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Damien Millerd4a8b7e1999-10-27 13:42:43 +10001/*
Damien Miller95def091999-11-25 00:26:21 +11002 * Author: Tatu Ylonen <ylo@cs.hut.fi>
Damien Miller95def091999-11-25 00:26:21 +11003 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
4 * All rights reserved
Damien Miller95def091999-11-25 00:26:21 +11005 * Functions for manipulating the known hosts files.
Damien Miller4af51302000-04-16 11:18:38 +10006 *
Damien Millere4340be2000-09-16 13:29:08 +11007 * As far as I am concerned, the code I have written for this software
8 * can be used freely for any purpose. Any derived versions of this
9 * software must be clearly marked as such, and if the derived work is
10 * incompatible with the protocol description in the RFC file, it must be
11 * called by a name other than "ssh" or "Secure Shell".
12 *
13 *
Ben Lindstrom44697232001-07-04 03:32:30 +000014 * Copyright (c) 1999, 2000 Markus Friedl. All rights reserved.
Damien Millere4340be2000-09-16 13:29:08 +110015 * Copyright (c) 1999 Niels Provos. All rights reserved.
16 *
17 * Redistribution and use in source and binary forms, with or without
18 * modification, are permitted provided that the following conditions
19 * are met:
20 * 1. Redistributions of source code must retain the above copyright
21 * notice, this list of conditions and the following disclaimer.
22 * 2. Redistributions in binary form must reproduce the above copyright
23 * notice, this list of conditions and the following disclaimer in the
24 * documentation and/or other materials provided with the distribution.
25 *
26 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
27 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
28 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
29 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
30 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
31 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
32 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
33 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
34 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
35 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
Damien Miller95def091999-11-25 00:26:21 +110036 */
Damien Millerd4a8b7e1999-10-27 13:42:43 +100037
38#include "includes.h"
Darren Tucker47eede72005-03-14 23:08:12 +110039RCSID("$OpenBSD: hostfile.c,v 1.34 2005/03/10 22:01:05 deraadt Exp $");
Damien Millere1776152005-03-01 21:47:37 +110040
41#include <resolv.h>
42#include <openssl/hmac.h>
43#include <openssl/sha.h>
Damien Miller450a7a12000-03-26 13:04:51 +100044
Damien Millerd4a8b7e1999-10-27 13:42:43 +100045#include "packet.h"
Damien Miller450a7a12000-03-26 13:04:51 +100046#include "match.h"
Damien Miller450a7a12000-03-26 13:04:51 +100047#include "key.h"
48#include "hostfile.h"
Ben Lindstrom226cfa02001-01-22 05:34:40 +000049#include "log.h"
Damien Millere1776152005-03-01 21:47:37 +110050#include "xmalloc.h"
51
52static int
53extract_salt(const char *s, u_int l, char *salt, size_t salt_len)
54{
55 char *p, *b64salt;
56 u_int b64len;
57 int ret;
58
59 if (l < sizeof(HASH_MAGIC) - 1) {
60 debug2("extract_salt: string too short");
61 return (-1);
62 }
63 if (strncmp(s, HASH_MAGIC, sizeof(HASH_MAGIC) - 1) != 0) {
64 debug2("extract_salt: invalid magic identifier");
65 return (-1);
66 }
67 s += sizeof(HASH_MAGIC) - 1;
68 l -= sizeof(HASH_MAGIC) - 1;
69 if ((p = memchr(s, HASH_DELIM, l)) == NULL) {
70 debug2("extract_salt: missing salt termination character");
71 return (-1);
72 }
73
74 b64len = p - s;
75 /* Sanity check */
76 if (b64len == 0 || b64len > 1024) {
77 debug2("extract_salt: bad encoded salt length %u", b64len);
78 return (-1);
79 }
80 b64salt = xmalloc(1 + b64len);
81 memcpy(b64salt, s, b64len);
82 b64salt[b64len] = '\0';
83
84 ret = __b64_pton(b64salt, salt, salt_len);
85 xfree(b64salt);
86 if (ret == -1) {
87 debug2("extract_salt: salt decode error");
88 return (-1);
89 }
90 if (ret != SHA_DIGEST_LENGTH) {
91 debug2("extract_salt: expected salt len %u, got %u",
92 salt_len, ret);
93 return (-1);
94 }
Darren Tucker47eede72005-03-14 23:08:12 +110095
Damien Millere1776152005-03-01 21:47:37 +110096 return (0);
97}
98
99char *
100host_hash(const char *host, const char *name_from_hostfile, u_int src_len)
