src/net_packet.c

   1 /*
   2     net_packet.c -- Handles in- and outgoing VPN packets
   3     Copyright (C) 1998-2005 Ivo Timmermans,
   4                   2000-2010 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
  31 #ifdef HAVE_LZO
  32 #include LZO1X_H
  33 #endif
  34
  35 #include "avl_tree.h"
  36 #include "conf.h"
  37 #include "connection.h"
  38 #include "device.h"
  39 #include "ethernet.h"
  40 #include "event.h"
  41 #include "graph.h"
  42 #include "list.h"
  43 #include "logger.h"
  44 #include "net.h"
  45 #include "netutl.h"
  46 #include "protocol.h"
  47 #include "process.h"
  48 #include "route.h"
  49 #include "utils.h"
  50 #include "xalloc.h"
  51
  52 int keylifetime = 0;
  53 int keyexpires = 0;
  54 #ifdef HAVE_LZO
  55 static char lzo_wrkmem[LZO1X_999_MEM_COMPRESS > LZO1X_1_MEM_COMPRESS ? LZO1X_999_MEM_COMPRESS : LZO1X_1_MEM_COMPRESS];
  56 #endif
  57
  58 static void send_udppacket(node_t *, vpn_packet_t *);
  59
  60 #define MAX_SEQNO 1073741824
  61
  62 // mtuprobes == 1..30: initial discovery, send bursts with 1 second interval
  63 // mtuprobes ==    31: sleep pinginterval seconds
  64 // mtuprobes ==    32: send 1 burst, sleep pingtimeout second
  65 // mtuprobes ==    33: no response from other side, restart PMTU discovery process
  66
  67 void send_mtu_probe(node_t *n) {
  68         vpn_packet_t packet;
  69         int len, i;
  70         int timeout = 1;
  71
  72         n->mtuprobes++;
  73         n->mtuevent = NULL;
  74
  75         if(!n->status.reachable || !n->status.validkey) {
  76                 ifdebug(TRAFFIC) logger(LOG_INFO, "Trying to send MTU probe to unreachable or rekeying node %s (%s)", n->name, n->hostname);
  77                 n->mtuprobes = 0;
  78                 return;
  79         }
  80
  81         if(n->mtuprobes > 32) {
  82                 ifdebug(TRAFFIC) logger(LOG_INFO, "%s (%s) did not respond to UDP ping, restarting PMTU discovery", n->name, n->hostname);
  83                 n->mtuprobes = 1;
  84                 n->minmtu = 0;
  85                 n->maxmtu = MTU;
  86         }
  87
  88         if(n->mtuprobes >= 10 && !n->minmtu) {
  89                 ifdebug(TRAFFIC) logger(LOG_INFO, "No response to MTU probes from %s (%s)", n->name, n->hostname);
  90                 n->mtuprobes = 0;
  91                 return;
  92         }
  93
  94         if(n->mtuprobes == 30 || (n->mtuprobes < 30 && n->minmtu >= n->maxmtu)) {
  95                 if(n->minmtu > n->maxmtu)
  96                         n->minmtu = n->maxmtu;
  97                 else
  98                         n->maxmtu = n->minmtu;
  99                 n->mtu = n->minmtu;
 100                 ifdebug(TRAFFIC) logger(LOG_INFO, "Fixing MTU of %s (%s) to %d after %d probes", n->name, n->hostname, n->mtu, n->mtuprobes);
 101                 n->mtuprobes = 31;
 102         }
 103
 104         if(n->mtuprobes == 31) {
 105                 timeout = pinginterval;
 106                 goto end;
 107         } else if(n->mtuprobes == 32) {
 108                 timeout = pingtimeout;
 109         }
 110
 111         for(i = 0; i < 3; i++) {
 112                 if(n->maxmtu <= n->minmtu)
 113                         len = n->maxmtu;
 114                 else
 115                         len = n->minmtu + 1 + rand() % (n->maxmtu - n->minmtu);
 116
 117                 if(len < 64)
 118                         len = 64;
 119
 120                 memset(packet.data, 0, 14);
 121                 RAND_pseudo_bytes(packet.data + 14, len - 14);
 122                 packet.len = len;
 123                 packet.priority = 0;
 124
 125                 ifdebug(TRAFFIC) logger(LOG_INFO, "Sending MTU probe length %d to %s (%s)", len, n->name, n->hostname);
