libdane/dane.c

   1 /*
   2  * Copyright (C) 2012 KU Leuven
   3  *
   4  * Author: Nikos Mavrogiannopoulos
   5  *
   6  * This file is part of libdane.
   7  *
   8  * libdane is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public License
  10  * as published by the Free Software Foundation; either version 3 of
  11  * the License, or (at your option) any later version.
  12  *
  13  * This library is distributed in the hope that it will be useful, but
  14  * WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16  * Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public License
  19  * along with this program.  If not, see <http://www.gnu.org/licenses/>
  20  *
  21  */
  22
  23 #include <config.h>
  24
  25 #include <stdio.h>
  26 #include <stdlib.h>
  27 #include <string.h>
  28 #include <errno.h>
  29 #include <arpa/inet.h>
  30 #include <unbound.h>
  31 #include <gnutls/dane.h>
  32 #include <gnutls/x509.h>
  33 #include <gnutls/abstract.h>
  34 #include <gnutls/crypto.h>
  35
  36 #define MAX_DATA_ENTRIES 4
  37
  38 struct dane_query_st
  39 {
  40         unsigned int data_entries;
  41         dane_cert_usage_t usage[MAX_DATA_ENTRIES];
  42         dane_cert_type_t  type[MAX_DATA_ENTRIES];
  43         dane_match_type_t match[MAX_DATA_ENTRIES];
  44         gnutls_datum_t data[MAX_DATA_ENTRIES];
  45         struct ub_ctx* ctx;
  46         struct ub_result* result;
  47         unsigned int flags;
  48         dane_query_status_t status;
  49 };
  50
  51 /**
  52  * dane_query_status:
  53  * @q: The query structure
  54  *
  55  * This function will return the status of the query response.
  56  * See %dane_query_status_t for the possible types.
  57  *
  58  * Returns: The status type.
  59  **/
  60 dane_query_status_t dane_query_status(dane_query_t q)
  61 {
  62         return q->status;
  63 }
  64
  65 /**
  66  * dane_query_entries:
  67  * @q: The query structure
  68  *
  69  * This function will return the number of entries in a query.
  70  *
  71  * Returns: The number of entries.
  72  **/
  73 unsigned int dane_query_entries(dane_query_t q)
  74 {
  75         return q->data_entries;
  76 }
  77
  78 /**
  79  * dane_query_data:
  80  * @q: The query structure
  81  * @idx: The index of the query response.
  82  * @usage: The certificate usage (see %dane_cert_usage_t)
  83  * @type: The certificate type (see %dane_cert_type_t)
  84  * @match: The DANE matching type (see %dane_match_type_t)
  85  * @data: The DANE data.
  86  *
  87  * This function will provide the DANE data from the query
  88  * response.
  89  *
  90  * Returns: On success, %DANE_E_SUCCESS (0) is returned, otherwise a
  91  *   negative error value.
  92  **/
  93 int dane_query_data(dane_query_t q, unsigned int idx,
  94                         unsigned int *usage, unsigned int *type,
  95                         unsigned int *match, gnutls_datum_t * data)
  96 {
  97         if (idx >= q->data_entries)
  98                 return DANE_E_REQUESTED_DATA_NOT_AVAILABLE;
  99
 100         if (usage)
 101                 *usage = q->usage[idx];
 102         if (type)
 103                 *type = q->type[idx];
 104         if (match)
 105                 *match = q->match[idx];
 106         if (data) {
 107                 data->data = q->data[idx].data;
 108                 data->size = q->data[idx].size;
 109         }
 110
 111         return DANE_E_SUCCESS;
 112 }
 113
 114 /**
 115  * dane_query_init:
 116  * @q: The structure to be initialized
 117  * @flags: flags from the DANE_F_* definitions
 118  *
 119  * This function will initialize a DANE query structure.
 120  *
 121  * Returns: On success, %DANE_E_SUCCESS (0) is returned, otherwise a
 122  *   negative error value.
