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