govpn.go

   1 /*
   2 govpn -- high-performance secure virtual private network daemon
   3 Copyright (C) 2014 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 package main
  19
  20 import (
  21         "bytes"
  22         "encoding/binary"
  23         "encoding/hex"
  24         "flag"
  25         "fmt"
  26         "io"
  27         "io/ioutil"
  28         "log"
  29         "net"
  30         "os"
  31         "os/exec"
  32         "os/signal"
  33         "time"
  34
  35         "code.google.com/p/go.crypto/poly1305"
  36         "code.google.com/p/go.crypto/salsa20"
  37 )
  38
  39 var (
  40         remoteAddr = flag.String("remote", "", "Remote server address")
  41         bindAddr   = flag.String("bind", "", "Bind to address")
  42         ifaceName  = flag.String("iface", "tap0", "TAP network interface")
  43         keyPath    = flag.String("key", "", "Path to authentication key file")
  44         upPath     = flag.String("up", "", "Path to up-script")
  45         downPath   = flag.String("down", "", "Path to down-script")
  46         mtu        = flag.Int("mtu", 1500, "MTU")
  47         timeoutP   = flag.Int("timeout", 60, "Timeout seconds")
  48         verboseP   = flag.Bool("v", false, "Increase verbosity")
  49 )
  50
  51 const (
  52         NonceSize = 8
  53         KeySize   = 32
  54         // S20BS is Salsa20's internal blocksize in bytes
  55         S20BS         = 64
  56         HeartBeatSize = 12
  57         HeartBeatMark = "\x00\x00\x00HEARTBEAT"
  58 )
  59
  60 type TAP interface {
  61         io.Reader
  62         io.Writer
  63 }
  64
  65 type Peer struct {
  66         addr      *net.UDPAddr
  67         key       *[KeySize]byte // encryption key
  68         nonceOur  uint64         // nonce for our messages
  69         nonceRecv uint64         // latest received nonce from remote peer
  70 }
  71
  72 type UDPPkt struct {
  73         addr *net.UDPAddr
  74         size int
  75 }
  76
  77 func ScriptCall(path *string) {
  78         if *path == "" {
  79                 return
  80         }
  81         cmd := exec.Command(*path, *ifaceName)
  82         var out bytes.Buffer
  83         cmd.Stdout = &out
  84         if err := cmd.Run(); err != nil {
  85                 fmt.Println(time.Now(), "script error: ", err.Error(), string(out.Bytes()))
  86         }
  87 }
  88
  89 func main() {
  90         flag.Parse()
  91         timeout := *timeoutP
  92         verbose := *verboseP
  93         log.SetFlags(log.Ldate | log.Lmicroseconds | log.Lshortfile)
  94
  95         // Key decoding
  96         keyData, err := ioutil.ReadFile(*keyPath)
  97         if err != nil {
  98                 panic("Unable to read keyfile: " + err.Error())
  99         }
 100         if len(keyData) < 64 {
 101                 panic("Key must be 64 hex characters long")
 102         }
 103         keyDecoded, err := hex.DecodeString(string(keyData[0:64]))
 104         if err != nil {
 105                 panic("Unable to decode the key: " + err.Error())
 106         }
 107         key := new([KeySize]byte)
 108         copy(key[:], keyDecoded)
 109         keyDecoded = nil
 110         keyData = nil
 111
 112         // Interface listening
 113         maxIfacePktSize := *mtu - poly1305.TagSize - NonceSize
 114         log.Println("Max MTU", maxIfacePktSize, "on interface", *ifaceName)
 115         iface := NewTAP(*ifaceName)
 116         ethBuf := make([]byte, maxIfacePktSize)
 117         ethSink := make(chan int)
 118         ethSinkReady := make(chan bool)
 119         go func() {
 120                 for {
 121                         <-ethSinkReady
 122                         n, err := iface.Read(ethBuf)
 123                         if err != nil {
 124                                 panic(err)
 125                         }
 126                         ethSink <- n
 127                 }
 128         }()
 129         ethSinkReady <- true
 130
 131         // Network address parsing
 132         if (len(*bindAddr) > 1 && len(*remoteAddr) > 1) ||
 133                 (len(*bindAddr) == 0 && len(*remoteAddr) == 0) {
 134                 panic("Either -bind or -remote must be specified only")
 135         }
 136         var conn *net.UDPConn
 137         var remote *net.UDPAddr
 138         serverMode := false
