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 #ifdef HAVE_ZLIB
  30 #include <zlib.h>
  31 #endif
  32
  33 #ifdef HAVE_LZO
  34 #include LZO1X_H
  35 #endif
  36
  37 #include "splay_tree.h"
  38 #include "cipher.h"
  39 #include "conf.h"
  40 #include "connection.h"
  41 #include "crypto.h"
  42 #include "digest.h"
  43 #include "device.h"
  44 #include "ethernet.h"
  45 #include "graph.h"
  46 #include "list.h"
  47 #include "logger.h"
  48 #include "net.h"
  49 #include "netutl.h"
  50 #include "protocol.h"
  51 #include "process.h"
  52 #include "route.h"
  53 #include "utils.h"
  54 #include "xalloc.h"
  55
  56 int keylifetime = 0;
  57 int keyexpires = 0;
  58 #ifdef HAVE_LZO
  59 static char lzo_wrkmem[LZO1X_999_MEM_COMPRESS > LZO1X_1_MEM_COMPRESS ? LZO1X_999_MEM_COMPRESS : LZO1X_1_MEM_COMPRESS];
  60 #endif
  61
  62 static void send_udppacket(node_t *, vpn_packet_t *);
  63
  64 #define MAX_SEQNO 1073741824
  65
  66 // mtuprobes == 1..30: initial discovery, send bursts with 1 second interval
  67 // mtuprobes ==    31: sleep pinginterval seconds
  68 // mtuprobes ==    32: send 1 burst, sleep pingtimeout second
  69 // mtuprobes ==    33: no response from other side, restart PMTU discovery process
  70
  71 static void send_mtu_probe_handler(int fd, short events, void *data) {
  72         node_t *n = data;
  73         vpn_packet_t packet;
  74         int len, i;
  75         int timeout = 1;
  76
  77         n->mtuprobes++;
  78
  79         if(!n->status.reachable || !n->status.validkey) {
  80                 ifdebug(TRAFFIC) logger(LOG_INFO, "Trying to send MTU probe to unreachable or rekeying node %s (%s)", n->name, n->hostname);
  81                 n->mtuprobes = 0;
  82                 return;
  83         }
  84
  85         if(n->mtuprobes > 32) {
  86                 ifdebug(TRAFFIC) logger(LOG_INFO, "%s (%s) did not respond to UDP ping, restarting PMTU discovery", n->name, n->hostname);
  87                 n->mtuprobes = 1;
  88                 n->minmtu = 0;
  89                 n->maxmtu = MTU;
  90         }
  91
  92         if(n->mtuprobes >= 10 && !n->minmtu) {
  93                 ifdebug(TRAFFIC) logger(LOG_INFO, "No response to MTU probes from %s (%s)", n->name, n->hostname);
  94                 n->mtuprobes = 0;
  95                 return;
  96         }
  97
  98         if(n->mtuprobes == 30 || (n->mtuprobes < 30 && n->minmtu >= n->maxmtu)) {
  99                 if(n->minmtu > n->maxmtu)
 100                         n->minmtu = n->maxmtu;
 101                 else
 102                         n->maxmtu = n->minmtu;
 103                 n->mtu = n->minmtu;
 104                 ifdebug(TRAFFIC) logger(LOG_INFO, "Fixing MTU of %s (%s) to %d after %d probes", n->name, n->hostname, n->mtu, n->mtuprobes);
 105                 n->mtuprobes = 31;
 106         }
 107
 108         if(n->mtuprobes == 31) {
 109                 timeout = pinginterval;
 110                 goto end;
 111         } else if(n->mtuprobes == 32) {
 112                 timeout = pingtimeout;
 113         }
 114
 115         for(i = 0; i < 3; i++) {
 116                 if(n->maxmtu <= n->minmtu)
 117                         len = n->maxmtu;
 118                 else
 119                         len = n->minmtu + 1 + rand() % (n->maxmtu - n->minmtu);
 120
 121                 if(len < 64)
 122                         len = 64;
 123
 124                 memset(packet.data, 0, 14);
 125                 randomize(packet.data + 14, len - 14);
 126                 packet.len = len;
