OpenCoverage

dns.c

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1/* $OpenBSD: dns.c,v 1.38 2018/02/23 15:58:37 markus Exp $ */-
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#include "includes.h"-
29-
30#include <sys/types.h>-
31#include <sys/socket.h>-
32-
33#include <netdb.h>-
34#include <stdarg.h>-
35#include <stdio.h>-
36#include <string.h>-
37#include <stdarg.h>-
38#include <stdlib.h>-
39-
40#include "xmalloc.h"-
41#include "sshkey.h"-
42#include "ssherr.h"-
43#include "dns.h"-
44#include "log.h"-
45#include "digest.h"-
46-
47static const char *errset_text[] = {-
48 "success", /* 0 ERRSET_SUCCESS */-
49 "out of memory", /* 1 ERRSET_NOMEMORY */-
50 "general failure", /* 2 ERRSET_FAIL */-
51 "invalid parameter", /* 3 ERRSET_INVAL */-
52 "name does not exist", /* 4 ERRSET_NONAME */-
53 "data does not exist", /* 5 ERRSET_NODATA */-
54};-
55-
56static const char *-
57dns_result_totext(unsigned int res)-
58{-
59 switch (res) {-
60 case ERRSET_SUCCESS:
never executed: case 0:
0
61 return errset_text[ERRSET_SUCCESS];
never executed: return errset_text[0];
0
62 case ERRSET_NOMEMORY:
never executed: case 1:
0
63 return errset_text[ERRSET_NOMEMORY];
never executed: return errset_text[1];
0
64 case ERRSET_FAIL:
never executed: case 2:
0
65 return errset_text[ERRSET_FAIL];
never executed: return errset_text[2];
0
66 case ERRSET_INVAL:
never executed: case 3:
0
67 return errset_text[ERRSET_INVAL];
never executed: return errset_text[3];
0
68 case ERRSET_NONAME:
never executed: case 4:
0
69 return errset_text[ERRSET_NONAME];
never executed: return errset_text[4];
0
70 case ERRSET_NODATA:
never executed: case 5:
0
71 return errset_text[ERRSET_NODATA];
never executed: return errset_text[5];
0
72 default:
never executed: default:
0
73 return "unknown error";
never executed: return "unknown error";
0
74 }-
75}-
76-
77/*-
78 * Read SSHFP parameters from key buffer.-
79 */-
80static int-
81dns_read_key(u_int8_t *algorithm, u_int8_t *digest_type,-
82 u_char **digest, size_t *digest_len, struct sshkey *key)-
83{-
84 int r, success = 0;-
85 int fp_alg = -1;-
86-
87 switch (key->type) {-
88 case KEY_RSA:
never executed: case KEY_RSA:
0
89 *algorithm = SSHFP_KEY_RSA;-
90 if (!*digest_type)
!*digest_typeDescription
TRUEnever evaluated
FALSEnever evaluated
0
91 *digest_type = SSHFP_HASH_SHA1;
never executed: *digest_type = SSHFP_HASH_SHA1;
0
92 break;
never executed: break;
0
93 case KEY_DSA:
never executed: case KEY_DSA:
0
94 *algorithm = SSHFP_KEY_DSA;-
95 if (!*digest_type)
!*digest_typeDescription
TRUEnever evaluated
FALSEnever evaluated
0
96 *digest_type = SSHFP_HASH_SHA1;
never executed: *digest_type = SSHFP_HASH_SHA1;
0
97 break;
never executed: break;
0
98 case KEY_ECDSA:
never executed: case KEY_ECDSA:
0
99 *algorithm = SSHFP_KEY_ECDSA;-
100 if (!*digest_type)
!*digest_typeDescription
TRUEnever evaluated
FALSEnever evaluated
0
101 *digest_type = SSHFP_HASH_SHA256;
never executed: *digest_type = SSHFP_HASH_SHA256;
0
102 break;
never executed: break;
0
103 case KEY_ED25519:
never executed: case KEY_ED25519:
0
104 *algorithm = SSHFP_KEY_ED25519;-
105 if (!*digest_type)
!*digest_typeDescription
TRUEnever evaluated
FALSEnever evaluated
0
106 *digest_type = SSHFP_HASH_SHA256;
never executed: *digest_type = SSHFP_HASH_SHA256;
0
107 break;
never executed: break;
0
108 case KEY_XMSS:
never executed: case KEY_XMSS:
0
109 *algorithm = SSHFP_KEY_XMSS;-
110 if (!*digest_type)
!*digest_typeDescription
TRUEnever evaluated
FALSEnever evaluated
0
111 *digest_type = SSHFP_HASH_SHA256;
never executed: *digest_type = SSHFP_HASH_SHA256;
0
112 break;
never executed: break;
0
113 default:
never executed: default:
0
114 *algorithm = SSHFP_KEY_RESERVED; /* 0 */-
115 *digest_type = SSHFP_HASH_RESERVED; /* 0 */-
