hostfile.c revision 98941 
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 1.29 2001/12/18 10:04:21 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, 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		log("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		log("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
96HostStatus
97check_host_in_hostfile(const char *filename, const char *host, Key *key,
98    Key *found, int *numret)
99{
100	FILE *f;
101	char line[8192];
102	int linenum = 0;
103	u_int kbits;
104	char *cp, *cp2;
105	HostStatus end_return;
106
107	debug3("check_host_in_hostfile: filename %s", filename);
108	if (key == NULL)
109		fatal("no key to look up");
110	/* Open the file containing the list of known hosts. */
111	f = fopen(filename, "r");
112	if (!f)
113		return HOST_NEW;
114
115	/*
116	 * Return value when the loop terminates.  This is set to
117	 * HOST_CHANGED if we have seen a different key for the host and have
118	 * not found the proper one.
119	 */
120	end_return = HOST_NEW;
121
122	/* Go through the file. */
123	while (fgets(line, sizeof(line), f)) {
124		cp = line;
125		linenum++;
126
127		/* Skip any leading whitespace, comments and empty lines. */
128		for (; *cp == ' ' || *cp == '\t'; cp++)
129			;
130		if (!*cp || *cp == '#' || *cp == '\n')
131			continue;
132
133		/* Find the end of the host name portion. */
134		for (cp2 = cp; *cp2 && *cp2 != ' ' && *cp2 != '\t'; cp2++)
135			;
136
137		/* Check if the host name matches. */
138		if (match_hostname(host, cp, (u_int) (cp2 - cp)) != 1)
139			continue;
140
141		/* Got a match.  Skip host name. */
142		cp = cp2;
143
144		/*
145		 * Extract the key from the line.  This will skip any leading
146		 * whitespace.  Ignore badly formatted lines.
147		 */
148		if (!hostfile_read_key(&cp, &kbits, found))
149			continue;
150		if (!hostfile_check_key(kbits, found, host, filename, linenum))
151			continue;
152
153		if (numret != NULL)
154			*numret = linenum;
155
156		/* Check if the current key is the same as the given key. */
157		if (key_equal(key, found)) {
158			/* Ok, they match. */
159			debug3("check_host_in_hostfile: match line %d", linenum);
160			fclose(f);
161			return HOST_OK;
162		}
163		/*
164		 * They do not match.  We will continue to go through the
165		 * file; however, we note that we will not return that it is
166		 * new.
167		 */
168		end_return = HOST_CHANGED;
169	}
170	/* Clear variables and close the file. */
171	fclose(f);
172
173	/*
174	 * Return either HOST_NEW or HOST_CHANGED, depending on whether we
175	 * saw a different key for the host.
176	 */
177	return end_return;
178}
179
180/*
181 * Appends an entry to the host file.  Returns false if the entry could not
182 * be appended.
183 */
184
185int
186add_host_to_hostfile(const char *filename, const char *host, Key *key)
187{
188	FILE *f;
189	int success = 0;
190	if (key == NULL)
191		return 1;	/* XXX ? */
192	f = fopen(filename, "a");
193	if (!f)
194		return 0;
195	fprintf(f, "%s ", host);
196	if (key_write(key, f)) {
197		success = 1;
198	} else {
199		error("add_host_to_hostfile: saving key in %s failed", filename);
200	}
201	fprintf(f, "\n");
202	fclose(f);
203	return success;
204}
205