1 /* $OpenBSD: hostfile.c,v 1.53 2014/01/09 23:20:00 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 <openssl/hmac.h> 46 #include <openssl/sha.h> 47 48 #include <resolv.h> 49 #include <stdarg.h> 50 #include <stdio.h> 51 #include <stdlib.h> 52 #include <string.h> 53 54 #include "xmalloc.h" 55 #include "match.h" 56 #include "key.h" 57 #include "hostfile.h" 58 #include "log.h" 59 #include "misc.h" 60 #include "digest.h" 61 62 struct hostkeys { 63 struct hostkey_entry *entries; 64 u_int num_entries; 65 }; 66 67 static int 68 extract_salt(const char *s, u_int l, u_char *salt, size_t salt_len) 69 { 70 char *p, *b64salt; 71 u_int b64len; 72 int ret; 73 74 if (l < sizeof(HASH_MAGIC) - 1) { 75 debug2("extract_salt: string too short"); 76 return (-1); 77 } 78 if (strncmp(s, HASH_MAGIC, sizeof(HASH_MAGIC) - 1) != 0) { 79 debug2("extract_salt: invalid magic identifier"); 80 return (-1); 81 } 82 s += sizeof(HASH_MAGIC) - 1; 83 l -= sizeof(HASH_MAGIC) - 1; 84 if ((p = memchr(s, HASH_DELIM, l)) == NULL) { 85 debug2("extract_salt: missing salt termination character"); 86 return (-1); 87 } 88 89 b64len = p - s; 90 /* Sanity check */ 91 if (b64len == 0 || b64len > 1024) { 92 debug2("extract_salt: bad encoded salt length %u", b64len); 93 return (-1); 94 } 95 b64salt = xmalloc(1 + b64len); 96 memcpy(b64salt, s, b64len); 97 b64salt[b64len] = '\0'; 98 99 ret = __b64_pton(b64salt, salt, salt_len); 100 free(b64salt); 101 if (ret == -1) { 102 debug2("extract_salt: salt decode error"); 103 return (-1); 104 } 105 if (ret != SHA_DIGEST_LENGTH) { 106 debug2("extract_salt: expected salt len %d, got %d", 107 SHA_DIGEST_LENGTH, ret); 108 return (-1); 109 } 110 111 return (0); 112 } 113 114 char * 115 host_hash(const char *host, const char *name_from_hostfile, u_int src_len) 116 { 117 const EVP_MD *md = EVP_sha1(); 118 HMAC_CTX mac_ctx; 119 u_char salt[256], result[256]; 120 char uu_salt[512], uu_result[512]; 121 static char encoded[1024]; 122 u_int i, len; 123 124 len = EVP_MD_size(md); 125 126 if (name_from_hostfile == NULL) { 127 /* Create new salt */ 128 for (i = 0; i < len; i++) 129 salt[i] = arc4random(); 130 } else { 131 /* Extract salt from known host entry */ 132 if (extract_salt(name_from_hostfile, src_len, salt, 133 sizeof(salt)) == -1) 134 return (NULL); 135 } 136 137 HMAC_Init(&mac_ctx, salt, len, md); 138 HMAC_Update(&mac_ctx, (u_char *)host, strlen(host)); 139 HMAC_Final(&mac_ctx, result, NULL); 140 HMAC_cleanup(&mac_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("host_hash: __b64_ntop failed"); 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 if (key == NULL || key->type != KEY_RSA1 || key->rsa == NULL) 187 return 1; 188 if (bits != BN_num_bits(key->rsa->n)) { 189 logit("Warning: %s, line %lu: keysize mismatch for host %s: " 190 "actual %d vs. announced %d.", 191 filename, linenum, host, BN_num_bits(key->rsa->n), bits); 192 logit("Warning: replace %d with %d in %s, line %lu.", 193 bits, BN_num_bits(key->rsa->n), filename, linenum); 194 } 195 return 1; 196 } 197 198 static HostkeyMarker 199 check_markers(char **cpp) 200 { 201 char marker[32], *sp, *cp = *cpp; 202 int ret = MRK_NONE; 203 204 while (*cp == '@') { 205 /* Only one marker is allowed */ 206 if (ret != MRK_NONE) 207 return MRK_ERROR; 208 /* Markers are terminated by whitespace */ 209 if ((sp = strchr(cp, ' ')) == NULL && 210 (sp = strchr(cp, '\t')) == NULL) 211 return MRK_ERROR; 212 /* Extract marker for comparison */ 213 if (sp <= cp + 1 || sp >= cp + sizeof(marker)) 214 return MRK_ERROR; 215 memcpy(marker, cp, sp - cp); 216 marker[sp - cp] = '\0'; 217 if (strcmp(marker, CA_MARKER) == 0) 218 ret = MRK_CA; 219 else if (strcmp(marker, REVOKE_MARKER) == 0) 220 ret = MRK_REVOKE; 221 else 222 return MRK_ERROR; 223 224 /* Skip past marker and any whitespace that follows it */ 225 cp = sp; 226 for (; *cp == ' ' || *cp == '\t'; cp++) 227 ; 228 } 229 *cpp = cp; 230 return ret; 231 } 232 233 struct hostkeys * 234 init_hostkeys(void) 235 { 236 struct hostkeys *ret = xcalloc(1, sizeof(*ret)); 237 238 ret->entries = NULL; 239 return ret; 240 } 241 242 void 243 load_hostkeys(struct hostkeys *hostkeys, const char *host, const char *path) 244 { 245 FILE *f; 246 char line[8192]; 247 u_long linenum = 0, num_loaded = 0; 248 char *cp, *cp2, *hashed_host; 249 HostkeyMarker marker; 250 Key *key; 251 int kbits; 252 253 if ((f = fopen(path, "r")) == NULL) 254 return; 255 debug3("%s: loading entries for host \"%.100s\" from file \"%s\"", 256 __func__, host, path); 257 while (read_keyfile_line(f, path, line, sizeof(line), &linenum) == 0) { 258 cp = line; 259 260 /* Skip any leading whitespace, comments and empty lines. */ 261 for (; *cp == ' ' || *cp == '\t'; cp++) 262 ; 263 if (!*cp || *cp == '#' || *cp == '\n') 264 continue; 265 266 if ((marker = check_markers(&cp)) == MRK_ERROR) { 267 verbose("%s: invalid marker at %s:%lu", 268 __func__, path, linenum); 269 continue; 270 } 271 272 /* Find the end of the host name portion. */ 273 for (cp2 = cp; *cp2 && *cp2 != ' ' && *cp2 != '\t'; cp2++) 274 ; 275 276 /* Check if the host name matches. */ 277 if (match_hostname(host, cp, (u_int) (cp2 - cp)) != 1) { 278 if (*cp != HASH_DELIM) 279 continue; 280 hashed_host = host_hash(host, cp, (u_int) (cp2 - cp)); 281 if (hashed_host == NULL) { 282 debug("Invalid hashed host line %lu of %s", 283 linenum, path); 284 continue; 285 } 286 if (strncmp(hashed_host, cp, (u_int) (cp2 - cp)) != 0) 287 continue; 288 } 289 290 /* Got a match. Skip host name. */ 291 cp = cp2; 292 293 /* 294 * Extract the key from the line. This will skip any leading 295 * whitespace. Ignore badly formatted lines. 296 */ 297 key = key_new(KEY_UNSPEC); 298 if (!hostfile_read_key(&cp, &kbits, key)) { 299 key_free(key); 300 key = key_new(KEY_RSA1); 301 if (!hostfile_read_key(&cp, &kbits, key)) { 302 key_free(key); 303 continue; 304 } 305 } 306 if (!hostfile_check_key(kbits, key, host, path, linenum)) 307 continue; 308 309 debug3("%s: found %skey type %s in file %s:%lu", __func__, 310 marker == MRK_NONE ? "" : 311 (marker == MRK_CA ? "ca " : "revoked "), 312 key_type(key), path, linenum); 313 hostkeys->entries = xrealloc(hostkeys->entries, 314 hostkeys->num_entries + 1, sizeof(*hostkeys->entries)); 315 hostkeys->entries[hostkeys->num_entries].host = xstrdup(host); 316 hostkeys->entries[hostkeys->num_entries].file = xstrdup(path); 317 hostkeys->entries[hostkeys->num_entries].line = linenum; 318 hostkeys->entries[hostkeys->num_entries].key = key; 319 hostkeys->entries[hostkeys->num_entries].marker = marker; 320 hostkeys->num_entries++; 321 num_loaded++; 322 } 323 debug3("%s: loaded %lu keys", __func__, num_loaded); 324 fclose(f); 325 return; 326 } 327 328 void 329 free_hostkeys(struct hostkeys *hostkeys) 330 { 331 u_int i; 332 333 for (i = 0; i < hostkeys->num_entries; i++) { 334 free(hostkeys->entries[i].host); 335 free(hostkeys->entries[i].file); 336 key_free(hostkeys->entries[i].key); 337 bzero(hostkeys->entries + i, sizeof(*hostkeys->entries)); 338 } 339 free(hostkeys->entries); 340 bzero(hostkeys, sizeof(*hostkeys)); 341 free(hostkeys); 342 } 343 344 static int 345 check_key_not_revoked(struct hostkeys *hostkeys, Key *k) 346 { 347 int is_cert = key_is_cert(k); 348 u_int i; 349 350 for (i = 0; i < hostkeys->num_entries; i++) { 351 if (hostkeys->entries[i].marker != MRK_REVOKE) 352 continue; 353 if (key_equal_public(k, hostkeys->entries[i].key)) 354 return -1; 355 