#!/usr/bin/env fail2ban-python
# Inspired by https://isc.sans.edu/forums/diary/When+Google+isnt+Google/15968/
#
# Written in Python to reuse built-in Python batteries and not depend on
# presence of host and cut commands
#
import sys
from fail2ban.server.ipdns import DNSUtils, IPAddr
from threading import Thread

def process_args(argv):
    if len(argv) - 1 not in (1, 2):
       raise ValueError("Usage %s ip ?timeout?. Got: %s\n"
                        % (argv[0], argv[1:]))
    ip = argv[1]

    if not IPAddr(ip).isValid:
       raise ValueError("Argument must be a single valid IP. Got: %s\n"
                        % ip)
    return argv[1:]

google_ips = None

def is_googlebot(ip, timeout=55):
    import re

    timeout = float(timeout or 0)
    if timeout:
      def ipToNameTO(host, ip, timeout):
        host[0] = DNSUtils.ipToName(ip)
      host = [None]
      th = Thread(target=ipToNameTO, args=(host, ip, timeout)); th.daemon=True; th.start()
      th.join(timeout)
      host = host[0]
    else:
      host = DNSUtils.ipToName(ip)

    if not host or not re.match(r'.*\.google(bot)?\.com$', host):
       return False
    host_ips = DNSUtils.dnsToIp(host)
    return (ip in host_ips)

if __name__ == '__main__': # pragma: no cover
    try:
      ret = is_googlebot(*process_args(sys.argv))
    except ValueError as e:
      sys.stderr.write(str(e))
      sys.exit(2)
    sys.exit(0 if ret else 1)