Annotation of src/usr.bin/ssh/dns.c, Revision 1.10.4.1
1.10.4.1! brad 1: /* $OpenBSD: dns.c,v 1.12 2005/06/17 02:44:32 djm Exp $ */
1.1 jakob 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:
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;
1.10.4.1! brad 46: RCSID("$OpenBSD: dns.c,v 1.12 2005/06/17 02:44:32 djm Exp $");
1.1 jakob 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 *
1.10 avsm 59: dns_result_totext(unsigned int res)
1.1 jakob 60: {
1.10 avsm 61: switch (res) {
1.1 jakob 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,
1.8 jakob 86: u_char **digest, u_int *digest_len, const Key *key)
1.1 jakob 87: {
88: int success = 0;
89:
90: switch (key->type) {
91: case KEY_RSA:
1.3 jakob 92: *algorithm = SSHFP_KEY_RSA;
1.1 jakob 93: break;
94: case KEY_DSA:
1.3 jakob 95: *algorithm = SSHFP_KEY_DSA;
1.1 jakob 96: break;
97: default:
1.3 jakob 98: *algorithm = SSHFP_KEY_RESERVED;
1.1 jakob 99: }
100:
101: if (*algorithm) {
1.3 jakob 102: *digest_type = SSHFP_HASH_SHA1;
1.1 jakob 103: *digest = key_fingerprint_raw(key, SSH_FP_SHA1, digest_len);
104: success = 1;
105: } else {
1.3 jakob 106: *digest_type = SSHFP_HASH_RESERVED;
1.1 jakob 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:
1.3 jakob 124: *algorithm = SSHFP_KEY_RESERVED;
125: *digest_type = SSHFP_HASH_RESERVED;
1.1 jakob 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:
1.10.4.1! brad 145: /*
! 146: * Check if hostname is numerical.
! 147: * Returns -1 if hostname is numeric, 0 otherwise
! 148: */
! 149: static int
! 150: is_numeric_hostname(const char *hostname)
! 151: {
! 152: struct addrinfo hints, *ai;
! 153:
! 154: memset(&hints, 0, sizeof(hints));
! 155: hints.ai_socktype = SOCK_DGRAM;
! 156: hints.ai_flags = AI_NUMERICHOST;
! 157:
! 158: if (getaddrinfo(hostname, "0", &hints, &ai) == 0) {
! 159: freeaddrinfo(ai);
! 160: return -1;
! 161: }
! 162:
! 163: return 0;
! 164: }
1.1 jakob 165:
166: /*
167: * Verify the given hostname, address and host key using DNS.
1.9 djm 168: * Returns 0 if lookup succeeds, -1 otherwise
1.1 jakob 169: */
170: int
171: verify_host_key_dns(const char *hostname, struct sockaddr *address,
1.8 jakob 172: const Key *hostkey, int *flags)
1.1 jakob 173: {
1.10.4.1! brad 174: u_int counter;
1.1 jakob 175: int result;
1.4 jakob 176: struct rrsetinfo *fingerprints = NULL;
1.1 jakob 177:
178: u_int8_t hostkey_algorithm;
179: u_int8_t hostkey_digest_type;
180: u_char *hostkey_digest;
181: u_int hostkey_digest_len;
182:
183: u_int8_t dnskey_algorithm;
184: u_int8_t dnskey_digest_type;
185: u_char *dnskey_digest;
186: u_int dnskey_digest_len;
187:
1.8 jakob 188: *flags = 0;
1.1 jakob 189:
190: debug3("verify_hostkey_dns");
191: if (hostkey == NULL)
192: fatal("No key to look up!");
193:
1.10.4.1! brad 194: if (is_numeric_hostname(hostname)) {
! 195: debug("skipped DNS lookup for numerical hostname");
! 196: return -1;
! 197: }
! 198:
1.1 jakob 199: result = getrrsetbyname(hostname, DNS_RDATACLASS_IN,
1.4 jakob 200: DNS_RDATATYPE_SSHFP, 0, &fingerprints);
1.1 jakob 201: if (result) {
202: verbose("DNS lookup error: %s", dns_result_totext(result));
1.8 jakob 203: return -1;
1.1 jakob 204: }
205:
1.8 jakob 206: if (fingerprints->rri_flags & RRSET_VALIDATED) {
207: *flags |= DNS_VERIFY_SECURE;
208: debug("found %d secure fingerprints in DNS",
209: fingerprints->rri_nrdatas);
210: } else {
211: debug("found %d insecure fingerprints in DNS",
212: fingerprints->rri_nrdatas);
1.1 jakob 213: }
214:
215: /* Initialize host key parameters */
216: if (!dns_read_key(&hostkey_algorithm, &hostkey_digest_type,
217: &hostkey_digest, &hostkey_digest_len, hostkey)) {
218: error("Error calculating host key fingerprint.");
1.5 jakob 219: freerrset(fingerprints);
1.8 jakob 220: return -1;
1.1 jakob 221: }
222:
1.8 jakob 223: if (fingerprints->rri_nrdatas)
224: *flags |= DNS_VERIFY_FOUND;
225:
1.4 jakob 226: for (counter = 0 ; counter < fingerprints->rri_nrdatas ; counter++) {
1.1 jakob 227: /*
228: * Extract the key from the answer. Ignore any badly
1.4 jakob 229: * formatted fingerprints.
