src/net_packet.c

   1 /*
   2     net_packet.c -- Handles in- and outgoing VPN packets
   3     Copyright (C) 1998-2005 Ivo Timmermans,
   4                   2000-2006 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 void receive_udppacket(node_t *n, vpn_packet_t *inpkt)
 172 {
 173         vpn_packet_t pkt1, pkt2;
 174         vpn_packet_t *pkt[] = { &pkt1, &pkt2, &pkt1, &pkt2 };
 175         int nextpkt = 0;
 176         vpn_packet_t *outpkt = pkt[0];
 177         int outlen, outpad;
 178         unsigned char hmac[EVP_MAX_MD_SIZE];
 179         int i;
 180
 181         cp();
 182
 183         /* Check packet length */
 184
 185         if(inpkt->len < sizeof(inpkt->seqno) + myself->maclength) {
 186                 ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Got too short packet from %s (%s)"),
 187                                         n->name, n->hostname);
 188                 return;
 189         }
 190
 191         /* Check the message authentication code */
 192
 193         if(myself->digest && myself->maclength) {
 194                 inpkt->len -= myself->maclength;
 195                 HMAC(myself->digest, myself->key, myself->keylength,
 196                          (unsigned char *) &inpkt->seqno, inpkt->len, (unsigned char *)hmac, NULL);
 197
 198                 if(memcmp(hmac, (char *) &inpkt->seqno + inpkt->len, myself->maclength)) {
 199                         ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Got unauthenticated packet from %s (%s)"),
 200                                            n->name, n->hostname);
 201                         return;
 202                 }
 203         }
 204
 205         /* Decrypt the packet */
 206
 207         if(myself->cipher) {
 208                 outpkt = pkt[nextpkt++];
 209
 210                 if(!EVP_DecryptInit_ex(&packet_ctx, NULL, NULL, NULL, NULL)
 211                                 || !EVP_DecryptUpdate(&packet_ctx, (unsigned char *) &outpkt->seqno, &outlen,
 212                                         (unsigned char *) &inpkt->seqno, inpkt->len)
 213                                 || !EVP_DecryptFinal_ex(&packet_ctx, (unsigned char *) &outpkt->seqno + outlen, &outpad)) {
 214                         ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Error decrypting packet from %s (%s): %s"),
 215                                                 n->name, n->hostname, ERR_error_string(ERR_get_error(), NULL));
 216                         return;
 217                 }
 218
 219                 outpkt->len = outlen + outpad;
 220                 inpkt = outpkt;
 221         }
 222
 223         /* Check the sequence number */
 224
 225         inpkt->len -= sizeof(inpkt->seqno);
 226         inpkt->seqno = ntohl(inpkt->seqno);
 227
 228         if(inpkt->seqno != n->received_seqno + 1) {
 229                 if(inpkt->seqno >= n->received_seqno + sizeof(n->late) * 8) {
 230                         logger(LOG_WARNING, _("Lost %d packets from %s (%s)"),
 231                                            inpkt->seqno - n->received_seqno - 1, n->name, n->hostname);
 232
 233                         memset(n->late, 0, sizeof(n->late));
 234                 } else if (inpkt->seqno <= n->received_seqno) {
 235                         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))) {
 236                                 logger(LOG_WARNING, _("Got late or replayed packet from %s (%s), seqno %d, last received %d"),
 237                                            n->name, n->hostname, inpkt->seqno, n->received_seqno);
 238                                 return;
 239                         }
 240                 } else {
 241                         for(i = n->received_seqno + 1; i < inpkt->seqno; i++)
 242                                 n->late[(i / 8) % sizeof(n->late)] |= 1 << i % 8;
 243                 }
 244         }
 245
 246         n->late[(inpkt->seqno / 8) % sizeof(n->late)] &= ~(1 << inpkt->seqno % 8);
 247
 248         if(inpkt->seqno > n->received_seqno)
 249                 n->received_seqno = inpkt->seqno;
 250
 251         if(n->received_seqno > MAX_SEQNO)
 252                 keyexpires = 0;
 253
 254         /* Decompress the packet */
 255
 256         if(myself->compression) {
 257                 outpkt = pkt[nextpkt++];
 258
 259                 if((outpkt->len = uncompress_packet(outpkt->data, inpkt->data, inpkt->len, myself->compression)) < 0) {
 260                         ifdebug(TRAFFIC) logger(LOG_ERR, _("Error while uncompressing packet from %s (%s)"),
 261                                                  n->name, n->hostname);
 262                         return;
