/* net_packet.c -- Handles in- and outgoing VPN packets Copyright (C) 1998-2005 Ivo Timmermans, 2000-2011 Guus Sliepen 2010 Timothy Redaelli 2010 Brandon Black This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. */ #include "system.h" #include #include #include #include #include #ifdef HAVE_ZLIB #include #endif #ifdef HAVE_LZO #include LZO1X_H #endif #include "avl_tree.h" #include "conf.h" #include "connection.h" #include "device.h" #include "ethernet.h" #include "event.h" #include "graph.h" #include "logger.h" #include "net.h" #include "netutl.h" #include "protocol.h" #include "process.h" #include "route.h" #include "utils.h" #include "xalloc.h" int keylifetime = 0; int keyexpires = 0; #ifdef HAVE_LZO static char lzo_wrkmem[LZO1X_999_MEM_COMPRESS > LZO1X_1_MEM_COMPRESS ? LZO1X_999_MEM_COMPRESS : LZO1X_1_MEM_COMPRESS]; #endif static void send_udppacket(node_t *, vpn_packet_t *); unsigned replaywin = 16; #define MAX_SEQNO 1073741824 // mtuprobes == 1..30: initial discovery, send bursts with 1 second interval // mtuprobes == 31: sleep pinginterval seconds // mtuprobes == 32: send 1 burst, sleep pingtimeout second // mtuprobes == 33: no response from other side, restart PMTU discovery process void send_mtu_probe(node_t *n) { vpn_packet_t packet; int len, i; int timeout = 1; n->mtuprobes++; n->mtuevent = NULL; if(!n->status.reachable || !n->status.validkey) { ifdebug(TRAFFIC) logger(LOG_INFO, "Trying to send MTU probe to unreachable or rekeying node %s (%s)", n->name, n->hostname); n->mtuprobes = 0; return; } if(n->mtuprobes > 32) { if(!n->minmtu) { n->mtuprobes = 31; timeout = pinginterval; goto end; } ifdebug(TRAFFIC) logger(LOG_INFO, "%s (%s) did not respond to UDP ping, restarting PMTU discovery", n->name, n->hostname); n->mtuprobes = 1; n->minmtu = 0; n->maxmtu = MTU; } if(n->mtuprobes >= 10 && n->mtuprobes < 32 && !n->minmtu) { ifdebug(TRAFFIC) logger(LOG_INFO, "No response to MTU probes from %s (%s)", n->name, n->hostname); n->mtuprobes = 31; } if(n->mtuprobes == 30 || (n->mtuprobes < 30 && n->minmtu >= n->maxmtu)) { if(n->minmtu > n->maxmtu) n->minmtu = n->maxmtu; else n->maxmtu = n->minmtu; n->mtu = n->minmtu; ifdebug(TRAFFIC) logger(LOG_INFO, "Fixing MTU of %s (%s) to %d after %d probes", n->name, n->hostname, n->mtu, n->mtuprobes); n->mtuprobes = 31; } if(n->mtuprobes == 31) { timeout = pinginterval; goto end; } else if(n->mtuprobes == 32) { timeout = pingtimeout; } for(i = 0; i < 3; i++) { if(n->maxmtu <= n->minmtu) len = n->maxmtu; else len = n->minmtu + 1 + rand() % (n->maxmtu - n->minmtu); if(len < 64) len = 64; memset(packet.data, 0, 14); RAND_pseudo_bytes(packet.data + 14, len - 14); packet.len = len; packet.priority = 0; ifdebug(TRAFFIC) logger(LOG_INFO, "Sending MTU probe length %d to %s (%s)", len, n->name, n->hostname); send_udppacket(n, &packet); } end: n->mtuevent = new_event(); n->mtuevent->handler = (event_handler_t)send_mtu_probe; n->mtuevent->data = n; n->mtuevent->time = now + timeout; event_add(n->mtuevent); } void mtu_probe_h(node_t *n, vpn_packet_t *packet, length_t len) { ifdebug(TRAFFIC) logger(LOG_INFO, "Got MTU probe length %d from %s (%s)", packet->len, n->name, n->hostname); if(!packet->data[0]) { packet->data[0] = 1; send_udppacket(n, packet); } else { if(n->mtuprobes > 30) { if(n->minmtu) n->mtuprobes = 30; else n->mtuprobes = 1; } if(len > n->maxmtu) len = n->maxmtu; if(n->minmtu < len) n->minmtu = len; } } static length_t compress_packet(uint8_t *dest, const uint8_t *source, length_t len, int level) { if(level == 0) { memcpy(dest, source, len); return len; } else if(level == 10) { #ifdef HAVE_LZO lzo_uint lzolen = MAXSIZE; lzo1x_1_compress(source, len, dest, &lzolen, lzo_wrkmem); return lzolen; #else return -1; #endif } else if(level < 10) { #ifdef HAVE_ZLIB unsigned long destlen = MAXSIZE; if(compress2(dest, &destlen, source, len, level) == Z_OK) return destlen; else #endif return -1; } else { #ifdef HAVE_LZO lzo_uint lzolen = MAXSIZE; lzo1x_999_compress(source, len, dest, &lzolen, lzo_wrkmem); return lzolen; #else return -1; #endif } return -1; } static length_t uncompress_packet(uint8_t *dest, const uint8_t *source, length_t len, int level) { if(level == 0) { memcpy(dest, source, len); return len; } else if(level > 9) { #ifdef HAVE_LZO lzo_uint lzolen = MAXSIZE; if(lzo1x_decompress_safe(source, len, dest, &lzolen, NULL) == LZO_E_OK) return lzolen; else #endif return -1; } #ifdef HAVE_ZLIB else { unsigned long destlen = MAXSIZE; if(uncompress(dest, &destlen, source, len) == Z_OK) return destlen; else return -1; } #endif return -1; } /* VPN packet I/O */ static void receive_packet(node_t *n, vpn_packet_t *packet) { ifdebug(TRAFFIC) logger(LOG_DEBUG, "Received packet of %d bytes from %s (%s)", packet->len, n->name, n->hostname); route(n, packet); } static bool try_mac(const node_t *n, const vpn_packet_t *inpkt) { unsigned char hmac[EVP_MAX_MD_SIZE]; if(!n->indigest || !n->inmaclength || !n->inkey || inpkt->len < sizeof inpkt->seqno + n->inmaclength) return false; HMAC(n->indigest, n->inkey, n->inkeylength, (unsigned char *) &inpkt->seqno, inpkt->len - n->inmaclength, (unsigned char *)hmac, NULL); return !memcmp(hmac, (char *) &inpkt->seqno + inpkt->len - n->inmaclength, n->inmaclength); } static void receive_udppacket(node_t *n, vpn_packet_t *inpkt) { vpn_packet_t pkt1, pkt2; vpn_packet_t *pkt[] = { &pkt1, &pkt2, &pkt1, &pkt2 }; int nextpkt = 0; vpn_packet_t *outpkt = pkt[0]; int outlen, outpad; unsigned char hmac[EVP_MAX_MD_SIZE]; int i; if(!n->inkey) { ifdebug(TRAFFIC) logger(LOG_DEBUG, "Got packet from %s (%s) but he hasn't got our key yet", n->name, n->hostname); return; } /* Check packet length */ if(inpkt->len < sizeof(inpkt->seqno) + n->inmaclength) { ifdebug(TRAFFIC) logger(LOG_DEBUG, "Got too short packet from %s (%s)", n->name, n->hostname); return; } /* Check the message authentication code */ if(n->indigest && n->inmaclength) { inpkt->len -= n->inmaclength; HMAC(n->indigest, n->inkey, n->inkeylength, (unsigned char *) &inpkt->seqno, inpkt->len, (unsigned char *)hmac, NULL); if(memcmp(hmac, (char *) &inpkt->seqno + inpkt->len, n->inmaclength)) { ifdebug(TRAFFIC) logger(LOG_DEBUG, "Got unauthenticated packet from %s (%s)", n->name, n->hostname); return; } } /* Decrypt the packet */ if(n->incipher) { outpkt = pkt[nextpkt++]; if(!EVP_DecryptInit_ex(&n->inctx, NULL, NULL, NULL, NULL) || !EVP_DecryptUpdate(&n->inctx, (unsigned char *) &outpkt->seqno, &outlen, (unsigned char *) &inpkt->seqno, inpkt->len) || !EVP_DecryptFinal_ex(&n->inctx, (unsigned char *) &outpkt->seqno + outlen, &outpad)) { ifdebug(TRAFFIC) logger(LOG_DEBUG, "Error decrypting packet from %s (%s): %s", n->name, n->hostname, ERR_error_string(ERR_get_error(), NULL)); return; } outpkt->len = outlen + outpad; inpkt = outpkt; } /* Check the sequence number */ inpkt->len -= sizeof(inpkt->seqno); inpkt->seqno = ntohl(inpkt->seqno); if(replaywin) { if(inpkt->seqno != n->received_seqno + 1) { if(inpkt->seqno >= n->received_seqno + replaywin * 8) { if(n->farfuture++ < replaywin >> 2) { logger(LOG_WARNING, "Packet from %s (%s) is %d seqs in the future, dropped (%u)", n->name, n->hostname, inpkt->seqno - n->received_seqno - 1, n->farfuture); return; } logger(LOG_WARNING, "Lost %d packets from %s (%s)", inpkt->seqno - n->received_seqno - 1, n->name, n->hostname); memset(n->late, 0, replaywin); } else if (inpkt->seqno <= n->received_seqno) { if((n->received_seqno >= replaywin * 8 && inpkt->seqno <= n->received_seqno - replaywin * 8) || !(n->late[(inpkt->seqno / 8) % replaywin] & (1 << inpkt->seqno % 8))) { logger(LOG_WARNING, "Got late or replayed packet from %s (%s), seqno %d, last received %d", n->name, n->hostname, inpkt->seqno, n->received_seqno); return; } } else { for(i = n->received_seqno + 1; i < inpkt->seqno; i++) n->late[(i / 8) % replaywin] |= 1 << i % 8; } } n->farfuture = 0; n->late[(inpkt->seqno / 8) % replaywin] &= ~(1 << inpkt->seqno % 8); } if(inpkt->seqno > n->received_seqno) n->received_seqno = inpkt->seqno; if(n->received_seqno > MAX_SEQNO) keyexpires = 0; /* Decompress the packet */ length_t origlen = inpkt->len; if(n->incompression) { outpkt = pkt[nextpkt++]; if((outpkt->len = uncompress_packet(outpkt->data, inpkt->data, inpkt->len, n->incompression)) < 0) { ifdebug(TRAFFIC) logger(LOG_ERR, "Error while uncompressing packet from %s (%s)", n->name, n->hostname); return; } inpkt = outpkt; origlen -= MTU/64 + 20; } inpkt->priority = 0; if(!inpkt->data[12] && !inpkt->data[13]) mtu_probe_h(n, inpkt, origlen); else receive_packet(n, inpkt); } void receive_tcppacket(connection_t *c, const char *buffer, int len) { vpn_packet_t outpkt; outpkt.len = len; if(c->options & OPTION_TCPONLY) outpkt.priority = 0; else outpkt.priority = -1; memcpy(outpkt.data, buffer, len); receive_packet(c->node, &outpkt); } static void send_udppacket(node_t *n, vpn_packet_t *origpkt) { vpn_packet_t pkt1, pkt2; vpn_packet_t *pkt[] = { &pkt1, &pkt2, &pkt1, &pkt2 }; vpn_packet_t *inpkt = origpkt; int nextpkt = 0; vpn_packet_t *outpkt; int origlen; int outlen, outpad; #if defined(SOL_IP) && defined(IP_TOS) static int priority = 