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Damien Millerd7834352006-08-05 12:39:39 +10001/* $OpenBSD: dns.c,v 1.23 2006/08/03 03:34:42 deraadt 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
Damien Miller37876e92003-05-15 10:19:46 +100028#include "includes.h"
29
Damien Millere3b60b52006-07-10 21:08:03 +100030#include <sys/types.h>
31#include <sys/socket.h>
32
Damien Millerb8fe89c2006-07-24 14:51:00 +100033#include <netdb.h>
Damien Millerded319c2006-09-01 15:38:36 +100034#include <stdarg.h>
Damien Millera7a73ee2006-08-05 11:37:59 +100035#include <stdio.h>
Damien Millere3476ed2006-07-24 14:13:33 +100036#include <string.h>
Damien Miller37876e92003-05-15 10:19:46 +100037
38#include "xmalloc.h"
39#include "key.h"
40#include "dns.h"
41#include "log.h"
Damien Miller37876e92003-05-15 10:19:46 +100042
Damien Miller37876e92003-05-15 10:19:46 +100043static 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 */
50};
51
52static const char *
Darren Tucker3f9fdc72004-06-22 12:56:01 +100053dns_result_totext(unsigned int res)
Damien Miller37876e92003-05-15 10:19:46 +100054{
Darren Tucker3f9fdc72004-06-22 12:56:01 +100055 switch (res) {
Damien Miller37876e92003-05-15 10:19:46 +100056 case ERRSET_SUCCESS:
57 return errset_text[ERRSET_SUCCESS];
58 case ERRSET_NOMEMORY:
59 return errset_text[ERRSET_NOMEMORY];
60 case ERRSET_FAIL:
61 return errset_text[ERRSET_FAIL];
62 case ERRSET_INVAL:
63 return errset_text[ERRSET_INVAL];
64 case ERRSET_NONAME:
65 return errset_text[ERRSET_NONAME];
66 case ERRSET_NODATA:
67 return errset_text[ERRSET_NODATA];
68 default:
69 return "unknown error";
70 }
71}
Damien Miller37876e92003-05-15 10:19:46 +100072
73/*
74 * Read SSHFP parameters from key buffer.
75 */
76static int
77dns_read_key(u_int8_t *algorithm, u_int8_t *digest_type,
Damien Miller150b5572003-11-17 21:19:29 +110078 u_char **digest, u_int *digest_len, const Key *key)
Damien Miller37876e92003-05-15 10:19:46 +100079{
80 int success = 0;
81
82 switch (key->type) {
83 case KEY_RSA:
84 *algorithm = SSHFP_KEY_RSA;
85 break;
86 case KEY_DSA:
87 *algorithm = SSHFP_KEY_DSA;
88 break;
89 default:
Damien Miller65712492005-11-05 15:09:27 +110090 *algorithm = SSHFP_KEY_RESERVED; /* 0 */
Damien Miller37876e92003-05-15 10:19:46 +100091 }
92
93 if (*algorithm) {
94 *digest_type = SSHFP_HASH_SHA1;
95 *digest = key_fingerprint_raw(key, SSH_FP_SHA1, digest_len);
Damien Miller65712492005-11-05 15:09:27 +110096 if (*digest == NULL)
97 fatal("dns_read_key: null from key_fingerprint_raw()");
Damien Miller37876e92003-05-15 10:19:46 +100098 success = 1;
99 } else {
100 *digest_type = SSHFP_HASH_RESERVED;
101 *digest = NULL;
102 *digest_len = 0;
103 success = 0;
104 }
105
106 return success;
107}
108
109/*
110 * Read SSHFP parameters from rdata buffer.
111 */
112static int
113dns_read_rdata(u_int8_t *algorithm, u_int8_t *digest_type,
114 u_char **digest, u_int *digest_len, u_char *rdata, int rdata_len)
115{
116 int success = 0;
117
118 *algorithm = SSHFP_KEY_RESERVED;
119 *digest_type = SSHFP_HASH_RESERVED;
120
121 if (rdata_len >= 2) {
122 *algorithm = rdata[0];
123 *digest_type = rdata[1];
124 *digest_len = rdata_len - 2;
125
126 if (*digest_len > 0) {
127 *digest = (u_char *) xmalloc(*digest_len);
128 memcpy(*digest, rdata + 2, *digest_len);
129 } else {
Damien Miller59962942006-03-26 00:06:48 +1100130 *digest = (u_char *)xstrdup("");
Damien Miller37876e92003-05-15 10:19:46 +1000131 }
132
133 success = 1;
134 }
135
136 return success;
137}
138
Damien Millera31c9292005-05-26 12:03:31 +1000139/*
140 * Check if hostname is numerical.
