_space(struct ssh *ssh, size_t len) 305 { 306 return (0 == sshbuf_check_reserve(ssh_packet_get_input(ssh), len)); 307 } 308 309 /* Read other side's version identification. */ 310 int 311 _ssh_read_banner(struct ssh *ssh, char **bannerp) 312 { 313 struct sshbuf *input; 314 const char *s; 315 char buf[256], remote_version[256]; /* must be same size! */ 316 const char *mismatch = "Protocol mismatch.\r\n"; 317 int r, remote_major, remote_minor; 318 size_t i, n, j, len; 319 320 *bannerp = NULL; 321 input = ssh_packet_get_input(ssh); 322 len = sshbuf_len(input); 323 s = (const char *)sshbuf_ptr(input); 324 for (j = n = 0;;) { 325 for (i = 0; i < sizeof(buf) - 1; i++) { 326 if (j >= len) 327 return (0); 328 buf[i] = s[j++]; 329 if (buf[i] == '\r') { 330 buf[i] = '\n'; 331 buf[i + 1] = 0; 332 continue; /**XXX wait for \n */ 333 } 334 if (buf[i] == '\n') { 335 buf[i + 1] = 0; 336 break; 337 } 338 } 339 buf[sizeof(buf) - 1] = 0; 340 if (strncmp(buf, "SSH-", 4) == 0) 341 break; 342 debug("ssh_exchange_identification: %s", buf); 343 if (ssh->kex->server || ++n > 65536) { 344 if ((r = sshbuf_put(ssh_packet_get_output(ssh), 345 mismatch, strlen(mismatch))) != 0) 346 return r; 347 return SSH_ERR_NO_PROTOCOL_VERSION; 348 } 349 } 350 if ((r = sshbuf_consume(input, j)) != 0) 351 return r; 352 353 /* 354 * Check that the versions match. In future this might accept 355 * several versions and set appropriate flags to handle them. 356 */ 357 if (sscanf(buf, "SSH-%d.%d-%[^\n]\n", 358 &remote_major, &remote_minor, remote_version) != 3) 359 return SSH_ERR_INVALID_FORMAT; 360 debug("Remote protocol version %d.%d, remote software version %.100s", 361 remote_major, remote_minor, remote_version); 362 363 ssh->compat = compat_datafellows(remote_version); 364 if (remote_major == 1 && remote_minor == 99) { 365 remote_major = 2; 366 remote_minor = 0; 367 } 368 if (remote_major != 2) 369 return SSH_ERR_PROTOCOL_MISMATCH; 370 chop(buf); 371 debug("Remote version string %.100s", buf); 372 if ((*bannerp = strdup(buf)) == NULL) 373 return SSH_ERR_ALLOC_FAIL; 374 return 0; 375 } 376 377 /* Send our own protocol version identification. */ 378 int 379 _ssh_send_banner(struct ssh *ssh, char **bannerp) 380 { 381 char buf[256]; 382 int r; 383 384 snprintf(buf, sizeof buf, "SSH-2.0-%.100s\r\n", SSH_VERSION); 385 if ((r = sshbuf_put(ssh_packet_get_output(ssh), buf, strlen(buf))) != 0) 386 return r; 387 chop(buf); 388 debug("Local version string %.100s", buf); 389 if ((*bannerp = strdup(buf)) == NULL) 390 return SSH_ERR_ALLOC_FAIL; 391 return 0; 392 } 393 394 int 395 _ssh_exchange_banner(struct ssh *ssh) 396 { 397 struct kex *kex = ssh->kex; 398 int r; 399 400 /* 401 * if _ssh_read_banner() cannot parse a full version string 402 * it will return NULL and we end up calling it again. 403 */ 404 405 r = 0; 406 if (kex->server) { 407 if (kex->server_version_string == NULL) 408 r = _ssh_send_banner(ssh, &kex->server_version_string); 409 if (r == 0 && 410 kex->server_version_string != NULL && 411 kex->client_version_string == NULL) 412 r = _ssh_read_banner(ssh, &kex->client_version_string); 413 } else { 414 if (kex->server_version_string == NULL) 415 r = _ssh_read_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_send_banner(ssh, &kex->client_version_string); 420 } 421 if (r != 0) 422 return r; 423 /* start initial kex as soon as we