Greg Hartman | ccacbc9 | 2016-02-03 09:59:44 -0800 | [diff] [blame] | 1 | /* $OpenBSD: dns.c,v 1.35 2015/08/20 22:32:42 deraadt Exp $ */ |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [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 | |
| 28 | #include "includes.h" |
| 29 | |
| 30 | #include <sys/types.h> |
| 31 | #include <sys/socket.h> |
| 32 | |
| 33 | #include <netdb.h> |
| 34 | #include <stdarg.h> |
| 35 | #include <stdio.h> |
| 36 | #include <string.h> |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 37 | #include <stdarg.h> |
| 38 | #include <stdlib.h> |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 39 | |
| 40 | #include "xmalloc.h" |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 41 | #include "sshkey.h" |
| 42 | #include "ssherr.h" |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 43 | #include "dns.h" |
| 44 | #include "log.h" |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 45 | #include "digest.h" |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 46 | |
| 47 | static const char *errset_text[] = { |
| 48 | "success", /* 0 ERRSET_SUCCESS */ |
| 49 | "out of memory", /* 1 ERRSET_NOMEMORY */ |
| 50 | "general failure", /* 2 ERRSET_FAIL */ |
| 51 | "invalid parameter", /* 3 ERRSET_INVAL */ |
| 52 | "name does not exist", /* 4 ERRSET_NONAME */ |
| 53 | "data does not exist", /* 5 ERRSET_NODATA */ |
| 54 | }; |
| 55 | |
| 56 | static const char * |
| 57 | dns_result_totext(unsigned int res) |
| 58 | { |
| 59 | switch (res) { |
| 60 | case ERRSET_SUCCESS: |
| 61 | return errset_text[ERRSET_SUCCESS]; |
| 62 | case ERRSET_NOMEMORY: |
| 63 | return errset_text[ERRSET_NOMEMORY]; |
| 64 | case ERRSET_FAIL: |
| 65 | return errset_text[ERRSET_FAIL]; |
| 66 | case ERRSET_INVAL: |
| 67 | return errset_text[ERRSET_INVAL]; |
| 68 | case ERRSET_NONAME: |
| 69 | return errset_text[ERRSET_NONAME]; |
| 70 | case ERRSET_NODATA: |
| 71 | return errset_text[ERRSET_NODATA]; |
| 72 | default: |
| 73 | return "unknown error"; |
| 74 | } |
| 75 | } |
| 76 | |
| 77 | /* |
| 78 | * Read SSHFP parameters from key buffer. |
| 79 | */ |
| 80 | static int |
| 81 | dns_read_key(u_int8_t *algorithm, u_int8_t *digest_type, |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 82 | u_char **digest, size_t *digest_len, struct sshkey *key) |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 83 | { |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 84 | int r, success = 0; |
| 85 | int fp_alg = -1; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 86 | |
| 87 | switch (key->type) { |
| 88 | case KEY_RSA: |
| 89 | *algorithm = SSHFP_KEY_RSA; |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 90 | if (!*digest_type) |
| 91 | *digest_type = SSHFP_HASH_SHA1; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 92 | break; |
| 93 | case KEY_DSA: |
| 94 | *algorithm = SSHFP_KEY_DSA; |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 95 | if (!*digest_type) |
| 96 | *digest_type = SSHFP_HASH_SHA1; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 97 | break; |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 98 | case KEY_ECDSA: |
| 99 | *algorithm = SSHFP_KEY_ECDSA; |
| 100 | if (!*digest_type) |
| 101 | *digest_type = SSHFP_HASH_SHA256; |
| 102 | break; |
| 103 | case KEY_ED25519: |
| 104 | *algorithm = SSHFP_KEY_ED25519; |
| 105 | if (!*digest_type) |
| 106 | *digest_type = SSHFP_HASH_SHA256; |
| 107 | break; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 108 | default: |
| 109 | *algorithm = SSHFP_KEY_RESERVED; /* 0 */ |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 110 | *digest_type = SSHFP_HASH_RESERVED; /* 0 */ |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 111 | } |
| 112 | |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 113 | switch (*digest_type) { |
| 114 | case SSHFP_HASH_SHA1: |
| 115 | fp_alg = SSH_DIGEST_SHA1; |
| 116 | break; |
| 117 | case SSHFP_HASH_SHA256: |
| 118 | fp_alg = SSH_DIGEST_SHA256; |
| 119 | break; |
| 120 | default: |
| 121 | *digest_type = SSHFP_HASH_RESERVED; /* 0 */ |
| 122 | } |
| 123 | |
| 124 | if (*algorithm && *digest_type) { |
| 125 | if ((r = sshkey_fingerprint_raw(key, fp_alg, digest, |
| 126 | digest_len)) != 0) |
| 127 | fatal("%s: sshkey_fingerprint_raw: %s", __func__, |
| 128 | ssh_err(r)); |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 129 | success = 1; |
| 130 | } else { |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 131 | *digest = NULL; |
| 132 | *digest_len = 0; |
| 133 | success = 0; |
| 134 | } |
| 135 | |
| 136 | return success; |
| 137 | } |
| 138 | |
| 139 | /* |
| 140 | * Read SSHFP parameters from rdata buffer. |
| 141 | */ |
| 142 | static int |
