Annotation of src/usr.bin/ssh/dns.c, Revision 1.1
1.1 ! jakob 1: /* $OpenBSD: dns.c,v 1.1 2003/05/12 16:40:33 jakob Exp $ */
! 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: * 3. The name of the authors may not be used to endorse or promote products
! 16: * derived from this software without specific prior written permission.
! 17: *
! 18: * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
! 19: * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
! 20: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
! 21: * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
! 22: * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
! 23: * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
! 24: * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
! 25: * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
! 26: * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
! 27: * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
! 28: */
! 29:
! 30:
! 31: #include "includes.h"
! 32:
! 33: #ifdef DNS
! 34: #include <openssl/bn.h>
! 35: #ifdef LWRES
! 36: #include <lwres/netdb.h>
! 37: #include <dns/result.h>
! 38: #else /* LWRES */
! 39: #include <netdb.h>
! 40: #endif /* LWRES */
! 41:
! 42: #include "xmalloc.h"
! 43: #include "key.h"
! 44: #include "dns.h"
! 45: #include "log.h"
! 46: #include "uuencode.h"
! 47:
! 48: extern char *__progname;
! 49: RCSID("$OpenBSD: dns.c,v 1.1 2003/05/12 16:40:33 jakob Exp $");
! 50:
! 51: #ifndef LWRES
! 52: static const char *errset_text[] = {
! 53: "success", /* 0 ERRSET_SUCCESS */
! 54: "out of memory", /* 1 ERRSET_NOMEMORY */
! 55: "general failure", /* 2 ERRSET_FAIL */
! 56: "invalid parameter", /* 3 ERRSET_INVAL */
! 57: "name does not exist", /* 4 ERRSET_NONAME */
! 58: "data does not exist", /* 5 ERRSET_NODATA */
! 59: };
! 60:
! 61: static const char *
! 62: dns_result_totext(unsigned int error)
! 63: {
! 64: switch (error) {
! 65: case ERRSET_SUCCESS:
! 66: return errset_text[ERRSET_SUCCESS];
! 67: case ERRSET_NOMEMORY:
! 68: return errset_text[ERRSET_NOMEMORY];
! 69: case ERRSET_FAIL:
! 70: return errset_text[ERRSET_FAIL];
! 71: case ERRSET_INVAL:
! 72: return errset_text[ERRSET_INVAL];
! 73: case ERRSET_NONAME:
! 74: return errset_text[ERRSET_NONAME];
! 75: case ERRSET_NODATA:
! 76: return errset_text[ERRSET_NODATA];
! 77: default:
! 78: return "unknown error";
! 79: }
! 80: }
! 81: #endif /* LWRES */
! 82:
! 83:
! 84: /*
! 85: * Read SSHFP parameters from key buffer.
! 86: */
! 87: static int
! 88: dns_read_key(u_int8_t *algorithm, u_int8_t *digest_type,
! 89: u_char **digest, u_int *digest_len, Key *key)
! 90: {
! 91: int success = 0;
! 92:
! 93: switch (key->type) {
! 94: case KEY_RSA:
! 95: *algorithm = DNS_KEY_RSA;
! 96: break;
! 97: case KEY_DSA:
! 98: *algorithm = DNS_KEY_DSA;
! 99: break;
! 100: default:
! 101: *algorithm = DNS_KEY_RESERVED;
! 102: }
! 103:
! 104: if (*algorithm) {
! 105: *digest_type = DNS_HASH_SHA1;
! 106: *digest = key_fingerprint_raw(key, SSH_FP_SHA1, digest_len);
! 107: success = 1;
! 108: } else {
! 109: *digest_type = DNS_HASH_RESERVED;
! 110: *digest = NULL;
! 111: *digest_len = 0;
! 112: success = 0;
! 113: }
! 114:
! 115: return success;
! 116: }
! 117:
! 118: /*
! 119: * Read SSHFP parameters from rdata buffer.
! 120: */
! 121: static int
! 122: dns_read_rdata(u_int8_t *algorithm, u_int8_t *digest_type,
! 123: u_char **digest, u_int *digest_len, u_char *rdata, int rdata_len)
! 124: {
! 125: int success = 0;
! 126:
! 127: *algorithm = DNS_KEY_RESERVED;
! 128: *digest_type = DNS_HASH_RESERVED;
! 129:
! 130: if (rdata_len >= 2) {
! 131: *algorithm = rdata[0];
! 132: *digest_type = rdata[1];
! 133: *digest_len = rdata_len - 2;
! 134:
! 135: if (*digest_len > 0) {
! 136: *digest = (u_char *) xmalloc(*digest_len);
! 137: memcpy(*digest, rdata + 2, *digest_len);
! 138: } else {
! 139: *digest = NULL;
! 140: }
! 141:
! 142: success = 1;
! 143: }
! 144:
! 145: return success;
! 146: }
! 147:
! 148:
! 149: /*
! 150: * Verify the given hostname, address and host key using DNS.
