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
  17     along with this program; if not, write to the Free Software
  18     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  19
  20     $Id$
  21 */
  22
  23 #include "system.h"
  24
  25 #include <openssl/rand.h>
  26 #include <openssl/err.h>
  27 #include <openssl/evp.h>
  28 #include <openssl/pem.h>
  29 #include <openssl/hmac.h>
  30
  31 #include <zlib.h>
  32 #include LZO1X_H
  33
  34 #include "avl_tree.h"
  35 #include "conf.h"
  36 #include "connection.h"
  37 #include "device.h"
  38 #include "ethernet.h"
  39 #include "event.h"
  40 #include "graph.h"
  41 #include "list.h"
  42 #include "logger.h"
  43 #include "net.h"
  44 #include "netutl.h"
  45 #include "protocol.h"
  46 #include "process.h"
  47 #include "route.h"
  48 #include "utils.h"
  49 #include "xalloc.h"
  50
  51 #ifdef WSAEMSGSIZE
  52 #define EMSGSIZE WSAEMSGSIZE
  53 #endif
  54
  55 int keylifetime = 0;
  56 int keyexpires = 0;
  57 static char lzo_wrkmem[LZO1X_999_MEM_COMPRESS > LZO1X_1_MEM_COMPRESS ? LZO1X_999_MEM_COMPRESS : LZO1X_1_MEM_COMPRESS];
  58
  59 static void send_udppacket(node_t *, vpn_packet_t *);
  60
  61 #define MAX_SEQNO 1073741824
  62
  63 void send_mtu_probe(node_t *n)
  64 {
  65         vpn_packet_t packet;
  66         int len, i;
  67
  68         cp();
  69
  70         n->mtuprobes++;
  71         n->mtuevent = NULL;
  72
  73         if(!n->status.reachable) {
  74                 logger(LOG_DEBUG, _("Trying to send MTU probe to unreachable node %s (%s)"), n->name, n->hostname);
  75                 return;
  76         }
  77
  78         if(n->mtuprobes >= 10 && !n->minmtu) {
  79                 ifdebug(TRAFFIC) logger(LOG_INFO, _("No response to MTU probes from %s (%s)"), n->name, n->hostname);
  80                 return;
  81         }
  82
  83         for(i = 0; i < 3; i++) {
  84                 if(n->mtuprobes >= 30 || n->minmtu >= n->maxmtu) {
  85                         n->mtu = n->minmtu;
  86                         ifdebug(TRAFFIC) logger(LOG_INFO, _("Fixing MTU of %s (%s) to %d after %d probes"), n->name, n->hostname, n->mtu, n->mtuprobes);
  87                         return;
  88                 }
  89
  90                 len = n->minmtu + 1 + rand() % (n->maxmtu - n->minmtu);
  91                 if(len < 64)
  92                         len = 64;
  93
  94                 memset(packet.data, 0, 14);
  95                 RAND_pseudo_bytes(packet.data + 14, len - 14);
  96                 packet.len = len;
  97                 packet.priority = 0;
  98
  99                 ifdebug(TRAFFIC) logger(LOG_INFO, _("Sending MTU probe length %d to %s (%s)"), len, n->name, n->hostname);
 100
 101                 send_udppacket(n, &packet);
 102         }
 103
 104         n->mtuevent = new_event();
 105         n->mtuevent->handler = (event_handler_t)send_mtu_probe;
 106         n->mtuevent->data = n;
 107         n->mtuevent->time = now + 1;
 108         event_add(n->mtuevent);
 109 }
 110
 111 void mtu_probe_h(node_t *n, vpn_packet_t *packet, length_t len) {
 112         ifdebug(TRAFFIC) logger(LOG_INFO, _("Got MTU probe length %d from %s (%s)"), packet->len, n->name, n->hostname);
 113
 114         if(!packet->data[0]) {
 115                 packet->data[0] = 1;
 116                 send_packet(n, packet);
 117         } else {
 118                 if(n->minmtu < len)
 119                         n->minmtu = len;
 120         }
 121 }
 122
 123 static length_t compress_packet(uint8_t *dest, const uint8_t *source, length_t len, int level)
 124 {
 125         if(level == 10) {
 126                 lzo_uint lzolen = MAXSIZE;
 127                 lzo1x_1_compress(source, len, dest, &lzolen, lzo_wrkmem);
 128                 return lzolen;
 129         } else if(level < 10) {
 130                 unsigned long destlen = MAXSIZE;
 131                 if(compress2(dest, &destlen, source, len, level) == Z_OK)
 132                         return destlen;
 133                 else
 134                         return -1;
 135         } else {
 136                 lzo_uint lzolen = MAXSIZE;
 137                 lzo1x_999_compress(source, len, dest, &lzolen, lzo_wrkmem);
 138                 return lzolen;
 139         }
 140
 141         return -1;
