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Damien Millera31c9292005-05-26 12:03:31 +10001/* $OpenBSD: dns.c,v 1.11 2005/04/20 10:05:45 jakob Exp $ */
Damien Miller37876e92003-05-15 10:19:46 +10002
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
29#include "includes.h"
30
Damien Miller37876e92003-05-15 10:19:46 +100031#include <openssl/bn.h>
32#ifdef LWRES
33#include <lwres/netdb.h>
34#include <dns/result.h>
35#else /* LWRES */
36#include <netdb.h>
37#endif /* LWRES */
38
39#include "xmalloc.h"
40#include "key.h"
41#include "dns.h"
42#include "log.h"
43#include "uuencode.h"
44
45extern char *__progname;
Damien Millera31c9292005-05-26 12:03:31 +100046RCSID("$OpenBSD: dns.c,v 1.11 2005/04/20 10:05:45 jakob Exp $");
Damien Miller37876e92003-05-15 10:19:46 +100047
48#ifndef LWRES
49static const char *errset_text[] = {
50 "success", /* 0 ERRSET_SUCCESS */
51 "out of memory", /* 1 ERRSET_NOMEMORY */
52 "general failure", /* 2 ERRSET_FAIL */
53 "invalid parameter", /* 3 ERRSET_INVAL */
54 "name does not exist", /* 4 ERRSET_NONAME */
55 "data does not exist", /* 5 ERRSET_NODATA */
56};
57
58static const char *
Darren Tucker3f9fdc72004-06-22 12:56:01 +100059dns_result_totext(unsigned int res)
Damien Miller37876e92003-05-15 10:19:46 +100060{
Darren Tucker3f9fdc72004-06-22 12:56:01 +100061 switch (res) {
Damien Miller37876e92003-05-15 10:19:46 +100062 case ERRSET_SUCCESS:
63 return errset_text[ERRSET_SUCCESS];
64 case ERRSET_NOMEMORY:
65 return errset_text[ERRSET_NOMEMORY];
66 case ERRSET_FAIL:
67 return errset_text[ERRSET_FAIL];
68 case ERRSET_INVAL:
69 return errset_text[ERRSET_INVAL];
70 case ERRSET_NONAME:
71 return errset_text[ERRSET_NONAME];
72 case ERRSET_NODATA:
73 return errset_text[ERRSET_NODATA];
74 default:
75 return "unknown error";
76 }
77}
78#endif /* LWRES */
79
80
81/*
82 * Read SSHFP parameters from key buffer.
83 */
84static int
85dns_read_key(u_int8_t *algorithm, u_int8_t *digest_type,
Damien Miller150b5572003-11-17 21:19:29 +110086 u_char **digest, u_int *digest_len, const Key *key)
Damien Miller37876e92003-05-15 10:19:46 +100087{
88 int success = 0;
89
90 switch (key->type) {
91 case KEY_RSA:
92 *algorithm = SSHFP_KEY_RSA;
93 break;
94 case KEY_DSA:
95 *algorithm = SSHFP_KEY_DSA;
96 break;
97 default:
98 *algorithm = SSHFP_KEY_RESERVED;
99 }
100
101 if (*algorithm) {
102 *digest_type = SSHFP_HASH_SHA1;
103 *digest = key_fingerprint_raw(key, SSH_FP_SHA1, digest_len);
104 success = 1;
105 } else {
106 *digest_type = SSHFP_HASH_RESERVED;
107 *digest = NULL;
108 *digest_len = 0;
109 success = 0;
110 }
111
112 return success;
113}
114
115/*
116 * Read SSHFP parameters from rdata buffer.
