compare_dns.py

import re
import socket

from dns.resolver import NoAnswer, Resolver


def make_resolver(ip_or_domain):
    if re.match(r"\d+\.\d+\.\d+\.\d+", ip_or_domain):
        ns_ip = ip_or_domain
    else:
        ns_ip = socket.gethostbyname(ip_or_domain)
    resolver = Resolver(configure=False)
    resolver.nameservers = [ns_ip]
    return resolver


class RecordComparator:
    def __init__(self, nsdomain1, nsdomain2):
        self.nsdomain1 = nsdomain1
        self.nsdomain2 = nsdomain2
        self.resolver1 = make_resolver(nsdomain1)
        self.resolver2 = make_resolver(nsdomain2)

    def compare_all_records(self, records):
        matches = 0
        mismatches = 0
        for record in records:
            match = self.compare_records(*record)
            if match:
                matches += 1
            else:
                mismatches += 1

        print(f"Matches: {matches}, Mismatches: {mismatches}")
        return mismatches == 0

    def compare_records(self, record, type_):
        answers1 = self.resolve(self.resolver1, record, type_)
        answers2 = self.resolve(self.resolver2, record, type_)

        match = answers1 == answers2
        green_check = "\033[32m\u2713\033[0m"
        red_cross = "\033[31m\u2717\033[0m"
        print(f"Comparing records {record}({type_}): {green_check if match else red_cross}")
        print(f"\t1: {answers1}")
        print(f"\t2: {answers2}")
        return match

    def resolve(self, resolver, record, type_):
        try:
            answers = resolver.resolve(record, type_)
        except NoAnswer:
            answers = []
        return sorted([(d.rdtype, d.to_text()) for d in answers])


def compare():
    comparator = RecordComparator("1.1.1.1", "8.8.8.8")
    comparator.compare_all_records(
        [
            ("example.com", "A"),
            ("www.example.com", "CNAME"),
            ("www.microsoft.com", "A"),
            ("reddit.com", "A"),
            ("derp.reddit.com", "CNAME"),
        ]
    )


if __name__ == "__main__":
    compare()