tinc-vpn.org Git - tinc/blob - src/net_packet.c

   1 /*
   2     net_packet.c -- Handles in- and outgoing VPN packets
   3     Copyright (C) 1998-2002 Ivo Timmermans <ivo@o2w.nl>,
   4                   2000-2002 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 1.1.2.24 2002/09/15 14:55:53 guus Exp $
  21 */
  22
  23 #include "config.h"
  24
  25 #include <errno.h>
  26 #include <fcntl.h>
  27 #include <netdb.h>
  28 #include <netinet/in.h>
  29 #include <stdio.h>
  30 #include <stdlib.h>
  31 #include <string.h>
  32 #include <signal.h>
  33 #include <sys/time.h>
  34 #include <sys/types.h>
  35 #include <syslog.h>
  36 #include <unistd.h>
  37 #include <sys/ioctl.h>
  38 /* SunOS really wants sys/socket.h BEFORE net/if.h,
  39    and FreeBSD wants these lines below the rest. */
  40 #include <arpa/inet.h>
  41 #include <sys/socket.h>
  42 #include <net/if.h>
  43 #ifdef HAVE_NETINET_IN_SYSTM_H
  44 #include <netinet/in_systm.h>
  45 #endif
  46 #ifdef HAVE_NETINET_IP_H
  47 #include <netinet/ip.h>
  48 #endif
  49 #ifdef HAVE_NETINET_TCP_H
  50 #include <netinet/tcp.h>
  51 #endif
  52
  53 #include <openssl/rand.h>
  54 #include <openssl/evp.h>
  55 #include <openssl/pem.h>
  56 #include <openssl/hmac.h>
  57
  58 #include <zlib.h>
  59
  60 #include <utils.h>
  61 #include <xalloc.h>
  62 #include <avl_tree.h>
  63 #include <list.h>
  64
  65 #include "conf.h"
  66 #include "connection.h"
  67 #include "meta.h"
  68 #include "net.h"
  69 #include "netutl.h"
  70 #include "process.h"
  71 #include "protocol.h"
  72 #include "subnet.h"
  73 #include "graph.h"
  74 #include "process.h"
  75 #include "route.h"
  76 #include "device.h"
  77 #include "event.h"
  78
  79 #include "system.h"
  80
  81 int keylifetime = 0;
  82 int keyexpires = 0;
  83
  84 #define MAX_SEQNO 1073741824
  85
  86 /* VPN packet I/O */
  87
  88 void receive_udppacket(node_t *n, vpn_packet_t *inpkt)
  89 {
  90         vpn_packet_t pkt1, pkt2;
  91         vpn_packet_t *pkt[] = { &pkt1, &pkt2, &pkt1, &pkt2 };
  92         int nextpkt = 0;
  93         vpn_packet_t *outpkt = pkt[0];
  94         int outlen, outpad;
  95         long int complen = MTU + 12;
  96         EVP_CIPHER_CTX ctx;
  97         char hmac[EVP_MAX_MD_SIZE];
  98
  99         cp();
 100
 101         /* Check the message authentication code */
 102
 103         if(myself->digest && myself->maclength) {
 104                 inpkt->len -= myself->maclength;
 105                 HMAC(myself->digest, myself->key, myself->keylength,
 106                          (char *) &inpkt->seqno, inpkt->len, hmac, NULL);
 107
 108                 if(memcmp(hmac, (char *) &inpkt->seqno + inpkt->len, myself->maclength)) {
 109                         if(debug_lvl >= DEBUG_TRAFFIC)
 110                                 syslog(LOG_DEBUG, _("Got unauthenticated packet from %s (%s)"),
 111                                            n->name, n->hostname);
 112                         return;
 113                 }
 114         }
 115
 116         /* Decrypt the packet */
 117
 118         if(myself->cipher) {
 119                 outpkt = pkt[nextpkt++];
 120
 121                 EVP_DecryptInit(&ctx, myself->cipher, myself->key,
 122                                                 myself->key + myself->cipher->key_len);
 123                 EVP_DecryptUpdate(&ctx, (char *) &outpkt->seqno, &outlen,
 124                                                   (char *) &inpkt->seqno, inpkt->len);
