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416fd2a8 | 1 | /* $OpenBSD: dns.c,v 1.9 2003/11/21 11:57:03 djm 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 | ||
28 | ||
29 | #include "includes.h" | |
30 | ||
70791e56 | 31 | #include <openssl/bn.h> |
32 | #ifdef LWRES | |
33 | #include <lwres/netdb.h> | |
34 | #include <dns/result.h> | |
35 | #else /* LWRES */ | |
36 | #include <netdb.h> | |
37 | #endif /* LWRES */ | |
38 | ||
39 | #include "xmalloc.h" | |
40 | #include "key.h" | |
41 | #include "dns.h" | |
42 | #include "log.h" | |
43 | #include "uuencode.h" | |
44 | ||
45 | extern char *__progname; | |
416fd2a8 | 46 | RCSID("$OpenBSD: dns.c,v 1.9 2003/11/21 11:57:03 djm Exp $"); |
70791e56 | 47 | |
48 | #ifndef LWRES | |
49 | static const char *errset_text[] = { | |
50 | "success", /* 0 ERRSET_SUCCESS */ | |
51 | "out of memory", /* 1 ERRSET_NOMEMORY */ | |
52 | "general failure", /* 2 ERRSET_FAIL */ | |
53 | "invalid parameter", /* 3 ERRSET_INVAL */ | |
54 | "name does not exist", /* 4 ERRSET_NONAME */ | |
55 | "data does not exist", /* 5 ERRSET_NODATA */ | |
56 | }; | |
57 | ||
58 | static const char * | |
59 | dns_result_totext(unsigned int error) | |
60 | { | |
61 | switch (error) { | |
62 | case ERRSET_SUCCESS: | |
63 | return errset_text[ERRSET_SUCCESS]; | |
64 | case ERRSET_NOMEMORY: | |
65 | return errset_text[ERRSET_NOMEMORY]; | |
66 | case ERRSET_FAIL: | |
67 | return errset_text[ERRSET_FAIL]; | |
68 | case ERRSET_INVAL: | |
69 | return errset_text[ERRSET_INVAL]; | |
70 | case ERRSET_NONAME: | |
71 | return errset_text[ERRSET_NONAME]; | |
72 | case ERRSET_NODATA: | |
73 | return errset_text[ERRSET_NODATA]; | |
74 | default: | |
75 | return "unknown error"; | |
76 | } | |
77 | } | |
78 | #endif /* LWRES */ | |
79 | ||
80 | ||
81 | /* | |
82 | * Read SSHFP parameters from key buffer. | |
83 | */ | |
84 | static int | |
85 | dns_read_key(u_int8_t *algorithm, u_int8_t *digest_type, | |
416fd2a8 | 86 | u_char **digest, u_int *digest_len, const Key *key) |
70791e56 | 87 | { |
88 | int success = 0; | |
89 | ||
90 | switch (key->type) { | |
91 | case KEY_RSA: | |
92 | *algorithm = SSHFP_KEY_RSA; | |
93 | break; | |
94 | case KEY_DSA: | |
95 | *algorithm = SSHFP_KEY_DSA; | |
96 | break; | |
97 | default: | |
98 | *algorithm = SSHFP_KEY_RESERVED; | |
99 | } | |
100 | ||
101 | if (*algorithm) { | |
102 | *digest_type = SSHFP_HASH_SHA1; | |
103 | *digest = key_fingerprint_raw(key, SSH_FP_SHA1, digest_len); | |
104 | success = 1; | |
105 | } else { | |
106 | *digest_type = SSHFP_HASH_RESERVED; | |
107 | *digest = NULL; | |
108 | *digest_len = 0; | |
109 | success = 0; | |
110 | } | |
111 | ||
112 | return success; | |
113 | } | |
114 | ||
115 | /* | |
116 | * Read SSHFP parameters from rdata buffer. | |
117 | */ | |
118 | static int | |
119 | dns_read_rdata(u_int8_t *algorithm, u_int8_t *digest_type, | |
120 | u_char **digest, u_int *digest_len, u_char *rdata, int rdata_len) | |
121 | { | |
122 | int success = 0; | |
123 | ||
124 | *algorithm = SSHFP_KEY_RESERVED; | |
125 | *digest_type = SSHFP_HASH_RESERVED; | |
126 | ||
127 | if (rdata_len >= 2) { | |
128 | *algorithm = rdata[0]; | |
129 | *digest_type = rdata[1]; | |
130 | *digest_len = rdata_len - 2; | |
131 | ||
132 | if (*digest_len > 0) { | |
133 | *digest = (u_char *) xmalloc(*digest_len); | |
134 | memcpy(*digest, rdata + 2, *digest_len); | |
135 | } else { | |
136 | *digest = NULL; | |
137 | } | |
138 | ||
139 | success = 1; | |
140 | } | |
141 | ||
142 | return success; | |
143 | } | |
144 | ||
145 | ||
146 | /* | |
147 | * Verify the given hostname, address and host key using DNS. | |
416fd2a8 | 148 | * Returns 0 if lookup succeeds, -1 otherwise |
70791e56 | 149 | */ |
150 | int | |
151 | verify_host_key_dns(const char *hostname, struct sockaddr *address, | |
416fd2a8 | 152 | const Key *hostkey, int *flags) |
70791e56 | 153 | { |
154 | int counter; | |
155 | int result; | |
156 | struct rrsetinfo *fingerprints = NULL; | |
70791e56 | 157 | |
158 | u_int8_t hostkey_algorithm; | |
159 | u_int8_t hostkey_digest_type; | |
