func (p *PacketSprayer) SetIPLayer(iplayer layers.IPv4) error {
p.ip = iplayer
p.ipBuf = gopacket.NewSerializeBuffer()
opts := gopacket.SerializeOptions{
FixLengths: true,
ComputeChecksums: true,
}
err := p.ip.SerializeTo(p.ipBuf, opts)
if err != nil {
return err
}
p.ipHeader, err = ipv4.ParseHeader(p.ipBuf.Bytes())
if err != nil {
return err
}
return nil
}
func (i *TCPStreamInjector) SetIPLayer(iplayer layers.IPv4) error {
i.ip = iplayer
i.ipBuf = gopacket.NewSerializeBuffer()
opts := gopacket.SerializeOptions{
FixLengths: true,
ComputeChecksums: true,
}
err := i.ip.SerializeTo(i.ipBuf, opts)
if err != nil {
return err
}
i.ipHeader, err = ipv4.ParseHeader(i.ipBuf.Bytes())
if err != nil {
return err
}
return nil
}
//sendPacket generates & sends a packet of arbitrary size to a specific destination.
//The size specified should be larger then 40bytes.
func sendPacket(sourceIP string, destinationIP string, size int, message string, appID int, chanID int, icmpType layers.ICMPv4TypeCode) []byte {
var payloadSize int
if size < 28 {
//Unable to create smaller packets.
payloadSize = 0
} else {
payloadSize = size - 28
}
//Convert IP to 4bit representation
srcIP := net.ParseIP(sourceIP).To4()
dstIP := net.ParseIP(destinationIP).To4()
//IP Layer
ip := layers.IPv4{
SrcIP: srcIP,
DstIP: dstIP,
Version: 4,
TTL: 64,
Protocol: layers.IPProtocolICMPv4,
}
icmp := layers.ICMPv4{
TypeCode: icmpType,
}
opts := gopacket.SerializeOptions{
FixLengths: true,
ComputeChecksums: true,
}
ipHeaderBuf := gopacket.NewSerializeBuffer()
err := ip.SerializeTo(ipHeaderBuf, opts)
if err != nil {
panic(err)
}
//Set "Don't Fragment"-Flag in Header
ipHeader, err := ipv4.ParseHeader(ipHeaderBuf.Bytes())
ipHeader.Flags |= ipv4.DontFragment
if err != nil {
panic(err)
}
payloadBuf := gopacket.NewSerializeBuffer()
//Influence the payload size
payload := gopacket.Payload(generatePayload(payloadSize, ","+strconv.Itoa(appID)+","+strconv.Itoa(chanID)+","+message+","))
err = gopacket.SerializeLayers(payloadBuf, opts, &icmp, payload)
if err != nil {
panic(err)
}
//Send packet
var packetConn net.PacketConn
var rawConn *ipv4.RawConn
packetConn, err = net.ListenPacket("ip4:icmp", srcIP.String())
if err != nil {
panic(err)
}
rawConn, err = ipv4.NewRawConn(packetConn)
if err != nil {
panic(err)
}
err = rawConn.WriteTo(ipHeader, payloadBuf.Bytes(), nil)
return append(ipHeaderBuf.Bytes(), payloadBuf.Bytes()...)
}
func sndrThread(conn *net.UDPConn, iface *water.Interface) {
// first time fill with random numbers
ivbuf := make([]byte, aes.BlockSize)
if _, err := io.ReadFull(rand.Reader, ivbuf); err != nil {
log.Fatalln("Unable to get rand data:", err)
}
var packet IPPacket = make([]byte, BUFFERSIZE)
for {
plen, err := iface.Read(packet[2 : MTU+2])
if err != nil {
break
}
if 4 != packet.IPver() {
header, _ := ipv4.ParseHeader(packet[2:])
log.Printf("Non IPv4 packet [%+v]\n", header)
continue
}
// each time get pointer to (probably) new config
c := config.Load().(VPNState)
dst := packet.Dst()
wanted := false
addr, ok := c.remotes[dst]
if ok {
wanted = true
}
if dst == c.Main.bcastIP || packet.IsMulticast() {
wanted = true
}
// very ugly and useful only for a limited numbers of routes!
if !wanted {
ip := packet.DstV4()
for n, s := range c.routes {
if n.Contains(ip) {
addr = s
ok = true
wanted = true
break
}
}
}
if wanted {
// store orig packet len
packet[0] = byte(plen % 256)
packet[1] = byte(plen / 256)
// encrypt
clen := plen + 2
if clen%aes.BlockSize != 0 {
clen += aes.BlockSize - (clen % aes.BlockSize)
}
if clen > len(packet) {
log.Println("clen > len(package)", clen, len(packet))
continue
}
ciphertext := make([]byte, aes.BlockSize+clen)
iv := ciphertext[:aes.BlockSize]
copy(iv, ivbuf)
mode := cipher.NewCBCEncrypter(c.Main.block, iv)
mode.CryptBlocks(ciphertext[aes.BlockSize:], packet[:clen])
// save new iv
copy(ivbuf, ciphertext[clen-aes.BlockSize:])
if ok {
n, err := conn.WriteToUDP(ciphertext, addr)
if nil != err {
log.Println("Error sending package:", err)
}
if n != len(ciphertext) {
log.Println("Only ", n, " bytes of ", len(ciphertext), " sent")
}
} else {
// multicast or broadcast
for _, addr := range c.remotes {
n, err := conn.WriteToUDP(ciphertext, addr)
if nil != err {
log.Println("Error sending package:", err)
}
if n != len(ciphertext) {
log.Println("Only ", n, " bytes of ", len(ciphertext), " sent")
}
}
}
} else {
fmt.Println("Unknown dst", dst)
}
}
}