 125                 EVP_DecryptFinal(&ctx, (char *) &outpkt->seqno + outlen, &outpad);
 126
 127                 outpkt->len = outlen + outpad;
 128                 inpkt = outpkt;
 129         }
 130
 131         /* Check the sequence number */
 132
 133         inpkt->len -= sizeof(inpkt->seqno);
 134         inpkt->seqno = ntohl(inpkt->seqno);
 135
 136         if(inpkt->seqno <= n->received_seqno) {
 137                 if(debug_lvl >= DEBUG_TRAFFIC)
 138                         syslog(LOG_DEBUG,
 139                                    _("Got late or replayed packet from %s (%s), seqno %d"),
 140                                    n->name, n->hostname, inpkt->seqno);
 141                 return;
 142         }
 143
 144         n->received_seqno = inpkt->seqno;
 145
 146         if(n->received_seqno > MAX_SEQNO)
 147                 keyexpires = 0;
 148
 149         /* Decompress the packet */
 150
 151         if(myself->compression) {
 152                 outpkt = pkt[nextpkt++];
 153
 154                 if(uncompress(outpkt->data, &complen, inpkt->data, inpkt->len) != Z_OK) {
 155                         syslog(LOG_ERR, _("Error while uncompressing packet from %s (%s)"),
 156                                    n->name, n->hostname);
 157                         return;
 158                 }
 159
 160                 outpkt->len = complen;
 161                 inpkt = outpkt;
 162         }
 163
 164         receive_packet(n, inpkt);
 165 }
 166
 167 void receive_tcppacket(connection_t *c, char *buffer, int len)
 168 {
 169         vpn_packet_t outpkt;
 170
 171         cp();
 172
 173         outpkt.len = len;
 174         memcpy(outpkt.data, buffer, len);
 175
 176         receive_packet(c->node, &outpkt);
 177 }
 178
 179 void receive_packet(node_t *n, vpn_packet_t *packet)
 180 {
 181         cp();
 182
 183         if(debug_lvl >= DEBUG_TRAFFIC)
 184                 syslog(LOG_DEBUG, _("Received packet of %d bytes from %s (%s)"),
 185                            packet->len, n->name, n->hostname);
 186
 187         route_incoming(n, packet);
 188 }
 189
 190 void send_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;
 196         int origlen;
 197         int outlen, outpad;
 198         long int complen = MTU + 12;
 199         EVP_CIPHER_CTX ctx;
 200         vpn_packet_t *copy;
 201         static int priority = 0;
 202         int origpriority;
 203         int sock;
 204
 205         cp();
 206
 207         /* Make sure we have a valid key */
 208
 209         if(!n->status.validkey) {
 210                 if(debug_lvl >= DEBUG_TRAFFIC)
 211                         syslog(LOG_INFO,
 212                                    _("No valid key known yet for %s (%s), queueing packet"),
 213                                    n->name, n->hostname);
 214
 215                 /* Since packet is on the stack of handle_tap_input(), we have to make a copy of it first. */
 216
 217                 copy = xmalloc(sizeof(vpn_packet_t));
 218                 memcpy(copy, inpkt, sizeof(vpn_packet_t));
 219
 220                 list_insert_tail(n->queue, copy);
 221
 222                 if(n->queue->count > MAXQUEUELENGTH)
 223                         list_delete_head(n->queue);
 224
 225                 if(!n->status.waitingforkey)
 226                         send_req_key(n->nexthop->connection, myself, n);
 227
 228                 n->status.waitingforkey = 1;
 229