 127                 packet.priority = 0;
 128
 129                 ifdebug(TRAFFIC) logger(LOG_INFO, "Sending MTU probe length %d to %s (%s)", len, n->name, n->hostname);
 130
 131                 send_udppacket(n, &packet);
 132         }
 133
 134 end:
 135         event_add(&n->mtuevent, &(struct timeval){timeout, 0});
 136 }
 137
 138 void send_mtu_probe(node_t *n) {
 139         if(!timeout_initialized(&n->mtuevent))
 140                 timeout_set(&n->mtuevent, send_mtu_probe_handler, n);
 141         send_mtu_probe_handler(0, 0, n);
 142 }
 143
 144 void mtu_probe_h(node_t *n, vpn_packet_t *packet, length_t len) {
 145         ifdebug(TRAFFIC) logger(LOG_INFO, "Got MTU probe length %d from %s (%s)", packet->len, n->name, n->hostname);
 146
 147         if(!packet->data[0]) {
 148                 packet->data[0] = 1;
 149                 send_udppacket(n, packet);
 150         } else {
 151                 if(len > n->maxmtu)
 152                         len = n->maxmtu;
 153                 if(n->minmtu < len)
 154                         n->minmtu = len;
 155                 if(n->mtuprobes > 30)
 156                         n->mtuprobes = 30;
 157         }
 158 }
 159
 160 static length_t compress_packet(uint8_t *dest, const uint8_t *source, length_t len, int level) {
 161         if(level == 0) {
 162                 memcpy(dest, source, len);
 163                 return len;
 164         } else if(level == 10) {
 165 #ifdef HAVE_LZO
 166                 lzo_uint lzolen = MAXSIZE;
 167                 lzo1x_1_compress(source, len, dest, &lzolen, lzo_wrkmem);
 168                 return lzolen;
 169 #else
 170                 return -1;
 171 #endif
 172         } else if(level < 10) {
 173 #ifdef HAVE_ZLIB
 174                 unsigned long destlen = MAXSIZE;
 175                 if(compress2(dest, &destlen, source, len, level) == Z_OK)
 176                         return destlen;
 177                 else
 178 #endif
 179                         return -1;
 180         } else {
 181 #ifdef HAVE_LZO
 182                 lzo_uint lzolen = MAXSIZE;
 183                 lzo1x_999_compress(source, len, dest, &lzolen, lzo_wrkmem);
 184                 return lzolen;
 185 #else
 186                 return -1;
 187 #endif
 188         }
 189
 190         return -1;
 191 }
 192
 193 static length_t uncompress_packet(uint8_t *dest, const uint8_t *source, length_t len, int level) {
 194         if(level == 0) {
 195                 memcpy(dest, source, len);
 196                 return len;
 197         } else if(level > 9) {
 198 #ifdef HAVE_LZO
 199                 lzo_uint lzolen = MAXSIZE;
 200                 if(lzo1x_decompress_safe(source, len, dest, &lzolen, NULL) == LZO_E_OK)
 201                         return lzolen;
 202                 else
 203 #endif
 204                         return -1;
 205         }
 206 #ifdef HAVE_ZLIB
 207         else {
 208                 unsigned long destlen = MAXSIZE;
 209                 if(uncompress(dest, &destlen, source, len) == Z_OK)
 210                         return destlen;
 211                 else
 212                         return -1;
 213         }
 214 #endif
 215
 216         return -1;
 217 }
 218
 219 /* VPN packet I/O */
 220
 221 static void receive_packet(node_t *n, vpn_packet_t *packet) {
 222         ifdebug(TRAFFIC) logger(LOG_DEBUG, "Received packet of %d bytes from %s (%s)",
 223                            packet->len, n->name, n->hostname);
 224
 225         route(n, packet);
 226 }
 227