 123  **/
 124 int dane_query_init(dane_query_t* q, unsigned int flags)
 125 {
 126         struct ub_ctx* ctx;
 127         int ret;
 128
 129         *q = calloc(1, sizeof(struct dane_query_st));
 130         if (*q == NULL)
 131                 return DANE_E_MEMORY_ERROR;
 132
 133         ctx = ub_ctx_create();
 134         if(!ctx) {
 135                 ret = DANE_E_INITIALIZATION_ERROR;
 136                 goto cleanup;
 137         }
 138         ub_ctx_debugout(ctx, stderr);
 139
 140         if (!(flags & DANE_F_IGNORE_LOCAL_RESOLVER)) {
 141                 if( (ret=ub_ctx_resolvconf(ctx, NULL)) != 0) {
 142                         ret = DANE_E_INITIALIZATION_ERROR;
 143                         goto cleanup;
 144                 }
 145
 146                 if( (ret=ub_ctx_hosts(ctx, NULL)) != 0) {
 147                         ret = DANE_E_INITIALIZATION_ERROR;
 148                         goto cleanup;
 149                 }
 150         }
 151
 152         /* read public keys for DNSSEC verification */
 153         if( (ret=ub_ctx_add_ta_file(ctx, (char*)UNBOUND_ROOT_KEY_FILE)) != 0) {
 154                 ret = DANE_E_INITIALIZATION_ERROR;
 155                 goto cleanup;
 156         }
 157
 158         (*q)->ctx = ctx;
 159         (*q)->flags = flags;
 160
 161         return DANE_E_SUCCESS;
 162 cleanup:
 163
 164         if (ctx)
 165                 ub_ctx_delete(ctx);
 166         free(*q);
 167
 168         return ret;
 169 }
 170
 171 /**
 172  * dane_query_init:
 173  * @q: The structure to be deinitialized
 174  *
 175  * This function will deinitialize a DANE query structure.
 176  *
 177  **/
 178 void dane_query_deinit(dane_query_t q)
 179 {
 180         if (q->result)
 181         ub_ctx_delete(q->ctx);
 182                 ub_resolve_free(q->result);
 183
 184         free(q);
 185 }
 186
 187 /**
 188  * dane_query_resolve_tlsa:
 189  * @q: The query structure
 190  * @host: The host name to resolve.
 191  * @proto: The protocol type (tcp, udp, etc.)
 192  * @port: The service port number (eg. 443).
 193  *
 194  * This function will query the DNS server for the TLSA (DANE)
 195  * data for the given host.
 196  *
 197  * Returns: On success, %DANE_E_SUCCESS (0) is returned, otherwise a
 198  *   negative error value.
 199  **/
 200 int dane_query_resolve_tlsa(dane_query_t q, const char* host, const char* proto, unsigned int port)
 201 {
 202         char ns[1024];
 203         int ret;
 204         unsigned int i;
 205
 206         if (q->result) {
 207                 ub_resolve_free(q->result);
 208                 q->result = NULL;
 209         }
 210
 211         snprintf(ns, sizeof(ns), "_%u._%s.%s", port, proto, host);
 212
 213         /* query for webserver */
 214         ret = ub_resolve(q->ctx, ns, 52, 1, &q->result);
 215         if(ret != 0) {
 216                 return DANE_E_RESOLVING_ERROR;
 217         }
 218
 219 /* show first result */
 220         if(!q->result->havedata) {
 221                 return DANE_E_NO_DANE_DATA;
 222         }
 223
 224         i = 0;
 225         do {
 226
 227                 if (q->result->len[i] > 3)
 228                         ret = DANE_E_SUCCESS;
 229                 else {
 230                         return DANE_E_RECEIVED_CORRUPT_DATA;
 231                 }
 232
 233                 q->usage[i] = q->result->data[i][0];
 234                 q->type[i] = q->result->data[i][1];
 235                 q->match[i] = q->result->data[i][2];
 236                 q->data[i].data = (void*)&q->result->data[i][3];
 237                 q->data[i].size = q->result->len[i];
 238                 i++;
 239         } while(q->result->data[i] != NULL);
 240
