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 #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
extract_salt(const char * s,u_int l,char * salt,size_t salt_len)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 *
host_hash(const char * host,const char * name_from_hostfile,u_int src_len)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
hostfile_read_key(char ** cpp,u_int * bitsp,Key * ret)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
hostfile_check_key(int bits,const Key * key,const char * host,const char * filename,u_long linenum)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
check_markers(char ** cpp)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 *
init_hostkeys(void)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
load_hostkeys(struct hostkeys * hostkeys,const char * host,const char * path)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
free_hostkeys(struct hostkeys * hostkeys)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
check_key_not_revoked(struct hostkeys * hostkeys,Key * k)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
check_hostkeys_by_key_or_type(struct hostkeys * hostkeys,Key * k,int keytype,const struct hostkey_entry ** found)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
check_key_in_hostkeys(struct hostkeys * hostkeys,Key * key,const struct hostkey_entry ** found)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
lookup_key_in_hostkeys_by_type(struct hostkeys * hostkeys,int keytype,const struct hostkey_entry ** found)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
add_host_to_hostfile(const char * filename,const char * host,const Key * key,int store_hash)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