1 /* $OpenBSD: hostfile.c,v 1.50 2010/12/04 13:31:37 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 <sys/types.h> 40 41 #include <netinet/in.h> 42 43 #include <openssl/hmac.h> 44 #include <openssl/sha.h> 45 46 #include <resolv.h> 47 #include <stdio.h> 48 #include <stdlib.h> 49 #include <string.h> 50 51 #include "xmalloc.h" 52 #include "match.h" 53 #include "key.h" 54 #include "hostfile.h" 55 #include "log.h" 56 #include "misc.h" 57 58 struct hostkeys { 59 struct hostkey_entry *entries; 60 u_int num_entries; 61 }; 62 63 static int 64 extract_salt(const char *s, u_int l, char *salt, size_t salt_len) 65 { 66 char *p, *b64salt; 67 u_int b64len; 68 int ret; 69 70 if (l < sizeof(HASH_MAGIC) - 1) { 71 debug2("extract_salt: string too short"); 72 return (-1); 73 } 74 if (strncmp(s, HASH_MAGIC, sizeof(HASH_MAGIC) - 1) != 0) { 75 debug2("extract_salt: invalid magic identifier"); 76 return (-1); 77 } 78 s += sizeof(HASH_MAGIC) - 1; 79 l -= sizeof(HASH_MAGIC) - 1; 80 if ((p = memchr(s, HASH_DELIM, l)) == NULL) { 81 debug2("extract_salt: missing salt termination character"); 82 return (-1); 83 } 84 85 b64len = p - s; 86 /* Sanity check */ 87 if (b64len == 0 || b64len > 1024) { 88 debug2("extract_salt: bad encoded salt length %u", b64len); 89 return (-1); 90 } 91 b64salt = xmalloc(1 + b64len); 92 memcpy(b64salt, s, b64len); 93 b64salt[b64len] = '\0'; 94 95 ret = __b64_pton(b64salt, salt, salt_len); 96 xfree(b64salt); 97 if (ret == -1) { 98 debug2("extract_salt: salt decode error"); 99 return (-1); 100 } 101 if (ret != SHA_DIGEST_LENGTH) { 102 debug2("extract_salt: expected salt len %d, got %d", 103 SHA_DIGEST_LENGTH, ret); 104 return (-1); 105 } 106 107 return (0); 108 } 109 110 char * 111 host_hash(const char *host, const char *name_from_hostfile, u_int src_len) 112 { 113 const EVP_MD *md = EVP_sha1(); 114 HMAC_CTX mac_ctx; 115 char salt[256], result[256], uu_salt[512], uu_result[512]; 116 static char encoded[1024]; 117 u_int i, len; 118 119 len = EVP_MD_size(md); 120 121 if (name_from_hostfile == NULL) { 122 /* Create new salt */ 123 for (i = 0; i < len; i++) 124 salt[i] = arc4random(); 125 } else { 126 /* Extract salt from known host entry */ 127 if (extract_salt(name_from_hostfile, src_len, salt, 128 sizeof(salt)) == -1) 129 return (NULL); 130 } 131 132 HMAC_Init(&mac_ctx, salt, len, md); 133 HMAC_Update(&mac_ctx, host, strlen(host)); 134 HMAC_Final(&mac_ctx, result, NULL); 135 HMAC_cleanup(&mac_ctx); 136 137 if (__b64_ntop(salt, len, uu_salt, sizeof(uu_salt)) == -1 || 138 __b64_ntop(result, len, uu_result, sizeof(uu_result)) == -1) 139 fatal("host_hash: __b64_ntop failed"); 140 141 snprintf(encoded, sizeof(encoded), "%s%s%c%s", HASH_MAGIC, uu_salt, 142 HASH_DELIM, uu_result); 143 144 return (encoded); 145 } 146 147 /* 148 * Parses an RSA (number of bits, e, n) or DSA key from a string. Moves the 149 * pointer over the key. Skips any whitespace at the beginning and at end. 150 */ 151 152 int 153 hostfile_read_key(char **cpp, u_int *bitsp, Key *ret) 154 { 155 char *cp; 