1.1 jakob 230: */
231: if (!dns_read_rdata(&dnskey_algorithm, &dnskey_digest_type,
232: &dnskey_digest, &dnskey_digest_len,
1.4 jakob 233: fingerprints->rri_rdatas[counter].rdi_data,
234: fingerprints->rri_rdatas[counter].rdi_length)) {
1.1 jakob 235: verbose("Error parsing fingerprint from DNS.");
236: continue;
237: }
238:
239: /* Check if the current key is the same as the given key */
240: if (hostkey_algorithm == dnskey_algorithm &&
241: hostkey_digest_type == dnskey_digest_type) {
242:
243: if (hostkey_digest_len == dnskey_digest_len &&
244: memcmp(hostkey_digest, dnskey_digest,
245: hostkey_digest_len) == 0) {
246:
1.8 jakob 247: *flags |= DNS_VERIFY_MATCH;
1.1 jakob 248: }
249: }
250: }
251:
1.4 jakob 252: freerrset(fingerprints);
1.1 jakob 253:
1.8 jakob 254: if (*flags & DNS_VERIFY_FOUND)
255: if (*flags & DNS_VERIFY_MATCH)
256: debug("matching host key fingerprint found in DNS");
257: else
258: debug("mismatching host key fingerprint found in DNS");
259: else
260: debug("no host key fingerprint found in DNS");
1.1 jakob 261:
1.8 jakob 262: return 0;
1.1 jakob 263: }
264:
265:
266: /*
267: * Export the fingerprint of a key as a DNS resource record
268: */
269: int
1.8 jakob 270: export_dns_rr(const char *hostname, const Key *key, FILE *f, int generic)
1.1 jakob 271: {
272: u_int8_t rdata_pubkey_algorithm = 0;
1.3 jakob 273: u_int8_t rdata_digest_type = SSHFP_HASH_SHA1;
1.1 jakob 274: u_char *rdata_digest;
275: u_int rdata_digest_len;
276:
1.10.4.1! brad 277: u_int i;
1.1 jakob 278: int success = 0;
279:
280: if (dns_read_key(&rdata_pubkey_algorithm, &rdata_digest_type,
281: &rdata_digest, &rdata_digest_len, key)) {
282:
283: if (generic)
284: fprintf(f, "%s IN TYPE%d \\# %d %02x %02x ", hostname,
285: DNS_RDATATYPE_SSHFP, 2 + rdata_digest_len,
286: rdata_pubkey_algorithm, rdata_digest_type);
287: else
288: fprintf(f, "%s IN SSHFP %d %d ", hostname,
289: rdata_pubkey_algorithm, rdata_digest_type);
290:
291: for (i = 0; i < rdata_digest_len; i++)
292: fprintf(f, "%02x", rdata_digest[i]);
293: fprintf(f, "\n");
294: success = 1;
295: } else {
296: error("dns_export_rr: unsupported algorithm");
297: }
298:
299: return success;
300: }
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