src/net_packet.c

   1 /*
   2     net_packet.c -- Handles in- and outgoing VPN packets
   3     Copyright (C) 1998-2003 Ivo Timmermans <ivo@o2w.nl>,
   4                   2000-2003 Guus Sliepen <guus@sliepen.eu.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: net_packet.c,v 1.1.2.49 2003/12/27 16:32:52 guus Exp $
  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 bool strictsource = true;
  58 EVP_CIPHER_CTX packet_ctx;
  59 static char lzo_wrkmem[LZO1X_999_MEM_COMPRESS > LZO1X_1_MEM_COMPRESS ? LZO1X_999_MEM_COMPRESS : LZO1X_1_MEM_COMPRESS];
  60
  61 static void send_udppacket(node_t *, vpn_packet_t *);
  62
  63 #define MAX_SEQNO 1073741824
  64
  65 void send_mtu_probe(node_t *n)
  66 {
  67         vpn_packet_t packet;
  68         int len, i;
  69
  70         cp();
  71
  72         n->mtuprobes++;
  73         n->mtuevent = NULL;
  74
  75         if(n->mtuprobes >= 10 && !n->minmtu) {
  76                 ifdebug(TRAFFIC) logger(LOG_INFO, _("No response to MTU probes from %s (%s)"), n->name, n->hostname);
  77                 return;
  78         }
  79
  80         for(i = 0; i < 3; i++) {
  81                 if(n->mtuprobes >= 30 || n->minmtu >= n->maxmtu) {
  82                         n->mtu = n->minmtu;
  83                         ifdebug(TRAFFIC) logger(LOG_INFO, _("Fixing MTU of %s (%s) to %d after %d probes"), n->name, n->hostname, n->mtu, n->mtuprobes);
  84                         return;
  85                 }
  86
  87                 len = n->minmtu + 1 + random() % (n->maxmtu - n->minmtu);
  88                 if(len < 64)
  89                         len = 64;
  90
  91                 memset(packet.data, 0, 14);
  92                 RAND_pseudo_bytes(packet.data + 14, len - 14);
  93                 packet.len = len;
  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 = xmalloc(sizeof(*n->mtuevent));
 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 bool authenticate_udppacket(node_t *n, vpn_packet_t *inpkt) {
 172         char hmac[EVP_MAX_MD_SIZE];
 173
 174         if(inpkt->len < sizeof(inpkt->seqno) + (myself->digest ? myself->maclength : 0))
 175                 return false;
 176
 177         /* Check the message authentication code */
 178
 179         if(myself->digest && myself->maclength) {
 180                 HMAC(myself->digest, myself->key, myself->keylength,
 181                          (char *) &inpkt->seqno, inpkt->len - myself->maclength, hmac, NULL);
 182
 183                 if(memcmp(hmac, (char *) &inpkt->seqno + inpkt->len - myself->maclength, myself->maclength))
 184                         return false;
 185         }
 186
 187         return true;
 188 }
 189
 190 static void receive_udppacket(node_t *n, vpn_packet_t *inpkt)
 191 {
 192         vpn_packet_t pkt1, pkt2;
 193         vpn_packet_t *pkt[] = { &pkt1, &pkt2, &pkt1, &pkt2 };
 194         int nextpkt = 0;
 195         vpn_packet_t *outpkt = pkt[0];
 196         int outlen, outpad;
 197         int i;
 198
 199         cp();
 200
 201         if(!authenticate_udppacket(n, inpkt)) {
 202                 ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Got unauthenticated packet from %s (%s)"),
 203                                            n->name, n->hostname);
 204                 return;
 205         }
 206
 207         inpkt->len -= myself->digest ? myself->maclength : 0;
 208
 209         /* Decrypt the packet */
 210
 211         if(myself->cipher) {
 212                 outpkt = pkt[nextpkt++];
 213
 214                 if(!EVP_DecryptInit_ex(&packet_ctx, NULL, NULL, NULL, NULL)
 215                                 || !EVP_DecryptUpdate(&packet_ctx, (char *) &outpkt->seqno, &outlen,
 216                                         (char *) &inpkt->seqno, inpkt->len)
 217                                 || !EVP_DecryptFinal_ex(&packet_ctx, (char *) &outpkt->seqno + outlen, &outpad)) {
