Damien Miller | e3476ed | 2006-07-24 14:13:33 +1000 | [diff] [blame] | 1 | /* $OpenBSD: dns.c,v 1.21 2006/07/22 20:48:23 stevesk Exp $ */ |
Damien Miller | 37876e9 | 2003-05-15 10:19:46 +1000 | [diff] [blame] | 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 | |
Damien Miller | 37876e9 | 2003-05-15 10:19:46 +1000 | [diff] [blame] | 28 | #include "includes.h" |
| 29 | |
Damien Miller | e3b60b5 | 2006-07-10 21:08:03 +1000 | [diff] [blame] | 30 | #include <sys/types.h> |
| 31 | #include <sys/socket.h> |
| 32 | |
Damien Miller | be43ebf | 2006-07-24 13:51:51 +1000 | [diff] [blame] | 33 | #if defined(HAVE_NETDB_H) |
| 34 | # include <netdb.h> |
| 35 | #endif |
Damien Miller | e3476ed | 2006-07-24 14:13:33 +1000 | [diff] [blame] | 36 | #include <string.h> |
Damien Miller | 37876e9 | 2003-05-15 10:19:46 +1000 | [diff] [blame] | 37 | |
| 38 | #include "xmalloc.h" |
| 39 | #include "key.h" |
| 40 | #include "dns.h" |
| 41 | #include "log.h" |
Damien Miller | 37876e9 | 2003-05-15 10:19:46 +1000 | [diff] [blame] | 42 | |
Damien Miller | 37876e9 | 2003-05-15 10:19:46 +1000 | [diff] [blame] | 43 | static const char *errset_text[] = { |
| 44 | "success", /* 0 ERRSET_SUCCESS */ |
| 45 | "out of memory", /* 1 ERRSET_NOMEMORY */ |
| 46 | "general failure", /* 2 ERRSET_FAIL */ |
| 47 | "invalid parameter", /* 3 ERRSET_INVAL */ |
| 48 | "name does not exist", /* 4 ERRSET_NONAME */ |
| 49 | "data does not exist", /* 5 ERRSET_NODATA */ |
| 50 | }; |
| 51 | |
| 52 | static const char * |
Darren Tucker | 3f9fdc7 | 2004-06-22 12:56:01 +1000 | [diff] [blame] | 53 | dns_result_totext(unsigned int res) |
Damien Miller | 37876e9 | 2003-05-15 10:19:46 +1000 | [diff] [blame] | 54 | { |
Darren Tucker | 3f9fdc7 | 2004-06-22 12:56:01 +1000 | [diff] [blame] | 55 | switch (res) { |
Damien Miller | 37876e9 | 2003-05-15 10:19:46 +1000 | [diff] [blame] | 56 | case ERRSET_SUCCESS: |
| 57 | return errset_text[ERRSET_SUCCESS]; |
| 58 | case ERRSET_NOMEMORY: |
| 59 | return errset_text[ERRSET_NOMEMORY]; |
| 60 | case ERRSET_FAIL: |
| 61 | return errset_text[ERRSET_FAIL]; |
| 62 | case ERRSET_INVAL: |
| 63 | return errset_text[ERRSET_INVAL]; |
| 64 | case ERRSET_NONAME: |
| 65 | return errset_text[ERRSET_NONAME]; |
| 66 | case ERRSET_NODATA: |
| 67 | return errset_text[ERRSET_NODATA]; |
| 68 | default: |
| 69 | return "unknown error"; |
| 70 | } |
| 71 | } |
Damien Miller | 37876e9 | 2003-05-15 10:19:46 +1000 | [diff] [blame] | 72 | |
| 73 | /* |
| 74 | * Read SSHFP parameters from key buffer. |
| 75 | */ |
| 76 | static int |
| 77 | dns_read_key(u_int8_t *algorithm, u_int8_t *digest_type, |
Damien Miller | 150b557 | 2003-11-17 21:19:29 +1100 | [diff] [blame] | 78 | u_char **digest, u_int *digest_len, const Key *key) |
Damien Miller | 37876e9 | 2003-05-15 10:19:46 +1000 | [diff] [blame] | 79 | { |
| 80 | int success = 0; |
| 81 | |
| 82 | switch (key->type) { |
| 83 | case KEY_RSA: |
| 84 | *algorithm = SSHFP_KEY_RSA; |
| 85 | break; |
| 86 | case KEY_DSA: |
| 87 | *algorithm = SSHFP_KEY_DSA; |
| 88 | break; |
| 89 | default: |
Damien Miller | 6571249 | 2005-11-05 15:09:27 +1100 | [diff] [blame] | 90 | *algorithm = SSHFP_KEY_RESERVED; /* 0 */ |
Damien Miller | 37876e9 | 2003-05-15 10:19:46 +1000 | [diff] [blame] | 91 | } |
| 92 | |
| 93 | if (*algorithm) { |
| 94 | *digest_type = SSHFP_HASH_SHA1; |
