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         if(level == 10) {
 119                 lzo_uint lzolen = MAXSIZE;
 120                 lzo1x_1_compress(source, len, dest, &lzolen, lzo_wrkmem);
 121                 return lzolen;
 122         } else if(level < 10) {
 123                 unsigned long destlen = MAXSIZE;
 124                 if(compress2(dest, &destlen, source, len, level) == Z_OK)
 125                         return destlen;
 126                 else
 127                         return -1;
 128         } else {
 129                 lzo_uint lzolen = MAXSIZE;
 130                 lzo1x_999_compress(source, len, dest, &lzolen, lzo_wrkmem);
 131                 return lzolen;
 132         }
 133
 134         return -1;
 135 }
 136
 137 static length_t uncompress_packet(uint8_t *dest, const uint8_t *source, length_t len, int level) {
 138         if(level > 9) {
 139                 lzo_uint lzolen = MAXSIZE;
 140                 if(lzo1x_decompress_safe(source, len, dest, &lzolen, NULL) == LZO_E_OK)
 141                         return lzolen;
 142                 else
 143                         return -1;
 144         } else {
 145                 unsigned long destlen = MAXSIZE;
 146                 if(uncompress(dest, &destlen, source, len) == Z_OK)
 147                         return destlen;
 148                 else
 149                         return -1;
 150         }
 151
 152         return -1;
 153 }
 154
 155 /* VPN packet I/O */
 156
 157 static void receive_packet(node_t *n, vpn_packet_t *packet) {
 158         cp();
 159
 160         ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Received packet of %d bytes from %s (%s)"),
 161                            packet->len, n->name, n->hostname);
 162
 163         route(n, packet);
 164 }
 165
 166 static void receive_udppacket(node_t *n, vpn_packet_t *inpkt) {
 167         vpn_packet_t pkt1, pkt2;
 168         vpn_packet_t *pkt[] = { &pkt1, &pkt2, &pkt1, &pkt2 };
 169         int nextpkt = 0;
 170         vpn_packet_t *outpkt = pkt[0];
 171         int outlen, outpad;
 172         unsigned char hmac[EVP_MAX_MD_SIZE];
 173         int i;
 174
 175         cp();
 176
 177         /* Check packet length */
 178
 179         if(inpkt->len < sizeof(inpkt->seqno) + myself->maclength) {
 180                 ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Got too short packet from %s (%s)"),
 181                                         n->name, n->hostname);
 182                 return;
 183         }
 184
 185         /* Check the message authentication code */
 186
 187         if(myself->digest && myself->maclength) {
 188                 inpkt->len -= myself->maclength;
 189                 HMAC(myself->digest, myself->key, myself->keylength,
 190                          (unsigned char *) &inpkt->seqno, inpkt->len, (unsigned char *)hmac, NULL);
 191
 192                 if(memcmp(hmac, (char *) &inpkt->seqno + inpkt->len, myself->maclength)) {
 193                         ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Got unauthenticated packet from %s (%s)"),
 194                                            n->name, n->hostname);
 195                         return;
 196                 }
 197         }
 198
 199         /* Decrypt the packet */
 200
 201         if(myself->cipher) {
 202                 outpkt = pkt[nextpkt++];
 203
 204                 if(!EVP_DecryptInit_ex(&packet_ctx, NULL, NULL, NULL, NULL)
 205                                 || !EVP_DecryptUpdate(&packet_ctx, (unsigned char *) &outpkt->seqno, &outlen,
 206                                         (unsigned char *) &inpkt->seqno, inpkt->len)
 207                                 || !EVP_DecryptFinal_ex(&packet_ctx, (unsigned char *) &outpkt->seqno + outlen, &outpad)) {
 208                         ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Error decrypting packet from %s (%s): %s"),
 209                                                 n->name, n->hostname, ERR_error_string(ERR_get_error(), NULL));