 241         q->data_entries = i;
 242
 243         if (!q->result->secure) {
 244                 if (q->result->bogus)
 245                         ret = DANE_E_INVALID_DNSSEC_SIG;
 246                 else
 247                         ret = DANE_E_NO_DNSSEC_SIG;
 248         }
 249
 250         /* show security status */
 251         if (q->result->secure)
 252                 q->status = DANE_QUERY_DNSSEC_VERIFIED;
 253         else if (q->result->bogus)
 254                 q->status = DANE_QUERY_BOGUS;
 255         else q->status = DANE_QUERY_NO_DNSSEC;
 256
 257         return ret;
 258 }
 259
 260 static unsigned int matches(const gnutls_datum_t *raw1, const gnutls_datum_t *raw2,
 261                                                         dane_match_type_t match)
 262 {
 263 uint8_t digest[64];
 264 int ret;
 265
 266         if (match == DANE_MATCH_EXACT) {
 267                 if (raw1->size != raw2->size)
 268                         return 0;
 269
 270                 if (memcmp(raw1->data, raw2->data, raw1->size) != 0)
 271                         return 0;
 272
 273                 return 1;
 274         } else if (match == DANE_MATCH_SHA2_256) {
 275
 276                 if (raw2->size < 32)
 277                         return 0;
 278
 279                 ret = gnutls_hash_fast(GNUTLS_DIG_SHA256, raw1->data, raw1->size, digest);
 280                 if (ret < 0)
 281                         return 0;
 282
 283                 if (memcmp(digest, raw2->data, 32) != 0)
 284                         return 0;
 285
 286                 return 1;
 287         } else if (match == DANE_MATCH_SHA2_512) {
 288                 if (raw2->size < 64)
 289                         return 0;
 290
 291                 ret = gnutls_hash_fast(GNUTLS_DIG_SHA512, raw1->data, raw1->size, digest);
 292                 if (ret < 0)
 293                         return 0;
 294
 295                 if (memcmp(digest, raw2->data, 64) != 0)
 296                         return 0;
 297
 298                 return 1;
 299         }
 300
 301         return 0;
 302 }
 303
 304 static int crt_to_pubkey(const gnutls_datum_t *raw_crt, gnutls_datum_t * out)
 305 {
 306 gnutls_pubkey_t pub = NULL;
 307 gnutls_x509_crt_t crt = NULL;
 308 int ret;
 309 size_t size;
 310
 311         out->data = NULL;
 312
 313         ret = gnutls_x509_crt_init(&crt);
 314         if (ret < 0)
 315                 return DANE_E_PUBKEY_ERROR;
 316
 317         ret = gnutls_pubkey_init( &pub);
 318         if (ret < 0) {
 319                 ret = DANE_E_PUBKEY_ERROR;
 320                 goto cleanup;
 321         }
 322
 323         ret = gnutls_x509_crt_import(crt, raw_crt, GNUTLS_X509_FMT_DER);
 324         if (ret < 0) {
 325                 ret = DANE_E_PUBKEY_ERROR;
 326                 goto cleanup;
 327         }
 328
 329         ret = gnutls_pubkey_import_x509(pub, crt, 0);
 330         if (ret < 0) {
 331                 ret = DANE_E_PUBKEY_ERROR;
 332                 goto cleanup;
 333         }
 334
 335         size = 0;
 336         ret = gnutls_pubkey_export(pub, GNUTLS_X509_FMT_DER, NULL, &size);
 337         if (ret < 0 && ret != GNUTLS_E_SHORT_MEMORY_BUFFER) {
 338                 ret = DANE_E_PUBKEY_ERROR;
 339                 goto cleanup;
 340         }
 341
 342         out->data = malloc(size);
 343         if (out->data == NULL) {
 344                 ret = DANE_E_MEMORY_ERROR;
 345                 goto cleanup;
 346         }
 347
 348         ret = gnutls_pubkey_export(pub, GNUTLS_X509_FMT_DER, out->data, &size);
 349         if (ret < 0) {
 350                 ret = DANE_E_PUBKEY_ERROR;
 351                 goto cleanup;
 352         }
 353
