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5b04a8bf | 1 | /* $OpenBSD: dns.c,v 1.20 2006/07/08 21:47:12 stevesk Exp $ */ |
21289cd0 | 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 | ||
21289cd0 | 28 | #include "includes.h" |
29 | ||
5b04a8bf | 30 | #include <sys/types.h> |
31 | #include <sys/socket.h> | |
32 | ||
21289cd0 | 33 | #include <netdb.h> |
21289cd0 | 34 | |
35 | #include "xmalloc.h" | |
36 | #include "key.h" | |
37 | #include "dns.h" | |
38 | #include "log.h" | |
21289cd0 | 39 | |
21289cd0 | 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 */ | |
47 | }; | |
48 | ||
49 | static const char * | |
ca75d7de | 50 | dns_result_totext(unsigned int res) |
21289cd0 | 51 | { |
ca75d7de | 52 | switch (res) { |
21289cd0 | 53 | case ERRSET_SUCCESS: |
54 | return errset_text[ERRSET_SUCCESS]; | |
55 | case ERRSET_NOMEMORY: | |
56 | return errset_text[ERRSET_NOMEMORY]; | |
57 | case ERRSET_FAIL: | |
58 | return errset_text[ERRSET_FAIL]; | |
59 | case ERRSET_INVAL: | |
60 | return errset_text[ERRSET_INVAL]; | |
61 | case ERRSET_NONAME: | |
62 | return errset_text[ERRSET_NONAME]; | |
63 | case ERRSET_NODATA: | |
64 | return errset_text[ERRSET_NODATA]; | |
65 | default: | |
66 | return "unknown error"; | |
67 | } | |
68 | } | |
21289cd0 | 69 | |
70 | /* | |
71 | * Read SSHFP parameters from key buffer. | |
72 | */ | |
73 | static int | |
74 | dns_read_key(u_int8_t *algorithm, u_int8_t *digest_type, | |
0161a13d | 75 | u_char **digest, u_int *digest_len, const Key *key) |
21289cd0 | 76 | { |
77 | int success = 0; | |
78 | ||
79 | switch (key->type) { | |
80 | case KEY_RSA: | |
81 | *algorithm = SSHFP_KEY_RSA; | |
82 | break; | |
83 | case KEY_DSA: | |
84 | *algorithm = SSHFP_KEY_DSA; | |
85 | break; | |
86 | default: | |
4d3434f7 | 87 | *algorithm = SSHFP_KEY_RESERVED; /* 0 */ |
21289cd0 | 88 | } |
89 | ||
90 | if (*algorithm) { | |
91 | *digest_type = SSHFP_HASH_SHA1; | |
92 | *digest = key_fingerprint_raw(key, SSH_FP_SHA1, digest_len); | |
4d3434f7 | 93 | if (*digest == NULL) |
94 | fatal("dns_read_key: null from key_fingerprint_raw()"); | |
21289cd0 | 95 | success = 1; |
96 | } else { | |
97 | *digest_type = SSHFP_HASH_RESERVED; | |
98 | *digest = NULL; | |
99 | *digest_len = 0; | |
100 | success = 0; | |
101 | } | |
102 | ||
103 | return success; | |
104 | } | |
105 | ||
106 | /* | |
107 | * Read SSHFP parameters from rdata buffer. | |
108 | */ | |
109 | static int | |
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) | |
112 | { | |
113 | int success = 0; | |
114 | ||
115 | *algorithm = SSHFP_KEY_RESERVED; | |
116 | *digest_type = SSHFP_HASH_RESERVED; | |
117 | ||
118 | if (rdata_len >= 2) { | |
119 | *algorithm = rdata[0]; | |
120 | *digest_type = rdata[1]; | |
121 | *digest_len = rdata_len - 2; | |
122 | ||
123 | if (*digest_len > 0) { | |
124 | *digest = (u_char *) xmalloc(*digest_len); | |
125 | memcpy(*digest, rdata + 2, *digest_len); | |
126 | } else { | |
6cfe93ec | 127 | *digest = (u_char *)xstrdup(""); |
21289cd0 | 128 | } |
129 | ||
130 | success = 1; | |
131 | } | |
132 | ||
133 | return success; | |
134 | } | |
135 | ||
4635e729 | 136 | /* |
137 | * Check if hostname is numerical. | |
138 | * Returns -1 if hostname is numeric, 0 otherwise | |
139 | */ | |
140 | static int | |
141 | is_numeric_hostname(const char *hostname) | |
142 | { | |
143 | struct addrinfo hints, *ai; | |
144 | ||
145 | memset(&hints, 0, sizeof(hints)); | |
146 | hints.ai_socktype = SOCK_DGRAM; | |
147 | hints.ai_flags = AI_NUMERICHOST; | |
148 | ||
149 | if (getaddrinfo(hostname, "0", &hints, &ai) == 0) { | |
150 | freeaddrinfo(ai); | |
151 | return -1; | |
152 | } | |
153 | ||
154 | return 0; | |
155 | } | |
21289cd0 | 156 | |
157 | /* | |
158 | * Verify the given hostname, address and host key using DNS. | |
aff51935 | 159 | * Returns 0 if lookup succeeds, -1 otherwise |
21289cd0 | 160 | */ |
161 | int | |
162 | verify_host_key_dns(const char *hostname, struct sockaddr *address, | |
0161a13d | 163 | const Key *hostkey, int *flags) |
