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         // Maximal amount of bytes transfered with single key (4 GiB)
  59         MaxBytesPerKey = 4294967296
  60 )
  61
  62 type TAP interface {
  63         io.Reader
  64         io.Writer
  65 }
  66
  67 type Peer struct {
  68         addr      *net.UDPAddr
  69         key       *[KeySize]byte // encryption key
  70         nonceOur  uint64         // nonce for our messages
  71         nonceRecv uint64         // latest received nonce from remote peer
  72 }
  73
  74 type UDPPkt struct {
  75         addr *net.UDPAddr
  76         size int
  77 }
  78
  79 func ScriptCall(path *string) {
  80         if *path == "" {
  81                 return
  82         }
  83         cmd := exec.Command(*path, *ifaceName)
  84         var out bytes.Buffer
  85         cmd.Stdout = &out
  86         if err := cmd.Run(); err != nil {
  87                 fmt.Println(time.Now(), "script error: ", err.Error(), string(out.Bytes()))
  88         }
  89 }
  90
  91 func main() {
  92         flag.Parse()
  93         timeout := *timeoutP
  94         verbose := *verboseP
  95         log.SetFlags(log.Ldate | log.Lmicroseconds | log.Lshortfile)
  96
  97         // Key decoding
  98         keyData, err := ioutil.ReadFile(*keyPath)
  99         if err != nil {
 100                 panic("Unable to read keyfile: " + err.Error())
 101         }
 102         if len(keyData) < 64 {
 103                 panic("Key must be 64 hex characters long")
 104         }
 105         keyDecoded, err := hex.DecodeString(string(keyData[0:64]))
 106         if err != nil {
 107                 panic("Unable to decode the key: " + err.Error())
 108         }
 109         key := new([KeySize]byte)
 110         copy(key[:], keyDecoded)
 111         keyDecoded = nil
 112         keyData = nil
 113
 114         // Interface listening
 115         maxIfacePktSize := *mtu - poly1305.TagSize - NonceSize
 116         log.Println("Max MTU", maxIfacePktSize, "on interface", *ifaceName)
 117         iface := NewTAP(*ifaceName)
 118         ethBuf := make([]byte, maxIfacePktSize)
 119         ethSink := make(chan int)
 120         ethSinkReady := make(chan bool)
 121         go func() {
 122                 for {
 123                         <-ethSinkReady
 124                         n, err := iface.Read(ethBuf)
 125                         if err != nil {
 126                                 panic(err)
 127                         }
 128                         ethSink <- n
 129                 }
 130         }()
 131         ethSinkReady <- true
 132
 133         // Network address parsing
 134         if (len(*bindAddr) > 1 && len(*remoteAddr) > 1) ||
 135                 (len(*bindAddr) == 0 && len(*remoteAddr) == 0) {
 136                 panic("Either -bind or -remote must be specified only")
 137         }
 138         var conn *net.UDPConn
 139         var remote *net.UDPAddr
 140         serverMode := false
 141         bindTo := "0.0.0.0:0"
 142
 143         if len(*bindAddr) > 1 {
 144                 bindTo = *bindAddr
 145                 serverMode = true
 146         }
 147
 148         bind, err := net.ResolveUDPAddr("udp", bindTo)
 149         if err != nil {
 150                 panic(err)
 151         }
 152         conn, err = net.ListenUDP("udp", bind)
 153         if err != nil {
 154                 panic(err)
 155         }
 156
 157         if len(*remoteAddr) > 1 {
 158                 remote, err = net.ResolveUDPAddr("udp", *remoteAddr)
 159                 if err != nil {
 160                         panic(err)
 161                 }
 162         }
 163
 164         udpBuf := make([]byte, *mtu)
 165         udpSink := make(chan *UDPPkt)
 166         udpSinkReady := make(chan bool)
 167         go func(conn *net.UDPConn) {
 168                 for {
 169                         <-udpSinkReady
 170                         conn.SetReadDeadline(time.Now().Add(time.Second))
 171                         n, addr, err := conn.ReadFromUDP(udpBuf)
 172                         if err != nil {
 173                                 if verbose {
 174                                         fmt.Print("B")
 175                                 }
 176                                 udpSink <- nil
 177                         } else {
 178                                 udpSink <- &UDPPkt{addr, n}
 179                         }
 180                 }
 181         }(conn)
 182         udpSinkReady <- true
 183
 184         // Process packets
 185         var udpPkt *UDPPkt
 186         var udpPktData []byte
 187         var ethPktSize int
 188         var frame []byte
 189         var addr string
 190         var peer *Peer
 191         var p *Peer
 192
 193         timeouts := 0
 194         bytes := 0
 195         states := make(map[string]*Handshake)
 196         nonce := make([]byte, NonceSize)
 197         keyAuth := new([KeySize]byte)
 198         tag := new([poly1305.TagSize]byte)
 199         buf := make([]byte, *mtu+S20BS)
 200         emptyKey := make([]byte, KeySize)
 201
 202         if !serverMode {
 203                 states[remote.String()] = HandshakeStart(conn, remote, key)
 204         }
 205
 206         heartbeat := time.Tick(time.Second * time.Duration(timeout/3))
 207         go func() { <-heartbeat }()
 208         heartbeatMark := []byte(HeartBeatMark)
 209
 210         termSignal := make(chan os.Signal, 1)
 211         signal.Notify(termSignal, os.Interrupt, os.Kill)
 212
 213         finished := false
 214         for {
 215                 if finished {
 216                         break
 217                 }
 218                 if !serverMode && bytes > MaxBytesPerKey {
 219                         states[remote.String()] = HandshakeStart(conn, remote, key)
 220                         bytes = 0
 221                 }
 222                 select {
 223                 case <-termSignal:
 224                         finished = true
 225                 case <-heartbeat:
 226                         go func() { ethSink <- -1 }()
 227                 case udpPkt = <-udpSink:
 228                         timeouts++
 229                         if !serverMode && timeouts >= timeout {
 230                                 finished = true
 231                         }
 232                         if udpPkt == nil {
 233                                 udpSinkReady <- true
 234                                 continue
 235                         }
 236                         udpPktData = udpBuf[:udpPkt.size]
 237                         if isValidHandshakePkt(udpPktData) {
 238                                 addr = udpPkt.addr.String()
 239                                 state, exists := states[addr]
 240                                 if serverMode {
 241                                         if !exists {
 242                                                 state = &Handshake{addr: udpPkt.addr}
 243                                                 states[addr] = state
 244                                         }
 245                                         p = state.Server(conn, key, udpPktData)
 246                                 } else {
 247                                         if !exists {
 248                                                 fmt.Print("[HS?]")