 139         bindTo := "0.0.0.0:0"
 140
 141         if len(*bindAddr) > 1 {
 142                 bindTo = *bindAddr
 143                 serverMode = true
 144         }
 145
 146         bind, err := net.ResolveUDPAddr("udp", bindTo)
 147         if err != nil {
 148                 panic(err)
 149         }
 150         conn, err = net.ListenUDP("udp", bind)
 151         if err != nil {
 152                 panic(err)
 153         }
 154
 155         if len(*remoteAddr) > 1 {
 156                 remote, err = net.ResolveUDPAddr("udp", *remoteAddr)
 157                 if err != nil {
 158                         panic(err)
 159                 }
 160         }
 161
 162         udpBuf := make([]byte, *mtu)
 163         udpSink := make(chan *UDPPkt)
 164         udpSinkReady := make(chan bool)
 165         go func(conn *net.UDPConn) {
 166                 for {
 167                         <-udpSinkReady
 168                         conn.SetReadDeadline(time.Now().Add(time.Second))
 169                         n, addr, err := conn.ReadFromUDP(udpBuf)
 170                         if err != nil {
 171                                 if verbose {
 172                                         fmt.Print("B")
 173                                 }
 174                                 udpSink <- nil
 175                         } else {
 176                                 udpSink <- &UDPPkt{addr, n}
 177                         }
 178                 }
 179         }(conn)
 180         udpSinkReady <- true
 181
 182         // Process packets
 183         var udpPkt *UDPPkt
 184         var udpPktData []byte
 185         var ethPktSize int
 186         var frame []byte
 187         var addr string
 188         var peer *Peer
 189         var p *Peer
 190
 191         timeouts := 0
 192         states := make(map[string]*Handshake)
 193         nonce := make([]byte, NonceSize)
 194         keyAuth := new([KeySize]byte)
 195         tag := new([poly1305.TagSize]byte)
 196         buf := make([]byte, *mtu+S20BS)
 197         emptyKey := make([]byte, KeySize)
 198         ethPkt := make([]byte, maxIfacePktSize)
 199         udpPktDataBuf := make([]byte, *mtu)
 200
 201         if !serverMode {
 202                 states[remote.String()] = HandshakeStart(conn, remote, key)
 203         }
 204
 205         heartbeat := time.Tick(time.Second * time.Duration(timeout/3))
 206         heartbeatMark := []byte(HeartBeatMark)
 207
 208         termSignal := make(chan os.Signal, 1)
 209         signal.Notify(termSignal, os.Interrupt, os.Kill)
 210
 211         finished := false
 212         for {
 213                 if finished {
 214                         break
 215                 }
 216                 select {
 217                 case <-termSignal:
 218                         finished = true
 219                 case <-heartbeat:
 220                         go func() { ethSink <- -1 }()
 221                 case udpPkt = <-udpSink:
 222                         timeouts++
 223                         if !serverMode && timeouts >= timeout {
 224                                 finished = true
 225                         }
 226                         if udpPkt == nil {
 227                                 udpSinkReady <- true
 228                                 continue
 229                         }
 230                         copy(udpPktDataBuf, udpBuf[:udpPkt.size])
 231                         udpSinkReady <- true
 232                         udpPktData = udpPktDataBuf[:udpPkt.size]
 233                         if isValidHandshakePkt(udpPktData) {
 234                                 addr = udpPkt.addr.String()
 235                                 state, exists := states[addr]
 236                                 if serverMode {
 237                                         if !exists {
 238                                                 state = &Handshake{addr: udpPkt.addr}
 239                                                 states[addr] = state
 240                                         }
 241                                         p = state.Server(conn, key, udpPktData)
 242                                 } else {
 243                                         if !exists {
 244                                                 fmt.Print("[HS?]")
