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1 | /* $OpenBSD: hostfile.c,v 1.43 2006/07/26 13:57:17 stevesk 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 <openssl/hmac.h> | |
46 | #include <openssl/sha.h> | |
47 | ||
48 | #include <resolv.h> | |
49 | #include <stdlib.h> | |
50 | #include <string.h> | |
51 | ||
52 | #include "match.h" | |
53 | #include "key.h" | |
54 | #include "hostfile.h" | |
55 | #include "log.h" | |
56 | #include "xmalloc.h" | |
57 | ||
58 | static int | |
59 | extract_salt(const char *s, u_int l, char *salt, size_t salt_len) | |
60 | { | |
61 | char *p, *b64salt; | |
62 | u_int b64len; | |
63 | int ret; | |
64 | ||
65 | if (l < sizeof(HASH_MAGIC) - 1) { | |
66 | debug2("extract_salt: string too short"); | |
67 | return (-1); | |
68 | } | |
69 | if (strncmp(s, HASH_MAGIC, sizeof(HASH_MAGIC) - 1) != 0) { | |
70 | debug2("extract_salt: invalid magic identifier"); | |
71 | return (-1); | |
72 | } | |
73 | s += sizeof(HASH_MAGIC) - 1; | |
74 | l -= sizeof(HASH_MAGIC) - 1; | |
75 | if ((p = memchr(s, HASH_DELIM, l)) == NULL) { | |
76 | debug2("extract_salt: missing salt termination character"); | |
77 | return (-1); | |
78 | } | |
79 | ||
80 | b64len = p - s; | |
81 | /* Sanity check */ | |
82 | if (b64len == 0 || b64len > 1024) { | |
83 | debug2("extract_salt: bad encoded salt length %u", b64len); | |
84 | return (-1); | |
85 | } | |
86 | b64salt = xmalloc(1 + b64len); | |
87 | memcpy(b64salt, s, b64len); | |
88 | b64salt[b64len] = '\0'; | |
89 | ||
90 | ret = __b64_pton(b64salt, salt, salt_len); | |
91 | xfree(b64salt); | |
92 | if (ret == -1) { | |
93 | debug2("extract_salt: salt decode error"); | |
94 | return (-1); | |
95 | } | |
96 | if (ret != SHA_DIGEST_LENGTH) { | |
97 | debug2("extract_salt: expected salt len %d, got %d", | |
98 | SHA_DIGEST_LENGTH, ret); | |
99 | return (-1); | |
100 | } | |
101 | ||
102 | return (0); | |
103 | } | |
104 | ||
105 | char * | |
106 | host_hash(const char *host, const char *name_from_hostfile, u_int src_len) | |
107 | { | |
108 | const EVP_MD *md = EVP_sha1(); | |
109 | HMAC_CTX mac_ctx; | |
110 | char salt[256], result[256], uu_salt[512], uu_result[512]; | |
111 | static char encoded[1024]; | |
112 | u_int i, len; | |
113 | ||
114 | len = EVP_MD_size(md); | |
115 | ||
116 | if (name_from_hostfile == NULL) { | |
117 | /* Create new salt */ | |
118 | for (i = 0; i < len; i++) | |
119 | salt[i] = arc4random(); | |
120 | } else { | |
121 | /* Extract salt from known host entry */ | |
122 | if (extract_salt(name_from_hostfile, src_len, salt, | |
123 | sizeof(salt)) == -1) | |
124 | return (NULL); | |
125 | } | |
126 | ||
127 | HMAC_Init(&mac_ctx, salt, len, md); | |
128 | HMAC_Update(&mac_ctx, host, strlen(host)); | |
129 | HMAC_Final(&mac_ctx, result, NULL); | |
130 | HMAC_cleanup(&mac_ctx); | |
131 | ||
132 | if (__b64_ntop(salt, len, uu_salt, sizeof(uu_salt)) == -1 || | |
133 | __b64_ntop(result, len, uu_result, sizeof(uu_result)) == -1) | |
134 | fatal("host_hash: __b64_ntop failed"); | |
135 | ||
136 | snprintf(encoded, sizeof(encoded), "%s%s%c%s", HASH_MAGIC, uu_salt, | |
137 | HASH_DELIM, uu_result); | |
138 | ||
139 | return (encoded); | |
140 | } | |
141 | ||
142 | /* | |
143 | * Parses an RSA (number of bits, e, n) or DSA key from a string. Moves the | |
144 | * pointer over the key. Skips any whitespace at the beginning and at end. | |
