0

I've written one small python script to fix the checksum of L3-4 protocols using scapy. When I'm running the script it is not taking command line argument or may be some other reason it is not generating the fix checksum pcap. I've verified the rdpcap() from scapy command line it is working file using script it is not getting executed. My program is

import sys
import logging
logging.getLogger("scapy").setLevel(1)
try:
    from scapy.all import *
except ImportError:
import scapy
if len(sys.argv) != 3: 
    print "Usage:./ChecksumFixer  <input_pcap_file> <output_pcap_file>"
    print "Example: ./ChecksumFixer input.pcap output.pcap"
    sys.exit(1)

#------------------------Command Line Argument---------------------------------------

input_file = sys.argv[1]
output_file = sys.argv[2]

#------------------------Get The layer and Fix Checksum-------------------------------

def getLayer(p):
    for paktype in (scapy.IP, scapy.TCP, scapy.UDP, scapy.ICMP):
        try:
            p.getlayer(paktype).chksum = None
        except: AttributeError
        pass
    return p
#-----------------------FixPcap in input file and write to output fi`enter code here`le----------------

def fixpcap():
    paks = scapy.rdpcap(input_file)
    fc = map(getLayer, paks)
    scapy.wrpcap(output_file, fc)
ifexploit
  • 101
  • 6

1 Answers1

2

The reason your function is not executed is that you're not invoking it. Adding a call to fixpcap() at the end of your script shall fix this issue.

Furthermore, here are a few more corrections & suggestions:

  1. The statement following except Exception: should be indented as well, as follows:

    try:
    from scapy.all import *
except ImportError:
    import scapy

  2. Use argparse to parse command-line arguments.

  3. Wrap your main code in a if __name__ == '__main__': block.

Community
  • 1
  • 1
Yoel
  • 9,144
  • 7
  • 42
  • 57