www.tinc-vpn.org Git - tinc/blob - src/net_packet.c

   1 /*
   2     net_packet.c -- Handles in- and outgoing VPN packets
   3     Copyright (C) 1998-2005 Ivo Timmermans,
   4                   2000-2009 Guus Sliepen <guus@tinc-vpn.org>
   5
   6     This program is free software; you can redistribute it and/or modify
   7     it under the terms of the GNU General Public License as published by
   8     the Free Software Foundation; either version 2 of the License, or
   9     (at your option) any later version.
  10
  11     This program is distributed in the hope that it will be useful,
  12     but WITHOUT ANY WARRANTY; without even the implied warranty of
  13     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14     GNU General Public License for more details.
  15
  16     You should have received a copy of the GNU General Public License along
  17     with this program; if not, write to the Free Software Foundation, Inc.,
  18     51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  19 */
  20
  21 #include "system.h"
  22
  23 #include <openssl/rand.h>
  24 #include <openssl/err.h>
  25 #include <openssl/evp.h>
  26 #include <openssl/pem.h>
  27 #include <openssl/hmac.h>
  28
  29 #include <zlib.h>
  30 #include LZO1X_H
  31
  32 #include "avl_tree.h"
  33 #include "conf.h"
  34 #include "connection.h"
  35 #include "device.h"
  36 #include "ethernet.h"
  37 #include "event.h"
  38 #include "graph.h"
  39 #include "list.h"
  40 #include "logger.h"
  41 #include "net.h"
  42 #include "netutl.h"
  43 #include "protocol.h"
  44 #include "process.h"
  45 #include "route.h"
  46 #include "utils.h"
  47 #include "xalloc.h"
  48
  49 #ifdef WSAEMSGSIZE
  50 #define EMSGSIZE WSAEMSGSIZE
  51 #endif
  52
  53 int keylifetime = 0;
  54 int keyexpires = 0;
  55 static char lzo_wrkmem[LZO1X_999_MEM_COMPRESS > LZO1X_1_MEM_COMPRESS ? LZO1X_999_MEM_COMPRESS : LZO1X_1_MEM_COMPRESS];
  56
  57 static void send_udppacket(node_t *, vpn_packet_t *);
  58
  59 #define MAX_SEQNO 1073741824
  60
  61 void send_mtu_probe(node_t *n) {
  62         vpn_packet_t packet;
  63         int len, i;
  64
  65         cp();
  66
  67         n->mtuprobes++;
  68         n->mtuevent = NULL;
  69
  70         if(!n->status.reachable) {
  71                 logger(LOG_DEBUG, _("Trying to send MTU probe to unreachable node %s (%s)"), n->name, n->hostname);
  72                 return;
  73         }
  74
  75         if(n->mtuprobes >= 10 && !n->minmtu) {
  76                 ifdebug(TRAFFIC) logger(LOG_INFO, _("No response to MTU probes from %s (%s)"), n->name, n->hostname);
  77                 return;
  78         }
  79
  80         for(i = 0; i < 3; i++) {
  81                 if(n->mtuprobes >= 30 || n->minmtu >= n->maxmtu) {
  82                         n->mtu = n->minmtu;
  83                         ifdebug(TRAFFIC) logger(LOG_INFO, _("Fixing MTU of %s (%s) to %d after %d probes"), n->name, n->hostname, n->mtu, n->mtuprobes);
  84                         return;
  85                 }
  86
  87                 len = n->minmtu + 1 + rand() % (n->maxmtu - n->minmtu);
  88                 if(len < 64)
  89                         len = 64;
  90
  91                 memset(packet.data, 0, 14);
  92                 RAND_pseudo_bytes(packet.data + 14, len - 14);
  93                 packet.len = len;
  94                 packet.priority = 0;
  95
  96                 ifdebug(TRAFFIC) logger(LOG_INFO, _("Sending MTU probe length %d to %s (%s)"), len, n->name, n->hostname);
  97
  98                 send_udppacket(n, &packet);
  99         }
 100
 101         n->mtuevent = new_event();
 102         n->mtuevent->handler = (event_handler_t)send_mtu_probe;
 103         n->mtuevent->data = n;
 104         n->mtuevent->time = now + 1;
 105         event_add(n->mtuevent);
 106 }
 107
 108 void mtu_probe_h(node_t *n, vpn_packet_t *packet, length_t len) {
 109         ifdebug(TRAFFIC) logger(LOG_INFO, _("Got MTU probe length %d from %s (%s)"), packet->len, n->name, n->hostname);
 110
 111         if(!packet->data[0]) {
 112                 packet->data[0] = 1;
 113                 send_packet(n, packet);
 114         } else {
 115                 if(n->minmtu < len)
 116                         n->minmtu = len;
 117         }
 118 }
 119
 120 static length_t compress_packet(uint8_t *dest, const uint8_t *source, length_t len, int level) {
 121         if(level == 10) {
 122                 lzo_uint lzolen = MAXSIZE;
 123                 lzo1x_1_compress(source, len, dest, &lzolen, lzo_wrkmem);