 210                         return;
 211                 }
 212
 213                 outpkt->len = outlen + outpad;
 214                 inpkt = outpkt;
 215         }
 216
 217         /* Check the sequence number */
 218
 219         inpkt->len -= sizeof(inpkt->seqno);
 220         inpkt->seqno = ntohl(inpkt->seqno);
 221
 222         if(inpkt->seqno != n->received_seqno + 1) {
 223                 if(inpkt->seqno >= n->received_seqno + sizeof(n->late) * 8) {
 224                         logger(LOG_WARNING, _("Lost %d packets from %s (%s)"),
 225                                            inpkt->seqno - n->received_seqno - 1, n->name, n->hostname);
 226
 227                         memset(n->late, 0, sizeof(n->late));
 228                 } else if (inpkt->seqno <= n->received_seqno) {
 229                         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))) {
 230                                 logger(LOG_WARNING, _("Got late or replayed packet from %s (%s), seqno %d, last received %d"),
 231                                            n->name, n->hostname, inpkt->seqno, n->received_seqno);
 232                                 return;
 233                         }
 234                 } else {
 235                         for(i = n->received_seqno + 1; i < inpkt->seqno; i++)
 236                                 n->late[(i / 8) % sizeof(n->late)] |= 1 << i % 8;
 237                 }
 238         }
 239
 240         n->late[(inpkt->seqno / 8) % sizeof(n->late)] &= ~(1 << inpkt->seqno % 8);
 241
 242         if(inpkt->seqno > n->received_seqno)
 243                 n->received_seqno = inpkt->seqno;
 244
 245         if(n->received_seqno > MAX_SEQNO)
 246                 regenerate_key();
 247
 248         /* Decompress the packet */
 249
 250         if(myself->compression) {
 251                 outpkt = pkt[nextpkt++];
 252
 253                 if((outpkt->len = uncompress_packet(outpkt->data, inpkt->data, inpkt->len, myself->compression)) < 0) {
 254                         ifdebug(TRAFFIC) logger(LOG_ERR, _("Error while uncompressing packet from %s (%s)"),
 255                                                  n->name, n->hostname);
 256                         return;
 257                 }
 258
 259                 inpkt = outpkt;
 260         }
 261
 262         if(!inpkt->data[12] && !inpkt->data[13])
 263                 mtu_probe_h(n, inpkt);
 264         else
 265                 receive_packet(n, inpkt);
 266 }
 267
 268 void receive_tcppacket(connection_t *c, char *buffer, int len) {
 269         vpn_packet_t outpkt;
 270
 271         cp();
 272
 273         outpkt.len = len;
 274         memcpy(outpkt.data, buffer, len);
 275
 276         receive_packet(c->node, &outpkt);
 277 }
 278
 279 static void send_udppacket(node_t *n, vpn_packet_t *origpkt) {
 280         vpn_packet_t pkt1, pkt2;
 281         vpn_packet_t *pkt[] = { &pkt1, &pkt2, &pkt1, &pkt2 };
 282         vpn_packet_t *inpkt = origpkt;
 283         int nextpkt = 0;
 284         vpn_packet_t *outpkt;
 285         int origlen;
 286         int outlen, outpad;
 287         vpn_packet_t *copy;
 288         static int priority = 0;
 289         int origpriority;
 290         int sock;
 291
 292         cp();
 293
 294         /* Make sure we have a valid key */
 295
 296         if(!n->status.validkey) {
 297                 ifdebug(TRAFFIC) logger(LOG_INFO,
 298                                    _("No valid key known yet for %s (%s), queueing packet"),
 299                                    n->name, n->hostname);
 300
 301                 /* Since packet is on the stack of handle_tap_input(), we have to make a copy of it first. */
 302
 303                 *(copy = xmalloc(sizeof(*copy))) = *inpkt;
 304
 305                 list_insert_tail(n->queue, copy);
 306
 307                 if(n->queue->count > MAXQUEUELENGTH)
 308                         list_delete_head(n->queue);
 309
 310                 if(!n->status.waitingforkey)
 311                         send_req_key(n->nexthop->connection, myself, n);
