]>
Commit | Line | Data |
---|---|---|
1 | /* $OpenBSD: dns.c,v 1.20 2006/07/08 21:47:12 stevesk Exp $ */ | |
2 | ||
3 | /* | |
4 | * Copyright (c) 2003 Wesley Griffin. All rights reserved. | |
5 | * Copyright (c) 2003 Jakob Schlyter. All rights reserved. | |
6 | * | |
7 | * Redistribution and use in source and binary forms, with or without | |
8 | * modification, are permitted provided that the following conditions | |
9 | * are met: | |
10 | * 1. Redistributions of source code must retain the above copyright | |
11 | * notice, this list of conditions and the following disclaimer. | |
12 | * 2. Redistributions in binary form must reproduce the above copyright | |
13 | * notice, this list of conditions and the following disclaimer in the | |
14 | * documentation and/or other materials provided with the distribution. | |
15 | * | |
16 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR | |
17 | * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES | |
18 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. | |
19 | * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, | |
20 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT | |
21 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | |
22 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY | |
23 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | |
24 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF | |
25 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
26 | */ | |
27 | ||
28 | #include "includes.h" | |
29 | ||
30 | #include <sys/types.h> | |
31 | #include <sys/socket.h> | |
32 | ||
33 | #if defined(HAVE_NETDB_H) | |
34 | # include <netdb.h> | |
35 | #endif | |
36 | ||
37 | #include "xmalloc.h" | |
38 | #include "key.h" | |
39 | #include "dns.h" | |
40 | #include "log.h" | |
41 | ||
42 | static const char *errset_text[] = { | |
43 | "success", /* 0 ERRSET_SUCCESS */ | |
44 | "out of memory", /* 1 ERRSET_NOMEMORY */ | |
45 | "general failure", /* 2 ERRSET_FAIL */ | |
46 | "invalid parameter", /* 3 ERRSET_INVAL */ | |
47 | "name does not exist", /* 4 ERRSET_NONAME */ | |
48 | "data does not exist", /* 5 ERRSET_NODATA */ | |
49 | }; | |
50 | ||
51 | static const char * | |
52 | dns_result_totext(unsigned int res) | |
53 | { | |
54 | switch (res) { | |
55 | case ERRSET_SUCCESS: | |
56 | return errset_text[ERRSET_SUCCESS]; | |
57 | case ERRSET_NOMEMORY: | |
58 | return errset_text[ERRSET_NOMEMORY]; | |
59 | case ERRSET_FAIL: | |
60 | return errset_text[ERRSET_FAIL]; | |
61 | case ERRSET_INVAL: | |
62 | return errset_text[ERRSET_INVAL]; | |
63 | case ERRSET_NONAME: | |
64 | return errset_text[ERRSET_NONAME]; | |
65 | case ERRSET_NODATA: | |
66 | return errset_text[ERRSET_NODATA]; | |
67 | default: | |
68 | return "unknown error"; | |
69 | } | |
70 | } | |
71 | ||
72 | /* | |
73 | * Read SSHFP parameters from key buffer. | |
74 | */ | |
75 | static int | |
76 | dns_read_key(u_int8_t *algorithm, u_int8_t *digest_type, | |
77 | u_char **digest, u_int *digest_len, const Key *key) | |
78 | { | |
79 | int success = 0; | |
80 | ||
81 | switch (key->type) { | |
82 | case KEY_RSA: | |
83 | *algorithm = SSHFP_KEY_RSA; | |
84 | break; | |
85 | case KEY_DSA: | |
86 | *algorithm = SSHFP_KEY_DSA; | |
87 | break; | |
88 | default: | |
89 | *algorithm = SSHFP_KEY_RESERVED; /* 0 */ | |
