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 1.1.2.48 2003/12/24 10:48:14 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 "event.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 int keyexpires = 0;
  56 EVP_CIPHER_CTX packet_ctx;
  57 static char lzo_wrkmem[LZO1X_999_MEM_COMPRESS > LZO1X_1_MEM_COMPRESS ? LZO1X_999_MEM_COMPRESS : LZO1X_1_MEM_COMPRESS];
  58
  59 static void send_udppacket(node_t *, vpn_packet_t *);
  60
  61 #define MAX_SEQNO 1073741824
  62
  63 void send_mtu_probe(node_t *n)
  64 {
  65         vpn_packet_t packet;
  66         int len, i;
  67
  68         cp();
  69
  70         n->mtuprobes++;
  71         n->mtuevent = NULL;
  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 + random() % (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
  93                 ifdebug(TRAFFIC) logger(LOG_INFO, _("Sending MTU probe length %d to %s (%s)"), len, n->name, n->hostname);
  94
  95                 send_udppacket(n, &packet);
  96         }
  97
  98         n->mtuevent = xmalloc(sizeof(*n->mtuevent));
  99         n->mtuevent->handler = (event_handler_t)send_mtu_probe;
 100         n->mtuevent->data = n;
 101         n->mtuevent->time = now + 1;
 102         event_add(n->mtuevent);
 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         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                          (char *) &inpkt->seqno, inpkt->len, 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, (char *) &outpkt->seqno, &outlen,
 210                                         (char *) &inpkt->seqno, inpkt->len)
 211                                 || !EVP_DecryptFinal_ex(&packet_ctx, (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(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                         } else
 237                                 for(i = n->received_seqno + 1; i < inpkt->seqno; i++)
 238                                         n->late[(inpkt->seqno / 8) % sizeof(n->late)] |= 1 << i % 8;
 239                 }
 240         }
 241
 242         n->received_seqno = inpkt->seqno;
 243         n->late[(n->received_seqno / 8) % sizeof(n->late)] &= ~(1 << n->received_seqno % 8);
 244
 245         if(n->received_seqno > MAX_SEQNO)
 246                 keyexpires = 0;
 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(n->connection)
 263                 n->connection->last_ping_time = now;
 264
 265         if(!inpkt->data[12] && !inpkt->data[13])
 266                 mtu_probe_h(n, inpkt);
 267         else
 268                 receive_packet(n, inpkt);
 269 }
 270
 271 void receive_tcppacket(connection_t *c, char *buffer, int len)
 272 {
 273         vpn_packet_t outpkt;
 274
 275         cp();
 276
 277         outpkt.len = len;
 278         memcpy(outpkt.data, buffer, len);
 279
 280         receive_packet(c->node, &outpkt);
 281 }
 282
 283 static void send_udppacket(node_t *n, vpn_packet_t *inpkt)
 284 {
 285         vpn_packet_t pkt1, pkt2;
 286         vpn_packet_t *pkt[] = { &pkt1, &pkt2, &pkt1, &pkt2 };
 287         int nextpkt = 0;
 288         vpn_packet_t *outpkt;
 289         int origlen;
 290         int outlen, outpad;
 291         vpn_packet_t *copy;
 292         static int priority = 0;
 293         int origpriority;
 294         int sock;
 295
 296         cp();
 297
 298         /* Make sure we have a valid key */
 299
 300         if(!n->status.validkey) {
 301                 ifdebug(TRAFFIC) logger(LOG_INFO,
 302                                    _("No valid key known yet for %s (%s), queueing packet"),
 303                                    n->name, n->hostname);
 304
 305                 /* Since packet is on the stack of handle_tap_input(), we have to make a copy of it first. */
 306
 307                 *(copy = xmalloc(sizeof(*copy))) = *inpkt;
 308
 309                 list_insert_tail(n->queue, copy);
 310
 311                 if(n->queue->count > MAXQUEUELENGTH)
 312                         list_delete_head(n->queue);
 313
 314                 if(!n->status.waitingforkey)
 315                         send_req_key(n->nexthop->connection, myself, n);
 316
 317                 n->status.waitingforkey = true;
 318
 319                 return;
 320         }
 321
 322         origlen = inpkt->len;
 323         origpriority = inpkt->priority;
 324
 325         /* Compress the packet */
 326
 327         if(n->compression) {
 328                 outpkt = pkt[nextpkt++];
 329
 330                 if((outpkt->len = compress_packet(outpkt->data, inpkt->data, inpkt->len, n->compression)) < 0) {
 331                         ifdebug(TRAFFIC) logger(LOG_ERR, _("Error while compressing packet to %s (%s)"),
 332                                    n->name, n->hostname);
 333                         return;
 334                 }
 335
 336                 inpkt = outpkt;
 337         }
 338
 339         /* Add sequence number */
 340
 341         inpkt->seqno = htonl(++(n->sent_seqno));
 342         inpkt->len += sizeof(inpkt->seqno);
 343
 344         /* Encrypt the packet */
 345
 346         if(n->cipher) {
 347                 outpkt = pkt[nextpkt++];
 348
 349                 if(!EVP_EncryptInit_ex(&n->packet_ctx, NULL, NULL, NULL, NULL)
 350                                 || !EVP_EncryptUpdate(&n->packet_ctx, (char *) &outpkt->seqno, &outlen,
 351                                         (char *) &inpkt->seqno, inpkt->len)
 352                                 || !EVP_EncryptFinal_ex(&n->packet_ctx, (char *) &outpkt->seqno + outlen, &outpad)) {
 353                         ifdebug(TRAFFIC) logger(LOG_ERR, _("Error while encrypting packet to %s (%s): %s"),
 354                                                 n->name, n->hostname, ERR_error_string(ERR_get_error(), NULL));