141 * Returns -1 if hostname is numeric, 0 otherwise
142 */
143static int
144is_numeric_hostname(const char *hostname)
145{
146 struct addrinfo hints, *ai;
147
148 memset(&hints, 0, sizeof(hints));
149 hints.ai_socktype = SOCK_DGRAM;
150 hints.ai_flags = AI_NUMERICHOST;
151
152 if (getaddrinfo(hostname, "0", &hints, &ai) == 0) {
153 freeaddrinfo(ai);
154 return -1;
155 }
156
157 return 0;
158}
Damien Miller37876e92003-05-15 10:19:46 +1000159
160/*
161 * Verify the given hostname, address and host key using DNS.
Damien Millera8e06ce2003-11-21 23:48:55 +1100162 * Returns 0 if lookup succeeds, -1 otherwise
Damien Miller37876e92003-05-15 10:19:46 +1000163 */
164int
165verify_host_key_dns(const char *hostname, struct sockaddr *address,
Damien Miller150b5572003-11-17 21:19:29 +1100166 const Key *hostkey, int *flags)
Damien Miller37876e92003-05-15 10:19:46 +1000167{
Damien Millereccb9de2005-06-17 12:59:34 +1000168 u_int counter;
Damien Miller37876e92003-05-15 10:19:46 +1000169 int result;
170 struct rrsetinfo *fingerprints = NULL;
Damien Miller37876e92003-05-15 10:19:46 +1000171
172 u_int8_t hostkey_algorithm;
173 u_int8_t hostkey_digest_type;
174 u_char *hostkey_digest;
175 u_int hostkey_digest_len;
176
177 u_int8_t dnskey_algorithm;
178 u_int8_t dnskey_digest_type;
179 u_char *dnskey_digest;
180 u_int dnskey_digest_len;
181
Damien Miller150b5572003-11-17 21:19:29 +1100182 *flags = 0;
Damien Miller37876e92003-05-15 10:19:46 +1000183
Damien Miller319550a2005-11-05 15:11:15 +1100184 debug3("verify_host_key_dns");
Damien Miller37876e92003-05-15 10:19:46 +1000185 if (hostkey == NULL)
186 fatal("No key to look up!");
187
Damien Millera31c9292005-05-26 12:03:31 +1000188 if (is_numeric_hostname(hostname)) {
189 debug("skipped DNS lookup for numerical hostname");
190 return -1;
191 }
192
Damien Miller37876e92003-05-15 10:19:46 +1000193 result = getrrsetbyname(hostname, DNS_RDATACLASS_IN,
194 DNS_RDATATYPE_SSHFP, 0, &fingerprints);
195 if (result) {
196 verbose("DNS lookup error: %s", dns_result_totext(result));
Damien Miller150b5572003-11-17 21:19:29 +1100197 return -1;
Damien Miller37876e92003-05-15 10:19:46 +1000198 }
199
Damien Miller150b5572003-11-17 21:19:29 +1100200 if (fingerprints->rri_flags & RRSET_VALIDATED) {
201 *flags |= DNS_VERIFY_SECURE;
202 debug("found %d secure fingerprints in DNS",
203 fingerprints->rri_nrdatas);
204 } else {
205 debug("found %d insecure fingerprints in DNS",
206 fingerprints->rri_nrdatas);
Damien Miller37876e92003-05-15 10:19:46 +1000207 }
Damien Miller37876e92003-05-15 10:19:46 +1000208
209 /* Initialize host key parameters */
210 if (!dns_read_key(&hostkey_algorithm, &hostkey_digest_type,
211 &hostkey_digest, &hostkey_digest_len, hostkey)) {
212 error("Error calculating host key fingerprint.");
Damien Millerb0622652003-05-15 13:27:28 +1000213 freerrset(fingerprints);
Damien Miller150b5572003-11-17 21:19:29 +1100214 return -1;
Damien Miller37876e92003-05-15 10:19:46 +1000215 }
216
Damien Miller150b5572003-11-17 21:19:29 +1100217 if (fingerprints->rri_nrdatas)
218 *flags |= DNS_VERIFY_FOUND;
219
Damien Miller20afc242005-11-05 15:06:38 +1100220 for (counter = 0; counter < fingerprints->rri_nrdatas; counter++) {
Damien Miller37876e92003-05-15 10:19:46 +1000221 /*
222 * Extract the key from the answer. Ignore any badly
223 * formatted fingerprints.