 126
 127                 send_udppacket(n, &packet);
 128         }
 129
 130 end:
 131         n->mtuevent = new_event();
 132         n->mtuevent->handler = (event_handler_t)send_mtu_probe;
 133         n->mtuevent->data = n;
 134         n->mtuevent->time = now + timeout;
 135         event_add(n->mtuevent);
 136 }
 137
 138 void mtu_probe_h(node_t *n, vpn_packet_t *packet, length_t len) {
 139         ifdebug(TRAFFIC) logger(LOG_INFO, "Got MTU probe length %d from %s (%s)", packet->len, n->name, n->hostname);
 140
 141         if(!packet->data[0]) {
 142                 packet->data[0] = 1;
 143                 send_udppacket(n, packet);
 144         } else {
 145                 if(len > n->maxmtu)
 146                         len = n->maxmtu;
 147                 if(n->minmtu < len)
 148                         n->minmtu = len;
 149                 if(n->mtuprobes > 30)
 150                         n->mtuprobes = 30;
 151         }
 152 }
 153
 154 static length_t compress_packet(uint8_t *dest, const uint8_t *source, length_t len, int level) {
 155         if(level == 10) {
 156 #ifdef HAVE_LZO
 157                 lzo_uint lzolen = MAXSIZE;
 158                 lzo1x_1_compress(source, len, dest, &lzolen, lzo_wrkmem);
 159                 return lzolen;
 160 #else
 161                 return -1;
 162 #endif
 163         } else if(level < 10) {
 164                 unsigned long destlen = MAXSIZE;
 165                 if(compress2(dest, &destlen, source, len, level) == Z_OK)
 166                         return destlen;
 167                 else
 168                         return -1;
 169         } else {
 170 #ifdef HAVE_LZO
 171                 lzo_uint lzolen = MAXSIZE;
 172                 lzo1x_999_compress(source, len, dest, &lzolen, lzo_wrkmem);
 173                 return lzolen;
 174 #else
 175                 return -1;
 176 #endif
 177         }
 178
 179         return -1;
 180 }
 181
 182 static length_t uncompress_packet(uint8_t *dest, const uint8_t *source, length_t len, int level) {
 183         if(level > 9) {
 184 #ifdef HAVE_LZO
 185                 lzo_uint lzolen = MAXSIZE;
 186                 if(lzo1x_decompress_safe(source, len, dest, &lzolen, NULL) == LZO_E_OK)
 187                         return lzolen;
 188                 else
 189 #endif
 190                         return -1;
 191         } else {
 192                 unsigned long destlen = MAXSIZE;
 193                 if(uncompress(dest, &destlen, source, len) == Z_OK)
 194                         return destlen;
 195                 else
 196                         return -1;
 197         }
 198
 199         return -1;
 200 }
 201
 202 /* VPN packet I/O */
 203
 204 static void receive_packet(node_t *n, vpn_packet_t *packet) {
 205         ifdebug(TRAFFIC) logger(LOG_DEBUG, "Received packet of %d bytes from %s (%s)",
 206                            packet->len, n->name, n->hostname);
 207
 208         route(n, packet);
 209 }
 210
 211 static bool try_mac(const node_t *n, const vpn_packet_t *inpkt) {
 212         unsigned char hmac[EVP_MAX_MD_SIZE];
 213
 214         if(!n->indigest || !n->inmaclength || !n->inkey || inpkt->len < sizeof inpkt->seqno + n->inmaclength)
 215                 return false;
 216
 217         HMAC(n->indigest, n->inkey, n->inkeylength, (unsigned char *) &inpkt->seqno, inpkt->len - n->inmaclength, (unsigned char *)hmac, NULL);
 218
 219         return !memcmp(hmac, (char *) &inpkt->seqno + inpkt->len - n->inmaclength, n->inmaclength);
 220 }
 221
 222 static void receive_udppacket(node_t *n, vpn_packet_t *inpkt) {
 223         vpn_packet_t pkt1, pkt2;