 228 static bool try_mac(node_t *n, const vpn_packet_t *inpkt) {
 229         if(!digest_active(&n->indigest) || inpkt->len < sizeof inpkt->seqno + digest_length(&n->indigest))
 230                 return false;
 231
 232         return digest_verify(&n->indigest, &inpkt->seqno, inpkt->len - n->indigest.maclength, (const char *)&inpkt->seqno + inpkt->len - n->indigest.maclength);
 233 }
 234
 235 static void receive_udppacket(node_t *n, vpn_packet_t *inpkt) {
 236         vpn_packet_t pkt1, pkt2;
 237         vpn_packet_t *pkt[] = { &pkt1, &pkt2, &pkt1, &pkt2 };
 238         int nextpkt = 0;
 239         vpn_packet_t *outpkt = pkt[0];
 240         size_t outlen;
 241         int i;
 242
 243         if(!cipher_active(&n->incipher)) {
 244                 ifdebug(TRAFFIC) logger(LOG_DEBUG, "Got packet from %s (%s) but he hasn't got our key yet",
 245                                         n->name, n->hostname);
 246                 return;
 247         }
 248
 249         /* Check packet length */
 250
 251         if(inpkt->len < sizeof inpkt->seqno + digest_length(&n->indigest)) {
 252                 ifdebug(TRAFFIC) logger(LOG_DEBUG, "Got too short packet from %s (%s)",
 253                                         n->name, n->hostname);
 254                 return;
 255         }
 256
 257         /* Check the message authentication code */
 258
 259         if(digest_active(&n->indigest)) {
 260                 inpkt->len -= n->indigest.maclength;
 261                 if(!digest_verify(&n->indigest, &inpkt->seqno, inpkt->len, (const char *)&inpkt->seqno + inpkt->len)) {
 262                         ifdebug(TRAFFIC) logger(LOG_DEBUG, "Got unauthenticated packet from %s (%s)", n->name, n->hostname);
 263                         return;
 264                 }
 265         }
 266         /* Decrypt the packet */
 267
 268         if(cipher_active(&n->incipher)) {
 269                 outpkt = pkt[nextpkt++];
 270                 outlen = MAXSIZE;
 271
 272                 if(!cipher_decrypt(&n->incipher, &inpkt->seqno, inpkt->len, &outpkt->seqno, &outlen, true)) {
 273                         ifdebug(TRAFFIC) logger(LOG_DEBUG, "Error decrypting packet from %s (%s)", n->name, n->hostname);
 274                         return;
 275                 }
 276
 277                 outpkt->len = outlen;
 278                 inpkt = outpkt;
 279         }
 280
 281         /* Check the sequence number */
 282
 283         inpkt->len -= sizeof inpkt->seqno;
 284         inpkt->seqno = ntohl(inpkt->seqno);
 285
 286         if(inpkt->seqno != n->received_seqno + 1) {
 287                 if(inpkt->seqno >= n->received_seqno + sizeof n->late * 8) {
 288                         logger(LOG_WARNING, "Lost %d packets from %s (%s)",
 289                                            inpkt->seqno - n->received_seqno - 1, n->name, n->hostname);
 290
 291                         memset(n->late, 0, sizeof n->late);
 292                 } else if (inpkt->seqno <= n->received_seqno) {
 293                         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))) {
 294                                 logger(LOG_WARNING, "Got late or replayed packet from %s (%s), seqno %d, last received %d",
 295                                            n->name, n->hostname, inpkt->seqno, n->received_seqno);
 296                                 return;
 297                         }
 298                 } else {
 299                         for(i = n->received_seqno + 1; i < inpkt->seqno; i++)
 300                                 n->late[(i / 8) % sizeof n->late] |= 1 << i % 8;
