Annotation of src/usr.bin/ssh/dns.c, Revision 1.16.2.1
1.16.2.1! brad 1: /* $OpenBSD: dns.c,v 1.23 2006/08/03 03:34:42 deraadt 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:
1.16.2.1! brad 28: #include <sys/types.h>
! 29: #include <sys/socket.h>
1.1 jakob 30:
31: #include <netdb.h>
1.16.2.1! brad 32: #include <stdio.h>
! 33: #include <string.h>
1.1 jakob 34:
35: #include "xmalloc.h"
36: #include "key.h"
37: #include "dns.h"
38: #include "log.h"
39:
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 *
1.10 avsm 50: dns_result_totext(unsigned int res)
1.1 jakob 51: {
1.10 avsm 52: switch (res) {
1.1 jakob 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: }
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,
1.8 jakob 75: u_char **digest, u_int *digest_len, const Key *key)
1.1 jakob 76: {
77: int success = 0;
78:
79: switch (key->type) {
80: case KEY_RSA:
1.3 jakob 81: *algorithm = SSHFP_KEY_RSA;
1.1 jakob 82: break;
83: case KEY_DSA:
1.3 jakob 84: *algorithm = SSHFP_KEY_DSA;
1.1 jakob 85: break;
86: default:
1.14 stevesk 87: *algorithm = SSHFP_KEY_RESERVED; /* 0 */
1.1 jakob 88: }
89:
90: if (*algorithm) {
1.3 jakob 91: *digest_type = SSHFP_HASH_SHA1;
1.1 jakob 92: *digest = key_fingerprint_raw(key, SSH_FP_SHA1, digest_len);
1.14 stevesk 93: if (*digest == NULL)
94: fatal("dns_read_key: null from key_fingerprint_raw()");
1.1 jakob 95: success = 1;
96: } else {
1.3 jakob 97: *digest_type = SSHFP_HASH_RESERVED;
1.1 jakob 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:
1.3 jakob 115: *algorithm = SSHFP_KEY_RESERVED;
116: *digest_type = SSHFP_HASH_RESERVED;
1.1 jakob 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 {
1.16.2.1! brad 127: *digest = (u_char *)xstrdup("");
1.1 jakob 128: }
129:
130: success = 1;
131: }
132:
133: return success;
134: }
135:
1.11 jakob 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: }
1.1 jakob 156:
157: /*
158: * Verify the given hostname, address and host key using DNS.
1.9 djm 159: * Returns 0 if lookup succeeds, -1 otherwise
1.1 jakob 160: */
161: int
162: verify_host_key_dns(const char *hostname, struct sockaddr *address,
1.8 jakob 163: const Key *hostkey, int *flags)
1.1 jakob 164: {
1.12 djm 165: u_int counter;
1.1 jakob 166: int result;
1.4 jakob 167: struct rrsetinfo *fingerprints = NULL;
1.1 jakob 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:
1.8 jakob 179: *flags = 0;
1.1 jakob 180:
1.16 stevesk 181: debug3("verify_host_key_dns");
1.1 jakob 182: if (hostkey == NULL)
183: fatal("No key to look up!");
1.11 jakob 184:
185: if (is_numeric_hostname(hostname)) {
186: debug("skipped DNS lookup for numerical hostname");
187: return -1;
188: }
1.1 jakob 189:
190: result = getrrsetbyname(hostname, DNS_RDATACLASS_IN,
1.4 jakob 191: DNS_RDATATYPE_SSHFP, 0, &fingerprints);
1.1 jakob 192: if (result) {
193: verbose("DNS lookup error: %s", dns_result_totext(result));
1.8 jakob 194: return -1;
1.1 jakob 195: }
196:
1.8 jakob 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);
1.1 jakob 204: }
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.");
1.5 jakob 210: freerrset(fingerprints);
1.8 jakob 211: return -1;
1.1 jakob 212: }
213:
1.8 jakob 214: if (fingerprints->rri_nrdatas)
215: *flags |= DNS_VERIFY_FOUND;
216:
1.13 stevesk 217: for (counter = 0; counter < fingerprints->rri_nrdatas; counter++) {
1.1 jakob 218: /*
219: * Extract the key from the answer. Ignore any badly
1.4 jakob 220: * formatted fingerprints.
1.1 jakob 221: */
222: if (!dns_read_rdata(&dnskey_algorithm, &dnskey_digest_type,
223: &dnskey_digest, &dnskey_digest_len,
1.4 jakob 224: fingerprints->rri_rdatas[counter].rdi_data,
225: fingerprints->rri_rdatas[counter].rdi_length)) {
1.1 jakob 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:
1.8 jakob 238: *flags |= DNS_VERIFY_MATCH;
1.1 jakob 239: }
240: }
1.14 stevesk 241: xfree(dnskey_digest);
1.1 jakob 242: }
243:
1.14 stevesk 244: xfree(hostkey_digest); /* from key_fingerprint_raw() */
1.4 jakob 245: freerrset(fingerprints);
1.1 jakob 246:
1.8 jakob 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");
1.1 jakob 254:
1.8 jakob 255: return 0;
1.1 jakob 256: }
257:
258: /*
259: * Export the fingerprint of a key as a DNS resource record
260: */
261: int
1.8 jakob 262: export_dns_rr(const char *hostname, const Key *key, FILE *f, int generic)
1.1 jakob 263: {
264: u_int8_t rdata_pubkey_algorithm = 0;
1.3 jakob 265: u_int8_t rdata_digest_type = SSHFP_HASH_SHA1;
1.1 jakob 266: u_char *rdata_digest;
267: u_int rdata_digest_len;
268:
1.12 djm 269: u_int i;
1.1 jakob 270: int success = 0;
271:
272: if (dns_read_key(&rdata_pubkey_algorithm, &rdata_digest_type,
1.16 stevesk 273: &rdata_digest, &rdata_digest_len, key)) {
1.1 jakob 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");
1.14 stevesk 286: xfree(rdata_digest); /* from key_fingerprint_raw() */
1.1 jakob 287: success = 1;
288: } else {
1.16 stevesk 289: error("export_dns_rr: unsupported algorithm");
1.1 jakob 290: }
291:
292: return success;
293: }
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