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2e437378 | 1 | /* $OpenBSD: dns.c,v 1.23 2006/08/03 03:34:42 deraadt Exp $ */ |
70791e56 | 2 | |
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 | ||
70791e56 | 28 | #include "includes.h" |
2e437378 | 29 | |
30 | #include <sys/types.h> | |
31 | #include <sys/socket.h> | |
70791e56 | 32 | |
70791e56 | 33 | #include <netdb.h> |
2e437378 | 34 | #include <stdarg.h> |
35 | #include <stdio.h> | |
36 | #include <string.h> | |
70791e56 | 37 | |
38 | #include "xmalloc.h" | |
39 | #include "key.h" | |
40 | #include "dns.h" | |
41 | #include "log.h" | |
70791e56 | 42 | |
70791e56 | 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 */ | |
50 | }; | |
51 | ||
52 | static const char * | |
1b56ff3d | 53 | dns_result_totext(unsigned int res) |
70791e56 | 54 | { |
1b56ff3d | 55 | switch (res) { |
70791e56 | 56 | 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 | } | |
70791e56 | 72 | |
73 | /* | |
74 | * Read SSHFP parameters from key buffer. | |
75 | */ | |
76 | static int | |
77 | dns_read_key(u_int8_t *algorithm, u_int8_t *digest_type, | |
416fd2a8 | 78 | u_char **digest, u_int *digest_len, const Key *key) |
70791e56 | 79 | { |
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: | |
e00da40d | 90 | *algorithm = SSHFP_KEY_RESERVED; /* 0 */ |
70791e56 | 91 | } |
92 | ||
93 | if (*algorithm) { | |
94 | *digest_type = SSHFP_HASH_SHA1; | |
95 | *digest = key_fingerprint_raw(key, SSH_FP_SHA1, digest_len); | |
e00da40d | 96 | if (*digest == NULL) |
97 | fatal("dns_read_key: null from key_fingerprint_raw()"); | |
70791e56 | 98 | 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 | */ | |
112 | static int | |
113 | dns_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 { | |
2e437378 | 130 | *digest = (u_char *)xstrdup(""); |
70791e56 | 131 | } |
132 | ||
133 | success = 1; | |
134 | } | |
135 | ||
136 | return success; | |
137 | } | |
138 | ||
34fee935 | 139 | /* |
140 | * Check if hostname is numerical. | |
141 | * Returns -1 if hostname is numeric, 0 otherwise | |
142 | */ | |
143 | static int | |
144 | is_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 | } | |
70791e56 | 159 | |
160 | /* | |
161 | * Verify the given hostname, address and host key using DNS. | |
416fd2a8 | 162 | * Returns 0 if lookup succeeds, -1 otherwise |
70791e56 | 163 | */ |
164 | int | |
165 | verify_host_key_dns(const char *hostname, struct sockaddr *address, | |
416fd2a8 | 166 | const Key *hostkey, int *flags) |
70791e56 | 167 | { |
34fee935 | 168 | u_int counter; |
70791e56 | 169 | int result; |
170 | struct rrsetinfo *fingerprints = NULL; | |
70791e56 | 171 | |
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 | ||
416fd2a8 | 182 | *flags = 0; |
70791e56 | 183 | |
e00da40d | 184 | debug3("verify_host_key_dns"); |
70791e56 | 185 | if (hostkey == NULL) |
186 | fatal("No key to look up!"); | |
187 | ||
34fee935 | 188 | if (is_numeric_hostname(hostname)) { |
189 | debug("skipped DNS lookup for numerical hostname"); | |
190 | return -1; | |
191 | } | |
192 | ||
70791e56 | 193 | 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)); | |
416fd2a8 | 197 | return -1; |
70791e56 | 198 | } |
199 | ||
416fd2a8 | 200 | 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); | |
70791e56 | 207 | } |
70791e56 | 208 | |
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."); | |
213 | freerrset(fingerprints); | |
416fd2a8 | 214 | return -1; |
70791e56 | 215 | } |
216 | ||
416fd2a8 | 217 | if (fingerprints->rri_nrdatas) |
218 | *flags |= DNS_VERIFY_FOUND; | |
219 | ||
e00da40d | 220 | for (counter = 0; counter < fingerprints->rri_nrdatas; counter++) { |
70791e56 | 221 | /* |
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 | ||
416fd2a8 | 241 | *flags |= DNS_VERIFY_MATCH; |
70791e56 | 242 | } |
243 | } | |
e00da40d | 244 | xfree(dnskey_digest); |
70791e56 | 245 | } |
246 | ||
e00da40d | 247 | xfree(hostkey_digest); /* from key_fingerprint_raw() */ |
70791e56 | 248 | freerrset(fingerprints); |
249 | ||
416fd2a8 | 250 | 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"); | |
70791e56 | 257 | |
416fd2a8 | 258 | return 0; |
70791e56 | 259 | } |
260 | ||
70791e56 | 261 | /* |
262 | * Export the fingerprint of a key as a DNS resource record | |
263 | */ | |
264 | int | |
416fd2a8 | 265 | export_dns_rr(const char *hostname, const Key *key, FILE *f, int generic) |
70791e56 | 266 | { |
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 | ||
34fee935 | 272 | u_int i; |
70791e56 | 273 | int success = 0; |
274 | ||
275 | if (dns_read_key(&rdata_pubkey_algorithm, &rdata_digest_type, | |
e00da40d | 276 | &rdata_digest, &rdata_digest_len, key)) { |
70791e56 | 277 | |
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"); | |
e00da40d | 289 | xfree(rdata_digest); /* from key_fingerprint_raw() */ |
70791e56 | 290 | success = 1; |
291 | } else { | |
e00da40d | 292 | error("export_dns_rr: unsupported algorithm"); |
70791e56 | 293 | } |
294 | ||
295 | return success; | |
296 | } |