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