hostfile.c revision 126277 
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"
39RCSID("$OpenBSD: hostfile.c,v 1.32 2003/11/10 16:23:41 jakob Exp $");
40
41#include "packet.h"
42#include "match.h"
43#include "key.h"
44#include "hostfile.h"
45#include "log.h"
46
47/*
48 * Parses an RSA (number of bits, e, n) or DSA key from a string.  Moves the
49 * pointer over the key.  Skips any whitespace at the beginning and at end.
50 */
51
52int
53hostfile_read_key(char **cpp, u_int *bitsp, Key *ret)
54{
55	char *cp;
56
57	/* Skip leading whitespace. */
58	for (cp = *cpp; *cp == ' ' || *cp == '\t'; cp++)
59		;
60
61	if (key_read(ret, &cp) != 1)
62		return 0;
63
64	/* Skip trailing whitespace. */
65	for (; *cp == ' ' || *cp == '\t'; cp++)
66		;
67
68	/* Return results. */
69	*cpp = cp;
70	*bitsp = key_size(ret);
71	return 1;
72}
73
74static int
75hostfile_check_key(int bits, const Key *key, const char *host, const char *filename, int linenum)
76{
77	if (key == NULL || key->type != KEY_RSA1 || key->rsa == NULL)
78		return 1;
79	if (bits != BN_num_bits(key->rsa->n)) {
80		logit("Warning: %s, line %d: keysize mismatch for host %s: "
81		    "actual %d vs. announced %d.",
82		    filename, linenum, host, BN_num_bits(key->rsa->n), bits);
83		logit("Warning: replace %d with %d in %s, line %d.",
84		    bits, BN_num_bits(key->rsa->n), filename, linenum);
85	}
86	return 1;
87}
88
89/*
90 * Checks whether the given host (which must be in all lowercase) is already
91 * in the list of our known hosts. Returns HOST_OK if the host is known and
92 * has the specified key, HOST_NEW if the host is not known, and HOST_CHANGED
93 * if the host is known but used to have a different host key.
94 *
95 * If no 'key' has been specified and a key of type 'keytype' is known
96 * for the specified host, then HOST_FOUND is returned.
97 */
98
99static HostStatus
100check_host_in_hostfile_by_key_or_type(const char *filename,
101    const char *host, const Key *key, int keytype, Key *found, int *numret)
102{
103	FILE *f;
104	char line[8192];
105	int linenum = 0;
106	u_int kbits;
107	char *cp, *cp2;
108	HostStatus end_return;
109
110	debug3("check_host_in_hostfile: filename %s", filename);
111
112	/* Open the file containing the list of known hosts. */
113	f = fopen(filename, "r");
114	if (!f)
115		return HOST_NEW;
116
117	/*
118	 * Return value when the loop terminates.  This is set to
119	 * HOST_CHANGED if we have seen a different key for the host and have
120	 * not found the proper one.
121	 */
122	end_return = HOST_NEW;
123
124	/* Go through the file. */
125	while (fgets(line, sizeof(line), f)) {
126		cp = line;
127		linenum++;
128
129		/* Skip any leading whitespace, comments and empty lines. */
130		for (; *cp == ' ' || *cp == '\t'; cp++)
131			;
132		if (!*cp || *cp == '#' || *cp == '\n')
133			continue;
134
135		/* Find the end of the host name portion. */
136		for (cp2 = cp; *cp2 && *cp2 != ' ' && *cp2 != '\t'; cp2++)
137			;
138
139		/* Check if the host name matches. */
140		if (match_hostname(host, cp, (u_int) (cp2 - cp)) != 1)
141			continue;
142
143		/* Got a match.  Skip host name. */
144		cp = cp2;
145
146		/*
147		 * Extract the key from the line.  This will skip any leading
148		 * whitespace.  Ignore badly formatted lines.
149		 */
150		if (!hostfile_read_key(&cp, &kbits, found))
151			continue;
152
153		if (numret != NULL)
154			*numret = linenum;
155
156		if (key == NULL) {
157			/* we found a key of the requested type */
158			if (found->type == keytype)
159				return HOST_FOUND;
160			continue;
161		}
162
163		if (!hostfile_check_key(kbits, found, host, filename, linenum))
164			continue;
165
166		/* Check if the current key is the same as the given key. */
167		if (key_equal(key, found)) {
168			/* Ok, they match. */
169			debug3("check_host_in_hostfile: match line %d", linenum);
170			fclose(f);
171			return HOST_OK;
172		}
173		/*
174		 * They do not match.  We will continue to go through the
175		 * file; however, we note that we will not return that it is
176		 * new.
177		 */
178		end_return = HOST_CHANGED;
179	}
180	/* Clear variables and close the file. */
181	fclose(f);
182
183	/*
184	 * Return either HOST_NEW or HOST_CHANGED, depending on whether we
185	 * saw a different key for the host.
186	 */
187	return end_return;
188}
189
190HostStatus
191check_host_in_hostfile(const char *filename, const char *host, const Key *key,
192    Key *found, int *numret)
193{
194	if (key == NULL)
195		fatal("no key to look up");
196	return (check_host_in_hostfile_by_key_or_type(filename, host, key, 0,
197	    found, numret));
198}
199
200int
201lookup_key_in_hostfile_by_type(const char *filename, const char *host,
202    int keytype, Key *found, int *numret)
203{
204	return (check_host_in_hostfile_by_key_or_type(filename, host, NULL,
205	    keytype, found, numret) == HOST_FOUND);
206}
207
208/*
209 * Appends an entry to the host file.  Returns false if the entry could not
210 * be appended.
211 */
212
213int
214add_host_to_hostfile(const char *filename, const char *host, const Key *key)
215{
216	FILE *f;
217	int success = 0;
218	if (key == NULL)
219		return 1;	/* XXX ? */
220	f = fopen(filename, "a");
221	if (!f)
222		return 0;
223	fprintf(f, "%s ", host);
224	if (key_write(key, f)) {
225		success = 1;
226	} else {
227		error("add_host_to_hostfile: saving key in %s failed", filename);
228	}
229	fprintf(f, "\n");
230	fclose(f);
231	return success;
232}
233