py-scan-dns-openresolvers.py

#!/usr/bin/env python3

from sys import argv, exit as callexit
from time import time
from ipaddress import ip_network
from random import shuffle
import socket as sk

"""
    --- Python DNS Open Resolver Scanner ---
    Originally written in 2013 in Python2. Refactored in 2021 with Python3.
    It still uses Pure Python and the Low-level Python networking interface.

    PEP8 compliant
    “Readability counts."
    “Beautiful is better than ugly.”
    — The Zen of Python
"""

''' set packet to use a BSD Socket UDP datagram '''

PAYLOADHEX = 'ff0001000001000000000000016c0c726f6f\
              742d73657276657273036e65740000010001'  # "l.root-servers.net"

PREFIX = argv[1] if len(argv) > 1 else 0


def iplist():

    try:  # certify the IP Address format is valid

        IP_ADDR_COUNT = ip_network(PREFIX).num_addresses
        NETWORK_HOSTS = ip_network(PREFIX).hosts()

        if PREFIX == 0:
            callexit("Provide a HOST IP Address or an IP/CIDR as argument.")
        elif IP_ADDR_COUNT > 1:
            for IPADDRESS in NETWORK_HOSTS:
                yield IPADDRESS
        elif IP_ADDR_COUNT == 1:
            if '/32' in PREFIX:  # ex: 8.8.8.8/32 will become '8.8.8.8'
                yield PREFIX.split('/')[0]
            else:
                yield PREFIX

    except ValueError as error:
        print(f'iplist() function Error >>> {error}')


for HOST in iplist():

    try:

        with sk.socket(sk.AF_INET, sk.SOCK_DGRAM) as packet:

            packet.settimeout(0.100)

            ''' send the 'PAYLOADHEX' to HOSTs in the list (port 53 (DNS)) '''

            packet.sendto(bytes.fromhex(PAYLOADHEX), (str(HOST), int(53)))
            RESPONSE = packet.recv(128)

            ''' check if RESPONSE contains a valid DNS RESPONSE with
                l.root-servers.net's IP address 199.7.83.42  '''

            if (b'\xc0\x0c\x00\x01\x00\x01' and
                    b'\x00\x04\xc7\x07') in RESPONSE:
                UNIXTIME = int(time())
                print(f'{HOST},open,{UNIXTIME}')

    except sk.timeout:   # timeout generated by network conditions
        continue

    except ValueError as error:
        print(f'Error >>> {error}')

    except KeyboardInterrupt:
        callexit('Program execution interrupted.')