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                   2000-2009 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 HAVE_MINGW
  50 #include <winerror.h>
  51 #define EMSGSIZE WSAEMSGSIZE
  52 #define EAGAIN WSATRY_AGAIN
  53 #define EINTR WSAEINTR
  54 #define sockstrerror(x) winerror(x)
  55 #define sockerrno WSAGetLastError()
  56 #else
  57 #define sockstrerror(x) strerror(x)
  58 #define sockerrno errno
  59 #endif
  60
  61 int keylifetime = 0;
  62 int keyexpires = 0;
  63 static char lzo_wrkmem[LZO1X_999_MEM_COMPRESS > LZO1X_1_MEM_COMPRESS ? LZO1X_999_MEM_COMPRESS : LZO1X_1_MEM_COMPRESS];
  64
  65 static void send_udppacket(node_t *, vpn_packet_t *);
  66
  67 #define MAX_SEQNO 1073741824
  68
  69 // mtuprobes == 1..30: initial discovery, send bursts with 1 second interval
  70 // mtuprobes ==    31: sleep pinginterval seconds
  71 // mtuprobes ==    32: send 1 burst, sleep pingtimeout second
  72 // mtuprobes ==    33: no response from other side, restart PMTU discovery process
  73
  74 void send_mtu_probe(node_t *n) {
  75         vpn_packet_t packet;
  76         int len, i;
  77         int timeout = 1;
  78
  79         n->mtuprobes++;
  80         n->mtuevent = NULL;
  81
  82         if(!n->status.reachable || !n->status.validkey) {
  83                 ifdebug(TRAFFIC) logger(LOG_INFO, "Trying to send MTU probe to unreachable or rekeying node %s (%s)", n->name, n->hostname);
  84                 n->mtuprobes = 0;
  85                 return;
  86         }
  87
  88         if(n->mtuprobes > 32) {
  89                 ifdebug(TRAFFIC) logger(LOG_INFO, "%s (%s) did not respond to UDP ping, restarting PMTU discovery", n->name, n->hostname);
  90                 n->mtuprobes = 1;
  91                 n->minmtu = 0;
  92                 n->maxmtu = MTU;
  93         }
  94
  95         if(n->mtuprobes >= 10 && !n->minmtu) {
  96                 ifdebug(TRAFFIC) logger(LOG_INFO, "No response to MTU probes from %s (%s)", n->name, n->hostname);
  97                 n->mtuprobes = 0;
  98                 return;
  99         }
 100
 101         if(n->mtuprobes == 30 || (n->mtuprobes < 30 && n->minmtu >= n->maxmtu)) {
 102                 if(n->minmtu > n->maxmtu)
 103                         n->minmtu = n->maxmtu;
 104                 else
 105                         n->maxmtu = n->minmtu;
 106                 n->mtu = n->minmtu;
 107                 ifdebug(TRAFFIC) logger(LOG_INFO, "Fixing MTU of %s (%s) to %d after %d probes", n->name, n->hostname, n->mtu, n->mtuprobes);
 108                 n->mtuprobes = 31;
 109         }
 110
 111         if(n->mtuprobes == 31) {
 112                 timeout = pinginterval;
 113                 goto end;
 114         } else if(n->mtuprobes == 32) {
 115                 timeout = pingtimeout;
 116         }
 117
 118         for(i = 0; i < 3; i++) {
 119                 if(n->maxmtu <= n->minmtu)
 120                         len = n->maxmtu;
 121                 else
 122                         len = n->minmtu + 1 + rand() % (n->maxmtu - n->minmtu);
 123
 124                 if(len < 64)
 125                         len = 64;
 126
 127                 memset(packet.data, 0, 14);
 128                 RAND_pseudo_bytes(packet.data + 14, len - 14);
 129                 packet.len = len;
 130                 packet.priority = 0;
 131
 132                 ifdebug(TRAFFIC) logger(LOG_INFO, "Sending MTU probe length %d to %s (%s)", len, n->name, n->hostname);
 133
 134                 send_udppacket(n, &packet);
 135         }
 136
 137 end:
 138         n->mtuevent = new_event();