0; #endif int origpriority; int sock; if(!n->status.reachable) { ifdebug(TRAFFIC) logger(LOG_INFO, "Trying to send UDP packet to unreachable node %s (%s)", n->name, n->hostname); return; } /* Make sure we have a valid key */ if(!n->status.validkey) { ifdebug(TRAFFIC) logger(LOG_INFO, "No valid key known yet for %s (%s), forwarding via TCP", n->name, n->hostname); if(n->last_req_key + 10 < now) { send_req_key(n); n->last_req_key = now; } send_tcppacket(n->nexthop->connection, origpkt); return; } if(n->options & OPTION_PMTU_DISCOVERY && inpkt->len > n->minmtu && (inpkt->data[12] | inpkt->data[13])) { ifdebug(TRAFFIC) logger(LOG_INFO, "Packet for %s (%s) larger than minimum MTU, forwarding via %s", n->name, n->hostname, n != n->nexthop ? n->nexthop->name : "TCP"); if(n != n->nexthop) send_packet(n->nexthop, origpkt); else send_tcppacket(n->nexthop->connection, origpkt); return; } origlen = inpkt->len; origpriority = inpkt->priority; /* Compress the packet */ if(n->outcompression) { outpkt = pkt[nextpkt++]; if((outpkt->len = compress_packet(outpkt->data, inpkt->data, inpkt->len, n->outcompression)) < 0) { ifdebug(TRAFFIC) logger(LOG_ERR, "Error while compressing packet to %s (%s)", n->name, n->hostname); return; } inpkt = outpkt; } /* Add sequence number */ inpkt->seqno = htonl(++(n->sent_seqno)); inpkt->len += sizeof(inpkt->seqno); /* Encrypt the packet */ if(n->outcipher) { outpkt = pkt[nextpkt++]; if(!EVP_EncryptInit_ex(&n->outctx, NULL, NULL, NULL, NULL) || !EVP_EncryptUpdate(&n->outctx, (unsigned char *) &outpkt->seqno, &outlen, (unsigned char *) &inpkt->seqno, inpkt->len) || !EVP_EncryptFinal_ex(&n->outctx, (unsigned char *) &outpkt->seqno + outlen, &outpad)) { ifdebug(TRAFFIC) logger(LOG_ERR, "Error while encrypting packet to %s (%s): %s", n->name, n->hostname, ERR_error_string(ERR_get_error(), NULL)); goto end; } outpkt->len = outlen + outpad; inpkt = outpkt; } /* Add the message authentication code */ if(n->outdigest && n->outmaclength) { HMAC(n->outdigest, n->outkey, n->outkeylength, (unsigned char *) &inpkt->seqno, inpkt->len, (unsigned char *) &inpkt->seqno + inpkt->len, NULL); inpkt->len += n->outmaclength; } /* Determine which socket we have to use */ for(sock = 0; sock < listen_sockets; sock++) if(n->address.sa.sa_family == listen_socket[sock].sa.sa.sa_family) break; if(sock >= listen_sockets) sock = 0; /* If none is available, just use the first and hope for the best. */ /* Send the packet */ #if defined(SOL_IP) && defined(IP_TOS) if(priorityinheritance && origpriority != priority && listen_socket[sock].sa.sa.sa_family == AF_INET) { priority = origpriority; ifdebug(TRAFFIC) logger(LOG_DEBUG, "Setting outgoing packet priority to %d", priority); if(setsockopt(listen_socket[sock].udp, SOL_IP, IP_TOS, &priority, sizeof(priority))) /* SO_PRIORITY doesn't seem to work */ logger(LOG_ERR, "System call `%s' failed: %s", "setsockopt", strerror(errno)); } #endif if(sendto(listen_socket[sock].udp, (char *) &inpkt->seqno, inpkt->len, 0, &(n->address.sa), SALEN(n->address.sa)) < 