160 | u_char *hostkey_digest; | |
161 | u_int hostkey_digest_len; | |
162 | ||
163 | u_int8_t dnskey_algorithm; | |
164 | u_int8_t dnskey_digest_type; | |
165 | u_char *dnskey_digest; | |
166 | u_int dnskey_digest_len; | |
167 | ||
416fd2a8 | 168 | *flags = 0; |
70791e56 | 169 | |
170 | debug3("verify_hostkey_dns"); | |
171 | if (hostkey == NULL) | |
172 | fatal("No key to look up!"); | |
173 | ||
174 | result = getrrsetbyname(hostname, DNS_RDATACLASS_IN, | |
175 | DNS_RDATATYPE_SSHFP, 0, &fingerprints); | |
176 | if (result) { | |
177 | verbose("DNS lookup error: %s", dns_result_totext(result)); | |
416fd2a8 | 178 | return -1; |
70791e56 | 179 | } |
180 | ||
416fd2a8 | 181 | if (fingerprints->rri_flags & RRSET_VALIDATED) { |
182 | *flags |= DNS_VERIFY_SECURE; | |
183 | debug("found %d secure fingerprints in DNS", | |
184 | fingerprints->rri_nrdatas); | |
185 | } else { | |
186 | debug("found %d insecure fingerprints in DNS", | |
187 | fingerprints->rri_nrdatas); | |
70791e56 | 188 | } |
70791e56 | 189 | |
190 | /* Initialize host key parameters */ | |
191 | if (!dns_read_key(&hostkey_algorithm, &hostkey_digest_type, | |
192 | &hostkey_digest, &hostkey_digest_len, hostkey)) { | |
193 | error("Error calculating host key fingerprint."); | |
194 | freerrset(fingerprints); | |
416fd2a8 | 195 | return -1; |
70791e56 | 196 | } |
197 | ||
416fd2a8 | 198 | if (fingerprints->rri_nrdatas) |
199 | *flags |= DNS_VERIFY_FOUND; | |
200 | ||
70791e56 | 201 | for (counter = 0 ; counter < fingerprints->rri_nrdatas ; counter++) { |
202 | /* | |
203 | * Extract the key from the answer. Ignore any badly | |
204 | * formatted fingerprints. | |
205 | */ | |
206 | if (!dns_read_rdata(&dnskey_algorithm, &dnskey_digest_type, | |
207 | &dnskey_digest, &dnskey_digest_len, | |
208 | fingerprints->rri_rdatas[counter].rdi_data, | |
209 | fingerprints->rri_rdatas[counter].rdi_length)) { | |
210 | verbose("Error parsing fingerprint from DNS."); | |
211 | continue; | |
212 | } | |
213 | ||
214 | /* Check if the current key is the same as the given key */ | |
215 | if (hostkey_algorithm == dnskey_algorithm && | |
216 | hostkey_digest_type == dnskey_digest_type) { | |
217 | ||
218 | if (hostkey_digest_len == dnskey_digest_len && | |
219 | memcmp(hostkey_digest, dnskey_digest, | |
220 | hostkey_digest_len) == 0) { | |
221 | ||
416fd2a8 | 222 | *flags |= DNS_VERIFY_MATCH; |
70791e56 | 223 | } |
224 | } | |
225 | } | |
226 | ||
227 | freerrset(fingerprints); | |
228 | ||
416fd2a8 | 229 | if (*flags & DNS_VERIFY_FOUND) |
230 | if (*flags & DNS_VERIFY_MATCH) | |
231 | debug("matching host key fingerprint found in DNS"); | |
232 | else | |
233 | debug("mismatching host key fingerprint found in DNS"); | |
234 | else | |
235 | debug("no host key fingerprint found in DNS"); | |
70791e56 | 236 | |
416fd2a8 | 237 | return 0; |
70791e56 | 238 | } |
239 | ||
240 | ||
241 | /* | |
242 | * Export the fingerprint of a key as a DNS resource record | |
243 | */ | |
244 | int | |
416fd2a8 | 245 | export_dns_rr(const char *hostname, const Key *key, FILE *f, int generic) |
70791e56 | 246 | { |
247 | u_int8_t rdata_pubkey_algorithm = 0; | |
248 | u_int8_t rdata_digest_type = SSHFP_HASH_SHA1; | |
249 | u_char *rdata_digest; | |
250 | u_int rdata_digest_len; | |
251 | ||
252 | int i; | |
253 | int success = 0; | |
254 | ||
255 | if (dns_read_key(&rdata_pubkey_algorithm, &rdata_digest_type, | |
256 | &rdata_digest, &rdata_digest_len, key)) { | |
257 | ||
258 | if (generic) | |
259 | fprintf(f, "%s IN TYPE%d \\# %d %02x %02x ", hostname, | |
260 | DNS_RDATATYPE_SSHFP, 2 + rdata_digest_len, | |
261 | rdata_pubkey_algorithm, rdata_digest_type); | |
262 | else | |
263 | fprintf(f, "%s IN SSHFP %d %d ", hostname, | |
264 | rdata_pubkey_algorithm, rdata_digest_type); | |
265 | ||
266 | for (i = 0; i < rdata_digest_len; i++) | |
267 | fprintf(f, "%02x", rdata_digest[i]); | |
268 | fprintf(f, "\n"); | |
269 | success = 1; | |
270 | } else { | |
271 | error("dns_export_rr: unsupported algorithm"); | |
272 | } | |
273 | ||
274 | return success; | |
275 | } |