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