 249                                                 udpSinkReady <- true
 250                                                 continue
 251                                         }
 252                                         p = state.Client(conn, key, udpPktData)
 253                                 }
 254                                 if p != nil {
 255                                         fmt.Print("[HS-OK]")
 256                                         if peer == nil {
 257                                                 go ScriptCall(upPath)
 258                                         }
 259                                         peer = p
 260                                         delete(states, addr)
 261                                 }
 262                                 udpSinkReady <- true
 263                                 continue
 264                         }
 265                         if peer == nil {
 266                                 udpSinkReady <- true
 267                                 continue
 268                         }
 269                         nonceRecv, _ := binary.Uvarint(udpPktData[:8])
 270                         if peer.nonceRecv >= nonceRecv {
 271                                 fmt.Print("R")
 272                                 udpSinkReady <- true
 273                                 continue
 274                         }
 275                         copy(buf[:KeySize], emptyKey)
 276                         copy(tag[:], udpPktData[udpPkt.size-poly1305.TagSize:])
 277                         copy(buf[S20BS:], udpPktData[NonceSize:udpPkt.size-poly1305.TagSize])
 278                         salsa20.XORKeyStream(
 279                                 buf[:S20BS+udpPkt.size-poly1305.TagSize],
 280                                 buf[:S20BS+udpPkt.size-poly1305.TagSize],
 281                                 udpPktData[:NonceSize],
 282                                 peer.key,
 283                         )
 284                         copy(keyAuth[:], buf[:KeySize])
 285                         if !poly1305.Verify(tag, udpPktData[:udpPkt.size-poly1305.TagSize], keyAuth) {
 286                                 udpSinkReady <- true
 287                                 fmt.Print("T")
 288                                 continue
 289                         }
 290                         udpSinkReady <- true
 291                         peer.nonceRecv = nonceRecv
 292                         timeouts = 0
 293                         frame = buf[S20BS : S20BS+udpPkt.size-NonceSize-poly1305.TagSize]
 294                         bytes += len(frame)
 295                         if string(frame[0:HeartBeatSize]) == HeartBeatMark {
 296                                 continue
 297                         }
 298                         if _, err := iface.Write(frame); err != nil {
 299                                 log.Println("Error writing to iface: ", err)
 300                         }
 301                         if verbose {
 302                                 fmt.Print("r")
 303                         }
 304                 case ethPktSize = <-ethSink:
 305                         if ethPktSize > maxIfacePktSize {
 306                                 panic("Too large packet on interface")
 307                         }
 308                         if peer == nil {
 309                                 ethSinkReady <- true
 310                                 continue
 311                         }
 312                         peer.nonceOur = peer.nonceOur + 2
 313                         binary.PutUvarint(nonce, peer.nonceOur)
 314                         copy(buf[:KeySize], emptyKey)
 315                         if ethPktSize > -1 {
 316                                 copy(buf[S20BS:], ethBuf[:ethPktSize])
 317                                 ethSinkReady <- true
 318                         } else {
 319                                 copy(buf[S20BS:], heartbeatMark)
 320                                 ethPktSize = HeartBeatSize
 321                         }
 322                         salsa20.XORKeyStream(buf, buf, nonce, peer.key)
 323                         copy(buf[S20BS-NonceSize:S20BS], nonce)
 324                         copy(keyAuth[:], buf[:KeySize])
 325                         dataToSend := buf[S20BS-NonceSize : S20BS+ethPktSize]
 326                         poly1305.Sum(tag, dataToSend, keyAuth)
 327                         bytes += len(dataToSend)
 328                         if _, err := conn.WriteTo(append(dataToSend, tag[:]...), peer.addr); err != nil {
 329                                 log.Println("Error sending UDP", err)
 330                         }
 331                         if verbose {
 332                                 fmt.Print("w")
 333                         }
 334                 }
 335         }
 336         ScriptCall(downPath)
 337 }