1 /* $OpenBSD: hostfile.c,v 1.50 2010/12/04 13:31:37 djm Exp $ */ 2 /* 3 * Author: Tatu Ylonen <ylo (at) cs.hut.fi> 4 * Copyright (c) 1995 Tatu Ylonen <ylo (at) 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 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, 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 xfree(b64salt); 100 if (ret == -1) { 101 debug2("extract_salt: salt decode error"); 102 return (-1); 103 } 104 if (ret != SHA_DIGEST_LENGTH) { 105 debug2("extract_salt: expected salt len %d, got %d", 106 SHA_DIGEST_LENGTH, 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 const EVP_MD *md = EVP_sha1(); 117 HMAC_CTX mac_ctx; 118 char salt[256], result[256], uu_salt[512], uu_result[512]; 119 static char encoded[1024]; 120 u_int i, len; 121 122 len = EVP_MD_size(md); 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 HMAC_Init(&mac_ctx, salt, len, md); 136 HMAC_Update(&mac_ctx, host, strlen(host)); 137 HMAC_Final(&mac_ctx, result, NULL); 138 HMAC_cleanup(&mac_ctx); 139 140 if (__b64_ntop(salt, len, uu_salt, sizeof(uu_salt)) == -1 || 141 __b64_ntop(result, len, uu_result, sizeof(uu_result)) == -1) 142 fatal("host_hash: __b64_ntop failed"); 143 144 snprintf(encoded, sizeof(encoded), "%s%s%c%s", HASH_MAGIC, uu_salt, 145 HASH_DELIM, uu_result); 146 147 return (encoded); 148 } 149 150 /* 151 * Parses an RSA (number of bits, e, n) or DSA key from a string. Moves the 152 * pointer over the key. Skips any whitespace at the beginning and at end. 153 */ 154 155 int 156 hostfile_read_key(char **cpp, u_int *bitsp, Key *ret) 157 { 158 char *cp; 159 160 /* Skip leading whitespace. */ 161 for (cp = *cpp; *cp == ' ' || *cp == '\t'; cp++) 162 ; 163 164 if (key_read(ret, &cp) != 1) 165 return 0; 166 167 /* Skip trailing whitespace. */ 168 for (; *cp == ' ' || *cp == '\t'; cp++) 169 ; 170 171 /* Return results. */ 172 *cpp = cp; 173 if (bitsp != NULL) 174 *bitsp = key_size(ret); 175 return 1; 176 } 177 178 static int 179 hostfile_check_key(int bits, const Key *key, const char *host, 180 const char *filename, u_long linenum) 181 { 182 if (key == NULL || key->type != KEY_RSA1 || key->rsa == NULL) 183 return 1; 184 if (bits != BN_num_bits(key->rsa->n)) { 185 logit("Warning: %s, line %lu: keysize mismatch for host %s: " 186 "actual %d vs. announced %d.", 187 filename, linenum, host, BN_num_bits(key->rsa->n), bits); 188 logit("Warning: replace %d with %d in %s, line %lu.", 189 bits, BN_num_bits(key->rsa->n), filename, linenum); 190 } 191 return 1; 192 } 193 194 static HostkeyMarker 195 check_markers(char **cpp) 196 { 197 char marker[32], *sp, *cp = *cpp; 198 int ret = MRK_NONE; 199 200 while (*cp == '@') { 201 /* Only one marker is allowed */ 202 if (ret != MRK_NONE) 203 return MRK_ERROR; 204 /* Markers are terminated by whitespace */ 205 if ((sp = strchr(cp, ' ')) == NULL && 206 (sp = strchr(cp, '\t')) == NULL) 207 return MRK_ERROR; 208 /* Extract marker for comparison */ 209 if (sp <= cp + 1 || sp >= cp + sizeof(marker)) 210 return MRK_ERROR; 211 memcpy(marker, cp, sp - cp); 212 marker[sp - cp] = '\0'; 213 if (strcmp(marker, CA_MARKER) == 0) 214 ret = MRK_CA; 215 else if (strcmp(marker, REVOKE_MARKER) == 0) 216 ret = MRK_REVOKE; 217 else 218 return MRK_ERROR; 219 220 /* Skip past marker and any whitespace that follows it */ 221 cp = sp; 222 for (; *cp == ' ' || *cp == '\t'; cp++) 223 ; 224 } 225 *cpp = cp; 226 return ret; 227 } 228 229 struct hostkeys * 230 init_hostkeys(void) 231 { 232 struct hostkeys *ret = xcalloc(1, sizeof(*ret)); 233 234 ret->entries = NULL; 235 return ret; 