src/vpn/gnunet-service-dns.c

   1 /*
   2      This file is part of GNUnet.
   3      (C) 2009 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  * @file vpn/gnunet-service-dns.c
  23  * @author Philipp Toelke
  24  */
  25 #include "platform.h"
  26 #include "gnunet_getopt_lib.h"
  27 #include "gnunet_service_lib.h"
  28 #include "gnunet_network_lib.h"
  29 #include "gnunet_os_lib.h"
  30 #include "gnunet-service-dns-p.h"
  31 #include "gnunet_protocols.h"
  32 #include "gnunet-vpn-packet.h"
  33 #include "gnunet-vpn-pretty-print.h"
  34 #include "gnunet_container_lib.h"
  35 #include "gnunet-dns-parser.h"
  36 #include "gnunet_dht_service.h"
  37 #include "gnunet_block_lib.h"
  38 #include "block_dns.h"
  39 #include "gnunet_crypto_lib.h"
  40 #include "gnunet_signatures.h"
  41
  42
  43 /**
  44  * The UDP-Socket through which DNS-Resolves will be sent if they are not to be
  45  * sent through gnunet. The port of this socket will not be hijacked.
  46  */
  47 static struct GNUNET_NETWORK_Handle *dnsout;
  48
  49 /**
  50  * The port bound to the socket dnsout
  51  */
  52 static unsigned short dnsoutport;
  53
  54 /**
  55  * A handle to the DHT-Service
  56  */
  57 static struct GNUNET_DHT_Handle *dht;
  58
  59 /**
  60  * The configuration to use
  61  */
  62 static const struct GNUNET_CONFIGURATION_Handle *cfg;
  63
  64 /**
  65  * A list of DNS-Responses that have to be sent to the requesting client
  66  */
  67 static struct answer_packet_list *head;
  68
  69 /**
  70  * The tail of the list of DNS-responses
  71  */
  72 static struct answer_packet_list *tail;
  73
  74 /**
  75  * A structure containing a mapping from network-byte-ordered DNS-id to
  76  * some information needed to handle this query
  77  *
  78  * It currently allocates at least
  79  * (1 + machine-width + 32 + 32 + 16 + machine-width + 8) * 65536 bit
  80  * = 1.7 MiB on 64 bit.
  81  * = 1.2 MiB on 32 bit.
  82  */
  83 static struct {
  84     unsigned valid:1;
  85     struct GNUNET_SERVER_Client* client;
  86     unsigned local_ip:32;
  87     unsigned remote_ip:32;
  88     unsigned local_port:16;
  89     char* name;
  90     unsigned namelen:8;
  91 } query_states[65536];
  92
  93 /**
  94  * A struct used to give more than one value as
  95  * closure to receive_dht
  96  */
  97 struct receive_dht_cls {
  98     unsigned short id;
  99     struct GNUNET_DHT_GetHandle* handle;
 100 };
 101
 102 /**
 103  * Hijack all outgoing DNS-Traffic but for traffic leaving "our" port.
 104  */
 105 static void
 106 hijack(unsigned short port) {
 107     char port_s[6];
 108
 109     GNUNET_log(GNUNET_ERROR_TYPE_DEBUG, "Hijacking, port is %d\n", port);
 110     snprintf(port_s, 6, "%d", port);
 111     GNUNET_OS_start_process(NULL,
 112                             NULL,
 113                             "gnunet-helper-hijack-dns",
 114                             "gnunet-hijack-dns",
 115                             port_s,
 116                             NULL);
 117 }
 118
 119 /**
 120  * Delete the hijacking-routes
 121  */
 122 static void
 123 unhijack(unsigned short port) {
 124     char port_s[6];
 125
 126     GNUNET_log(GNUNET_ERROR_TYPE_DEBUG, "unHijacking, port is %d\n", port);
 127     snprintf(port_s, 6, "%d", port);
 128     GNUNET_OS_start_process(NULL,
 129                             NULL,
 130                             "gnunet-helper-hijack-dns",
 131                             "gnunet-hijack-dns",
 132                             "-d",
 133                             port_s,
 134                             NULL);
 135 }
 136
 137 /**
 138  * Send the DNS-Response to the client. Gets called via the notify_transmit_ready-
 139  * system.