if (is_cert && 356 key_equal_public(k->cert->signature_key, 357 hostkeys->entries[i].key)) 358 return -1; 359 } 360 return 0; 361 } 362 363 /* 364 * Match keys against a specified key, or look one up by key type. 365 * 366 * If looking for a keytype (key == NULL) and one is found then return 367 * HOST_FOUND, otherwise HOST_NEW. 368 * 369 * If looking for a key (key != NULL): 370 * 1. If the key is a cert and a matching CA is found, return HOST_OK 371 * 2. If the key is not a cert and a matching key is found, return HOST_OK 372 * 3. If no key matches but a key with a different type is found, then 373 * return HOST_CHANGED 374 * 4. If no matching keys are found, then return HOST_NEW. 375 * 376 * Finally, check any found key is not revoked. 377 */ 378 static HostStatus 379 check_hostkeys_by_key_or_type(struct hostkeys *hostkeys, 380 Key *k, int keytype, const struct hostkey_entry **found) 381 { 382 u_int i; 383 HostStatus end_return = HOST_NEW; 384 int want_cert = key_is_cert(k); 385 HostkeyMarker want_marker = want_cert ? MRK_CA : MRK_NONE; 386 int proto = (k ? k->type : keytype) == KEY_RSA1 ? 1 : 2; 387 388 if (found != NULL) 389 *found = NULL; 390 391 for (i = 0; i < hostkeys->num_entries; i++) { 392 if (proto == 1 && hostkeys->entries[i].key->type != KEY_RSA1) 393 continue; 394 if (proto == 2 && hostkeys->entries[i].key->type == KEY_RSA1) 395 continue; 396 if (hostkeys->entries[i].marker != want_marker) 397 continue; 398 if (k == NULL) { 399 if (hostkeys->entries[i].key->type != keytype) 400 continue; 401 end_return = HOST_FOUND; 402 if (found != NULL) 403 *found = hostkeys->entries + i; 404 k = hostkeys->entries[i].key; 405 break; 406 } 407 if (want_cert) { 408 if (key_equal_public(k->cert->signature_key, 409 hostkeys->entries[i].key)) { 410 /* A matching CA exists */ 411 end_return = HOST_OK; 412 if (found != NULL) 413 *found = hostkeys->entries + i; 414 break; 415 } 416 } else { 417 if (key_equal(k, hostkeys->entries[i].key)) { 418 end_return = HOST_OK; 419 if (found != NULL) 420 *found = hostkeys->entries + i; 421 break; 422 } 423 /* A non-maching key exists */ 424 end_return = HOST_CHANGED; 425 if (found != NULL) 426 *found = hostkeys->entries + i; 427 } 428 } 429 if (check_key_not_revoked(hostkeys, k) != 0) { 430 end_return = HOST_REVOKED; 431 if (found != NULL) 432 *found = NULL; 433 } 434 return end_return; 435 } 436 437 HostStatus 438 check_key_in_hostkeys(struct hostkeys *hostkeys, Key *key, 439 const struct hostkey_entry **found) 440 { 441 if (key == NULL) 442 fatal("no key to look up"); 443 return check_hostkeys_by_key_or_type(hostkeys, key, 0, found); 444 } 445 446 int 447 lookup_key_in_hostkeys_by_type(struct hostkeys *hostkeys, int keytype, 448 const struct hostkey_entry **found) 449 { 450 return (check_hostkeys_by_key_or_type(hostkeys, NULL, keytype, 451 found) == HOST_FOUND); 452 } 453 454 /* 455 * Appends an entry to the host file. Returns false if the entry could not 456 * be appended. 457 */ 458 459 int 460 add_host_to_hostfile(const char *filename, const char *host, const Key *key, 461 int store_hash) 462 { 463 FILE *f; 464 int success = 0; 465 char *hashed_host = NULL; 466 467 if (key == NULL) 468 return 1; /* XXX ? */ 469 f = fopen(filename, "a"); 470 if (!f) 471 return 0; 472 473 if (store_hash) { 474 if ((hashed_host = host_hash(host, NULL, 0)) == NULL) { 475 error("add_host_to_hostfile: host_hash failed"); 476 fclose(f); 477 return 0; 478 } 479 } 480 fprintf(f, "%s ", store_hash ? hashed_host : host); 481 482 if (key_write(key, f)) { 483 success = 1; 484 } else { 485 error("add_host_to_hostfile: saving key in %s failed", filename); 486 } 487 fprintf(f, "\n"); 488 fclose(f); 489 return success; 490 } 491