156 157 /* Skip leading whitespace. */ 158 for (cp = *cpp; *cp == ' ' || *cp == '\t'; cp++) 159 ; 160 161 if (key_read(ret, &cp) != 1) 162 return 0; 163 164 /* Skip trailing whitespace. */ 165 for (; *cp == ' ' || *cp == '\t'; cp++) 166 ; 167 168 /* Return results. */ 169 *cpp = cp; 170 if (bitsp != NULL) 171 *bitsp = key_size(ret); 172 return 1; 173 } 174 175 static int 176 hostfile_check_key(int bits, const Key *key, const char *host, 177 const char *filename, u_long linenum) 178 { 179 if (key == NULL || key->type != KEY_RSA1 || key->rsa == NULL) 180 return 1; 181 if (bits != BN_num_bits(key->rsa->n)) { 182 logit("Warning: %s, line %lu: keysize mismatch for host %s: " 183 "actual %d vs. announced %d.", 184 filename, linenum, host, BN_num_bits(key->rsa->n), bits); 185 logit("Warning: replace %d with %d in %s, line %lu.", 186 bits, BN_num_bits(key->rsa->n), filename, linenum); 187 } 188 return 1; 189 } 190 191 static HostkeyMarker 192 check_markers(char **cpp) 193 { 194 char marker[32], *sp, *cp = *cpp; 195 int ret = MRK_NONE; 196 197 while (*cp == '@') { 198 /* Only one marker is allowed */ 199 if (ret != MRK_NONE) 200 return MRK_ERROR; 201 /* Markers are terminated by whitespace */ 202 if ((sp = strchr(cp, ' ')) == NULL && 203 (sp = strchr(cp, '\t')) == NULL) 204 return MRK_ERROR; 205 /* Extract marker for comparison */ 206 if (sp <= cp + 1 || sp >= cp + sizeof(marker)) 207 return MRK_ERROR; 208 memcpy(marker, cp, sp - cp); 209 marker[sp - cp] = '\0'; 210 if (strcmp(marker, CA_MARKER) == 0) 211 ret = MRK_CA; 212 else if (strcmp(marker, REVOKE_MARKER) == 0) 213 ret = MRK_REVOKE; 214 else 215 return MRK_ERROR; 216 217 /* Skip past marker and any whitespace that follows it */ 218 cp = sp; 219 for (; *cp == ' ' || *cp == '\t'; cp++) 220 ; 221 } 222 *cpp = cp; 223 return ret; 224 } 225 226 struct hostkeys * 227 init_hostkeys(void) 228 { 229 struct hostkeys *ret = xcalloc(1, sizeof(*ret)); 230 231 ret->entries = NULL; 232 return ret; 233 } 234 235 void 236 load_hostkeys(struct hostkeys *hostkeys, const char *host, const char *path) 237 { 238 FILE *f; 239 char line[8192]; 240 u_long linenum = 0, num_loaded = 0; 241 char *cp, *cp2, *hashed_host; 242 HostkeyMarker marker; 243 Key *key; 244 int kbits; 245 246 if ((f = fopen(path, "r")) == NULL) 247 return; 248 debug3("%s: loading entries for host \"%.100s\" from file \"%s\"", 249 __func__, host, path); 250 while (read_keyfile_line(f, path, line, sizeof(line), &linenum) == 0) { 251 cp = line; 252 253 /* Skip any leading whitespace, comments and empty lines. */ 254 for (; *cp == ' ' || *cp == '\t'; cp++) 255 ; 256 if (!