 263                 }
 264
 265                 inpkt = outpkt;
 266         }
 267
 268         inpkt->priority = 0;
 269
 270         if(n->connection)
 271                 n->connection->last_ping_time = now;
 272
 273         if(!inpkt->data[12] && !inpkt->data[13])
 274                 mtu_probe_h(n, inpkt);
 275         else
 276                 receive_packet(n, inpkt);
 277 }
 278
 279 void receive_tcppacket(connection_t *c, char *buffer, int len)
 280 {
 281         vpn_packet_t outpkt;
 282
 283         cp();
 284
 285         outpkt.len = len;
 286         if(c->options & OPTION_TCPONLY)
 287                 outpkt.priority = 0;
 288         else
 289                 outpkt.priority = -1;
 290         memcpy(outpkt.data, buffer, len);
 291
 292         receive_packet(c->node, &outpkt);
 293 }
 294
 295 static void send_udppacket(node_t *n, vpn_packet_t *origpkt)
 296 {
 297         vpn_packet_t pkt1, pkt2;
 298         vpn_packet_t *pkt[] = { &pkt1, &pkt2, &pkt1, &pkt2 };
 299         vpn_packet_t *inpkt = origpkt;
 300         int nextpkt = 0;
 301         vpn_packet_t *outpkt;
 302         int origlen;
 303         int outlen, outpad;
 304         static int priority = 0;
 305         int origpriority;
 306         int sock;
 307
 308         cp();
 309
 310         /* Make sure we have a valid key */
 311
 312         if(!n->status.validkey) {
 313                 ifdebug(TRAFFIC) logger(LOG_INFO,
 314                                    _("No valid key known yet for %s (%s), forwarding via TCP"),
 315                                    n->name, n->hostname);
 316
 317                 if(!n->status.waitingforkey)
 318                         send_req_key(n->nexthop->connection, myself, n);
 319
 320                 n->status.waitingforkey = true;
 321
 322                 send_tcppacket(n->nexthop->connection, origpkt);
 323
 324                 return;
 325         }
 326
 327         if(!n->minmtu && (inpkt->data[12] | inpkt->data[13])) {
 328                 ifdebug(TRAFFIC) logger(LOG_INFO,
 329                                 _("No minimum MTU established yet for %s (%s), forwarding via TCP"),
 330                                 n->name, n->hostname);
 331
 332                 send_tcppacket(n->nexthop->connection, origpkt);
 333         }
 334
 335         origlen = inpkt->len;
 336         origpriority = inpkt->priority;
 337
 338         /* Compress the packet */
 339
 340         if(n->compression) {
 341                 outpkt = pkt[nextpkt++];
 342
 343                 if((outpkt->len = compress_packet(outpkt->data, inpkt->data, inpkt->len, n->compression)) < 0) {
 344                         ifdebug(TRAFFIC) logger(LOG_ERR, _("Error while compressing packet to %s (%s)"),
 345                                    n->name, n->hostname);
 346                         return;
 347                 }
 348
 349                 inpkt = outpkt;
 350         }
 351
 352         /* Add sequence number */
 353
 354         inpkt->seqno = htonl(++(n->sent_seqno));
 355         inpkt->len += sizeof(inpkt->seqno);
 356
 357         /* Encrypt the packet */
 358
 359         if(n->cipher) {
 360                 outpkt = pkt[nextpkt++];
 361
 362                 if(!EVP_EncryptInit_ex(&n->packet_ctx, NULL, NULL, NULL, NULL)
 363                                 || !EVP_EncryptUpdate(&n->packet_ctx, (unsigned char *) &outpkt->seqno, &outlen,
 364                                         (unsigned char *) &inpkt->seqno, inpkt->len)
 365                                 || !EVP_EncryptFinal_ex(&n->packet_ctx, (unsigned char *) &outpkt->seqno + outlen, &outpad)) {
 366                         ifdebug(TRAFFIC) logger(LOG_ERR, _("Error while encrypting packet to %s (%s): %s"),
 367                                                 n->name, n->hostname, ERR_error_string(ERR_get_error(), NULL));
 368                         goto end;
 369                 }
 370
 371                 outpkt->len = outlen + outpad;
 372                 inpkt = outpkt;
 373         }
 374
 375         /* Add the message authentication code */
 376
 377         if(n->digest && n->maclength) {
 378                 HMAC(n->digest, n->key, n->keylength, (unsigned char *) &inpkt->seqno,
 379                          inpkt->len, (unsigned char *) &inpkt->seqno + inpkt->len, NULL);
 380                 inpkt->len += n->maclength;
 381         }
 382
 383         /* Determine which socket we have to use */
 384
 385         for(sock = 0; sock < listen_sockets; sock++)
 386                 if(n->address.sa.sa_family == listen_socket[sock].sa.sa.sa_family)
 387                         break;
 388
 389         if(sock >= listen_sockets)