 139         n->mtuevent->handler = (event_handler_t)send_mtu_probe;
 140         n->mtuevent->data = n;
 141         n->mtuevent->time = now + timeout;
 142         event_add(n->mtuevent);
 143 }
 144
 145 void mtu_probe_h(node_t *n, vpn_packet_t *packet, length_t len) {
 146         ifdebug(TRAFFIC) logger(LOG_INFO, "Got MTU probe length %d from %s (%s)", packet->len, n->name, n->hostname);
 147
 148         if(!packet->data[0]) {
 149                 packet->data[0] = 1;
 150                 send_udppacket(n, packet);
 151         } else {
 152                 if(len > n->maxmtu)
 153                         len = n->maxmtu;
 154                 if(n->minmtu < len)
 155                         n->minmtu = len;
 156                 if(n->mtuprobes > 30)
 157                         n->mtuprobes = 30;
 158         }
 159 }
 160
 161 static length_t compress_packet(uint8_t *dest, const uint8_t *source, length_t len, int level) {
 162         if(level == 10) {
 163                 lzo_uint lzolen = MAXSIZE;
 164                 lzo1x_1_compress(source, len, dest, &lzolen, lzo_wrkmem);
 165                 return lzolen;
 166         } else if(level < 10) {
 167                 unsigned long destlen = MAXSIZE;
 168                 if(compress2(dest, &destlen, source, len, level) == Z_OK)
 169                         return destlen;
 170                 else
 171                         return -1;
 172         } else {
 173                 lzo_uint lzolen = MAXSIZE;
 174                 lzo1x_999_compress(source, len, dest, &lzolen, lzo_wrkmem);
 175                 return lzolen;
 176         }
 177
 178         return -1;
 179 }
 180
 181 static length_t uncompress_packet(uint8_t *dest, const uint8_t *source, length_t len, int level) {
 182         if(level > 9) {
 183                 lzo_uint lzolen = MAXSIZE;
 184                 if(lzo1x_decompress_safe(source, len, dest, &lzolen, NULL) == LZO_E_OK)
 185                         return lzolen;
 186                 else
 187                         return -1;
 188         } else {
 189                 unsigned long destlen = MAXSIZE;
 190                 if(uncompress(dest, &destlen, source, len) == Z_OK)
 191                         return destlen;
 192                 else
 193                         return -1;
 194         }
 195
 196         return -1;
 197 }
 198
 199 /* VPN packet I/O */
 200
 201 static void receive_packet(node_t *n, vpn_packet_t *packet) {
 202         ifdebug(TRAFFIC) logger(LOG_DEBUG, "Received packet of %d bytes from %s (%s)",
 203                            packet->len, n->name, n->hostname);
 204
 205         route(n, packet);
 206 }
 207
 208 static bool try_mac(const node_t *n, const vpn_packet_t *inpkt) {
 209         unsigned char hmac[EVP_MAX_MD_SIZE];
 210
 211         if(!n->indigest || !n->inmaclength || !n->inkey || inpkt->len < sizeof inpkt->seqno + n->inmaclength)
 212                 return false;
 213
 214         HMAC(n->indigest, n->inkey, n->inkeylength, (unsigned char *) &inpkt->seqno, inpkt->len - n->inmaclength, (unsigned char *)hmac, NULL);
 215
 216         return !memcmp(hmac, (char *) &inpkt->seqno + inpkt->len - n->inmaclength, n->inmaclength);
 217 }
 218
 219 static void receive_udppacket(node_t *n, vpn_packet_t *inpkt) {
 220         vpn_packet_t pkt1, pkt2;
 221         vpn_packet_t *pkt[] = { &pkt1, &pkt2, &pkt1, &pkt2 };
 222         int nextpkt = 0;
 223         vpn_packet_t *outpkt = pkt[0];
 224         int outlen, outpad;
 225         unsigned char hmac[EVP_MAX_MD_SIZE];
 226         int i;
 227
 228         if(!n->inkey) {