116 }
never executed: end of block
0
117-
118 switch (*digest_type) {-
119 case SSHFP_HASH_SHA1:
never executed: case SSHFP_HASH_SHA1:
0
120 fp_alg = SSH_DIGEST_SHA1;-
121 break;
never executed: break;
0
122 case SSHFP_HASH_SHA256:
never executed: case SSHFP_HASH_SHA256:
0
123 fp_alg = SSH_DIGEST_SHA256;-
124 break;
never executed: break;
0
125 default:
never executed: default:
0
126 *digest_type = SSHFP_HASH_RESERVED; /* 0 */-
127 }
never executed: end of block
0
128-
129 if (*algorithm && *digest_type) {
*algorithmDescription
TRUEnever evaluated
FALSEnever evaluated
*digest_typeDescription
TRUEnever evaluated
FALSEnever evaluated
0
130 if ((r = sshkey_fingerprint_raw(key, fp_alg, digest,
(r = sshkey_fi...est_len)) != 0Description
TRUEnever evaluated
FALSEnever evaluated
0
131 digest_len)) != 0)
(r = sshkey_fi...est_len)) != 0Description
TRUEnever evaluated
FALSEnever evaluated
0
132 fatal("%s: sshkey_fingerprint_raw: %s", __func__,
never executed: fatal("%s: sshkey_fingerprint_raw: %s", __func__, ssh_err(r));
0
133 ssh_err(r));
never executed: fatal("%s: sshkey_fingerprint_raw: %s", __func__, ssh_err(r));
0
134 success = 1;-
135 } else {
never executed: end of block
0
136 *digest = NULL;-
137 *digest_len = 0;-
138 success = 0;-
139 }
never executed: end of block
0
140-
141 return success;
never executed: return success;
0
142}-
143-
144/*-
145 * Read SSHFP parameters from rdata buffer.-
146 */-
147static int-
148dns_read_rdata(u_int8_t *algorithm, u_int8_t *digest_type,-
149 u_char **digest, size_t *digest_len, u_char *rdata, int rdata_len)-
150{-
151 int success = 0;-
152-
153 *algorithm = SSHFP_KEY_RESERVED;-
154 *digest_type = SSHFP_HASH_RESERVED;-
155-
156 if (rdata_len >= 2) {
rdata_len >= 2Description
TRUEnever evaluated
FALSEnever evaluated
0
157 *algorithm = rdata[0];-
158 *digest_type = rdata[1];-
159 *digest_len = rdata_len - 2;-
160-
161 if (*digest_len > 0) {
*digest_len > 0Description
TRUEnever evaluated
FALSEnever evaluated
0
162 *digest = xmalloc(*digest_len);-
163 memcpy(*digest, rdata + 2, *digest_len);-
164 } else {
never executed: end of block
0
165 *digest = (u_char *)xstrdup("");-
166 }
never executed: end of block
0
167-
168 success = 1;-
169 }
never executed: end of block
0
170-
171 return success;
never executed: return success;
0
172}-
173-
174/*-
175 * Check if hostname is numerical.-
176 * Returns -1 if hostname is numeric, 0 otherwise-
177 */-
178static int-
179is_numeric_hostname(const char *hostname)-
180{-
181 struct addrinfo hints, *ai;-
182-
183 /*-
184 * We shouldn't ever get a null host but if we do then log an error-
185 * and return -1 which stops DNS key fingerprint processing.-
186 */-
187 if (hostname == NULL) {
hostname == ((void *)0)Description
TRUEnever evaluated
FALSEnever evaluated
0
188 error("is_numeric_hostname called with NULL hostname");-
189 return -1;
never executed: return -1;
0
190 }-
191-
192 memset(&hints, 0, sizeof(hints));-
193 hints.ai_socktype = SOCK_DGRAM;-
194 hints.ai_flags = AI_NUMERICHOST;-
195-
196 if (getaddrinfo(hostname, NULL, &hints, &ai) == 0) {
getaddrinfo(ho...nts, &ai) == 0Description
TRUEnever evaluated
FALSEnever evaluated
0
197 freeaddrinfo(ai);-
198 return -1;
never executed: return -1;
0
199 }-
200-
201 return 0;
never executed: return 0;
0
202}-
203-
204/*-
205 * Verify the given hostname, address and host key using DNS.-
206 * Returns 0 if lookup succeeds, -1 otherwise-
207 */-
208int-
209verify_host_key_dns(const char *hostname, struct sockaddr *address,-
210 struct sshkey *hostkey, int *flags)-
211{-
212 u_int counter;-
213 int result;-
214 struct rrsetinfo *fingerprints = NULL;-
215-
216 u_int8_t hostkey_algorithm;-
217 u_int8_t hostkey_digest_type = SSHFP_HASH_RESERVED;-
