1 /* $OpenBSD: hostfile.c,v 1.55 2014/01/31 16:39:19 tedu 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 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 #include "digest.h" 58 #include "hmac.h" 59 60 struct hostkeys { 61 struct hostkey_entry *entries; 62 u_int num_entries; 63 }; 64 65 static int 66 extract_salt(const char *s, u_int l, u_char *salt, size_t salt_len) 67 { 68 char *p, *b64salt; 69 u_int b64len; 70 int ret; 71 72 if (l < sizeof(HASH_MAGIC) - 1) { 73 debug2("extract_salt: string too short"); 74 return (-1); 75 } 76 if (strncmp(s, HASH_MAGIC, sizeof(HASH_MAGIC) - 1) != 0) { 77 debug2("extract_salt: invalid magic identifier"); 78 return (-1); 79 } 80 s += sizeof(HASH_MAGIC) - 1; 81 l -= sizeof(HASH_MAGIC) - 1; 82 if ((p = memchr(s, HASH_DELIM, l)) == NULL) { 83 debug2("extract_salt: missing salt termination character"); 84 return (-1); 85 } 86 87 b64len = p - s; 88 /* Sanity check */ 89 if (b64len == 0 || b64len > 1024) { 90 debug2("extract_salt: bad encoded salt length %u", b64len); 91 return (-1); 92 } 93 b64salt = xmalloc(1 + b64len); 94 memcpy(b64salt, s, b64len); 95 b64salt[b64len] = '\0'; 96 97 ret = __b64_pton(b64salt, salt, salt_len); 98 free(b64salt); 99 if (ret == -1) { 100 debug2("extract_salt: salt decode error"); 101 return (-1); 102 } 103 if (ret != (int)ssh_hmac_bytes(SSH_DIGEST_SHA1)) { 104 debug2("extract_salt: expected salt len %zd, got %d", 105 ssh_hmac_bytes(SSH_DIGEST_SHA1), ret); 106 return (-1); 107 } 108 109 return (0); 110 } 111 112 char * 113 host_hash(const char *host, const char *name_from_hostfile, u_int src_len) 114 { 115 struct ssh_hmac_ctx *ctx; 116 u_char salt[256], result[256]; 117 char uu_salt[512], uu_result[512]; 118 static char encoded[1024]; 119 u_int i, len; 120 121 len = ssh_digest_bytes(SSH_DIGEST_SHA1); 122 123 if (name_from_hostfile == NULL) { 124 /* Create new salt */ 125 for (i = 0; i < len; i++) 126 salt[i] = arc4random(); 127 } else { 128 /* Extract salt from known host entry */ 129 if (extract_salt(name_from_hostfile, src_len, salt, 130 sizeof(salt)) == -1) 131 return (NULL); 132 } 133 134 if ((ctx = ssh_hmac_start(SSH_DIGEST_SHA1)) == NULL || 135 ssh_hmac_init(ctx, salt, len) < 0 || 136 ssh_hmac_update(ctx, host, strlen(host)) < 0 || 137 ssh_hmac_final(ctx, result, sizeof(result))) 138 fatal("%s: ssh_hmac failed", __func__); 139 ssh_hmac_free(ctx); 140 141 if (__b64_ntop(salt, len, uu_salt, sizeof(uu_salt)) == -1 || 142 __b64_ntop(result, len, uu_result, sizeof(uu_result)) == -1) 143 fatal("%s: __b64_ntop failed", __func__); 144 145 snprintf(encoded, sizeof(encoded), "%s%s%c%s", HASH_MAGIC, uu_salt, 146 HASH_DELIM, uu_result); 147 148 return (encoded); 149 } 150 151 /* 152 * Parses an RSA (number of bits, e, n) or DSA key from a string. Moves the 153 * pointer over the key. Skips any whitespace at the beginning and at end. 154 */ 155 156 int 157 hostfile_read_key(char **cpp, int *bitsp, Key *ret) 158 { 159 char *cp; 160 161 /* Skip leading whitespace. */ 162 for (cp = *cpp; *cp == ' ' || *cp == '\t'; cp++) 163 ; 164 165 if (key_read(ret, &cp) != 1) 166 return 0; 167 168 /* Skip trailing whitespace. */ 169 for (; *cp == ' ' || *cp == '\t'; cp++) 170 ; 171 172 /* Return results. */ 173 *cpp = cp; 174 if (bitsp != NULL) { 175 if ((*bitsp = key_size(ret)) <= 0) 176 return 0; 177 } 178 return 1; 179 } 180 181 static int 182 hostfile_check_key(int bits, const Key *key, const char *host, 183 const char *filename, u_long linenum) 184 { 185 if (key == NULL || key->type != KEY_RSA1 || key->rsa == NULL) 186 return 1; 187 if (bits != BN_num_bits(key->rsa->n)) { 188 logit("Warning: %s, line %lu: keysize mismatch for host %s: " 189 "actual %d vs. announced %d.", 190 filename, linenum, host, BN_num_bits(key->rsa->n), bits); 191 logit("Warning: replace %d with %d in %s, line %lu.", 192 bits, BN_num_bits(key->rsa->n), filename, linenum); 193 } 194 return 1; 195 } 196 197 static HostkeyMarker 198 check_markers(char **cpp) 199 { 200 char marker[32], *sp, *cp = *cpp; 201 int ret = MRK_NONE; 202 203 while (*cp == '@') { 204 /* Only one marker is allowed */ 205 if (ret != MRK_NONE) 206 return MRK_ERROR; 207 /* Markers are terminated by whitespace */ 208 if ((sp = strchr(cp, ' ')) == NULL && 209 (sp = strchr(cp, '\t')) == NULL) 210 return MRK_ERROR; 211 /* Extract marker for comparison */ 212 if (sp <= cp + 1 || sp >= cp + sizeof(marker)) 213 return MRK_ERROR; 214 memcpy(marker, cp, sp - cp); 215 marker[sp - cp] = '\0'; 216 if (strcmp(marker, CA_MARKER) == 0) 217 ret = MRK_CA; 218 else if (strcmp(marker, REVOKE_MARKER) == 0) 219 ret = MRK_REVOKE; 220 else 221 return MRK_ERROR; 222 223 /* Skip past marker and any whitespace that follows it */ 224 cp = sp; 225 for (; *cp == ' ' || *cp == '\t'; cp++) 226 ; 227 } 228 *cpp = cp; 229 return ret; 230 } 231 232 struct hostkeys * 233 init_hostkeys(void) 234 { 235 struct hostkeys *ret = xcalloc(1, sizeof(*ret)); 236 237 ret->entries = NULL; 238 return ret; 239 } 240 241 void 242 load_hostkeys(struct hostkeys *hostkeys, const char *host, const char *path) 243 { 244 FILE *f; 245 char line[8192]; 246 u_long linenum = 0, num_loaded = 0; 247 char *cp, *cp2, *hashed_host; 248 HostkeyMarker marker; 249 Key *key; 250 int kbits; 251 252 if ((f = fopen(path, "r")) == NULL) 253 return; 254 debug3("%s: loading entries for host \"%.100s\" from file \"%s\"", 255 __func__, host, path); 256 while (read_keyfile_line(f, path, line, sizeof(line), &linenum) == 0) { 257 cp = line; 258 259 /* Skip any leading whitespace, comments and empty lines. */ 260 for (; *cp == ' ' || *cp == '\t'; cp++) 261 ; 262 if (!