1 /* $OpenBSD: hostfile.c,v 1.57 2014/06/24 01:13:21 djm Exp $ */ 2 /* 3 * Author: Tatu Ylonen <ylo@cs.hut.fi> 4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 5 * All rights reserved 6 * Functions for manipulating the known hosts files. 7 * 8 * As far as I am concerned, the code I have written for this software 9 * can be used freely for any purpose. Any derived versions of this 10 * software must be clearly marked as such, and if the derived work is 11 * incompatible with the protocol description in the RFC file, it must be 12 * called by a name other than "ssh" or "Secure Shell". 13 * 14 * 15 * Copyright (c) 1999, 2000 Markus Friedl. All rights reserved. 16 * Copyright (c) 1999 Niels Provos. All rights reserved. 17 * 18 * Redistribution and use in source and binary forms, with or without 19 * modification, are permitted provided that the following conditions 20 * are met: 21 * 1. Redistributions of source code must retain the above copyright 22 * notice, this list of conditions and the following disclaimer. 23 * 2. Redistributions in binary form must reproduce the above copyright 24 * notice, this list of conditions and the following disclaimer in the 25 * documentation and/or other materials provided with the distribution. 26 * 27 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 28 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 29 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 30 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 31 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 32 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 33 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 34 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 35 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 36 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 37 */ 38 39 #include "includes.h" 40 41 #include <sys/types.h> 42 43 #include <netinet/in.h> 44 45 #include <resolv.h> 46 #include <stdarg.h> 47 #include <stdio.h> 48 #include <stdlib.h> 49 #include <string.h> 50 #include <stdarg.h> 51 52 #include "xmalloc.h" 53 #include "match.h" 54 #include "key.h" 55 #include "hostfile.h" 56 #include "log.h" 57 #include "misc.h" 58 #include "digest.h" 59 #include "hmac.h" 60 61 struct hostkeys { 62 struct hostkey_entry *entries; 63 u_int num_entries; 64 }; 65 66 static int 67 extract_salt(const char *s, u_int l, u_char *salt, size_t salt_len) 68 { 69 char *p, *b64salt; 70 u_int b64len; 71 int ret; 72 73 if (l < sizeof(HASH_MAGIC) - 1) { 74 debug2("extract_salt: string too short"); 75 return (-1); 76 } 77 if (strncmp(s, HASH_MAGIC, sizeof(HASH_MAGIC) - 1) != 0) { 78 debug2("extract_salt: invalid magic identifier"); 79 return (-1); 80 } 81 s += sizeof(HASH_MAGIC) - 1; 82 l -= sizeof(HASH_MAGIC) - 1; 83 if ((p = memchr(s, HASH_DELIM, l)) == NULL) { 84 debug2("extract_salt: missing salt termination character"); 85 return (-1); 86 } 87 88 b64len = p - s; 89 /* Sanity check */ 90 if (b64len == 0 || b64len > 1024) { 91 debug2("extract_salt: bad encoded salt length %u", b64len); 92 return (-1); 93 } 94 b64salt = xmalloc(1 + b64len); 95 memcpy(b64salt, s, b64len); 96 b64salt[b64len] = '\0'; 97 98 ret = __b64_pton(b64salt, salt, salt_len); 99 free(b64salt); 100 if (ret == -1) { 101 debug2("extract_salt: salt decode error"); 102 return (-1); 103 } 104 if (ret != (int)ssh_hmac_bytes(SSH_DIGEST_SHA1)) { 105 debug2("extract_salt: expected salt len %zd, got %d", 106 ssh_hmac_bytes(SSH_DIGEST_SHA1), ret); 107 return (-1); 108 } 109 110 return (0); 