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1 | /* | |
2 | * | |
3 | * hostfile.c | |
4 | * | |
5 | * Author: Tatu Ylonen <ylo@cs.hut.fi> | |
6 | * | |
7 | * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland | |
8 | * All rights reserved | |
9 | * | |
10 | * Created: Thu Jun 29 07:10:56 1995 ylo | |
11 | * | |
12 | * Functions for manipulating the known hosts files. | |
13 | * | |
14 | */ | |
15 | ||
16 | #include "includes.h" | |
17 | RCSID("$OpenBSD: hostfile.c,v 1.16 2000/04/14 10:30:31 markus Exp $"); | |
18 | ||
19 | #include "packet.h" | |
20 | #include "match.h" | |
21 | #include "ssh.h" | |
22 | #include <openssl/rsa.h> | |
23 | #include <openssl/dsa.h> | |
24 | #include "key.h" | |
25 | #include "hostfile.h" | |
26 | ||
27 | /* | |
28 | * Parses an RSA (number of bits, e, n) or DSA key from a string. Moves the | |
29 | * pointer over the key. Skips any whitespace at the beginning and at end. | |
30 | */ | |
31 | ||
32 | int | |
33 | hostfile_read_key(char **cpp, unsigned int *bitsp, Key *ret) | |
34 | { | |
35 | unsigned int bits; | |
36 | char *cp; | |
37 | ||
38 | /* Skip leading whitespace. */ | |
39 | for (cp = *cpp; *cp == ' ' || *cp == '\t'; cp++) | |
40 | ; | |
41 | ||
42 | /* Get number of bits. */ | |
43 | if (*cp < '0' || *cp > '9') | |
44 | return 0; /* Bad bit count... */ | |
45 | for (bits = 0; *cp >= '0' && *cp <= '9'; cp++) | |
46 | bits = 10 * bits + *cp - '0'; | |
47 | ||
48 | if (!key_read(ret, bits, &cp)) | |
49 | return 0; | |
50 | ||
51 | /* Skip trailing whitespace. */ | |
52 | for (; *cp == ' ' || *cp == '\t'; cp++) | |
53 | ; | |
54 | ||
55 | /* Return results. */ | |
56 | *cpp = cp; | |
57 | *bitsp = bits; | |
58 | return 1; | |
59 | } | |
60 | ||
61 | int | |
62 | auth_rsa_read_key(char **cpp, unsigned int *bitsp, BIGNUM * e, BIGNUM * n) | |
63 | { | |
64 | Key *k = key_new(KEY_RSA); | |
65 | int ret = hostfile_read_key(cpp, bitsp, k); | |
66 | BN_copy(e, k->rsa->e); | |
67 | BN_copy(n, k->rsa->n); | |
68 | key_free(k); | |
69 | return ret; | |
70 | } | |
71 | ||
72 | int | |
73 | hostfile_check_key(int bits, Key *key, const char *host, const char *filename, int linenum) | |
74 | { | |
75 | if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) | |
76 | return 1; | |
77 | if (bits != BN_num_bits(key->rsa->n)) { | |
78 | error("Warning: %s, line %d: keysize mismatch for host %s: " | |
79 | "actual %d vs. announced %d.", | |
80 | filename, linenum, host, BN_num_bits(key->rsa->n), bits); | |
81 | error("Warning: replace %d with %d in %s, line %d.", | |
82 | bits, BN_num_bits(key->rsa->n), filename, linenum); | |
83 | } | |
84 | return 1; | |
85 | } | |
86 | ||
87 | /* | |
88 | * Checks whether the given host (which must be in all lowercase) is already | |
89 | * in the list of our known hosts. Returns HOST_OK if the host is known and | |
90 | * has the specified key, HOST_NEW if the host is not known, and HOST_CHANGED | |
91 | * if the host is known but used to have a different host key. | |
92 | */ | |
93 | ||
94 | HostStatus | |
95 | check_host_in_hostfile(const char *filename, const char *host, Key *key, Key *found) | |
96 | { | |
97 | FILE *f; | |
98 | char line[8192]; | |
99 | int linenum = 0; | |
