src/net_packet.c

   1 /*
   2     net_packet.c -- Handles in- and outgoing VPN packets
   3     Copyright (C) 1998-2005 Ivo Timmermans,
   4                   2000-2009 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 along
  17     with this program; if not, write to the Free Software Foundation, Inc.,
  18     51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  19 */
  20
  21 #include "system.h"
  22
  23 #include <openssl/rand.h>
  24 #include <openssl/err.h>
  25 #include <openssl/evp.h>
  26 #include <openssl/pem.h>
  27 #include <openssl/hmac.h>
  28
  29 #include <zlib.h>
  30 #include LZO1X_H
  31
  32 #include "avl_tree.h"
  33 #include "conf.h"
  34 #include "connection.h"
  35 #include "device.h"
  36 #include "ethernet.h"
  37 #include "event.h"
  38 #include "graph.h"
  39 #include "list.h"
  40 #include "logger.h"
  41 #include "net.h"
  42 #include "netutl.h"
  43 #include "protocol.h"
  44 #include "process.h"
  45 #include "route.h"
  46 #include "utils.h"
  47 #include "xalloc.h"
  48
  49 #ifdef WSAEMSGSIZE
  50 #define EMSGSIZE WSAEMSGSIZE
  51 #endif
  52
  53 int keylifetime = 0;
  54 int keyexpires = 0;
  55 static char lzo_wrkmem[LZO1X_999_MEM_COMPRESS > LZO1X_1_MEM_COMPRESS ? LZO1X_999_MEM_COMPRESS : LZO1X_1_MEM_COMPRESS];
  56
  57 static void send_udppacket(node_t *, vpn_packet_t *);
  58
  59 #define MAX_SEQNO 1073741824
  60
  61 // mtuprobes == 1..30: initial discovery, send bursts with 1 second interval
  62 // mtuprobes ==    31: sleep pinginterval seconds
  63 // mtuprobes ==    32: send 1 burst, sleep pingtimeout second
  64 // mtuprobes ==    33: no response from other side, restart PMTU discovery process
  65
  66 void send_mtu_probe(node_t *n) {
  67         vpn_packet_t packet;
  68         int len, i;
  69         int timeout = 1;
  70
  71         n->mtuprobes++;
  72         n->mtuevent = NULL;
  73
  74         if(!n->status.reachable || !n->status.validkey) {
  75                 ifdebug(TRAFFIC) logger(LOG_INFO, "Trying to send MTU probe to unreachable or rekeying node %s (%s)", n->name, n->hostname);
  76                 n->mtuprobes = 0;
  77                 return;
  78         }
  79
  80         if(n->mtuprobes > 32) {
  81                 ifdebug(TRAFFIC) logger(LOG_INFO, "%s (%s) did not respond to UDP ping, restarting PMTU discovery", n->name, n->hostname);
  82                 n->mtuprobes = 1;
  83                 n->minmtu = 0;
  84                 n->maxmtu = MTU;
  85         }
  86
  87         if(n->mtuprobes >= 10 && !n->minmtu) {
  88                 ifdebug(TRAFFIC) logger(LOG_INFO, "No response to MTU probes from %s (%s)", n->name, n->hostname);
  89                 n->mtuprobes = 0;
  90                 return;
  91         }
  92
  93         if(n->mtuprobes == 30 || (n->mtuprobes < 30 && n->minmtu >= n->maxmtu)) {
  94                 if(n->minmtu > n->maxmtu)
  95                         n->minmtu = n->maxmtu;
  96                 else
  97                         n->maxmtu = n->minmtu;
  98                 n->mtu = n->minmtu;
  99                 ifdebug(TRAFFIC) logger(LOG_INFO, "Fixing MTU of %s (%s) to %d after %d probes", n->name, n->hostname, n->mtu, n->mtuprobes);
 100                 n->mtuprobes = 31;
 101         }
 102
 103         if(n->mtuprobes == 31) {
 104                 timeout = pinginterval;
 105                 goto end;
 106         } else if(n->mtuprobes == 32) {
 107                 timeout = pingtimeout;
 108         }
 109
 110         for(i = 0; i < 3; i++) {
 111                 if(n->maxmtu <= n->minmtu)
 112                         len = n->maxmtu;
 113                 else
 114                         len = n->minmtu + 1 + rand() % (n->maxmtu - n->minmtu);
