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 1.1.2.27 2003/04/18 21:18:36 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         int i;
  99
 100         cp();
 101
 102         /* Check the message authentication code */
 103
 104         if(myself->digest && myself->maclength) {
 105                 inpkt->len -= myself->maclength;
 106                 HMAC(myself->digest, myself->key, myself->keylength,
 107                          (char *) &inpkt->seqno, inpkt->len, hmac, NULL);
 108
 109                 if(memcmp(hmac, (char *) &inpkt->seqno + inpkt->len, myself->maclength)) {
 110                         if(debug_lvl >= DEBUG_TRAFFIC)
 111                                 syslog(LOG_DEBUG, _("Got unauthenticated packet from %s (%s)"),
 112                                            n->name, n->hostname);
 113                         return;
 114                 }
 115         }
 116
 117         /* Decrypt the packet */
 118
 119         if(myself->cipher) {
 120                 outpkt = pkt[nextpkt++];
 121
 122                 EVP_DecryptInit_ex(&packet_ctx, myself->cipher, NULL, myself->key,
 123                                                 myself->key + myself->cipher->key_len);
 124                 EVP_DecryptUpdate(&packet_ctx, (char *) &outpkt->seqno, &outlen,
 125                                                   (char *) &inpkt->seqno, inpkt->len);
 126                 EVP_DecryptFinal_ex(&packet_ctx, (char *) &outpkt->seqno + outlen, &outpad);
 127
 128                 outpkt->len = outlen + outpad;
 129                 inpkt = outpkt;
 130         }
 131
 132         /* Check the sequence number */
 133
 134         inpkt->len -= sizeof(inpkt->seqno);
 135         inpkt->seqno = ntohl(inpkt->seqno);
 136
 137         if(inpkt->seqno != n->received_seqno + 1) {
 138                 if(inpkt->seqno >= n->received_seqno + sizeof(n->late) * 8) {
 139                         if(debug_lvl >= DEBUG_TRAFFIC)
 140                                 syslog(LOG_WARNING, _("Lost %d packets from %s (%s)"),
 141                                            inpkt->seqno - n->received_seqno - 1, n->name, n->hostname);
 142
 143                         memset(n->late, 0, sizeof(n->late));
 144                 } else if (inpkt->seqno <= n->received_seqno) {
 145                         if(inpkt->seqno <= n->received_seqno - sizeof(n->late) * 8 || !(n->late[(inpkt->seqno / 8) % sizeof(n->late)] & (1 << inpkt->seqno % 8))) {
 146                                 syslog(LOG_WARNING, _("Got late or replayed packet from %s (%s), seqno %d, last received %d"),
 147                                            n->name, n->hostname, inpkt->seqno, n->received_seqno, n->late[(inpkt->seqno / 8) % sizeof(n->late)]);
 148                         } else
 149                                 for(i = n->received_seqno + 1; i < inpkt->seqno; i++)
 150                                         n->late[(inpkt->seqno / 8) % sizeof(n->late)] |= 1 << i % 8;
 151                 }
 152         }
 153
 154         n->received_seqno = inpkt->seqno;
 155         n->late[(n->received_seqno / 8) % sizeof(n->late)] &= ~(1 << n->received_seqno % 8);
 156
 157         if(n->received_seqno > MAX_SEQNO)
 158                 keyexpires = 0;
 159
 160         /* Decompress the packet */
 161
 162         if(myself->compression) {
 163                 outpkt = pkt[nextpkt++];
 164
 165                 if(uncompress(outpkt->data, &complen, inpkt->data, inpkt->len) != Z_OK) {
 166                         syslog(LOG_ERR, _("Error while uncompressing packet from %s (%s)"),
 167                                    n->name, n->hostname);
 168                         return;
 169                 }
 170
 171                 outpkt->len = complen;
 172                 inpkt = outpkt;
 173         }
 174
 175         receive_packet(n, inpkt);
 176 }
 177
 178 void receive_tcppacket(connection_t *c, char *buffer, int len)
 179 {
 180         vpn_packet_t outpkt;
 181
 182         cp();
 183
 184         outpkt.len = len;
 185         memcpy(outpkt.data, buffer, len);
 186
 187         receive_packet(c->node, &outpkt);
 188 }
 189
 190 void receive_packet(node_t *n, vpn_packet_t *packet)
 191 {
 192         cp();
 193
 194         if(debug_lvl >= DEBUG_TRAFFIC)
 195                 syslog(LOG_DEBUG, _("Received packet of %d bytes from %s (%s)"),
 196                            packet->len, n->name, n->hostname);
 197
 198         route_incoming(n, packet);
 199 }
 200
 201 void send_udppacket(node_t *n, vpn_packet_t *inpkt)
 202 {
 203         vpn_packet_t pkt1, pkt2;
 204         vpn_packet_t *pkt[] = { &pkt1, &pkt2, &pkt1, &pkt2 };
 205         int nextpkt = 0;
 206         vpn_packet_t *outpkt;