 224         vpn_packet_t *pkt[] = { &pkt1, &pkt2, &pkt1, &pkt2 };
 225         int nextpkt = 0;
 226         vpn_packet_t *outpkt = pkt[0];
 227         int outlen, outpad;
 228         unsigned char hmac[EVP_MAX_MD_SIZE];
 229         int i;
 230
 231         if(!n->inkey) {
 232                 ifdebug(TRAFFIC) logger(LOG_DEBUG, "Got packet from %s (%s) but he hasn't got our key yet",
 233                                         n->name, n->hostname);
 234                 return;
 235         }
 236
 237         /* Check packet length */
 238
 239         if(inpkt->len < sizeof(inpkt->seqno) + n->inmaclength) {
 240                 ifdebug(TRAFFIC) logger(LOG_DEBUG, "Got too short packet from %s (%s)",
 241                                         n->name, n->hostname);
 242                 return;
 243         }
 244
 245         /* Check the message authentication code */
 246
 247         if(n->indigest && n->inmaclength) {
 248                 inpkt->len -= n->inmaclength;
 249                 HMAC(n->indigest, n->inkey, n->inkeylength,
 250                          (unsigned char *) &inpkt->seqno, inpkt->len, (unsigned char *)hmac, NULL);
 251
 252                 if(memcmp(hmac, (char *) &inpkt->seqno + inpkt->len, n->inmaclength)) {
 253                         ifdebug(TRAFFIC) logger(LOG_DEBUG, "Got unauthenticated packet from %s (%s)",
 254                                            n->name, n->hostname);
 255                         return;
 256                 }
 257         }
 258
 259         /* Decrypt the packet */
 260
 261         if(n->incipher) {
 262                 outpkt = pkt[nextpkt++];
 263
 264                 if(!EVP_DecryptInit_ex(&n->inctx, NULL, NULL, NULL, NULL)
 265                                 || !EVP_DecryptUpdate(&n->inctx, (unsigned char *) &outpkt->seqno, &outlen,
 266                                         (unsigned char *) &inpkt->seqno, inpkt->len)
 267                                 || !EVP_DecryptFinal_ex(&n->inctx, (unsigned char *) &outpkt->seqno + outlen, &outpad)) {
 268                         ifdebug(TRAFFIC) logger(LOG_DEBUG, "Error decrypting packet from %s (%s): %s",
 269                                                 n->name, n->hostname, ERR_error_string(ERR_get_error(), NULL));
 270                         return;
 271                 }
 272
 273                 outpkt->len = outlen + outpad;
 274                 inpkt = outpkt;
 275         }
 276
 277         /* Check the sequence number */
 278
 279         inpkt->len -= sizeof(inpkt->seqno);
 280         inpkt->seqno = ntohl(inpkt->seqno);
 281
 282         if(inpkt->seqno != n->received_seqno + 1) {
 283                 if(inpkt->seqno >= n->received_seqno + sizeof(n->late) * 8) {
 284                         logger(LOG_WARNING, "Lost %d packets from %s (%s)",
 285                                            inpkt->seqno - n->received_seqno - 1, n->name, n->hostname);
 286
 287                         memset(n->late, 0, sizeof(n->late));
 288                 } else if (inpkt->seqno <= n->received_seqno) {
 289                         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))) {
 290                                 logger(LOG_WARNING, "Got late or replayed packet from %s (%s), seqno %d, last received %d",
 291                                            n->name, n->hostname, inpkt->seqno, n->received_seqno);
 292                                 return;
 293                         }
 294                 } else {
 295                         for(i = n->received_seqno + 1; i < inpkt->seqno; i++)
 296                                 n->late[(i / 8) % sizeof(n->late)] |= 1 << i % 8;
 297                 }
 298         }
 299