 312
 313                 n->status.waitingforkey = true;
 314
 315                 return;
 316         }
 317
 318         origlen = inpkt->len;
 319         origpriority = inpkt->priority;
 320
 321         /* Compress the packet */
 322
 323         if(n->compression) {
 324                 outpkt = pkt[nextpkt++];
 325
 326                 if((outpkt->len = compress_packet(outpkt->data, inpkt->data, inpkt->len, n->compression)) < 0) {
 327                         ifdebug(TRAFFIC) logger(LOG_ERR, _("Error while compressing packet to %s (%s)"),
 328                                    n->name, n->hostname);
 329                         return;
 330                 }
 331
 332                 inpkt = outpkt;
 333         }
 334
 335         /* Add sequence number */
 336
 337         inpkt->seqno = htonl(++(n->sent_seqno));
 338         inpkt->len += sizeof(inpkt->seqno);
 339
 340         /* Encrypt the packet */
 341
 342         if(n->cipher) {
 343                 outpkt = pkt[nextpkt++];
 344
 345                 if(!EVP_EncryptInit_ex(&n->packet_ctx, NULL, NULL, NULL, NULL)
 346                                 || !EVP_EncryptUpdate(&n->packet_ctx, (unsigned char *) &outpkt->seqno, &outlen,
 347                                         (unsigned char *) &inpkt->seqno, inpkt->len)
 348                                 || !EVP_EncryptFinal_ex(&n->packet_ctx, (unsigned char *) &outpkt->seqno + outlen, &outpad)) {
 349                         ifdebug(TRAFFIC) logger(LOG_ERR, _("Error while encrypting packet to %s (%s): %s"),
 350                                                 n->name, n->hostname, ERR_error_string(ERR_get_error(), NULL));
 351                         goto end;
 352                 }
 353
 354                 outpkt->len = outlen + outpad;
 355                 inpkt = outpkt;
 356         }
 357
 358         /* Add the message authentication code */
 359
 360         if(n->digest && n->maclength) {
 361                 HMAC(n->digest, n->key, n->keylength, (unsigned char *) &inpkt->seqno,
 362                          inpkt->len, (unsigned char *) &inpkt->seqno + inpkt->len, NULL);
 363                 inpkt->len += n->maclength;
 364         }
 365
 366         /* Determine which socket we have to use */
 367
 368         for(sock = 0; sock < listen_sockets; sock++)
 369                 if(n->address.sa.sa_family == listen_socket[sock].sa.sa.sa_family)
 370                         break;
 371
 372         if(sock >= listen_sockets)
 373                 sock = 0;                               /* If none is available, just use the first and hope for the best. */
 374
 375         /* Send the packet */
 376
 377 #if defined(SOL_IP) && defined(IP_TOS)
 378         if(priorityinheritance && origpriority != priority
 379            && listen_socket[sock].sa.sa.sa_family == AF_INET) {
 380                 priority = origpriority;
 381                 ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Setting outgoing packet priority to %d"), priority);
 382                 if(setsockopt(listen_socket[sock].udp, SOL_IP, IP_TOS, &priority, sizeof(priority)))    /* SO_PRIORITY doesn't seem to work */
 383                         logger(LOG_ERR, _("System call `%s' failed: %s"), "setsockopt", strerror(errno));
 384         }
 385 #endif
 386
 387         if((sendto(listen_socket[sock].udp, (char *) &inpkt->seqno, inpkt->len, 0, &(n->address.sa), SALEN(n->address.sa))) < 0) {
 388                 if(errno == EMSGSIZE) {
 389                         if(n->maxmtu >= origlen)
 390                                 n->maxmtu = origlen - 1;
 391                         if(n->mtu >= origlen)
 392                                 n->mtu = origlen - 1;
 393                 } else
 394                         logger(LOG_ERR, _("Error sending packet to %s (%s): %s"), n->name, n->hostname, strerror(errno));
 395         }
 396
 397 end:
 398         origpkt->len = origlen;
 399 }
 400
 401 /*
 402   send a packet to the given vpn ip.