 355                         goto end;
 356                 }
 357
 358                 outpkt->len = outlen + outpad;
 359                 inpkt = outpkt;
 360         }
 361
 362         /* Add the message authentication code */
 363
 364         if(n->digest && n->maclength) {
 365                 HMAC(n->digest, n->key, n->keylength, (char *) &inpkt->seqno,
 366                          inpkt->len, (char *) &inpkt->seqno + inpkt->len, &outlen);
 367                 inpkt->len += n->maclength;
 368         }
 369
 370         /* Determine which socket we have to use */
 371
 372         for(sock = 0; sock < listen_sockets; sock++)
 373                 if(n->address.sa.sa_family == listen_socket[sock].sa.sa.sa_family)
 374                         break;
 375
 376         if(sock >= listen_sockets)
 377                 sock = 0;                               /* If none is available, just use the first and hope for the best. */
 378
 379         /* Send the packet */
 380
 381 #if defined(SOL_IP) && defined(IP_TOS)
 382         if(priorityinheritance && origpriority != priority
 383            && listen_socket[sock].sa.sa.sa_family == AF_INET) {
 384                 priority = origpriority;
 385                 ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Setting outgoing packet priority to %d"), priority);
 386                 if(setsockopt(listen_socket[sock].udp, SOL_IP, IP_TOS, &priority, sizeof(priority)))    /* SO_PRIORITY doesn't seem to work */
 387                         logger(LOG_ERR, _("System call `%s' failed: %s"), "setsockopt", strerror(errno));
 388         }
 389 #endif
 390
 391         if((sendto(listen_socket[sock].udp, (char *) &inpkt->seqno, inpkt->len, 0, &(n->address.sa), SALEN(n->address.sa))) < 0) {
 392                 if(errno == EMSGSIZE) {
 393                         if(n->maxmtu >= origlen)
 394                                 n->maxmtu = origlen - 1;
 395                         if(n->mtu >= origlen)
 396                                 n->mtu = origlen - 1;
 397                 } else
 398                         logger(LOG_ERR, _("Error sending packet to %s (%s): %s"), n->name, n->hostname, strerror(errno));
 399         }
 400
 401 end:
 402         inpkt->len = origlen;
 403 }
 404
 405 /*
 406   send a packet to the given vpn ip.
 407 */
 408 void send_packet(const node_t *n, vpn_packet_t *packet)
 409 {
 410         node_t *via;
 411
 412         cp();
 413
 414         if(n == myself) {
 415                 write_packet(packet);
 416                 return;
 417         }
 418
 419         ifdebug(TRAFFIC) logger(LOG_ERR, _("Sending packet of %d bytes to %s (%s)"),
 420                            packet->len, n->name, n->hostname);
 421
 422         if(!n->status.reachable) {
 423                 ifdebug(TRAFFIC) logger(LOG_INFO, _("Node %s (%s) is not reachable"),
 424                                    n->name, n->hostname);
 425                 return;
 426         }
 427
 428         via = (n->via == myself) ? n->nexthop : n->via;
 429
 430         if(via != n)
 431                 ifdebug(TRAFFIC) logger(LOG_ERR, _("Sending packet to %s via %s (%s)"),
 432                            n->name, via->name, n->via->hostname);
 433
 434         if((myself->options | via->options) & OPTION_TCPONLY) {
 435                 if(!send_tcppacket(via->connection, packet))
 436                         terminate_connection(via->connection, true);
 437         } else
 438                 send_udppacket(via, packet);
 439 }
 440
 441 /* Broadcast a packet using the minimum spanning tree */
 442
 443 void broadcast_packet(const node_t *from, vpn_packet_t *packet)
 444 {
 445         avl_node_t *node;
 446         connection_t *c;
 447
 448         cp();
 449
 450         ifdebug(TRAFFIC) logger(LOG_INFO, _("Broadcasting packet of %d bytes from %s (%s)"),
 451                            packet->len, from->name, from->hostname);
 452
 453         for(node = connection_tree->head; node; node = node->next) {
 454                 c = node->data;
 455
 456                 if(c->status.active && c->status.mst && c != from->nexthop->connection)
 457                         send_packet(c->node, packet);
 458         }
 459 }
 460
 461 void flush_queue(node_t *n)
 462 {
 463         list_node_t *node, *next;
 464
 465         cp();
 466
 467         ifdebug(TRAFFIC) logger(LOG_INFO, _("Flushing queue for %s (%s)"), n->name, n->hostname);
 468
 469         for(node = n->queue->head; node; node = next) {
 470                 next = node->next;
 471                 send_udppacket(n, node->data);
 472                 list_delete_node(n->queue, node);
 473         }
 474 }
 475
 476 void handle_incoming_vpn_data(int sock)
 477 {
 478         vpn_packet_t pkt;
 479         char *hostname;
 480         sockaddr_t from;
 481         socklen_t fromlen = sizeof(from);
 482         node_t *n;
 483
 484         cp();
 485
 486         pkt.len = recvfrom(sock, (char *) &pkt.seqno, MAXSIZE, 0, &from.sa, &fromlen);
 487
 488         if(pkt.len < 0) {
 489                 logger(LOG_ERR, _("Receiving packet failed: %s"), strerror(errno));
 490                 return;
 491         }
 492
 493         sockaddrunmap(&from);           /* Some braindead IPv6 implementations do stupid things. */
 494
 495         n = lookup_node_udp(&from);
 496
 497         if(!n) {
 498                 hostname = sockaddr2hostname(&from);
 499                 logger(LOG_WARNING, _("Received UDP packet from unknown source %s"),
 500                            hostname);
 501                 free(hostname);
 502                 return;
 503         }
 504
 505         receive_udppacket(n, &pkt);
 506 }