 124                 return lzolen;
 125         } else if(level < 10) {
 126                 unsigned long destlen = MAXSIZE;
 127                 if(compress2(dest, &destlen, source, len, level) == Z_OK)
 128                         return destlen;
 129                 else
 130                         return -1;
 131         } else {
 132                 lzo_uint lzolen = MAXSIZE;
 133                 lzo1x_999_compress(source, len, dest, &lzolen, lzo_wrkmem);
 134                 return lzolen;
 135         }
 136
 137         return -1;
 138 }
 139
 140 static length_t uncompress_packet(uint8_t *dest, const uint8_t *source, length_t len, int level) {
 141         if(level > 9) {
 142                 lzo_uint lzolen = MAXSIZE;
 143                 if(lzo1x_decompress_safe(source, len, dest, &lzolen, NULL) == LZO_E_OK)
 144                         return lzolen;
 145                 else
 146                         return -1;
 147         } else {
 148                 unsigned long destlen = MAXSIZE;
 149                 if(uncompress(dest, &destlen, source, len) == Z_OK)
 150                         return destlen;
 151                 else
 152                         return -1;
 153         }
 154
 155         return -1;
 156 }
 157
 158 /* VPN packet I/O */
 159
 160 static void receive_packet(node_t *n, vpn_packet_t *packet) {
 161         cp();
 162
 163         ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Received packet of %d bytes from %s (%s)"),
 164                            packet->len, n->name, n->hostname);
 165
 166         route(n, packet);
 167 }
 168
 169 static bool try_mac(const node_t *n, const vpn_packet_t *inpkt) {
 170         unsigned char hmac[EVP_MAX_MD_SIZE];
 171
 172         if(!n->indigest || !n->inmaclength || !n->inkey || inpkt->len < sizeof inpkt->seqno + n->inmaclength)
 173                 return false;
 174
 175         HMAC(n->indigest, n->inkey, n->inkeylength, (unsigned char *) &inpkt->seqno, inpkt->len - n->inmaclength, (unsigned char *)hmac, NULL);
 176
 177         return !memcmp(hmac, (char *) &inpkt->seqno + inpkt->len - n->inmaclength, n->inmaclength);
 178 }
 179
 180 static void receive_udppacket(node_t *n, vpn_packet_t *inpkt) {
 181         vpn_packet_t pkt1, pkt2;
 182         vpn_packet_t *pkt[] = { &pkt1, &pkt2, &pkt1, &pkt2 };
 183         int nextpkt = 0;
 184         vpn_packet_t *outpkt = pkt[0];
 185         int outlen, outpad;
 186         unsigned char hmac[EVP_MAX_MD_SIZE];
 187         int i;
 188
 189         cp();
 190
 191         if(!n->inkey) {
 192                 ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Got packet from %s (%s) but he hasn't got our key yet"),
 193                                         n->name, n->hostname);
 194                 return;
 195         }
 196
 197         /* Check packet length */
 198
 199         if(inpkt->len < sizeof(inpkt->seqno) + n->inmaclength) {
 200                 ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Got too short packet from %s (%s)"),
 201                                         n->name, n->hostname);
 202                 return;
 203         }
 204
 205         /* Check the message authentication code */
 206
 207         if(n->indigest && n->inmaclength) {
 208                 inpkt->len -= n->inmaclength;
 209                 HMAC(n->indigest, n->inkey, n->inkeylength,
 210                          (unsigned char *) &inpkt->seqno, inpkt->len, (unsigned char *)hmac, NULL);
 211
 212                 if(memcmp(hmac, (char *) &inpkt->seqno + inpkt->len, n->inmaclength)) {
 213                         ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Got unauthenticated packet from %s (%s)"),
 214                                            n->name, n->hostname);
 215                         return;
 216                 }
 217         }
 218
 219         /* Decrypt the packet */
 220
 221         if(n->incipher) {
 222                 outpkt = pkt[nextpkt++];
 223
 224                 if(!EVP_DecryptInit_ex(&n->inctx, NULL, NULL, NULL, NULL)
 225                                 || !EVP_DecryptUpdate(&n->inctx, (unsigned char *) &outpkt->seqno, &outlen,
 226                                         (unsigned char *) &inpkt->seqno, inpkt->len)
 227                                 || !EVP_DecryptFinal_ex(&n->inctx, (unsigned char *) &outpkt->seqno + outlen, &outpad)) {
 228                         ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Error decrypting packet from %s (%s): %s"),
