xref: /titanic_44/usr/src/cmd/ssh/libssh/common/hostfile.c (revision 0db3240d392634cfff2f95fb6da34b56b8dc574f)
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 /* $OpenBSD: hostfile.c,v 1.45 2006/08/03 03:34:42 deraadt Exp $ */
39 
40 #pragma ident	"%Z%%M%	%I%	%E% SMI"
41 
42 #include "includes.h"
43 
44 #include <openssl/hmac.h>
45 #include <openssl/sha.h>
46 
47 #include "packet.h"
48 #include "xmalloc.h"
49 #include "match.h"
50 #include "key.h"
51 #include "hostfile.h"
52 #include "log.h"
53 
54 /*
55  * Format of a hashed hostname is <MAGIC><SALT>|<HASHED_HOSTNAME>. <MAGIC> is
56  * "|1|". As in non-hashed hostnames this whole string is then followed by a
57  * space, a key type and the key (which is out of scope of this function).
58  *
59  * Example what can be in 's':
60  *
61  * |1|t17NtsuXSLwP0H0eYdd8vJeNakM=|9XFVPh3jZUrfY6YCWn8Ua5eGZtA=
62  */
63 static int
64 extract_salt(const char *s, u_int l, char *salt, size_t salt_len)
65 {
66 	char *p;
67 	u_char *b64salt;
68 	u_int b64len;
69 	int ret;
70 
71 	if (l < sizeof(HASH_MAGIC) - 1) {
72 		debug2("extract_salt: string too short");
73 		return (-1);
74 	}
75 	if (strncmp(s, HASH_MAGIC, sizeof(HASH_MAGIC) - 1) != 0) {
76 		debug2("extract_salt: invalid magic identifier");
77 		return (-1);
78 	}
79 	s += sizeof(HASH_MAGIC) - 1;
80 	l -= sizeof(HASH_MAGIC) - 1;
81 	if ((p = memchr(s, HASH_DELIM, l)) == NULL) {
82 		debug2("extract_salt: missing salt termination character");
83 		return (-1);
84 	}
85 
86 	b64len = p - s;
87 	/* Sanity check */
88 	if (b64len == 0 || b64len > 1024) {
89 		debug2("extract_salt: bad encoded salt length %u", b64len);
90 		return (-1);
91 	}
92 	b64salt = xmalloc(1 + b64len);
93 	memcpy(b64salt, s, b64len);
94 	b64salt[b64len] = '\0';
95 
96 	ret = __b64_pton(b64salt, (u_char *) salt, salt_len);
97 	xfree(b64salt);
98 	if (ret == -1) {
99 		debug2("extract_salt: salt decode error");
100 		return (-1);
101 	}
102 	if (ret != SHA_DIGEST_LENGTH) {
103 		debug2("extract_salt: expected salt len %d, got %d",
104 		    SHA_DIGEST_LENGTH, ret);
105 		return (-1);
106 	}
107 
108 	return (0);
109 }
110 
111 char *
112 host_hash(const char *host, const char *name_from_hostfile, u_int src_len)
113 {
114 	const EVP_MD *md = EVP_sha1();
115 	HMAC_CTX mac_ctx;
116 	char salt[256], result[256], uu_salt[512], uu_result[512];
117 	static char encoded[1024];
118 	u_int i, len;
119 
120 	len = EVP_MD_size(md);
121 
122 	if (name_from_hostfile == NULL) {
123 		/* Create new salt */
124 		for (i = 0; i < len; i++)
125 			salt[i] = arc4random();
126 	} else {
127 		/* Extract salt from known host entry */
128 		if (extract_salt(name_from_hostfile, src_len, salt,
129 		    sizeof(salt)) == -1)
130 			return (NULL);
131 	}
132 
133 	HMAC_Init(&mac_ctx, salt, len, md);
134 	HMAC_Update(&mac_ctx, (u_char *) host, strlen(host));
135 	HMAC_Final(&mac_ctx, (u_char *) result, NULL);
136 	HMAC_cleanup(&mac_ctx);
137 
138 	if (__b64_ntop((u_char *) salt, len, uu_salt, sizeof(uu_salt)) == -1 ||
139 	    __b64_ntop((u_char *) result, len, uu_result, sizeof(uu_result)) == -1)
140 		fatal("host_hash: __b64_ntop failed");
141 
142 	snprintf(encoded, sizeof(encoded), "%s%s%c%s", HASH_MAGIC, uu_salt,
143 	    HASH_DELIM, uu_result);
144 
145 	return (encoded);
146 }
147 
148 /*
149  * Parses an RSA (number of bits, e, n) or DSA key from a string.  Moves the
150  * pointer over the key.  Skips any whitespace at the beginning and at end.