 140  */
 141 static size_t
 142 send_answer(void* cls, size_t size, void* buf) {
 143     struct answer_packet_list* query = head;
 144     size_t len = ntohs(query->pkt.hdr.size);
 145
 146     GNUNET_assert(len <= size);
 147
 148     memcpy(buf, &query->pkt.hdr, len);
 149
 150     GNUNET_CONTAINER_DLL_remove (head, tail, query);
 151
 152     GNUNET_free(query);
 153
 154     /* When more data is to be sent, reschedule */
 155     if (head != NULL)
 156       GNUNET_SERVER_notify_transmit_ready(cls,
 157                                           ntohs(head->pkt.hdr.size),
 158                                           GNUNET_TIME_UNIT_FOREVER_REL,
 159                                           &send_answer,
 160                                           cls);
 161
 162     return len;
 163 }
 164
 165 /**
 166  * Receive a block from the dht.
 167  */
 168 static void
 169 receive_dht(void *cls,
 170             struct GNUNET_TIME_Absolute exp,
 171             const GNUNET_HashCode *key,
 172             const struct GNUNET_PeerIdentity *const *get_path,
 173             const struct GNUNET_PeerIdentity *const *put_path,
 174             enum GNUNET_BLOCK_Type type,
 175             size_t size,
 176             const void *data) {
 177
 178     unsigned short id = ((struct receive_dht_cls*)cls)->id;
 179     struct GNUNET_DHT_GetHandle* handle = ((struct receive_dht_cls*)cls)->handle;
 180     GNUNET_free(cls);
 181
 182     GNUNET_assert(type == GNUNET_BLOCK_TYPE_DNS);
 183
 184     /* If no query with this id is pending, ignore the block */
 185     if (query_states[id].valid != GNUNET_YES) return;
 186     query_states[id].valid = GNUNET_NO;
 187
 188     const struct GNUNET_DNS_Record* rec = data;
 189     GNUNET_log(GNUNET_ERROR_TYPE_DEBUG,
 190                "Got block of size %d, peer: %08x, desc: %08x\n",
 191                size,
 192                *((unsigned int*)&rec->peer),
 193                *((unsigned int*)&rec->service_descriptor));
 194
 195     size_t len = sizeof(struct answer_packet) - 1 \
 196                  + sizeof(struct dns_static) \
 197                  + query_states[id].namelen \
 198                  + sizeof(struct dns_query_line) \
 199                  + 2 /* To hold the pointer (as defined in RFC1035) to the name */ \
 200                  + sizeof(struct dns_record_line) - 1 \
 201                  + 16; /* To hold the IPv6-Address */
 202
 203     struct answer_packet_list* answer = GNUNET_malloc(len + 2*sizeof(struct answer_packet_list*));
 204     memset(answer, 0, len + 2*sizeof(struct answer_packet_list*));
 205
 206     answer->pkt.hdr.type = htons(GNUNET_MESSAGE_TYPE_LOCAL_RESPONSE_DNS);
 207     answer->pkt.hdr.size = htons(len);
 208     answer->pkt.subtype = GNUNET_DNS_ANSWER_TYPE_SERVICE;
 209
 210     GNUNET_CRYPTO_hash(&rec->peer,
 211                        sizeof(struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded),
 212                        &answer->pkt.peer);
 213
 214     memcpy(&answer->pkt.service_descriptor,
 215            &rec->service_descriptor,
 216            sizeof(GNUNET_HashCode));
 217     memcpy(&answer->pkt.service_type,
 218            &rec->service_type,
 219            sizeof(answer->pkt.service_type));
 220     memcpy(&answer->pkt.ports, &rec->ports, sizeof(answer->pkt.ports));
 221
 222     answer->pkt.from = query_states[id].remote_ip;
 223
 224     answer->pkt.to = query_states[id].local_ip;
 225     answer->pkt.dst_port = query_states[id].local_port;
 226
 227     struct dns_pkt *dpkt = (struct dns_pkt*)answer->pkt.data;
 228
 229     dpkt->s.id = id;
 230     dpkt->s.aa = 1;
 231     dpkt->s.qr = 1;
 232     dpkt->s.ra = 1;
 233     dpkt->s.qdcount = htons(1);
 234     dpkt->s.ancount = htons(1);
 235
 236     memcpy(dpkt->data, query_states[id].name, query_states[id].namelen);
 237     GNUNET_free(query_states[id].name);
 238
 239
 240     struct dns_query_line* dque = (struct dns_query_line*)(dpkt->data+(query_states[id].namelen));
 241     dque->type = htons(28); /* AAAA */
 242     dque->class = htons(1); /* IN */
 243