117 */
118static int
119dns_read_rdata(u_int8_t *algorithm, u_int8_t *digest_type,
120 u_char **digest, u_int *digest_len, u_char *rdata, int rdata_len)
121{
122 int success = 0;
123
124 *algorithm = SSHFP_KEY_RESERVED;
125 *digest_type = SSHFP_HASH_RESERVED;
126
127 if (rdata_len >= 2) {
128 *algorithm = rdata[0];
129 *digest_type = rdata[1];
130 *digest_len = rdata_len - 2;
131
132 if (*digest_len > 0) {
133 *digest = (u_char *) xmalloc(*digest_len);
134 memcpy(*digest, rdata + 2, *digest_len);
135 } else {
136 *digest = NULL;
137 }
138
139 success = 1;
140 }
141
142 return success;
143}
144
Damien Millera31c9292005-05-26 12:03:31 +1000145/*
146 * Check if hostname is numerical.
147 * Returns -1 if hostname is numeric, 0 otherwise
148 */
149static int
150is_numeric_hostname(const char *hostname)
151{
152 struct addrinfo hints, *ai;
153
154 memset(&hints, 0, sizeof(hints));
155 hints.ai_socktype = SOCK_DGRAM;
156 hints.ai_flags = AI_NUMERICHOST;
157
158 if (getaddrinfo(hostname, "0", &hints, &ai) == 0) {
159 freeaddrinfo(ai);
160 return -1;
161 }
162
163 return 0;
164}
Damien Miller37876e92003-05-15 10:19:46 +1000165
166/*
167 * Verify the given hostname, address and host key using DNS.
Damien Millera8e06ce2003-11-21 23:48:55 +1100168 * Returns 0 if lookup succeeds, -1 otherwise
Damien Miller37876e92003-05-15 10:19:46 +1000169 */
170int
171verify_host_key_dns(const char *hostname, struct sockaddr *address,
Damien Miller150b5572003-11-17 21:19:29 +1100172 const Key *hostkey, int *flags)
Damien Miller37876e92003-05-15 10:19:46 +1000173{
174 int counter;
175 int result;
176 struct rrsetinfo *fingerprints = NULL;
Damien Miller37876e92003-05-15 10:19:46 +1000177
178 u_int8_t hostkey_algorithm;
179 u_int8_t hostkey_digest_type;
180 u_char *hostkey_digest;
181 u_int hostkey_digest_len;
182
183 u_int8_t dnskey_algorithm;
184 u_int8_t dnskey_digest_type;
185 u_char *dnskey_digest;
186 u_int dnskey_digest_len;
187
Damien Miller150b5572003-11-17 21:19:29 +1100188 *flags = 0;
Damien Miller37876e92003-05-15 10:19:46 +1000189
190 debug3("verify_hostkey_dns");
191 if (hostkey == NULL)
192 fatal("No key to look up!");
193
Damien Millera31c9292005-05-26 12:03:31 +1000194 if (is_numeric_hostname(hostname)) {
195 debug("skipped DNS lookup for numerical hostname");
196 return -1;
197 }
198
Damien Miller37876e92003-05-15 10:19:46 +1000199 result = getrrsetbyname(hostname, DNS_RDATACLASS_IN,
200 DNS_RDATATYPE_SSHFP, 0, &fingerprints);
201 if (result) {
202 verbose("DNS lookup error: %s", dns_result_totext(result));
Damien Miller150b5572003-11-17 21:19:29 +1100203 return -1;
Damien Miller37876e92003-05-15 10:19:46 +1000204 }
205
Damien Miller150b5572003-11-17 21:19:29 +1100206 if (fingerprints->rri_flags & RRSET_VALIDATED) {
207 *flags |= DNS_VERIFY_SECURE;
208 debug("found %d secure fingerprints in DNS",
209 fingerprints->rri_nrdatas);
210 } else {
211 debug("found %d insecure fingerprints in DNS",
212 fingerprints->rri_nrdatas);
Damien Miller37876e92003-05-15 10:19:46 +1000213 }
Damien Miller37876e92003-05-15 10:19:46 +1000214
215 /* Initialize host key parameters */
216 if (!dns_read_key(&hostkey_algorithm, &hostkey_digest_type,
217 &hostkey_digest, &hostkey_digest_len, hostkey)) {
218 error("Error calculating host key fingerprint.");
Damien Millerb0622652003-05-15 13:27:28 +1000219 freerrset(fingerprints);
Damien Miller150b5572003-11-17 21:19:29 +1100220 return -1;
Damien Miller37876e92003-05-15 10:19:46 +1000221 }
222
Damien Miller150b5572003-11-17 21:19:29 +1100223 if (fingerprints->rri_nrdatas)
224 *flags |= DNS_VERIFY_FOUND;
225
Damien Miller37876e92003-05-15 10:19:46 +1000226 for (counter = 0 ; counter < fingerprints->rri_nrdatas ; counter++) {
227 /*
228 * Extract the key from the answer. Ignore any badly
229 * formatted fingerprints.
