Annotation of src/usr.bin/ssh/dns.c, Revision 1.8
1.8 ! jakob 1: /* $OpenBSD: dns.c,v 1.7 2003/10/14 19:42:10 jakob 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;
1.8 ! jakob 46: RCSID("$OpenBSD: dns.c,v 1.7 2003/10/14 19:42:10 jakob 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 *
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,
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:
145:
146: /*
147: * Verify the given hostname, address and host key using DNS.
1.8 ! jakob 148: * Returns 0 if lookup succeeds, -1 otherwise
1.1 jakob 149: */
150: int
151: verify_host_key_dns(const char *hostname, struct sockaddr *address,
1.8 ! jakob 152: const Key *hostkey, int *flags)
1.1 jakob 153: {
154: int counter;
155: int result;
1.4 jakob 156: struct rrsetinfo *fingerprints = NULL;
1.1 jakob 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:
1.8 ! jakob 168: *flags = 0;
1.1 jakob 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,
1.4 jakob 175: DNS_RDATATYPE_SSHFP, 0, &fingerprints);
1.1 jakob 176: if (result) {
177: verbose("DNS lookup error: %s", dns_result_totext(result));
1.8 ! jakob 178: return -1;
1.1 jakob 179: }
180:
1.8 ! jakob 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);
1.1 jakob 188: }
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.");
1.5 jakob 194: freerrset(fingerprints);
1.8 ! jakob 195: return -1;
1.1 jakob 196: }
197:
1.8 ! jakob 198: if (fingerprints->rri_nrdatas)
! 199: *flags |= DNS_VERIFY_FOUND;
! 200:
1.4 jakob 201: for (counter = 0 ; counter < fingerprints->rri_nrdatas ; counter++) {
1.1 jakob 202: /*
203: * Extract the key from the answer. Ignore any badly
1.4 jakob 204: * formatted fingerprints.
1.1 jakob 205: */
206: if (!dns_read_rdata(&dnskey_algorithm, &dnskey_digest_type,
207: &dnskey_digest, &dnskey_digest_len,
1.4 jakob 208: fingerprints->rri_rdatas[counter].rdi_data,
209: fingerprints->rri_rdatas[counter].rdi_length)) {
1.1 jakob 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:
1.8 ! jakob 222: *flags |= DNS_VERIFY_MATCH;
1.1 jakob 223: }
224: }
225: }
226:
1.4 jakob 227: freerrset(fingerprints);
1.1 jakob 228:
1.8 ! jakob 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");
1.1 jakob 236:
1.8 ! jakob 237: return 0;
1.1 jakob 238: }
239:
240:
241: /*
242: * Export the fingerprint of a key as a DNS resource record
243: */
244: int
1.8 ! jakob 245: export_dns_rr(const char *hostname, const Key *key, FILE *f, int generic)
1.1 jakob 246: {
247: u_int8_t rdata_pubkey_algorithm = 0;
1.3 jakob 248: u_int8_t rdata_digest_type = SSHFP_HASH_SHA1;
1.1 jakob 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: }
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