 230                 return;
 231         }
 232
 233         origlen = inpkt->len;
 234         origpriority = inpkt->priority;
 235
 236         /* Compress the packet */
 237
 238         if(n->compression) {
 239                 outpkt = pkt[nextpkt++];
 240
 241                 if(compress2
 242                    (outpkt->data, &complen, inpkt->data, inpkt->len,
 243                         n->compression) != Z_OK) {
 244                         syslog(LOG_ERR, _("Error while compressing packet to %s (%s)"),
 245                                    n->name, n->hostname);
 246                         return;
 247                 }
 248
 249                 outpkt->len = complen;
 250                 inpkt = outpkt;
 251         }
 252
 253         /* Add sequence number */
 254
 255         inpkt->seqno = htonl(++(n->sent_seqno));
 256         inpkt->len += sizeof(inpkt->seqno);
 257
 258         /* Encrypt the packet */
 259
 260         if(n->cipher) {
 261                 outpkt = pkt[nextpkt++];
 262
 263                 EVP_EncryptInit(&ctx, n->cipher, n->key, n->key + n->cipher->key_len);
 264                 EVP_EncryptUpdate(&ctx, (char *) &outpkt->seqno, &outlen,
 265                                                   (char *) &inpkt->seqno, inpkt->len);
 266                 EVP_EncryptFinal(&ctx, (char *) &outpkt->seqno + outlen, &outpad);
 267
 268                 outpkt->len = outlen + outpad;
 269                 inpkt = outpkt;
 270         }
 271
 272         /* Add the message authentication code */
 273
 274         if(n->digest && n->maclength) {
 275                 HMAC(n->digest, n->key, n->keylength, (char *) &inpkt->seqno,
 276                          inpkt->len, (char *) &inpkt->seqno + inpkt->len, &outlen);
 277                 inpkt->len += n->maclength;
 278         }
 279
 280         /* Determine which socket we have to use */
 281
 282         for(sock = 0; sock < listen_sockets; sock++)
 283                 if(n->address.sa.sa_family == listen_socket[sock].sa.sa.sa_family)
 284                         break;
 285
 286         if(sock >= listen_sockets)
 287                 sock = 0;                               /* If none is available, just use the first and hope for the best. */
 288
 289         /* Send the packet */
 290
 291 #if defined(SOL_IP) && defined(IP_TOS)
 292         if(priorityinheritance && origpriority != priority
 293            && listen_socket[sock].sa.sa.sa_family == AF_INET) {
 294                 priority = origpriority;
 295                 if(debug_lvl >= DEBUG_TRAFFIC)
 296                         syslog(LOG_DEBUG, _("Setting outgoing packet priority to %d"),
 297                                    priority);
 298                 if(setsockopt(sock, SOL_IP, IP_TOS, &priority, sizeof(priority)))       /* SO_PRIORITY doesn't seem to work */
 299                         syslog(LOG_ERR, _("System call `%s' failed: %s"), "setsockopt",
 300                                    strerror(errno));
 301         }
 302 #endif
 303
 304         if((sendto(listen_socket[sock].udp, (char *) &inpkt->seqno, inpkt->len, 0, &(n->address.sa), SALEN(n->address.sa))) < 0) {
 305                 syslog(LOG_ERR, _("Error sending packet to %s (%s): %s"), n->name,
 306                            n->hostname, strerror(errno));
 307                 return;
 308         }
 309
 310         inpkt->len = origlen;
 311 }
 312
 313 /*
 314   send a packet to the given vpn ip.