 142 }
 143
 144 static length_t uncompress_packet(uint8_t *dest, const uint8_t *source, length_t len, int level)
 145 {
 146         if(level > 9) {
 147                 lzo_uint lzolen = MAXSIZE;
 148                 if(lzo1x_decompress_safe(source, len, dest, &lzolen, NULL) == LZO_E_OK)
 149                         return lzolen;
 150                 else
 151                         return -1;
 152         } else {
 153                 unsigned long destlen = MAXSIZE;
 154                 if(uncompress(dest, &destlen, source, len) == Z_OK)
 155                         return destlen;
 156                 else
 157                         return -1;
 158         }
 159
 160         return -1;
 161 }
 162
 163 /* VPN packet I/O */
 164
 165 static void receive_packet(node_t *n, vpn_packet_t *packet)
 166 {
 167         cp();
 168
 169         ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Received packet of %d bytes from %s (%s)"),
 170                            packet->len, n->name, n->hostname);
 171
 172         route(n, packet);
 173 }
 174
 175 static bool try_mac(const node_t *n, const vpn_packet_t *inpkt)
 176 {
 177         unsigned char hmac[EVP_MAX_MD_SIZE];
 178
 179         if(!n->indigest || !n->inmaclength || !n->inkey || inpkt->len < sizeof inpkt->seqno + n->inmaclength)
 180                 return false;
 181
 182         HMAC(n->indigest, n->inkey, n->inkeylength, (unsigned char *) &inpkt->seqno, inpkt->len - n->inmaclength, (unsigned char *)hmac, NULL);
 183
 184         return !memcmp(hmac, (char *) &inpkt->seqno + inpkt->len - n->inmaclength, n->inmaclength);
 185 }
 186
 187 static void receive_udppacket(node_t *n, vpn_packet_t *inpkt)
 188 {
 189         vpn_packet_t pkt1, pkt2;
 190         vpn_packet_t *pkt[] = { &pkt1, &pkt2, &pkt1, &pkt2 };
 191         int nextpkt = 0;
 192         vpn_packet_t *outpkt = pkt[0];
 193         int outlen, outpad;
 194         unsigned char hmac[EVP_MAX_MD_SIZE];
 195         int i;
 196
 197         cp();
 198
 199         if(!n->inkey) {
 200                 ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Got packet from %s (%s) but he hasn't got our key yet"),
 201                                         n->name, n->hostname);
 202                 return;
 203         }
 204
 205         /* Check packet length */
 206
 207         if(inpkt->len < sizeof(inpkt->seqno) + n->inmaclength) {
 208                 ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Got too short packet from %s (%s)"),
 209                                         n->name, n->hostname);
 210                 return;
 211         }
 212
 213         /* Check the message authentication code */
 214
 215         if(n->indigest && n->inmaclength) {
 216                 inpkt->len -= n->inmaclength;
 217                 HMAC(n->indigest, n->inkey, n->inkeylength,
 218                          (unsigned char *) &inpkt->seqno, inpkt->len, (unsigned char *)hmac, NULL);
 219
 220                 if(memcmp(hmac, (char *) &inpkt->seqno + inpkt->len, n->inmaclength)) {
 221                         ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Got unauthenticated packet from %s (%s)"),
 222                                            n->name, n->hostname);
 223                         return;
 224                 }
 225         }
 226
 227         /* Decrypt the packet */
 228
 229         if(n->incipher) {
 230                 outpkt = pkt[nextpkt++];
 231
 232                 if(!EVP_DecryptInit_ex(&n->inctx, NULL, NULL, NULL, NULL)
 233                                 || !EVP_DecryptUpdate(&n->inctx, (unsigned char *) &outpkt->seqno, &outlen,
 234                                         (unsigned char *) &inpkt->seqno, inpkt->len)
 235                                 || !EVP_DecryptFinal_ex(&n->inctx, (unsigned char *) &outpkt->seqno + outlen, &outpad)) {
 236                         ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Error decrypting packet from %s (%s): %s"),
 237                                                 n->name, n->hostname, ERR_error_string(ERR_get_error(), NULL));
 238                         return;
 239                 }
 240
 241                 outpkt->len = outlen + outpad;
 242                 inpkt = outpkt;
 243         }
 244