 300         n->late[(inpkt->seqno / 8) % sizeof(n->late)] &= ~(1 << inpkt->seqno % 8);
 301
 302         if(inpkt->seqno > n->received_seqno)
 303                 n->received_seqno = inpkt->seqno;
 304
 305         if(n->received_seqno > MAX_SEQNO)
 306                 keyexpires = 0;
 307
 308         /* Decompress the packet */
 309
 310         length_t origlen = inpkt->len;
 311
 312         if(n->incompression) {
 313                 outpkt = pkt[nextpkt++];
 314
 315                 if((outpkt->len = uncompress_packet(outpkt->data, inpkt->data, inpkt->len, n->incompression)) < 0) {
 316                         ifdebug(TRAFFIC) logger(LOG_ERR, "Error while uncompressing packet from %s (%s)",
 317                                                  n->name, n->hostname);
 318                         return;
 319                 }
 320
 321                 inpkt = outpkt;
 322
 323                 origlen -= MTU/64 + 20;
 324         }
 325
 326         inpkt->priority = 0;
 327
 328         if(!inpkt->data[12] && !inpkt->data[13])
 329                 mtu_probe_h(n, inpkt, origlen);
 330         else
 331                 receive_packet(n, inpkt);
 332 }
 333
 334 void receive_tcppacket(connection_t *c, char *buffer, int len) {
 335         vpn_packet_t outpkt;
 336
 337         outpkt.len = len;
 338         if(c->options & OPTION_TCPONLY)
 339                 outpkt.priority = 0;
 340         else
 341                 outpkt.priority = -1;
 342         memcpy(outpkt.data, buffer, len);
 343
 344         receive_packet(c->node, &outpkt);
 345 }
 346
 347 static void send_udppacket(node_t *n, vpn_packet_t *origpkt) {
 348         vpn_packet_t pkt1, pkt2;
 349         vpn_packet_t *pkt[] = { &pkt1, &pkt2, &pkt1, &pkt2 };
 350         vpn_packet_t *inpkt = origpkt;
 351         int nextpkt = 0;
 352         vpn_packet_t *outpkt;
 353         int origlen;
 354         int outlen, outpad;
 355         static int priority = 0;
 356         int origpriority;
 357         int sock;
 358
 359         if(!n->status.reachable) {
 360                 ifdebug(TRAFFIC) logger(LOG_INFO, "Trying to send UDP packet to unreachable node %s (%s)", n->name, n->hostname);
 361                 return;
 362         }
 363
 364         /* Make sure we have a valid key */
 365
 366         if(!n->status.validkey) {
 367                 ifdebug(TRAFFIC) logger(LOG_INFO,
 368                                    "No valid key known yet for %s (%s), forwarding via TCP",
 369                                    n->name, n->hostname);
 370
 371                 if(n->last_req_key + 10 < now) {
 372                         send_req_key(n);
 373                         n->last_req_key = now;
 374                 }
 375
 376                 send_tcppacket(n->nexthop->connection, origpkt);
 377
 378                 return;
 379         }
 380
 381         if(n->options & OPTION_PMTU_DISCOVERY && inpkt->len > n->minmtu && (inpkt->data[12] | inpkt->data[13])) {
 382                 ifdebug(TRAFFIC) logger(LOG_INFO,
 383                                 "Packet for %s (%s) larger than minimum MTU, forwarding via %s",
 384                                 n->name, n->hostname, n != n->nexthop ? n->nexthop->name : "TCP");
 385
 386                 if(n != n->nexthop)
 387                         send_packet(n->nexthop, origpkt);
 388                 else
 389                         send_tcppacket(n->nexthop->connection, origpkt);
 390
 391                 return;
 392         }
 393
 394         origlen = inpkt->len;
 395         origpriority = inpkt->priority;
 396
 397         /* Compress the packet */
 398
 399         if(n->outcompression) {
 400                 outpkt = pkt[nextpkt++];
