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c1cb7bae 1/* $OpenBSD: hostfile.c,v 1.40 2006/03/25 13:17:02 djm Exp $ */
8efc0c15 2/*
5260325f 3 * Author: Tatu Ylonen <ylo@cs.hut.fi>
5260325f 4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5 * All rights reserved
bcbf86ec 6 * Functions for manipulating the known hosts files.
6ae2364d 7 *
bcbf86ec 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".
6ae2364d 13 *
6ae2364d 14 *
a96070d4 15 * Copyright (c) 1999, 2000 Markus Friedl. All rights reserved.
bcbf86ec 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.
5260325f 37 */
8efc0c15 38
39#include "includes.h"
5c63c2ab 40
41#include <resolv.h>
cc63c340 42
5c63c2ab 43#include <openssl/hmac.h>
44#include <openssl/sha.h>
4fe2af09 45
4fe2af09 46#include "match.h"
4fe2af09 47#include "key.h"
48#include "hostfile.h"
42f11eb2 49#include "log.h"
5c63c2ab 50#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) {
18f8ef7a 91 debug2("extract_salt: expected salt len %d, got %d",
92 SHA_DIGEST_LENGTH, ret);
5c63c2ab 93 return (-1);
94 }
f8cc7664 95
5c63c2ab 96 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
f8cc7664 126 if (__b64_ntop(salt, len, uu_salt, sizeof(uu_salt)) == -1 ||
5c63c2ab 127 __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}
8efc0c15 135
aa3378df 136/*
4fe2af09 137 * 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.
aa3378df 139 */
8efc0c15 140
fb396518 141int
1e3b8b07 142hostfile_read_key(char **cpp, u_int *bitsp, Key *ret)
8efc0c15 143{
5260325f 144 char *cp;
145
146 /* Skip leading whitespace. */
aa3378df 147 for (cp = *cpp; *cp == ' ' || *cp == '\t'; cp++)
148 ;
5260325f 149
fa08c86b 150 if (key_read(ret, &cp) != 1)
5260325f 151 return 0;
152
153 /* Skip trailing whitespace. */
aa3378df 154 for (; *cp == ' ' || *cp == '\t'; cp++)
155 ;
5260325f 156
157 /* Return results. */
158 *cpp = cp;
fa08c86b 159 *bitsp = key_size(ret);
5260325f 160 return 1;
8efc0c15 161}
162
396c147e 163static int
b6c7b7b7 164hostfile_check_key(int bits, const Key *key, const char *host, const char *filename, int linenum)
4fe2af09 165{
fa08c86b 166 if (key == NULL || key->type != KEY_RSA1 || key->rsa == NULL)
4fe2af09 167 return 1;
168 if (bits != BN_num_bits(key->rsa->n)) {
bbe88b6d 169 logit("Warning: %s, line %d: keysize mismatch for host %s: "
4fe2af09 170 "actual %d vs. announced %d.",
171 filename, linenum, host, BN_num_bits(key->rsa->n), bits);
bbe88b6d 172 logit("Warning: replace %d with %d in %s, line %d.",
4fe2af09 173 bits, BN_num_bits(key->rsa->n), filename, linenum);
8efc0c15 174 }
4fe2af09 175 return 1;
8efc0c15 176}
177
aa3378df 178/*
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.
8a48a7ef 183 *
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.
aa3378df 186 */
8efc0c15 187
8a48a7ef 188static HostStatus
189check_host_in_hostfile_by_key_or_type(const char *filename,
b6c7b7b7 190 const char *host, const Key *key, int keytype, Key *found, int *numret)
8efc0c15 191{
5260325f 192 FILE *f;
193 char line[8192];
194 int linenum = 0;
d9d49fdb 195 u_int kbits;
5c63c2ab 196 char *cp, *cp2, *hashed_host;
5260325f 197 HostStatus end_return;
198
8002af61 199 debug3("check_host_in_hostfile: filename %s", filename);
8a48a7ef 200
5260325f 201 /* Open the file containing the list of known hosts. */
202 f = fopen(filename, "r");
203 if (!f)
204 return HOST_NEW;
205
aa3378df 206 /*
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 */
5260325f 211 end_return = HOST_NEW;
212
d9d49fdb 213 /* Go through the file. */
5260325f 214 while (fgets(line, sizeof(line), f)) {
215 cp = line;
216 linenum++;
217
aa3378df 218 /* Skip any leading whitespace, comments and empty lines. */
219 for (; *cp == ' ' || *cp == '\t'; cp++)
220 ;
5260325f 221 if (!*cp || *cp == '#' || *cp == '\n')
222 continue;
223
224 /* Find the end of the host name portion. */
aa3378df 225 for (cp2 = cp; *cp2 && *cp2 != ' ' && *cp2 != '\t'; cp2++)
226 ;
5260325f 227
228 /* Check if the host name matches. */
5c63c2ab 229 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 }
5260325f 241
242 /* Got a match. Skip host name. */
243 cp = cp2;
244
aa3378df 245 /*
246 * Extract the key from the line. This will skip any leading
247 * whitespace. Ignore badly formatted lines.