 244     char* anname = (char*)(dpkt->data+(query_states[id].namelen)+sizeof(struct dns_query_line));
 245     memcpy(anname, (char[]){0xc0, 0x0c}, 2);
 246
 247     struct dns_record_line *drec_data = (struct dns_record_line*)(dpkt->data+(query_states[id].namelen)+sizeof(struct dns_query_line)+2);
 248     drec_data->type = htons(28); /* AAAA */
 249     drec_data->class = htons(1); /* IN */
 250     drec_data->ttl = htonl(3600); /* FIXME: read from block */
 251     drec_data->data_len = htons(16);
 252
 253     /* Calculate at which offset in the packet the IPv6-Address belongs, it is
 254      * filled in by the daemon-vpn */
 255     answer->pkt.addroffset = htons((unsigned short)((unsigned long)(&drec_data->data)-(unsigned long)(&answer->pkt)));
 256
 257     GNUNET_CONTAINER_DLL_insert_after(head, tail, tail, answer);
 258
 259     GNUNET_SERVER_notify_transmit_ready(query_states[id].client,
 260                                         len,
 261                                         GNUNET_TIME_UNIT_FOREVER_REL,
 262                                         &send_answer,
 263                                         query_states[id].client);
 264
 265     GNUNET_DHT_get_stop(handle);
 266 }
 267
 268 /**
 269  * This receives a GNUNET_MESSAGE_TYPE_REHIJACK and rehijacks the DNS
 270  */
 271 static void
 272 rehijack(void *cls,
 273          struct GNUNET_SERVER_Client *client,
 274          const struct GNUNET_MessageHeader *message) {
 275     unhijack(dnsoutport);
 276     hijack(dnsoutport);
 277 }
 278
 279 /**
 280  * This receives the dns-payload from the daemon-vpn and sends it on over the udp-socket
 281  */
 282 static void
 283 receive_query(void *cls,
 284               struct GNUNET_SERVER_Client *client,
 285               const struct GNUNET_MessageHeader *message) {
 286     struct query_packet* pkt = (struct query_packet*)message;
 287     struct dns_pkt* dns = (struct dns_pkt*)pkt->data;
 288     struct dns_pkt_parsed* pdns = parse_dns_packet(dns);
 289
 290     query_states[dns->s.id].valid = GNUNET_YES;
 291     query_states[dns->s.id].client = client;
 292     query_states[dns->s.id].local_ip = pkt->orig_from;
 293     query_states[dns->s.id].local_port = pkt->src_port;
 294     query_states[dns->s.id].remote_ip = pkt->orig_to;
 295     query_states[dns->s.id].namelen = strlen((char*)dns->data) + 1;
 296     query_states[dns->s.id].name = GNUNET_malloc(query_states[dns->s.id].namelen);
 297     memcpy(query_states[dns->s.id].name, dns->data, query_states[dns->s.id].namelen);
 298
 299     if (pdns->queries[0]->namelen > 9 &&
 300         0 == strncmp(pdns->queries[0]->name+(pdns->queries[0]->namelen - 9), ".gnunet.", 9))
 301       {
 302         GNUNET_log(GNUNET_ERROR_TYPE_DEBUG, "Query for .gnunet!\n");
 303         GNUNET_HashCode key;
 304         GNUNET_CRYPTO_hash(pdns->queries[0]->name, pdns->queries[0]->namelen, &key);
 305
 306         GNUNET_log(GNUNET_ERROR_TYPE_DEBUG,
 307                    "Getting with key %08x, len is %d\n",
 308                    *((unsigned int*)&key),
 309                    pdns->queries[0]->namelen);
 310
 311         struct receive_dht_cls* cls = GNUNET_malloc(sizeof(struct receive_dht_cls));
 312         cls->id = dns->s.id;
 313
 314         cls->handle = GNUNET_DHT_get_start(dht,
 315                                            GNUNET_TIME_UNIT_MINUTES,
 316                                            GNUNET_BLOCK_TYPE_DNS,
 317                                            &key,
 318                                            GNUNET_DHT_RO_NONE,
 319                                            NULL,
 320                                            0,
 321                                            NULL,
 322                                            0,
 323                                            receive_dht,
 324                                            cls);
 325
 326         goto out;
 327       }
 328
 329     /* The query should be sent to the network */
 330
 331     struct sockaddr_in dest;
 332     memset(&dest, 0, sizeof dest);
 333     dest.sin_port = htons(53);
 334     dest.sin_addr.s_addr = pkt->orig_to;
 335