| 143 | dns_read_rdata(u_int8_t *algorithm, u_int8_t *digest_type, |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 144 | u_char **digest, size_t *digest_len, u_char *rdata, int rdata_len) |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 145 | { |
| 146 | int success = 0; |
| 147 | |
| 148 | *algorithm = SSHFP_KEY_RESERVED; |
| 149 | *digest_type = SSHFP_HASH_RESERVED; |
| 150 | |
| 151 | if (rdata_len >= 2) { |
| 152 | *algorithm = rdata[0]; |
| 153 | *digest_type = rdata[1]; |
| 154 | *digest_len = rdata_len - 2; |
| 155 | |
| 156 | if (*digest_len > 0) { |
Greg Hartman | ccacbc9 | 2016-02-03 09:59:44 -0800 | [diff] [blame] | 157 | *digest = xmalloc(*digest_len); |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 158 | memcpy(*digest, rdata + 2, *digest_len); |
| 159 | } else { |
| 160 | *digest = (u_char *)xstrdup(""); |
| 161 | } |
| 162 | |
| 163 | success = 1; |
| 164 | } |
| 165 | |
| 166 | return success; |
| 167 | } |
| 168 | |
| 169 | /* |
| 170 | * Check if hostname is numerical. |
| 171 | * Returns -1 if hostname is numeric, 0 otherwise |
| 172 | */ |
| 173 | static int |
| 174 | is_numeric_hostname(const char *hostname) |
| 175 | { |
| 176 | struct addrinfo hints, *ai; |
| 177 | |
| 178 | /* |
| 179 | * We shouldn't ever get a null host but if we do then log an error |
| 180 | * and return -1 which stops DNS key fingerprint processing. |
| 181 | */ |
| 182 | if (hostname == NULL) { |
| 183 | error("is_numeric_hostname called with NULL hostname"); |
| 184 | return -1; |
| 185 | } |
| 186 | |
| 187 | memset(&hints, 0, sizeof(hints)); |
| 188 | hints.ai_socktype = SOCK_DGRAM; |
| 189 | hints.ai_flags = AI_NUMERICHOST; |
| 190 | |
| 191 | if (getaddrinfo(hostname, NULL, &hints, &ai) == 0) { |
| 192 | freeaddrinfo(ai); |
| 193 | return -1; |
| 194 | } |
| 195 | |
| 196 | return 0; |
| 197 | } |
| 198 | |
| 199 | /* |
| 200 | * Verify the given hostname, address and host key using DNS. |
| 201 | * Returns 0 if lookup succeeds, -1 otherwise |
| 202 | */ |
| 203 | int |
| 204 | verify_host_key_dns(const char *hostname, struct sockaddr *address, |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 205 | struct sshkey *hostkey, int *flags) |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 206 | { |
| 207 | u_int counter; |
| 208 | int result; |
| 209 | struct rrsetinfo *fingerprints = NULL; |
| 210 | |
| 211 | u_int8_t hostkey_algorithm; |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 212 | u_int8_t hostkey_digest_type = SSHFP_HASH_RESERVED; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 213 | u_char *hostkey_digest; |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 214 | size_t hostkey_digest_len; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 215 | |
| 216 | u_int8_t dnskey_algorithm; |
| 217 | u_int8_t dnskey_digest_type; |
| 218 | u_char *dnskey_digest; |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 219 | size_t dnskey_digest_len; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 220 | |
| 221 | *flags = 0; |
| 222 | |
| 223 | debug3("verify_host_key_dns"); |
| 224 | if (hostkey == NULL) |
| 225 | fatal("No key to look up!"); |
| 226 | |
| 227 | if (is_numeric_hostname(hostname)) { |
| 228 | debug("skipped DNS lookup for numerical hostname"); |
| 229 | return -1; |
| 230 | } |
| 231 | |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 232 | #if !defined(ANDROID) |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 233 | result = getrrsetbyname(hostname, DNS_RDATACLASS_IN, |
| 234 | DNS_RDATATYPE_SSHFP, 0, &fingerprints); |
| 235 | #else |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 236 | /* unsupported in Android. */ |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 237 | result = -1; |
| 238 | #endif |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 239 | |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 240 | if (result) { |
| 241 | verbose("DNS lookup error: %s", dns_result_totext(result)); |
| 242 | return -1; |
| 243 | } |
| 244 | |
| 245 | if (fingerprints->rri_flags & RRSET_VALIDATED) { |
| 246 | *flags |= DNS_VERIFY_SECURE; |
| 247 | debug("found %d secure fingerprints in DNS", |
| 248 | fingerprints->rri_nrdatas); |
| 249 | } else { |
| 250 | debug("found %d insecure fingerprints in DNS", |
| 251 | fingerprints->rri_nrdatas); |
| 252 | } |
| 253 | |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 254 | /* Initialize default host key parameters */ |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 255 | if (!dns_read_key(&hostkey_algorithm, &hostkey_digest_type, |
| 256 | &hostkey_digest, &hostkey_digest_len, hostkey)) { |
| 257 | error("Error calculating host key fingerprint."); |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 258 | #if !defined(ANDROID) |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 259 | freerrset(fingerprints); |