 229                 ifdebug(TRAFFIC) logger(LOG_DEBUG, "Got packet from %s (%s) but he hasn't got our key yet",
 230                                         n->name, n->hostname);
 231                 return;
 232         }
 233
 234         /* Check packet length */
 235
 236         if(inpkt->len < sizeof(inpkt->seqno) + n->inmaclength) {
 237                 ifdebug(TRAFFIC) logger(LOG_DEBUG, "Got too short packet from %s (%s)",
 238                                         n->name, n->hostname);
 239                 return;
 240         }
 241
 242         /* Check the message authentication code */
 243
 244         if(n->indigest && n->inmaclength) {
 245                 inpkt->len -= n->inmaclength;
 246                 HMAC(n->indigest, n->inkey, n->inkeylength,
 247                          (unsigned char *) &inpkt->seqno, inpkt->len, (unsigned char *)hmac, NULL);
 248
 249                 if(memcmp(hmac, (char *) &inpkt->seqno + inpkt->len, n->inmaclength)) {
 250                         ifdebug(TRAFFIC) logger(LOG_DEBUG, "Got unauthenticated packet from %s (%s)",
 251                                            n->name, n->hostname);
 252                         return;
 253                 }
 254         }
 255
 256         /* Decrypt the packet */
 257
 258         if(n->incipher) {
 259                 outpkt = pkt[nextpkt++];
 260
 261                 if(!EVP_DecryptInit_ex(&n->inctx, NULL, NULL, NULL, NULL)
 262                                 || !EVP_DecryptUpdate(&n->inctx, (unsigned char *) &outpkt->seqno, &outlen,
 263                                         (unsigned char *) &inpkt->seqno, inpkt->len)
 264                                 || !EVP_DecryptFinal_ex(&n->inctx, (unsigned char *) &outpkt->seqno + outlen, &outpad)) {
 265                         ifdebug(TRAFFIC) logger(LOG_DEBUG, "Error decrypting packet from %s (%s): %s",
 266                                                 n->name, n->hostname, ERR_error_string(ERR_get_error(), NULL));
 267                         return;
 268                 }
 269
 270                 outpkt->len = outlen + outpad;
 271                 inpkt = outpkt;
 272         }
 273
 274         /* Check the sequence number */
 275
 276         inpkt->len -= sizeof(inpkt->seqno);
 277         inpkt->seqno = ntohl(inpkt->seqno);
 278
 279         if(inpkt->seqno != n->received_seqno + 1) {
 280                 if(inpkt->seqno >= n->received_seqno + sizeof(n->late) * 8) {
 281                         logger(LOG_WARNING, "Lost %d packets from %s (%s)",
 282                                            inpkt->seqno - n->received_seqno - 1, n->name, n->hostname);
 283
 284                         memset(n->late, 0, sizeof(n->late));
 285                 } else if (inpkt->seqno <= n->received_seqno) {
 286                         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))) {
 287                                 logger(LOG_WARNING, "Got late or replayed packet from %s (%s), seqno %d, last received %d",
 288                                            n->name, n->hostname, inpkt->seqno, n->received_seqno);
 289                                 return;
 290                         }
 291                 } else {
 292                         for(i = n->received_seqno + 1; i < inpkt->seqno; i++)
 293                                 n->late[(i / 8) % sizeof(n->late)] |= 1 << i % 8;
 294                 }
 295         }
 296
 297         n->late[(inpkt->seqno / 8) % sizeof(n->late)] &= ~(1 << inpkt->seqno % 8);
 298
 299         if(inpkt->seqno > n->received_seqno)
