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9794d008 1/* $OpenBSD: hostfile.c,v 1.41 2006/07/05 02:42:09 stevesk 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
9794d008 41#include <sys/types.h>
42
43#include <netinet/in.h>
44
5c63c2ab 45#include <resolv.h>
cc63c340 46
5c63c2ab 47#include <openssl/hmac.h>
48#include <openssl/sha.h>
4fe2af09 49
4fe2af09 50#include "match.h"
4fe2af09 51#include "key.h"
52#include "hostfile.h"
42f11eb2 53#include "log.h"
5c63c2ab 54#include "xmalloc.h"
55
56static int
57extract_salt(const char *s, u_int l, char *salt, size_t salt_len)
58{
59 char *p, *b64salt;
60 u_int b64len;
61 int ret;
62
63 if (l < sizeof(HASH_MAGIC) - 1) {
64 debug2("extract_salt: string too short");
65 return (-1);
66 }
67 if (strncmp(s, HASH_MAGIC, sizeof(HASH_MAGIC) - 1) != 0) {
68 debug2("extract_salt: invalid magic identifier");
69 return (-1);
70 }
71 s += sizeof(HASH_MAGIC) - 1;
72 l -= sizeof(HASH_MAGIC) - 1;
73 if ((p = memchr(s, HASH_DELIM, l)) == NULL) {
74 debug2("extract_salt: missing salt termination character");
75 return (-1);
76 }
77
78 b64len = p - s;
79 /* Sanity check */
80 if (b64len == 0 || b64len > 1024) {
81 debug2("extract_salt: bad encoded salt length %u", b64len);
82 return (-1);
83 }
84 b64salt = xmalloc(1 + b64len);
85 memcpy(b64salt, s, b64len);
86 b64salt[b64len] = '\0';
87
88 ret = __b64_pton(b64salt, salt, salt_len);
89 xfree(b64salt);
90 if (ret == -1) {
91 debug2("extract_salt: salt decode error");
92 return (-1);
93 }
94 if (ret != SHA_DIGEST_LENGTH) {
18f8ef7a 95 debug2("extract_salt: expected salt len %d, got %d",
96 SHA_DIGEST_LENGTH, ret);
5c63c2ab 97 return (-1);
98 }
f8cc7664 99
5c63c2ab 100 return (0);
101}
102
103char *
104host_hash(const char *host, const char *name_from_hostfile, u_int src_len)
105{
106 const EVP_MD *md = EVP_sha1();
107 HMAC_CTX mac_ctx;
108 char salt[256], result[256], uu_salt[512], uu_result[512];
109 static char encoded[1024];
110 u_int i, len;
111
112 len = EVP_MD_size(md);
113
114 if (name_from_hostfile == NULL) {
115 /* Create new salt */
116 for (i = 0; i < len; i++)
117 salt[i] = arc4random();
118 } else {
119 /* Extract salt from known host entry */
120 if (extract_salt(name_from_hostfile, src_len, salt,
121 sizeof(salt)) == -1)
122 return (NULL);
123 }
124
125 HMAC_Init(&mac_ctx, salt, len, md);
126 HMAC_Update(&mac_ctx, host, strlen(host));
127 HMAC_Final(&mac_ctx, result, NULL);
128 HMAC_cleanup(&mac_ctx);
129
f8cc7664 130 if (__b64_ntop(salt, len, uu_salt, sizeof(uu_salt)) == -1 ||
5c63c2ab 131 __b64_ntop(result, len, uu_result, sizeof(uu_result)) == -1)
132 fatal("host_hash: __b64_ntop failed");
133
134 snprintf(encoded, sizeof(encoded), "%s%s%c%s", HASH_MAGIC, uu_salt,
135 HASH_DELIM, uu_result);
136
137 return (encoded);
138}
8efc0c15 139
aa3378df 140/*
4fe2af09 141 * Parses an RSA (number of bits, e, n) or DSA key from a string. Moves the
142 * pointer over the key. Skips any whitespace at the beginning and at end.