| 260 | #endif |
| 261 | return -1; |
| 262 | } |
| 263 | |
| 264 | if (fingerprints->rri_nrdatas) |
| 265 | *flags |= DNS_VERIFY_FOUND; |
| 266 | |
| 267 | for (counter = 0; counter < fingerprints->rri_nrdatas; counter++) { |
| 268 | /* |
| 269 | * Extract the key from the answer. Ignore any badly |
| 270 | * formatted fingerprints. |
| 271 | */ |
| 272 | if (!dns_read_rdata(&dnskey_algorithm, &dnskey_digest_type, |
| 273 | &dnskey_digest, &dnskey_digest_len, |
| 274 | fingerprints->rri_rdatas[counter].rdi_data, |
| 275 | fingerprints->rri_rdatas[counter].rdi_length)) { |
| 276 | verbose("Error parsing fingerprint from DNS."); |
| 277 | continue; |
| 278 | } |
| 279 | |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 280 | if (hostkey_digest_type != dnskey_digest_type) { |
| 281 | hostkey_digest_type = dnskey_digest_type; |
| 282 | free(hostkey_digest); |
| 283 | |
| 284 | /* Initialize host key parameters */ |
| 285 | if (!dns_read_key(&hostkey_algorithm, |
| 286 | &hostkey_digest_type, &hostkey_digest, |
| 287 | &hostkey_digest_len, hostkey)) { |
| 288 | error("Error calculating key fingerprint."); |
| 289 | #if !defined(ANDROID) |
| 290 | freerrset(fingerprints); |
| 291 | #endif |
| 292 | return -1; |
| 293 | } |
| 294 | } |
| 295 | |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 296 | /* Check if the current key is the same as the given key */ |
| 297 | if (hostkey_algorithm == dnskey_algorithm && |
| 298 | hostkey_digest_type == dnskey_digest_type) { |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 299 | if (hostkey_digest_len == dnskey_digest_len && |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 300 | timingsafe_bcmp(hostkey_digest, dnskey_digest, |
| 301 | hostkey_digest_len) == 0) |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 302 | *flags |= DNS_VERIFY_MATCH; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 303 | } |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 304 | free(dnskey_digest); |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 305 | } |
| 306 | |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 307 | free(hostkey_digest); /* from sshkey_fingerprint_raw() */ |
| 308 | #if !defined(ANDROID) |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 309 | freerrset(fingerprints); |
| 310 | #endif |
| 311 | |
| 312 | if (*flags & DNS_VERIFY_FOUND) |
| 313 | if (*flags & DNS_VERIFY_MATCH) |
| 314 | debug("matching host key fingerprint found in DNS"); |
| 315 | else |
| 316 | debug("mismatching host key fingerprint found in DNS"); |
| 317 | else |
| 318 | debug("no host key fingerprint found in DNS"); |
| 319 | |
| 320 | return 0; |
| 321 | } |
| 322 | |
| 323 | /* |
| 324 | * Export the fingerprint of a key as a DNS resource record |
| 325 | */ |
| 326 | int |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 327 | export_dns_rr(const char *hostname, struct sshkey *key, FILE *f, int generic) |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 328 | { |
| 329 | u_int8_t rdata_pubkey_algorithm = 0; |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 330 | u_int8_t rdata_digest_type = SSHFP_HASH_RESERVED; |
| 331 | u_int8_t dtype; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 332 | u_char *rdata_digest; |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 333 | size_t i, rdata_digest_len; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 334 | int success = 0; |
| 335 | |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 336 | for (dtype = SSHFP_HASH_SHA1; dtype < SSHFP_HASH_MAX; dtype++) { |
| 337 | rdata_digest_type = dtype; |
| 338 | if (dns_read_key(&rdata_pubkey_algorithm, &rdata_digest_type, |
| 339 | &rdata_digest, &rdata_digest_len, key)) { |
| 340 | if (generic) { |
| 341 | fprintf(f, "%s IN TYPE%d \\# %zu %02x %02x ", |
| 342 | hostname, DNS_RDATATYPE_SSHFP, |
| 343 | 2 + rdata_digest_len, |
| 344 | rdata_pubkey_algorithm, rdata_digest_type); |
| 345 | } else { |
| 346 | fprintf(f, "%s IN SSHFP %d %d ", hostname, |
| 347 | rdata_pubkey_algorithm, rdata_digest_type); |
| 348 | } |
| 349 | for (i = 0; i < rdata_digest_len; i++) |
| 350 | fprintf(f, "%02x", rdata_digest[i]); |
| 351 | fprintf(f, "\n"); |
| 352 | free(rdata_digest); /* from sshkey_fingerprint_raw() */ |
| 353 | success = 1; |
| 354 | } |
| 355 | } |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 356 | |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 357 | /* No SSHFP record was generated at all */ |
| 358 | if (success == 0) { |
| 359 | error("%s: unsupported algorithm and/or digest_type", __func__); |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 360 | } |
| 361 | |
| 362 | return success; |
| 363 | } |