 300                 n->received_seqno = inpkt->seqno;
 301
 302         if(n->received_seqno > MAX_SEQNO)
 303                 keyexpires = 0;
 304
 305         /* Decompress the packet */
 306
 307         length_t origlen = inpkt->len;
 308
 309         if(n->incompression) {
 310                 outpkt = pkt[nextpkt++];
 311
 312                 if((outpkt->len = uncompress_packet(outpkt->data, inpkt->data, inpkt->len, n->incompression)) < 0) {
 313                         ifdebug(TRAFFIC) logger(LOG_ERR, "Error while uncompressing packet from %s (%s)",
 314                                                  n->name, n->hostname);
 315                         return;
 316                 }
 317
 318                 inpkt = outpkt;
 319
 320                 origlen -= MTU/64 + 20;
 321         }
 322
 323         inpkt->priority = 0;
 324
 325         if(!inpkt->data[12] && !inpkt->data[13])
 326                 mtu_probe_h(n, inpkt, origlen);
 327         else
 328                 receive_packet(n, inpkt);
 329 }
 330
 331 void receive_tcppacket(connection_t *c, char *buffer, int len) {
 332         vpn_packet_t outpkt;
 333
 334         outpkt.len = len;
 335         if(c->options & OPTION_TCPONLY)
 336                 outpkt.priority = 0;
 337         else
 338                 outpkt.priority = -1;
 339         memcpy(outpkt.data, buffer, len);
 340
 341         receive_packet(c->node, &outpkt);
 342 }
 343
 344 static void send_udppacket(node_t *n, vpn_packet_t *origpkt) {
 345         vpn_packet_t pkt1, pkt2;
 346         vpn_packet_t *pkt[] = { &pkt1, &pkt2, &pkt1, &pkt2 };
 347         vpn_packet_t *inpkt = origpkt;
 348         int nextpkt = 0;
 349         vpn_packet_t *outpkt;
 350         int origlen;
 351         int outlen, outpad;
 352         static int priority = 0;
 353         int origpriority;
 354         int sock;
 355
 356         if(!n->status.reachable) {
 357                 ifdebug(TRAFFIC) logger(LOG_INFO, "Trying to send UDP packet to unreachable node %s (%s)", n->name, n->hostname);
 358                 return;
 359         }
 360
 361         /* Make sure we have a valid key */
 362
 363         if(!n->status.validkey) {
 364                 ifdebug(TRAFFIC) logger(LOG_INFO,
 365                                    "No valid key known yet for %s (%s), forwarding via TCP",
 366                                    n->name, n->hostname);
 367
 368                 if(!n->status.waitingforkey)
 369                         send_req_key(n);
 370
 371                 n->status.waitingforkey = true;
 372
 373                 send_tcppacket(n->nexthop->connection, origpkt);
 374
 375                 return;
 376         }
 377
 378         if(n->options & OPTION_PMTU_DISCOVERY && inpkt->len > n->minmtu && (inpkt->data[12] | inpkt->data[13])) {
 379                 ifdebug(TRAFFIC) logger(LOG_INFO,
 380                                 "Packet for %s (%s) larger than minimum MTU, forwarding via %s",
 381                                 n->name, n->hostname, n != n->nexthop ? n->nexthop->name : "TCP");
 382
 383                 if(n != n->nexthop)
 384                         send_packet(n->nexthop, origpkt);
 385                 else
 386                         send_tcppacket(n->nexthop->connection, origpkt);
 387
 388                 return;
 389         }
 390
 391         origlen = inpkt->len;
 392         origpriority = inpkt->priority;
 393
 394         /* Compress the packet */
 395
 396         if(n->outcompression) {
 397                 outpkt = pkt[nextpkt++];
 398
 399                 if((outpkt->len = compress_packet(outpkt->data, inpkt->data, inpkt->len, n->outcompression)) < 0) {
