Annotation of src/usr.bin/ssh/dns.c, Revision 1.22
1.22 ! stevesk 1: /* $OpenBSD: dns.c,v 1.21 2006/07/22 20:48:23 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: */
27:
28: #include "includes.h"
1.20 stevesk 29:
30: #include <sys/types.h>
31: #include <sys/socket.h>
1.1 jakob 32:
33: #include <netdb.h>
1.22 ! stevesk 34: #include <stdio.h>
1.21 stevesk 35: #include <string.h>
1.1 jakob 36:
37: #include "xmalloc.h"
38: #include "key.h"
39: #include "dns.h"
40: #include "log.h"
41:
42: static const char *errset_text[] = {
43: "success", /* 0 ERRSET_SUCCESS */
44: "out of memory", /* 1 ERRSET_NOMEMORY */
45: "general failure", /* 2 ERRSET_FAIL */
46: "invalid parameter", /* 3 ERRSET_INVAL */
47: "name does not exist", /* 4 ERRSET_NONAME */
48: "data does not exist", /* 5 ERRSET_NODATA */
49: };
50:
51: static const char *
1.10 avsm 52: dns_result_totext(unsigned int res)
1.1 jakob 53: {
1.10 avsm 54: switch (res) {
1.1 jakob 55: case ERRSET_SUCCESS:
56: return errset_text[ERRSET_SUCCESS];
57: case ERRSET_NOMEMORY:
58: return errset_text[ERRSET_NOMEMORY];
59: case ERRSET_FAIL:
60: return errset_text[ERRSET_FAIL];
61: case ERRSET_INVAL:
62: return errset_text[ERRSET_INVAL];
63: case ERRSET_NONAME:
64: return errset_text[ERRSET_NONAME];
65: case ERRSET_NODATA:
66: return errset_text[ERRSET_NODATA];
67: default:
68: return "unknown error";
69: }
70: }
71:
72: /*
73: * Read SSHFP parameters from key buffer.
74: */
75: static int
76: dns_read_key(u_int8_t *algorithm, u_int8_t *digest_type,
1.8 jakob 77: u_char **digest, u_int *digest_len, const Key *key)
1.1 jakob 78: {
79: int success = 0;
80:
81: switch (key->type) {
82: case KEY_RSA:
1.3 jakob 83: *algorithm = SSHFP_KEY_RSA;
1.1 jakob 84: break;
85: case KEY_DSA:
1.3 jakob 86: *algorithm = SSHFP_KEY_DSA;
1.1 jakob 87: break;
88: default:
1.14 stevesk 89: *algorithm = SSHFP_KEY_RESERVED; /* 0 */
1.1 jakob 90: }
91:
92: if (*algorithm) {
1.3 jakob 93: *digest_type = SSHFP_HASH_SHA1;
1.1 jakob 94: *digest = key_fingerprint_raw(key, SSH_FP_SHA1, digest_len);
1.14 stevesk 95: if (*digest == NULL)
96: fatal("dns_read_key: null from key_fingerprint_raw()");
1.1 jakob 97: success = 1;
98: } else {
1.3 jakob 99: *digest_type = SSHFP_HASH_RESERVED;
1.1 jakob 100: *digest = NULL;
101: *digest_len = 0;
102: success = 0;
103: }
104:
105: return success;
106: }
107:
108: /*
109: * Read SSHFP parameters from rdata buffer.
110: */
111: static int
112: dns_read_rdata(u_int8_t *algorithm, u_int8_t *digest_type,
113: u_char **digest, u_int *digest_len, u_char *rdata, int rdata_len)
114: {
115: int success = 0;
116:
1.3 jakob 117: *algorithm = SSHFP_KEY_RESERVED;
118: *digest_type = SSHFP_HASH_RESERVED;
1.1 jakob 119:
120: if (rdata_len >= 2) {
121: *algorithm = rdata[0];
122: *digest_type = rdata[1];
123: *digest_len = rdata_len - 2;
124:
125: if (*digest_len > 0) {
126: *digest = (u_char *) xmalloc(*digest_len);
127: memcpy(*digest, rdata + 2, *digest_len);
128: } else {
1.18 deraadt 129: *digest = (u_char *)xstrdup("");
1.1 jakob 130: }
131:
132: success = 1;
133: }
134:
135: return success;
136: }
137:
1.11 jakob 138: /*
139: * Check if hostname is numerical.
140: * Returns -1 if hostname is numeric, 0 otherwise
141: */
142: static int
143: is_numeric_hostname(const char *hostname)
144: {
145: struct addrinfo hints, *ai;
146:
147: memset(&hints, 0, sizeof(hints));
148: hints.ai_socktype = SOCK_DGRAM;
149: hints.ai_flags = AI_NUMERICHOST;
150:
151: if (getaddrinfo(hostname, "0", &hints, &ai) == 0) {
152: freeaddrinfo(ai);
153: return -1;
154: }
155:
156: return 0;
157: }
1.1 jakob 158:
159: /*
160: * Verify the given hostname, address and host key using DNS.