*cp || *cp == '#' || *cp == '\n') 263 continue; 264 265 if ((marker = check_markers(&cp)) == MRK_ERROR) { 266 verbose("%s: invalid marker at %s:%lu", 267 __func__, path, linenum); 268 continue; 269 } 270 271 /* Find the end of the host name portion. */ 272 for (cp2 = cp; *cp2 && *cp2 != ' ' && *cp2 != '\t'; cp2++) 273 ; 274 275 /* Check if the host name matches. */ 276 if (match_hostname(host, cp, (u_int) (cp2 - cp)) != 1) { 277 if (*cp != HASH_DELIM) 278 continue; 279 hashed_host = host_hash(host, cp, (u_int) (cp2 - cp)); 280 if (hashed_host == NULL) { 281 debug("Invalid hashed host line %lu of %s", 282 linenum, path); 283 continue; 284 } 285 if (strncmp(hashed_host, cp, (u_int) (cp2 - cp)) != 0) 286 continue; 287 } 288 289 /* Got a match. Skip host name. */ 290 cp = cp2; 291 292 /* 293 * Extract the key from the line. This will skip any leading 294 * whitespace. Ignore badly formatted lines. 295 */ 296 key = key_new(KEY_UNSPEC); 297 if (!hostfile_read_key(&cp, &kbits, key)) { 298 key_free(key); 299 key = key_new(KEY_RSA1); 300 if (!hostfile_read_key(&cp, &kbits, key)) { 301 key_free(key); 302 continue; 303 } 304 } 305 if (!hostfile_check_key(kbits, key, host, path, linenum)) 306 continue; 307 308 debug3("%s: found %skey type %s in file %s:%lu", __func__, 309 marker == MRK_NONE ? "" : 310 (marker == MRK_CA ? "ca " : "revoked "), 311 key_type(key), path, linenum); 312 hostkeys->entries = xrealloc(hostkeys->entries, 313 hostkeys->num_entries + 1, sizeof(*hostkeys->entries)); 314 hostkeys->entries[hostkeys->num_entries].host = xstrdup(host); 315 hostkeys->entries[hostkeys->num_entries].file = xstrdup(path); 316 hostkeys->entries[hostkeys->num_entries].line = linenum; 317 hostkeys->entries[hostkeys->num_entries].key = key; 318 hostkeys->entries[hostkeys->num_entries].marker = marker; 319 hostkeys->num_entries++; 320 num_loaded++; 321 } 322 debug3("%s: loaded %lu keys", __func__, num_loaded); 323 fclose(f); 324 return; 325 } 326 327 void 328 free_hostkeys(struct hostkeys *hostkeys) 329 { 330 u_int i; 331 332 for (i = 0; i < hostkeys->num_entries; i++) { 333 free(hostkeys->entries[i].host); 334 free(hostkeys->entries[i].file); 335 key_free(hostkeys->entries[i].key); 336 explicit_bzero(hostkeys->entries + i, sizeof(*hostkeys->entries)); 337 } 338 free(hostkeys->entries); 339 explicit_bzero(hostkeys, sizeof(*hostkeys)); 340 free(hostkeys); 341 } 342 343 static int 344 check_key_not_revoked(struct hostkeys *hostkeys, Key *k) 345 { 346 int is_cert = key_is_cert(k); 347 u_int i; 348 349 for (i = 0; i < hostkeys->num_entries; i++) { 350 if (hostkeys->entries[i].marker != MRK_REVOKE) 351 continue; 352 if (key_equal_public(k, hostkeys->entries[i].key)) 353 return -1; 354 if (is_cert && 355 key_equal_public(k->cert->signature_key, 356 hostkeys->entries[i].key)) 357 return -1; 358 } 359 return 0; 360 } 361 362 /* 363 * Match keys against a specified key, or look one up by key type. 364 * 365 * If looking for a keytype (key == NULL) and one is found then return 366 * HOST_FOUND, otherwise HOST_NEW. 367 * 368 * If looking for a key (key != NULL): 369 * 1. If the key is a cert and a matching CA is found, return HOST_OK 370 * 2. If the key is not a cert and a matching key is found, return HOST_OK 371 * 3. If no key matches but a key with a different type is found, then 372 * return HOST_CHANGED 373 * 4. If no matching keys are found, then return HOST_NEW. 374 * 375 * Finally, check any found key is not revoked. 