! 151: * Returns 0 if key verifies or -1 if key does NOT verify
! 152: */
! 153: int
! 154: verify_host_key_dns(const char *hostname, struct sockaddr *address,
! 155: Key *hostkey)
! 156: {
! 157: int counter;
! 158: int result;
! 159: struct rrsetinfo *keys = NULL;
! 160: int failures = 0;
! 161:
! 162: u_int8_t hostkey_algorithm;
! 163: u_int8_t hostkey_digest_type;
! 164: u_char *hostkey_digest;
! 165: u_int hostkey_digest_len;
! 166:
! 167: u_int8_t dnskey_algorithm;
! 168: u_int8_t dnskey_digest_type;
! 169: u_char *dnskey_digest;
! 170: u_int dnskey_digest_len;
! 171:
! 172:
! 173: debug3("verify_hostkey_dns");
! 174: if (hostkey == NULL)
! 175: fatal("No key to look up!");
! 176:
! 177: result = getrrsetbyname(hostname, DNS_RDATACLASS_IN,
! 178: DNS_RDATATYPE_SSHFP, 0, &keys);
! 179: if (result) {
! 180: verbose("DNS lookup error: %s", dns_result_totext(result));
! 181: return DNS_VERIFY_ERROR;
! 182: }
! 183:
! 184: #ifdef DNSSEC
! 185: /* Only accept validated answers */
! 186: if (!keys->rri_flags & RRSET_VALIDATED) {
! 187: error("Ignored unvalidated fingerprint from DNS.");
! 188: return DNS_VERIFY_ERROR;
! 189: }
! 190: #endif
! 191:
! 192: debug("found %d fingerprints in DNS", keys->rri_nrdatas);
! 193:
! 194: /* Initialize host key parameters */
! 195: if (!dns_read_key(&hostkey_algorithm, &hostkey_digest_type,
! 196: &hostkey_digest, &hostkey_digest_len, hostkey)) {
! 197: error("Error calculating host key fingerprint.");
! 198: return DNS_VERIFY_ERROR;
! 199: }
! 200:
! 201: for (counter = 0 ; counter < keys->rri_nrdatas ; counter++) {
! 202: /*
! 203: * Extract the key from the answer. Ignore any badly
! 204: * formatted keys.
! 205: */
! 206: if (!dns_read_rdata(&dnskey_algorithm, &dnskey_digest_type,
! 207: &dnskey_digest, &dnskey_digest_len,
! 208: keys->rri_rdatas[counter].rdi_data,
! 209: keys->rri_rdatas[counter].rdi_length)) {
! 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:
! 222: /* Matching algoritm and digest. */
! 223: freerrset(keys);
! 224: #ifdef DNSSEC
! 225: debug("matching host key fingerprint found in DNS");
! 226: return DNS_VERIFY_OK;
! 227: #else
! 228: logit("Matching host key fingerprint found in DNS.");
! 229: return DNS_VERIFY_ERROR;
! 230: #endif
! 231: } else {
! 232: /* Correct algorithm but bad digest */
! 233: debug("verify_hostkey_dns: failed");
! 234: failures++;
! 235: }
! 236: }
! 237: }
! 238:
! 239: freerrset(keys);
! 240:
! 241: if (failures) {
! 242: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
! 243: error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @");
! 244: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
! 245: error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
! 246: error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
! 247: error("It is also possible that the %s host key has just been changed.",
! 248: key_type(hostkey));
! 249: error("Please contact your system administrator.");
! 250: return DNS_VERIFY_FAILED;
! 251: }
! 252:
! 253: debug("fingerprints found in DNS, but none of them matched");
! 254:
! 255: return DNS_VERIFY_ERROR;
! 256: }
! 257:
! 258:
! 259: /*
! 260: * Export the fingerprint of a key as a DNS resource record
! 261: */
! 262: int
! 263: export_dns_rr(const char *hostname, Key *key, FILE *f, int generic)
! 264: {
! 265: u_int8_t rdata_pubkey_algorithm = 0;
! 266: u_int8_t rdata_digest_type = DNS_HASH_SHA1;
! 267: u_char *rdata_digest;
! 268: u_int rdata_digest_len;
! 269:
! 270: int i;
! 271: int success = 0;
! 272:
! 273: if (dns_read_key(&rdata_pubkey_algorithm, &rdata_digest_type,
! 274: &rdata_digest, &rdata_digest_len, key)) {
! 275:
! 276: if (generic)
! 277: fprintf(f, "%s IN TYPE%d \\# %d %02x %02x ", hostname,
! 278: DNS_RDATATYPE_SSHFP, 2 + rdata_digest_len,
! 279: rdata_pubkey_algorithm, rdata_digest_type);
! 280: else
! 281: fprintf(f, "%s IN SSHFP %d %d ", hostname,
! 282: rdata_pubkey_algorithm, rdata_digest_type);
! 283:
! 284: for (i = 0; i < rdata_digest_len; i++)
! 285: fprintf(f, "%02x", rdata_digest[i]);
! 286: fprintf(f, "\n");
! 287: success = 1;
! 288: } else {
! 289: error("dns_export_rr: unsupported algorithm");
! 290: }
! 291:
! 292: return success;
! 293: }
! 294:
! 295: #endif /* DNS */
![[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