 315 */
 316 void send_packet(node_t *n, vpn_packet_t *packet)
 317 {
 318         node_t *via;
 319
 320         cp();
 321
 322         if(debug_lvl >= DEBUG_TRAFFIC)
 323                 syslog(LOG_ERR, _("Sending packet of %d bytes to %s (%s)"),
 324                            packet->len, n->name, n->hostname);
 325
 326         if(n == myself) {
 327                 if(debug_lvl >= DEBUG_TRAFFIC)
 328                         syslog(LOG_NOTICE, _("Packet is looping back to us!"));
 329
 330                 return;
 331         }
 332
 333         if(!n->status.reachable) {
 334                 if(debug_lvl >= DEBUG_TRAFFIC)
 335                         syslog(LOG_INFO, _("Node %s (%s) is not reachable"),
 336                                    n->name, n->hostname);
 337
 338                 return;
 339         }
 340
 341         via = (n->via == myself) ? n->nexthop : n->via;
 342
 343         if(via != n && debug_lvl >= DEBUG_TRAFFIC)
 344                 syslog(LOG_ERR, _("Sending packet to %s via %s (%s)"),
 345                            n->name, via->name, n->via->hostname);
 346
 347         if((myself->options | via->options) & OPTION_TCPONLY) {
 348                 if(send_tcppacket(via->connection, packet))
 349                         terminate_connection(via->connection, 1);
 350         } else
 351                 send_udppacket(via, packet);
 352 }
 353
 354 /* Broadcast a packet using the minimum spanning tree */
 355
 356 void broadcast_packet(node_t *from, vpn_packet_t *packet)
 357 {
 358         avl_node_t *node;
 359         connection_t *c;
 360
 361         cp();
 362
 363         if(debug_lvl >= DEBUG_TRAFFIC)
 364                 syslog(LOG_INFO, _("Broadcasting packet of %d bytes from %s (%s)"),
 365                            packet->len, from->name, from->hostname);
 366
 367         for(node = connection_tree->head; node; node = node->next) {
 368                 c = (connection_t *) node->data;
 369
 370                 if(c->status.active && c->status.mst && c != from->nexthop->connection)
 371                         send_packet(c->node, packet);
 372         }
 373 }
 374
 375 void flush_queue(node_t *n)
 376 {
 377         list_node_t *node, *next;
 378
 379         cp();
 380
 381         if(debug_lvl >= DEBUG_TRAFFIC)
 382                 syslog(LOG_INFO, _("Flushing queue for %s (%s)"), n->name, n->hostname);
 383
 384         for(node = n->queue->head; node; node = next) {
 385                 next = node->next;
 386                 send_udppacket(n, (vpn_packet_t *) node->data);
 387                 list_delete_node(n->queue, node);
 388         }
 389 }
 390
 391 void handle_incoming_vpn_data(int sock)
 392 {
 393         vpn_packet_t pkt;
 394         int x, l = sizeof(x);
 395         char *hostname;
 396         sockaddr_t from;
 397         socklen_t fromlen = sizeof(from);
 398         node_t *n;
 399
 400         cp();
 401
 402         if(getsockopt(sock, SOL_SOCKET, SO_ERROR, &x, &l) < 0) {
 403                 syslog(LOG_ERR, _("This is a bug: %s:%d: %d:%s"),
 404                            __FILE__, __LINE__, sock, strerror(errno));
 405                 cp_trace();
 406                 exit(1);
 407         }
 408
 409         if(x) {
 410                 syslog(LOG_ERR, _("Incoming data socket error: %s"), strerror(x));
 411                 return;
 412         }
 413
 414         pkt.len = recvfrom(sock, (char *) &pkt.seqno, MAXSIZE, 0, &from.sa, &fromlen);
 415
 416         if(pkt.len <= 0) {
 417                 syslog(LOG_ERR, _("Receiving packet failed: %s"), strerror(errno));
 418                 return;
 419         }
 420
 421         sockaddrunmap(&from);           /* Some braindead IPv6 implementations do stupid things. */
 422
 423         n = lookup_node_udp(&from);
 424
 425         if(!n) {
 426                 hostname = sockaddr2hostname(&from);
 427                 syslog(LOG_WARNING, _("Received UDP packet from unknown source %s"),
 428                            hostname);
 429                 free(hostname);
 430                 return;
 431         }
 432
 433         if(n->connection)
 434                 n->connection->last_ping_time = now;
 435
 436         receive_udppacket(n, &pkt);
 437 }