have exchanged the banners */ 424 if (kex->server_version_string != NULL && 425 kex->client_version_string != NULL) { 426 if ((r = _ssh_order_hostkeyalgs(ssh)) != 0 || 427 (r = kex_send_kexinit(ssh)) != 0) 428 return r; 429 } 430 return 0; 431 } 432 433 struct sshkey * 434 _ssh_host_public_key(int type, int nid, struct ssh *ssh) 435 { 436 struct key_entry *k; 437 438 debug3("%s: need %d", __func__, type); 439 TAILQ_FOREACH(k, &ssh->public_keys, next) { 440 debug3("%s: check %s", __func__, sshkey_type(k->key)); 441 if (k->key->type == type && 442 (type != KEY_ECDSA || k->key->ecdsa_nid == nid)) 443 return (k->key); 444 } 445 return (NULL); 446 } 447 448 struct sshkey * 449 _ssh_host_private_key(int type, int nid, struct ssh *ssh) 450 { 451 struct key_entry *k; 452 453 debug3("%s: need %d", __func__, type); 454 TAILQ_FOREACH(k, &ssh->private_keys, next) { 455 debug3("%s: check %s", __func__, sshkey_type(k->key)); 456 if (k->key->type == type && 457 (type != KEY_ECDSA || k->key->ecdsa_nid == nid)) 458 return (k->key); 459 } 460 return (NULL); 461 } 462 463 int 464 _ssh_verify_host_key(struct sshkey *hostkey, struct ssh *ssh) 465 { 466 struct key_entry *k; 467 468 debug3("%s: need %s", __func__, sshkey_type(hostkey)); 469 TAILQ_FOREACH(k, &ssh->public_keys, next) { 470 debug3("%s: check %s", __func__, sshkey_type(k->key)); 471 if (sshkey_equal_public(hostkey, k->key)) 472 return (0); /* ok */ 473 } 474 return (-1); /* failed */ 475 } 476 477 /* offer hostkey algorithms in kexinit depending on registered keys */ 478 int 479 _ssh_order_hostkeyalgs(struct ssh *ssh) 480 { 481 struct key_entry *k; 482 char *orig, *avail, *oavail = NULL, *alg, *replace = NULL; 483 char **proposal; 484 size_t maxlen; 485 int ktype, r; 486 487 /* XXX we de-serialize ssh->kex->my, modify it, and change it */ 488 if ((r = kex_buf2prop(ssh->kex->my, NULL, &proposal)) != 0) 489 return r; 490 orig = proposal[PROPOSAL_SERVER_HOST_KEY_ALGS]; 491 if ((oavail = avail = strdup(orig)) == NULL) { 492 r = SSH_ERR_ALLOC_FAIL; 493 goto out; 494 } 495 maxlen = strlen(avail) + 1; 496 if ((replace = calloc(1, maxlen)) == NULL) { 497 r = SSH_ERR_ALLOC_FAIL; 498 goto out; 499 } 500 *replace = '\0'; 501 while ((alg = strsep(&avail, ",")) && *alg != '\0') { 502 if ((ktype = sshkey_type_from_name(alg)) == KEY_UNSPEC) 503 continue; 504 TAILQ_FOREACH(k, &ssh->public_keys, next) { 505 if (k->key->type == ktype || 506 (sshkey_is_cert(k->key) && k->key->type == 507 sshkey_type_plain(ktype))) { 508 if (*replace != '\0') 509 strlcat(replace, ",", maxlen); 510 strlcat(replace, alg, maxlen); 511 break; 512 } 513 } 514 } 515 if (*replace != '\0') { 516 debug2("%s: orig/%d %s", __func__, ssh->kex->server, orig); 517 debug2("%s: replace/%d %s", __func__, ssh->kex->server, replace); 518 free(orig); 519 proposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = replace; 520 replace = NULL; /* owned by proposal */ 521 r = kex_prop2buf(ssh->kex->my, (const char **)(void *)proposal); 522 } 523 out: 524 free(oavail); 525 free(replace); 526 kex_prop_free(proposal); 527 return r; 528 } 529 530 int 531 _ssh_host_key_sign(struct sshkey *privkey, struct sshkey *pubkey, 532 u_char **signature, size_t *slen, const u_char *data, size_t dlen, 533 const char *alg, u_int compat) 534 { 535 return sshkey_sign(privkey, signature, slen, data, dlen, alg, compat); 536 } 537