 218                         ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Error decrypting packet from %s (%s): %s"),
 219                                                 n->name, n->hostname, ERR_error_string(ERR_get_error(), NULL));
 220                         return;
 221                 }
 222
 223                 outpkt->len = outlen + outpad;
 224                 inpkt = outpkt;
 225         }
 226
 227         /* Check the sequence number */
 228
 229         inpkt->len -= sizeof(inpkt->seqno);
 230         inpkt->seqno = ntohl(inpkt->seqno);
 231
 232         if(inpkt->seqno != n->received_seqno + 1) {
 233                 if(inpkt->seqno >= n->received_seqno + sizeof(n->late) * 8) {
 234                         logger(LOG_WARNING, _("Lost %d packets from %s (%s)"),
 235                                            inpkt->seqno - n->received_seqno - 1, n->name, n->hostname);
 236
 237                         memset(n->late, 0, sizeof(n->late));
 238                 } else if (inpkt->seqno <= n->received_seqno) {
 239                         if(inpkt->seqno <= n->received_seqno - sizeof(n->late) * 8 || !(n->late[(inpkt->seqno / 8) % sizeof(n->late)] & (1 << inpkt->seqno % 8))) {
 240                                 logger(LOG_WARNING, _("Got late or replayed packet from %s (%s), seqno %d, last received %d"),
 241                                            n->name, n->hostname, inpkt->seqno, n->received_seqno);
 242                         } else
 243                                 for(i = n->received_seqno + 1; i < inpkt->seqno; i++)
 244                                         n->late[(inpkt->seqno / 8) % sizeof(n->late)] |= 1 << i % 8;
 245                 }
 246         }
 247
 248         n->received_seqno = inpkt->seqno;
 249         n->late[(n->received_seqno / 8) % sizeof(n->late)] &= ~(1 << n->received_seqno % 8);
 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         if(n->connection)
 269                 n->connection->last_ping_time = now;
 270
 271         if(!inpkt->data[12] && !inpkt->data[13])
 272                 mtu_probe_h(n, inpkt);
 273         else
 274                 receive_packet(n, inpkt);
 275 }
 276
 277 void receive_tcppacket(connection_t *c, char *buffer, int len)
 278 {
 279         vpn_packet_t outpkt;
 280
 281         cp();
 282
 283         outpkt.len = len;
 284         memcpy(outpkt.data, buffer, len);
 285
 286         receive_packet(c->node, &outpkt);
 287 }
 288
 289 static void send_udppacket(node_t *n, vpn_packet_t *inpkt)
 290 {
 291         vpn_packet_t pkt1, pkt2;
 292         vpn_packet_t *pkt[] = { &pkt1, &pkt2, &pkt1, &pkt2 };
 293         int nextpkt = 0;
 294         vpn_packet_t *outpkt;
 295         int origlen;
 296         int outlen, outpad;
 297         vpn_packet_t *copy;
 298         static int priority = 0;
 299         int origpriority;
 300         int sock;
 301
 302         cp();
 303
 304         /* Make sure we have a valid key */
 305
 306         if(!n->status.validkey) {
 307                 ifdebug(TRAFFIC) logger(LOG_INFO,
 308                                    _("No valid key known yet for %s (%s), queueing packet"),
 309                                    n->name, n->hostname);
 310
 311                 /* Since packet is on the stack of handle_tap_input(), we have to make a copy of it first. */
 312
 313                 *(copy = xmalloc(sizeof(*copy))) = *inpkt;
 314
 315                 list_insert_tail(n->queue, copy);
 316
 317                 if(n->queue->count > MAXQUEUELENGTH)
 318                         list_delete_head(n->queue);
 319
 320                 if(!n->status.waitingforkey)
 321                         send_req_key(n->nexthop->connection, myself, n);
 322
 323                 n->status.waitingforkey = true;
 324
 325                 return;