248 */
4fe2af09 249 if (!hostfile_read_key(&cp, &kbits, found))
250 continue;
5260325f 251
1e3b8b07 252 if (numret != NULL)
253 *numret = linenum;
254
8a48a7ef 255 if (key == NULL) {
256 /* we found a key of the requested type */
f8f9ef4d 257 if (found->type == keytype) {
258 fclose(f);
8a48a7ef 259 return HOST_FOUND;
f8f9ef4d 260 }
8a48a7ef 261 continue;
262 }
263
264 if (!hostfile_check_key(kbits, found, host, filename, linenum))
265 continue;
266
5260325f 267 /* Check if the current key is the same as the given key. */
4fe2af09 268 if (key_equal(key, found)) {
5260325f 269 /* Ok, they match. */
8002af61 270 debug3("check_host_in_hostfile: match line %d", linenum);
5260325f 271 fclose(f);
272 return HOST_OK;
273 }
aa3378df 274 /*
275 * They do not match. We will continue to go through the
276 * file; however, we note that we will not return that it is
277 * new.
278 */
5260325f 279 end_return = HOST_CHANGED;
8efc0c15 280 }
5260325f 281 /* Clear variables and close the file. */
282 fclose(f);
283
aa3378df 284 /*
285 * Return either HOST_NEW or HOST_CHANGED, depending on whether we
286 * saw a different key for the host.
287 */
5260325f 288 return end_return;
8efc0c15 289}
290
8a48a7ef 291HostStatus
b6c7b7b7 292check_host_in_hostfile(const char *filename, const char *host, const Key *key,
8a48a7ef 293 Key *found, int *numret)
294{
295 if (key == NULL)
296 fatal("no key to look up");
297 return (check_host_in_hostfile_by_key_or_type(filename, host, key, 0,
298 found, numret));
299}
300
301int
302lookup_key_in_hostfile_by_type(const char *filename, const char *host,
303 int keytype, Key *found, int *numret)
304{
305 return (check_host_in_hostfile_by_key_or_type(filename, host, NULL,
306 keytype, found, numret) == HOST_FOUND);
307}
308
aa3378df 309/*
310 * Appends an entry to the host file. Returns false if the entry could not
311 * be appended.
312 */
8efc0c15 313
314int
f8cc7664 315add_host_to_hostfile(const char *filename, const char *host, const Key *key,
5c63c2ab 316 int store_hash)
8efc0c15 317{
5260325f 318 FILE *f;
4fe2af09 319 int success = 0;
a056dfa2 320 char *hashed_host = NULL;
5c63c2ab 321
4fe2af09 322 if (key == NULL)
a306f2dd 323 return 1; /* XXX ? */
5260325f 324 f = fopen(filename, "a");
325 if (!f)
326 return 0;
5c63c2ab 327
328 if (store_hash) {
329 if ((hashed_host = host_hash(host, NULL, 0)) == NULL) {
330 error("add_host_to_hostfile: host_hash failed");
331 fclose(f);
332 return 0;
333 }
334 }
335 fprintf(f, "%s ", store_hash ? hashed_host : host);
336
4fe2af09 337 if (key_write(key, f)) {
4fe2af09 338 success = 1;
339 } else {
a306f2dd 340 error("add_host_to_hostfile: saving key in %s failed", filename);
5260325f 341 }
a306f2dd 342 fprintf(f, "\n");
5260325f 343 fclose(f);
4fe2af09 344 return success;
8efc0c15 345}
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