151  */
152 
153 int
154 hostfile_read_key(char **cpp, u_int *bitsp, Key *ret)
155 {
156 	char *cp;
157 
158 	/* Skip leading whitespace. */
159 	for (cp = *cpp; *cp == ' ' || *cp == '\t'; cp++)
160 		;
161 
162 	if (key_read(ret, &cp) != 1)
163 		return 0;
164 
165 	/* Skip trailing whitespace. */
166 	for (; *cp == ' ' || *cp == '\t'; cp++)
167 		;
168 
169 	/* Return results. */
170 	*cpp = cp;
171 	*bitsp = key_size(ret);
172 	return 1;
173 }
174 
175 static int
176 hostfile_check_key(int bits, const Key *key, const char *host, const char *filename, int linenum)
177 {
178 	if (key == NULL || key->type != KEY_RSA1 || key->rsa == NULL)
179 		return 1;
180 	if (bits != BN_num_bits(key->rsa->n)) {
181 		log("Warning: %s, line %d: keysize mismatch for host %s: "
182 		    "actual %d vs. announced %d.",
183 		    filename, linenum, host, BN_num_bits(key->rsa->n), bits);
184 		log("Warning: replace %d with %d in %s, line %d.",
185 		    bits, BN_num_bits(key->rsa->n), filename, linenum);
186 	}
187 	return 1;
188 }
189 
190 /*
191  * Checks whether the given host (which must be in all lowercase) is already
192  * in the list of our known hosts. Returns HOST_OK if the host is known and
193  * has the specified key, HOST_NEW if the host is not known, and HOST_CHANGED
194  * if the host is known but used to have a different host key.
195  *
196  * If no 'key' has been specified and a key of type 'keytype' is known
197  * for the specified host, then HOST_FOUND is returned.
198  */
199 
200 static HostStatus
201 check_host_in_hostfile_by_key_or_type(const char *filename,
202     const char *host, const Key *key, int keytype, Key *found, int *numret)
203 {
204 	FILE *f;
205 	char line[8192];
206 	int linenum = 0;
207 	u_int kbits;
208 	char *cp, *cp2, *hashed_host;
209 	HostStatus end_return;
210 
211 	debug3("check_host_in_hostfile: filename %s", filename);
212 
213 	/* Open the file containing the list of known hosts. */
214 	f = fopen(filename, "r");
215 	if (!f)
216 		return HOST_NEW;
217 
218 	/*
219 	 * Return value when the loop terminates.  This is set to
220 	 * HOST_CHANGED if we have seen a different key for the host and have
221 	 * not found the proper one.