376 */ 377 static HostStatus 378 check_hostkeys_by_key_or_type(struct hostkeys *hostkeys, 379 Key *k, int keytype, const struct hostkey_entry **found) 380 { 381 u_int i; 382 HostStatus end_return = HOST_NEW; 383 int want_cert = key_is_cert(k); 384 HostkeyMarker want_marker = want_cert ? MRK_CA : MRK_NONE; 385 int proto = (k ? k->type : keytype) == KEY_RSA1 ? 1 : 2; 386 387 if (found != NULL) 388 *found = NULL; 389 390 for (i = 0; i < hostkeys->num_entries; i++) { 391 if (proto == 1 && hostkeys->entries[i].key->type != KEY_RSA1) 392 continue; 393 if (proto == 2 && hostkeys->entries[i].key->type == KEY_RSA1) 394 continue; 395 if (hostkeys->entries[i].marker != want_marker) 396 continue; 397 if (k == NULL) { 398 if (hostkeys->entries[i].key->type != keytype) 399 continue; 400 end_return = HOST_FOUND; 401 if (found != NULL) 402 *found = hostkeys->entries + i; 403 k = hostkeys->entries[i].key; 404 break; 405 } 406 if (want_cert) { 407 if (key_equal_public(k->cert->signature_key, 408 hostkeys->entries[i].key)) { 409 /* A matching CA exists */ 410 end_return = HOST_OK; 411 if (found != NULL) 412 *found = hostkeys->entries + i; 413 break; 414 } 415 } else { 416 if (key_equal(k, hostkeys->entries[i].key)) { 417 end_return = HOST_OK; 418 if (found != NULL) 419 *found = hostkeys->entries + i; 420 break; 421 } 422 /* A non-maching key exists */ 423 end_return = HOST_CHANGED; 424 if (found != NULL) 425 *found = hostkeys->entries + i; 426 } 427 } 428 if (check_key_not_revoked(hostkeys, k) != 0) { 429 end_return = HOST_REVOKED; 430 if (found != NULL) 431 *found = NULL; 432 } 433 return end_return; 434 } 435 436 HostStatus 437 check_key_in_hostkeys(struct hostkeys *hostkeys, Key *key, 438 const struct hostkey_entry **found) 439 { 440 if (key == NULL) 441 fatal("no key to look up"); 442 return check_hostkeys_by_key_or_type(hostkeys, key, 0, found); 443 } 444 445 int 446 lookup_key_in_hostkeys_by_type(struct hostkeys *hostkeys, int keytype, 447 const struct hostkey_entry **found) 448 { 449 return (check_hostkeys_by_key_or_type(hostkeys, NULL, keytype, 450 found) == HOST_FOUND); 451 } 452 453 /* 454 * Appends an entry to the host file. Returns false if the entry could not 455 * be appended. 456 */ 457 458 int 459 add_host_to_hostfile(const char *filename, const char *host, const Key *key, 460 int store_hash) 461 { 462 FILE *f; 463 int success = 0; 464 char *hashed_host = NULL; 465 466 if (key == NULL) 467 return 1; /* XXX ? */ 468 f = fopen(filename, "a"); 469 if (!f) 470 return 0; 471 472 if (store_hash) { 473 if ((hashed_host = host_hash(host, NULL, 0)) == NULL) { 474 error("add_host_to_hostfile: host_hash failed"); 475 fclose(f); 476 return 0; 477 } 478 } 479 fprintf(f, "%s ", store_hash ? hashed_host : host); 480 481 if (key_write(key, f)) { 482 success = 1; 483 } else { 484 error("add_host_to_hostfile: saving key in %s failed", filename); 485 } 486 fprintf(f, "\n"); 487 fclose(f); 488 return success; 489 } 490