101{
102 const EVP_MD *md = EVP_sha1();
103 HMAC_CTX mac_ctx;
104 char salt[256], result[256], uu_salt[512], uu_result[512];
105 static char encoded[1024];
106 u_int i, len;
107
108 len = EVP_MD_size(md);
109
110 if (name_from_hostfile == NULL) {
111 /* Create new salt */
112 for (i = 0; i < len; i++)
113 salt[i] = arc4random();
114 } else {
115 /* Extract salt from known host entry */
116 if (extract_salt(name_from_hostfile, src_len, salt,
117 sizeof(salt)) == -1)
118 return (NULL);
119 }
120
121 HMAC_Init(&mac_ctx, salt, len, md);
122 HMAC_Update(&mac_ctx, host, strlen(host));
123 HMAC_Final(&mac_ctx, result, NULL);
124 HMAC_cleanup(&mac_ctx);
125
Darren Tucker47eede72005-03-14 23:08:12 +1100126 if (__b64_ntop(salt, len, uu_salt, sizeof(uu_salt)) == -1 ||
Damien Millere1776152005-03-01 21:47:37 +1100127 __b64_ntop(result, len, uu_result, sizeof(uu_result)) == -1)
128 fatal("host_hash: __b64_ntop failed");
129
130 snprintf(encoded, sizeof(encoded), "%s%s%c%s", HASH_MAGIC, uu_salt,
131 HASH_DELIM, uu_result);
132
133 return (encoded);
134}
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000135
Damien Miller5428f641999-11-25 11:54:57 +1100136/*
Damien Miller450a7a12000-03-26 13:04:51 +1000137 * Parses an RSA (number of bits, e, n) or DSA key from a string. Moves the
138 * pointer over the key. Skips any whitespace at the beginning and at end.
Damien Miller5428f641999-11-25 11:54:57 +1100139 */
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000140
Damien Miller5b2aea92001-12-21 12:47:09 +1100141int
Ben Lindstrom46c16222000-12-22 01:43:59 +0000142hostfile_read_key(char **cpp, u_int *bitsp, Key *ret)
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000143{
Damien Miller95def091999-11-25 00:26:21 +1100144 char *cp;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000145
Damien Miller95def091999-11-25 00:26:21 +1100146 /* Skip leading whitespace. */
Damien Miller5428f641999-11-25 11:54:57 +1100147 for (cp = *cpp; *cp == ' ' || *cp == '\t'; cp++)
148 ;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000149
Damien Miller0bc1bd82000-11-13 22:57:25 +1100150 if (key_read(ret, &cp) != 1)
Damien Miller95def091999-11-25 00:26:21 +1100151 return 0;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000152
Damien Miller95def091999-11-25 00:26:21 +1100153 /* Skip trailing whitespace. */
Damien Miller5428f641999-11-25 11:54:57 +1100154 for (; *cp == ' ' || *cp == '\t'; cp++)
155 ;
Damien Miller95def091999-11-25 00:26:21 +1100156
157 /* Return results. */
158 *cpp = cp;
Damien Miller0bc1bd82000-11-13 22:57:25 +1100159 *bitsp = key_size(ret);
Damien Miller95def091999-11-25 00:26:21 +1100160 return 1;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000161}
162
Ben Lindstrombba81212001-06-25 05:01:22 +0000163static int
Damien Millerf58b58c2003-11-17 21:18:23 +1100164hostfile_check_key(int bits, const Key *key, const char *host, const char *filename, int linenum)
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000165{
Damien Miller0bc1bd82000-11-13 22:57:25 +1100166 if (key == NULL || key->type != KEY_RSA1 || key->rsa == NULL)
Damien Miller450a7a12000-03-26 13:04:51 +1000167 return 1;
168 if (bits != BN_num_bits(key->rsa->n)) {
Damien Miller996acd22003-04-09 20:59:48 +1000169 logit("Warning: %s, line %d: keysize mismatch for host %s: "
Damien Miller450a7a12000-03-26 13:04:51 +1000170 "actual %d vs. announced %d.",
171 filename, linenum, host, BN_num_bits(key->rsa->n), bits);
Damien Miller996acd22003-04-09 20:59:48 +1000172 logit("Warning: replace %d with %d in %s, line %d.",
Damien Miller450a7a12000-03-26 13:04:51 +1000173 bits, BN_num_bits(key->rsa->n), filename, linenum);
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000174 }
Damien Miller450a7a12000-03-26 13:04:51 +1000175 return 1;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000176}
177
Damien Miller5428f641999-11-25 11:54:57 +1100178/*
179 * Checks whether the given host (which must be in all lowercase) is already
180 * in the list of our known hosts. Returns HOST_OK if the host is known and
181 * has the specified key, HOST_NEW if the host is not known, and HOST_CHANGED
182 * if the host is known but used to have a different host key.