90 | } | |
91 | ||
92 | if (*algorithm) { | |
93 | *digest_type = SSHFP_HASH_SHA1; | |
94 | *digest = key_fingerprint_raw(key, SSH_FP_SHA1, digest_len); | |
95 | if (*digest == NULL) | |
96 | fatal("dns_read_key: null from key_fingerprint_raw()"); | |
97 | success = 1; | |
98 | } else { | |
99 | *digest_type = SSHFP_HASH_RESERVED; | |
100 | *digest = NULL; | |
101 | *digest_len = 0; | |
102 | success = 0; | |
103 | } | |
104 | ||
105 | return success; | |
106 | } | |
107 | ||
108 | /* | |
109 | * Read SSHFP parameters from rdata buffer. | |
110 | */ | |
111 | static int | |
112 | dns_read_rdata(u_int8_t *algorithm, u_int8_t *digest_type, | |
113 | u_char **digest, u_int *digest_len, u_char *rdata, int rdata_len) | |
114 | { | |
115 | int success = 0; | |
116 | ||
117 | *algorithm = SSHFP_KEY_RESERVED; | |
118 | *digest_type = SSHFP_HASH_RESERVED; | |
119 | ||
120 | if (rdata_len >= 2) { | |
121 | *algorithm = rdata[0]; | |
122 | *digest_type = rdata[1]; | |
123 | *digest_len = rdata_len - 2; | |
124 | ||
125 | if (*digest_len > 0) { | |
126 | *digest = (u_char *) xmalloc(*digest_len); | |
127 | memcpy(*digest, rdata + 2, *digest_len); | |
128 | } else { | |
129 | *digest = (u_char *)xstrdup(""); | |
130 | } | |
131 | ||
132 | success = 1; | |
133 | } | |
134 | ||
135 | return success; | |
136 | } | |
137 | ||
138 | /* | |
139 | * Check if hostname is numerical. | |
140 | * Returns -1 if hostname is numeric, 0 otherwise | |
141 | */ | |
142 | static int | |
143 | is_numeric_hostname(const char *hostname) | |
144 | { | |
145 | struct addrinfo hints, *ai; | |
146 | ||
147 | memset(&hints, 0, sizeof(hints)); | |
148 | hints.ai_socktype = SOCK_DGRAM; | |
149 | hints.ai_flags = AI_NUMERICHOST; | |
150 | ||
151 | if (getaddrinfo(hostname, "0", &hints, &ai) == 0) { | |
152 | freeaddrinfo(ai); | |
153 | return -1; | |
154 | } | |
155 | ||
156 | return 0; | |
157 | } | |
158 | ||
159 | /* | |
160 | * Verify the given hostname, address and host key using DNS. | |
161 | * Returns 0 if lookup succeeds, -1 otherwise | |
162 | */ | |
163 | int | |
164 | verify_host_key_dns(const char *hostname, struct sockaddr *address, | |
165 | const Key *hostkey, int *flags) | |
166 | { | |
167 | u_int counter; | |
168 | int result; | |
169 | struct rrsetinfo *fingerprints = NULL; | |
170 | ||
171 | u_int8_t hostkey_algorithm; | |
172 | u_int8_t hostkey_digest_type; | |
173 | u_char *hostkey_digest; | |
174 | u_int hostkey_digest_len; | |
175 | ||
176 | u_int8_t dnskey_algorithm; | |
177 | u_int8_t dnskey_digest_type; | |
178 | u_char *dnskey_digest; | |
179 | u_int dnskey_digest_len; | |
180 | ||
181 | *flags = 0; | |
182 | ||
183 | debug3("verify_host_key_dns"); | |
184 | if (hostkey == NULL) | |
185 | fatal("No key to look up!"); | |
186 | ||
187 | if (is_numeric_hostname(hostname)) { | |
188 | debug("skipped DNS lookup for numerical hostname"); | |
189 | return -1; | |
190 | } | |
191 | ||
192 | result = getrrsetbyname(hostname, DNS_RDATACLASS_IN, | |
193 | DNS_RDATATYPE_SSHFP, 0, &fingerprints); | |
194 | if (result) { | |
195 | verbose("DNS lookup error: %s", dns_result_totext(result)); | |
196 | return -1; | |
197 | } | |
198 | ||
199 | if (fingerprints->rri_flags & RRSET_VALIDATED) { | |
200 | *flags |= DNS_VERIFY_SECURE; | |