| 95 | *digest = key_fingerprint_raw(key, SSH_FP_SHA1, digest_len); |
Damien Miller | 6571249 | 2005-11-05 15:09:27 +1100 | [diff] [blame] | 96 | if (*digest == NULL) |
| 97 | fatal("dns_read_key: null from key_fingerprint_raw()"); |
Damien Miller | 37876e9 | 2003-05-15 10:19:46 +1000 | [diff] [blame] | 98 | success = 1; |
| 99 | } else { |
| 100 | *digest_type = SSHFP_HASH_RESERVED; |
| 101 | *digest = NULL; |
| 102 | *digest_len = 0; |
| 103 | success = 0; |
| 104 | } |
| 105 | |
| 106 | return success; |
| 107 | } |
| 108 | |
| 109 | /* |
| 110 | * Read SSHFP parameters from rdata buffer. |
| 111 | */ |
| 112 | static int |
| 113 | dns_read_rdata(u_int8_t *algorithm, u_int8_t *digest_type, |
| 114 | u_char **digest, u_int *digest_len, u_char *rdata, int rdata_len) |
| 115 | { |
| 116 | int success = 0; |
| 117 | |
| 118 | *algorithm = SSHFP_KEY_RESERVED; |
| 119 | *digest_type = SSHFP_HASH_RESERVED; |
| 120 | |
| 121 | if (rdata_len >= 2) { |
| 122 | *algorithm = rdata[0]; |
| 123 | *digest_type = rdata[1]; |
| 124 | *digest_len = rdata_len - 2; |
| 125 | |
| 126 | if (*digest_len > 0) { |
| 127 | *digest = (u_char *) xmalloc(*digest_len); |
| 128 | memcpy(*digest, rdata + 2, *digest_len); |
| 129 | } else { |
Damien Miller | 5996294 | 2006-03-26 00:06:48 +1100 | [diff] [blame] | 130 | *digest = (u_char *)xstrdup(""); |
Damien Miller | 37876e9 | 2003-05-15 10:19:46 +1000 | [diff] [blame] | 131 | } |
| 132 | |
| 133 | success = 1; |
| 134 | } |
| 135 | |
| 136 | return success; |
| 137 | } |
| 138 | |
Damien Miller | a31c929 | 2005-05-26 12:03:31 +1000 | [diff] [blame] | 139 | /* |
| 140 | * Check if hostname is numerical. |
| 141 | * Returns -1 if hostname is numeric, 0 otherwise |
| 142 | */ |
| 143 | static int |
| 144 | is_numeric_hostname(const char *hostname) |
| 145 | { |
| 146 | struct addrinfo hints, *ai; |
| 147 | |
| 148 | memset(&hints, 0, sizeof(hints)); |
| 149 | hints.ai_socktype = SOCK_DGRAM; |
| 150 | hints.ai_flags = AI_NUMERICHOST; |
| 151 | |
| 152 | if (getaddrinfo(hostname, "0", &hints, &ai) == 0) { |
| 153 | freeaddrinfo(ai); |
| 154 | return -1; |
| 155 | } |
| 156 | |
| 157 | return 0; |
| 158 | } |
Damien Miller | 37876e9 | 2003-05-15 10:19:46 +1000 | [diff] [blame] | 159 | |
| 160 | /* |
| 161 | * Verify the given hostname, address and host key using DNS. |
Damien Miller | a8e06ce | 2003-11-21 23:48:55 +1100 | [diff] [blame] | 162 | * Returns 0 if lookup succeeds, -1 otherwise |
Damien Miller | 37876e9 | 2003-05-15 10:19:46 +1000 | [diff] [blame] | 163 | */ |
| 164 | int |
| 165 | verify_host_key_dns(const char *hostname, struct sockaddr *address, |
Damien Miller | 150b557 | 2003-11-17 21:19:29 +1100 | [diff] [blame] | 166 | const Key *hostkey, int *flags) |
Damien Miller | 37876e9 | 2003-05-15 10:19:46 +1000 | [diff] [blame] | 167 | { |
Damien Miller | eccb9de | 2005-06-17 12:59:34 +1000 | [diff] [blame] | 168 | u_int counter; |
Damien Miller | 37876e9 | 2003-05-15 10:19:46 +1000 | [diff] [blame] | 169 | int result; |
| 170 | struct rrsetinfo *fingerprints = NULL; |
Damien Miller | 37876e9 | 2003-05-15 10:19:46 +1000 | [diff] [blame] | 171 | |
| 172 | u_int8_t hostkey_algorithm; |
| 173 | u_int8_t hostkey_digest_type; |
| 174 | u_char *hostkey_digest; |
| 175 | u_int hostkey_digest_len; |
| 176 | |
| 177 | u_int8_t dnskey_algorithm; |
| 178 | u_int8_t dnskey_digest_type; |
