src/govpn/cmd/govpn-server/tcp.go

   1 /*
   2 GoVPN -- simple secure free software virtual private network daemon
   3 Copyright (C) 2014-2015 Sergey Matveev <stargrave@stargrave.org>
   4
   5 This program is free software: you can redistribute it and/or modify
   6 it under the terms of the GNU General Public License as published by
   7 the Free Software Foundation, either version 3 of the License, or
   8 (at your option) any later version.
   9
  10 This program is distributed in the hope that it will be useful,
  11 but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 GNU General Public License for more details.
  14
  15 You should have received a copy of the GNU General Public License
  16 along with this program.  If not, see <http://www.gnu.org/licenses/>.
  17 */
  18
  19 package main
  20
  21 import (
  22         "bytes"
  23         "encoding/binary"
  24         "log"
  25         "net"
  26         "time"
  27
  28         "govpn"
  29 )
  30
  31 func startTCP() {
  32         bind, err := net.ResolveTCPAddr("tcp", *bindAddr)
  33         if err != nil {
  34                 log.Fatalln("Can not resolve bind address:", err)
  35         }
  36         listener, err := net.ListenTCP("tcp", bind)
  37         if err != nil {
  38                 log.Fatalln("Can not listen on TCP:", err)
  39         }
  40         log.Println("Listening on TCP:" + *bindAddr)
  41         go func() {
  42                 for {
  43                         conn, err := listener.AcceptTCP()
  44                         if err != nil {
  45                                 log.Println("Error accepting TCP:", err)
  46                                 continue
  47                         }
  48                         go handleTCP(conn)
  49                 }
  50         }()
  51 }
  52
  53 func handleTCP(conn net.Conn) {
  54         addr := conn.RemoteAddr().String()
  55         buf := make([]byte, govpn.MTU)
  56         var n int
  57         var err error
  58         var prev int
  59         var hs *govpn.Handshake
  60         var ps *PeerState
  61         var peer *govpn.Peer
  62         var tap *govpn.TAP
  63         var conf *govpn.PeerConf
  64         for {
  65                 if prev == govpn.MTU {
  66                         break
  67                 }
  68                 conn.SetReadDeadline(time.Now().Add(time.Duration(govpn.TimeoutDefault) * time.Second))
  69                 n, err = conn.Read(buf[prev:])
  70                 if err != nil {
  71                         // Either EOFed or timeouted
  72                         break
  73                 }
  74                 prev += n
  75                 peerId := govpn.IDsCache.Find(buf[:prev])
  76                 if peerId == nil {
  77                         continue
  78                 }
  79                 if hs == nil {
  80                         conf = peerId.Conf()
  81                         if conf == nil {
  82                                 log.Println("Can not get peer configuration:", peerId.String())
  83                                 break
  84                         }
  85                         hs = govpn.NewHandshake(addr, conn, conf)
  86                 }
  87                 peer = hs.Server(buf[:prev])
  88                 prev = 0
  89                 if peer == nil {
  90                         continue
  91                 }
  92                 hs.Zero()
  93                 log.Println("Peer handshake finished:", addr, peer.Id.String())
  94                 peersByIdLock.RLock()
  95                 addrPrev, exists := peersById[*peer.Id]
  96                 peersByIdLock.RUnlock()
  97                 if exists {
  98                         peersLock.RLock()
  99                         tap = peers[addrPrev].tap
 100                         ps = &PeerState{
 101                                 peer:       peer,
 102                                 tap:        tap,
 103                                 terminator: peers[addrPrev].terminator,
 104                         }
 105                         peersLock.RUnlock()
 106                         ps.terminator <- struct{}{}
 107                         peersLock.Lock()
 108                         peersByIdLock.Lock()
 109                         kpLock.Lock()
 110                         delete(peers, addrPrev)
 111                         delete(knownPeers, addrPrev)
 112                         delete(peersById, *peer.Id)
 113                         peers[addr] = ps
 114                         knownPeers[addr] = &peer
 115                         peersById[*peer.Id] = addr
 116                         peersLock.Unlock()
 117                         peersByIdLock.Unlock()
 118                         kpLock.Unlock()
 119                         go peerReady(*ps)
 120                         log.Println("Rehandshake processed:", peer.Id.String())
 121                 } else {
 122                         ifaceName, err := callUp(peer.Id)
 123                         if err != nil {
 124                                 break
 125                         }
 126                         tap, err = govpn.TAPListen(ifaceName)
 127                         if err != nil {
 128                                 log.Println("Unable to create TAP:", err)
 129                                 break
 130                         }
 131                         ps = &PeerState{
 132                                 peer:       peer,
 133                                 tap:        tap,
 134                                 terminator: make(chan struct{}, 1),
 135                         }
 136                         go peerReady(*ps)
 137                         peersLock.Lock()
 138                         peersByIdLock.Lock()
 139                         kpLock.Lock()
 140                         peers[addr] = ps
 141                         peersById[*peer.Id] = addr
 142                         knownPeers[addr] = &peer
 143                         peersLock.Unlock()
 144                         peersByIdLock.Unlock()
 145                         kpLock.Unlock()
 146                         log.Println("Peer created:", peer.Id.String())
 147                 }
 148                 break
 149         }
 150         if hs != nil {
 151                 hs.Zero()
 152         }
 153         if peer == nil {
 154                 return
 155         }
 156
 157         nonceExpectation := make([]byte, govpn.NonceSize)
 158         binary.BigEndian.PutUint64(nonceExpectation, peer.NonceExpect)
 159         peer.NonceCipher.Encrypt(nonceExpectation, nonceExpectation)
 160         prev = 0
 161         var i int
 162         for {
 163                 if prev == govpn.MTU {
 164                         break
 165                 }
 166                 conn.SetReadDeadline(time.Now().Add(conf.Timeout))
 167                 n, err = conn.Read(buf[prev:])
 168                 if err != nil {
 169                         // Either EOFed or timeouted
 170                         break
 171                 }
 172                 prev += n
 173         CheckMore:
 174                 if prev < govpn.MinPktLength {
 175                         continue
 176                 }
 177                 i = bytes.Index(buf[:prev], nonceExpectation)
 178                 if i == -1 {
 179                         continue
 180                 }
 181                 if !peer.PktProcess(buf[:i+govpn.NonceSize], tap, false) {
 182                         log.Println(
 183                                 "Unauthenticated packet, dropping connection",
 184                                 addr, peer.Id.String(),
 185                         )
 186                         break
 187                 }
 188                 binary.BigEndian.PutUint64(nonceExpectation, peer.NonceExpect)
 189                 peer.NonceCipher.Encrypt(nonceExpectation, nonceExpectation)
 190                 copy(buf, buf[i+govpn.NonceSize:prev])
 191                 prev = prev - i - govpn.NonceSize
 192                 goto CheckMore
 193         }
 194         peer.Zero()
 195 }