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 1.1.2.26 2003/03/28 13:41:49 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 EVP_CIPHER_CTX packet_ctx;
  84
  85 #define MAX_SEQNO 1073741824
  86
  87 /* VPN packet I/O */
  88
  89 void receive_udppacket(node_t *n, vpn_packet_t *inpkt)
  90 {
  91         vpn_packet_t pkt1, pkt2;
  92         vpn_packet_t *pkt[] = { &pkt1, &pkt2, &pkt1, &pkt2 };
  93         int nextpkt = 0;
  94         vpn_packet_t *outpkt = pkt[0];
  95         int outlen, outpad;
  96         long int complen = MTU + 12;
  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_ex(&packet_ctx, myself->cipher, NULL, myself->key,
 122                                                 myself->key + myself->cipher->key_len);
 123                 EVP_DecryptUpdate(&packet_ctx, (char *) &outpkt->seqno, &outlen,
 124                                                   (char *) &inpkt->seqno, inpkt->len);
 125                 EVP_DecryptFinal_ex(&packet_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         vpn_packet_t *copy;
 200         static int priority = 0;
 201         int origpriority;
 202         int sock;
 203
 204         cp();
 205
 206         /* Make sure we have a valid key */
 207
 208         if(!n->status.validkey) {
 209                 if(debug_lvl >= DEBUG_TRAFFIC)
 210                         syslog(LOG_INFO,
 211                                    _("No valid key known yet for %s (%s), queueing packet"),
 212                                    n->name, n->hostname);
 213
 214                 /* Since packet is on the stack of handle_tap_input(), we have to make a copy of it first. */
 215
 216                 copy = xmalloc(sizeof(vpn_packet_t));
 217                 memcpy(copy, inpkt, sizeof(vpn_packet_t));
 218
 219                 list_insert_tail(n->queue, copy);
 220
 221                 if(n->queue->count > MAXQUEUELENGTH)
 222                         list_delete_head(n->queue);
 223
 224                 if(!n->status.waitingforkey)
 225                         send_req_key(n->nexthop->connection, myself, n);
 226
 227                 n->status.waitingforkey = 1;
 228
 229                 return;
 230         }
 231
 232         origlen = inpkt->len;
 233         origpriority = inpkt->priority;
 234
 235         /* Compress the packet */
 236
 237         if(n->compression) {
 238                 outpkt = pkt[nextpkt++];
 239
 240                 if(compress2
 241                    (outpkt->data, &complen, inpkt->data, inpkt->len,
 242                         n->compression) != Z_OK) {
 243                         syslog(LOG_ERR, _("Error while compressing packet to %s (%s)"),
 244                                    n->name, n->hostname);
 245                         return;
 246                 }
 247
 248                 outpkt->len = complen;
 249                 inpkt = outpkt;
 250         }
 251
 252         /* Add sequence number */
 253
 254         inpkt->seqno = htonl(++(n->sent_seqno));
 255         inpkt->len += sizeof(inpkt->seqno);
 256
 257         /* Encrypt the packet */
 258
 259         if(n->cipher) {
 260                 outpkt = pkt[nextpkt++];
 261
 262                 EVP_EncryptInit_ex(&packet_ctx, n->cipher, NULL, n->key, n->key + n->cipher->key_len);
 263                 EVP_EncryptUpdate(&packet_ctx, (char *) &outpkt->seqno, &outlen,
 264                                                   (char *) &inpkt->seqno, inpkt->len);
 265                 EVP_EncryptFinal_ex(&packet_ctx, (char *) &outpkt->seqno + outlen, &outpad);
 266
 267                 outpkt->len = outlen + outpad;
 268                 inpkt = outpkt;
 269         }
 270
 271         /* Add the message authentication code */
 272
 273         if(n->digest && n->maclength) {
 274                 HMAC(n->digest, n->key, n->keylength, (char *) &inpkt->seqno,
 275                          inpkt->len, (char *) &inpkt->seqno + inpkt->len, &outlen);
 276                 inpkt->len += n->maclength;
 277         }
 278
 279         /* Determine which socket we have to use */
 280
 281         for(sock = 0; sock < listen_sockets; sock++)
 282                 if(n->address.sa.sa_family == listen_socket[sock].sa.sa.sa_family)
 283                         break;
 284
 285         if(sock >= listen_sockets)
 286                 sock = 0;                               /* If none is available, just use the first and hope for the best. */
 287
 288         /* Send the packet */
 289
 290 #if defined(SOL_IP) && defined(IP_TOS)
 291         if(priorityinheritance && origpriority != priority
 292            && listen_socket[sock].sa.sa.sa_family == AF_INET) {
 293                 priority = origpriority;
 294                 if(debug_lvl >= DEBUG_TRAFFIC)
 295                         syslog(LOG_DEBUG, _("Setting outgoing packet priority to %d"),
 296                                    priority);
 297                 if(setsockopt(listen_socket[sock].udp, SOL_IP, IP_TOS, &priority, sizeof(priority)))    /* SO_PRIORITY doesn't seem to work */
 298                         syslog(LOG_ERR, _("System call `%s' failed: %s"), "setsockopt",
 299                                    strerror(errno));
 300         }
 301 #endif
 302
 303         if((sendto(listen_socket[sock].udp, (char *) &inpkt->seqno, inpkt->len, 0, &(n->address.sa), SALEN(n->address.sa))) < 0) {
 304                 syslog(LOG_ERR, _("Error sending packet to %s (%s): %s"), n->name,
 305                            n->hostname, strerror(errno));
 306                 return;
 307         }
 308
 309         inpkt->len = origlen;
 310 }
 311
 312 /*
 313   send a packet to the given vpn ip.