Ben Lindstrom3ed66402002-08-01 01:21:56 +0000183 *
184 * If no 'key' has been specified and a key of type 'keytype' is known
185 * for the specified host, then HOST_FOUND is returned.
Damien Miller5428f641999-11-25 11:54:57 +1100186 */
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000187
Ben Lindstrom3ed66402002-08-01 01:21:56 +0000188static HostStatus
189check_host_in_hostfile_by_key_or_type(const char *filename,
Damien Millerf58b58c2003-11-17 21:18:23 +1100190 const char *host, const Key *key, int keytype, Key *found, int *numret)
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000191{
Damien Miller95def091999-11-25 00:26:21 +1100192 FILE *f;
193 char line[8192];
194 int linenum = 0;
Ben Lindstromab0cedc2001-04-07 17:23:43 +0000195 u_int kbits;
Damien Millere1776152005-03-01 21:47:37 +1100196 char *cp, *cp2, *hashed_host;
Damien Miller95def091999-11-25 00:26:21 +1100197 HostStatus end_return;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000198
Ben Lindstrom5eabda32001-04-12 23:34:34 +0000199 debug3("check_host_in_hostfile: filename %s", filename);
Ben Lindstrom3ed66402002-08-01 01:21:56 +0000200
Damien Miller95def091999-11-25 00:26:21 +1100201 /* Open the file containing the list of known hosts. */
202 f = fopen(filename, "r");
203 if (!f)
204 return HOST_NEW;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000205
Damien Miller5428f641999-11-25 11:54:57 +1100206 /*
207 * Return value when the loop terminates. This is set to
208 * HOST_CHANGED if we have seen a different key for the host and have
209 * not found the proper one.
210 */
Damien Miller95def091999-11-25 00:26:21 +1100211 end_return = HOST_NEW;
Damien Miller7e8e8201999-11-16 13:37:16 +1100212
Ben Lindstromab0cedc2001-04-07 17:23:43 +0000213 /* Go through the file. */
Damien Miller95def091999-11-25 00:26:21 +1100214 while (fgets(line, sizeof(line), f)) {
215 cp = line;
216 linenum++;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000217
Damien Miller5428f641999-11-25 11:54:57 +1100218 /* Skip any leading whitespace, comments and empty lines. */
219 for (; *cp == ' ' || *cp == '\t'; cp++)
220 ;
Damien Miller95def091999-11-25 00:26:21 +1100221 if (!*cp || *cp == '#' || *cp == '\n')
222 continue;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000223
Damien Miller95def091999-11-25 00:26:21 +1100224 /* Find the end of the host name portion. */
Damien Miller5428f641999-11-25 11:54:57 +1100225 for (cp2 = cp; *cp2 && *cp2 != ' ' && *cp2 != '\t'; cp2++)
226 ;
Damien Miller7e8e8201999-11-16 13:37:16 +1100227
Damien Miller95def091999-11-25 00:26:21 +1100228 /* Check if the host name matches. */
Damien Millere1776152005-03-01 21:47:37 +1100229 if (match_hostname(host, cp, (u_int) (cp2 - cp)) != 1) {
230 if (*cp != HASH_DELIM)
231 continue;
232 hashed_host = host_hash(host, cp, (u_int) (cp2 - cp));
233 if (hashed_host == NULL) {
234 debug("Invalid hashed host line %d of %s",
235 linenum, filename);
236 continue;
237 }
238 if (strncmp(hashed_host, cp, (u_int) (cp2 - cp)) != 0)
239 continue;
240 }
Damien Miller95def091999-11-25 00:26:21 +1100241
242 /* Got a match. Skip host name. */
243 cp = cp2;
244
Damien Miller5428f641999-11-25 11:54:57 +1100245 /*
246 * Extract the key from the line. This will skip any leading
247 * whitespace. Ignore badly formatted lines.
