1 /* $OpenBSD: dns.c,v 1.28 2012/05/23 03:28:28 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.
30 #include <sys/types.h>
31 #include <sys/socket.h>
43 static const char *errset_text[] = {
44 "success", /* 0 ERRSET_SUCCESS */
45 "out of memory", /* 1 ERRSET_NOMEMORY */
46 "general failure", /* 2 ERRSET_FAIL */
47 "invalid parameter", /* 3 ERRSET_INVAL */
48 "name does not exist", /* 4 ERRSET_NONAME */
49 "data does not exist", /* 5 ERRSET_NODATA */
53 dns_result_totext(unsigned int res)
57 return errset_text[ERRSET_SUCCESS];
59 return errset_text[ERRSET_NOMEMORY];
61 return errset_text[ERRSET_FAIL];
63 return errset_text[ERRSET_INVAL];
65 return errset_text[ERRSET_NONAME];
67 return errset_text[ERRSET_NODATA];
69 return "unknown error";
74 * Read SSHFP parameters from key buffer.
77 dns_read_key(u_int8_t *algorithm, u_int8_t *digest_type,
78 u_char **digest, u_int *digest_len, Key *key)
81 enum fp_type fp_type = 0;
85 *algorithm = SSHFP_KEY_RSA;
87 *digest_type = SSHFP_HASH_SHA1;
90 *algorithm = SSHFP_KEY_DSA;
92 *digest_type = SSHFP_HASH_SHA1;
95 *algorithm = SSHFP_KEY_ECDSA;
97 *digest_type = SSHFP_HASH_SHA256;
100 *algorithm = SSHFP_KEY_RESERVED; /* 0 */
101 *digest_type = SSHFP_HASH_RESERVED; /* 0 */
104 switch (*digest_type) {
105 case SSHFP_HASH_SHA1:
106 fp_type = SSH_FP_SHA1;
108 case SSHFP_HASH_SHA256:
109 fp_type = SSH_FP_SHA256;
112 *digest_type = SSHFP_HASH_RESERVED; /* 0 */
115 if (*algorithm && *digest_type) {
116 *digest = key_fingerprint_raw(key, fp_type, digest_len);
118 fatal("dns_read_key: null from key_fingerprint_raw()");
130 * Read SSHFP parameters from rdata buffer.
133 dns_read_rdata(u_int8_t *algorithm, u_int8_t *digest_type,
134 u_char **digest, u_int *digest_len, u_char *rdata, int rdata_len)
138 *algorithm = SSHFP_KEY_RESERVED;
139 *digest_type = SSHFP_HASH_RESERVED;
141 if (rdata_len >= 2) {
142 *algorithm = rdata[0];
143 *digest_type = rdata[1];
144 *digest_len = rdata_len - 2;
146 if (*digest_len > 0) {
147 *digest = (u_char *) xmalloc(*digest_len);
148 memcpy(*digest, rdata + 2, *digest_len);
150 *digest = (u_char *)xstrdup("");
160 * Check if hostname is numerical.
161 * Returns -1 if hostname is numeric, 0 otherwise
164 is_numeric_hostname(const char *hostname)
166 struct addrinfo hints, *ai;
169 * We shouldn't ever get a null host but if we do then log an error
170 * and return -1 which stops DNS key fingerprint processing.
172 if (hostname == NULL) {
173 error("is_numeric_hostname called with NULL hostname");
177 memset(&hints, 0, sizeof(hints));
178 hints.ai_socktype = SOCK_DGRAM;
179 hints.ai_flags = AI_NUMERICHOST;
181 if (getaddrinfo(hostname, NULL, &hints, &ai) == 0) {
190 * Verify the given hostname, address and host key using DNS.