 115
 116                 if(len < 64)
 117                         len = 64;
 118
 119                 memset(packet.data, 0, 14);
 120                 RAND_pseudo_bytes(packet.data + 14, len - 14);
 121                 packet.len = len;
 122                 packet.priority = 0;
 123
 124                 ifdebug(TRAFFIC) logger(LOG_INFO, "Sending MTU probe length %d to %s (%s)", len, n->name, n->hostname);
 125
 126                 send_udppacket(n, &packet);
 127         }
 128
 129 end:
 130         n->mtuevent = new_event();
 131         n->mtuevent->handler = (event_handler_t)send_mtu_probe;
 132         n->mtuevent->data = n;
 133         n->mtuevent->time = now + timeout;
 134         event_add(n->mtuevent);
 135 }
 136
 137 void mtu_probe_h(node_t *n, vpn_packet_t *packet, length_t len) {
 138         ifdebug(TRAFFIC) logger(LOG_INFO, "Got MTU probe length %d from %s (%s)", packet->len, n->name, n->hostname);
 139
 140         if(!packet->data[0]) {
 141                 packet->data[0] = 1;
 142                 send_udppacket(n, packet);
 143         } else {
 144                 if(len > n->maxmtu)
 145                         len = n->maxmtu;
 146                 if(n->minmtu < len)
 147                         n->minmtu = len;
 148                 if(n->mtuprobes > 30)
 149                         n->mtuprobes = 30;
 150         }
 151 }
 152
 153 static length_t compress_packet(uint8_t *dest, const uint8_t *source, length_t len, int level) {
 154         if(level == 10) {
 155                 lzo_uint lzolen = MAXSIZE;
 156                 lzo1x_1_compress(source, len, dest, &lzolen, lzo_wrkmem);
 157                 return lzolen;
 158         } else if(level < 10) {
 159                 unsigned long destlen = MAXSIZE;
 160                 if(compress2(dest, &destlen, source, len, level) == Z_OK)
 161                         return destlen;
 162                 else
 163                         return -1;
 164         } else {
 165                 lzo_uint lzolen = MAXSIZE;
 166                 lzo1x_999_compress(source, len, dest, &lzolen, lzo_wrkmem);
 167                 return lzolen;
 168         }
 169
 170         return -1;
 171 }
 172
 173 static length_t uncompress_packet(uint8_t *dest, const uint8_t *source, length_t len, int level) {
 174         if(level > 9) {
 175                 lzo_uint lzolen = MAXSIZE;
 176                 if(lzo1x_decompress_safe(source, len, dest, &lzolen, NULL) == LZO_E_OK)
 177                         return lzolen;
 178                 else
 179                         return -1;
 180         } else {
 181                 unsigned long destlen = MAXSIZE;
 182                 if(uncompress(dest, &destlen, source, len) == Z_OK)
 183                         return destlen;
 184                 else
 185                         return -1;
 186         }
 187
 188         return -1;
 189 }
 190
 191 /* VPN packet I/O */
 192
 193 static void receive_packet(node_t *n, vpn_packet_t *packet) {
 194         ifdebug(TRAFFIC) logger(LOG_DEBUG, "Received packet of %d bytes from %s (%s)",
 195                            packet->len, n->name, n->hostname);
 196
 197         route(n, packet);
 198 }
 199
 200 static bool try_mac(const node_t *n, const vpn_packet_t *inpkt) {
 201         unsigned char hmac[EVP_MAX_MD_SIZE];
 202
 203         if(!n->indigest || !n->inmaclength || !n->inkey || inpkt->len < sizeof inpkt->seqno + n->inmaclength)
 204                 return false;
 205
 206         HMAC(n->indigest, n->inkey, n->inkeylength, (unsigned char *) &inpkt->seqno, inpkt->len - n->inmaclength, (unsigned char *)hmac, NULL);
 207
 208         return !memcmp(hmac, (char *) &inpkt->seqno + inpkt->len - n->inmaclength, n->inmaclength);