| 179 | u_char *dnskey_digest; |
| 180 | u_int dnskey_digest_len; |
| 181 | |
Damien Miller | 150b557 | 2003-11-17 21:19:29 +1100 | [diff] [blame] | 182 | *flags = 0; |
Damien Miller | 37876e9 | 2003-05-15 10:19:46 +1000 | [diff] [blame] | 183 | |
Damien Miller | 319550a | 2005-11-05 15:11:15 +1100 | [diff] [blame] | 184 | debug3("verify_host_key_dns"); |
Damien Miller | 37876e9 | 2003-05-15 10:19:46 +1000 | [diff] [blame] | 185 | if (hostkey == NULL) |
| 186 | fatal("No key to look up!"); |
| 187 | |
Damien Miller | a31c929 | 2005-05-26 12:03:31 +1000 | [diff] [blame] | 188 | if (is_numeric_hostname(hostname)) { |
| 189 | debug("skipped DNS lookup for numerical hostname"); |
| 190 | return -1; |
| 191 | } |
| 192 | |
Damien Miller | 37876e9 | 2003-05-15 10:19:46 +1000 | [diff] [blame] | 193 | result = getrrsetbyname(hostname, DNS_RDATACLASS_IN, |
| 194 | DNS_RDATATYPE_SSHFP, 0, &fingerprints); |
| 195 | if (result) { |
| 196 | verbose("DNS lookup error: %s", dns_result_totext(result)); |
Damien Miller | 150b557 | 2003-11-17 21:19:29 +1100 | [diff] [blame] | 197 | return -1; |
Damien Miller | 37876e9 | 2003-05-15 10:19:46 +1000 | [diff] [blame] | 198 | } |
| 199 | |
Damien Miller | 150b557 | 2003-11-17 21:19:29 +1100 | [diff] [blame] | 200 | if (fingerprints->rri_flags & RRSET_VALIDATED) { |
| 201 | *flags |= DNS_VERIFY_SECURE; |
| 202 | debug("found %d secure fingerprints in DNS", |
| 203 | fingerprints->rri_nrdatas); |
| 204 | } else { |
| 205 | debug("found %d insecure fingerprints in DNS", |
| 206 | fingerprints->rri_nrdatas); |
Damien Miller | 37876e9 | 2003-05-15 10:19:46 +1000 | [diff] [blame] | 207 | } |
Damien Miller | 37876e9 | 2003-05-15 10:19:46 +1000 | [diff] [blame] | 208 | |
| 209 | /* Initialize host key parameters */ |
| 210 | if (!dns_read_key(&hostkey_algorithm, &hostkey_digest_type, |
| 211 | &hostkey_digest, &hostkey_digest_len, hostkey)) { |
| 212 | error("Error calculating host key fingerprint."); |
Damien Miller | b062265 | 2003-05-15 13:27:28 +1000 | [diff] [blame] | 213 | freerrset(fingerprints); |
Damien Miller | 150b557 | 2003-11-17 21:19:29 +1100 | [diff] [blame] | 214 | return -1; |
Damien Miller | 37876e9 | 2003-05-15 10:19:46 +1000 | [diff] [blame] | 215 | } |
| 216 | |
Damien Miller | 150b557 | 2003-11-17 21:19:29 +1100 | [diff] [blame] | 217 | if (fingerprints->rri_nrdatas) |
| 218 | *flags |= DNS_VERIFY_FOUND; |
| 219 | |
Damien Miller | 20afc24 | 2005-11-05 15:06:38 +1100 | [diff] [blame] | 220 | for (counter = 0; counter < fingerprints->rri_nrdatas; counter++) { |
Damien Miller | 37876e9 | 2003-05-15 10:19:46 +1000 | [diff] [blame] | 221 | /* |
| 222 | * Extract the key from the answer. Ignore any badly |
| 223 | * formatted fingerprints. |
| 224 | */ |
| 225 | if (!dns_read_rdata(&dnskey_algorithm, &dnskey_digest_type, |
| 226 | &dnskey_digest, &dnskey_digest_len, |
| 227 | fingerprints->rri_rdatas[counter].rdi_data, |
| 228 | fingerprints->rri_rdatas[counter].rdi_length)) { |
| 229 | verbose("Error parsing fingerprint from DNS."); |
| 230 | continue; |
| 231 | } |
| 232 | |
| 233 | /* Check if the current key is the same as the given key */ |
| 234 | if (hostkey_algorithm == dnskey_algorithm && |
| 235 | hostkey_digest_type == dnskey_digest_type) { |
| 236 | |
| 237 | if (hostkey_digest_len == dnskey_digest_len && |
| 238 | memcmp(hostkey_digest, dnskey_digest, |
