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                   2000-2006 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 "graph.h"
  40 #include "list.h"
  41 #include "logger.h"
  42 #include "net.h"
  43 #include "netutl.h"
  44 #include "protocol.h"
  45 #include "process.h"
  46 #include "route.h"
  47 #include "utils.h"
  48 #include "xalloc.h"
  49
  50 #ifdef WSAEMSGSIZE
  51 #define EMSGSIZE WSAEMSGSIZE
  52 #endif
  53
  54 int keylifetime = 0;
  55 EVP_CIPHER_CTX packet_ctx;
  56 static char lzo_wrkmem[LZO1X_999_MEM_COMPRESS > LZO1X_1_MEM_COMPRESS ? LZO1X_999_MEM_COMPRESS : LZO1X_1_MEM_COMPRESS];
  57
  58 static void send_udppacket(node_t *, vpn_packet_t *);
  59
  60 #define MAX_SEQNO 1073741824
  61
  62 static void send_mtu_probe_handler(int fd, short events, void *data) {
  63         node_t *n = data;
  64         vpn_packet_t packet;
  65         int len, i;
  66
  67         cp();
  68
  69         n->mtuprobes++;
  70
  71         if(n->mtuprobes >= 10 && !n->minmtu) {
  72                 ifdebug(TRAFFIC) logger(LOG_INFO, _("No response to MTU probes from %s (%s)"), n->name, n->hostname);
  73                 return;
  74         }
  75
  76         for(i = 0; i < 3; i++) {
  77                 if(n->mtuprobes >= 30 || n->minmtu >= n->maxmtu) {
  78                         n->mtu = n->minmtu;
  79                         ifdebug(TRAFFIC) logger(LOG_INFO, _("Fixing MTU of %s (%s) to %d after %d probes"), n->name, n->hostname, n->mtu, n->mtuprobes);
  80                         return;
  81                 }
  82
  83                 len = n->minmtu + 1 + random() % (n->maxmtu - n->minmtu);
  84                 if(len < 64)
  85                         len = 64;
  86
  87                 memset(packet.data, 0, 14);
  88                 RAND_pseudo_bytes(packet.data + 14, len - 14);
  89                 packet.len = len;
  90
  91                 ifdebug(TRAFFIC) logger(LOG_INFO, _("Sending MTU probe length %d to %s (%s)"), len, n->name, n->hostname);
  92
  93                 send_udppacket(n, &packet);
  94         }
  95
  96         event_add(&n->mtuevent, &(struct timeval){1, 0});
  97 }
  98
  99 void send_mtu_probe(node_t *n) {
 100         if(!timeout_initialized(&n->mtuevent))
 101                 timeout_set(&n->mtuevent, send_mtu_probe_handler, n);
 102         send_mtu_probe_handler(0, 0, n);
 103 }
 104
 105 void mtu_probe_h(node_t *n, vpn_packet_t *packet) {
 106         ifdebug(TRAFFIC) logger(LOG_INFO, _("Got MTU probe length %d from %s (%s)"), packet->len, n->name, n->hostname);
 107
 108         if(!packet->data[0]) {
 109                 packet->data[0] = 1;
 110                 send_packet(n, packet);
 111         } else {
 112                 if(n->minmtu < packet->len)
 113                         n->minmtu = packet->len;
 114         }
 115 }
 116
 117 static length_t compress_packet(uint8_t *dest, const uint8_t *source, length_t len, int level)
 118 {
 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 {
 140         if(level > 9) {
 141                 lzo_uint lzolen = MAXSIZE;
 142                 if(lzo1x_decompress_safe(source, len, dest, &lzolen, NULL) == LZO_E_OK)
 143                         return lzolen;
 144                 else
 145                         return -1;
 146         } else {
 147                 unsigned long destlen = MAXSIZE;
 148                 if(uncompress(dest, &destlen, source, len) == Z_OK)
 149                         return destlen;
 150                 else
 151                         return -1;
 152         }
 153
 154         return -1;
 155 }
 156
 157 /* VPN packet I/O */
 158
 159 static void receive_packet(node_t *n, vpn_packet_t *packet)
 160 {
 161         cp();
 162
 163         ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Received packet of %d bytes from %s (%s)"),
 164                            packet->len, n->name, n->hostname);
 165
 166         route(n, packet);
 167 }
 168
 169 static void receive_udppacket(node_t *n, vpn_packet_t *inpkt)
 170 {
 171         vpn_packet_t pkt1, pkt2;
 172         vpn_packet_t *pkt[] = { &pkt1, &pkt2, &pkt1, &pkt2 };
 173         int nextpkt = 0;
 174         vpn_packet_t *outpkt = pkt[0];
 175         int outlen, outpad;
 176         unsigned char hmac[EVP_MAX_MD_SIZE];
 177         int i;
 178
 179         cp();
 180
 181         /* Check packet length */
 182
 183         if(inpkt->len < sizeof(inpkt->seqno) + myself->maclength) {
 184                 ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Got too short packet from %s (%s)"),
 185                                         n->name, n->hostname);
 186                 return;
 187         }
 188
 189         /* Check the message authentication code */
 190