145 | */ | |
146 | ||
147 | int | |
148 | hostfile_read_key(char **cpp, u_int *bitsp, Key *ret) | |
149 | { | |
150 | char *cp; | |
151 | ||
152 | /* Skip leading whitespace. */ | |
153 | for (cp = *cpp; *cp == ' ' || *cp == '\t'; cp++) | |
154 | ; | |
155 | ||
156 | if (key_read(ret, &cp) != 1) | |
157 | return 0; | |
158 | ||
159 | /* Skip trailing whitespace. */ | |
160 | for (; *cp == ' ' || *cp == '\t'; cp++) | |
161 | ; | |
162 | ||
163 | /* Return results. */ | |
164 | *cpp = cp; | |
165 | *bitsp = key_size(ret); | |
166 | return 1; | |
167 | } | |
168 | ||
169 | static int | |
170 | hostfile_check_key(int bits, const Key *key, const char *host, const char *filename, int linenum) | |
171 | { | |
172 | if (key == NULL || key->type != KEY_RSA1 || key->rsa == NULL) | |
173 | return 1; | |
174 | if (bits != BN_num_bits(key->rsa->n)) { | |
175 | logit("Warning: %s, line %d: keysize mismatch for host %s: " | |
176 | "actual %d vs. announced %d.", | |
177 | filename, linenum, host, BN_num_bits(key->rsa->n), bits); | |
178 | logit("Warning: replace %d with %d in %s, line %d.", | |
179 | bits, BN_num_bits(key->rsa->n), filename, linenum); | |
180 | } | |
181 | return 1; | |
182 | } | |
183 | ||
184 | /* | |
185 | * Checks whether the given host (which must be in all lowercase) is already | |
186 | * in the list of our known hosts. Returns HOST_OK if the host is known and | |
187 | * has the specified key, HOST_NEW if the host is not known, and HOST_CHANGED | |
188 | * if the host is known but used to have a different host key. | |
189 | * | |
190 | * If no 'key' has been specified and a key of type 'keytype' is known | |
191 | * for the specified host, then HOST_FOUND is returned. | |
192 | */ | |
193 | ||
194 | static HostStatus | |
195 | check_host_in_hostfile_by_key_or_type(const char *filename, | |
196 | const char *host, const Key *key, int keytype, Key *found, int *numret) | |
197 | { | |
198 | FILE *f; | |
199 | char line[8192]; | |
200 | int linenum = 0; | |
201 | u_int kbits; | |
202 | char *cp, *cp2, *hashed_host; | |
203 | HostStatus end_return; | |
204 | ||
205 | debug3("check_host_in_hostfile: filename %s", filename); | |
206 | ||
207 | /* Open the file containing the list of known hosts. */ | |
208 | f = fopen(filename, "r"); | |
209 | if (!f) | |
210 | return HOST_NEW; | |
211 | ||
212 | /* | |
213 | * Return value when the loop terminates. This is set to | |
214 | * HOST_CHANGED if we have seen a different key for the host and have | |
215 | * not found the proper one. | |
216 | */ | |
217 | end_return = HOST_NEW; | |
218 | ||
219 | /* Go through the file. */ | |
220 | while (fgets(line, sizeof(line), f)) { | |
221 | cp = line; | |
222 | linenum++; | |
223 | ||
224 | /* Skip any leading whitespace, comments and empty lines. */ | |
225 | for (; *cp == ' ' || *cp == '\t'; cp++) | |
226 | ; | |
227 | if (!*cp || *cp == '#' || *cp == '\n') | |
228 | continue; | |
229 | ||
230 | /* Find the end of the host name portion. */ | |
231 | for (cp2 = cp; *cp2 && *cp2 != ' ' && *cp2 != '\t'; cp2++) | |
232 | ; | |
233 | ||
234 | /* Check if the host name matches. */ | |
235 | if (match_hostname(host, cp, (u_int) (cp2 - cp)) != 1) { | |
236 | if (*cp != HASH_DELIM) | |
237 | continue; | |
238 | hashed_host = host_hash(host, cp, (u_int) (cp2 - cp)); | |
239 | if (hashed_host == NULL) { | |
240 | debug("Invalid hashed host line %d of %s", | |
