src/gns/gnunet-service-gns_interceptor.c

   1 /*
   2      This file is part of GNUnet.
   3      (C) 2009, 2010, 2011 Christian Grothoff (and other contributing authors)
   4
   5      GNUnet is free software; you can redistribute it and/or modify
   6      it under the terms of the GNU General Public License as published
   7      by the Free Software Foundation; either version 3, or (at your
   8      option) any later version.
   9
  10      GNUnet is distributed in the hope that it will be useful, but
  11      WITHOUT ANY WARRANTY; without even the implied warranty of
  12      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13      General Public License for more details.
  14
  15      You should have received a copy of the GNU General Public License
  16      along with GNUnet; see the file COPYING.  If not, write to the
  17      Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18      Boston, MA 02111-1307, USA.
  19 */
  20
  21 /**
  22  *
  23  * @file gns/gnunet-service-gns_interceptor.c
  24  * @brief GNUnet GNS interceptor logic
  25  * @author Martin Schanzenbach
  26  */
  27 #include "platform.h"
  28 #include "gnunet_util_lib.h"
  29 #include "gnunet_transport_service.h"
  30 #include "gnunet_dns_service.h"
  31 #include "gnunet_dnsparser_lib.h"
  32 #include "gnunet-service-gns_resolver.h"
  33 #include "gns.h"
  34
  35 #define MAX_DNS_LABEL_LENGTH 63
  36
  37 /**
  38  * Handle to a DNS intercepted
  39  * reslution request
  40  */
  41 struct InterceptLookupHandle
  42 {
  43   /* the request handle to reply to */
  44   struct GNUNET_DNS_RequestHandle *request_handle;
  45
  46   /* the dns parser packet received */
  47   struct GNUNET_DNSPARSER_Packet *packet;
  48
  49   /* the query parsed from the packet */
  50   struct GNUNET_DNSPARSER_Query *query;
  51 };
  52
  53
  54 /**
  55  * Our handle to the DNS handler library
  56  */
  57 static struct GNUNET_DNS_Handle *dns_handle;
  58
  59 /**
  60  * The root zone for this interceptor
  61  */
  62 static struct GNUNET_CRYPTO_ShortHashCode our_zone;
  63
  64 /**
  65  * Our priv key
  66  */
  67 static struct GNUNET_CRYPTO_RsaPrivateKey *our_key;
  68
  69 /**
  70  * Default timeout
  71  */
  72 static struct GNUNET_TIME_Relative default_lookup_timeout;
  73
  74 /**
  75  * Reply to dns request with the result from our lookup.
  76  *
  77  * @param cls the closure to the request (an InterceptLookupHandle)
  78  * @param rd_count the number of records to return
  79  * @param rd the record data
  80  */
  81 static void
  82 reply_to_dns(void* cls, uint32_t rd_count,
  83              const struct GNUNET_NAMESTORE_RecordData *rd)
  84 {
  85   int i;
  86   size_t len;
  87   int ret;
  88   char *buf;
  89   struct InterceptLookupHandle* ilh = (struct InterceptLookupHandle*)cls;
  90   struct GNUNET_DNSPARSER_Packet *packet = ilh->packet;
  91   unsigned int num_answers = 0;
  92
  93
  94   /**
  95    * Put records in the DNS packet and modify it
  96    * to a response
  97    */
  98   for (i=0; i < rd_count; i++)
  99   {
 100     if (rd[i].record_type == ilh->query->type)
 101       num_answers++;
 102   }
 103
 104   struct GNUNET_DNSPARSER_Record answer_records[num_answers];
 105   struct GNUNET_DNSPARSER_Record additional_records[rd_count-(num_answers)];
 106   packet->answers = answer_records;
 107   packet->additional_records = additional_records;
 108
 109   for (i=0; i < rd_count; i++)
 110   {
 111     GNUNET_log(GNUNET_ERROR_TYPE_DEBUG,
 112                "Adding type %d to DNS response\n", rd[i].record_type);
 113     GNUNET_log(GNUNET_ERROR_TYPE_DEBUG, "Name: %s\n", ilh->query->name);
 114     GNUNET_log(GNUNET_ERROR_TYPE_DEBUG, "Record %d/%d\n", i+1, rd_count);
 115     GNUNET_log(GNUNET_ERROR_TYPE_DEBUG, "Record len %d\n", rd[i].data_size);
 116
 117     if (rd[i].record_type == ilh->query->type)
 118     {
 119       answer_records[i].name = ilh->query->name;
 120       answer_records[i].type = rd[i].record_type;
 121       switch(rd[i].record_type)
 122       {
 123        case GNUNET_GNS_RECORD_TYPE_NS:
 124        case GNUNET_GNS_RECORD_TYPE_CNAME:
 125        case GNUNET_GNS_RECORD_TYPE_PTR:
 126          answer_records[i].data.hostname = (char*)rd[i].data;
 127          break;
 128        case GNUNET_GNS_RECORD_TYPE_SOA:
 129          answer_records[i].data.soa =
 130            (struct GNUNET_DNSPARSER_SoaRecord *)rd[i].data;
 131          break;
 132        case GNUNET_GNS_RECORD_MX:
 133          answer_records[i].data.mx =
 134            (struct GNUNET_DNSPARSER_MxRecord *)rd[i].data;
 135          break;
 136        default:
 137         answer_records[i].data.raw.data_len = rd[i].data_size;
 138         answer_records[i].data.raw.data = (char*)rd[i].data;
 139       }
 140       answer_records[i].expiration_time = rd[i].expiration;
 141       answer_records[i].class = GNUNET_DNSPARSER_CLASS_INTERNET;//hmmn
 142     }
 143     else
 144     {
 145       additional_records[i].name = ilh->query->name;
 146       additional_records[i].type = rd[i].record_type;
 147       switch(rd[i].record_type)
 148       {
 149        case GNUNET_GNS_RECORD_TYPE_NS:
 150        case GNUNET_GNS_RECORD_TYPE_CNAME:
 151        case GNUNET_GNS_RECORD_TYPE_PTR:
 152          additional_records[i].data.hostname = (char*)rd[i].data;
 153          break;
 154        case GNUNET_GNS_RECORD_TYPE_SOA:
 155          additional_records[i].data.soa =
 156            (struct GNUNET_DNSPARSER_SoaRecord *)rd[i].data;
 157          break;
 158        case GNUNET_GNS_RECORD_MX:
 159          additional_records[i].data.mx =
 160            (struct GNUNET_DNSPARSER_MxRecord *)rd[i].data;
 161          break;
 162        default:
 163         additional_records[i].data.raw.data_len = rd[i].data_size;
 164         additional_records[i].data.raw.data = (char*)rd[i].data;
 165       }
 166       additional_records[i].expiration_time = rd[i].expiration;
 167       additional_records[i].class = GNUNET_DNSPARSER_CLASS_INTERNET;//hmmn
 168     }
 169   }
 170
 171   packet->num_answers = num_answers;
 172   packet->num_additional_records = rd_count-(num_answers);
 173
 174   packet->flags.authoritative_answer = 1;
 175
 176   if (rd == NULL)
 177     packet->flags.return_code = GNUNET_DNSPARSER_RETURN_CODE_NAME_ERROR;
 178   else
 179     packet->flags.return_code = GNUNET_DNSPARSER_RETURN_CODE_NO_ERROR;
 180
 181   packet->flags.query_or_response = 1;
 182
 183
 184   /**
 185    * Reply to DNS
 186    */
 187   GNUNET_log(GNUNET_ERROR_TYPE_DEBUG,
 188              "Building DNS response\n");
 189   ret = GNUNET_DNSPARSER_pack (packet,
 190                                1024, /* FIXME magic from dns redirector */
 191                                &buf,
 192                                &len);
 193   GNUNET_log(GNUNET_ERROR_TYPE_DEBUG,
 194              "Built DNS response! (ret=%d,len=%d)\n", ret, len);
 195   if (ret == GNUNET_OK)
 196   {
 197     GNUNET_log(GNUNET_ERROR_TYPE_DEBUG,
 198                "Answering DNS request\n");
 199     GNUNET_DNS_request_answer(ilh->request_handle,
 200                               len,
 201                               buf);
 202
 203     GNUNET_free(buf);
 204     GNUNET_log(GNUNET_ERROR_TYPE_DEBUG, "Answered DNS request\n");
 205   }
 206   else
 207   {
 208     GNUNET_log(GNUNET_ERROR_TYPE_ERROR,
 209                "Error building DNS response! (ret=%d)", ret);
 210   }
 211
 212   packet->num_answers = 0;
 213   packet->answers = NULL;
 214   packet->num_additional_records = 0;
 215   packet->additional_records = NULL;
 216   GNUNET_DNSPARSER_free_packet(packet);
 217   GNUNET_free(ilh);
 218 }
 219
 220
 221 /**
 222  * Entry point for name resolution
 223  * Setup a new query and try to resolve
 224  *
 225  * @param request the request handle of the DNS request from a client
 226  * @param p the DNS query packet we received
 227  * @param q the DNS query we received parsed from p
 228  */
 229 static void
 230 start_resolution_for_dns(struct GNUNET_DNS_RequestHandle *request,
 231                           struct GNUNET_DNSPARSER_Packet *p,
 232                           struct GNUNET_DNSPARSER_Query *q)
 233 {
 234   struct InterceptLookupHandle* ilh;
 235
 236   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
 237               "Starting resolution for %s (type=%d)!\n",
 238               q->name, q->type);
 239
 240   ilh = GNUNET_malloc(sizeof(struct InterceptLookupHandle));
 241   ilh->packet = p;
 242   ilh->query = q;
 243   ilh->request_handle = request;
 244
 245   /* Start resolution in our zone */
 246   gns_resolver_lookup_record(our_zone, our_zone, q->type, q->name,
 247                              our_key,
 248                              default_lookup_timeout,
 249                              GNUNET_NO,
 250                              &reply_to_dns, ilh);
 251 }
 252
 253
 254
 255 /**
 256  * The DNS request handler
 257  * Called for every incoming DNS request.