aa3378df 143 */
8efc0c15 144
fb396518 145int
1e3b8b07 146hostfile_read_key(char **cpp, u_int *bitsp, Key *ret)
8efc0c15 147{
5260325f 148 char *cp;
149
150 /* Skip leading whitespace. */
aa3378df 151 for (cp = *cpp; *cp == ' ' || *cp == '\t'; cp++)
152 ;
5260325f 153
fa08c86b 154 if (key_read(ret, &cp) != 1)
5260325f 155 return 0;
156
157 /* Skip trailing whitespace. */
aa3378df 158 for (; *cp == ' ' || *cp == '\t'; cp++)
159 ;
5260325f 160
161 /* Return results. */
162 *cpp = cp;
fa08c86b 163 *bitsp = key_size(ret);
5260325f 164 return 1;
8efc0c15 165}
166
396c147e 167static int
b6c7b7b7 168hostfile_check_key(int bits, const Key *key, const char *host, const char *filename, int linenum)
4fe2af09 169{
fa08c86b 170 if (key == NULL || key->type != KEY_RSA1 || key->rsa == NULL)
4fe2af09 171 return 1;
172 if (bits != BN_num_bits(key->rsa->n)) {
bbe88b6d 173 logit("Warning: %s, line %d: keysize mismatch for host %s: "
4fe2af09 174 "actual %d vs. announced %d.",
175 filename, linenum, host, BN_num_bits(key->rsa->n), bits);
bbe88b6d 176 logit("Warning: replace %d with %d in %s, line %d.",
4fe2af09 177 bits, BN_num_bits(key->rsa->n), filename, linenum);
8efc0c15 178 }
4fe2af09 179 return 1;
8efc0c15 180}
181
aa3378df 182/*
183 * Checks whether the given host (which must be in all lowercase) is already
184 * in the list of our known hosts. Returns HOST_OK if the host is known and
185 * has the specified key, HOST_NEW if the host is not known, and HOST_CHANGED
186 * if the host is known but used to have a different host key.
8a48a7ef 187 *
188 * If no 'key' has been specified and a key of type 'keytype' is known
189 * for the specified host, then HOST_FOUND is returned.
aa3378df 190 */
8efc0c15 191
8a48a7ef 192static HostStatus
193check_host_in_hostfile_by_key_or_type(const char *filename,
b6c7b7b7 194 const char *host, const Key *key, int keytype, Key *found, int *numret)
8efc0c15 195{
5260325f 196 FILE *f;
197 char line[8192];
198 int linenum = 0;
d9d49fdb 199 u_int kbits;
5c63c2ab 200 char *cp, *cp2, *hashed_host;
5260325f 201 HostStatus end_return;
202
8002af61 203 debug3("check_host_in_hostfile: filename %s", filename);
8a48a7ef 204
5260325f 205 /* Open the file containing the list of known hosts. */
206 f = fopen(filename, "r");
207 if (!f)
208 return HOST_NEW;
209
aa3378df 210 /*
211 * Return value when the loop terminates. This is set to
212 * HOST_CHANGED if we have seen a different key for the host and have
213 * not found the proper one.
214 */
5260325f 215 end_return = HOST_NEW;
216
d9d49fdb 217 /* Go through the file. */
5260325f 218 while (fgets(line, sizeof(line), f)) {
219 cp = line;
220 linenum++;
221
aa3378df 222 /* Skip any leading whitespace, comments and empty lines. */
223 for (; *cp == ' ' || *cp == '\t'; cp++)
224 ;
5260325f 225 if (!*cp || *cp == '#' || *cp == '\n')
226 continue;
227
228 /* Find the end of the host name portion. */
aa3378df 229 for (cp2 = cp; *cp2 && *cp2 != ' ' && *cp2 != '\t'; cp2++)
230 ;
5260325f 231
232 /* Check if the host name matches. */
5c63c2ab 233 if (match_hostname(host, cp, (u_int) (cp2 - cp)) != 1) {
234 if (*cp != HASH_DELIM)
235 continue;
236 hashed_host = host_hash(host, cp, (u_int) (cp2 - cp));
237 if (hashed_host == NULL) {
238 debug("Invalid hashed host line %d of %s",
239 linenum, filename);
240 continue;
241 }
242 if (strncmp(hashed_host, cp, (u_int) (cp2 - cp)) != 0)
243 continue;
244 }
5260325f 245
246 /* Got a match. Skip host name. */
247 cp = cp2;
248
aa3378df 249 /*
250 * Extract the key from the line. This will skip any leading
251 * whitespace. Ignore badly formatted lines.