 209 }
 210
 211 static void receive_udppacket(node_t *n, vpn_packet_t *inpkt) {
 212         vpn_packet_t pkt1, pkt2;
 213         vpn_packet_t *pkt[] = { &pkt1, &pkt2, &pkt1, &pkt2 };
 214         int nextpkt = 0;
 215         vpn_packet_t *outpkt = pkt[0];
 216         int outlen, outpad;
 217         unsigned char hmac[EVP_MAX_MD_SIZE];
 218         int i;
 219
 220         if(!n->inkey) {
 221                 ifdebug(TRAFFIC) logger(LOG_DEBUG, "Got packet from %s (%s) but he hasn't got our key yet",
 222                                         n->name, n->hostname);
 223                 return;
 224         }
 225
 226         /* Check packet length */
 227
 228         if(inpkt->len < sizeof(inpkt->seqno) + n->inmaclength) {
 229                 ifdebug(TRAFFIC) logger(LOG_DEBUG, "Got too short packet from %s (%s)",
 230                                         n->name, n->hostname);
 231                 return;
 232         }
 233
 234         /* Check the message authentication code */
 235
 236         if(n->indigest && n->inmaclength) {
 237                 inpkt->len -= n->inmaclength;
 238                 HMAC(n->indigest, n->inkey, n->inkeylength,
 239                          (unsigned char *) &inpkt->seqno, inpkt->len, (unsigned char *)hmac, NULL);
 240
 241                 if(memcmp(hmac, (char *) &inpkt->seqno + inpkt->len, n->inmaclength)) {
 242                         ifdebug(TRAFFIC) logger(LOG_DEBUG, "Got unauthenticated packet from %s (%s)",
 243                                            n->name, n->hostname);
 244                         return;
 245                 }
 246         }
 247
 248         /* Decrypt the packet */
 249
 250         if(n->incipher) {
 251                 outpkt = pkt[nextpkt++];
 252
 253                 if(!EVP_DecryptInit_ex(&n->inctx, NULL, NULL, NULL, NULL)
 254                                 || !EVP_DecryptUpdate(&n->inctx, (unsigned char *) &outpkt->seqno, &outlen,
 255                                         (unsigned char *) &inpkt->seqno, inpkt->len)
 256                                 || !EVP_DecryptFinal_ex(&n->inctx, (unsigned char *) &outpkt->seqno + outlen, &outpad)) {
 257                         ifdebug(TRAFFIC) logger(LOG_DEBUG, "Error decrypting packet from %s (%s): %s",
 258                                                 n->name, n->hostname, ERR_error_string(ERR_get_error(), NULL));
 259                         return;
 260                 }
 261
 262                 outpkt->len = outlen + outpad;
 263                 inpkt = outpkt;
 264         }
 265
 266         /* Check the sequence number */
 267
 268         inpkt->len -= sizeof(inpkt->seqno);
 269         inpkt->seqno = ntohl(inpkt->seqno);
 270
 271         if(inpkt->seqno != n->received_seqno + 1) {
 272                 if(inpkt->seqno >= n->received_seqno + sizeof(n->late) * 8) {
 273                         logger(LOG_WARNING, "Lost %d packets from %s (%s)",
 274                                            inpkt->seqno - n->received_seqno - 1, n->name, n->hostname);
 275
 276                         memset(n->late, 0, sizeof(n->late));
 277                 } else if (inpkt->seqno <= n->received_seqno) {
 278                         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))) {
 279                                 logger(LOG_WARNING, "Got late or replayed packet from %s (%s), seqno %d, last received %d",
 280                                            n->name, n->hostname, inpkt->seqno, n->received_seqno);
 281                                 return;
 282                         }
 283                 } else {
 284                         for(i = n->received_seqno + 1; i < inpkt->seqno; i++)