 191         if(myself->digest && myself->maclength) {
 192                 inpkt->len -= myself->maclength;
 193                 HMAC(myself->digest, myself->key, myself->keylength,
 194                          (unsigned char *) &inpkt->seqno, inpkt->len, (unsigned char *)hmac, NULL);
 195
 196                 if(memcmp(hmac, (char *) &inpkt->seqno + inpkt->len, myself->maclength)) {
 197                         ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Got unauthenticated packet from %s (%s)"),
 198                                            n->name, n->hostname);
 199                         return;
 200                 }
 201         }
 202
 203         /* Decrypt the packet */
 204
 205         if(myself->cipher) {
 206                 outpkt = pkt[nextpkt++];
 207
 208                 if(!EVP_DecryptInit_ex(&packet_ctx, NULL, NULL, NULL, NULL)
 209                                 || !EVP_DecryptUpdate(&packet_ctx, (unsigned char *) &outpkt->seqno, &outlen,
 210                                         (unsigned char *) &inpkt->seqno, inpkt->len)
 211                                 || !EVP_DecryptFinal_ex(&packet_ctx, (unsigned char *) &outpkt->seqno + outlen, &outpad)) {
 212                         ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Error decrypting packet from %s (%s): %s"),
 213                                                 n->name, n->hostname, ERR_error_string(ERR_get_error(), NULL));
 214                         return;
 215                 }
 216
 217                 outpkt->len = outlen + outpad;
 218                 inpkt = outpkt;
 219         }
 220
 221         /* Check the sequence number */
 222
 223         inpkt->len -= sizeof(inpkt->seqno);
 224         inpkt->seqno = ntohl(inpkt->seqno);
 225
 226         if(inpkt->seqno != n->received_seqno + 1) {
 227                 if(inpkt->seqno >= n->received_seqno + sizeof(n->late) * 8) {
 228                         logger(LOG_WARNING, _("Lost %d packets from %s (%s)"),
 229                                            inpkt->seqno - n->received_seqno - 1, n->name, n->hostname);
 230
 231                         memset(n->late, 0, sizeof(n->late));
 232                 } else if (inpkt->seqno <= n->received_seqno) {
 233                         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))) {
 234                                 logger(LOG_WARNING, _("Got late or replayed packet from %s (%s), seqno %d, last received %d"),
 235                                            n->name, n->hostname, inpkt->seqno, n->received_seqno);
 236                                 return;
 237                         }
 238                 } else {
 239                         for(i = n->received_seqno + 1; i < inpkt->seqno; i++)
 240                                 n->late[(i / 8) % sizeof(n->late)] |= 1 << i % 8;
 241                 }
 242         }
 243
 244         n->late[(inpkt->seqno / 8) % sizeof(n->late)] &= ~(1 << inpkt->seqno % 8);
 245
 246         if(inpkt->seqno > n->received_seqno)
 247                 n->received_seqno = inpkt->seqno;
 248
 249         if(n->received_seqno > MAX_SEQNO)
 250                 regenerate_key();
 251
 252         /* Decompress the packet */
 253
 254         if(myself->compression) {
 255                 outpkt = pkt[nextpkt++];
 256
 257                 if((outpkt->len = uncompress_packet(outpkt->data, inpkt->data, inpkt->len, myself->compression)) < 0) {
 258                         ifdebug(TRAFFIC) logger(LOG_ERR, _("Error while uncompressing packet from %s (%s)"),
 259                                                  n->name, n->hostname);
 260                         return;
 261                 }
 262
 263                 inpkt = outpkt;
 264         }
 265
 266         if(!inpkt->data[12] && !inpkt->data[13])
 267                 mtu_probe_h(n, inpkt);
 268         else
 269                 receive_packet(n, inpkt);
 270 }
 271
 272 void receive_tcppacket(connection_t *c, char *buffer, int len)
 273 {
 274         vpn_packet_t outpkt;
 275
 276         cp();
 277
 278         outpkt.len = len;
 279         memcpy(outpkt.data, buffer, len);
 280
 281         receive_packet(c->node, &outpkt);
 282 }
 283
 284 static void send_udppacket(node_t *n, vpn_packet_t *origpkt)
 285 {
 286         vpn_packet_t pkt1, pkt2;
 287         vpn_packet_t *pkt[] = { &pkt1, &pkt2, &pkt1, &pkt2 };
 288         vpn_packet_t *inpkt = origpkt;
 289         int nextpkt = 0;
 290         vpn_packet_t *outpkt;
 291         int origlen;
 292         int outlen, outpad;
 293         vpn_packet_t *copy;
 294         static int priority = 0;
 295         int origpriority;
 296         int sock;
 297
 298         cp();
 299
 300         /* Make sure we have a valid key */