230 */
231 if (!dns_read_rdata(&dnskey_algorithm, &dnskey_digest_type,
232 &dnskey_digest, &dnskey_digest_len,
233 fingerprints->rri_rdatas[counter].rdi_data,
234 fingerprints->rri_rdatas[counter].rdi_length)) {
235 verbose("Error parsing fingerprint from DNS.");
236 continue;
237 }
238
239 /* Check if the current key is the same as the given key */
240 if (hostkey_algorithm == dnskey_algorithm &&
241 hostkey_digest_type == dnskey_digest_type) {
242
243 if (hostkey_digest_len == dnskey_digest_len &&
244 memcmp(hostkey_digest, dnskey_digest,
245 hostkey_digest_len) == 0) {
246
Damien Miller150b5572003-11-17 21:19:29 +1100247 *flags |= DNS_VERIFY_MATCH;
Damien Miller37876e92003-05-15 10:19:46 +1000248 }
249 }
250 }
251
252 freerrset(fingerprints);
253
Damien Miller150b5572003-11-17 21:19:29 +1100254 if (*flags & DNS_VERIFY_FOUND)
255 if (*flags & DNS_VERIFY_MATCH)
256 debug("matching host key fingerprint found in DNS");
257 else
258 debug("mismatching host key fingerprint found in DNS");
259 else
260 debug("no host key fingerprint found in DNS");
Damien Miller37876e92003-05-15 10:19:46 +1000261
Damien Miller150b5572003-11-17 21:19:29 +1100262 return 0;
Damien Miller37876e92003-05-15 10:19:46 +1000263}
264
265
266/*
267 * Export the fingerprint of a key as a DNS resource record
268 */
269int
Damien Miller150b5572003-11-17 21:19:29 +1100270export_dns_rr(const char *hostname, const Key *key, FILE *f, int generic)
Damien Miller37876e92003-05-15 10:19:46 +1000271{
272 u_int8_t rdata_pubkey_algorithm = 0;
273 u_int8_t rdata_digest_type = SSHFP_HASH_SHA1;
274 u_char *rdata_digest;
275 u_int rdata_digest_len;
276
277 int i;
278 int success = 0;
279
280 if (dns_read_key(&rdata_pubkey_algorithm, &rdata_digest_type,
281 &rdata_digest, &rdata_digest_len, key)) {
282
283 if (generic)
284 fprintf(f, "%s IN TYPE%d \\# %d %02x %02x ", hostname,
285 DNS_RDATATYPE_SSHFP, 2 + rdata_digest_len,
286 rdata_pubkey_algorithm, rdata_digest_type);
287 else
288 fprintf(f, "%s IN SSHFP %d %d ", hostname,
289 rdata_pubkey_algorithm, rdata_digest_type);
290
291 for (i = 0; i < rdata_digest_len; i++)
292 fprintf(f, "%02x", rdata_digest[i]);
293 fprintf(f, "\n");
294 success = 1;
295 } else {
296 error("dns_export_rr: unsupported algorithm");
297 }
298
299 return success;
300}