1 /* $OpenBSD: dns.c,v 1.19 2006/03/25 22:22:43 djm 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.
37 static const char *errset_text[] = {
38 "success", /* 0 ERRSET_SUCCESS */
39 "out of memory", /* 1 ERRSET_NOMEMORY */
40 "general failure", /* 2 ERRSET_FAIL */
41 "invalid parameter", /* 3 ERRSET_INVAL */
42 "name does not exist", /* 4 ERRSET_NONAME */
43 "data does not exist", /* 5 ERRSET_NODATA */
47 dns_result_totext(unsigned int res)
51 return errset_text[ERRSET_SUCCESS];
53 return errset_text[ERRSET_NOMEMORY];
55 return errset_text[ERRSET_FAIL];
57 return errset_text[ERRSET_INVAL];
59 return errset_text[ERRSET_NONAME];
61 return errset_text[ERRSET_NODATA];
63 return "unknown error";
68 * Read SSHFP parameters from key buffer.
71 dns_read_key(u_int8_t *algorithm, u_int8_t *digest_type,
72 u_char **digest, u_int *digest_len, const Key *key)
78 *algorithm = SSHFP_KEY_RSA;
81 *algorithm = SSHFP_KEY_DSA;
84 *algorithm = SSHFP_KEY_RESERVED; /* 0 */
88 *digest_type = SSHFP_HASH_SHA1;
89 *digest = key_fingerprint_raw(key, SSH_FP_SHA1, digest_len);
91 fatal("dns_read_key: null from key_fingerprint_raw()");
94 *digest_type = SSHFP_HASH_RESERVED;
104 * Read SSHFP parameters from rdata buffer.
107 dns_read_rdata(u_int8_t *algorithm, u_int8_t *digest_type,
108 u_char **digest, u_int *digest_len, u_char *rdata, int rdata_len)
112 *algorithm = SSHFP_KEY_RESERVED;
113 *digest_type = SSHFP_HASH_RESERVED;
115 if (rdata_len >= 2) {
116 *algorithm = rdata[0];
117 *digest_type = rdata[1];
118 *digest_len = rdata_len - 2;
120 if (*digest_len > 0) {
121 *digest = (u_char *) xmalloc(*digest_len);
122 memcpy(*digest, rdata + 2, *digest_len);
124 *digest = (u_char *)xstrdup("");
134 * Check if hostname is numerical.
135 * Returns -1 if hostname is numeric, 0 otherwise
138 is_numeric_hostname(const char *hostname)
140 struct addrinfo hints, *ai;
142 memset(&hints, 0, sizeof(hints));
143 hints.ai_socktype = SOCK_DGRAM;
144 hints.ai_flags = AI_NUMERICHOST;
146 if (getaddrinfo(hostname, "0", &hints, &ai) == 0) {
155 * Verify the given hostname, address and host key using DNS.
156 * Returns 0 if lookup succeeds, -1 otherwise
159 verify_host_key_dns(const char *hostname, struct sockaddr *address,
160 const Key *hostkey, int *flags)
164 struct rrsetinfo *fingerprints = NULL;
166 u_int8_t hostkey_algorithm;
167 u_int8_t hostkey_digest_type;
168 u_char *hostkey_digest;
169 u_int hostkey_digest_len;
171 u_int8_t dnskey_algorithm;
172 u_int8_t dnskey_digest_type;
173 u_char *dnskey_digest;
174 u_int dnskey_digest_len;
178 debug3("verify_host_key_dns");
180 fatal("No key to look up!");
182 if (is_numeric_hostname(hostname)) {
183 debug("skipped DNS lookup for numerical hostname");
187 result = getrrsetbyname(hostname, DNS_RDATACLASS_IN,
188 DNS_RDATATYPE_SSHFP, 0, &fingerprints);
190 verbose("DNS lookup error: %s", dns_result_totext(result));
194 if (fingerprints->rri_flags & RRSET_VALIDATED) {
195 *flags |= DNS_VERIFY_SECURE;
196 debug("found %d secure fingerprints in DNS",
197 fingerprints->rri_nrdatas);
199 debug("found %d insecure fingerprints in DNS",
200 fingerprints->rri_nrdatas);
203 /* Initialize host key parameters */
204 if (!dns_read_key(&hostkey_algorithm, &hostkey_digest_type,
205 &hostkey_digest, &hostkey_digest_len, hostkey)) {
206 error("Error calculating host key fingerprint.");
207 freerrset(fingerprints);
211 if (fingerprints->rri_nrdatas)
212 *flags |= DNS_VERIFY_FOUND;
214 for (counter = 0; counter < fingerprints->rri_nrdatas; counter++) {
216 * Extract the key from the answer. Ignore any badly
217 * formatted fingerprints.
219 if (!dns_read_rdata(&dnskey_algorithm, &dnskey_digest_type,
220 &dnskey_digest, &dnskey_digest_len,
221 fingerprints->rri_rdatas[counter].rdi_data,
222 fingerprints->rri_rdatas[counter].rdi_length)) {
223 verbose("Error parsing fingerprint from DNS.");
227 /* Check if the current key is the same as the given key */
228 if (hostkey_algorithm == dnskey_algorithm &&
229 hostkey_digest_type == dnskey_digest_type) {
231 if (hostkey_digest_len == dnskey_digest_len &&
232 memcmp(hostkey_digest, dnskey_digest,
233 hostkey_digest_len) == 0) {
235 *flags |= DNS_VERIFY_MATCH;
238 xfree(dnskey_digest);
241 xfree(hostkey_digest); /* from key_fingerprint_raw() */
242 freerrset(fingerprints);
244 if (*flags & DNS_VERIFY_FOUND)
245 if (*flags & DNS_VERIFY_MATCH)
246 debug("matching host key fingerprint found in DNS");
248 debug("mismatching host key fingerprint found in DNS");
250 debug("no host key fingerprint found in DNS");
256 * Export the fingerprint of a key as a DNS resource record
259 export_dns_rr(const char *hostname, const Key *key, FILE *f, int generic)
261 u_int8_t rdata_pubkey_algorithm = 0;
262 u_int8_t rdata_digest_type = SSHFP_HASH_SHA1;
263 u_char *rdata_digest;
264 u_int rdata_digest_len;
269 if (dns_read_key(&rdata_pubkey_algorithm, &rdata_digest_type,
270 &rdata_digest, &rdata_digest_len, key)) {
273 fprintf(f, "%s IN TYPE%d \\# %d %02x %02x ", hostname,
274 DNS_RDATATYPE_SSHFP, 2 + rdata_digest_len,
275 rdata_pubkey_algorithm, rdata_digest_type);
277 fprintf(f, "%s IN SSHFP %d %d ", hostname,
278 rdata_pubkey_algorithm, rdata_digest_type);
280 for (i = 0; i < rdata_digest_len; i++)
281 fprintf(f, "%02x", rdata_digest[i]);
283 xfree(rdata_digest); /* from key_fingerprint_raw() */
286 error("export_dns_rr: unsupported algorithm");