I am building a Python program to modify request inside a packet but I am getting layer TCP not found error in netfilterqueue.global_callback ignored error. Why this error is coming?

Question

1.00/5 (1 vote)

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, +

[+] Request >>
Exception TypeError: "'module' object has no attribute '__getitem__'" in 'netfilterqueue.global_callback' ignored

Exception IndexError: IndexError('Layer [TCP] not found',) in 'netfilterqueue.global_callback' ignored

These two errors come while executing my python code given:

What I have tried:

#!/usr/bin/env python
import netfilterqueue
import scapy.all as scapy
import re

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

def process_packet(packet):
scapy_packet = scapy.IP(packet.get_payload())
if scapy_packet.haslayer(scapy.Raw):
if scapy_packet[scapy.TCP].dport == 80:
print("[+] Request >>")
modified_load = re.sub("Accept-Encoding:.*?\\r\\n", "", scapy_packet[scapy.Raw].load)
new_packet = set_load(scapy_packet, modified_load)
packet.set_payload(str(new_packet))
elif scapy_packet[scapy.TCP].sport == 80:
print("[+] Response >>")
print(scapy_packet.show())

packet.accept()

queue = netfilterqueue.NetfilterQueue()
queue.bind(0, process_packet)

queue.run()

Posted 16-Nov-18 3:07am

Member 14056957

Updated 16-Dec-20 5:06am

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Member 14888563 · Answer 1 · 2020-07-13T10:26:00

Solution 1

hi I would change your if statement to:

if scapy.Raw in scapy_packet and scapy.TCP in scapy_packet:

instead of:

if scapy_packet.haslayer(scapy.Raw):

Posted 13-Jul-20 10:26am

Member 14888563

Member 15022892 · Answer 2 · 2020-12-16T05:06:00

Compare this with yours though its the same code but I changed some variables.
Make sure your are testing it on http(port 80) not https(port443) and be mindful of your indents too

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):
        if scapy_packet[scapy.TCP].dport == 80:
            print('Request..')
            mod_load = re.sub('Accept-Encoding:.*?\\r\\n','',scapy_packet[scapy.Raw].load)
            new_pack = set_load(scapy_packet, mod_load)
            packet.set_payload(str(new_pack))
        elif scapy_packet[scapy.TCP].sport == 80:
                print('Response...')
                print(scapy_packet.show())



    packet.accept()


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