 354         out->size = size;
 355
 356         ret = 0;
 357         goto clean_certs;
 358
 359 cleanup:
 360         free(out->data);
 361 clean_certs:
 362         if (pub)
 363                 gnutls_pubkey_deinit(pub);
 364         if (crt)
 365                 gnutls_x509_crt_deinit(crt);
 366
 367         return ret;
 368 }
 369
 370 static int verify_ca(const gnutls_datum_t *raw_crt, unsigned raw_crt_size,
 371                                          gnutls_certificate_type_t crt_type,
 372                                          dane_cert_type_t ctype,
 373                                          dane_match_type_t match, gnutls_datum_t * data,
 374                                          unsigned int *verify)
 375 {
 376 gnutls_datum_t pubkey = {NULL, 0};
 377 int ret;
 378
 379         if (raw_crt_size < 2)
 380                 return DANE_E_INVALID_REQUEST;
 381
 382         if (ctype == DANE_CERT_X509 && crt_type == GNUTLS_CRT_X509) {
 383
 384                 if (!matches(&raw_crt[1], data, match))
 385                         *verify |= DANE_VERIFY_CA_CONSTRAINS_VIOLATED;
 386
 387         } else if (ctype == DANE_CERT_PK && crt_type == GNUTLS_CRT_X509) {
 388                 ret = crt_to_pubkey(&raw_crt[1], &pubkey);
 389                 if (ret < 0)
 390                         goto cleanup;
 391
 392                 if (!matches(&pubkey, data, match))
 393                         *verify |= DANE_VERIFY_CA_CONSTRAINS_VIOLATED;
 394         }
 395
 396         ret = 0;
 397 cleanup:
 398         free(pubkey.data);
 399         return ret;
 400 }
 401
 402 static int verify_ee(const gnutls_datum_t *raw_crt, gnutls_certificate_type_t crt_type,
 403                  dane_cert_type_t ctype, dane_match_type_t match, gnutls_datum_t * data,
 404                  unsigned int *verify)
 405 {
 406 gnutls_datum_t pubkey = {NULL, 0};
 407 int ret;
 408
 409         if (ctype == DANE_CERT_X509 && crt_type == GNUTLS_CRT_X509) {
 410
 411                 if (!matches(raw_crt, data, match))
 412                         *verify |= DANE_VERIFY_CERT_DIFFERS;
 413
 414         } else if (ctype == DANE_CERT_PK && crt_type == GNUTLS_CRT_X509) {
 415
 416                 ret = crt_to_pubkey(raw_crt, &pubkey);
 417                 if (ret < 0)
 418                         goto cleanup;
 419
 420                 if (!matches(&pubkey, data, match))
 421                         *verify |= DANE_VERIFY_CERT_DIFFERS;
 422         }
 423
 424         ret = 0;
 425 cleanup:
 426         free(pubkey.data);
 427         return ret;
 428 }
 429
 430 /**
 431  * dane_verify_crt:
 432  * @chain: A certificate chain
 433  * @chain_size: The size of the chain
 434  * @chain_type: The type of the certificate chain
 435  * @hostname: The hostname associated with the chain
 436  * @proto: The protocol of the service connecting (e.g. tcp)
 437  * @port: The port of the service connecting (e.g. 443)
 438  * @flags: The %DANE_F flags.
 439  * @verify: An OR'ed list of %dane_verify_status_t.
 440  *
 441  * This function will verify the given certificate chain against the
 442  * CA constrains and/or the certificate available via DANE.
 443  * If no information via DANE can be obtained the flag %DANE_VERIFY_NO_DANE_INFO
 444  * is set. If a DNSSEC signature is not available for the DANE
 445  * record then the verify flag %DANE_VERIFY_NO_DNSSEC_DATA is set.
 446  *
 447  * Due to the many possible options of DANE, there is no single threat
 448  * model countered. When notifying the user about DANE verification results
 449  * it may be better to mention: DANE verification did not reject the certificate,
 450  * rather than mentioning a successful DANE verication.