 314 */
 315 void send_packet(node_t *n, vpn_packet_t *packet)
 316 {
 317         node_t *via;
 318
 319         cp();
 320
 321         if(debug_lvl >= DEBUG_TRAFFIC)
 322                 syslog(LOG_ERR, _("Sending packet of %d bytes to %s (%s)"),
 323                            packet->len, n->name, n->hostname);
 324
 325         if(n == myself) {
 326                 if(debug_lvl >= DEBUG_TRAFFIC)
 327                         syslog(LOG_NOTICE, _("Packet is looping back to us!"));
 328
 329                 return;
 330         }
 331
 332         if(!n->status.reachable) {
 333                 if(debug_lvl >= DEBUG_TRAFFIC)
 334                         syslog(LOG_INFO, _("Node %s (%s) is not reachable"),
 335                                    n->name, n->hostname);
 336
 337                 return;
 338         }
 339
 340         via = (n->via == myself) ? n->nexthop : n->via;
 341
 342         if(via != n && debug_lvl >= DEBUG_TRAFFIC)
 343                 syslog(LOG_ERR, _("Sending packet to %s via %s (%s)"),
 344                            n->name, via->name, n->via->hostname);
 345
 346         if((myself->options | via->options) & OPTION_TCPONLY) {
 347                 if(send_tcppacket(via->connection, packet))
 348                         terminate_connection(via->connection, 1);
 349         } else
 350                 send_udppacket(via, packet);
 351 }
 352
 353 /* Broadcast a packet using the minimum spanning tree */
 354
 355 void broadcast_packet(node_t *from, vpn_packet_t *packet)
 356 {
 357         avl_node_t *node;
 358         connection_t *c;
 359
 360         cp();
 361
 362         if(debug_lvl >= DEBUG_TRAFFIC)
 363                 syslog(LOG_INFO, _("Broadcasting packet of %d bytes from %s (%s)"),
 364                            packet->len, from->name, from->hostname);
 365
 366         for(node = connection_tree->head; node; node = node->next) {
 367                 c = (connection_t *) node->data;
 368
 369                 if(c->status.active && c->status.mst && c != from->nexthop->connection)
 370                         send_packet(c->node, packet);
 371         }
 372 }
 373
 374 void flush_queue(node_t *n)
 375 {
 376         list_node_t *node, *next;
 377
 378         cp();
 379
 380         if(debug_lvl >= DEBUG_TRAFFIC)
 381                 syslog(LOG_INFO, _("Flushing queue for %s (%s)"), n->name, n->hostname);
 382
 383         for(node = n->queue->head; node; node = next) {
 384                 next = node->next;
 385                 send_udppacket(n, (vpn_packet_t *) node->data);
 386                 list_delete_node(n->queue, node);
 387         }
 388 }
 389
 390 void handle_incoming_vpn_data(int sock)
 391 {
 392         vpn_packet_t pkt;
 393         int x, l = sizeof(x);
 394         char *hostname;
 395         sockaddr_t from;
 396         socklen_t fromlen = sizeof(from);
 397         node_t *n;
 398
 399         cp();
 400
 401         if(getsockopt(sock, SOL_SOCKET, SO_ERROR, &x, &l) < 0) {
 402                 syslog(LOG_ERR, _("This is a bug: %s:%d: %d:%s"),
 403                            __FILE__, __LINE__, sock, strerror(errno));
 404                 cp_trace();
 405                 exit(1);
 406         }
 407
 408         if(x) {
 409                 syslog(LOG_ERR, _("Incoming data socket error: %s"), strerror(x));
 410                 return;
 411         }
 412
 413         pkt.len = recvfrom(sock, (char *) &pkt.seqno, MAXSIZE, 0, &from.sa, &fromlen);
 414
 415         if(pkt.len <= 0) {
 416                 syslog(LOG_ERR, _("Receiving packet failed: %s"), strerror(errno));
 417                 return;
 418         }
 419
 420         sockaddrunmap(&from);           /* Some braindead IPv6 implementations do stupid things. */
 421
 422         n = lookup_node_udp(&from);
 423
 424         if(!n) {
 425                 hostname = sockaddr2hostname(&from);
 426                 syslog(LOG_WARNING, _("Received UDP packet from unknown source %s"),
 427                            hostname);
 428                 free(hostname);
 429                 return;
 430         }
 431
 432         if(n->connection)
 433                 n->connection->last_ping_time = now;
 434
 435         receive_udppacket(n, &pkt);
 436 }