 403 */
 404 void send_packet(const node_t *n, vpn_packet_t *packet) {
 405         node_t *via;
 406
 407         cp();
 408
 409         if(n == myself) {
 410                 if(overwrite_mac)
 411                          memcpy(packet->data, mymac.x, ETH_ALEN);
 412                 write_packet(packet);
 413                 return;
 414         }
 415
 416         ifdebug(TRAFFIC) logger(LOG_ERR, _("Sending packet of %d bytes to %s (%s)"),
 417                            packet->len, n->name, n->hostname);
 418
 419         if(!n->status.reachable) {
 420                 ifdebug(TRAFFIC) logger(LOG_INFO, _("Node %s (%s) is not reachable"),
 421                                    n->name, n->hostname);
 422                 return;
 423         }
 424
 425         via = (n->via == myself) ? n->nexthop : n->via;
 426
 427         if(via != n)
 428                 ifdebug(TRAFFIC) logger(LOG_ERR, _("Sending packet to %s via %s (%s)"),
 429                            n->name, via->name, n->via->hostname);
 430
 431         if((myself->options | via->options) & OPTION_TCPONLY) {
 432                 if(!send_tcppacket(via->connection, packet))
 433                         terminate_connection(via->connection, true);
 434         } else
 435                 send_udppacket(via, packet);
 436 }
 437
 438 /* Broadcast a packet using the minimum spanning tree */
 439
 440 void broadcast_packet(const node_t *from, vpn_packet_t *packet) {
 441         avl_node_t *node;
 442         connection_t *c;
 443
 444         cp();
 445
 446         ifdebug(TRAFFIC) logger(LOG_INFO, _("Broadcasting packet of %d bytes from %s (%s)"),
 447                            packet->len, from->name, from->hostname);
 448
 449         if(from != myself)
 450                 send_packet(myself, packet);
 451
 452         for(node = connection_tree->head; node; node = node->next) {
 453                 c = node->data;
 454
 455                 if(c->status.active && c->status.mst && c != from->nexthop->connection)
 456                         send_packet(c->node, packet);
 457         }
 458 }
 459
 460 void flush_queue(node_t *n) {
 461         list_node_t *node, *next;
 462
 463         cp();
 464
 465         ifdebug(TRAFFIC) logger(LOG_INFO, _("Flushing queue for %s (%s)"), n->name, n->hostname);
 466
 467         for(node = n->queue->head; node; node = next) {
 468                 next = node->next;
 469                 send_udppacket(n, node->data);
 470                 list_delete_node(n->queue, node);
 471         }
 472 }
 473
 474 void handle_incoming_vpn_data(int sock, short events, void *data) {
 475         vpn_packet_t pkt;
 476         char *hostname;
 477         sockaddr_t from;
 478         socklen_t fromlen = sizeof(from);
 479         node_t *n;
 480
 481         cp();
 482
 483         pkt.len = recvfrom(sock, (char *) &pkt.seqno, MAXSIZE, 0, &from.sa, &fromlen);
 484
 485         if(pkt.len < 0) {
 486                 logger(LOG_ERR, _("Receiving packet failed: %s"), strerror(errno));
 487                 return;
 488         }
 489
 490         sockaddrunmap(&from);           /* Some braindead IPv6 implementations do stupid things. */
 491
 492         n = lookup_node_udp(&from);
 493
 494         if(!n) {
 495                 hostname = sockaddr2hostname(&from);
 496                 logger(LOG_WARNING, _("Received UDP packet from unknown source %s"),
 497                            hostname);
 498                 free(hostname);
 499                 return;
 500         }
 501
 502         receive_udppacket(n, &pkt);
 503 }
 504
 505 void handle_device_data(int sock, short events, void *data) {
 506         vpn_packet_t packet;
 507
 508         if(read_packet(&packet))
 509                 route(myself, &packet);
 510 }