241 | linenum, filename); | |
242 | continue; | |
243 | } | |
244 | if (strncmp(hashed_host, cp, (u_int) (cp2 - cp)) != 0) | |
245 | continue; | |
246 | } | |
247 | ||
248 | /* Got a match. Skip host name. */ | |
249 | cp = cp2; | |
250 | ||
251 | /* | |
252 | * Extract the key from the line. This will skip any leading | |
253 | * whitespace. Ignore badly formatted lines. | |
254 | */ | |
255 | if (!hostfile_read_key(&cp, &kbits, found)) | |
256 | continue; | |
257 | ||
258 | if (numret != NULL) | |
259 | *numret = linenum; | |
260 | ||
261 | if (key == NULL) { | |
262 | /* we found a key of the requested type */ | |
263 | if (found->type == keytype) { | |
264 | fclose(f); | |
265 | return HOST_FOUND; | |
266 | } | |
267 | continue; | |
268 | } | |
269 | ||
270 | if (!hostfile_check_key(kbits, found, host, filename, linenum)) | |
271 | continue; | |
272 | ||
273 | /* Check if the current key is the same as the given key. */ | |
274 | if (key_equal(key, found)) { | |
275 | /* Ok, they match. */ | |
276 | debug3("check_host_in_hostfile: match line %d", linenum); | |
277 | fclose(f); | |
278 | return HOST_OK; | |
279 | } | |
280 | /* | |
281 | * They do not match. We will continue to go through the | |
282 | * file; however, we note that we will not return that it is | |
283 | * new. | |
284 | */ | |
285 | end_return = HOST_CHANGED; | |
286 | } | |
287 | /* Clear variables and close the file. */ | |
288 | fclose(f); | |
289 | ||
290 | /* | |
291 | * Return either HOST_NEW or HOST_CHANGED, depending on whether we | |
292 | * saw a different key for the host. | |
293 | */ | |
294 | return end_return; | |
295 | } | |
296 | ||
297 | HostStatus | |
298 | check_host_in_hostfile(const char *filename, const char *host, const Key *key, | |
299 | Key *found, int *numret) | |
300 | { | |
301 | if (key == NULL) | |
302 | fatal("no key to look up"); | |
303 | return (check_host_in_hostfile_by_key_or_type(filename, host, key, 0, | |
304 | found, numret)); | |
305 | } | |
306 | ||
307 | int | |
308 | lookup_key_in_hostfile_by_type(const char *filename, const char *host, | |
309 | int keytype, Key *found, int *numret) | |
310 | { | |
311 | return (check_host_in_hostfile_by_key_or_type(filename, host, NULL, | |
312 | keytype, found, numret) == HOST_FOUND); | |
313 | } | |
314 | ||
315 | /* | |
316 | * Appends an entry to the host file. Returns false if the entry could not | |
317 | * be appended. | |
318 | */ | |
319 | ||
320 | int | |
321 | add_host_to_hostfile(const char *filename, const char *host, const Key *key, | |
322 | int store_hash) | |
323 | { | |
324 | FILE *f; | |
325 | int success = 0; | |
326 | char *hashed_host = NULL; | |
327 | ||
328 | if (key == NULL) | |
329 | return 1; /* XXX ? */ | |
330 | f = fopen(filename, "a"); | |
331 | if (!f) | |
332 | return 0; | |
333 | ||
334 | if (store_hash) { | |
335 | if ((hashed_host = host_hash(host, NULL, 0)) == NULL) { | |
336 | error("add_host_to_hostfile: host_hash failed"); | |
337 | fclose(f); | |
338 | return 0; | |
339 | } | |
340 | } | |
341 | fprintf(f, "%s ", store_hash ? hashed_host : host); | |
342 | ||
343 | if (key_write(key, f)) { | |
344 | success = 1; | |
345 | } else { | |
346 | error("add_host_to_hostfile: saving key in %s failed", filename); | |
347 | } | |
348 | fprintf(f, "\n"); | |
349 | fclose(f); | |
350 | return success; | |
351 | } |