236 } 237 238 void 239 load_hostkeys(struct hostkeys *hostkeys, const char *host, const char *path) 240 { 241 FILE *f; 242 char line[8192]; 243 u_long linenum = 0, num_loaded = 0; 244 char *cp, *cp2, *hashed_host; 245 HostkeyMarker marker; 246 Key *key; 247 int kbits; 248 249 if ((f = fopen(path, "r")) == NULL) 250 return; 251 debug3("%s: loading entries for host \"%.100s\" from file \"%s\"", 252 __func__, host, path); 253 while (read_keyfile_line(f, path, line, sizeof(line), &linenum) == 0) { 254 cp = line; 255 256 /* Skip any leading whitespace, comments and empty lines. */ 257 for (; *cp == ' ' || *cp == '\t'; cp++) 258 ; 259 if (!*cp || *cp == '#' || *cp == '\n') 260 continue; 261 262 if ((marker = check_markers(&cp)) == MRK_ERROR) { 263 verbose("%s: invalid marker at %s:%lu", 264 __func__, path, linenum); 265 continue; 266 } 267 268 /* Find the end of the host name portion. */ 269 for (cp2 = cp; *cp2 && *cp2 != ' ' && *cp2 != '\t'; cp2++) 270 ; 271 272 /* Check if the host name matches. */ 273 if (match_hostname(host, cp, (u_int) (cp2 - cp)) != 1) { 274 if (*cp != HASH_DELIM) 275 continue; 276 hashed_host = host_hash(host, cp, (u_int) (cp2 - cp)); 277 if (hashed_host == NULL) { 278 debug("Invalid hashed host line %lu of %s", 279 linenum, path); 280 continue; 281 } 282 if (strncmp(hashed_host, cp, (u_int) (cp2 - cp)) != 0) 283 continue; 284 } 285 286 /* Got a match. Skip host name. */ 287 cp = cp2; 288 289 /* 290 * Extract the key from the line. This will skip any leading 291 * whitespace. Ignore badly formatted lines. 292 */ 293 key = key_new(KEY_UNSPEC); 294 if (!hostfile_read_key(&cp, &kbits, key)) { 295 key_free(key); 296 key = key_new(KEY_RSA1); 297 if (!hostfile_read_key(&cp, &kbits, key)) { 298 key_free(key); 299 continue; 300 } 301 } 302 if (!hostfile_check_key(kbits, key, host, path, linenum)) 303 continue; 304 305 debug3("%s: found %skey type %s in file %s:%lu", __func__, 306 marker == MRK_NONE ? "" : 307 (marker == MRK_CA ? "ca " : "revoked "), 308 key_type(key), path, linenum); 309 hostkeys->entries = xrealloc(hostkeys->entries, 310 hostkeys->num_entries + 1, sizeof(*hostkeys->entries)); 311 hostkeys->entries[hostkeys->num_entries].host = xstrdup(host); 312 hostkeys->entries[hostkeys->num_entries].file = xstrdup(path); 313 hostkeys->entries[hostkeys->num_entries].line = linenum; 314 hostkeys->entries[hostkeys->num_entries].key = key; 315 hostkeys->entries[hostkeys->num_entries].marker = marker; 316 hostkeys->num_entries++; 317 num_loaded++; 318 } 319 debug3("%s: loaded %lu keys", __func__, num_loaded); 320 fclose(f); 321 return; 322 } 323 324 void 325 free_hostkeys(struct hostkeys *hostkeys) 326 { 327 u_int i; 328 329 for (i = 0; i < hostkeys->num_entries; i++) { 330 xfree(hostkeys->entries[i].host); 331 xfree(hostkeys->entries[i].file); 332 key_free(hostkeys->entries[i].key); 333 bzero(hostkeys->entries + i, sizeof(*hostkeys->entries)); 334 } 335 if (hostkeys->entries != NULL) 336 xfree(hostkeys->entries); 337 hostkeys->entries = NULL; 338 hostkeys->num_entries = 0; 339 xfree(hostkeys); 340 } 341 342 static int 343 check_key_not_revoked(struct hostkeys *hostkeys, Key *k) 344 { 345 int is_cert = key_is_cert(k); 346 u_int i; 347 348 for (i = 0; i < hostkeys->num_entries; i++) { 349 if (hostkeys->entries[i].marker != MRK_REVOKE) 350 continue; 351 if (key_equal_public(k, hostkeys->entries[i].key)) 352 return -1; 353 if (is_cert && 354 key_equal_public(k->cert->signature_key, 355 hostkeys->entries[i].key)) 356 return -1; 357 } 358 return 0; 359 } 360 361 /* 362 * Match