 285                                 n->late[(i / 8) % sizeof(n->late)] |= 1 << i % 8;
 286                 }
 287         }
 288
 289         n->late[(inpkt->seqno / 8) % sizeof(n->late)] &= ~(1 << inpkt->seqno % 8);
 290
 291         if(inpkt->seqno > n->received_seqno)
 292                 n->received_seqno = inpkt->seqno;
 293
 294         if(n->received_seqno > MAX_SEQNO)
 295                 keyexpires = 0;
 296
 297         /* Decompress the packet */
 298
 299         length_t origlen = inpkt->len;
 300
 301         if(n->incompression) {
 302                 outpkt = pkt[nextpkt++];
 303
 304                 if((outpkt->len = uncompress_packet(outpkt->data, inpkt->data, inpkt->len, n->incompression)) < 0) {
 305                         ifdebug(TRAFFIC) logger(LOG_ERR, "Error while uncompressing packet from %s (%s)",
 306                                                  n->name, n->hostname);
 307                         return;
 308                 }
 309
 310                 inpkt = outpkt;
 311
 312                 origlen -= MTU/64 + 20;
 313         }
 314
 315         inpkt->priority = 0;
 316
 317         if(!inpkt->data[12] && !inpkt->data[13])
 318                 mtu_probe_h(n, inpkt, origlen);
 319         else
 320                 receive_packet(n, inpkt);
 321 }
 322
 323 void receive_tcppacket(connection_t *c, char *buffer, int len) {
 324         vpn_packet_t outpkt;
 325
 326         outpkt.len = len;
 327         if(c->options & OPTION_TCPONLY)
 328                 outpkt.priority = 0;
 329         else
 330                 outpkt.priority = -1;
 331         memcpy(outpkt.data, buffer, len);
 332
 333         receive_packet(c->node, &outpkt);
 334 }
 335
 336 static void send_udppacket(node_t *n, vpn_packet_t *origpkt) {
 337         vpn_packet_t pkt1, pkt2;
 338         vpn_packet_t *pkt[] = { &pkt1, &pkt2, &pkt1, &pkt2 };
 339         vpn_packet_t *inpkt = origpkt;
 340         int nextpkt = 0;
 341         vpn_packet_t *outpkt;
 342         int origlen;
 343         int outlen, outpad;
 344         static int priority = 0;
 345         int origpriority;
 346         int sock;
 347
 348         if(!n->status.reachable) {
 349                 ifdebug(TRAFFIC) logger(LOG_INFO, "Trying to send UDP packet to unreachable node %s (%s)", n->name, n->hostname);
 350                 return;
 351         }
 352
 353         /* Make sure we have a valid key */
 354
 355         if(!n->status.validkey) {
 356                 ifdebug(TRAFFIC) logger(LOG_INFO,
 357                                    "No valid key known yet for %s (%s), forwarding via TCP",
 358                                    n->name, n->hostname);
 359
 360                 if(!n->status.waitingforkey)
 361                         send_req_key(n);
 362
 363                 n->status.waitingforkey = true;
 364
 365                 send_tcppacket(n->nexthop->connection, origpkt);
 366
 367                 return;
 368         }
 369
 370         if(n->options & OPTION_PMTU_DISCOVERY && inpkt->len > n->minmtu && (inpkt->data[12] | inpkt->data[13])) {
 371                 ifdebug(TRAFFIC) logger(LOG_INFO,
 372                                 "Packet for %s (%s) larger than minimum MTU, forwarding via %s",
 373                                 n->name, n->hostname, n != n->nexthop ? n->nexthop->name : "TCP");
 374
 375                 if(n != n->nexthop)
 376                         send_packet(n->nexthop, origpkt);
 377                 else
 378                         send_tcppacket(n->nexthop->connection, origpkt);
 379
 380                 return;
 381         }
 382
 383         origlen = inpkt->len;
 384         origpriority = inpkt->priority;
 385
 386         /* Compress the packet */
 387