1.9 djm 161: * Returns 0 if lookup succeeds, -1 otherwise
1.1 jakob 162: */
163: int
164: verify_host_key_dns(const char *hostname, struct sockaddr *address,
1.8 jakob 165: const Key *hostkey, int *flags)
1.1 jakob 166: {
1.12 djm 167: u_int counter;
1.1 jakob 168: int result;
1.4 jakob 169: struct rrsetinfo *fingerprints = NULL;
1.1 jakob 170:
171: u_int8_t hostkey_algorithm;
172: u_int8_t hostkey_digest_type;
173: u_char *hostkey_digest;
174: u_int hostkey_digest_len;
175:
176: u_int8_t dnskey_algorithm;
177: u_int8_t dnskey_digest_type;
178: u_char *dnskey_digest;
179: u_int dnskey_digest_len;
180:
1.8 jakob 181: *flags = 0;
1.1 jakob 182:
1.16 stevesk 183: debug3("verify_host_key_dns");
1.1 jakob 184: if (hostkey == NULL)
185: fatal("No key to look up!");
1.11 jakob 186:
187: if (is_numeric_hostname(hostname)) {
188: debug("skipped DNS lookup for numerical hostname");
189: return -1;
190: }
1.1 jakob 191:
192: result = getrrsetbyname(hostname, DNS_RDATACLASS_IN,
1.4 jakob 193: DNS_RDATATYPE_SSHFP, 0, &fingerprints);
1.1 jakob 194: if (result) {
195: verbose("DNS lookup error: %s", dns_result_totext(result));
1.8 jakob 196: return -1;
1.1 jakob 197: }
198:
1.8 jakob 199: if (fingerprints->rri_flags & RRSET_VALIDATED) {
200: *flags |= DNS_VERIFY_SECURE;
201: debug("found %d secure fingerprints in DNS",
202: fingerprints->rri_nrdatas);
203: } else {
204: debug("found %d insecure fingerprints in DNS",
205: fingerprints->rri_nrdatas);
1.1 jakob 206: }
207:
208: /* Initialize host key parameters */
209: if (!dns_read_key(&hostkey_algorithm, &hostkey_digest_type,
210: &hostkey_digest, &hostkey_digest_len, hostkey)) {
211: error("Error calculating host key fingerprint.");
1.5 jakob 212: freerrset(fingerprints);
1.8 jakob 213: return -1;
1.1 jakob 214: }
215:
1.8 jakob 216: if (fingerprints->rri_nrdatas)
217: *flags |= DNS_VERIFY_FOUND;
218:
1.13 stevesk 219: for (counter = 0; counter < fingerprints->rri_nrdatas; counter++) {
1.1 jakob 220: /*
221: * Extract the key from the answer. Ignore any badly
1.4 jakob 222: * formatted fingerprints.
1.1 jakob 223: */
224: if (!dns_read_rdata(&dnskey_algorithm, &dnskey_digest_type,
225: &dnskey_digest, &dnskey_digest_len,
1.4 jakob 226: fingerprints->rri_rdatas[counter].rdi_data,
227: fingerprints->rri_rdatas[counter].rdi_length)) {
1.1 jakob 228: verbose("Error parsing fingerprint from DNS.");
229: continue;
230: }
231:
232: /* Check if the current key is the same as the given key */
233: if (hostkey_algorithm == dnskey_algorithm &&
234: hostkey_digest_type == dnskey_digest_type) {
235:
236: if (hostkey_digest_len == dnskey_digest_len &&
237: memcmp(hostkey_digest, dnskey_digest,
238: hostkey_digest_len) == 0) {
239:
1.8 jakob 240: *flags |= DNS_VERIFY_MATCH;
1.1 jakob 241: }
242: }
1.14 stevesk 243: xfree(dnskey_digest);
1.1 jakob 244: }
245:
1.14 stevesk 246: xfree(hostkey_digest); /* from key_fingerprint_raw() */
1.4 jakob 247: freerrset(fingerprints);
1.1 jakob 248:
1.8 jakob 249: if (*flags & DNS_VERIFY_FOUND)
250: if (*flags & DNS_VERIFY_MATCH)
251: debug("matching host key fingerprint found in DNS");
252: else
253: debug("mismatching host key fingerprint found in DNS");
254: else
255: debug("no host key fingerprint found in DNS");
1.1 jakob 256:
1.8 jakob 257: return 0;
1.1 jakob 258: }
259:
260: /*
261: * Export the fingerprint of a key as a DNS resource record
262: */
263: int
1.8 jakob 264: export_dns_rr(const char *hostname, const Key *key, FILE *f, int generic)
1.1 jakob 265: {
266: u_int8_t rdata_pubkey_algorithm = 0;
1.3 jakob 267: u_int8_t rdata_digest_type = SSHFP_HASH_SHA1;
1.1 jakob 268: u_char *rdata_digest;
269: u_int rdata_digest_len;
270:
1.12 djm 271: u_int i;
1.1 jakob 272: int success = 0;
273:
274: if (dns_read_key(&rdata_pubkey_algorithm, &rdata_digest_type,
1.16 stevesk 275: &rdata_digest, &rdata_digest_len, key)) {
1.1 jakob 276:
277: if (generic)
278: fprintf(f, "%s IN TYPE%d \\# %d %02x %02x ", hostname,
279: DNS_RDATATYPE_SSHFP, 2 + rdata_digest_len,
280: rdata_pubkey_algorithm, rdata_digest_type);
281: else
282: fprintf(f, "%s IN SSHFP %d %d ", hostname,
283: rdata_pubkey_algorithm, rdata_digest_type);
284:
285: for (i = 0; i < rdata_digest_len; i++)
286: fprintf(f, "%02x", rdata_digest[i]);
287: fprintf(f, "\n");
1.14 stevesk 288: xfree(rdata_digest); /* from key_fingerprint_raw() */
1.1 jakob 289: success = 1;
290: } else {
1.16 stevesk 291: error("export_dns_rr: unsupported algorithm");
1.1 jakob 292: }
293:
294: return success;
295: }
![[BACK]](/icons/back.gif){kind=icon}
Return to dns.c CVS log ![[TXT]](/icons/text.gif){kind=icon}
![[DIR]](/icons/dir.gif){kind=icon}
Up to [local] / src / usr.bin / ssh