 451  *
 452  * Returns: On success, %DANE_E_SUCCESS (0) is returned, otherwise a
 453  *   negative error value.
 454  *
 455  **/
 456 int dane_verify_crt (
 457         const gnutls_datum_t *chain, unsigned chain_size,
 458         gnutls_certificate_type_t chain_type,
 459         const char * hostname, const char* proto, unsigned int port,
 460         unsigned int flags, unsigned int *verify)
 461 {
 462 dane_query_t q;
 463 int ret;
 464 unsigned int usage, type, match, idx, status;
 465 gnutls_datum_t data;
 466
 467         if (chain_type != GNUTLS_CRT_X509)
 468                 return DANE_E_INVALID_REQUEST;
 469
 470         *verify = 0;
 471
 472         ret = dane_query_init(&q, flags);
 473         if (ret < 0) {
 474                 return ret;
 475         }
 476
 477         ret = dane_query_resolve_tlsa(q, hostname, proto, port);
 478         if (ret < 0) {
 479                 goto cleanup;
 480         }
 481
 482         status = dane_query_status(q);
 483         if (status == DANE_QUERY_BOGUS) {
 484                 *verify |= DANE_VERIFY_DNSSEC_DATA_INVALID;
 485                 goto cleanup;
 486         } else if (status == DANE_QUERY_NO_DNSSEC) {
 487                 *verify |= DANE_VERIFY_NO_DNSSEC_DATA;
 488                 goto cleanup;
 489         }
 490
 491         idx = 0;
 492         do {
 493                 ret = dane_query_data(q, idx++, &usage, &type, &match, &data);
 494                 if (ret == DANE_E_REQUESTED_DATA_NOT_AVAILABLE)
 495                         break;
 496
 497                 if (ret < 0) {
 498                         goto cleanup;
 499                 }
 500
 501                 if (usage == DANE_CERT_USAGE_LOCAL_CA || usage == DANE_CERT_USAGE_CA) {
 502                         ret = verify_ca(chain, chain_size, chain_type, type, match, &data, verify);
 503                         if (ret < 0)
 504                                 goto cleanup;
 505
 506                 } else if (usage == DANE_CERT_USAGE_LOCAL_EE || usage == DANE_CERT_USAGE_EE) {
 507                         ret = verify_ee(&chain[0], chain_type, type, match, &data, verify);
 508                         if (ret < 0)
 509                                 goto cleanup;
 510                 }
 511         } while(1);
 512
 513         ret = 0;
 514
 515 cleanup:
 516         dane_query_deinit(q);
 517         return ret;
 518 }
 519
 520 /**
 521  * dane_verify_session_crt:
 522  * @session: A gnutls session
 523  * @hostname: The hostname associated with the chain
 524  * @proto: The protocol of the service connecting (e.g. tcp)
 525  * @port: The port of the service connecting (e.g. 443)
 526  * @flags: The %DANE_F flags.
 527  * @verify: An OR'ed list of %dane_verify_status_t.
 528  *
 529  * This function will verify session's certificate chain against the
 530  * CA constrains and/or the certificate available via DANE.
 531  * See dane_verify_crt() for more information.
 532  *
 533  * Returns: On success, %DANE_E_SUCCESS (0) is returned, otherwise a
 534  *   negative error value.
 535  *
 536  **/
 537 int dane_verify_session_crt (
 538         gnutls_session_t session,
 539         const char * hostname, const char* proto, unsigned int port,
 540         unsigned int flags, unsigned int *verify)
 541 {
 542 const gnutls_datum_t *cert_list;
 543 unsigned int cert_list_size = 0;
 544 unsigned int type;
 545
 546         cert_list = gnutls_certificate_get_peers(session, &cert_list_size);
 547         if (cert_list_size == 0) {
 548                 return DANE_E_NO_CERT;
 549         }
 550
 551         type = gnutls_certificate_type_get(session);
 552
 553         return dane_verify_crt(cert_list, cert_list_size, type, hostname, proto, port, flags, verify);
 554 }