 326         }
 327
 328         origlen = inpkt->len;
 329         origpriority = inpkt->priority;
 330
 331         /* Compress the packet */
 332
 333         if(n->compression) {
 334                 outpkt = pkt[nextpkt++];
 335
 336                 if((outpkt->len = compress_packet(outpkt->data, inpkt->data, inpkt->len, n->compression)) < 0) {
 337                         ifdebug(TRAFFIC) logger(LOG_ERR, _("Error while compressing packet to %s (%s)"),
 338                                    n->name, n->hostname);
 339                         return;
 340                 }
 341
 342                 inpkt = outpkt;
 343         }
 344
 345         /* Add sequence number */
 346
 347         inpkt->seqno = htonl(++(n->sent_seqno));
 348         inpkt->len += sizeof(inpkt->seqno);
 349
 350         /* Encrypt the packet */
 351
 352         if(n->cipher) {
 353                 outpkt = pkt[nextpkt++];
 354
 355                 if(!EVP_EncryptInit_ex(&n->packet_ctx, NULL, NULL, NULL, NULL)
 356                                 || !EVP_EncryptUpdate(&n->packet_ctx, (char *) &outpkt->seqno, &outlen,
 357                                         (char *) &inpkt->seqno, inpkt->len)
 358                                 || !EVP_EncryptFinal_ex(&n->packet_ctx, (char *) &outpkt->seqno + outlen, &outpad)) {
 359                         ifdebug(TRAFFIC) logger(LOG_ERR, _("Error while encrypting packet to %s (%s): %s"),
 360                                                 n->name, n->hostname, ERR_error_string(ERR_get_error(), NULL));
 361                         goto end;
 362                 }
 363
 364                 outpkt->len = outlen + outpad;
 365                 inpkt = outpkt;
 366         }
 367
 368         /* Add the message authentication code */
 369
 370         if(n->digest && n->maclength) {
 371                 HMAC(n->digest, n->key, n->keylength, (char *) &inpkt->seqno,
 372                          inpkt->len, (char *) &inpkt->seqno + inpkt->len, &outlen);
 373                 inpkt->len += n->maclength;
 374         }
 375
 376         /* Determine which socket we have to use */
 377
 378         for(sock = 0; sock < listen_sockets; sock++)
 379                 if(n->address.sa.sa_family == listen_socket[sock].sa.sa.sa_family)
 380                         break;
 381
 382         if(sock >= listen_sockets)
 383                 sock = 0;                               /* If none is available, just use the first and hope for the best. */
 384
 385         /* Send the packet */
 386
 387 #if defined(SOL_IP) && defined(IP_TOS)
 388         if(priorityinheritance && origpriority != priority
 389            && listen_socket[sock].sa.sa.sa_family == AF_INET) {
 390                 priority = origpriority;
 391                 ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Setting outgoing packet priority to %d"), priority);
 392                 if(setsockopt(listen_socket[sock].udp, SOL_IP, IP_TOS, &priority, sizeof(priority)))    /* SO_PRIORITY doesn't seem to work */
 393                         logger(LOG_ERR, _("System call `%s' failed: %s"), "setsockopt", strerror(errno));
 394         }
 395 #endif
 396
 397         if((sendto(listen_socket[sock].udp, (char *) &inpkt->seqno, inpkt->len, 0, &(n->address.sa), SALEN(n->address.sa))) < 0) {
 398                 if(errno == EMSGSIZE) {
 399                         if(n->maxmtu >= origlen)
 400                                 n->maxmtu = origlen - 1;
 401                         if(n->mtu >= origlen)
 402                                 n->mtu = origlen - 1;
 403                 } else
 404                         logger(LOG_ERR, _("Error sending packet to %s (%s): %s"), n->name, n->hostname, strerror(errno));
 405         }
 406
 407 end:
 408         inpkt->len = origlen;
 409 }
 410
 411 /*
 412   send a packet to the given vpn ip.