191 * Returns 0 if lookup succeeds, -1 otherwise
194 verify_host_key_dns(const char *hostname, struct sockaddr *address,
195 Key *hostkey, int *flags)
199 struct rrsetinfo *fingerprints = NULL;
201 u_int8_t hostkey_algorithm;
202 u_int8_t hostkey_digest_type = SSHFP_HASH_RESERVED;
203 u_char *hostkey_digest;
204 u_int hostkey_digest_len;
206 u_int8_t dnskey_algorithm;
207 u_int8_t dnskey_digest_type;
208 u_char *dnskey_digest;
209 u_int dnskey_digest_len;
213 debug3("verify_host_key_dns");
215 fatal("No key to look up!");
217 if (is_numeric_hostname(hostname)) {
218 debug("skipped DNS lookup for numerical hostname");
222 result = getrrsetbyname(hostname, DNS_RDATACLASS_IN,
223 DNS_RDATATYPE_SSHFP, 0, &fingerprints);
225 verbose("DNS lookup error: %s", dns_result_totext(result));
229 if (fingerprints->rri_flags & RRSET_VALIDATED) {
230 *flags |= DNS_VERIFY_SECURE;
231 debug("found %d secure fingerprints in DNS",
232 fingerprints->rri_nrdatas);
234 debug("found %d insecure fingerprints in DNS",
235 fingerprints->rri_nrdatas);
238 /* Initialize default host key parameters */
239 if (!dns_read_key(&hostkey_algorithm, &hostkey_digest_type,
240 &hostkey_digest, &hostkey_digest_len, hostkey)) {
241 error("Error calculating host key fingerprint.");
242 freerrset(fingerprints);
246 if (fingerprints->rri_nrdatas)
247 *flags |= DNS_VERIFY_FOUND;
249 for (counter = 0; counter < fingerprints->rri_nrdatas; counter++) {
251 * Extract the key from the answer. Ignore any badly
252 * formatted fingerprints.
254 if (!dns_read_rdata(&dnskey_algorithm, &dnskey_digest_type,
255 &dnskey_digest, &dnskey_digest_len,
256 fingerprints->rri_rdatas[counter].rdi_data,
257 fingerprints->rri_rdatas[counter].rdi_length)) {
258 verbose("Error parsing fingerprint from DNS.");
262 if (hostkey_digest_type != dnskey_digest_type) {
263 hostkey_digest_type = dnskey_digest_type;
264 xfree(hostkey_digest);
266 /* Initialize host key parameters */
267 if (!dns_read_key(&hostkey_algorithm,
268 &hostkey_digest_type, &hostkey_digest,
269 &hostkey_digest_len, hostkey)) {
270 error("Error calculating key fingerprint.");
271 freerrset(fingerprints);
276 /* Check if the current key is the same as the given key */
277 if (hostkey_algorithm == dnskey_algorithm &&
278 hostkey_digest_type == dnskey_digest_type) {
279 if (hostkey_digest_len == dnskey_digest_len &&
280 timingsafe_bcmp(hostkey_digest, dnskey_digest,
281 hostkey_digest_len) == 0)
282 *flags |= DNS_VERIFY_MATCH;
284 xfree(dnskey_digest);
287 xfree(hostkey_digest); /* from key_fingerprint_raw() */
288 freerrset(fingerprints);
290 if (*flags & DNS_VERIFY_FOUND)
291 if (*flags & DNS_VERIFY_MATCH)
292 debug("matching host key fingerprint found in DNS");
294 debug("mismatching host key fingerprint found in DNS");
296 debug("no host key fingerprint found in DNS");
302 * Export the fingerprint of a key as a DNS resource record
305 export_dns_rr(const char *hostname, Key *key, FILE *f, int generic)
307 u_int8_t rdata_pubkey_algorithm = 0;
308 u_int8_t rdata_digest_type = SSHFP_HASH_RESERVED;
310 u_char *rdata_digest;
311 u_int i, rdata_digest_len;
314 for (dtype = SSHFP_HASH_SHA1; dtype < SSHFP_HASH_MAX; dtype++) {
315 rdata_digest_type = dtype;
316 if (dns_read_key(&rdata_pubkey_algorithm, &rdata_digest_type,
317 &rdata_digest, &rdata_digest_len, key)) {
319 fprintf(f, "%s IN TYPE%d \\# %d %02x %02x ",
320 hostname, DNS_RDATATYPE_SSHFP,
321 2 + rdata_digest_len,
322 rdata_pubkey_algorithm, rdata_digest_type);
324 fprintf(f, "%s IN SSHFP %d %d ", hostname,
325 rdata_pubkey_algorithm, rdata_digest_type);
327 for (i = 0; i < rdata_digest_len; i++)
328 fprintf(f, "%02x", rdata_digest[i]);
330 xfree(rdata_digest); /* from key_fingerprint_raw() */
335 /* No SSHFP record was generated at all */
337 error("%s: unsupported algorithm and/or digest_type", __func__);