 301
 302         if(!n->status.validkey) {
 303                 ifdebug(TRAFFIC) logger(LOG_INFO,
 304                                    _("No valid key known yet for %s (%s), queueing packet"),
 305                                    n->name, n->hostname);
 306
 307                 /* Since packet is on the stack of handle_tap_input(), we have to make a copy of it first. */
 308
 309                 *(copy = xmalloc(sizeof(*copy))) = *inpkt;
 310
 311                 list_insert_tail(n->queue, copy);
 312
 313                 if(n->queue->count > MAXQUEUELENGTH)
 314                         list_delete_head(n->queue);
 315
 316                 if(!n->status.waitingforkey)
 317                         send_req_key(n->nexthop->connection, myself, n);
 318
 319                 n->status.waitingforkey = true;
 320
 321                 return;
 322         }
 323
 324         origlen = inpkt->len;
 325         origpriority = inpkt->priority;
 326
 327         /* Compress the packet */
 328
 329         if(n->compression) {
 330                 outpkt = pkt[nextpkt++];
 331
 332                 if((outpkt->len = compress_packet(outpkt->data, inpkt->data, inpkt->len, n->compression)) < 0) {
 333                         ifdebug(TRAFFIC) logger(LOG_ERR, _("Error while compressing packet to %s (%s)"),
 334                                    n->name, n->hostname);
 335                         return;
 336                 }
 337
 338                 inpkt = outpkt;
 339         }
 340
 341         /* Add sequence number */
 342
 343         inpkt->seqno = htonl(++(n->sent_seqno));
 344         inpkt->len += sizeof(inpkt->seqno);
 345
 346         /* Encrypt the packet */
 347
 348         if(n->cipher) {
 349                 outpkt = pkt[nextpkt++];
 350
 351                 if(!EVP_EncryptInit_ex(&n->packet_ctx, NULL, NULL, NULL, NULL)
 352                                 || !EVP_EncryptUpdate(&n->packet_ctx, (unsigned char *) &outpkt->seqno, &outlen,
 353                                         (unsigned char *) &inpkt->seqno, inpkt->len)
 354                                 || !EVP_EncryptFinal_ex(&n->packet_ctx, (unsigned char *) &outpkt->seqno + outlen, &outpad)) {
 355                         ifdebug(TRAFFIC) logger(LOG_ERR, _("Error while encrypting packet to %s (%s): %s"),
 356                                                 n->name, n->hostname, ERR_error_string(ERR_get_error(), NULL));
 357                         goto end;
 358                 }
 359
 360                 outpkt->len = outlen + outpad;
 361                 inpkt = outpkt;
 362         }
 363
 364         /* Add the message authentication code */
 365
 366         if(n->digest && n->maclength) {
 367                 HMAC(n->digest, n->key, n->keylength, (unsigned char *) &inpkt->seqno,
 368                          inpkt->len, (unsigned char *) &inpkt->seqno + inpkt->len, NULL);
 369                 inpkt->len += n->maclength;
 370         }
 371
 372         /* Determine which socket we have to use */
 373
 374         for(sock = 0; sock < listen_sockets; sock++)
 375                 if(n->address.sa.sa_family == listen_socket[sock].sa.sa.sa_family)
 376                         break;
 377
 378         if(sock >= listen_sockets)
 379                 sock = 0;                               /* If none is available, just use the first and hope for the best. */
 380
 381         /* Send the packet */
 382
 383 #if defined(SOL_IP) && defined(IP_TOS)
 384         if(priorityinheritance && origpriority != priority
 385            && listen_socket[sock].sa.sa.sa_family == AF_INET) {
 386                 priority = origpriority;
 387                 ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Setting outgoing packet priority to %d"), priority);
 388                 if(setsockopt(listen_socket[sock].udp, SOL_IP, IP_TOS, &priority, sizeof(priority)))    /* SO_PRIORITY doesn't seem to work */
 389                         logger(LOG_ERR, _("System call `%s' failed: %s"), "setsockopt", strerror(errno));
 390         }
 391 #endif
 392
 393         if((sendto(listen_socket[sock].udp, (char *) &inpkt->seqno, inpkt->len, 0, &(n->address.sa), SALEN(n->address.sa))) < 0) {
 394                 if(errno == EMSGSIZE) {
 395                         if(n->maxmtu >= origlen)
 396                                 n->maxmtu = origlen - 1;
 397                         if(n->mtu >= origlen)
 398                                 n->mtu = origlen - 1;
 399                 } else
 400                         logger(LOG_ERR, _("Error sending packet to %s (%s): %s"), n->name, n->hostname, strerror(errno));
 401         }
 402
 403 end:
 404         origpkt->len = origlen;
 405 }
 406
 407 /*
 408   send a packet to the given vpn ip.