*cp || *cp == '#' || *cp == '\n') 257 continue; 258 259 if ((marker = check_markers(&cp)) == MRK_ERROR) { 260 verbose("%s: invalid marker at %s:%lu", 261 __func__, path, linenum); 262 continue; 263 } 264 265 /* Find the end of the host name portion. */ 266 for (cp2 = cp; *cp2 && *cp2 != ' ' && *cp2 != '\t'; cp2++) 267 ; 268 269 /* Check if the host name matches. */ 270 if (match_hostname(host, cp, (u_int) (cp2 - cp)) != 1) { 271 if (*cp != HASH_DELIM) 272 continue; 273 hashed_host = host_hash(host, cp, (u_int) (cp2 - cp)); 274 if (hashed_host == NULL) { 275 debug("Invalid hashed host line %lu of %s", 276 linenum, path); 277 continue; 278 } 279 if (strncmp(hashed_host, cp, (u_int) (cp2 - cp)) != 0) 280 continue; 281 } 282 283 /* Got a match. Skip host name. */ 284 cp = cp2; 285 286 /* 287 * Extract the key from the line. This will skip any leading 288 * whitespace. Ignore badly formatted lines. 289 */ 290 key = key_new(KEY_UNSPEC); 291 if (!hostfile_read_key(&cp, &kbits, key)) { 292 key_free(key); 293 key = key_new(KEY_RSA1); 294 if (!hostfile_read_key(&cp, &kbits, key)) { 295 key_free(key); 296 continue; 297 } 298 } 299 if (!hostfile_check_key(kbits, key, host, path, linenum)) 300 continue; 301 302 debug3("%s: found %skey type %s in file %s:%lu", __func__, 303 marker == MRK_NONE ? "" : 304 (marker == MRK_CA ? "ca " : "revoked "), 305 key_type(key), path, linenum); 306 hostkeys->entries = xrealloc(hostkeys->entries, 307 hostkeys->num_entries + 1, sizeof(*hostkeys->entries)); 308 hostkeys->entries[hostkeys->num_entries].host = xstrdup(host); 309 hostkeys->entries[hostkeys->num_entries].file = xstrdup(path); 310 hostkeys->entries[hostkeys->num_entries].line = linenum; 311 hostkeys->entries[hostkeys->num_entries].key = key; 312 hostkeys->entries[hostkeys->num_entries].marker = marker; 313 hostkeys->num_entries++; 314 num_loaded++; 315 } 316 debug3("%s: loaded %lu keys", __func__, num_loaded); 317 fclose(f); 318 return; 319 } 320 321 void 322 free_hostkeys(struct hostkeys *hostkeys) 323 { 324 u_int i; 325 326 for (i = 0; i < hostkeys->num_entries; i++) { 327 xfree(hostkeys->entries[i].host); 328 xfree(hostkeys->entries[i].file); 329 key_free(hostkeys->entries[i].key); 330 bzero(hostkeys->entries + i, sizeof(*hostkeys->entries)); 331 } 332 if (hostkeys->entries != NULL) 333 xfree(hostkeys->entries); 334 hostkeys->entries = NULL; 335 hostkeys->num_entries = 0; 336 xfree(hostkeys); 337 } 338 339 static int 340 check_key_not_revoked(struct hostkeys *hostkeys, Key *k) 341 { 342 int is_cert = key_is_cert(k); 343 u_int i; 344 345 for (i = 0; i < hostkeys->num_entries; i++) { 346 if (hostkeys->entries[i].marker != MRK_REVOKE) 347 continue; 348 if (key_equal_public(k, hostkeys->entries[i].key)) 349 return -1; 350 if (is_cert && 351 key_equal_public(k->cert->signature_key, 352 hostkeys->entries[i].key)) 353 return -1; 354 } 355 return 0; 356 } 357 358 /* 359 * Match keys against a specified key, or look one up by key type. 360 * 361 * If looking for a keytype (key == NULL) and one is found then return 362 * HOST_FOUND, otherwise HOST_NEW. 363 * 364 * If looking for a key (key != NULL): 365 * 1. If the key is a cert and a matching CA is found, return HOST_OK 366 * 2. If the key is not a cert and a matching key is found, return HOST_OK 367 * 3. If no key matches but a key with a different type is found, then 368 * return HOST_CHANGED 369 * 4. If no matching keys are found, then return HOST_NEW. 370 * 371 * Finally, check any found key is not revoked. 