 207         int origlen;
 208         int outlen, outpad;
 209         long int complen = MTU + 12;
 210         vpn_packet_t *copy;
 211         static int priority = 0;
 212         int origpriority;
 213         int sock;
 214
 215         cp();
 216
 217         /* Make sure we have a valid key */
 218
 219         if(!n->status.validkey) {
 220                 if(debug_lvl >= DEBUG_TRAFFIC)
 221                         syslog(LOG_INFO,
 222                                    _("No valid key known yet for %s (%s), queueing packet"),
 223                                    n->name, n->hostname);
 224
 225                 /* Since packet is on the stack of handle_tap_input(), we have to make a copy of it first. */
 226
 227                 copy = xmalloc(sizeof(vpn_packet_t));
 228                 memcpy(copy, inpkt, sizeof(vpn_packet_t));
 229
 230                 list_insert_tail(n->queue, copy);
 231
 232                 if(n->queue->count > MAXQUEUELENGTH)
 233                         list_delete_head(n->queue);
 234
 235                 if(!n->status.waitingforkey)
 236                         send_req_key(n->nexthop->connection, myself, n);
 237
 238                 n->status.waitingforkey = 1;
 239
 240                 return;
 241         }
 242
 243         origlen = inpkt->len;
 244         origpriority = inpkt->priority;
 245
 246         /* Compress the packet */
 247
 248         if(n->compression) {
 249                 outpkt = pkt[nextpkt++];
 250
 251                 if(compress2
 252                    (outpkt->data, &complen, inpkt->data, inpkt->len,
 253                         n->compression) != Z_OK) {
 254                         syslog(LOG_ERR, _("Error while compressing packet to %s (%s)"),
 255                                    n->name, n->hostname);
 256                         return;
 257                 }
 258
 259                 outpkt->len = complen;
 260                 inpkt = outpkt;
 261         }
 262
 263         /* Add sequence number */
 264
 265         inpkt->seqno = htonl(++(n->sent_seqno));
 266         inpkt->len += sizeof(inpkt->seqno);
 267
 268         /* Encrypt the packet */
 269
 270         if(n->cipher) {
 271                 outpkt = pkt[nextpkt++];
 272
 273                 EVP_EncryptInit_ex(&packet_ctx, n->cipher, NULL, n->key, n->key + n->cipher->key_len);
 274                 EVP_EncryptUpdate(&packet_ctx, (char *) &outpkt->seqno, &outlen,
 275                                                   (char *) &inpkt->seqno, inpkt->len);
 276                 EVP_EncryptFinal_ex(&packet_ctx, (char *) &outpkt->seqno + outlen, &outpad);
 277
 278                 outpkt->len = outlen + outpad;
 279                 inpkt = outpkt;
 280         }
 281
 282         /* Add the message authentication code */
 283
 284         if(n->digest && n->maclength) {
 285                 HMAC(n->digest, n->key, n->keylength, (char *) &inpkt->seqno,
 286                          inpkt->len, (char *) &inpkt->seqno + inpkt->len, &outlen);
 287                 inpkt->len += n->maclength;
 288         }
 289
 290         /* Determine which socket we have to use */
 291
 292         for(sock = 0; sock < listen_sockets; sock++)
 293                 if(n->address.sa.sa_family == listen_socket[sock].sa.sa.sa_family)
 294                         break;
 295
 296         if(sock >= listen_sockets)
 297                 sock = 0;                               /* If none is available, just use the first and hope for the best. */
 298
 299         /* Send the packet */
 300
 301 #if defined(SOL_IP) && defined(IP_TOS)
 302         if(priorityinheritance && origpriority != priority
 303            && listen_socket[sock].sa.sa.sa_family == AF_INET) {
 304                 priority = origpriority;
 305                 if(debug_lvl >= DEBUG_TRAFFIC)
 306                         syslog(LOG_DEBUG, _("Setting outgoing packet priority to %d"),
 307                                    priority);
 308                 if(setsockopt(listen_socket[sock].udp, SOL_IP, IP_TOS, &priority, sizeof(priority)))    /* SO_PRIORITY doesn't seem to work */
 309                         syslog(LOG_ERR, _("System call `%s' failed: %s"), "setsockopt",
 310                                    strerror(errno));
 311         }
 312 #endif
 313
 314         if((sendto(listen_socket[sock].udp, (char *) &inpkt->seqno, inpkt->len, 0, &(n->address.sa), SALEN(n->address.sa))) < 0) {
 315                 syslog(LOG_ERR, _("Error sending packet to %s (%s): %s"), n->name,
 316                            n->hostname, strerror(errno));
 317                 return;
 318         }
 319
 320         inpkt->len = origlen;
 321 }
 322
 323 /*
 324   send a packet to the given vpn ip.