 409 */
 410 void send_packet(const node_t *n, vpn_packet_t *packet)
 411 {
 412         node_t *via;
 413
 414         cp();
 415
 416         if(n == myself) {
 417                 if(overwrite_mac)
 418                          memcpy(packet->data, mymac.x, ETH_ALEN);
 419                 write_packet(packet);
 420                 return;
 421         }
 422
 423         ifdebug(TRAFFIC) logger(LOG_ERR, _("Sending packet of %d bytes to %s (%s)"),
 424                            packet->len, n->name, n->hostname);
 425
 426         if(!n->status.reachable) {
 427                 ifdebug(TRAFFIC) logger(LOG_INFO, _("Node %s (%s) is not reachable"),
 428                                    n->name, n->hostname);
 429                 return;
 430         }
 431
 432         via = (n->via == myself) ? n->nexthop : n->via;
 433
 434         if(via != n)
 435                 ifdebug(TRAFFIC) logger(LOG_ERR, _("Sending packet to %s via %s (%s)"),
 436                            n->name, via->name, n->via->hostname);
 437
 438         if((myself->options | via->options) & OPTION_TCPONLY) {
 439                 if(!send_tcppacket(via->connection, packet))
 440                         terminate_connection(via->connection, true);
 441         } else
 442                 send_udppacket(via, packet);
 443 }
 444
 445 /* Broadcast a packet using the minimum spanning tree */
 446
 447 void broadcast_packet(const node_t *from, vpn_packet_t *packet)
 448 {
 449         avl_node_t *node;
 450         connection_t *c;
 451
 452         cp();
 453
 454         ifdebug(TRAFFIC) logger(LOG_INFO, _("Broadcasting packet of %d bytes from %s (%s)"),
 455                            packet->len, from->name, from->hostname);
 456
 457         if(from != myself)
 458                 send_packet(myself, packet);
 459
 460         for(node = connection_tree->head; node; node = node->next) {
 461                 c = node->data;
 462
 463                 if(c->status.active && c->status.mst && c != from->nexthop->connection)
 464                         send_packet(c->node, packet);
 465         }
 466 }
 467
 468 void flush_queue(node_t *n)
 469 {
 470         list_node_t *node, *next;
 471
 472         cp();
 473
 474         ifdebug(TRAFFIC) logger(LOG_INFO, _("Flushing queue for %s (%s)"), n->name, n->hostname);
 475
 476         for(node = n->queue->head; node; node = next) {
 477                 next = node->next;
 478                 send_udppacket(n, node->data);
 479                 list_delete_node(n->queue, node);
 480         }
 481 }
 482
 483 void handle_incoming_vpn_data(int sock, short events, void *data)
 484 {
 485         vpn_packet_t pkt;
 486         char *hostname;
 487         sockaddr_t from;
 488         socklen_t fromlen = sizeof(from);
 489         node_t *n;
 490
 491         cp();
 492
 493         pkt.len = recvfrom(sock, (char *) &pkt.seqno, MAXSIZE, 0, &from.sa, &fromlen);
 494
 495         if(pkt.len < 0) {
 496                 logger(LOG_ERR, _("Receiving packet failed: %s"), strerror(errno));
 497                 return;
 498         }
 499
 500         sockaddrunmap(&from);           /* Some braindead IPv6 implementations do stupid things. */
 501
 502         n = lookup_node_udp(&from);
 503
 504         if(!n) {
 505                 hostname = sockaddr2hostname(&from);
 506                 logger(LOG_WARNING, _("Received UDP packet from unknown source %s"),
 507                            hostname);
 508                 free(hostname);
 509                 return;
 510         }
 511
 512         receive_udppacket(n, &pkt);
 513 }
 514
 515 void handle_device_data(int sock, short events, void *data)
 516 {
 517         vpn_packet_t packet;
 518
 519         if(read_packet(&packet))
 520                 route(myself, &packet);
 521 }