Annotation of src/usr.bin/ssh/dns.c, Revision 1.25
1.25 ! dtucker 1: /* $OpenBSD: dns.c,v 1.24 2007/01/03 03:01:40 stevesk 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: */
1.20 stevesk 27:
28: #include <sys/types.h>
29: #include <sys/socket.h>
1.1 jakob 30:
31: #include <netdb.h>
1.22 stevesk 32: #include <stdio.h>
1.21 stevesk 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 {
1.18 deraadt 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:
1.25 ! dtucker 145: /*
! 146: * We shouldn't ever get a null host but if we do then log an error
! 147: * and return -1 which stops DNS key fingerprint processing.
! 148: */
! 149: if (hostname == NULL) {
! 150: error("is_numeric_hostname called with NULL hostname");
! 151: return -1;
! 152: }
! 153:
1.11 jakob 154: memset(&hints, 0, sizeof(hints));
155: hints.ai_socktype = SOCK_DGRAM;
156: hints.ai_flags = AI_NUMERICHOST;
157:
1.25 ! dtucker 158: if (getaddrinfo(hostname, NULL, &hints, &ai) == 0) {
1.11 jakob 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: {
1.12 djm 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:
1.16 stevesk 190: debug3("verify_host_key_dns");
1.1 jakob 191: if (hostkey == NULL)
192: fatal("No key to look up!");
1.11 jakob 193:
194: if (is_numeric_hostname(hostname)) {
195: debug("skipped DNS lookup for numerical hostname");
196: return -1;
197: }
1.1 jakob 198:
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:
1.24 stevesk 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: }
1.14 stevesk 250: xfree(dnskey_digest);
1.1 jakob 251: }
252:
1.14 stevesk 253: xfree(hostkey_digest); /* from key_fingerprint_raw() */
1.4 jakob 254: freerrset(fingerprints);
1.1 jakob 255:
1.8 jakob 256: if (*flags & DNS_VERIFY_FOUND)
257: if (*flags & DNS_VERIFY_MATCH)
258: debug("matching host key fingerprint found in DNS");
259: else
260: debug("mismatching host key fingerprint found in DNS");
261: else
262: debug("no host key fingerprint found in DNS");
1.1 jakob 263:
1.8 jakob 264: return 0;
1.1 jakob 265: }
266:
267: /*
268: * Export the fingerprint of a key as a DNS resource record
269: */
270: int
1.8 jakob 271: export_dns_rr(const char *hostname, const Key *key, FILE *f, int generic)
1.1 jakob 272: {
273: u_int8_t rdata_pubkey_algorithm = 0;
1.3 jakob 274: u_int8_t rdata_digest_type = SSHFP_HASH_SHA1;
1.1 jakob 275: u_char *rdata_digest;
276: u_int rdata_digest_len;
277:
1.12 djm 278: u_int i;
1.1 jakob 279: int success = 0;
280:
281: if (dns_read_key(&rdata_pubkey_algorithm, &rdata_digest_type,
1.16 stevesk 282: &rdata_digest, &rdata_digest_len, key)) {
1.1 jakob 283:
284: if (generic)
285: fprintf(f, "%s IN TYPE%d \\# %d %02x %02x ", hostname,
286: DNS_RDATATYPE_SSHFP, 2 + rdata_digest_len,
287: rdata_pubkey_algorithm, rdata_digest_type);
288: else
289: fprintf(f, "%s IN SSHFP %d %d ", hostname,
290: rdata_pubkey_algorithm, rdata_digest_type);
291:
292: for (i = 0; i < rdata_digest_len; i++)
293: fprintf(f, "%02x", rdata_digest[i]);
294: fprintf(f, "\n");
1.14 stevesk 295: xfree(rdata_digest); /* from key_fingerprint_raw() */
1.1 jakob 296: success = 1;
297: } else {
1.16 stevesk 298: error("export_dns_rr: unsupported algorithm");
1.1 jakob 299: }
300:
301: return success;
302: }