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3c0ef626 | 1 | /* |
2 | * Author: Tatu Ylonen <ylo@cs.hut.fi> | |
3 | * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland | |
4 | * All rights reserved | |
5 | * Functions for manipulating the known hosts files. | |
6 | * | |
7 | * 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 | * | |
14 | * Copyright (c) 1999, 2000 Markus Friedl. All rights reserved. | |
15 | * 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. | |
36 | */ | |
37 | ||
38 | #include "includes.h" | |
34fee935 | 39 | RCSID("$OpenBSD: hostfile.c,v 1.35 2005/07/27 10:39:03 dtucker Exp $"); |
40 | ||
41 | #include <resolv.h> | |
42 | #include <openssl/hmac.h> | |
43 | #include <openssl/sha.h> | |
3c0ef626 | 44 | |
45 | #include "packet.h" | |
46 | #include "match.h" | |
47 | #include "key.h" | |
48 | #include "hostfile.h" | |
49 | #include "log.h" | |
34fee935 | 50 | #include "xmalloc.h" |
51 | ||
52 | static int | |
53 | extract_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 | } | |
95 | ||
96 | return (0); | |
97 | } | |
98 | ||
99 | char * | |
100 | host_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 | ||
126 | if (__b64_ntop(salt, len, uu_salt, sizeof(uu_salt)) == -1 || | |
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 | } | |
3c0ef626 | 135 | |
136 | /* | |
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. | |
139 | */ | |
140 | ||
e9a17296 | 141 | int |
3c0ef626 | 142 | hostfile_read_key(char **cpp, u_int *bitsp, Key *ret) |
143 | { | |
144 | char *cp; | |
145 | ||
146 | /* Skip leading whitespace. */ | |
147 | for (cp = *cpp; *cp == ' ' || *cp == '\t'; cp++) | |
148 | ; | |
149 | ||
150 | if (key_read(ret, &cp) != 1) | |
151 | return 0; | |
152 | ||
153 | /* Skip trailing whitespace. */ | |
154 | for (; *cp == ' ' || *cp == '\t'; cp++) | |
155 | ; | |
156 | ||
157 | /* Return results. */ | |
158 | *cpp = cp; | |
159 | *bitsp = key_size(ret); | |
160 | return 1; | |
161 | } | |
162 | ||
3c0ef626 | 163 | static int |
416fd2a8 | 164 | hostfile_check_key(int bits, const Key *key, const char *host, const char *filename, int linenum) |
3c0ef626 | 165 | { |
166 | if (key == NULL || key->type != KEY_RSA1 || key->rsa == NULL) | |
167 | return 1; | |
168 | if (bits != BN_num_bits(key->rsa->n)) { | |
70791e56 | 169 | logit("Warning: %s, line %d: keysize mismatch for host %s: " |
3c0ef626 | 170 | "actual %d vs. announced %d.", |
171 | filename, linenum, host, BN_num_bits(key->rsa->n), bits); | |
70791e56 | 172 | logit("Warning: replace %d with %d in %s, line %d.", |
3c0ef626 | 173 | bits, BN_num_bits(key->rsa->n), filename, linenum); |
174 | } | |
175 | return 1; | |
176 | } | |
177 | ||
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. | |
e54b3d7c | 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. | |
3c0ef626 | 186 | */ |
187 | ||
e54b3d7c | 188 | static HostStatus |
189 | check_host_in_hostfile_by_key_or_type(const char *filename, | |
416fd2a8 | 190 | const char *host, const Key *key, int keytype, Key *found, int *numret) |
3c0ef626 | 191 | { |
192 | FILE *f; | |
193 | char line[8192]; | |
194 | int linenum = 0; | |
195 | u_int kbits; | |
34fee935 | 196 | char *cp, *cp2, *hashed_host; |
3c0ef626 | 197 | HostStatus end_return; |
198 | ||
199 | debug3("check_host_in_hostfile: filename %s", filename); | |
e54b3d7c | 200 | |
3c0ef626 | 201 | /* Open the file containing the list of known hosts. */ |
202 | f = fopen(filename, "r"); | |
203 | if (!f) | |
204 | return HOST_NEW; | |
205 | ||
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 | */ | |
211 | end_return = HOST_NEW; | |
212 | ||
213 | /* Go through the file. */ | |
214 | while (fgets(line, sizeof(line), f)) { | |
215 | cp = line; | |
216 | linenum++; | |
217 | ||
218 | /* Skip any leading whitespace, comments and empty lines. */ | |
219 | for (; *cp == ' ' || *cp == '\t'; cp++) | |
220 | ; | |
221 | if (!*cp || *cp == '#' || *cp == '\n') | |
222 | continue; | |
223 | ||
224 | /* Find the end of the host name portion. */ | |
225 | for (cp2 = cp; *cp2 && *cp2 != ' ' && *cp2 != '\t'; cp2++) | |
226 | ; | |
227 | ||
228 | /* Check if the host name matches. */ | |
34fee935 | 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 | } | |
3c0ef626 | 241 | |
242 | /* Got a match. Skip host name. */ | |
243 | cp = cp2; | |
244 | ||
245 | /* | |
246 | * Extract the key from the line. This will skip any leading | |
247 | * whitespace. Ignore badly formatted lines. | |
248 | */ | |
249 | if (!hostfile_read_key(&cp, &kbits, found)) | |
250 | continue; | |
3c0ef626 | 251 | |
252 | if (numret != NULL) | |
253 | *numret = linenum; | |
254 | ||
e54b3d7c | 255 | 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 | ||
3c0ef626 | 265 | /* Check if the current key is the same as the given key. */ |
266 | if (key_equal(key, found)) { | |
267 | /* Ok, they match. */ | |
268 | debug3("check_host_in_hostfile: match line %d", linenum); | |
269 | fclose(f); | |
270 | return HOST_OK; | |
271 | } | |
272 | /* | |
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 | */ | |
277 | end_return = HOST_CHANGED; | |
278 | } | |
279 | /* Clear variables and close the file. */ | |
280 | fclose(f); | |
281 | ||
282 | /* | |
283 | * Return either HOST_NEW or HOST_CHANGED, depending on whether we | |
284 | * saw a different key for the host. | |
285 | */ | |
286 | return end_return; | |
287 | } | |
288 | ||
e54b3d7c | 289 | HostStatus |
416fd2a8 | 290 | check_host_in_hostfile(const char *filename, const char *host, const Key *key, |
e54b3d7c | 291 | 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 | ||
299 | int | |
300 | lookup_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 | ||
3c0ef626 | 307 | /* |
308 | * Appends an entry to the host file. Returns false if the entry could not | |
309 | * be appended. | |
310 | */ | |
311 | ||
312 | int | |
34fee935 | 313 | add_host_to_hostfile(const char *filename, const char *host, const Key *key, |
314 | int store_hash) | |
3c0ef626 | 315 | { |
316 | FILE *f; | |
317 | int success = 0; | |
34fee935 | 318 | char *hashed_host = NULL; |
319 | ||
3c0ef626 | 320 | if (key == NULL) |
321 | return 1; /* XXX ? */ | |
322 | f = fopen(filename, "a"); | |
323 | if (!f) | |
324 | return 0; | |
34fee935 | 325 | |
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 | ||
3c0ef626 | 335 | if (key_write(key, f)) { |
336 | success = 1; | |
337 | } else { | |
338 | error("add_host_to_hostfile: saving key in %s failed", filename); | |
339 | } | |
340 | fprintf(f, "\n"); | |
341 | fclose(f); | |
342 | return success; | |
343 | } |