 229                                                 n->name, n->hostname, ERR_error_string(ERR_get_error(), NULL));
 230                         return;
 231                 }
 232
 233                 outpkt->len = outlen + outpad;
 234                 inpkt = outpkt;
 235         }
 236
 237         /* Check the sequence number */
 238
 239         inpkt->len -= sizeof(inpkt->seqno);
 240         inpkt->seqno = ntohl(inpkt->seqno);
 241
 242         if(inpkt->seqno != n->received_seqno + 1) {
 243                 if(inpkt->seqno >= n->received_seqno + sizeof(n->late) * 8) {
 244                         logger(LOG_WARNING, _("Lost %d packets from %s (%s)"),
 245                                            inpkt->seqno - n->received_seqno - 1, n->name, n->hostname);
 246
 247                         memset(n->late, 0, sizeof(n->late));
 248                 } else if (inpkt->seqno <= n->received_seqno) {
 249                         if((n->received_seqno >= sizeof(n->late) * 8 && inpkt->seqno <= n->received_seqno - sizeof(n->late) * 8) || !(n->late[(inpkt->seqno / 8) % sizeof(n->late)] & (1 << inpkt->seqno % 8))) {
 250                                 logger(LOG_WARNING, _("Got late or replayed packet from %s (%s), seqno %d, last received %d"),
 251                                            n->name, n->hostname, inpkt->seqno, n->received_seqno);
 252                                 return;
 253                         }
 254                 } else {
 255                         for(i = n->received_seqno + 1; i < inpkt->seqno; i++)
 256                                 n->late[(i / 8) % sizeof(n->late)] |= 1 << i % 8;
 257                 }
 258         }
 259
 260         n->late[(inpkt->seqno / 8) % sizeof(n->late)] &= ~(1 << inpkt->seqno % 8);
 261
 262         if(inpkt->seqno > n->received_seqno)
 263                 n->received_seqno = inpkt->seqno;
 264
 265         if(n->received_seqno > MAX_SEQNO)
 266                 keyexpires = 0;
 267
 268         /* Decompress the packet */
 269
 270         length_t origlen = inpkt->len;
 271
 272         if(n->incompression) {
 273                 outpkt = pkt[nextpkt++];
 274
 275                 if((outpkt->len = uncompress_packet(outpkt->data, inpkt->data, inpkt->len, n->incompression)) < 0) {
 276                         ifdebug(TRAFFIC) logger(LOG_ERR, _("Error while uncompressing packet from %s (%s)"),
 277                                                  n->name, n->hostname);
 278                         return;
 279                 }
 280
 281                 inpkt = outpkt;
 282
 283                 origlen -= MTU/64 + 20;
 284         }
 285
 286         inpkt->priority = 0;
 287
 288         if(n->connection)
 289                 n->connection->last_ping_time = now;
 290
 291         if(!inpkt->data[12] && !inpkt->data[13])
 292                 mtu_probe_h(n, inpkt, origlen);
 293         else
 294                 receive_packet(n, inpkt);
 295 }
 296
 297 void receive_tcppacket(connection_t *c, char *buffer, int len) {
 298         vpn_packet_t outpkt;
 299
 300         cp();
 301
 302         outpkt.len = len;
 303         if(c->options & OPTION_TCPONLY)
 304                 outpkt.priority = 0;
 305         else
 306                 outpkt.priority = -1;
 307         memcpy(outpkt.data, buffer, len);
 308
 309         receive_packet(c->node, &outpkt);
 310 }
 311
 312 static void send_udppacket(node_t *n, vpn_packet_t *origpkt) {
 313         vpn_packet_t pkt1, pkt2;
 314         vpn_packet_t *pkt[] = { &pkt1, &pkt2, &pkt1, &pkt2 };
 315         vpn_packet_t *inpkt = origpkt;
 316         int nextpkt = 0;
 317         vpn_packet_t *outpkt;
 318         int origlen;
 319         int outlen, outpad;
 320         static int priority = 0;
 321         int origpriority;
 322         int sock;
 323
 324         cp();
 325
 326         if(!n->status.reachable) {
 327                 ifdebug(TRAFFIC) logger(LOG_INFO, _("Trying to send UDP packet to unreachable node %s (%s)"), n->name, n->hostname);
 328                 return;
 329         }
 330
 331         /* Make sure we have a valid key */
 332
 333         if(!n->status.validkey) {
 334                 ifdebug(TRAFFIC) logger(LOG_INFO,
 335                                    _("No valid key known yet for %s (%s), forwarding via TCP"),
 336                                    n->name, n->hostname);
 337
 338                 if(!n->status.waitingforkey)
 339                         send_req_key(n);
 340