| 239 | hostkey_digest_len) == 0) { |
| 240 | |
Damien Miller | 150b557 | 2003-11-17 21:19:29 +1100 | [diff] [blame] | 241 | *flags |= DNS_VERIFY_MATCH; |
Damien Miller | 37876e9 | 2003-05-15 10:19:46 +1000 | [diff] [blame] | 242 | } |
| 243 | } |
Damien Miller | 6571249 | 2005-11-05 15:09:27 +1100 | [diff] [blame] | 244 | xfree(dnskey_digest); |
Damien Miller | 37876e9 | 2003-05-15 10:19:46 +1000 | [diff] [blame] | 245 | } |
| 246 | |
Damien Miller | 6571249 | 2005-11-05 15:09:27 +1100 | [diff] [blame] | 247 | xfree(hostkey_digest); /* from key_fingerprint_raw() */ |
Damien Miller | 37876e9 | 2003-05-15 10:19:46 +1000 | [diff] [blame] | 248 | freerrset(fingerprints); |
| 249 | |
Damien Miller | 150b557 | 2003-11-17 21:19:29 +1100 | [diff] [blame] | 250 | if (*flags & DNS_VERIFY_FOUND) |
| 251 | if (*flags & DNS_VERIFY_MATCH) |
| 252 | debug("matching host key fingerprint found in DNS"); |
| 253 | else |
| 254 | debug("mismatching host key fingerprint found in DNS"); |
| 255 | else |
| 256 | debug("no host key fingerprint found in DNS"); |
Damien Miller | 37876e9 | 2003-05-15 10:19:46 +1000 | [diff] [blame] | 257 | |
Damien Miller | 150b557 | 2003-11-17 21:19:29 +1100 | [diff] [blame] | 258 | return 0; |
Damien Miller | 37876e9 | 2003-05-15 10:19:46 +1000 | [diff] [blame] | 259 | } |
| 260 | |
Damien Miller | 37876e9 | 2003-05-15 10:19:46 +1000 | [diff] [blame] | 261 | /* |
| 262 | * Export the fingerprint of a key as a DNS resource record |
| 263 | */ |
| 264 | int |
Damien Miller | 150b557 | 2003-11-17 21:19:29 +1100 | [diff] [blame] | 265 | export_dns_rr(const char *hostname, const Key *key, FILE *f, int generic) |
Damien Miller | 37876e9 | 2003-05-15 10:19:46 +1000 | [diff] [blame] | 266 | { |
| 267 | u_int8_t rdata_pubkey_algorithm = 0; |
| 268 | u_int8_t rdata_digest_type = SSHFP_HASH_SHA1; |
| 269 | u_char *rdata_digest; |
| 270 | u_int rdata_digest_len; |
| 271 | |
Damien Miller | eccb9de | 2005-06-17 12:59:34 +1000 | [diff] [blame] | 272 | u_int i; |
Damien Miller | 37876e9 | 2003-05-15 10:19:46 +1000 | [diff] [blame] | 273 | int success = 0; |
| 274 | |
| 275 | if (dns_read_key(&rdata_pubkey_algorithm, &rdata_digest_type, |
Damien Miller | 319550a | 2005-11-05 15:11:15 +1100 | [diff] [blame] | 276 | &rdata_digest, &rdata_digest_len, key)) { |
Damien Miller | 37876e9 | 2003-05-15 10:19:46 +1000 | [diff] [blame] | 277 | |
| 278 | if (generic) |
| 279 | fprintf(f, "%s IN TYPE%d \\# %d %02x %02x ", hostname, |
| 280 | DNS_RDATATYPE_SSHFP, 2 + rdata_digest_len, |
| 281 | rdata_pubkey_algorithm, rdata_digest_type); |
| 282 | else |
| 283 | fprintf(f, "%s IN SSHFP %d %d ", hostname, |
| 284 | rdata_pubkey_algorithm, rdata_digest_type); |
| 285 | |
| 286 | for (i = 0; i < rdata_digest_len; i++) |
| 287 | fprintf(f, "%02x", rdata_digest[i]); |
| 288 | fprintf(f, "\n"); |
Damien Miller | 6571249 | 2005-11-05 15:09:27 +1100 | [diff] [blame] | 289 | xfree(rdata_digest); /* from key_fingerprint_raw() */ |
Damien Miller | 37876e9 | 2003-05-15 10:19:46 +1000 | [diff] [blame] | 290 | success = 1; |
| 291 | } else { |
Damien Miller | 319550a | 2005-11-05 15:11:15 +1100 | [diff] [blame] | 292 | error("export_dns_rr: unsupported algorithm"); |
Damien Miller | 37876e9 | 2003-05-15 10:19:46 +1000 | [diff] [blame] | 293 | } |
| 294 | |
| 295 | return success; |
| 296 | } |