372 */ 373 static HostStatus 374 check_hostkeys_by_key_or_type(struct hostkeys *hostkeys, 375 Key *k, int keytype, const struct hostkey_entry **found) 376 { 377 u_int i; 378 HostStatus end_return = HOST_NEW; 379 int want_cert = key_is_cert(k); 380 HostkeyMarker want_marker = want_cert ? MRK_CA : MRK_NONE; 381 int proto = (k ? k->type : keytype) == KEY_RSA1 ? 1 : 2; 382 383 if (found != NULL) 384 *found = NULL; 385 386 for (i = 0; i < hostkeys->num_entries; i++) { 387 if (proto == 1 && hostkeys->entries[i].key->type != KEY_RSA1) 388 continue; 389 if (proto == 2 && hostkeys->entries[i].key->type == KEY_RSA1) 390 continue; 391 if (hostkeys->entries[i].marker != want_marker) 392 continue; 393 if (k == NULL) { 394 if (hostkeys->entries[i].key->type != keytype) 395 continue; 396 end_return = HOST_FOUND; 397 if (found != NULL) 398 *found = hostkeys->entries + i; 399 k = hostkeys->entries[i].key; 400 break; 401 } 402 if (want_cert) { 403 if (key_equal_public(k->cert->signature_key, 404 hostkeys->entries[i].key)) { 405 /* A matching CA exists */ 406 end_return = HOST_OK; 407 if (found != NULL) 408 *found = hostkeys->entries + i; 409 break; 410 } 411 } else { 412 if (key_equal(k, hostkeys->entries[i].key)) { 413 end_return = HOST_OK; 414 if (found != NULL) 415 *found = hostkeys->entries + i; 416 break; 417 } 418 /* A non-maching key exists */ 419 end_return = HOST_CHANGED; 420 if (found != NULL) 421 *found = hostkeys->entries + i; 422 } 423 } 424 if (check_key_not_revoked(hostkeys, k) != 0) { 425 end_return = HOST_REVOKED; 426 if (found != NULL) 427 *found = NULL; 428 } 429 return end_return; 430 } 431 432 HostStatus 433 check_key_in_hostkeys(struct hostkeys *hostkeys, Key *key, 434 const struct hostkey_entry **found) 435 { 436 if (key == NULL) 437 fatal("no key to look up"); 438 return check_hostkeys_by_key_or_type(hostkeys, key, 0, found); 439 } 440 441 int 442 lookup_key_in_hostkeys_by_type(struct hostkeys *hostkeys, int keytype, 443 const struct hostkey_entry **found) 444 { 445 return (check_hostkeys_by_key_or_type(hostkeys, NULL, keytype, 446 found) == HOST_FOUND); 447 } 448 449 /* 450 * Appends an entry to the host file. Returns false if the entry could not 451 * be appended. 452 */ 453 454 int 455 add_host_to_hostfile(const char *filename, const char *host, const Key *key, 456 int store_hash) 457 { 458 FILE *f; 459 int success = 0; 460 char *hashed_host = NULL; 461 462 if (key == NULL) 463 return 1; /* XXX ? */ 464 f = fopen(filename, "a"); 465 if (!f) 466 return 0; 467 468 if (store_hash) { 469 if ((hashed_host = host_hash(host, NULL, 0)) == NULL) { 470 error("add_host_to_hostfile: host_hash failed"); 471 fclose(f); 472 return 0; 473 } 474 } 475 fprintf(f, "%s ", store_hash ? hashed_host : host); 476 477 if (key_write(key, f)) { 478 success = 1; 479 } else { 480 error("add_host_to_hostfile: saving key in %s failed", filename); 481 } 482 fprintf(f, "\n"); 483 fclose(f); 484 return success; 485 } 486