 245         /* Check the sequence number */
 246
 247         inpkt->len -= sizeof(inpkt->seqno);
 248         inpkt->seqno = ntohl(inpkt->seqno);
 249
 250         if(inpkt->seqno != n->received_seqno + 1) {
 251                 if(inpkt->seqno >= n->received_seqno + sizeof(n->late) * 8) {
 252                         logger(LOG_WARNING, _("Lost %d packets from %s (%s)"),
 253                                            inpkt->seqno - n->received_seqno - 1, n->name, n->hostname);
 254
 255                         memset(n->late, 0, sizeof(n->late));
 256                 } else if (inpkt->seqno <= n->received_seqno) {
 257                         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))) {
 258                                 logger(LOG_WARNING, _("Got late or replayed packet from %s (%s), seqno %d, last received %d"),
 259                                            n->name, n->hostname, inpkt->seqno, n->received_seqno);
 260                                 return;
 261                         }
 262                 } else {
 263                         for(i = n->received_seqno + 1; i < inpkt->seqno; i++)
 264                                 n->late[(i / 8) % sizeof(n->late)] |= 1 << i % 8;
 265                 }
 266         }
 267
 268         n->late[(inpkt->seqno / 8) % sizeof(n->late)] &= ~(1 << inpkt->seqno % 8);
 269
 270         if(inpkt->seqno > n->received_seqno)
 271                 n->received_seqno = inpkt->seqno;
 272
 273         if(n->received_seqno > MAX_SEQNO)
 274                 keyexpires = 0;
 275
 276         /* Decompress the packet */
 277
 278         length_t origlen = inpkt->len;
 279
 280         if(n->incompression) {
 281                 outpkt = pkt[nextpkt++];
 282
 283                 if((outpkt->len = uncompress_packet(outpkt->data, inpkt->data, inpkt->len, n->incompression)) < 0) {
 284                         ifdebug(TRAFFIC) logger(LOG_ERR, _("Error while uncompressing packet from %s (%s)"),
 285                                                  n->name, n->hostname);
 286                         return;
 287                 }
 288
 289                 inpkt = outpkt;
 290
 291                 origlen -= MTU/64 + 20;
 292         }
 293
 294         inpkt->priority = 0;
 295
 296         if(n->connection)
 297                 n->connection->last_ping_time = now;
 298
 299         if(!inpkt->data[12] && !inpkt->data[13])
 300                 mtu_probe_h(n, inpkt, origlen);
 301         else
 302                 receive_packet(n, inpkt);
 303 }
 304
 305 void receive_tcppacket(connection_t *c, char *buffer, int len)
 306 {
 307         vpn_packet_t outpkt;
 308
 309         cp();
 310
 311         outpkt.len = len;
 312         if(c->options & OPTION_TCPONLY)
 313                 outpkt.priority = 0;
 314         else
 315                 outpkt.priority = -1;
 316         memcpy(outpkt.data, buffer, len);
 317
 318         receive_packet(c->node, &outpkt);
 319 }
 320
 321 static void send_udppacket(node_t *n, vpn_packet_t *origpkt)
 322 {
 323         vpn_packet_t pkt1, pkt2;
 324         vpn_packet_t *pkt[] = { &pkt1, &pkt2, &pkt1, &pkt2 };
 325         vpn_packet_t *inpkt = origpkt;
 326         int nextpkt = 0;
 327         vpn_packet_t *outpkt;
 328         int origlen;
 329         int outlen, outpad;
 330         static int priority = 0;
 331         int origpriority;
 332         int sock;
 333
 334         cp();
 335
 336         if(!n->status.reachable) {
 337                 ifdebug(TRAFFIC) logger(LOG_INFO, _("Trying to send UDP packet to unreachable node %s (%s)"), n->name, n->hostname);
 338                 return;
 339         }
 340
 341         /* Make sure we have a valid key */
 342
 343         if(!n->status.validkey) {
 344                 ifdebug(TRAFFIC) logger(LOG_INFO,
 345                                    _("No valid key known yet for %s (%s), forwarding via TCP"),
 346                                    n->name, n->hostname);
 347
 348                 if(!n->status.waitingforkey)
 349                         send_req_key(n);
 350
 351                 n->status.waitingforkey = true;
 352
 353                 send_tcppacket(n->nexthop->connection, origpkt);
 354
 355                 return;
 356         }
 357
 358         if(n->options & OPTION_PMTU_DISCOVERY && !n->minmtu && (inpkt->data[12] | inpkt->data[13])) {