100 | unsigned int kbits, hostlen; | |
101 | char *cp, *cp2; | |
102 | HostStatus end_return; | |
103 | ||
104 | if (key == NULL) | |
105 | fatal("no key to look up"); | |
106 | /* Open the file containing the list of known hosts. */ | |
107 | f = fopen(filename, "r"); | |
108 | if (!f) | |
109 | return HOST_NEW; | |
110 | ||
111 | /* Cache the length of the host name. */ | |
112 | hostlen = strlen(host); | |
113 | ||
114 | /* | |
115 | * Return value when the loop terminates. This is set to | |
116 | * HOST_CHANGED if we have seen a different key for the host and have | |
117 | * not found the proper one. | |
118 | */ | |
119 | end_return = HOST_NEW; | |
120 | ||
121 | /* Go trough the file. */ | |
122 | while (fgets(line, sizeof(line), f)) { | |
123 | cp = line; | |
124 | linenum++; | |
125 | ||
126 | /* Skip any leading whitespace, comments and empty lines. */ | |
127 | for (; *cp == ' ' || *cp == '\t'; cp++) | |
128 | ; | |
129 | if (!*cp || *cp == '#' || *cp == '\n') | |
130 | continue; | |
131 | ||
132 | /* Find the end of the host name portion. */ | |
133 | for (cp2 = cp; *cp2 && *cp2 != ' ' && *cp2 != '\t'; cp2++) | |
134 | ; | |
135 | ||
136 | /* Check if the host name matches. */ | |
137 | if (!match_hostname(host, cp, (unsigned int) (cp2 - cp))) | |
138 | continue; | |
139 | ||
140 | /* Got a match. Skip host name. */ | |
141 | cp = cp2; | |
142 | ||
143 | /* | |
144 | * Extract the key from the line. This will skip any leading | |
145 | * whitespace. Ignore badly formatted lines. | |
146 | */ | |
147 | if (!hostfile_read_key(&cp, &kbits, found)) | |
148 | continue; | |
149 | if (!hostfile_check_key(kbits, found, host, filename, linenum)) | |
150 | continue; | |
151 | ||
152 | /* Check if the current key is the same as the given key. */ | |
153 | if (key_equal(key, found)) { | |
154 | /* Ok, they match. */ | |
155 | fclose(f); | |
156 | return HOST_OK; | |
157 | } | |
158 | /* | |
159 | * They do not match. We will continue to go through the | |
160 | * file; however, we note that we will not return that it is | |
161 | * new. | |
162 | */ | |
163 | end_return = HOST_CHANGED; | |
164 | } | |
165 | /* Clear variables and close the file. */ | |
166 | fclose(f); | |
167 | ||
168 | /* | |
169 | * Return either HOST_NEW or HOST_CHANGED, depending on whether we | |
170 | * saw a different key for the host. | |
171 | */ | |
172 | return end_return; | |
173 | } | |
174 | ||
175 | /* | |
176 | * Appends an entry to the host file. Returns false if the entry could not | |
177 | * be appended. | |
178 | */ | |
179 | ||
180 | int | |
181 | add_host_to_hostfile(const char *filename, const char *host, Key *key) | |
182 | { | |
183 | FILE *f; | |
184 | int success = 0; | |
185 | ||
186 | if (key == NULL) | |
187 | return 1; | |
188 | ||
189 | /* Open the file for appending. */ | |
190 | f = fopen(filename, "a"); | |
191 | if (!f) | |
192 | return 0; | |
193 | ||
194 | fprintf(f, "%s ", host); | |
195 | if (key_write(key, f)) { | |
196 | fprintf(f, "\n"); | |
197 | success = 1; | |
198 | } else { | |
199 | error("add_host_to_hostfile: saving key failed"); | |
200 | } | |
201 | ||
202 | /* Close the file. */ | |
203 | fclose(f); | |
204 | return success; | |
205 | } |