 301                 }
 302         }
 303
 304         n->late[(inpkt->seqno / 8) % sizeof n->late] &= ~(1 << inpkt->seqno % 8);
 305
 306         if(inpkt->seqno > n->received_seqno)
 307                 n->received_seqno = inpkt->seqno;
 308
 309         if(n->received_seqno > MAX_SEQNO)
 310                 regenerate_key();
 311
 312         /* Decompress the packet */
 313
 314         length_t origlen = inpkt->len;
 315
 316         if(n->incompression) {
 317                 outpkt = pkt[nextpkt++];
 318
 319                 if((outpkt->len = uncompress_packet(outpkt->data, inpkt->data, inpkt->len, n->incompression)) < 0) {
 320                         ifdebug(TRAFFIC) logger(LOG_ERR, "Error while uncompressing packet from %s (%s)",
 321                                                  n->name, n->hostname);
 322                         return;
 323                 }
 324
 325                 inpkt = outpkt;
 326
 327                 origlen -= MTU/64 + 20;
 328         }
 329
 330         inpkt->priority = 0;
 331
 332         if(!inpkt->data[12] && !inpkt->data[13])
 333                 mtu_probe_h(n, inpkt, origlen);
 334         else
 335                 receive_packet(n, inpkt);
 336 }
 337
 338 void receive_tcppacket(connection_t *c, char *buffer, int len) {
 339         vpn_packet_t outpkt;
 340
 341         outpkt.len = len;
 342         if(c->options & OPTION_TCPONLY)
 343                 outpkt.priority = 0;
 344         else
 345                 outpkt.priority = -1;
 346         memcpy(outpkt.data, buffer, len);
 347
 348         receive_packet(c->node, &outpkt);
 349 }
 350
 351 static void send_udppacket(node_t *n, vpn_packet_t *origpkt) {
 352         vpn_packet_t pkt1, pkt2;
 353         vpn_packet_t *pkt[] = { &pkt1, &pkt2, &pkt1, &pkt2 };
 354         vpn_packet_t *inpkt = origpkt;
 355         int nextpkt = 0;
 356         vpn_packet_t *outpkt;
 357         int origlen;
 358         size_t outlen;
 359         static int priority = 0;
 360         int origpriority;
 361         int sock;
 362
 363         if(!n->status.reachable) {
 364                 ifdebug(TRAFFIC) logger(LOG_INFO, "Trying to send UDP packet to unreachable node %s (%s)", n->name, n->hostname);
 365                 return;
 366         }
 367
 368         /* Make sure we have a valid key */
 369
 370         if(!n->status.validkey) {
 371                 time_t now = time(NULL);
 372
 373                 ifdebug(TRAFFIC) logger(LOG_INFO,
 374                                    "No valid key known yet for %s (%s), forwarding via TCP",
 375                                    n->name, n->hostname);
 376
 377                 if(n->last_req_key + 10 < now) {
 378                         send_req_key(n);
 379                         n->last_req_key = now;
 380                 }
 381
 382                 send_tcppacket(n->nexthop->connection, origpkt);
 383
 384                 return;
 385         }
 386
 387         if(n->options & OPTION_PMTU_DISCOVERY && inpkt->len > n->minmtu && (inpkt->data[12] | inpkt->data[13])) {
 388                 ifdebug(TRAFFIC) logger(LOG_INFO,
 389                                 "Packet for %s (%s) larger than minimum MTU, forwarding via %s",
 390                                 n->name, n->hostname, n != n->nexthop ? n->nexthop->name : "TCP");
 391
 392                 if(n != n->nexthop)
 393                         send_packet(n->nexthop, origpkt);
 394                 else
 395                         send_tcppacket(n->nexthop->connection, origpkt);