 400                         ifdebug(TRAFFIC) logger(LOG_ERR, "Error while compressing packet to %s (%s)",
 401                                    n->name, n->hostname);
 402                         return;
 403                 }
 404
 405                 inpkt = outpkt;
 406         }
 407
 408         /* Add sequence number */
 409
 410         inpkt->seqno = htonl(++(n->sent_seqno));
 411         inpkt->len += sizeof(inpkt->seqno);
 412
 413         /* Encrypt the packet */
 414
 415         if(n->outcipher) {
 416                 outpkt = pkt[nextpkt++];
 417
 418                 if(!EVP_EncryptInit_ex(&n->outctx, NULL, NULL, NULL, NULL)
 419                                 || !EVP_EncryptUpdate(&n->outctx, (unsigned char *) &outpkt->seqno, &outlen,
 420                                         (unsigned char *) &inpkt->seqno, inpkt->len)
 421                                 || !EVP_EncryptFinal_ex(&n->outctx, (unsigned char *) &outpkt->seqno + outlen, &outpad)) {
 422                         ifdebug(TRAFFIC) logger(LOG_ERR, "Error while encrypting packet to %s (%s): %s",
 423                                                 n->name, n->hostname, ERR_error_string(ERR_get_error(), NULL));
 424                         goto end;
 425                 }
 426
 427                 outpkt->len = outlen + outpad;
 428                 inpkt = outpkt;
 429         }
 430
 431         /* Add the message authentication code */
 432
 433         if(n->outdigest && n->outmaclength) {
 434                 HMAC(n->outdigest, n->outkey, n->outkeylength, (unsigned char *) &inpkt->seqno,
 435                          inpkt->len, (unsigned char *) &inpkt->seqno + inpkt->len, NULL);
 436                 inpkt->len += n->outmaclength;
 437         }
 438
 439         /* Determine which socket we have to use */
 440
 441         for(sock = 0; sock < listen_sockets; sock++)
 442                 if(n->address.sa.sa_family == listen_socket[sock].sa.sa.sa_family)
 443                         break;
 444
 445         if(sock >= listen_sockets)
 446                 sock = 0;                               /* If none is available, just use the first and hope for the best. */
 447
 448         /* Send the packet */
 449
 450 #if defined(SOL_IP) && defined(IP_TOS)
 451         if(priorityinheritance && origpriority != priority
 452            && listen_socket[sock].sa.sa.sa_family == AF_INET) {
 453                 priority = origpriority;
 454                 ifdebug(TRAFFIC) logger(LOG_DEBUG, "Setting outgoing packet priority to %d", priority);
 455                 if(setsockopt(listen_socket[sock].udp, SOL_IP, IP_TOS, &priority, sizeof(priority)))    /* SO_PRIORITY doesn't seem to work */
 456                         logger(LOG_ERR, "System call `%s' failed: %s", "setsockopt", strerror(errno));
 457         }
 458 #endif
 459
 460         if((sendto(listen_socket[sock].udp, (char *) &inpkt->seqno, inpkt->len, 0, &(n->address.sa), SALEN(n->address.sa))) < 0) {
 461                 if(sockerrno == EMSGSIZE) {
 462                         if(n->maxmtu >= origlen)
 463                                 n->maxmtu = origlen - 1;
 464                         if(n->mtu >= origlen)
 465                                 n->mtu = origlen - 1;
 466                 } else
 467                         logger(LOG_ERR, "Error sending packet to %s (%s): %s", n->name, n->hostname, sockstrerror(sockerrno));
 468         }
 469
 470 end:
 471         origpkt->len = origlen;
 472 }
 473
 474 /*
 475   send a packet to the given vpn ip.