248 */
Damien Miller450a7a12000-03-26 13:04:51 +1000249 if (!hostfile_read_key(&cp, &kbits, found))
250 continue;
Damien Miller95def091999-11-25 00:26:21 +1100251
Ben Lindstrom46c16222000-12-22 01:43:59 +0000252 if (numret != NULL)
253 *numret = linenum;
254
Ben Lindstrom3ed66402002-08-01 01:21:56 +0000255 if (key == NULL) {
256 /* we found a key of the requested type */
257 if (found->type == keytype)
258 return HOST_FOUND;
259 continue;
260 }
261
262 if (!hostfile_check_key(kbits, found, host, filename, linenum))
263 continue;
264
Damien Miller95def091999-11-25 00:26:21 +1100265 /* Check if the current key is the same as the given key. */
Damien Miller450a7a12000-03-26 13:04:51 +1000266 if (key_equal(key, found)) {
Damien Miller95def091999-11-25 00:26:21 +1100267 /* Ok, they match. */
Ben Lindstrom5eabda32001-04-12 23:34:34 +0000268 debug3("check_host_in_hostfile: match line %d", linenum);
Damien Miller95def091999-11-25 00:26:21 +1100269 fclose(f);
270 return HOST_OK;
271 }
Damien Miller5428f641999-11-25 11:54:57 +1100272 /*
273 * They do not match. We will continue to go through the
274 * file; however, we note that we will not return that it is
275 * new.
276 */
Damien Miller95def091999-11-25 00:26:21 +1100277 end_return = HOST_CHANGED;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000278 }
Damien Miller95def091999-11-25 00:26:21 +1100279 /* Clear variables and close the file. */
280 fclose(f);
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000281
Damien Miller5428f641999-11-25 11:54:57 +1100282 /*
283 * Return either HOST_NEW or HOST_CHANGED, depending on whether we
284 * saw a different key for the host.
285 */
Damien Miller95def091999-11-25 00:26:21 +1100286 return end_return;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000287}
288
Ben Lindstrom3ed66402002-08-01 01:21:56 +0000289HostStatus
Damien Millerf58b58c2003-11-17 21:18:23 +1100290check_host_in_hostfile(const char *filename, const char *host, const Key *key,
Ben Lindstrom3ed66402002-08-01 01:21:56 +0000291 Key *found, int *numret)
292{
293 if (key == NULL)
294 fatal("no key to look up");
295 return (check_host_in_hostfile_by_key_or_type(filename, host, key, 0,
296 found, numret));
297}
298
299int
300lookup_key_in_hostfile_by_type(const char *filename, const char *host,
301 int keytype, Key *found, int *numret)
302{
303 return (check_host_in_hostfile_by_key_or_type(filename, host, NULL,
304 keytype, found, numret) == HOST_FOUND);
305}
306
Damien Miller5428f641999-11-25 11:54:57 +1100307/*
308 * Appends an entry to the host file. Returns false if the entry could not
309 * be appended.
310 */
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000311
312int
Darren Tucker47eede72005-03-14 23:08:12 +1100313add_host_to_hostfile(const char *filename, const char *host, const Key *key,
Damien Millere1776152005-03-01 21:47:37 +1100314 int store_hash)
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000315{
Damien Miller95def091999-11-25 00:26:21 +1100316 FILE *f;
Damien Miller450a7a12000-03-26 13:04:51 +1000317 int success = 0;
Damien Millere1776152005-03-01 21:47:37 +1100318 char *hashed_host;
319
Damien Miller450a7a12000-03-26 13:04:51 +1000320 if (key == NULL)
Damien Millereba71ba2000-04-29 23:57:08 +1000321 return 1; /* XXX ? */
Damien Miller95def091999-11-25 00:26:21 +1100322 f = fopen(filename, "a");
323 if (!f)
324 return 0;
Damien Millere1776152005-03-01 21:47:37 +1100325
326 if (store_hash) {
327 if ((hashed_host = host_hash(host, NULL, 0)) == NULL) {
328 error("add_host_to_hostfile: host_hash failed");
329 fclose(f);
330 return 0;
331 }
332 }
333 fprintf(f, "%s ", store_hash ? hashed_host : host);
334
Damien Miller450a7a12000-03-26 13:04:51 +1000335 if (key_write(key, f)) {
Damien Miller450a7a12000-03-26 13:04:51 +1000336 success = 1;
337 } else {
Damien Millereba71ba2000-04-29 23:57:08 +1000338 error("add_host_to_hostfile: saving key in %s failed", filename);
Damien Miller95def091999-11-25 00:26:21 +1100339 }
Damien Millereba71ba2000-04-29 23:57:08 +1000340 fprintf(f, "\n");
Damien Miller95def091999-11-25 00:26:21 +1100341 fclose(f);
Damien Miller450a7a12000-03-26 13:04:51 +1000342 return success;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000343}