1 /* $OpenBSD: dns.c,v 1.13 2005/10/13 19:13:41 stevesk Exp $ */
4 * Copyright (c) 2003 Wesley Griffin. All rights reserved.
5 * Copyright (c) 2003 Jakob Schlyter. All rights reserved.
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
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.
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.
31 #include <openssl/bn.h>
33 #include <lwres/netdb.h>
34 #include <dns/result.h>
44 RCSID("$OpenBSD: dns.c,v 1.13 2005/10/13 19:13:41 stevesk Exp $");
47 static const char *errset_text[] = {
48 "success", /* 0 ERRSET_SUCCESS */
49 "out of memory", /* 1 ERRSET_NOMEMORY */
50 "general failure", /* 2 ERRSET_FAIL */
51 "invalid parameter", /* 3 ERRSET_INVAL */
52 "name does not exist", /* 4 ERRSET_NONAME */
53 "data does not exist", /* 5 ERRSET_NODATA */
57 dns_result_totext(unsigned int res)
61 return errset_text[ERRSET_SUCCESS];
63 return errset_text[ERRSET_NOMEMORY];
65 return errset_text[ERRSET_FAIL];
67 return errset_text[ERRSET_INVAL];
69 return errset_text[ERRSET_NONAME];
71 return errset_text[ERRSET_NODATA];
73 return "unknown error";
80 * Read SSHFP parameters from key buffer.
83 dns_read_key(u_int8_t *algorithm, u_int8_t *digest_type,
84 u_char **digest, u_int *digest_len, const Key *key)
90 *algorithm = SSHFP_KEY_RSA;
93 *algorithm = SSHFP_KEY_DSA;
96 *algorithm = SSHFP_KEY_RESERVED;
100 *digest_type = SSHFP_HASH_SHA1;
101 *digest = key_fingerprint_raw(key, SSH_FP_SHA1, digest_len);
104 *digest_type = SSHFP_HASH_RESERVED;
114 * Read SSHFP parameters from rdata buffer.
117 dns_read_rdata(u_int8_t *algorithm, u_int8_t *digest_type,
118 u_char **digest, u_int *digest_len, u_char *rdata, int rdata_len)
122 *algorithm = SSHFP_KEY_RESERVED;
123 *digest_type = SSHFP_HASH_RESERVED;
125 if (rdata_len >= 2) {
126 *algorithm = rdata[0];
127 *digest_type = rdata[1];
128 *digest_len = rdata_len - 2;
130 if (*digest_len > 0) {
131 *digest = (u_char *) xmalloc(*digest_len);
132 memcpy(*digest, rdata + 2, *digest_len);
144 * Check if hostname is numerical.
145 * Returns -1 if hostname is numeric, 0 otherwise
148 is_numeric_hostname(const char *hostname)
150 struct addrinfo hints, *ai;
152 memset(&hints, 0, sizeof(hints));
153 hints.ai_socktype = SOCK_DGRAM;
154 hints.ai_flags = AI_NUMERICHOST;
156 if (getaddrinfo(hostname, "0", &hints, &ai) == 0) {
165 * Verify the given hostname, address and host key using DNS.
166 * Returns 0 if lookup succeeds, -1 otherwise
169 verify_host_key_dns(const char *hostname, struct sockaddr *address,
170 const Key *hostkey, int *flags)
174 struct rrsetinfo *fingerprints = NULL;
176 u_int8_t hostkey_algorithm;
177 u_int8_t hostkey_digest_type;
178 u_char *hostkey_digest;
179 u_int hostkey_digest_len;
181 u_int8_t dnskey_algorithm;
182 u_int8_t dnskey_digest_type;
183 u_char *dnskey_digest;
184 u_int dnskey_digest_len;
188 debug3("verify_hostkey_dns");
190 fatal("No key to look up!");
192 if (is_numeric_hostname(hostname)) {
193 debug("skipped DNS lookup for numerical hostname");
197 result = getrrsetbyname(hostname, DNS_RDATACLASS_IN,
198 DNS_RDATATYPE_SSHFP, 0, &fingerprints);
200 verbose("DNS lookup error: %s", dns_result_totext(result));
204 if (fingerprints->rri_flags & RRSET_VALIDATED) {
205 *flags |= DNS_VERIFY_SECURE;
206 debug("found %d secure fingerprints in DNS",
207 fingerprints->rri_nrdatas);
209 debug("found %d insecure fingerprints in DNS",
210 fingerprints->rri_nrdatas);
213 /* Initialize host key parameters */
214 if (!dns_read_key(&hostkey_algorithm, &hostkey_digest_type,
215 &hostkey_digest, &hostkey_digest_len, hostkey)) {
216 error("Error calculating host key fingerprint.");
217 freerrset(fingerprints);
221 if (fingerprints->rri_nrdatas)
222 *flags |= DNS_VERIFY_FOUND;
224 for (counter = 0; counter < fingerprints->rri_nrdatas; counter++) {
226 * Extract the key from the answer. Ignore any badly
227 * formatted fingerprints.
229 if (!dns_read_rdata(&dnskey_algorithm, &dnskey_digest_type,
230 &dnskey_digest, &dnskey_digest_len,
231 fingerprints->rri_rdatas[counter].rdi_data,
232 fingerprints->rri_rdatas[counter].rdi_length)) {
233 verbose("Error parsing fingerprint from DNS.");
237 /* Check if the current key is the same as the given key */
238 if (hostkey_algorithm == dnskey_algorithm &&
239 hostkey_digest_type == dnskey_digest_type) {
241 if (hostkey_digest_len == dnskey_digest_len &&
242 memcmp(hostkey_digest, dnskey_digest,
243 hostkey_digest_len) == 0) {
245 *flags |= DNS_VERIFY_MATCH;
250 freerrset(fingerprints);
252 if (*flags & DNS_VERIFY_FOUND)
253 if (*flags & DNS_VERIFY_MATCH)
254 debug("matching host key fingerprint found in DNS");
256 debug("mismatching host key fingerprint found in DNS");
258 debug("no host key fingerprint found in DNS");
265 * Export the fingerprint of a key as a DNS resource record
268 export_dns_rr(const char *hostname, const Key *key, FILE *f, int generic)
270 u_int8_t rdata_pubkey_algorithm = 0;
271 u_int8_t rdata_digest_type = SSHFP_HASH_SHA1;
272 u_char *rdata_digest;
273 u_int rdata_digest_len;
278 if (dns_read_key(&rdata_pubkey_algorithm, &rdata_digest_type,
279 &rdata_digest, &rdata_digest_len, key)) {
282 fprintf(f, "%s IN TYPE%d \\# %d %02x %02x ", hostname,
283 DNS_RDATATYPE_SSHFP, 2 + rdata_digest_len,
284 rdata_pubkey_algorithm, rdata_digest_type);
286 fprintf(f, "%s IN SSHFP %d %d ", hostname,
287 rdata_pubkey_algorithm, rdata_digest_type);
289 for (i = 0; i < rdata_digest_len; i++)
290 fprintf(f, "%02x", rdata_digest[i]);
294 error("dns_export_rr: unsupported algorithm");