1 /* $OpenBSD: dns.c,v 1.20 2006/07/08 21:47:12 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.
30 #include <sys/types.h>
31 #include <sys/socket.h>
40 static const char *errset_text[] = {
41 "success", /* 0 ERRSET_SUCCESS */
42 "out of memory", /* 1 ERRSET_NOMEMORY */
43 "general failure", /* 2 ERRSET_FAIL */
44 "invalid parameter", /* 3 ERRSET_INVAL */
45 "name does not exist", /* 4 ERRSET_NONAME */
46 "data does not exist", /* 5 ERRSET_NODATA */
50 dns_result_totext(unsigned int res)
54 return errset_text[ERRSET_SUCCESS];
56 return errset_text[ERRSET_NOMEMORY];
58 return errset_text[ERRSET_FAIL];
60 return errset_text[ERRSET_INVAL];
62 return errset_text[ERRSET_NONAME];
64 return errset_text[ERRSET_NODATA];
66 return "unknown error";
71 * Read SSHFP parameters from key buffer.
74 dns_read_key(u_int8_t *algorithm, u_int8_t *digest_type,
75 u_char **digest, u_int *digest_len, const Key *key)
81 *algorithm = SSHFP_KEY_RSA;
84 *algorithm = SSHFP_KEY_DSA;
87 *algorithm = SSHFP_KEY_RESERVED; /* 0 */
91 *digest_type = SSHFP_HASH_SHA1;
92 *digest = key_fingerprint_raw(key, SSH_FP_SHA1, digest_len);
94 fatal("dns_read_key: null from key_fingerprint_raw()");
97 *digest_type = SSHFP_HASH_RESERVED;
107 * Read SSHFP parameters from rdata buffer.
110 dns_read_rdata(u_int8_t *algorithm, u_int8_t *digest_type,
111 u_char **digest, u_int *digest_len, u_char *rdata, int rdata_len)
115 *algorithm = SSHFP_KEY_RESERVED;
116 *digest_type = SSHFP_HASH_RESERVED;
118 if (rdata_len >= 2) {
119 *algorithm = rdata[0];
120 *digest_type = rdata[1];
121 *digest_len = rdata_len - 2;
123 if (*digest_len > 0) {
124 *digest = (u_char *) xmalloc(*digest_len);
125 memcpy(*digest, rdata + 2, *digest_len);
127 *digest = (u_char *)xstrdup("");
137 * Check if hostname is numerical.
138 * Returns -1 if hostname is numeric, 0 otherwise
141 is_numeric_hostname(const char *hostname)
143 struct addrinfo hints, *ai;
145 memset(&hints, 0, sizeof(hints));
146 hints.ai_socktype = SOCK_DGRAM;
147 hints.ai_flags = AI_NUMERICHOST;
149 if (getaddrinfo(hostname, "0", &hints, &ai) == 0) {
158 * Verify the given hostname, address and host key using DNS.
159 * Returns 0 if lookup succeeds, -1 otherwise
162 verify_host_key_dns(const char *hostname, struct sockaddr *address,
163 const Key *hostkey, int *flags)
167 struct rrsetinfo *fingerprints = NULL;
169 u_int8_t hostkey_algorithm;
170 u_int8_t hostkey_digest_type;
171 u_char *hostkey_digest;
172 u_int hostkey_digest_len;
174 u_int8_t dnskey_algorithm;
175 u_int8_t dnskey_digest_type;
176 u_char *dnskey_digest;
177 u_int dnskey_digest_len;
181 debug3("verify_host_key_dns");
183 fatal("No key to look up!");
185 if (is_numeric_hostname(hostname)) {
186 debug("skipped DNS lookup for numerical hostname");
190 result = getrrsetbyname(hostname, DNS_RDATACLASS_IN,
191 DNS_RDATATYPE_SSHFP, 0, &fingerprints);
193 verbose("DNS lookup error: %s", dns_result_totext(result));
197 if (fingerprints->rri_flags & RRSET_VALIDATED) {
198 *flags |= DNS_VERIFY_SECURE;
199 debug("found %d secure fingerprints in DNS",
200 fingerprints->rri_nrdatas);
202 debug("found %d insecure fingerprints in DNS",
203 fingerprints->rri_nrdatas);
206 /* Initialize host key parameters */
207 if (!dns_read_key(&hostkey_algorithm, &hostkey_digest_type,
208 &hostkey_digest, &hostkey_digest_len, hostkey)) {
209 error("Error calculating host key fingerprint.");
210 freerrset(fingerprints);
214 if (fingerprints->rri_nrdatas)
215 *flags |= DNS_VERIFY_FOUND;
217 for (counter = 0; counter < fingerprints->rri_nrdatas; counter++) {
219 * Extract the key from the answer. Ignore any badly
220 * formatted fingerprints.
222 if (!dns_read_rdata(&dnskey_algorithm, &dnskey_digest_type,
223 &dnskey_digest, &dnskey_digest_len,
224 fingerprints->rri_rdatas[counter].rdi_data,
225 fingerprints->rri_rdatas[counter].rdi_length)) {
226 verbose("Error parsing fingerprint from DNS.");
230 /* Check if the current key is the same as the given key */
231 if (hostkey_algorithm == dnskey_algorithm &&
232 hostkey_digest_type == dnskey_digest_type) {
234 if (hostkey_digest_len == dnskey_digest_len &&
235 memcmp(hostkey_digest, dnskey_digest,
236 hostkey_digest_len) == 0) {
238 *flags |= DNS_VERIFY_MATCH;
241 xfree(dnskey_digest);
244 xfree(hostkey_digest); /* from key_fingerprint_raw() */
245 freerrset(fingerprints);
247 if (*flags & DNS_VERIFY_FOUND)
248 if (*flags & DNS_VERIFY_MATCH)
249 debug("matching host key fingerprint found in DNS");
251 debug("mismatching host key fingerprint found in DNS");
253 debug("no host key fingerprint found in DNS");
259 * Export the fingerprint of a key as a DNS resource record
262 export_dns_rr(const char *hostname, const Key *key, FILE *f, int generic)
264 u_int8_t rdata_pubkey_algorithm = 0;
265 u_int8_t rdata_digest_type = SSHFP_HASH_SHA1;
266 u_char *rdata_digest;
267 u_int rdata_digest_len;
272 if (dns_read_key(&rdata_pubkey_algorithm, &rdata_digest_type,
273 &rdata_digest, &rdata_digest_len, key)) {
276 fprintf(f, "%s IN TYPE%d \\# %d %02x %02x ", hostname,
277 DNS_RDATATYPE_SSHFP, 2 + rdata_digest_len,
278 rdata_pubkey_algorithm, rdata_digest_type);
280 fprintf(f, "%s IN SSHFP %d %d ", hostname,
281 rdata_pubkey_algorithm, rdata_digest_type);
283 for (i = 0; i < rdata_digest_len; i++)
284 fprintf(f, "%02x", rdata_digest[i]);
286 xfree(rdata_digest); /* from key_fingerprint_raw() */
289 error("export_dns_rr: unsupported algorithm");