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