Validates that each IPv4/IPv6 address has a valid reverse DNS (including forward DNS)

reverse_validator.py

#!/usr/bin/env python
import sys
from os.path import basename
from dns import resolver, reversename
import socket

def get_single_reverse(ip):
    rname = reversename.from_address(ip)
    try:
        responses = resolver.query(rname, "PTR")
    except:
        print "%s\tNo reverse DNS" % ip
        return None
    if len(responses) > 1:
        print "%s\tMultiple reverse DNS records" % ip
    else:
        return responses[0]
    return None

def compare_ip(family, string1, string2):
    a = socket.inet_pton(family, string1)
    b = socket.inet_pton(family, string2)
    return a == b

def check_forward(ip, rname):
    try:
        rname_aaaa  = resolver.query(rname, "AAAA")
    except:
        rname_aaaa = []
    try:
        rname_a     = resolver.query(rname, "A")
    except:
        rname_a = []
    if ':' in ip:
        if len(rname_aaaa) > 1:
            print "%s\tMultiple IPs for forward name %s" % (ip, rname)
        else:
            if len(rname_aaaa) == 0:
                print "%s\tForward name %s does not have an AAAA record" % (ip, rname)
            elif not compare_ip(socket.AF_INET6, ip, rname_aaaa[0].address):
                print "%s\tReverse name does not match forward name" % ip
            elif len(rname_a) != 0:
                print "%s\tIPv6 forward name %s has A records" % (ip, rname)
                for i in rname_a:
                    print " - %s" % i.address
            else:
                print "%s\tOK" % ip
    else:
        if len(rname_a) > 1:
            print "%s\tMultiple IPs for forward name %s" % (ip, rname)
        else:
            if not compare_ip(socket.AF_INET, ip, rname_a[0].address):
                print "%s\tReverse name does not match forward name" % (ip)
            elif len(rname_aaaa) != 0:
                print "%s\tIPv4 forward name has AAAA records"
            else:
                print "%s\tOK" % ip

def main():
    if len(sys.argv) != 2:
        print "Usage: %s <IP-list-file>" % basename(sys.argv[0])
        print
        print "File format: one IP per line, IPv4 or IPv6"
        sys.exit(1)

    ip_list = open(sys.argv[1], 'r').readlines()
    for ip in ip_list:
        ip = ip.strip()
        if ip == '':
            continue
        rname = get_single_reverse(ip)
        if rname:
            check_forward(ip, rname.target)

if __name__ == '__main__':
    main()