 401
 402                 if((outpkt->len = compress_packet(outpkt->data, inpkt->data, inpkt->len, n->outcompression)) < 0) {
 403                         ifdebug(TRAFFIC) logger(LOG_ERR, "Error while compressing packet to %s (%s)",
 404                                    n->name, n->hostname);
 405                         return;
 406                 }
 407
 408                 inpkt = outpkt;
 409         }
 410
 411         /* Add sequence number */
 412
 413         inpkt->seqno = htonl(++(n->sent_seqno));
 414         inpkt->len += sizeof(inpkt->seqno);
 415
 416         /* Encrypt the packet */
 417
 418         if(n->outcipher) {
 419                 outpkt = pkt[nextpkt++];
 420
 421                 if(!EVP_EncryptInit_ex(&n->outctx, NULL, NULL, NULL, NULL)
 422                                 || !EVP_EncryptUpdate(&n->outctx, (unsigned char *) &outpkt->seqno, &outlen,
 423                                         (unsigned char *) &inpkt->seqno, inpkt->len)
 424                                 || !EVP_EncryptFinal_ex(&n->outctx, (unsigned char *) &outpkt->seqno + outlen, &outpad)) {
 425                         ifdebug(TRAFFIC) logger(LOG_ERR, "Error while encrypting packet to %s (%s): %s",
 426                                                 n->name, n->hostname, ERR_error_string(ERR_get_error(), NULL));
 427                         goto end;
 428                 }
 429
 430                 outpkt->len = outlen + outpad;
 431                 inpkt = outpkt;
 432         }
 433
 434         /* Add the message authentication code */
 435
 436         if(n->outdigest && n->outmaclength) {
 437                 HMAC(n->outdigest, n->outkey, n->outkeylength, (unsigned char *) &inpkt->seqno,
 438                          inpkt->len, (unsigned char *) &inpkt->seqno + inpkt->len, NULL);
 439                 inpkt->len += n->outmaclength;
 440         }
 441
 442         /* Determine which socket we have to use */
 443
 444         for(sock = 0; sock < listen_sockets; sock++)
 445                 if(n->address.sa.sa_family == listen_socket[sock].sa.sa.sa_family)
 446                         break;
 447
 448         if(sock >= listen_sockets)
 449                 sock = 0;                               /* If none is available, just use the first and hope for the best. */
 450
 451         /* Send the packet */
 452
 453 #if defined(SOL_IP) && defined(IP_TOS)
 454         if(priorityinheritance && origpriority != priority
 455            && listen_socket[sock].sa.sa.sa_family == AF_INET) {
 456                 priority = origpriority;
 457                 ifdebug(TRAFFIC) logger(LOG_DEBUG, "Setting outgoing packet priority to %d", priority);
 458                 if(setsockopt(listen_socket[sock].udp, SOL_IP, IP_TOS, &priority, sizeof(priority)))    /* SO_PRIORITY doesn't seem to work */
 459                         logger(LOG_ERR, "System call `%s' failed: %s", "setsockopt", strerror(errno));
 460         }
 461 #endif
 462
 463         if(sendto(listen_socket[sock].udp, (char *) &inpkt->seqno, inpkt->len, 0, &(n->address.sa), SALEN(n->address.sa)) < 0 && !sockwouldblock(sockerrno)) {
 464                 if(sockmsgsize(sockerrno)) {
 465                         if(n->maxmtu >= origlen)
 466                                 n->maxmtu = origlen - 1;
 467                         if(n->mtu >= origlen)
 468                                 n->mtu = origlen - 1;
 469                 } else
 470                         logger(LOG_ERR, "Error sending packet to %s (%s): %s", n->name, n->hostname, sockstrerror(sockerrno));
 471         }
 472
 473 end:
 474         origpkt->len = origlen;
 475 }
 476
 477 /*
 478   send a packet to the given vpn ip.