 336     GNUNET_NETWORK_socket_sendto(dnsout,
 337                                  dns,
 338                                  ntohs(pkt->hdr.size) - sizeof(struct query_packet) + 1,
 339                                  (struct sockaddr*) &dest,
 340                                  sizeof dest);
 341
 342 out:
 343     free_parsed_dns_packet(pdns);
 344     pdns = NULL;
 345     GNUNET_SERVER_receive_done(client, GNUNET_OK);
 346 }
 347
 348 /**
 349  * Read a response-packet of the UDP-Socket
 350  */
 351 static void
 352 read_response (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc) {
 353     unsigned char buf[65536];
 354     struct dns_pkt* dns = (struct dns_pkt*)buf;
 355
 356     if (tc->reason & GNUNET_SCHEDULER_REASON_SHUTDOWN)
 357       return;
 358
 359     struct sockaddr_in addr;
 360     memset(&addr, 0, sizeof addr);
 361     socklen_t addrlen = sizeof addr;
 362
 363     int r;
 364     r = GNUNET_NETWORK_socket_recvfrom(dnsout,
 365                                        buf,
 366                                        65536,
 367                                        (struct sockaddr*)&addr,
 368                                        &addrlen);
 369
 370     /* if (r < 0) FIXME */
 371
 372     if (query_states[dns->s.id].valid == GNUNET_YES) {
 373         query_states[dns->s.id].valid = GNUNET_NO;
 374
 375         size_t len = sizeof(struct answer_packet) + r - 1; /* 1 for the unsigned char data[1]; */
 376         struct answer_packet_list* answer = GNUNET_malloc(len + 2*sizeof(struct answer_packet_list*));
 377         answer->pkt.hdr.type = htons(GNUNET_MESSAGE_TYPE_LOCAL_RESPONSE_DNS);
 378         answer->pkt.hdr.size = htons(len);
 379         answer->pkt.subtype = GNUNET_DNS_ANSWER_TYPE_IP;
 380         answer->pkt.from = addr.sin_addr.s_addr;
 381         answer->pkt.to = query_states[dns->s.id].local_ip;
 382         answer->pkt.dst_port = query_states[dns->s.id].local_port;
 383         memcpy(answer->pkt.data, buf, r);
 384
 385         GNUNET_CONTAINER_DLL_insert_after(head, tail, tail, answer);
 386
 387         GNUNET_SERVER_notify_transmit_ready(query_states[dns->s.id].client,
 388                                             len,
 389                                             GNUNET_TIME_UNIT_FOREVER_REL,
 390                                             &send_answer,
 391                                             query_states[dns->s.id].client);
 392     }
 393
 394     GNUNET_SCHEDULER_add_read_net(GNUNET_TIME_UNIT_FOREVER_REL,
 395                                   dnsout,
 396                                   &read_response,
 397                                   NULL);
 398 }
 399
 400
 401 /**
 402  * Task run during shutdown.
 403  *
 404  * @param cls unused
 405  * @param tc unused
 406  */
 407 static void
 408 cleanup_task (void *cls,
 409               const struct GNUNET_SCHEDULER_TaskContext *tc)
 410 {
 411   unhijack(dnsoutport);
 412   GNUNET_DHT_disconnect(dht);
 413 }
 414
 415 /**
 416  * Publish a DNS-record in the DHT. This is up to now just for testing.
 417  */
 418 static void
 419 publish_name (void *cls,
 420               const struct GNUNET_SCHEDULER_TaskContext *tc) {
 421     if (0 != (tc->reason & GNUNET_SCHEDULER_REASON_SHUTDOWN))
 422       return;
 423
 424     char* name = "philipptoelke.gnunet.";
 425     size_t size = sizeof(struct GNUNET_DNS_Record);
 426     struct GNUNET_DNS_Record data;
 427     memset(&data, 0, size);
 428
 429     data.purpose.size = htonl(size - sizeof(struct GNUNET_CRYPTO_RsaSignature));
 430     data.purpose.purpose = GNUNET_SIGNATURE_PURPOSE_DNS_RECORD;
 431
 432     GNUNET_CRYPTO_hash(name, strlen(name)+1, &data.service_descriptor);
 433
 434     char* keyfile;
 435     if (GNUNET_OK != GNUNET_CONFIGURATION_get_value_filename(cfg, "GNUNETD",
 436                                                              "HOSTKEY", &keyfile))
 437       {
 438         GNUNET_log(GNUNET_ERROR_TYPE_ERROR, "could not read keyfile-value\n");
 439         if (keyfile != NULL) GNUNET_free(keyfile);
 440         return;
 441       }
 442