111 } 112 113 char * 114 host_hash(const char *host, const char *name_from_hostfile, u_int src_len) 115 { 116 struct ssh_hmac_ctx *ctx; 117 u_char salt[256], result[256]; 118 char uu_salt[512], uu_result[512]; 119 static char encoded[1024]; 120 u_int i, len; 121 122 len = ssh_digest_bytes(SSH_DIGEST_SHA1); 123 124 if (name_from_hostfile == NULL) { 125 /* Create new salt */ 126 for (i = 0; i < len; i++) 127 salt[i] = arc4random(); 128 } else { 129 /* Extract salt from known host entry */ 130 if (extract_salt(name_from_hostfile, src_len, salt, 131 sizeof(salt)) == -1) 132 return (NULL); 133 } 134 135 if ((ctx = ssh_hmac_start(SSH_DIGEST_SHA1)) == NULL || 136 ssh_hmac_init(ctx, salt, len) < 0 || 137 ssh_hmac_update(ctx, host, strlen(host)) < 0 || 138 ssh_hmac_final(ctx, result, sizeof(result))) 139 fatal("%s: ssh_hmac failed", __func__); 140 ssh_hmac_free(ctx); 141 142 if (__b64_ntop(salt, len, uu_salt, sizeof(uu_salt)) == -1 || 143 __b64_ntop(result, len, uu_result, sizeof(uu_result)) == -1) 144 fatal("%s: __b64_ntop failed", __func__); 145 146 snprintf(encoded, sizeof(encoded), "%s%s%c%s", HASH_MAGIC, uu_salt, 147 HASH_DELIM, uu_result); 148 149 return (encoded); 150 } 151 152 /* 153 * Parses an RSA (number of bits, e, n) or DSA key from a string. Moves the 154 * pointer over the key. Skips any whitespace at the beginning and at end. 155 */ 156 157 int 158 hostfile_read_key(char **cpp, int *bitsp, Key *ret) 159 { 160 char *cp; 161 162 /* Skip leading whitespace. */ 163 for (cp = *cpp; *cp == ' ' || *cp == '\t'; cp++) 164 ; 165 166 if (key_read(ret, &cp) != 1) 167 return 0; 168 169 /* Skip trailing whitespace. */ 170 for (; *cp == ' ' || *cp == '\t'; cp++) 171 ; 172 173 /* Return results. */ 174 *cpp = cp; 175 if (bitsp != NULL) { 176 if ((*bitsp = key_size(ret)) <= 0) 177 return 0; 178 } 179 return 1; 180 } 181 182 static int 183 hostfile_check_key(int bits, const Key *key, const char *host, 184 const char *filename, u_long linenum) 185 { 186 #ifdef WITH_SSH1 187 if (key == NULL || key->type != KEY_RSA1 || key->rsa == NULL) 188 return 1; 189 if (bits != BN_num_bits(key->rsa->n)) { 190 logit("Warning: %s, line %lu: keysize mismatch for host %s: " 191 "actual %d vs. announced %d.", 192 filename, linenum, host, BN_num_bits(key->rsa->n), bits); 193 logit("Warning: replace %d with %d in %s, line %lu.", 194 bits, BN_num_bits(key->rsa->n), filename, linenum); 195 } 196 #endif 197 return 1; 198 } 199 200 static HostkeyMarker 201 check_markers(char **cpp) 202 { 203 char marker[32], *sp, *cp = *cpp; 204 int ret = MRK_NONE; 205 206 while (*cp == '@') { 207 /* Only one marker is allowed */ 208 if (ret != MRK_NONE) 209 return MRK_ERROR; 210 /* Markers are terminated by whitespace */ 211 if ((sp = strchr(cp, ' ')) == NULL && 212 (sp = strchr(cp, '\t')) == NULL) 213 return MRK_ERROR; 214 /* Extract marker for comparison */ 215 if (sp <= cp + 1 || sp >= cp + sizeof(marker)) 216 return MRK_ERROR; 217 memcpy(marker, cp, sp - cp); 218 marker[sp - cp] = '\0'; 219 if (strcmp(marker, CA_MARKER) == 0) 220 ret = MRK_CA; 221 else if (strcmp(marker, REVOKE_MARKER) == 0) 222 ret = MRK_REVOKE; 223 else 224 return MRK_ERROR; 225 226 /* Skip past marker and any whitespace that follows it */ 227 cp = sp; 228 for (; *cp == ' ' || *cp == '\t'; cp++) 229 ; 230 } 231 *cpp = cp; 232 return ret; 233 } 234 235 struct hostkeys * 236 init_hostkeys(void) 237 { 238 struct hostkeys *ret = xcalloc(1, sizeof(*ret)); 239 240 ret->entries = NULL; 241 return ret; 242 } 243 244 void 245 load_hostkeys(struct hostkeys *hostkeys, const char *host, const char *path) 246 { 247 FILE *f; 248 char line[8192]; 249 u_long linenum = 0, num_loaded = 0; 250 char *cp, *cp2, *hashed_host; 251 HostkeyMarker marker; 252 Key *key; 253 int kbits; 254 255 if ((f = fopen(path, "r")) == NULL) 256 return; 257 debug3("%s: loading entries for host \"%.100s\" from file \"%s\"", 258 __func__, host, path); 259 while (read_keyfile_line(f, path, line, sizeof(line), &linenum) == 0) { 260 cp = line; 261 262 /* Skip any leading whitespace, comments and empty lines. */ 263 for (; *cp == ' ' || *cp == '\t'; cp++) 264 ; 265 if (!*cp || *cp == '#' || *cp == '\n') 266 continue; 267 268 if ((marker = check_markers(&cp)) == MRK_ERROR) { 269 verbose("%s: invalid marker at %s:%lu", 270 __func__, path, linenum); 271 continue; 272 } 273 274 /* Find the end of the host name portion. */ 275 for (cp2 = cp; *cp2 && *cp2 != ' ' && *cp2 != '\t'; cp2++) 276 ; 277 278 /* Check if the host name matches. */ 279 if (match_hostname(host, cp, (u_int) (cp2 - cp)) != 1) { 280 if (*cp != HASH_DELIM) 281 continue; 282 hashed_host = host_hash(host, cp, (u_int) (cp2 - cp)); 283 if (hashed_host == NULL) { 284 debug("Invalid hashed host line %lu of %s", 285 linenum, path); 286 continue; 287 } 288 if (strncmp(hashed_host, cp, (u_int) (cp2 - cp)) != 0) 289 continue; 290 } 291 292 /* Got a match. Skip host name. */ 293 cp = cp2; 294 295 /* 296 * Extract the key from the line. This will skip any leading 297 * whitespace. Ignore badly formatted lines. 298 */ 299 key = key_new(KEY_UNSPEC); 300 if (!hostfile_read_key(&cp, &kbits, key)) { 301 key_free(key); 302 #ifdef WITH_SSH1 303 key = key_new(KEY_RSA1); 304 if (!hostfile_read_key(&cp, &kbits, key)) { 305 key_free(key); 306 continue; 307 } 308 #else 309 continue; 310 #endif 311 } 312 if (!hostfile_check_key(kbits, key, host, path, linenum)) 313 continue; 314 315 debug3("%s: found %skey type %s in file %s:%lu", __func__, 316 marker == MRK_NONE ? "" : 317 (marker == MRK_CA ? "ca " : "revoked "), 318 key_type(key), path, linenum); 319 hostkeys->entries = xrealloc(hostkeys->entries, 320 hostkeys->num_entries + 1, sizeof(*hostkeys->entries)); 321 hostkeys->entries[hostkeys->num_entries].host = xstrdup(host); 322 hostkeys->entries[hostkeys->num_entries].file = xstrdup(path); 323 hostkeys->entries[hostkeys->num_entries].line = linenum; 324 hostkeys->entries[hostkeys->num_entries].key = key; 325 hostkeys->entries[hostkeys->num_entries].marker = marker; 326 hostkeys->num_entries++; 327 num_loaded++; 328 } 329 debug3("%s: loaded %lu keys", __func__, num_loaded); 330 fclose(f); 331 return; 332 } 333 334 void 335 free_hostkeys(struct hostkeys *hostkeys) 336 { 337 u_int i; 338 339 for (i = 0; i < hostkeys->num_entries; i++) { 340 free(hostkeys->entries[i].host); 341 free(hostkeys->entries[i].file); 342 key_free(hostkeys->entries[i].key); 343 explicit_bzero(hostkeys->entries + i, sizeof(*hostkeys->entries)); 344 } 345 free(hostkeys->entries); 346 explicit_bzero(hostkeys, sizeof(*hostkeys)); 347 free(hostkeys); 348 } 349 350 static int 351 check_key_not_revoked(struct hostkeys *hostkeys, Key *k) 352 { 353 int is_cert = key_is_cert(k); 354 u_int i; 355 356 for (i = 0; i < hostkeys->num_entries; i++) { 357 if (hostkeys->entries[i].marker != MRK_REVOKE) 358 continue; 359 if (key_equal_public(k, hostkeys->entries[i].key)) 360 return -1; 361 if (is_cert && 362 key_equal_public(k->cert->signature_key, 363 hostkeys->entries[i].key)) 364 return -1; 365 } 366 return 0; 367 } 368 369 /* 370 * Match keys against a