 341                 n->status.waitingforkey = true;
 342
 343                 send_tcppacket(n->nexthop->connection, origpkt);
 344
 345                 return;
 346         }
 347
 348         if(n->options & OPTION_PMTU_DISCOVERY && inpkt->len > n->minmtu && (inpkt->data[12] | inpkt->data[13])) {
 349                 ifdebug(TRAFFIC) logger(LOG_INFO,
 350                                 _("Packet for %s (%s) larger than minimum MTU, forwarding via TCP"),
 351                                 n->name, n->hostname);
 352
 353                 send_tcppacket(n->nexthop->connection, origpkt);
 354
 355                 return;
 356         }
 357
 358         origlen = inpkt->len;
 359         origpriority = inpkt->priority;
 360
 361         /* Compress the packet */
 362
 363         if(n->outcompression) {
 364                 outpkt = pkt[nextpkt++];
 365
 366                 if((outpkt->len = compress_packet(outpkt->data, inpkt->data, inpkt->len, n->outcompression)) < 0) {
 367                         ifdebug(TRAFFIC) logger(LOG_ERR, _("Error while compressing packet to %s (%s)"),
 368                                    n->name, n->hostname);
 369                         return;
 370                 }
 371
 372                 inpkt = outpkt;
 373         }
 374
 375         /* Add sequence number */
 376
 377         inpkt->seqno = htonl(++(n->sent_seqno));
 378         inpkt->len += sizeof(inpkt->seqno);
 379
 380         /* Encrypt the packet */
 381
 382         if(n->outcipher) {
 383                 outpkt = pkt[nextpkt++];
 384
 385                 if(!EVP_EncryptInit_ex(&n->outctx, NULL, NULL, NULL, NULL)
 386                                 || !EVP_EncryptUpdate(&n->outctx, (unsigned char *) &outpkt->seqno, &outlen,
 387                                         (unsigned char *) &inpkt->seqno, inpkt->len)
 388                                 || !EVP_EncryptFinal_ex(&n->outctx, (unsigned char *) &outpkt->seqno + outlen, &outpad)) {
 389                         ifdebug(TRAFFIC) logger(LOG_ERR, _("Error while encrypting packet to %s (%s): %s"),
 390                                                 n->name, n->hostname, ERR_error_string(ERR_get_error(), NULL));
 391                         goto end;
 392                 }
 393
 394                 outpkt->len = outlen + outpad;
 395                 inpkt = outpkt;
 396         }
 397
 398         /* Add the message authentication code */
 399
 400         if(n->outdigest && n->outmaclength) {
 401                 HMAC(n->outdigest, n->outkey, n->outkeylength, (unsigned char *) &inpkt->seqno,
 402                          inpkt->len, (unsigned char *) &inpkt->seqno + inpkt->len, NULL);
 403                 inpkt->len += n->outmaclength;
 404         }
 405
 406         /* Determine which socket we have to use */
 407
 408         for(sock = 0; sock < listen_sockets; sock++)
 409                 if(n->address.sa.sa_family == listen_socket[sock].sa.sa.sa_family)
 410                         break;
 411
 412         if(sock >= listen_sockets)
 413                 sock = 0;                               /* If none is available, just use the first and hope for the best. */
 414
 415         /* Send the packet */
 416
 417 #if defined(SOL_IP) && defined(IP_TOS)
 418         if(priorityinheritance && origpriority != priority
 419            && listen_socket[sock].sa.sa.sa_family == AF_INET) {
 420                 priority = origpriority;
 421                 ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Setting outgoing packet priority to %d"), priority);
 422                 if(setsockopt(listen_socket[sock].udp, SOL_IP, IP_TOS, &priority, sizeof(priority)))    /* SO_PRIORITY doesn't seem to work */
 423                         logger(LOG_ERR, _("System call `%s' failed: %s"), "setsockopt", strerror(errno));
 424         }
 425 #endif
 426
 427         if((sendto(listen_socket[sock].udp, (char *) &inpkt->seqno, inpkt->len, 0, &(n->address.sa), SALEN(n->address.sa))) < 0) {
 428                 if(errno == EMSGSIZE) {
 429                         if(n->maxmtu >= origlen)
 430                                 n->maxmtu = origlen - 1;
 431                         if(n->mtu >= origlen)
 432                                 n->mtu = origlen - 1;
 433                 } else
 434                         logger(LOG_ERR, _("Error sending packet to %s (%s): %s"), n->name, n->hostname, strerror(errno));
 435         }
 436
 437 end:
 438         origpkt->len = origlen;
 439 }
 440
 441 /*
 442   send a packet to the given vpn ip.