0 && !sockwouldblock(sockerrno)) { if(sockmsgsize(sockerrno)) { if(n->maxmtu >= origlen) n->maxmtu = origlen - 1; if(n->mtu >= origlen) n->mtu = origlen - 1; } else logger(LOG_ERR, "Error sending packet to %s (%s): %s", n->name, n->hostname, sockstrerror(sockerrno)); } end: origpkt->len = origlen; } /* send a packet to the given vpn ip. */ void send_packet(const node_t *n, vpn_packet_t *packet) { node_t *via; if(n == myself) { if(overwrite_mac) memcpy(packet->data, mymac.x, ETH_ALEN); write_packet(packet); return; } ifdebug(TRAFFIC) logger(LOG_ERR, "Sending packet of %d bytes to %s (%s)", packet->len, n->name, n->hostname); if(!n->status.reachable) { ifdebug(TRAFFIC) logger(LOG_INFO, "Node %s (%s) is not reachable", n->name, n->hostname); return; } via = (packet->priority == -1 || n->via == myself) ? n->nexthop : n->via; if(via != n) ifdebug(TRAFFIC) logger(LOG_INFO, "Sending packet to %s via %s (%s)", n->name, via->name, n->via->hostname); if(packet->priority == -1 || ((myself->options | via->options) & OPTION_TCPONLY)) { if(!send_tcppacket(via->connection, packet)) terminate_connection(via->connection, true); } else send_udppacket(via, packet); } /* Broadcast a packet using the minimum spanning tree */ void broadcast_packet(const node_t *from, vpn_packet_t *packet) { avl_node_t *node; connection_t *c; ifdebug(TRAFFIC) logger(LOG_INFO, "Broadcasting packet of %d bytes from %s (%s)", packet->len, from->name, from->hostname); if(from != myself) { send_packet(myself, packet); // In TunnelServer mode, do not forward broadcast packets. // The MST might not be valid and create loops. if(tunnelserver) return; } for(node = connection_tree->head; node; node = node->next) { c = node->data; if(c->status.active && c->status.mst && c != from->nexthop->connection) send_packet(c->node, packet); } } static node_t *try_harder(const sockaddr_t *from, const vpn_packet_t *pkt) { avl_node_t *node; edge_t *e; node_t *n = NULL; bool hard = false; static time_t last_hard_try = 0; for(node = edge_weight_tree->head; node; node = node->next) { e = node->data; if(e->to == myself) continue; if(sockaddrcmp_noport(from, &e->address)) { if(last_hard_try == now) continue; hard = true; } if(!try_mac(e->to, pkt)) continue; n = e->to; break; } if(hard) last_hard_try = now; return n; } void handle_incoming_vpn_data(int sock) { vpn_packet_t pkt; char *hostname; sockaddr_t from; socklen_t fromlen = sizeof(from); node_t *n; pkt.len = recvfrom(sock, (char *) &pkt.seqno, MAXSIZE, 0, &from.sa, &fromlen); if(pkt.len < 0) { if(!sockwouldblock(sockerrno)) logger(LOG_ERR, "Receiving packet failed: %s", sockstrerror(sockerrno)); return; } sockaddrunmap(&from); /* Some braindead IPv6 implementations do stupid things. */ n = lookup_node_udp(&from); if(!n) { n = try_harder(&from, &pkt); if(n) update_node_udp(n, &from); else ifdebug(PROTOCOL) { hostname = sockaddr2hostname(&from); logger(LOG_WARNING, "Received UDP packet from unknown source %s", hostname); free(hostname); return; } else return; } receive_udppacket(n, &pkt); }