1 /* $OpenBSD: hostfile.c,v 1.58 2014/10/20 03:43:01 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 <resolv.h> 44 #include <stdio.h> 45 #include <stdlib.h> 46 #include <string.h> 47 #include <stdarg.h> 48 49 #include "xmalloc.h" 50 #include "match.h" 51 #include "key.h" 52 #include "hostfile.h" 53 #include "log.h" 54 #include "misc.h" 55 #include "digest.h" 56 #include "hmac.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, u_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 free(b64salt); 97 if (ret == -1) { 98 debug2("extract_salt: salt decode error"); 99 return (-1); 100 } 101 if (ret != (int)ssh_hmac_bytes(SSH_DIGEST_SHA1)) { 102 debug2("extract_salt: expected salt len %zd, got %d", 103 ssh_hmac_bytes(SSH_DIGEST_SHA1), 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 struct ssh_hmac_ctx *ctx; 114 u_char salt[256], result[256]; 115 char uu_salt[512], uu_result[512]; 116 static char encoded[1024]; 117 u_int i, len; 118 119 len = ssh_digest_bytes(SSH_DIGEST_SHA1); 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 if ((ctx = ssh_hmac_start(SSH_DIGEST_SHA1)) == NULL || 133 ssh_hmac_init(ctx, salt, len) < 0 || 134 ssh_hmac_update(ctx, host, strlen(host)) < 0 || 135 ssh_hmac_final(ctx, result, sizeof(result))) 136 fatal("%s: ssh_hmac failed", __func__); 137 ssh_hmac_free(ctx); 138 139 if (__b64_ntop(salt, len, uu_salt, sizeof(uu_salt)) == -1 || 140 __b64_ntop(result, len, uu_result, sizeof(uu_result)) == -1) 141 fatal("%s: __b64_ntop failed", __func__); 142 143 snprintf(encoded, sizeof(encoded), "%s%s%c%s", HASH_MAGIC, uu_salt, 144 HASH_DELIM, uu_result); 145 146 return (encoded); 147 } 148 149 /* 150 * Parses an RSA (number of bits, e, n) or DSA key from a string. Moves the 151 * pointer over the key. Skips any whitespace at the beginning and at end. 152 */ 153 154 int 155 hostfile_read_key(char **cpp, int *bitsp, Key *ret) 156 { 157 char *cp; 158 159 /* Skip leading whitespace. */ 160 for (cp = *cpp; *cp == ' ' || *cp == '\t'; cp++) 161 ; 162 163 if (key_read(ret, &cp) != 1) 164 return 0; 165 166 /* Skip trailing whitespace. */ 167 for (; *cp == ' ' || *cp == '\t'; cp++) 168 ; 169 170 /* Return results. */ 171 *cpp = cp; 172 if (bitsp != NULL) { 173 if ((*bitsp = key_size(ret)) <= 0) 174 return 0; 175 } 176 return 1; 177 } 178 179 static int 180 hostfile_check_key(int bits, const Key *key, const char *host, 181 const char *filename, u_long linenum) 182 { 183 #ifdef WITH_SSH1 184 if (key == NULL || key->type != KEY_RSA1 || key->rsa == NULL) 185 return 1; 186 if (bits != BN_num_bits(key->rsa->n)) { 187 logit("Warning: %s, line %lu: keysize mismatch for host %s: " 188 "actual %d vs. announced %d.", 189 filename, linenum, host, BN_num_bits(key->rsa->n), bits); 190 logit("Warning: replace %d with %d in %s, line %lu.", 191 bits, BN_num_bits(key->rsa->n), filename, linenum); 192 } 193 #endif 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 #ifdef WITH_SSH1 300 key = key_new(KEY_RSA1); 301 if (!hostfile_read_key(&cp, &kbits, key)) { 302 key_free(key); 303 continue; 304 } 305 #else 306 continue; 307 #endif 308 } 309 if (!hostfile_check_key(kbits, key, host, path, linenum)) 310 continue; 311 312 debug3("%s: found %skey type %s in file %s:%lu", __func__, 313 marker == MRK_NONE ? "" : 314 (marker == MRK_CA ? "ca " : "revoked "), 315 key_type(key), path, linenum); 316 hostkeys->entries = xrealloc(hostkeys->entries, 317 hostkeys->num_entries + 1, sizeof(*hostkeys->entries)); 318 hostkeys->entries[hostkeys->num_entries].host = xstrdup(host); 319 hostkeys->entries[hostkeys->num_entries].file = xstrdup(path); 320 hostkeys->entries[hostkeys->num_entries].line = linenum; 321 hostkeys->entries[hostkeys->num_entries].key = key; 322 hostkeys->entries[hostkeys->num_entries].marker = marker; 323 hostkeys->num_entries++; 324 num_loaded++; 325 } 326 debug3("%s: loaded %lu keys", __func__, num_loaded); 327 fclose(f); 328 return; 329 } 330 331 void 332 free_hostkeys(struct hostkeys *hostkeys) 333 { 334 u_int i; 335 336 for (i = 0; i < hostkeys->num_entries; i++) { 337 free(hostkeys->entries[i].host); 338 free(hostkeys->entries[i].file); 339 key_free(hostkeys->entries[i].key); 340 explicit_bzero(hostkeys->entries + i, sizeof(*hostkeys->entries)); 341 } 342 free(hostkeys->entries); 343 explicit_bzero(hostkeys, sizeof(*hostkeys)); 344 free(hostkeys); 345 } 346 347 static int 348 check_key_not_revoked(struct hostkeys *hostkeys, Key *k) 349 { 350 int is_cert = key_is_cert(k); 351 u_int i; 352 353 for (i = 0; i < hostkeys->num_entries; i++) { 354 if (hostkeys->entries[i].marker != MRK_REVOKE) 355 continue; 356 if (key_equal_public(k, hostkeys->entries[i].key)) 357 return -1; 358 if (is_cert && 359 key_equal_public(k->cert->signature_key, 360 hostkeys->entries[i].key)) 361 return -1; 362 } 363 return 0; 364 } 365 366 /* 367 * Match keys against a specified key, or look one up by key type. 368 * 369 * If looking for a keytype (key == NULL) and one is found then return 370 * HOST_FOUND, otherwise HOST_NEW. 371 * 372 * If looking for a key (key != NULL): 373 * 1. If the key is a cert and a matching CA is found, return HOST_OK 374 * 2. If the key is not a cert and a matching key is found, return HOST_OK 375 * 3. If no key matches but a key with a different type is found, then 376 * return HOST_CHANGED 377 * 4. If no matching keys are found, then return HOST_NEW. 378 * 379 * Finally, check any found key is not revoked. 380 */ 381 static HostStatus 382 check_hostkeys_by_key_or_type(struct hostkeys *hostkeys, 383 Key *k, int keytype, const struct hostkey_entry **found) 384 { 385 u_int i; 386 HostStatus end_return = HOST_NEW; 387 int want_cert = key_is_cert(k); 388 HostkeyMarker want_marker = want_cert ? MRK_CA : MRK_NONE; 389 int proto = (k ? k->type : keytype) == KEY_RSA1 ? 1 : 2; 390 391 if (found != NULL) 392 *found = NULL; 393 394 for (i = 0; i < hostkeys->num_entries; i++) { 395 if (proto == 1 && hostkeys->entries[i].key->type != KEY_RSA1) 396 continue; 397 if (proto == 2 && hostkeys->entries[i].key->type == KEY_RSA1) 398 continue; 399 if (hostkeys->entries[i].marker != want_marker) 400 continue; 401 if (k == NULL) { 402 if (hostkeys->entries[i].key->type != keytype) 403 continue; 404 end_return = HOST_FOUND; 405 if (found != NULL) 406 *found = hostkeys->entries + i; 407 k = hostkeys->entries[i].key; 408 break; 409 } 410 if (want_cert) { 411 if (key_equal_public(k->cert->signature_key, 412 hostkeys->entries[i].key)) { 413 /* A matching CA exists */ 414 end_return = HOST_OK; 415 if (found != NULL) 416 *found = hostkeys->entries + i; 417 break; 418 } 419 } else { 420 if (key_equal(k, hostkeys->entries[i].key)) { 421 end_return = HOST_OK; 422 if (found != NULL) 423 *found = hostkeys->entries + i; 424 break; 425 } 426 /* A non-maching key exists */ 427 end_return = HOST_CHANGED; 428 if (found != NULL) 429 *found = hostkeys->entries + i; 430 } 431 } 432 if (check_key_not_revoked(hostkeys, k) != 0) { 433 end_return = HOST_REVOKED; 434 if (found != NULL) 435 *found = NULL; 436 } 437 return end_return; 438 } 439 440 HostStatus 441 check_key_in_hostkeys(struct hostkeys *hostkeys, Key *key, 442 const struct hostkey_entry **found) 443 { 444 if (key == NULL) 445 fatal("no key to look up"); 446 return check_hostkeys_by_key_or_type(hostkeys, key, 0, found); 447 } 448 449 int 450 lookup_key_in_hostkeys_by_type(struct hostkeys *hostkeys, int keytype, 451 const struct hostkey_entry **found) 452 { 453 return (check_hostkeys_by_key_or_type(hostkeys, NULL, keytype, 454 found) == HOST_FOUND); 455 } 456 457 /* 458 * Appends an entry to the host file. Returns false if the entry could not 459 * be appended. 460 */ 461 462 int 463 add_host_to_hostfile(const char *filename, const char *host, const Key *key, 464 int store_hash) 465 { 466 FILE *f; 467 int success = 0; 468 char *hashed_host = NULL; 469 470 if (key == NULL) 471 return 1; /* XXX ? */ 472 f = fopen(filename, "a"); 473 if (!f) 474 return 0; 475 476 if (store_hash) { 477 if ((hashed_host = host_hash(host, NULL, 0)) == NULL) { 478 error("add_host_to_hostfile: host_hash failed"); 479 fclose(f); 480 return 0; 481 } 482 } 483 fprintf(f, "%s ", store_hash ? hashed_host : host); 484 485 if (key_write(key, f)) { 486 success = 1; 487 } else { 488 error("add_host_to_hostfile: saving key in %s failed", filename); 489 } 490 fprintf(f, "\n"); 491 fclose(f); 492 return success; 493 } 494