 258  *
 259  * @param cls closure
 260  * @param rh request handle to user for reply
 261  * @param request_length number of bytes in request
 262  * @param request udp payload of the DNS request
 263  */
 264 static void
 265 handle_dns_request(void *cls,
 266                    struct GNUNET_DNS_RequestHandle *rh,
 267                    size_t request_length,
 268                    const char *request)
 269 {
 270   struct GNUNET_DNSPARSER_Packet *p;
 271
 272   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Hijacked a DNS request...processing\n");
 273   p = GNUNET_DNSPARSER_parse (request, request_length);
 274
 275   if (NULL == p)
 276   {
 277     GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
 278                 "Received malformed DNS packet, leaving it untouched\n");
 279     GNUNET_DNS_request_forward (rh);
 280     GNUNET_DNSPARSER_free_packet (p);
 281     return;
 282   }
 283
 284   /**
 285    * Check tld and decide if we or
 286    * legacy dns is responsible
 287    *
 288    * FIXME now in theory there could be more than 1 query in the request
 289    * but if this is case we get into trouble:
 290    * either we query the GNS or the DNS. We cannot do both!
 291    * So I suggest to either only allow a single query per request or
 292    * only allow GNS or DNS requests.
 293    * The way it is implemented here now is buggy and will lead to erratic
 294    * behaviour (if multiple queries are present).
 295    */
 296   if (p->num_queries == 0)
 297   {
 298     GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
 299                 "No Queries in DNS packet... forwarding\n");
 300     GNUNET_DNS_request_forward (rh);
 301     GNUNET_DNSPARSER_free_packet(p);
 302     return;
 303   }
 304
 305   if (p->num_queries > 1)
 306   {
 307     /* Note: We could also look for .gnunet */
 308     GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
 309                 ">1 queriy in DNS packet... odd. We only process #1\n");
 310   }
 311
 312
 313   /**
 314    * Check for .gnunet/.zkey
 315    */
 316
 317   if ((is_gnunet_tld(p->queries[0].name) == GNUNET_YES) ||
 318       (is_zkey_tld(p->queries[0].name) == GNUNET_YES) ||
 319       (strcmp(p->queries[0].name, GNUNET_GNS_TLD) == 0))
 320   {
 321     start_resolution_for_dns(rh, p, p->queries);
 322   }
 323   else
 324   {
 325     /**
 326      * This request does not concern us. Forward to real DNS.
 327      */
 328     GNUNET_log(GNUNET_ERROR_TYPE_DEBUG,
 329                "Request for %s is forwarded to DNS\n", p->queries[0].name);
 330     GNUNET_DNS_request_forward (rh);
 331     GNUNET_DNSPARSER_free_packet (p);
 332   }
 333
 334 }
 335
 336
 337 /**
 338  * Initialized the interceptor
 339  *
 340  * @param zone the zone to work in
 341  * @param key the prov key of the zone (can be null, needed for caching)
 342  * @param c the configuration
 343  * @return GNUNET_OK on success
 344  */
 345 int
 346 gns_interceptor_init(struct GNUNET_CRYPTO_ShortHashCode zone,
 347                      struct GNUNET_CRYPTO_RsaPrivateKey *key,
 348                      const struct GNUNET_CONFIGURATION_Handle *c)
 349 {
 350   unsigned long long default_lookup_timeout_secs = 0;
 351
 352   GNUNET_log(GNUNET_ERROR_TYPE_INFO,
 353              "DNS hijacking enabled... connecting to service.\n");
 354
 355   our_zone = zone;
 356   our_key = key;
 357   /**
 358    * Do gnunet dns init here
 359    */
 360   dns_handle = GNUNET_DNS_connect(c,
 361                                   GNUNET_DNS_FLAG_PRE_RESOLUTION,
 362                                   &handle_dns_request, /* rh */
 363                                   NULL); /* Closure */
 364
 365   if (GNUNET_OK ==
 366       GNUNET_CONFIGURATION_get_value_number(c, "gns",
 367                                             "DEFAULT_LOOKUP_TIMEOUT",
 368                                             &default_lookup_timeout_secs))
 369   {
 370     default_lookup_timeout = GNUNET_TIME_relative_multiply(
 371                                                   GNUNET_TIME_UNIT_SECONDS,
 372                                                   default_lookup_timeout_secs);
 373   }
 374
 375   if (NULL == dns_handle)
 376   {
 377     GNUNET_log(GNUNET_ERROR_TYPE_ERROR,
 378              "Failed to connect to the dnsservice!\n");
 379     return GNUNET_SYSERR;
 380   }
 381
 382   return GNUNET_YES;
 383 }
 384
 385 /**
 386  * Disconnect from interceptor
 387  */
 388 void
 389 gns_interceptor_stop(void)
 390 {
 391   if (dns_handle)
 392     GNUNET_DNS_disconnect(dns_handle);
 393 }
 394
 395 /* end of gns_interceptor.c */