252 */
4fe2af09 253 if (!hostfile_read_key(&cp, &kbits, found))
254 continue;
5260325f 255
1e3b8b07 256 if (numret != NULL)
257 *numret = linenum;
258
8a48a7ef 259 if (key == NULL) {
260 /* we found a key of the requested type */
f8f9ef4d 261 if (found->type == keytype) {
262 fclose(f);
8a48a7ef 263 return HOST_FOUND;
f8f9ef4d 264 }
8a48a7ef 265 continue;
266 }
267
268 if (!hostfile_check_key(kbits, found, host, filename, linenum))
269 continue;
270
5260325f 271 /* Check if the current key is the same as the given key. */
4fe2af09 272 if (key_equal(key, found)) {
5260325f 273 /* Ok, they match. */
8002af61 274 debug3("check_host_in_hostfile: match line %d", linenum);
5260325f 275 fclose(f);
276 return HOST_OK;
277 }
aa3378df 278 /*
279 * They do not match. We will continue to go through the
280 * file; however, we note that we will not return that it is
281 * new.
282 */
5260325f 283 end_return = HOST_CHANGED;
8efc0c15 284 }
5260325f 285 /* Clear variables and close the file. */
286 fclose(f);
287
aa3378df 288 /*
289 * Return either HOST_NEW or HOST_CHANGED, depending on whether we
290 * saw a different key for the host.
291 */
5260325f 292 return end_return;
8efc0c15 293}
294
8a48a7ef 295HostStatus
b6c7b7b7 296check_host_in_hostfile(const char *filename, const char *host, const Key *key,
8a48a7ef 297 Key *found, int *numret)
298{
299 if (key == NULL)
300 fatal("no key to look up");
301 return (check_host_in_hostfile_by_key_or_type(filename, host, key, 0,
302 found, numret));
303}
304
305int
306lookup_key_in_hostfile_by_type(const char *filename, const char *host,
307 int keytype, Key *found, int *numret)
308{
309 return (check_host_in_hostfile_by_key_or_type(filename, host, NULL,
310 keytype, found, numret) == HOST_FOUND);
311}
312
aa3378df 313/*
314 * Appends an entry to the host file. Returns false if the entry could not
315 * be appended.
316 */
8efc0c15 317
318int
f8cc7664 319add_host_to_hostfile(const char *filename, const char *host, const Key *key,
5c63c2ab 320 int store_hash)
8efc0c15 321{
5260325f 322 FILE *f;
4fe2af09 323 int success = 0;
a056dfa2 324 char *hashed_host = NULL;
5c63c2ab 325
4fe2af09 326 if (key == NULL)
a306f2dd 327 return 1; /* XXX ? */
5260325f 328 f = fopen(filename, "a");
329 if (!f)
330 return 0;
5c63c2ab 331
332 if (store_hash) {
333 if ((hashed_host = host_hash(host, NULL, 0)) == NULL) {
334 error("add_host_to_hostfile: host_hash failed");
335 fclose(f);
336 return 0;
337 }
338 }
339 fprintf(f, "%s ", store_hash ? hashed_host : host);
340
4fe2af09 341 if (key_write(key, f)) {
4fe2af09 342 success = 1;
343 } else {
a306f2dd 344 error("add_host_to_hostfile: saving key in %s failed", filename);
5260325f 345 }
a306f2dd 346 fprintf(f, "\n");
5260325f 347 fclose(f);
4fe2af09 348 return success;
8efc0c15 349}
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