 359                 ifdebug(TRAFFIC) logger(LOG_INFO,
 360                                 _("No minimum MTU established yet for %s (%s), forwarding via TCP"),
 361                                 n->name, n->hostname);
 362
 363                 send_tcppacket(n->nexthop->connection, origpkt);
 364
 365                 return;
 366         }
 367
 368         origlen = inpkt->len;
 369         origpriority = inpkt->priority;
 370
 371         /* Compress the packet */
 372
 373         if(n->outcompression) {
 374                 outpkt = pkt[nextpkt++];
 375
 376                 if((outpkt->len = compress_packet(outpkt->data, inpkt->data, inpkt->len, n->outcompression)) < 0) {
 377                         ifdebug(TRAFFIC) logger(LOG_ERR, _("Error while compressing packet to %s (%s)"),
 378                                    n->name, n->hostname);
 379                         return;
 380                 }
 381
 382                 inpkt = outpkt;
 383         }
 384
 385         /* Add sequence number */
 386
 387         inpkt->seqno = htonl(++(n->sent_seqno));
 388         inpkt->len += sizeof(inpkt->seqno);
 389
 390         /* Encrypt the packet */
 391
 392         if(n->outcipher) {
 393                 outpkt = pkt[nextpkt++];
 394
 395                 if(!EVP_EncryptInit_ex(&n->outctx, NULL, NULL, NULL, NULL)
 396                                 || !EVP_EncryptUpdate(&n->outctx, (unsigned char *) &outpkt->seqno, &outlen,
 397                                         (unsigned char *) &inpkt->seqno, inpkt->len)
 398                                 || !EVP_EncryptFinal_ex(&n->outctx, (unsigned char *) &outpkt->seqno + outlen, &outpad)) {
 399                         ifdebug(TRAFFIC) logger(LOG_ERR, _("Error while encrypting packet to %s (%s): %s"),
 400                                                 n->name, n->hostname, ERR_error_string(ERR_get_error(), NULL));
 401                         goto end;
 402                 }
 403
 404                 outpkt->len = outlen + outpad;
 405                 inpkt = outpkt;
 406         }
 407
 408         /* Add the message authentication code */
 409
 410         if(n->outdigest && n->outmaclength) {
 411                 HMAC(n->outdigest, n->outkey, n->outkeylength, (unsigned char *) &inpkt->seqno,
 412                          inpkt->len, (unsigned char *) &inpkt->seqno + inpkt->len, NULL);
 413                 inpkt->len += n->outmaclength;
 414         }
 415
 416         /* Determine which socket we have to use */
 417
 418         for(sock = 0; sock < listen_sockets; sock++)
 419                 if(n->address.sa.sa_family == listen_socket[sock].sa.sa.sa_family)
 420                         break;
 421
 422         if(sock >= listen_sockets)
 423                 sock = 0;                               /* If none is available, just use the first and hope for the best. */
 424
 425         /* Send the packet */
 426
 427 #if defined(SOL_IP) && defined(IP_TOS)
 428         if(priorityinheritance && origpriority != priority
 429            && listen_socket[sock].sa.sa.sa_family == AF_INET) {
 430                 priority = origpriority;
 431                 ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Setting outgoing packet priority to %d"), priority);
 432                 if(setsockopt(listen_socket[sock].udp, SOL_IP, IP_TOS, &priority, sizeof(priority)))    /* SO_PRIORITY doesn't seem to work */
 433                         logger(LOG_ERR, _("System call `%s' failed: %s"), "setsockopt", strerror(errno));
 434         }
 435 #endif
 436
 437         if((sendto(listen_socket[sock].udp, (char *) &inpkt->seqno, inpkt->len, 0, &(n->address.sa), SALEN(n->address.sa))) < 0) {
 438                 if(errno == EMSGSIZE) {
 439                         if(n->maxmtu >= origlen)
 440                                 n->maxmtu = origlen - 1;
 441                         if(n->mtu >= origlen)
 442                                 n->mtu = origlen - 1;
 443                 } else
 444                         logger(LOG_ERR, _("Error sending packet to %s (%s): %s"), n->name, n->hostname, strerror(errno));
 445         }
 446
 447 end:
 448         origpkt->len = origlen;
 449 }
 450
 451 /*
 452   send a packet to the given vpn ip.