 443 */
 444 void send_packet(const node_t *n, vpn_packet_t *packet) {
 445         node_t *via;
 446
 447         cp();
 448
 449         if(n == myself) {
 450                 if(overwrite_mac)
 451                          memcpy(packet->data, mymac.x, ETH_ALEN);
 452                 write_packet(packet);
 453                 return;
 454         }
 455
 456         ifdebug(TRAFFIC) logger(LOG_ERR, _("Sending packet of %d bytes to %s (%s)"),
 457                            packet->len, n->name, n->hostname);
 458
 459         if(!n->status.reachable) {
 460                 ifdebug(TRAFFIC) logger(LOG_INFO, _("Node %s (%s) is not reachable"),
 461                                    n->name, n->hostname);
 462                 return;
 463         }
 464
 465         via = (packet->priority == -1 || n->via == myself) ? n->nexthop : n->via;
 466
 467         if(via != n)
 468                 ifdebug(TRAFFIC) logger(LOG_INFO, _("Sending packet to %s via %s (%s)"),
 469                            n->name, via->name, n->via->hostname);
 470
 471         if(packet->priority == -1 || ((myself->options | via->options) & OPTION_TCPONLY)) {
 472                 if(!send_tcppacket(via->connection, packet))
 473                         terminate_connection(via->connection, true);
 474         } else
 475                 send_udppacket(via, packet);
 476 }
 477
 478 /* Broadcast a packet using the minimum spanning tree */
 479
 480 void broadcast_packet(const node_t *from, vpn_packet_t *packet) {
 481         avl_node_t *node;
 482         connection_t *c;
 483
 484         cp();
 485
 486         ifdebug(TRAFFIC) logger(LOG_INFO, _("Broadcasting packet of %d bytes from %s (%s)"),
 487                            packet->len, from->name, from->hostname);
 488
 489         if(from != myself) {
 490                 send_packet(myself, packet);
 491
 492                 // In TunnelServer mode, do not forward broadcast packets.
 493                 // The MST might not be valid and create loops.
 494                 if(tunnelserver)
 495                         return;
 496         }
 497
 498         for(node = connection_tree->head; node; node = node->next) {
 499                 c = node->data;
 500
 501                 if(c->status.active && c->status.mst && c != from->nexthop->connection)
 502                         send_packet(c->node, packet);
 503         }
 504 }
 505
 506 static node_t *try_harder(const sockaddr_t *from, const vpn_packet_t *pkt) {
 507         avl_node_t *node;
 508         edge_t *e;
 509         node_t *n = NULL;
 510
 511         for(node = edge_weight_tree->head; node; node = node->next) {
 512                 e = node->data;
 513
 514                 if(sockaddrcmp_noport(from, &e->address))
 515                         continue;
 516
 517                 if(!n)
 518                         n = e->to;
 519
 520                 if(!try_mac(e->to, pkt))
 521                         continue;
 522
 523                 n = e->to;
 524                 break;
 525         }
 526
 527         return n;
 528 }
 529
 530 void handle_incoming_vpn_data(int sock) {
 531         vpn_packet_t pkt;
 532         char *hostname;
 533         sockaddr_t from;
 534         socklen_t fromlen = sizeof(from);
 535         node_t *n;
 536
 537         cp();
 538
 539         pkt.len = recvfrom(sock, (char *) &pkt.seqno, MAXSIZE, 0, &from.sa, &fromlen);
 540
 541         if(pkt.len < 0) {
 542                 if(errno != EAGAIN && errno != EINTR)
 543                         logger(LOG_ERR, _("Receiving packet failed: %s"), strerror(errno));
 544                 return;
 545         }
 546
 547         sockaddrunmap(&from);           /* Some braindead IPv6 implementations do stupid things. */
 548
 549         n = lookup_node_udp(&from);
 550
 551         if(!n) {
 552                 n = try_harder(&from, &pkt);
 553                 if(n)
 554                         update_node_udp(n, &from);
 555                 else ifdebug(PROTOCOL) {
 556                         hostname = sockaddr2hostname(&from);
 557                         logger(LOG_WARNING, _("Received UDP packet from unknown source %s"), hostname);
 558                         free(hostname);
 559                         return;
 560                 }
 561                 else
 562                         return;
 563         }
 564
 565         receive_udppacket(n, &pkt);
 566 }