keys against a specified key, or look one up by key type. 363 * 364 * If looking for a keytype (key == NULL) and one is found then return 365 * HOST_FOUND, otherwise HOST_NEW. 366 * 367 * If looking for a key (key != NULL): 368 * 1. If the key is a cert and a matching CA is found, return HOST_OK 369 * 2. If the key is not a cert and a matching key is found, return HOST_OK 370 * 3. If no key matches but a key with a different type is found, then 371 * return HOST_CHANGED 372 * 4. If no matching keys are found, then return HOST_NEW. 373 * 374 * Finally, check any found key is not revoked. 375 */ 376 static HostStatus 377 check_hostkeys_by_key_or_type(struct hostkeys *hostkeys, 378 Key *k, int keytype, const struct hostkey_entry **found) 379 { 380 u_int i; 381 HostStatus end_return = HOST_NEW; 382 int want_cert = key_is_cert(k); 383 HostkeyMarker want_marker = want_cert ? MRK_CA : MRK_NONE; 384 int proto = (k ? k->type : keytype) == KEY_RSA1 ? 1 : 2; 385 386 if (found != NULL) 387 *found = NULL; 388 389 for (i = 0; i < hostkeys->num_entries; i++) { 390 if (proto == 1 && hostkeys->entries[i].key->type != KEY_RSA1) 391 continue; 392 if (proto == 2 && hostkeys->entries[i].key->type == KEY_RSA1) 393 continue; 394 if (hostkeys->entries[i].marker != want_marker) 395 continue; 396 if (k == NULL) { 397 if (hostkeys->entries[i].key->type != keytype) 398 continue; 399 end_return = HOST_FOUND; 400 if (found != NULL) 401 *found = hostkeys->entries + i; 402 k = hostkeys->entries[i].key; 403 break; 404 } 405 if (want_cert) { 406 if (key_equal_public(k->cert->signature_key, 407 hostkeys->entries[i].key)) { 408 /* A matching CA exists */ 409 end_return = HOST_OK; 410 if (found != NULL) 411 *found = hostkeys->entries + i; 412 break; 413 } 414 } else { 415 if (key_equal(k, hostkeys->entries[i].key)) { 416 end_return = HOST_OK; 417 if (found != NULL) 418 *found = hostkeys->entries + i; 419 break; 420 } 421 /* A non-maching key exists */ 422 end_return = HOST_CHANGED; 423 if (found != NULL) 424 *found = hostkeys->entries + i; 425 } 426 } 427 if (check_key_not_revoked(hostkeys, k) != 0) { 428 end_return = HOST_REVOKED; 429 if (found != NULL) 430 *found = NULL; 431 } 432 return end_return; 433 } 434 435 HostStatus 436 check_key_in_hostkeys(struct hostkeys *hostkeys, Key *key, 437 const struct hostkey_entry **found) 438 { 439 if (key == NULL) 440 fatal("no key to look up"); 441 return check_hostkeys_by_key_or_type(hostkeys, key, 0, found); 442 } 443 444 int 445 lookup_key_in_hostkeys_by_type(struct hostkeys *hostkeys, int keytype, 446 const struct hostkey_entry **found) 447 { 448 return (check_hostkeys_by_key_or_type(hostkeys, NULL, keytype, 449 found) == HOST_FOUND); 450 } 451 452 /* 453 * Appends an entry to the host file. Returns false if the entry could not 454 * be appended. 455 */ 456 457 int 458 add_host_to_hostfile(const char *filename, const char *host, const Key *key, 459 int store_hash) 460 { 461 FILE *f; 462 int success = 0; 463 char *hashed_host = NULL; 464 465 if (key == NULL) 466 return 1; /* XXX ? */ 467 f = fopen(filename, "a"); 468 if (!f) 469 return 0; 470 471 if (store_hash) { 472 if ((hashed_host = host_hash(host, NULL, 0)) == NULL) { 473 error("add_host_to_hostfile: host_hash failed"); 474 fclose(f); 475 return 0; 476 } 477 } 478 fprintf(f, "%s ", store_hash ? hashed_host : host); 479 480 if (key_write(key, f)) { 481 success = 1; 482 } else { 483 error("add_host_to_hostfile: saving key in %s failed", filename); 484 } 485 fprintf(f, "\n"); 486 fclose(f); 487 return success; 488 } 489