201 | debug("found %d secure fingerprints in DNS", | |
202 | fingerprints->rri_nrdatas); | |
203 | } else { | |
204 | debug("found %d insecure fingerprints in DNS", | |
205 | fingerprints->rri_nrdatas); | |
206 | } | |
207 | ||
208 | /* Initialize host key parameters */ | |
209 | if (!dns_read_key(&hostkey_algorithm, &hostkey_digest_type, | |
210 | &hostkey_digest, &hostkey_digest_len, hostkey)) { | |
211 | error("Error calculating host key fingerprint."); | |
212 | freerrset(fingerprints); | |
213 | return -1; | |
214 | } | |
215 | ||
216 | if (fingerprints->rri_nrdatas) | |
217 | *flags |= DNS_VERIFY_FOUND; | |
218 | ||
219 | for (counter = 0; counter < fingerprints->rri_nrdatas; counter++) { | |
220 | /* | |
221 | * Extract the key from the answer. Ignore any badly | |
222 | * formatted fingerprints. | |
223 | */ | |
224 | if (!dns_read_rdata(&dnskey_algorithm, &dnskey_digest_type, | |
225 | &dnskey_digest, &dnskey_digest_len, | |
226 | fingerprints->rri_rdatas[counter].rdi_data, | |
227 | fingerprints->rri_rdatas[counter].rdi_length)) { | |
228 | verbose("Error parsing fingerprint from DNS."); | |
229 | continue; | |
230 | } | |
231 | ||
232 | /* Check if the current key is the same as the given key */ | |
233 | if (hostkey_algorithm == dnskey_algorithm && | |
234 | hostkey_digest_type == dnskey_digest_type) { | |
235 | ||
236 | if (hostkey_digest_len == dnskey_digest_len && | |
237 | memcmp(hostkey_digest, dnskey_digest, | |
238 | hostkey_digest_len) == 0) { | |
239 | ||
240 | *flags |= DNS_VERIFY_MATCH; | |
241 | } | |
242 | } | |
243 | xfree(dnskey_digest); | |
244 | } | |
245 | ||
246 | xfree(hostkey_digest); /* from key_fingerprint_raw() */ | |
247 | freerrset(fingerprints); | |
248 | ||
249 | if (*flags & DNS_VERIFY_FOUND) | |
250 | if (*flags & DNS_VERIFY_MATCH) | |
251 | debug("matching host key fingerprint found in DNS"); | |
252 | else | |
253 | debug("mismatching host key fingerprint found in DNS"); | |
254 | else | |
255 | debug("no host key fingerprint found in DNS"); | |
256 | ||
257 | return 0; | |
258 | } | |
259 | ||
260 | /* | |
261 | * Export the fingerprint of a key as a DNS resource record | |
262 | */ | |
263 | int | |
264 | export_dns_rr(const char *hostname, const Key *key, FILE *f, int generic) | |
265 | { | |
266 | u_int8_t rdata_pubkey_algorithm = 0; | |
267 | u_int8_t rdata_digest_type = SSHFP_HASH_SHA1; | |
268 | u_char *rdata_digest; | |
269 | u_int rdata_digest_len; | |
270 | ||
271 | u_int i; | |
272 | int success = 0; | |
273 | ||
274 | if (dns_read_key(&rdata_pubkey_algorithm, &rdata_digest_type, | |
275 | &rdata_digest, &rdata_digest_len, key)) { | |
276 | ||
277 | if (generic) | |
278 | fprintf(f, "%s IN TYPE%d \\# %d %02x %02x ", hostname, | |
279 | DNS_RDATATYPE_SSHFP, 2 + rdata_digest_len, | |
280 | rdata_pubkey_algorithm, rdata_digest_type); | |
281 | else | |
282 | fprintf(f, "%s IN SSHFP %d %d ", hostname, | |
283 | rdata_pubkey_algorithm, rdata_digest_type); | |
284 | ||
285 | for (i = 0; i < rdata_digest_len; i++) | |
286 | fprintf(f, "%02x", rdata_digest[i]); | |
287 | fprintf(f, "\n"); | |
288 | xfree(rdata_digest); /* from key_fingerprint_raw() */ | |
289 | success = 1; | |
290 | } else { | |
291 | error("export_dns_rr: unsupported algorithm"); | |
292 | } | |
293 | ||
294 | return success; | |
295 | } |