 479 */
 480 void send_packet(const node_t *n, vpn_packet_t *packet) {
 481         node_t *via;
 482
 483         if(n == myself) {
 484                 if(overwrite_mac)
 485                          memcpy(packet->data, mymac.x, ETH_ALEN);
 486                 write_packet(packet);
 487                 return;
 488         }
 489
 490         ifdebug(TRAFFIC) logger(LOG_ERR, "Sending packet of %d bytes to %s (%s)",
 491                            packet->len, n->name, n->hostname);
 492
 493         if(!n->status.reachable) {
 494                 ifdebug(TRAFFIC) logger(LOG_INFO, "Node %s (%s) is not reachable",
 495                                    n->name, n->hostname);
 496                 return;
 497         }
 498
 499         via = (packet->priority == -1 || n->via == myself) ? n->nexthop : n->via;
 500
 501         if(via != n)
 502                 ifdebug(TRAFFIC) logger(LOG_INFO, "Sending packet to %s via %s (%s)",
 503                            n->name, via->name, n->via->hostname);
 504
 505         if(packet->priority == -1 || ((myself->options | via->options) & OPTION_TCPONLY)) {
 506                 if(!send_tcppacket(via->connection, packet))
 507                         terminate_connection(via->connection, true);
 508         } else
 509                 send_udppacket(via, packet);
 510 }
 511
 512 /* Broadcast a packet using the minimum spanning tree */
 513
 514 void broadcast_packet(const node_t *from, vpn_packet_t *packet) {
 515         avl_node_t *node;
 516         connection_t *c;
 517
 518         ifdebug(TRAFFIC) logger(LOG_INFO, "Broadcasting packet of %d bytes from %s (%s)",
 519                            packet->len, from->name, from->hostname);
 520
 521         if(from != myself) {
 522                 send_packet(myself, packet);
 523
 524                 // In TunnelServer mode, do not forward broadcast packets.
 525                 // The MST might not be valid and create loops.
 526                 if(tunnelserver)
 527                         return;
 528         }
 529
 530         for(node = connection_tree->head; node; node = node->next) {
 531                 c = node->data;
 532
 533                 if(c->status.active && c->status.mst && c != from->nexthop->connection)
 534                         send_packet(c->node, packet);
 535         }
 536 }
 537
 538 static node_t *try_harder(const sockaddr_t *from, const vpn_packet_t *pkt) {
 539         avl_node_t *node;
 540         edge_t *e;
 541         node_t *n = NULL;
 542         static time_t last_hard_try = 0;
 543
 544         for(node = edge_weight_tree->head; node; node = node->next) {
 545                 e = node->data;
 546
 547                 if(sockaddrcmp_noport(from, &e->address)) {
 548                         if(last_hard_try == now)
 549                                 continue;
 550                         last_hard_try = now;
 551                 }
 552
 553                 if(!n)
 554                         n = e->to;
 555
 556                 if(!try_mac(e->to, pkt))
 557                         continue;
 558
 559                 n = e->to;
 560                 break;
 561         }
 562
 563         return n;
 564 }
 565
 566 void handle_incoming_vpn_data(int sock) {
 567         vpn_packet_t pkt;
 568         char *hostname;
 569         sockaddr_t from;
 570         socklen_t fromlen = sizeof(from);
 571         node_t *n;
 572
 573         pkt.len = recvfrom(sock, (char *) &pkt.seqno, MAXSIZE, 0, &from.sa, &fromlen);
 574
 575         if(pkt.len < 0) {
 576                 if(!sockwouldblock(sockerrno))
 577                         logger(LOG_ERR, "Receiving packet failed: %s", sockstrerror(sockerrno));
 578                 return;
 579         }
 580
 581         sockaddrunmap(&from);           /* Some braindead IPv6 implementations do stupid things. */
 582
 583         n = lookup_node_udp(&from);
 584
 585         if(!n) {
 586                 n = try_harder(&from, &pkt);
 587                 if(n)
 588                         update_node_udp(n, &from);
 589                 else ifdebug(PROTOCOL) {
 590                         hostname = sockaddr2hostname(&from);
 591                         logger(LOG_WARNING, "Received UDP packet from unknown source %s", hostname);
 592                         free(hostname);
 593                         return;
 594                 }
 595                 else
 596                         return;
 597         }
 598
 599         receive_udppacket(n, &pkt);
 600 }