specified key, or look one up by key type. 371 * 372 * If looking for a keytype (key == NULL) and one is found then return 373 * HOST_FOUND, otherwise HOST_NEW. 374 * 375 * If looking for a key (key != NULL): 376 * 1. If the key is a cert and a matching CA is found, return HOST_OK 377 * 2. If the key is not a cert and a matching key is found, return HOST_OK 378 * 3. If no key matches but a key with a different type is found, then 379 * return HOST_CHANGED 380 * 4. If no matching keys are found, then return HOST_NEW. 381 * 382 * Finally, check any found key is not revoked. 383 */ 384 static HostStatus 385 check_hostkeys_by_key_or_type(struct hostkeys *hostkeys, 386 Key *k, int keytype, const struct hostkey_entry **found) 387 { 388 u_int i; 389 HostStatus end_return = HOST_NEW; 390 int want_cert = key_is_cert(k); 391 HostkeyMarker want_marker = want_cert ? MRK_CA : MRK_NONE; 392 int proto = (k ? k->type : keytype) == KEY_RSA1 ? 1 : 2; 393 394 if (found != NULL) 395 *found = NULL; 396 397 for (i = 0; i < hostkeys->num_entries; i++) { 398 if (proto == 1 && hostkeys->entries[i].key->type != KEY_RSA1) 399 continue; 400 if (proto == 2 && hostkeys->entries[i].key->type == KEY_RSA1) 401 continue; 402 if (hostkeys->entries[i].marker != want_marker) 403 continue; 404 if (k == NULL) { 405 if (hostkeys->entries[i].key->type != keytype) 406 continue; 407 end_return = HOST_FOUND; 408 if (found != NULL) 409 *found = hostkeys->entries + i; 410 k = hostkeys->entries[i].key; 411 break; 412 } 413 if (want_cert) { 414 if (key_equal_public(k->cert->signature_key, 415 hostkeys->entries[i].key)) { 416 /* A matching CA exists */ 417 end_return = HOST_OK; 418 if (found != NULL) 419 *found = hostkeys->entries + i; 420 break; 421 } 422 } else { 423 if (key_equal(k, hostkeys->entries[i].key)) { 424 end_return = HOST_OK; 425 if (found != NULL) 426 *found = hostkeys->entries + i; 427 break; 428 } 429 /* A non-maching key exists */ 430 end_return = HOST_CHANGED; 431 if (found != NULL) 432 *found = hostkeys->entries + i; 433 } 434 } 435 if (check_key_not_revoked(hostkeys, k) != 0) { 436 end_return = HOST_REVOKED; 437 if (found != NULL) 438 *found = NULL; 439 } 440 return end_return; 441 } 442 443 HostStatus 444 check_key_in_hostkeys(struct hostkeys *hostkeys, Key *key, 445 const struct hostkey_entry **found) 446 { 447 if (key == NULL) 448 fatal("no key to look up"); 449 return check_hostkeys_by_key_or_type(hostkeys, key, 0, found); 450 } 451 452 int 453 lookup_key_in_hostkeys_by_type(struct hostkeys *hostkeys, int keytype, 454 const struct hostkey_entry **found) 455 { 456 return (check_hostkeys_by_key_or_type(hostkeys, NULL, keytype, 457 found) == HOST_FOUND); 458 } 459 460 /* 461 * Appends an entry to the host file. Returns false if the entry could not 462 * be appended. 463 */ 464 465 int 466 add_host_to_hostfile(const char *filename, const char *host, const Key *key, 467 int store_hash) 468 { 469 FILE *f; 470 int success = 0; 471 char *hashed_host = NULL; 472 473 if (key == NULL) 474 return 1; /* XXX ? */ 475 f = fopen(filename, "a"); 476 if (!f) 477 return 0; 478 479 if (store_hash) { 480 if ((hashed_host = host_hash(host, NULL, 0)) == NULL) { 481 error("add_host_to_hostfile: host_hash failed"); 482 fclose(f); 483 return 0; 484 } 485 } 486 fprintf(f, "%s ", store_hash ? hashed_host : host); 487 488 if (key_write(key, f)) { 489 success = 1; 490 } else { 491 error("add_host_to_hostfile: saving key in %s failed", filename); 492 } 493 fprintf(f, "\n"); 494 fclose(f); 495 return success; 496 } 497