A simple knocking server

knocking.py

from bottle import route, run, template, error
import bottle
import subprocess
from random import random
from time import sleep

sequence = ['key1', 'key2', 'key3']
exclude = ['favicon.ico']
table = {}

def bingo(addr):
	print('accept', addr)
	# sudo iptables -I INPUT -p tcp --dport 33060 -s <addr> -j ACCEPT
	subprocess.run(['sudo', 'iptables', '-I', 'INPUT', '-p', 'tcp', '--dport', '33060', '-s', addr, '-j', 'ACCEPT'])

def delay():
  sleep(0.2 + 0.5 * random())
	
@error(404)
def notFound(error):
	return ''

@route('/<path>')
def knock(path):
  if path in exclude:
    return ''

  addr = bottle.request.remote_addr
  cnt = 0
  if addr in table:
    cnt = table[addr]

  ## increase count by 1 or reset
  if path == sequence[cnt]:
    table[addr] = cnt + 1

    ## pass whole sequence
    if table[addr] == len(sequence):
      bingo(addr)
      table.pop(addr, None)
      delay()
      return addr
  else:
    table.pop(addr, None)

	## add noise against timing attack and make attack longer 
  delay()
  return path

run(host='0.0.0.0', port=54321, reloader=False)