 453 */
 454 void send_packet(const node_t *n, vpn_packet_t *packet)
 455 {
 456         node_t *via;
 457
 458         cp();
 459
 460         if(n == myself) {
 461                 if(overwrite_mac)
 462                          memcpy(packet->data, mymac.x, ETH_ALEN);
 463                 write_packet(packet);
 464                 return;
 465         }
 466
 467         ifdebug(TRAFFIC) logger(LOG_ERR, _("Sending packet of %d bytes to %s (%s)"),
 468                            packet->len, n->name, n->hostname);
 469
 470         if(!n->status.reachable) {
 471                 ifdebug(TRAFFIC) logger(LOG_INFO, _("Node %s (%s) is not reachable"),
 472                                    n->name, n->hostname);
 473                 return;
 474         }
 475
 476         via = (packet->priority == -1 || n->via == myself) ? n->nexthop : n->via;
 477
 478         if(via != n)
 479                 ifdebug(TRAFFIC) logger(LOG_INFO, _("Sending packet to %s via %s (%s)"),
 480                            n->name, via->name, n->via->hostname);
 481
 482         if(packet->priority == -1 || ((myself->options | via->options) & OPTION_TCPONLY)) {
 483                 if(!send_tcppacket(via->connection, packet))
 484                         terminate_connection(via->connection, true);
 485         } else
 486                 send_udppacket(via, packet);
 487 }
 488
 489 /* Broadcast a packet using the minimum spanning tree */
 490
 491 void broadcast_packet(const node_t *from, vpn_packet_t *packet)
 492 {
 493         avl_node_t *node;
 494         connection_t *c;
 495
 496         cp();
 497
 498         ifdebug(TRAFFIC) logger(LOG_INFO, _("Broadcasting packet of %d bytes from %s (%s)"),
 499                            packet->len, from->name, from->hostname);
 500
 501         if(from != myself) {
 502                 send_packet(myself, packet);
 503
 504                 // In TunnelServer mode, do not forward broadcast packets.
 505                 // The MST might not be valid and create loops.
 506                 if(tunnelserver)
 507                         return;
 508         }
 509
 510         for(node = connection_tree->head; node; node = node->next) {
 511                 c = node->data;
 512
 513                 if(c->status.active && c->status.mst && c != from->nexthop->connection)
 514                         send_packet(c->node, packet);
 515         }
 516 }
 517
 518 static node_t *try_harder(const sockaddr_t *from, const vpn_packet_t *pkt) {
 519         avl_node_t *node;
 520         edge_t *e;
 521         node_t *n = NULL;
 522
 523         for(node = edge_weight_tree->head; node; node = node->next) {
 524                 e = node->data;
 525
 526                 if(sockaddrcmp_noport(from, &e->address))
 527                         continue;
 528
 529                 if(!n)
 530                         n = e->to;
 531
 532                 if(!try_mac(e->to, pkt))
 533                         continue;
 534
 535                 n = e->to;
 536                 break;
 537         }
 538
 539         return n;
 540 }
 541
 542 void handle_incoming_vpn_data(int sock)
 543 {
 544         vpn_packet_t pkt;
 545         char *hostname;
 546         sockaddr_t from;
 547         socklen_t fromlen = sizeof(from);
 548         node_t *n;
 549
 550         cp();
 551
 552         pkt.len = recvfrom(sock, (char *) &pkt.seqno, MAXSIZE, 0, &from.sa, &fromlen);
 553
 554         if(pkt.len < 0) {
 555                 if(errno != EAGAIN && errno != EINTR)
 556                         logger(LOG_ERR, _("Receiving packet failed: %s"), strerror(errno));
 557                 return;
 558         }
 559
 560         sockaddrunmap(&from);           /* Some braindead IPv6 implementations do stupid things. */
 561
 562         n = lookup_node_udp(&from);
 563
 564         if(!n) {
 565                 n = try_harder(&from, &pkt);
 566                 if(n)
 567                         update_node_udp(n, &from);
 568                 else ifdebug(PROTOCOL) {
 569                         hostname = sockaddr2hostname(&from);
 570                         logger(LOG_WARNING, _("Received UDP packet from unknown source %s"), hostname);
 571                         free(hostname);
 572                         return;
 573                 }
 574                 else
 575                         return;
 576         }
 577
 578         receive_udppacket(n, &pkt);
 579 }