 245                                                 continue
 246                                         }
 247                                         p = state.Client(conn, key, udpPktData)
 248                                 }
 249                                 if p != nil {
 250                                         fmt.Print("[HS-OK]")
 251                                         peer = p
 252                                         delete(states, addr)
 253                                         go ScriptCall(upPath)
 254                                 }
 255                                 continue
 256                         }
 257                         if peer == nil {
 258                                 continue
 259                         }
 260                         nonceRecv, _ := binary.Uvarint(udpPktData[:8])
 261                         if peer.nonceRecv >= nonceRecv {
 262                                 fmt.Print("R")
 263                                 continue
 264                         }
 265                         copy(buf[:KeySize], emptyKey)
 266                         copy(tag[:], udpPktData[udpPkt.size-poly1305.TagSize:])
 267                         copy(buf[S20BS:], udpPktData[NonceSize:udpPkt.size-poly1305.TagSize])
 268                         salsa20.XORKeyStream(
 269                                 buf[:S20BS+udpPkt.size-poly1305.TagSize],
 270                                 buf[:S20BS+udpPkt.size-poly1305.TagSize],
 271                                 udpPktData[:NonceSize],
 272                                 peer.key,
 273                         )
 274                         copy(keyAuth[:], buf[:KeySize])
 275                         if !poly1305.Verify(tag, udpPktData[:udpPkt.size-poly1305.TagSize], keyAuth) {
 276                                 fmt.Print("T")
 277                                 continue
 278                         }
 279                         peer.nonceRecv = nonceRecv
 280                         timeouts = 0
 281                         frame = buf[S20BS : S20BS+udpPkt.size-NonceSize-poly1305.TagSize]
 282                         if string(frame[0:HeartBeatSize]) == HeartBeatMark {
 283                                 continue
 284                         }
 285                         if _, err := iface.Write(frame); err != nil {
 286                                 log.Println("Error writing to iface: ", err)
 287                         }
 288                         if verbose {
 289                                 fmt.Print("r")
 290                         }
 291                 case ethPktSize = <-ethSink:
 292                         if ethPktSize > maxIfacePktSize {
 293                                 panic("Too large packet on interface")
 294                         }
 295                         if peer == nil {
 296                                 ethSinkReady <- true
 297                                 continue
 298                         }
 299                         if ethPktSize > -1 {
 300                                 copy(ethPkt, ethBuf[:ethPktSize])
 301                                 ethSinkReady <- true
 302                         } else {
 303                                 copy(ethPkt, heartbeatMark)
 304                                 ethPktSize = HeartBeatSize
 305                         }
 306                         peer.nonceOur = peer.nonceOur + 2
 307                         binary.PutUvarint(nonce, peer.nonceOur)
 308                         copy(buf[:KeySize], emptyKey)
 309                         copy(buf[S20BS:], ethPkt[:ethPktSize])
 310                         salsa20.XORKeyStream(buf, buf, nonce, peer.key)
 311                         copy(buf[S20BS-NonceSize:S20BS], nonce)
 312                         copy(keyAuth[:], buf[:KeySize])
 313                         dataToSend := buf[S20BS-NonceSize : S20BS+ethPktSize]
 314                         poly1305.Sum(tag, dataToSend, keyAuth)
 315                         if _, err := conn.WriteTo(append(dataToSend, tag[:]...), peer.addr); err != nil {
 316                                 log.Println("Error sending UDP", err)
 317                         }
 318                         if verbose {
 319                                 fmt.Print("w")
 320                         }
 321                 }
 322         }
 323         ScriptCall(downPath)
 324 }