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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" | |
39 | RCSID("$OpenBSD: hostfile.c,v 1.28 2001/06/25 08:25:37 markus 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 | ||
52 | static int | |
53 | hostfile_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 | ||
74 | int | |
75 | auth_rsa_read_key(char **cpp, u_int *bitsp, BIGNUM * e, BIGNUM * n) | |
76 | { | |
77 | Key *k = key_new(KEY_RSA1); | |
78 | int ret = hostfile_read_key(cpp, bitsp, k); | |
79 | BN_copy(e, k->rsa->e); | |
80 | BN_copy(n, k->rsa->n); | |
81 | key_free(k); | |
82 | return ret; | |
83 | } | |
84 | ||
85 | static int | |
86 | hostfile_check_key(int bits, Key *key, const char *host, const char *filename, int linenum) | |
87 | { | |
88 | if (key == NULL || key->type != KEY_RSA1 || key->rsa == NULL) | |
89 | return 1; | |
90 | if (bits != BN_num_bits(key->rsa->n)) { | |
91 | log("Warning: %s, line %d: keysize mismatch for host %s: " | |
92 | "actual %d vs. announced %d.", | |
93 | filename, linenum, host, BN_num_bits(key->rsa->n), bits); | |
94 | log("Warning: replace %d with %d in %s, line %d.", | |
95 | bits, BN_num_bits(key->rsa->n), filename, linenum); | |
96 | } | |
97 | return 1; | |
98 | } | |
99 | ||
100 | /* | |
101 | * Checks whether the given host (which must be in all lowercase) is already | |
102 | * in the list of our known hosts. Returns HOST_OK if the host is known and | |
103 | * has the specified key, HOST_NEW if the host is not known, and HOST_CHANGED | |
104 | * if the host is known but used to have a different host key. | |
105 | */ | |
106 | ||
107 | HostStatus | |
108 | check_host_in_hostfile(const char *filename, const char *host, Key *key, | |
109 | Key *found, int *numret) | |
110 | { | |
111 | FILE *f; | |
112 | char line[8192]; | |
113 | int linenum = 0; | |
114 | u_int kbits; | |
115 | char *cp, *cp2; | |
116 | HostStatus end_return; | |
117 | ||
118 | debug3("check_host_in_hostfile: filename %s", filename); | |
119 | if (key == NULL) | |
120 | fatal("no key to look up"); | |
121 | /* Open the file containing the list of known hosts. */ | |
122 | f = fopen(filename, "r"); | |
123 | if (!f) | |
124 | return HOST_NEW; | |
125 | ||
126 | /* | |
127 | * Return value when the loop terminates. This is set to | |
128 | * HOST_CHANGED if we have seen a different key for the host and have | |
129 | * not found the proper one. | |
130 | */ | |
131 | end_return = HOST_NEW; | |
132 | ||
133 | /* Go through the file. */ | |
134 | while (fgets(line, sizeof(line), f)) { | |
135 | cp = line; | |
136 | linenum++; | |
137 | ||
138 | /* Skip any leading whitespace, comments and empty lines. */ | |
139 | for (; *cp == ' ' || *cp == '\t'; cp++) | |
140 | ; | |
141 | if (!*cp || *cp == '#' || *cp == '\n') | |
142 | continue; | |
143 | ||
144 | /* Find the end of the host name portion. */ | |
145 | for (cp2 = cp; *cp2 && *cp2 != ' ' && *cp2 != '\t'; cp2++) | |
146 | ; | |
147 | ||
148 | /* Check if the host name matches. */ | |
149 | if (match_hostname(host, cp, (u_int) (cp2 - cp)) != 1) | |
150 | continue; | |
151 | ||
152 | /* Got a match. Skip host name. */ | |
153 | cp = cp2; | |
154 | ||
155 | /* | |
156 | * Extract the key from the line. This will skip any leading | |
157 | * whitespace. Ignore badly formatted lines. | |
158 | */ | |
159 | if (!hostfile_read_key(&cp, &kbits, found)) | |
160 | continue; | |
161 | if (!hostfile_check_key(kbits, found, host, filename, linenum)) | |
162 | continue; | |
163 | ||
164 | if (numret != NULL) | |
165 | *numret = linenum; | |
166 | ||
167 | /* Check if the current key is the same as the given key. */ | |
168 | if (key_equal(key, found)) { | |
169 | /* Ok, they match. */ | |
170 | debug3("check_host_in_hostfile: match line %d", linenum); | |
171 | fclose(f); | |
172 | return HOST_OK; | |
173 | } | |
174 | /* | |
175 | * They do not match. We will continue to go through the | |
176 | * file; however, we note that we will not return that it is | |
177 | * new. | |
178 | */ | |
179 | end_return = HOST_CHANGED; | |
180 | } | |
181 | /* Clear variables and close the file. */ | |
182 | fclose(f); | |
183 | ||
184 | /* | |
185 | * Return either HOST_NEW or HOST_CHANGED, depending on whether we | |
186 | * saw a different key for the host. | |
187 | */ | |
188 | return end_return; | |
189 | } | |
190 | ||
191 | /* | |
192 | * Appends an entry to the host file. Returns false if the entry could not | |
193 | * be appended. | |
194 | */ | |
195 | ||
196 | int | |
197 | add_host_to_hostfile(const char *filename, const char *host, Key *key) | |
198 | { | |
199 | FILE *f; | |
200 | int success = 0; | |
201 | if (key == NULL) | |
202 | return 1; /* XXX ? */ | |
203 | f = fopen(filename, "a"); | |
204 | if (!f) | |
205 | return 0; | |
206 | fprintf(f, "%s ", host); | |
207 | if (key_write(key, f)) { | |
208 | success = 1; | |
209 | } else { | |
210 | error("add_host_to_hostfile: saving key in %s failed", filename); | |
211 | } | |
212 | fprintf(f, "\n"); | |
213 | fclose(f); | |
214 | return success; | |
215 | } |