 396
 397                 return;
 398         }
 399
 400         origlen = inpkt->len;
 401         origpriority = inpkt->priority;
 402
 403         /* Compress the packet */
 404
 405         if(n->outcompression) {
 406                 outpkt = pkt[nextpkt++];
 407
 408                 if((outpkt->len = compress_packet(outpkt->data, inpkt->data, inpkt->len, n->outcompression)) < 0) {
 409                         ifdebug(TRAFFIC) logger(LOG_ERR, "Error while compressing packet to %s (%s)",
 410                                    n->name, n->hostname);
 411                         return;
 412                 }
 413
 414                 inpkt = outpkt;
 415         }
 416
 417         /* Add sequence number */
 418
 419         inpkt->seqno = htonl(++(n->sent_seqno));
 420         inpkt->len += sizeof inpkt->seqno;
 421
 422         /* Encrypt the packet */
 423
 424         if(cipher_active(&n->outcipher)) {
 425                 outpkt = pkt[nextpkt++];
 426                 outlen = MAXSIZE;
 427
 428                 if(!cipher_encrypt(&n->outcipher, &inpkt->seqno, inpkt->len, &outpkt->seqno, &outlen, true)) {
 429                         ifdebug(TRAFFIC) logger(LOG_ERR, "Error while encrypting packet to %s (%s)", n->name, n->hostname);
 430                         goto end;
 431                 }
 432
 433                 outpkt->len = outlen;
 434                 inpkt = outpkt;
 435         }
 436
 437         /* Add the message authentication code */
 438
 439         if(digest_active(&n->outdigest)) {
 440                 digest_create(&n->outdigest, &inpkt->seqno, inpkt->len, (char *)&inpkt->seqno + inpkt->len);
 441                 inpkt->len += digest_length(&n->outdigest);
 442         }
 443
 444         /* Determine which socket we have to use */
 445
 446         for(sock = 0; sock < listen_sockets; sock++)
 447                 if(n->address.sa.sa_family == listen_socket[sock].sa.sa.sa_family)
 448                         break;
 449
 450         if(sock >= listen_sockets)
 451                 sock = 0;                               /* If none is available, just use the first and hope for the best. */
 452
 453         /* Send the packet */
 454
 455 #if defined(SOL_IP) && defined(IP_TOS)
 456         if(priorityinheritance && origpriority != priority
 457            && listen_socket[sock].sa.sa.sa_family == AF_INET) {
 458                 priority = origpriority;
 459                 ifdebug(TRAFFIC) logger(LOG_DEBUG, "Setting outgoing packet priority to %d", priority);
 460                 if(setsockopt(listen_socket[sock].udp, SOL_IP, IP_TOS, &priority, sizeof priority))     /* SO_PRIORITY doesn't seem to work */
 461                         logger(LOG_ERR, "System call `%s' failed: %s", "setsockopt", strerror(errno));
 462         }
 463 #endif
 464
 465         if(sendto(listen_socket[sock].udp, (char *) &inpkt->seqno, inpkt->len, 0, &(n->address.sa), SALEN(n->address.sa)) < 0 && !sockwouldblock(sockerrno)) {
 466                 if(sockmsgsize(sockerrno)) {
 467                         if(n->maxmtu >= origlen)
 468                                 n->maxmtu = origlen - 1;
 469                         if(n->mtu >= origlen)
 470                                 n->mtu = origlen - 1;
 471                 } else
 472                         logger(LOG_ERR, "Error sending packet to %s (%s): %s", n->name, n->hostname, sockstrerror(sockerrno));
 473         }
 474
 475 end:
 476         origpkt->len = origlen;
 477 }
 478
 479 /*
 480   send a packet to the given vpn ip.