224 */
225 if (!dns_read_rdata(&dnskey_algorithm, &dnskey_digest_type,
226 &dnskey_digest, &dnskey_digest_len,
227 fingerprints->rri_rdatas[counter].rdi_data,
228 fingerprints->rri_rdatas[counter].rdi_length)) {
229 verbose("Error parsing fingerprint from DNS.");
230 continue;
231 }
232
233 /* Check if the current key is the same as the given key */
234 if (hostkey_algorithm == dnskey_algorithm &&
235 hostkey_digest_type == dnskey_digest_type) {
236
237 if (hostkey_digest_len == dnskey_digest_len &&
238 memcmp(hostkey_digest, dnskey_digest,
239 hostkey_digest_len) == 0) {
240
Damien Miller150b5572003-11-17 21:19:29 +1100241 *flags |= DNS_VERIFY_MATCH;
Damien Miller37876e92003-05-15 10:19:46 +1000242 }
243 }
Damien Miller65712492005-11-05 15:09:27 +1100244 xfree(dnskey_digest);
Damien Miller37876e92003-05-15 10:19:46 +1000245 }
246
Damien Miller65712492005-11-05 15:09:27 +1100247 xfree(hostkey_digest); /* from key_fingerprint_raw() */
Damien Miller37876e92003-05-15 10:19:46 +1000248 freerrset(fingerprints);
249
Damien Miller150b5572003-11-17 21:19:29 +1100250 if (*flags & DNS_VERIFY_FOUND)
251 if (*flags & DNS_VERIFY_MATCH)
252 debug("matching host key fingerprint found in DNS");
253 else
254 debug("mismatching host key fingerprint found in DNS");
255 else
256 debug("no host key fingerprint found in DNS");
Damien Miller37876e92003-05-15 10:19:46 +1000257
Damien Miller150b5572003-11-17 21:19:29 +1100258 return 0;
Damien Miller37876e92003-05-15 10:19:46 +1000259}
260
Damien Miller37876e92003-05-15 10:19:46 +1000261/*
262 * Export the fingerprint of a key as a DNS resource record
263 */
264int
Damien Miller150b5572003-11-17 21:19:29 +1100265export_dns_rr(const char *hostname, const Key *key, FILE *f, int generic)
Damien Miller37876e92003-05-15 10:19:46 +1000266{
267 u_int8_t rdata_pubkey_algorithm = 0;
268 u_int8_t rdata_digest_type = SSHFP_HASH_SHA1;
269 u_char *rdata_digest;
270 u_int rdata_digest_len;
271
Damien Millereccb9de2005-06-17 12:59:34 +1000272 u_int i;
Damien Miller37876e92003-05-15 10:19:46 +1000273 int success = 0;
274
275 if (dns_read_key(&rdata_pubkey_algorithm, &rdata_digest_type,
Damien Miller319550a2005-11-05 15:11:15 +1100276 &rdata_digest, &rdata_digest_len, key)) {
Damien Miller37876e92003-05-15 10:19:46 +1000277
278 if (generic)
279 fprintf(f, "%s IN TYPE%d \\# %d %02x %02x ", hostname,
280 DNS_RDATATYPE_SSHFP, 2 + rdata_digest_len,
281 rdata_pubkey_algorithm, rdata_digest_type);
282 else
283 fprintf(f, "%s IN SSHFP %d %d ", hostname,
284 rdata_pubkey_algorithm, rdata_digest_type);
285
286 for (i = 0; i < rdata_digest_len; i++)
287 fprintf(f, "%02x", rdata_digest[i]);
288 fprintf(f, "\n");
Damien Miller65712492005-11-05 15:09:27 +1100289 xfree(rdata_digest); /* from key_fingerprint_raw() */
Damien Miller37876e92003-05-15 10:19:46 +1000290 success = 1;
291 } else {
Damien Miller319550a2005-11-05 15:11:15 +1100292 error("export_dns_rr: unsupported algorithm");
Damien Miller37876e92003-05-15 10:19:46 +1000293 }
294
295 return success;
296}