218 u_char *hostkey_digest;-
219 size_t hostkey_digest_len;-
220-
221 u_int8_t dnskey_algorithm;-
222 u_int8_t dnskey_digest_type;-
223 u_char *dnskey_digest;-
224 size_t dnskey_digest_len;-
225-
226 *flags = 0;-
227-
228 debug3("verify_host_key_dns");-
229 if (hostkey == NULL)
hostkey == ((void *)0)Description
TRUEnever evaluated
FALSEnever evaluated
0
230 fatal("No key to look up!");
never executed: fatal("No key to look up!");
0
231-
232 if (is_numeric_hostname(hostname)) {
is_numeric_hostname(hostname)Description
TRUEnever evaluated
FALSEnever evaluated
0
233 debug("skipped DNS lookup for numerical hostname");-
234 return -1;
never executed: return -1;
0
235 }-
236-
237 result = getrrsetbyname(hostname, DNS_RDATACLASS_IN,-
238 DNS_RDATATYPE_SSHFP, 0, &fingerprints);-
239 if (result) {
resultDescription
TRUEnever evaluated
FALSEnever evaluated
0
240 verbose("DNS lookup error: %s", dns_result_totext(result));-
241 return -1;
never executed: return -1;
0
242 }-
243-
244 if (fingerprints->rri_flags & RRSET_VALIDATED) {
fingerprints->rri_flags & 1Description
TRUEnever evaluated
FALSEnever evaluated
0
245 *flags |= DNS_VERIFY_SECURE;-
246 debug("found %d secure fingerprints in DNS",-
247 fingerprints->rri_nrdatas);-
248 } else {
never executed: end of block
0
249 debug("found %d insecure fingerprints in DNS",-
250 fingerprints->rri_nrdatas);-
251 }
never executed: end of block
0
252-
253 /* Initialize default host key parameters */-
254 if (!dns_read_key(&hostkey_algorithm, &hostkey_digest_type,
!dns_read_key(..._len, hostkey)Description
TRUEnever evaluated
FALSEnever evaluated
0
255 &hostkey_digest, &hostkey_digest_len, hostkey)) {
!dns_read_key(..._len, hostkey)Description
TRUEnever evaluated
FALSEnever evaluated
0
256 error("Error calculating host key fingerprint.");-
257 freerrset(fingerprints);-
258 return -1;
never executed: return -1;
0
259 }-
260-
261 if (fingerprints->rri_nrdatas)
fingerprints->rri_nrdatasDescription
TRUEnever evaluated
FALSEnever evaluated
0
262 *flags |= DNS_VERIFY_FOUND;
never executed: *flags |= 0x00000001;
0
263-
264 for (counter = 0; counter < fingerprints->rri_nrdatas; counter++) {
counter < fing...s->rri_nrdatasDescription
TRUEnever evaluated
FALSEnever evaluated
0
265 /*-
266 * Extract the key from the answer. Ignore any badly-
267 * formatted fingerprints.-
268 */-
269 if (!dns_read_rdata(&dnskey_algorithm, &dnskey_digest_type,
!dns_read_rdat...r].rdi_length)Description
TRUEnever evaluated
FALSEnever evaluated
0
270 &dnskey_digest, &dnskey_digest_len,
!dns_read_rdat...r].rdi_length)Description
TRUEnever evaluated
FALSEnever evaluated
0
271 fingerprints->rri_rdatas[counter].rdi_data,
!dns_read_rdat...r].rdi_length)Description
TRUEnever evaluated
FALSEnever evaluated
0
272 fingerprints->rri_rdatas[counter].rdi_length)) {
!dns_read_rdat...r].rdi_length)Description
TRUEnever evaluated
FALSEnever evaluated
0
273 verbose("Error parsing fingerprint from DNS.");-
274 continue;
never executed: continue;
0
275 }-
276-
277 if (hostkey_digest_type != dnskey_digest_type) {
hostkey_digest...ey_digest_typeDescription
TRUEnever evaluated
FALSEnever evaluated
0
278 hostkey_digest_type = dnskey_digest_type;-
279 free(hostkey_digest);-
280-
281 /* Initialize host key parameters */-
282 if (!dns_read_key(&hostkey_algorithm,
!dns_read_key(..._len, hostkey)Description
TRUEnever evaluated
FALSEnever evaluated
0
283 &hostkey_digest_type, &hostkey_digest,
!dns_read_key(..._len, hostkey)Description
TRUEnever evaluated
FALSEnever evaluated
0
284 &hostkey_digest_len, hostkey)) {
!dns_read_key(..._len, hostkey)Description
TRUEnever evaluated
FALSEnever evaluated
0
285 error("Error calculating key fingerprint.");-
286 freerrset(fingerprints);-
287 return -1;
never executed: return -1;