 476 */
 477 void send_packet(const node_t *n, vpn_packet_t *packet) {
 478         node_t *via;
 479
 480         if(n == myself) {
 481                 if(overwrite_mac)
 482                          memcpy(packet->data, mymac.x, ETH_ALEN);
 483                 write_packet(packet);
 484                 return;
 485         }
 486
 487         ifdebug(TRAFFIC) logger(LOG_ERR, "Sending packet of %d bytes to %s (%s)",
 488                            packet->len, n->name, n->hostname);
 489
 490         if(!n->status.reachable) {
 491                 ifdebug(TRAFFIC) logger(LOG_INFO, "Node %s (%s) is not reachable",
 492                                    n->name, n->hostname);
 493                 return;
 494         }
 495
 496         via = (packet->priority == -1 || n->via == myself) ? n->nexthop : n->via;
 497
 498         if(via != n)
 499                 ifdebug(TRAFFIC) logger(LOG_INFO, "Sending packet to %s via %s (%s)",
 500                            n->name, via->name, n->via->hostname);
 501
 502         if(packet->priority == -1 || ((myself->options | via->options) & OPTION_TCPONLY)) {
 503                 if(!send_tcppacket(via->connection, packet))
 504                         terminate_connection(via->connection, true);
 505         } else
 506                 send_udppacket(via, packet);
 507 }
 508
 509 /* Broadcast a packet using the minimum spanning tree */
 510
 511 void broadcast_packet(const node_t *from, vpn_packet_t *packet) {
 512         avl_node_t *node;
 513         connection_t *c;
 514
 515         ifdebug(TRAFFIC) logger(LOG_INFO, "Broadcasting packet of %d bytes from %s (%s)",
 516                            packet->len, from->name, from->hostname);
 517
 518         if(from != myself) {
 519                 send_packet(myself, packet);
 520
 521                 // In TunnelServer mode, do not forward broadcast packets.
 522                 // The MST might not be valid and create loops.
 523                 if(tunnelserver)
 524                         return;
 525         }
 526
 527         for(node = connection_tree->head; node; node = node->next) {
 528                 c = node->data;
 529
 530                 if(c->status.active && c->status.mst && c != from->nexthop->connection)
 531                         send_packet(c->node, packet);
 532         }
 533 }
 534
 535 static node_t *try_harder(const sockaddr_t *from, const vpn_packet_t *pkt) {
 536         avl_node_t *node;
 537         edge_t *e;
 538         node_t *n = NULL;
 539         static time_t last_hard_try = 0;
 540
 541         for(node = edge_weight_tree->head; node; node = node->next) {
 542                 e = node->data;
 543
 544                 if(sockaddrcmp_noport(from, &e->address)) {
 545                         if(last_hard_try == now)
 546                                 continue;
 547                         last_hard_try = now;
 548                 }
 549
 550                 if(!n)
 551                         n = e->to;
 552
 553                 if(!try_mac(e->to, pkt))
 554                         continue;
 555
 556                 n = e->to;
 557                 break;
 558         }
 559
 560         return n;
 561 }
 562
 563 void handle_incoming_vpn_data(int sock) {
 564         vpn_packet_t pkt;
 565         char *hostname;
 566         sockaddr_t from;
 567         socklen_t fromlen = sizeof(from);
 568         node_t *n;
 569
 570         pkt.len = recvfrom(sock, (char *) &pkt.seqno, MAXSIZE, 0, &from.sa, &fromlen);
 571
 572         if(pkt.len < 0) {
 573                 if(sockerrno != EAGAIN && sockerrno != EINTR)
 574                         logger(LOG_ERR, "Receiving packet failed: %s", sockstrerror(sockerrno));
 575                 return;
 576         }
 577
 578         sockaddrunmap(&from);           /* Some braindead IPv6 implementations do stupid things. */
 579
 580         n = lookup_node_udp(&from);
 581
 582         if(!n) {
 583                 n = try_harder(&from, &pkt);
 584                 if(n)
 585                         update_node_udp(n, &from);
 586                 else ifdebug(PROTOCOL) {
 587                         hostname = sockaddr2hostname(&from);
 588                         logger(LOG_WARNING, "Received UDP packet from unknown source %s", hostname);
 589                         free(hostname);
 590                         return;
 591                 }
 592                 else
 593                         return;
 594         }
 595
 596         receive_udppacket(n, &pkt);
 597 }