 481 */
 482 void send_packet(const node_t *n, vpn_packet_t *packet) {
 483         node_t *via;
 484
 485         if(n == myself) {
 486                 if(overwrite_mac)
 487                          memcpy(packet->data, mymac.x, ETH_ALEN);
 488                 write_packet(packet);
 489                 return;
 490         }
 491
 492         ifdebug(TRAFFIC) logger(LOG_ERR, "Sending packet of %d bytes to %s (%s)",
 493                            packet->len, n->name, n->hostname);
 494
 495         if(!n->status.reachable) {
 496                 ifdebug(TRAFFIC) logger(LOG_INFO, "Node %s (%s) is not reachable",
 497                                    n->name, n->hostname);
 498                 return;
 499         }
 500
 501         via = (packet->priority == -1 || n->via == myself) ? n->nexthop : n->via;
 502
 503         if(via != n)
 504                 ifdebug(TRAFFIC) logger(LOG_INFO, "Sending packet to %s via %s (%s)",
 505                            n->name, via->name, n->via->hostname);
 506
 507         if(packet->priority == -1 || ((myself->options | via->options) & OPTION_TCPONLY)) {
 508                 if(!send_tcppacket(via->connection, packet))
 509                         terminate_connection(via->connection, true);
 510         } else
 511                 send_udppacket(via, packet);
 512 }
 513
 514 /* Broadcast a packet using the minimum spanning tree */
 515
 516 void broadcast_packet(const node_t *from, vpn_packet_t *packet) {
 517         splay_node_t *node;
 518         connection_t *c;
 519
 520         ifdebug(TRAFFIC) logger(LOG_INFO, "Broadcasting packet of %d bytes from %s (%s)",
 521                            packet->len, from->name, from->hostname);
 522
 523         if(from != myself) {
 524                 send_packet(myself, packet);
 525
 526                 // In TunnelServer mode, do not forward broadcast packets.
 527                 // The MST might not be valid and create loops.
 528                 if(tunnelserver)
 529                         return;
 530         }
 531
 532         for(node = connection_tree->head; node; node = node->next) {
 533                 c = node->data;
 534
 535                 if(c->status.active && c->status.mst && c != from->nexthop->connection)
 536                         send_packet(c->node, packet);
 537         }
 538 }
 539
 540 static node_t *try_harder(const sockaddr_t *from, const vpn_packet_t *pkt) {
 541         splay_node_t *node;
 542         node_t *n, *found = NULL;
 543         static time_t last_hard_try = 0;
 544         time_t now = time(NULL);
 545
 546         if(last_hard_try == now)
 547                 return NULL;
 548         else
 549                 last_hard_try = now;
 550
 551         for(node = node_tree->head; node; node = node->next) {
 552                 n = node->data;
 553
 554                 if(n == myself || !n->status.reachable || !digest_active(&n->indigest))
 555                         continue;
 556
 557                 if(try_mac(n, pkt)) {
 558                         found = n;
 559                         break;
 560                 }
 561         }
 562
 563         return found;
 564 }
 565
 566 void handle_incoming_vpn_data(int sock, short events, void *data) {
 567         vpn_packet_t pkt;
 568         char *hostname;
 569         sockaddr_t from;
 570         socklen_t fromlen = sizeof from;
 571         node_t *n;
 572         int len;
 573
 574         len = recvfrom(sock, (char *) &pkt.seqno, MAXSIZE, 0, &from.sa, &fromlen);
 575
 576         if(len <= 0 || len > MAXSIZE) {
 577                 if(!sockwouldblock(sockerrno))
 578                         logger(LOG_ERR, "Receiving packet failed: %s", sockstrerror(sockerrno));
 579                 return;
 580         }
 581
 582         pkt.len = len;
 583
 584         sockaddrunmap(&from);           /* Some braindead IPv6 implementations do stupid things. */
 585
 586         n = lookup_node_udp(&from);
 587
 588         if(!n) {
 589                 n = try_harder(&from, &pkt);
 590                 if(n)
 591                         update_node_udp(n, &from);
 592                 else ifdebug(PROTOCOL) {
 593                         hostname = sockaddr2hostname(&from);
 594                         logger(LOG_WARNING, "Received UDP packet from unknown source %s", hostname);
 595                         free(hostname);
 596                         return;
 597                 }
 598                 else
 599                         return;
 600         }
 601
 602         receive_udppacket(n, &pkt);
 603 }
 604
 605 void handle_device_data(int sock, short events, void *data) {
 606         vpn_packet_t packet;
 607
 608         if(read_packet(&packet))
 609                 route(myself, &packet);
 610 }