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 "includes.h" 40 41#include <sys/types.h> 42 43#include <netinet/in.h> 44 45#ifdef __APPLE_CRYPTO__ 46#include "ossl-hmac.h" 47#include "ossl-sha.h" 48#else 49#include <openssl/hmac.h> 50#include <openssl/sha.h> 51#endif 52 53#include <resolv.h> 54#include <stdarg.h> 55#include <stdio.h> 56#include <stdlib.h> 57#include <string.h> 58 59#include "xmalloc.h" 60#include "match.h" 61#include "key.h" 62#include "hostfile.h" 63#include "log.h" 64#include "misc.h" 65 66struct hostkeys { 67 struct hostkey_entry *entries; 68 u_int num_entries; 69}; 70 71static int 72extract_salt(const char *s, u_int l, char *salt, size_t salt_len) 73{ 74 char *p, *b64salt; 75 u_int b64len; 76 int ret; 77 78 if (l < sizeof(HASH_MAGIC) - 1) { 79 debug2("extract_salt: string too short"); 80 return (-1); 81 } 82 if (strncmp(s, HASH_MAGIC, sizeof(HASH_MAGIC) - 1) != 0) { 83 debug2("extract_salt: invalid magic identifier"); 84 return (-1); 85 } 86 s += sizeof(HASH_MAGIC) - 1; 87 l -= sizeof(HASH_MAGIC) - 1; 88 if ((p = memchr(s, HASH_DELIM, l)) == NULL) { 89 debug2("extract_salt: missing salt termination character"); 90 return (-1); 91 } 92 93 b64len = p - s; 94 /* Sanity check */ 95 if (b64len == 0 || b64len > 1024) { 96 debug2("extract_salt: bad encoded salt length %u", b64len); 97 return (-1); 98 } 99 b64salt = xmalloc(1 + b64len); 100 memcpy(b64salt, s, b64len); 101 b64salt[b64len] = '\0'; 102 103 ret = __b64_pton(b64salt, salt, salt_len); 104 xfree(b64salt); 105 if (ret == -1) { 106 debug2("extract_salt: salt decode error"); 107 return (-1); 108 } 109 if (ret != SHA_DIGEST_LENGTH) { 110 debug2("extract_salt: expected salt len %d, got %d", 111 SHA_DIGEST_LENGTH, ret); 112 return (-1); 113 } 114 115 return (0); 116} 117 118char * 119host_hash(const char *host, const char *name_from_hostfile, u_int src_len) 120{ 121 const EVP_MD *md = EVP_sha1(); 122 HMAC_CTX mac_ctx; 123 char salt[256], result[256], uu_salt[512], uu_result[512]; 124 static char encoded[1024]; 125 u_int i, len; 126 127 len = EVP_MD_size(md); 128 129 if (name_from_hostfile == NULL) { 130 /* Create new salt */ 131 for (i = 0; i < len; i++) 132 salt[i] = arc4random(); 133 } else { 134 /* Extract salt from known host entry */ 135 if (extract_salt(name_from_hostfile, src_len, salt, 136 sizeof(salt)) == -1) 137 return (NULL); 138 } 139 140 HMAC_Init(&mac_ctx, salt, len, md); 141 HMAC_Update(&mac_ctx, host, strlen(host)); 142 HMAC_Final(&mac_ctx, result, NULL); 143 HMAC_cleanup(&mac_ctx); 144 145 if (__b64_ntop(salt, len, uu_salt, sizeof(uu_salt)) == -1 || 146 __b64_ntop(result, len, uu_result, sizeof(uu_result)) == -1) 147 fatal("host_hash: __b64_ntop failed"); 148 149 snprintf(encoded, sizeof(encoded), "%s%s%c%s", HASH_MAGIC, uu_salt, 150 HASH_DELIM, uu_result); 151 152 return (encoded); 153} 154 155/* 156 * Parses an RSA (number of bits, e, n) or DSA key from a string. Moves the 157 * pointer over the key. Skips any whitespace at the beginning and at end. 158 */ 159 160int 161hostfile_read_key(char **cpp, u_int *bitsp, Key *ret) 162{ 163 char *cp; 164 165 /* Skip leading whitespace. */ 166 for (cp = *cpp; *cp == ' ' || *cp == '\t'; cp++) 167 ; 168 169 if (key_read(ret, &cp) != 1) 170 return 0; 171 172 /* Skip trailing whitespace. */ 173 for (; *cp == ' ' || *cp == '\t'; cp++) 174 ; 175 176 /* Return results. */ 177 *cpp = cp; 178 if (bitsp != NULL) 179 *bitsp = key_size(ret); 180 return 1; 181} 182 183static int 184hostfile_check_key(int bits, const Key *key, const char *host, 185 const char *filename, u_long linenum) 186{ 187 if (key == NULL || key->type != KEY_RSA1 || key->rsa == NULL) 188 return 1; 189 if (bits != BN_num_bits(key->rsa->n)) { 190 logit("Warning: %s, line %lu: keysize mismatch for host %s: " 191 "actual %d vs. announced %d.", 192 filename, linenum, host, BN_num_bits(key->rsa->n), bits); 193 logit("Warning: replace %d with %d in %s, line %lu.", 194 bits, BN_num_bits(key->rsa->n), filename, linenum); 195 } 196 return 1; 197} 198 199static HostkeyMarker 200check_markers(char **cpp) 201{ 202 char marker[32], *sp, *cp = *cpp; 203 int ret = MRK_NONE; 204 205 while (*cp == '@') { 206 /* Only one marker is allowed */ 207 if (ret != MRK_NONE) 208 return MRK_ERROR; 209 /* Markers are terminated by whitespace */ 210 if ((sp = strchr(cp, ' ')) == NULL && 211 (sp = strchr(cp, '\t')) == NULL) 212 return MRK_ERROR; 213 /* Extract marker for comparison */ 214 if (sp <= cp + 1 || sp >= cp + sizeof(marker)) 215 return MRK_ERROR; 216 memcpy(marker, cp, sp - cp); 217 marker[sp - cp] = '\0'; 218 if (strcmp(marker, CA_MARKER) == 0) 219 ret = MRK_CA; 220 else if (strcmp(marker, REVOKE_MARKER) == 0) 221 ret = MRK_REVOKE; 222 else 223 return MRK_ERROR; 224 225 /* Skip past marker and any whitespace that follows it */ 226 cp = sp; 227 for (; *cp == ' ' || *cp == '\t'; cp++) 228 ; 229 } 230 *cpp = cp; 231 return ret; 232} 233 234struct hostkeys * 235init_hostkeys(void) 236{ 237 struct hostkeys *ret = xcalloc(1, sizeof(*ret)); 238 239 ret->entries = NULL; 240 return ret; 241} 242 243void 244load_hostkeys(struct hostkeys *hostkeys, const char *host, const char *path) 245{ 246 FILE *f; 247 char line[8192]; 248 u_long linenum = 0, num_loaded = 0; 249 char *cp, *cp2, *hashed_host; 250 HostkeyMarker marker; 251 Key *key; 252 int kbits; 253 254 if ((f = fopen(path, "r")) == NULL) 255 return; 256 debug3("%s: loading entries for host \"%.100s\" from file \"%s\"", 257 __func__, host, path); 258 while (read_keyfile_line(f, path, line, sizeof(line), &linenum) == 0) { 259 cp = line; 260 261 /* Skip any leading whitespace, comments and empty lines. */ 262 for (; *cp == ' ' || *cp == '\t'; cp++) 263 ; 264 if (!*cp || *cp == '#' || *cp == '\n') 265 continue; 266 267 if ((marker = check_markers(&cp)) == MRK_ERROR) { 268 verbose("%s: invalid marker at %s:%lu", 269 __func__, path, linenum); 270 continue; 271 } 272 273 /* Find the end of the host name portion. */ 274 for (cp2 = cp; *cp2 && *cp2 != ' ' && *cp2 != '\t'; cp2++) 275 ; 276 277 /* Check if the host name matches. */ 278 if (match_hostname(host, cp, (u_int) (cp2 - cp)) != 1) { 279 if (*cp != HASH_DELIM) 280 continue; 281 hashed_host = host_hash(host, cp, (u_int) (cp2 - cp)); 282 if (hashed_host == NULL) { 283 debug("Invalid hashed host line %lu of %s", 284 linenum, path); 285 continue; 286 } 287 if (strncmp(hashed_host, cp, (u_int) (cp2 - cp)) != 0) 288 continue; 289 } 290 291 /* Got a match. Skip host name. */ 292 cp = cp2; 293 294 /* 295 * Extract the key from the line. This will skip any leading 296 * whitespace. Ignore badly formatted lines. 297 */ 298 key = key_new(KEY_UNSPEC); 299 if (!hostfile_read_key(&cp, &kbits, key)) { 300 key_free(key); 301 key = key_new(KEY_RSA1); 302 if (!hostfile_read_key(&cp, &kbits, key)) { 303 key_free(key); 304 continue; 305 } 306 } 307 if (!hostfile_check_key(kbits, key, host, path, linenum)) 308 continue; 309 310 debug3("%s: found %skey type %s in file %s:%lu", __func__, 311 marker == MRK_NONE ? "" : 312 (marker == MRK_CA ? "ca " : "revoked "), 313 key_type(key), path, linenum); 314 hostkeys->entries = xrealloc(hostkeys->entries, 315 hostkeys->num_entries + 1, sizeof(*hostkeys->entries)); 316 hostkeys->entries[hostkeys->num_entries].host = xstrdup(host); 317 hostkeys->entries[hostkeys->num_entries].file = xstrdup(path); 318 hostkeys->entries[hostkeys->num_entries].line = linenum; 319 hostkeys->entries[hostkeys->num_entries].key = key; 320 hostkeys->entries[hostkeys->num_entries].marker = marker; 321 hostkeys->num_entries++; 322 num_loaded++; 323 } 324 debug3("%s: loaded %lu keys", __func__, num_loaded); 325 fclose(f); 326 return; 327} 328 329void 330free_hostkeys(struct hostkeys *hostkeys) 331{ 332 u_int i; 333 334 for (i = 0; i < hostkeys->num_entries; i++) { 335 xfree(hostkeys->entries[i].host); 336 xfree(hostkeys->entries[i].file); 337 key_free(hostkeys->entries[i].key); 338 bzero(hostkeys->entries + i, sizeof(*hostkeys->entries)); 339 } 340 if (hostkeys->entries != NULL) 341 xfree(hostkeys->entries); 342 hostkeys->entries = NULL; 343 hostkeys->num_entries = 0; 344 xfree(hostkeys); 345} 346 347static int 348check_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 */ 381static HostStatus 382check_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 440HostStatus 441check_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 449int 450lookup_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 462int 463add_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