 388         if(n->outcompression) {
 389                 outpkt = pkt[nextpkt++];
 390
 391                 if((outpkt->len = compress_packet(outpkt->data, inpkt->data, inpkt->len, n->outcompression)) < 0) {
 392                         ifdebug(TRAFFIC) logger(LOG_ERR, "Error while compressing packet to %s (%s)",
 393                                    n->name, n->hostname);
 394                         return;
 395                 }
 396
 397                 inpkt = outpkt;
 398         }
 399
 400         /* Add sequence number */
 401
 402         inpkt->seqno = htonl(++(n->sent_seqno));
 403         inpkt->len += sizeof(inpkt->seqno);
 404
 405         /* Encrypt the packet */
 406
 407         if(n->outcipher) {
 408                 outpkt = pkt[nextpkt++];
 409
 410                 if(!EVP_EncryptInit_ex(&n->outctx, NULL, NULL, NULL, NULL)
 411                                 || !EVP_EncryptUpdate(&n->outctx, (unsigned char *) &outpkt->seqno, &outlen,
 412                                         (unsigned char *) &inpkt->seqno, inpkt->len)
 413                                 || !EVP_EncryptFinal_ex(&n->outctx, (unsigned char *) &outpkt->seqno + outlen, &outpad)) {
 414                         ifdebug(TRAFFIC) logger(LOG_ERR, "Error while encrypting packet to %s (%s): %s",
 415                                                 n->name, n->hostname, ERR_error_string(ERR_get_error(), NULL));
 416                         goto end;
 417                 }
 418
 419                 outpkt->len = outlen + outpad;
 420                 inpkt = outpkt;
 421         }
 422
 423         /* Add the message authentication code */
 424
 425         if(n->outdigest && n->outmaclength) {
 426                 HMAC(n->outdigest, n->outkey, n->outkeylength, (unsigned char *) &inpkt->seqno,
 427                          inpkt->len, (unsigned char *) &inpkt->seqno + inpkt->len, NULL);
 428                 inpkt->len += n->outmaclength;
 429         }
 430
 431         /* Determine which socket we have to use */
 432
 433         for(sock = 0; sock < listen_sockets; sock++)
 434                 if(n->address.sa.sa_family == listen_socket[sock].sa.sa.sa_family)
 435                         break;
 436
 437         if(sock >= listen_sockets)
 438                 sock = 0;                               /* If none is available, just use the first and hope for the best. */
 439
 440         /* Send the packet */
 441
 442 #if defined(SOL_IP) && defined(IP_TOS)
 443         if(priorityinheritance && origpriority != priority
 444            && listen_socket[sock].sa.sa.sa_family == AF_INET) {
 445                 priority = origpriority;
 446                 ifdebug(TRAFFIC) logger(LOG_DEBUG, "Setting outgoing packet priority to %d", priority);
 447                 if(setsockopt(listen_socket[sock].udp, SOL_IP, IP_TOS, &priority, sizeof(priority)))    /* SO_PRIORITY doesn't seem to work */
 448                         logger(LOG_ERR, "System call `%s' failed: %s", "setsockopt", strerror(errno));
 449         }
 450 #endif
 451
 452         if((sendto(listen_socket[sock].udp, (char *) &inpkt->seqno, inpkt->len, 0, &(n->address.sa), SALEN(n->address.sa))) < 0) {
 453                 if(errno == EMSGSIZE) {
 454                         if(n->maxmtu >= origlen)
 455                                 n->maxmtu = origlen - 1;
 456                         if(n->mtu >= origlen)
 457                                 n->mtu = origlen - 1;
 458                 } else
 459                         logger(LOG_ERR, "Error sending packet to %s (%s): %s", n->name, n->hostname, strerror(errno));
 460         }
 461
 462 end:
 463         origpkt->len = origlen;
 464 }
 465
 466 /*
 467   send a packet to the given vpn ip.