 325 */
 326 void send_packet(node_t *n, vpn_packet_t *packet)
 327 {
 328         node_t *via;
 329
 330         cp();
 331
 332         if(debug_lvl >= DEBUG_TRAFFIC)
 333                 syslog(LOG_ERR, _("Sending packet of %d bytes to %s (%s)"),
 334                            packet->len, n->name, n->hostname);
 335
 336         if(n == myself) {
 337                 if(debug_lvl >= DEBUG_TRAFFIC)
 338                         syslog(LOG_NOTICE, _("Packet is looping back to us!"));
 339
 340                 return;
 341         }
 342
 343         if(!n->status.reachable) {
 344                 if(debug_lvl >= DEBUG_TRAFFIC)
 345                         syslog(LOG_INFO, _("Node %s (%s) is not reachable"),
 346                                    n->name, n->hostname);
 347
 348                 return;
 349         }
 350
 351         via = (n->via == myself) ? n->nexthop : n->via;
 352
 353         if(via != n && debug_lvl >= DEBUG_TRAFFIC)
 354                 syslog(LOG_ERR, _("Sending packet to %s via %s (%s)"),
 355                            n->name, via->name, n->via->hostname);
 356
 357         if((myself->options | via->options) & OPTION_TCPONLY) {
 358                 if(send_tcppacket(via->connection, packet))
 359                         terminate_connection(via->connection, 1);
 360         } else
 361                 send_udppacket(via, packet);
 362 }
 363
 364 /* Broadcast a packet using the minimum spanning tree */
 365
 366 void broadcast_packet(node_t *from, vpn_packet_t *packet)
 367 {
 368         avl_node_t *node;
 369         connection_t *c;
 370
 371         cp();
 372
 373         if(debug_lvl >= DEBUG_TRAFFIC)
 374                 syslog(LOG_INFO, _("Broadcasting packet of %d bytes from %s (%s)"),
 375                            packet->len, from->name, from->hostname);
 376
 377         for(node = connection_tree->head; node; node = node->next) {
 378                 c = (connection_t *) node->data;
 379
 380                 if(c->status.active && c->status.mst && c != from->nexthop->connection)
 381                         send_packet(c->node, packet);
 382         }
 383 }
 384
 385 void flush_queue(node_t *n)
 386 {
 387         list_node_t *node, *next;
 388
 389         cp();
 390
 391         if(debug_lvl >= DEBUG_TRAFFIC)
 392                 syslog(LOG_INFO, _("Flushing queue for %s (%s)"), n->name, n->hostname);
 393
 394         for(node = n->queue->head; node; node = next) {
 395                 next = node->next;
 396                 send_udppacket(n, (vpn_packet_t *) node->data);
 397                 list_delete_node(n->queue, node);
 398         }
 399 }
 400
 401 void handle_incoming_vpn_data(int sock)
 402 {
 403         vpn_packet_t pkt;
 404         int x, l = sizeof(x);
 405         char *hostname;
 406         sockaddr_t from;
 407         socklen_t fromlen = sizeof(from);
 408         node_t *n;
 409
 410         cp();
 411
 412         if(getsockopt(sock, SOL_SOCKET, SO_ERROR, &x, &l) < 0) {
 413                 syslog(LOG_ERR, _("This is a bug: %s:%d: %d:%s"),
 414                            __FILE__, __LINE__, sock, strerror(errno));
 415                 cp_trace();
 416                 exit(1);
 417         }
 418
 419         if(x) {
 420                 syslog(LOG_ERR, _("Incoming data socket error: %s"), strerror(x));
 421                 return;
 422         }
 423
 424         pkt.len = recvfrom(sock, (char *) &pkt.seqno, MAXSIZE, 0, &from.sa, &fromlen);
 425
 426         if(pkt.len <= 0) {
 427                 syslog(LOG_ERR, _("Receiving packet failed: %s"), strerror(errno));
 428                 return;
 429         }
 430
 431         sockaddrunmap(&from);           /* Some braindead IPv6 implementations do stupid things. */
 432
 433         n = lookup_node_udp(&from);
 434
 435         if(!n) {
 436                 hostname = sockaddr2hostname(&from);
 437                 syslog(LOG_WARNING, _("Received UDP packet from unknown source %s"),
 438                            hostname);
 439                 free(hostname);
 440                 return;
 441         }
 442
 443         if(n->connection)
 444                 n->connection->last_ping_time = now;
 445
 446         receive_udppacket(n, &pkt);
 447 }