 413 */
 414 void send_packet(const node_t *n, vpn_packet_t *packet)
 415 {
 416         node_t *via;
 417
 418         cp();
 419
 420         if(n == myself) {
 421                 if(overwrite_mac)
 422                          memcpy(packet->data, mymac.x, ETH_ALEN);
 423                 write_packet(packet);
 424                 return;
 425         }
 426
 427         ifdebug(TRAFFIC) logger(LOG_ERR, _("Sending packet of %d bytes to %s (%s)"),
 428                            packet->len, n->name, n->hostname);
 429
 430         if(!n->status.reachable) {
 431                 ifdebug(TRAFFIC) logger(LOG_INFO, _("Node %s (%s) is not reachable"),
 432                                    n->name, n->hostname);
 433                 return;
 434         }
 435
 436         via = (n->via == myself) ? n->nexthop : n->via;
 437
 438         if(via != n)
 439                 ifdebug(TRAFFIC) logger(LOG_ERR, _("Sending packet to %s via %s (%s)"),
 440                            n->name, via->name, n->via->hostname);
 441
 442         if((myself->options | via->options) & OPTION_TCPONLY) {
 443                 if(!send_tcppacket(via->connection, packet))
 444                         terminate_connection(via->connection, true);
 445         } else
 446                 send_udppacket(via, packet);
 447 }
 448
 449 /* Broadcast a packet using the minimum spanning tree */
 450
 451 void broadcast_packet(const node_t *from, vpn_packet_t *packet)
 452 {
 453         avl_node_t *node;
 454         connection_t *c;
 455
 456         cp();
 457
 458         ifdebug(TRAFFIC) logger(LOG_INFO, _("Broadcasting packet of %d bytes from %s (%s)"),
 459                            packet->len, from->name, from->hostname);
 460
 461         for(node = connection_tree->head; node; node = node->next) {
 462                 c = node->data;
 463
 464                 if(c->status.active && c->status.mst && c != from->nexthop->connection)
 465                         send_packet(c->node, packet);
 466         }
 467 }
 468
 469 void flush_queue(node_t *n)
 470 {
 471         list_node_t *node, *next;
 472
 473         cp();
 474
 475         ifdebug(TRAFFIC) logger(LOG_INFO, _("Flushing queue for %s (%s)"), n->name, n->hostname);
 476
 477         for(node = n->queue->head; node; node = next) {
 478                 next = node->next;
 479                 send_udppacket(n, node->data);
 480                 list_delete_node(n->queue, node);
 481         }
 482 }
 483
 484 void handle_incoming_vpn_data(int sock)
 485 {
 486         vpn_packet_t pkt;
 487         char *hostname;
 488         sockaddr_t from;
 489         socklen_t fromlen = sizeof(from);
 490         node_t *n;
 491         static time_t lasttime = 0;
 492
 493         cp();
 494
 495         pkt.len = recvfrom(sock, (char *) &pkt.seqno, MAXSIZE, 0, &from.sa, &fromlen);
 496
 497         if(pkt.len < 0) {
 498                 logger(LOG_ERR, _("Receiving packet failed: %s"), strerror(errno));
 499                 return;
 500         }
 501
 502         sockaddrunmap(&from);           /* Some braindead IPv6 implementations do stupid things. */
 503
 504         n = lookup_node_udp(&from);
 505
 506         if(!n && !strictsource && myself->digest && myself->maclength && lasttime != now) {
 507                 avl_node_t *node;
 508
 509                 lasttime = now;
 510
 511                 for(node = node_tree->head; node; node = node->next) {
 512                         n = node->data;
 513
 514                         if(authenticate_udppacket(n, &pkt)) {
 515                                 update_node_address(n, &from);
 516                                 logger(LOG_DEBUG, _("Updated address of node %s to %s"), n->name, n->hostname);
 517                                 break;
 518                         }
 519                 }
 520         }
 521
 522         if(!n) {
 523                 hostname = sockaddr2hostname(&from);
 524                 logger(LOG_WARNING, _("Received UDP packet from unknown source %s"), hostname);
 525                 free(hostname);
 526                 return;
 527         }
 528
 529         receive_udppacket(n, &pkt);
 530 }