 468 */
 469 void send_packet(const node_t *n, vpn_packet_t *packet) {
 470         node_t *via;
 471
 472         if(n == myself) {
 473                 if(overwrite_mac)
 474                          memcpy(packet->data, mymac.x, ETH_ALEN);
 475                 write_packet(packet);
 476                 return;
 477         }
 478
 479         ifdebug(TRAFFIC) logger(LOG_ERR, "Sending packet of %d bytes to %s (%s)",
 480                            packet->len, n->name, n->hostname);
 481
 482         if(!n->status.reachable) {
 483                 ifdebug(TRAFFIC) logger(LOG_INFO, "Node %s (%s) is not reachable",
 484                                    n->name, n->hostname);
 485                 return;
 486         }
 487
 488         via = (packet->priority == -1 || n->via == myself) ? n->nexthop : n->via;
 489
 490         if(via != n)
 491                 ifdebug(TRAFFIC) logger(LOG_INFO, "Sending packet to %s via %s (%s)",
 492                            n->name, via->name, n->via->hostname);
 493
 494         if(packet->priority == -1 || ((myself->options | via->options) & OPTION_TCPONLY)) {
 495                 if(!send_tcppacket(via->connection, packet))
 496                         terminate_connection(via->connection, true);
 497         } else
 498                 send_udppacket(via, packet);
 499 }
 500
 501 /* Broadcast a packet using the minimum spanning tree */
 502
 503 void broadcast_packet(const node_t *from, vpn_packet_t *packet) {
 504         avl_node_t *node;
 505         connection_t *c;
 506
 507         ifdebug(TRAFFIC) logger(LOG_INFO, "Broadcasting packet of %d bytes from %s (%s)",
 508                            packet->len, from->name, from->hostname);
 509
 510         if(from != myself) {
 511                 send_packet(myself, packet);
 512
 513                 // In TunnelServer mode, do not forward broadcast packets.
 514                 // The MST might not be valid and create loops.
 515                 if(tunnelserver)
 516                         return;
 517         }
 518
 519         for(node = connection_tree->head; node; node = node->next) {
 520                 c = node->data;
 521
 522                 if(c->status.active && c->status.mst && c != from->nexthop->connection)
 523                         send_packet(c->node, packet);
 524         }
 525 }
 526
 527 static node_t *try_harder(const sockaddr_t *from, const vpn_packet_t *pkt) {
 528         avl_node_t *node;
 529         edge_t *e;
 530         node_t *n = NULL;
 531         static time_t last_hard_try = 0;
 532
 533         for(node = edge_weight_tree->head; node; node = node->next) {
 534                 e = node->data;
 535
 536                 if(sockaddrcmp_noport(from, &e->address)) {
 537                         if(last_hard_try == now)
 538                                 continue;
 539                         last_hard_try = now;
 540                 }
 541
 542                 if(!n)
 543                         n = e->to;
 544
 545                 if(!try_mac(e->to, pkt))
 546                         continue;
 547
 548                 n = e->to;
 549                 break;
 550         }
 551
 552         return n;
 553 }
 554
 555 void handle_incoming_vpn_data(int sock) {
 556         vpn_packet_t pkt;
 557         char *hostname;
 558         sockaddr_t from;
 559         socklen_t fromlen = sizeof(from);
 560         node_t *n;
 561
 562         pkt.len = recvfrom(sock, (char *) &pkt.seqno, MAXSIZE, 0, &from.sa, &fromlen);
 563
 564         if(pkt.len < 0) {
 565                 if(errno != EAGAIN && errno != EINTR)
 566                         logger(LOG_ERR, "Receiving packet failed: %s", strerror(errno));
 567                 return;
 568         }
 569
 570         sockaddrunmap(&from);           /* Some braindead IPv6 implementations do stupid things. */
 571
 572         n = lookup_node_udp(&from);
 573
 574         if(!n) {
 575                 n = try_harder(&from, &pkt);
 576                 if(n)
 577                         update_node_udp(n, &from);
 578                 else ifdebug(PROTOCOL) {
 579                         hostname = sockaddr2hostname(&from);
 580                         logger(LOG_WARNING, "Received UDP packet from unknown source %s", hostname);
 581                         free(hostname);
 582                         return;
 583                 }
 584                 else
 585                         return;
 586         }
 587
 588         receive_udppacket(n, &pkt);
 589 }