 443     struct GNUNET_CRYPTO_RsaPrivateKey *my_private_key = GNUNET_CRYPTO_rsa_key_create_from_file(keyfile);
 444     GNUNET_free(keyfile);
 445
 446     GNUNET_CRYPTO_rsa_key_get_public(my_private_key, &data.peer);
 447
 448     data.expiration_time = GNUNET_TIME_relative_to_absolute(GNUNET_TIME_UNIT_HOURS);
 449
 450   /* Sign the block */
 451     if (GNUNET_OK != GNUNET_CRYPTO_rsa_sign(my_private_key,
 452                                             &data.purpose,
 453                                             &data.signature))
 454       {
 455         GNUNET_log(GNUNET_ERROR_TYPE_ERROR, "could not sign DNS_Record\n");
 456         return;
 457       }
 458     GNUNET_CRYPTO_rsa_key_free(my_private_key);
 459
 460     GNUNET_log(GNUNET_ERROR_TYPE_DEBUG,
 461                "Putting with key %08x\n",
 462                *((unsigned int*)&data.service_descriptor));
 463
 464     GNUNET_DHT_put(dht,
 465                    &data.service_descriptor,
 466                    GNUNET_DHT_RO_NONE,
 467                    GNUNET_BLOCK_TYPE_DNS,
 468                    size,
 469                    (char*)&data,
 470                    GNUNET_TIME_relative_to_absolute(GNUNET_TIME_UNIT_HOURS),
 471                    GNUNET_TIME_UNIT_MINUTES,
 472                    NULL,
 473                    NULL);
 474
 475     GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_UNIT_HOURS,
 476                                   publish_name,
 477                                   NULL);
 478 }
 479
 480 /**
 481  * @param cls closure
 482  * @param server the initialized server
 483  * @param cfg configuration to use
 484  */
 485 static void
 486 run (void *cls,
 487      struct GNUNET_SERVER_Handle *server,
 488      const struct GNUNET_CONFIGURATION_Handle *cfg_)
 489 {
 490   static const struct GNUNET_SERVER_MessageHandler handlers[] = {
 491       /* callback, cls, type, size */
 492         {&receive_query, NULL, GNUNET_MESSAGE_TYPE_LOCAL_QUERY_DNS, 0},
 493         {&rehijack, NULL, GNUNET_MESSAGE_TYPE_REHIJACK, sizeof(struct GNUNET_MessageHeader)},
 494         {NULL, NULL, 0, 0}
 495   };
 496
 497   cfg = cfg_;
 498
 499   unsigned int i;
 500   for (i = 0; i < 65536; i++) {
 501       query_states[i].valid = GNUNET_NO;
 502   }
 503
 504   dht = GNUNET_DHT_connect(cfg, 1024);
 505
 506   struct sockaddr_in addr;
 507
 508   dnsout = GNUNET_NETWORK_socket_create (AF_INET, SOCK_DGRAM, 0);
 509   if (dnsout == NULL)
 510     return;
 511   memset(&addr, 0, sizeof(struct sockaddr_in));
 512
 513   int err = GNUNET_NETWORK_socket_bind (dnsout,
 514                                         (struct sockaddr*)&addr,
 515                                         sizeof(struct sockaddr_in));
 516
 517   if (err != GNUNET_YES) {
 518       GNUNET_log(GNUNET_ERROR_TYPE_ERROR, "Could not bind a port, exiting\n");
 519       return;
 520   }
 521
 522   /* Read the port we bound to */
 523   socklen_t addrlen = sizeof(struct sockaddr_in);
 524   err = getsockname(GNUNET_NETWORK_get_fd(dnsout),
 525                     (struct sockaddr*) &addr,
 526                     &addrlen);
 527
 528   dnsoutport = htons(addr.sin_port);
 529
 530   hijack(htons(addr.sin_port));
 531
 532   GNUNET_SCHEDULER_add_now (publish_name, NULL);
 533
 534   GNUNET_SCHEDULER_add_read_net(GNUNET_TIME_UNIT_FOREVER_REL, dnsout, &read_response, NULL);
 535
 536   GNUNET_SERVER_add_handlers (server, handlers);
 537   GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_UNIT_FOREVER_REL,
 538                                 &cleanup_task,
 539                                 cls);
 540 }
 541
 542 /**
 543  * The main function for the dns service.
 544  *
 545  * @param argc number of arguments from the command line
 546  * @param argv command line arguments
 547  * @return 0 ok, 1 on error
 548  */
 549 int
 550 main (int argc, char *const *argv)
 551 {
 552   return (GNUNET_OK ==
 553           GNUNET_SERVICE_run (argc,
 554                               argv,
 555                               "dns",
 556                               GNUNET_SERVICE_OPTION_NONE,
 557                               &run, NULL)) ? 0 : 1;
 558 }