 390                 sock = 0;                               /* If none is available, just use the first and hope for the best. */
 391
 392         /* Send the packet */
 393
 394 #if defined(SOL_IP) && defined(IP_TOS)
 395         if(priorityinheritance && origpriority != priority
 396            && listen_socket[sock].sa.sa.sa_family == AF_INET) {
 397                 priority = origpriority;
 398                 ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Setting outgoing packet priority to %d"), priority);
 399                 if(setsockopt(listen_socket[sock].udp, SOL_IP, IP_TOS, &priority, sizeof(priority)))    /* SO_PRIORITY doesn't seem to work */
 400                         logger(LOG_ERR, _("System call `%s' failed: %s"), "setsockopt", strerror(errno));
 401         }
 402 #endif
 403
 404         if((sendto(listen_socket[sock].udp, (char *) &inpkt->seqno, inpkt->len, 0, &(n->address.sa), SALEN(n->address.sa))) < 0) {
 405                 if(errno == EMSGSIZE) {
 406                         if(n->maxmtu >= origlen)
 407                                 n->maxmtu = origlen - 1;
 408                         if(n->mtu >= origlen)
 409                                 n->mtu = origlen - 1;
 410                 } else
 411                         logger(LOG_ERR, _("Error sending packet to %s (%s): %s"), n->name, n->hostname, strerror(errno));
 412         }
 413
 414 end:
 415         origpkt->len = origlen;
 416 }
 417
 418 /*
 419   send a packet to the given vpn ip.
 420 */
 421 void send_packet(const node_t *n, vpn_packet_t *packet)
 422 {
 423         node_t *via;
 424
 425         cp();
 426
 427         if(n == myself) {
 428                 if(overwrite_mac)
 429                          memcpy(packet->data, mymac.x, ETH_ALEN);
 430                 write_packet(packet);
 431                 return;
 432         }
 433
 434         ifdebug(TRAFFIC) logger(LOG_ERR, _("Sending packet of %d bytes to %s (%s)"),
 435                            packet->len, n->name, n->hostname);
 436
 437         if(!n->status.reachable) {
 438                 ifdebug(TRAFFIC) logger(LOG_INFO, _("Node %s (%s) is not reachable"),
 439                                    n->name, n->hostname);
 440                 return;
 441         }
 442
 443         via = (packet->priority == -1 || n->via == myself) ? n->nexthop : n->via;
 444
 445         if(via != n)
 446                 ifdebug(TRAFFIC) logger(LOG_INFO, _("Sending packet to %s via %s (%s)"),
 447                            n->name, via->name, n->via->hostname);
 448
 449         if(packet->priority == -1 || ((myself->options | via->options) & OPTION_TCPONLY)) {
 450                 if(!send_tcppacket(via->connection, packet))
 451                         terminate_connection(via->connection, true);
 452         } else
 453                 send_udppacket(via, packet);
 454 }
 455
 456 /* Broadcast a packet using the minimum spanning tree */
 457
 458 void broadcast_packet(const node_t *from, vpn_packet_t *packet)
 459 {
 460         avl_node_t *node;
 461         connection_t *c;
 462
 463         cp();
 464
 465         ifdebug(TRAFFIC) logger(LOG_INFO, _("Broadcasting packet of %d bytes from %s (%s)"),
 466                            packet->len, from->name, from->hostname);
 467
 468         if(from != myself)
 469                 send_packet(myself, packet);
 470
 471         for(node = connection_tree->head; node; node = node->next) {
 472                 c = node->data;
 473
 474                 if(c->status.active && c->status.mst && c != from->nexthop->connection)
 475                         send_packet(c->node, packet);
 476         }
 477 }
 478
 479 void handle_incoming_vpn_data(int sock)
 480 {
 481         vpn_packet_t pkt;
 482         char *hostname;
 483         sockaddr_t from;
 484         socklen_t fromlen = sizeof(from);
 485         node_t *n;
 486
 487         cp();
 488
 489         pkt.len = recvfrom(sock, (char *) &pkt.seqno, MAXSIZE, 0, &from.sa, &fromlen);
 490
 491         if(pkt.len < 0) {
 492                 logger(LOG_ERR, _("Receiving packet failed: %s"), strerror(errno));
 493                 return;
 494         }
 495
 496         sockaddrunmap(&from);           /* Some braindead IPv6 implementations do stupid things. */
 497
 498         n = lookup_node_udp(&from);
 499
 500         if(!n) {
 501                 hostname = sockaddr2hostname(&from);
 502                 logger(LOG_WARNING, _("Received UDP packet from unknown source %s"),
 503                            hostname);
 504                 free(hostname);
 505                 return;
 506         }
 507
 508         receive_udppacket(n, &pkt);
 509 }