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