21289cd0 | 164 | { |
2ceb8101 | 165 | u_int counter; |
21289cd0 | 166 | int result; |
167 | struct rrsetinfo *fingerprints = NULL; | |
21289cd0 | 168 | |
169 | u_int8_t hostkey_algorithm; | |
170 | u_int8_t hostkey_digest_type; | |
171 | u_char *hostkey_digest; | |
172 | u_int hostkey_digest_len; | |
173 | ||
174 | u_int8_t dnskey_algorithm; | |
175 | u_int8_t dnskey_digest_type; | |
176 | u_char *dnskey_digest; | |
177 | u_int dnskey_digest_len; | |
178 | ||
0161a13d | 179 | *flags = 0; |
21289cd0 | 180 | |
8374cf6f | 181 | debug3("verify_host_key_dns"); |
21289cd0 | 182 | if (hostkey == NULL) |
183 | fatal("No key to look up!"); | |
184 | ||
4635e729 | 185 | if (is_numeric_hostname(hostname)) { |
186 | debug("skipped DNS lookup for numerical hostname"); | |
187 | return -1; | |
188 | } | |
189 | ||
21289cd0 | 190 | result = getrrsetbyname(hostname, DNS_RDATACLASS_IN, |
191 | DNS_RDATATYPE_SSHFP, 0, &fingerprints); | |
192 | if (result) { | |
193 | verbose("DNS lookup error: %s", dns_result_totext(result)); | |
0161a13d | 194 | return -1; |
21289cd0 | 195 | } |
196 | ||
0161a13d | 197 | if (fingerprints->rri_flags & RRSET_VALIDATED) { |
198 | *flags |= DNS_VERIFY_SECURE; | |
199 | debug("found %d secure fingerprints in DNS", | |
200 | fingerprints->rri_nrdatas); | |
201 | } else { | |
202 | debug("found %d insecure fingerprints in DNS", | |
203 | fingerprints->rri_nrdatas); | |
21289cd0 | 204 | } |
21289cd0 | 205 | |
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."); | |
b414a17b | 210 | freerrset(fingerprints); |
0161a13d | 211 | return -1; |
21289cd0 | 212 | } |
213 | ||
0161a13d | 214 | if (fingerprints->rri_nrdatas) |
215 | *flags |= DNS_VERIFY_FOUND; | |
216 | ||
adf8c40b | 217 | for (counter = 0; counter < fingerprints->rri_nrdatas; counter++) { |
21289cd0 | 218 | /* |
219 | * Extract the key from the answer. Ignore any badly | |
220 | * formatted fingerprints. | |
221 | */ | |
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."); | |
227 | continue; | |
228 | } | |
229 | ||
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) { | |
233 | ||
234 | if (hostkey_digest_len == dnskey_digest_len && | |
235 | memcmp(hostkey_digest, dnskey_digest, | |
236 | hostkey_digest_len) == 0) { | |
237 | ||
0161a13d | 238 | *flags |= DNS_VERIFY_MATCH; |
21289cd0 | 239 | } |
240 | } | |
4d3434f7 | 241 | xfree(dnskey_digest); |
21289cd0 | 242 | } |
243 | ||
4d3434f7 | 244 | xfree(hostkey_digest); /* from key_fingerprint_raw() */ |
21289cd0 | 245 | freerrset(fingerprints); |
246 | ||
0161a13d | 247 | if (*flags & DNS_VERIFY_FOUND) |
248 | if (*flags & DNS_VERIFY_MATCH) | |
249 | debug("matching host key fingerprint found in DNS"); | |
250 | else | |
251 | debug("mismatching host key fingerprint found in DNS"); | |
252 | else | |
253 | debug("no host key fingerprint found in DNS"); | |
21289cd0 | 254 | |
0161a13d | 255 | return 0; |
21289cd0 | 256 | } |
257 | ||
21289cd0 | 258 | /* |
259 | * Export the fingerprint of a key as a DNS resource record | |
260 | */ | |
261 | int | |
0161a13d | 262 | export_dns_rr(const char *hostname, const Key *key, FILE *f, int generic) |
21289cd0 | 263 | { |
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; | |
268 | ||
2ceb8101 | 269 | u_int i; |
21289cd0 | 270 | int success = 0; |
271 | ||
272 | if (dns_read_key(&rdata_pubkey_algorithm, &rdata_digest_type, | |
8374cf6f | 273 | &rdata_digest, &rdata_digest_len, key)) { |
21289cd0 | 274 | |
275 | if (generic) | |
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); | |
279 | else | |
280 | fprintf(f, "%s IN SSHFP %d %d ", hostname, | |
281 | rdata_pubkey_algorithm, rdata_digest_type); | |
282 | ||
283 | for (i = 0; i < rdata_digest_len; i++) | |
284 | fprintf(f, "%02x", rdata_digest[i]); | |
285 | fprintf(f, "\n"); | |
4d3434f7 | 286 | xfree(rdata_digest); /* from key_fingerprint_raw() */ |
21289cd0 | 287 | success = 1; |
288 | } else { | |
8374cf6f | 289 | error("export_dns_rr: unsupported algorithm"); |
21289cd0 | 290 | } |
291 | ||
292 | return success; | |
293 | } |