222 	 */
223 	end_return = HOST_NEW;
224 
225 	/* Go through the file. */
226 	while (fgets(line, sizeof(line), f)) {
227 		cp = line;
228 		linenum++;
229 
230 		/* Skip any leading whitespace, comments and empty lines. */
231 		for (; *cp == ' ' || *cp == '\t'; cp++)
232 			;
233 		if (!*cp || *cp == '#' || *cp == '\n')
234 			continue;
235 
236 		/* Find the end of the host name portion. */
237 		for (cp2 = cp; *cp2 && *cp2 != ' ' && *cp2 != '\t'; cp2++)
238 			;
239 
240 		/* Check if the host name matches. */
241 		if (match_hostname(host, cp, (u_int) (cp2 - cp)) != 1) {
242 			if (*cp != HASH_DELIM)
243 				continue;
244 			hashed_host = host_hash(host, cp, (u_int) (cp2 - cp));
245 			if (hashed_host == NULL) {
246 				debug("Invalid hashed host line %d of %s",
247 				    linenum, filename);
248 				continue;
249 			}
250 			if (strncmp(hashed_host, cp, (u_int) (cp2 - cp)) != 0)
251 				continue;
252 		}
253 
254 		/* Got a match.  Skip host name. */
255 		cp = cp2;
256 
257 		/*
258 		 * Extract the key from the line.  This will skip any leading
259 		 * whitespace.  Ignore badly formatted lines.
260 		 */
261 		if (!hostfile_read_key(&cp, &kbits, found))
262 			continue;
263 
264 		if (numret != NULL)
265 			*numret = linenum;
266 
267 		if (key == NULL) {
268 			/* we found a key of the requested type */
269 			if (found->type == keytype) {
270 				fclose(f);
271 				return HOST_FOUND;
272 			}
273 			continue;
274 		}
275 
276 		if (!hostfile_check_key(kbits, found, host, filename, linenum))
277 			continue;
278 
279 		/* Check if the current key is the same as the given key. */
280 		if (key_equal(key, found)) {
281 			/* Ok, they match. */
282 			debug3("check_host_in_hostfile: match line %d", linenum);
283 			fclose(f);
284 			return HOST_OK;
285 		}
286 		/*
287 		 * They do not match.  We will continue to go through the
288 		 * file; however, we note that we will not return that it is
289 		 * new.
290 		 */
291 		end_return = HOST_CHANGED;
292 	}
293 	/* Clear variables and close the file. */
294 	fclose(f);
295 
296 	/*
297 	 * Return either HOST_NEW or HOST_CHANGED, depending on whether we
298 	 * saw a different key for the host.
299 	 */
300 	return end_return;
301 }
302 
303 HostStatus
304 check_host_in_hostfile(const char *filename, const char *host, const Key *key,
305     Key *found, int *numret)
306 {
307 	if (key == NULL)
308 		fatal("no key to look up");
309 	return (check_host_in_hostfile_by_key_or_type(filename, host, key, 0,
310 	    found, numret));
311 }
312 
313 int
314 lookup_key_in_hostfile_by_type(const char *filename, const char *host,
315     int keytype, Key *found, int *numret)
316 {
317 	return (check_host_in_hostfile_by_key_or_type(filename, host, NULL,
318 	    keytype, found, numret) == HOST_FOUND);
319 }
320 
321 /*
322  * Appends an entry to the host file.  Returns false if the entry could not
323  * be appended.
324  */
325 
326 int
327 add_host_to_hostfile(const char *filename, const char *host, const Key *key,
328     int store_hash)
329 {
330 	FILE *f;
331 	int success = 0;
332 	char *hashed_host = NULL;
333 
334 	if (key == NULL)
335 		return 1;	/* XXX ? */
336 	f = fopen(filename, "a");
337 	if (!f)
338 		return 0;
339 
340 	if (store_hash) {
341 		if ((hashed_host = host_hash(host, NULL, 0)) == NULL) {
342 			error("add_host_to_hostfile: host_hash failed");
343 			fclose(f);
344 			return 0;
345 		}
346 	}
347 	fprintf(f, "%s ", store_hash ? hashed_host : host);
348 
349 	if (key_write(key, f)) {
350 		success = 1;
351 	} else {
352 		error("add_host_to_hostfile: saving key in %s failed", filename);
353 	}
354 	fprintf(f, "\n");
355 	fclose(f);
356 	return success;
357 }
358