0
288 }-
289 }
never executed: end of block
0
290-
291 /* Check if the current key is the same as the given key */-
292 if (hostkey_algorithm == dnskey_algorithm &&
hostkey_algori...skey_algorithmDescription
TRUEnever evaluated
FALSEnever evaluated
0
293 hostkey_digest_type == dnskey_digest_type) {
hostkey_digest...ey_digest_typeDescription
TRUEnever evaluated
FALSEnever evaluated
0
294 if (hostkey_digest_len == dnskey_digest_len &&
hostkey_digest...key_digest_lenDescription
TRUEnever evaluated
FALSEnever evaluated
0
295 timingsafe_bcmp(hostkey_digest, dnskey_digest,
timingsafe_bcm...gest_len) == 0Description
TRUEnever evaluated
FALSEnever evaluated
0
296 hostkey_digest_len) == 0)
timingsafe_bcm...gest_len) == 0Description
TRUEnever evaluated
FALSEnever evaluated
0
297 *flags |= DNS_VERIFY_MATCH;
never executed: *flags |= 0x00000002;
0
298 }
never executed: end of block
0
299 free(dnskey_digest);-
300 }
never executed: end of block
0
301-
302 free(hostkey_digest); /* from sshkey_fingerprint_raw() */-
303 freerrset(fingerprints);-
304-
305 if (*flags & DNS_VERIFY_FOUND)
*flags & 0x00000001Description
TRUEnever evaluated
FALSEnever evaluated
0
306 if (*flags & DNS_VERIFY_MATCH)
*flags & 0x00000002Description
TRUEnever evaluated
FALSEnever evaluated
0
307 debug("matching host key fingerprint found in DNS");
never executed: debug("matching host key fingerprint found in DNS");
0
308 else-
309 debug("mismatching host key fingerprint found in DNS");
never executed: debug("mismatching host key fingerprint found in DNS");
0
310 else-
311 debug("no host key fingerprint found in DNS");
never executed: debug("no host key fingerprint found in DNS");
0
312-
313 return 0;
never executed: return 0;
0
314}-
315-
316/*-
317 * Export the fingerprint of a key as a DNS resource record-
318 */-
319int-
320export_dns_rr(const char *hostname, struct sshkey *key, FILE *f, int generic)-
321{-
322 u_int8_t rdata_pubkey_algorithm = 0;-
323 u_int8_t rdata_digest_type = SSHFP_HASH_RESERVED;-
324 u_int8_t dtype;-
325 u_char *rdata_digest;-
326 size_t i, rdata_digest_len;-
327 int success = 0;-
328-
329 for (dtype = SSHFP_HASH_SHA1; dtype < SSHFP_HASH_MAX; dtype++) {
dtype < SSHFP_HASH_MAXDescription
TRUEnever evaluated
FALSEnever evaluated
0
330 rdata_digest_type = dtype;-
331 if (dns_read_key(&rdata_pubkey_algorithm, &rdata_digest_type,
dns_read_key(&...gest_len, key)Description
TRUEnever evaluated
FALSEnever evaluated
0
332 &rdata_digest, &rdata_digest_len, key)) {
dns_read_key(&...gest_len, key)Description
TRUEnever evaluated
FALSEnever evaluated
0
333 if (generic) {
genericDescription
TRUEnever evaluated
FALSEnever evaluated
0
334 fprintf(f, "%s IN TYPE%d \\# %zu %02x %02x ",-
335 hostname, DNS_RDATATYPE_SSHFP,-
336 2 + rdata_digest_len,-
337 rdata_pubkey_algorithm, rdata_digest_type);-
338 } else {
never executed: end of block
0
339 fprintf(f, "%s IN SSHFP %d %d ", hostname,-
340 rdata_pubkey_algorithm, rdata_digest_type);-
341 }
never executed: end of block
0
342 for (i = 0; i < rdata_digest_len; i++)
i < rdata_digest_lenDescription
TRUEnever evaluated
FALSEnever evaluated
0
343 fprintf(f, "%02x", rdata_digest[i]);
never executed: fprintf(f, "%02x", rdata_digest[i]);
0
344 fprintf(f, "\n");-
345 free(rdata_digest); /* from sshkey_fingerprint_raw() */-
346 success = 1;-
347 }
never executed: end of block
0
348 }
never executed: end of block
0
349-
350 /* No SSHFP record was generated at all */-
351 if (success == 0) {
success == 0Description
TRUEnever evaluated
FALSEnever evaluated
0
352 error("%s: unsupported algorithm and/or digest_type", __func__);-
353 }
never executed: end of block
0
354-
355 return success;
never executed: return success;
0
356}-
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