doorstatus/statusd.py

#!/usr/bin/python3

# file: statusd.py
# date: 26.07.2019
# email: berhsi@web.de

# server, who listen for ipv4 connections at port 10001. now with ssl
# encrypted connection and client side authentication.

import socket
import ssl
import os
import logging
from time import time, ctime, sleep
from sys import exit, byteorder


def read_config(CONFIGFILE, CONFIG):
    '''
    reads the given config file and sets the values are founded.
    param 1: string
    param 2: dictionary
    return: boolean
    '''
    logging.debug('Read configfile {}'.format(CONFIGFILE))
    if os.access(CONFIGFILE, os.R_OK):
        logging.debug('Configfile is readable')
        with open(CONFIGFILE, 'r') as config:
            logging.debug('Configfile successfull read')
            for line in config.readlines():
                if not line[0] in ('#', ';', '\n', '\r'):
                    key, value = (line.strip().split('='))
                    key = strip_argument(key).upper()
                    value = strip_argument(value)
                    CONFIG[key] = value
                    logging.debug('Set {} to {}'.format(key, value))
    else:
        logging.error('Failed to read {}'.format(CONFIGFILE))
        logging.error('Using default values')
        return False
    return True


def certs_readable(config):
    '''
    checks at start, if the needed certificates defined (no nullstring) and readable.
    param 1: dictionary
    return: boolean
    '''
    for i in (config['SERVER_KEY'], config['SERVER_CERT'], config['CLIENT_CERT']):
        if  i == '' or os.access(i, os.R_OK) == False:
            logging.error('Cant read {}'.format(i))
            return False
    return True


def strip_argument(argument):
    '''
    Becomes a string and strips at first whitespaces, second apostrops and
    returns the clear string.
    param 1: string
    return: string
    '''
    argument = argument.strip()
    argument = argument.strip('"')
    argument = argument.strip("'")
    return argument


def print_config(CONFIG):
    '''
    Prints the used configuration, if loglevel ist debug.
    param 1: dictionary
    return: boolean (allways true)
    '''
    logging.debug('Using config:')
    for i in CONFIG.keys():
        logging.debug('{}: {}'.format(i, CONFIG[i]))
    return True


def display_peercert(cert):
    for i in cert.keys():
        print(i)
        for j in cert[i]:
            print('\t{}'.format(j))
    return


def receive_buffer_is_valid(raw_data):
    '''
    checks, if the received buffer from the connection is valid or not.
    param 1: byte
    return: boolean
    '''
    if raw_data == b'\x00' or raw_data == b'\x01':
        logging.debug('Argument is valid: {}'.format(raw_data))
        return True
    else:
        logging.debug('Argument is not valid: {}'.format(raw_data))
        return False


def replace_entry(line, new):
    '''
    The function becomes two strings and replaces the second part of the
    first string from ":" until end with the second string. Than appends a
    "," and returns the result.

    !!! Todo: needs exception handling !!!

    param 1: string
    param 2: string
    return: string
    '''
    array = line.split(':')
    logging.debug('Replace {} with {}'.format(array[1], new))
    array[1] = ''.join((new, ','))
    line = ':'.join((array[0], array[1]))
    return line


def change_status(raw_data, api):
    '''
    Becomes the received byte and the path to API file. Grabs the content of
    the API with read_api() and replaces "open" and "lastchange". Write all
    lines back to API file.
    param 1: byte
    param 2: string
    return: boolean
    '''
    edit = False

    logging.debug('Change status API')
    data = read_api(api)
    if data != False:
        status, timestamp = set_values(raw_data)
        if os.access(api, os.W_OK):
            logging.debug('API file is writable')
            with open(api, 'w') as api_file:
                logging.debug('API file open successfull')
                for line in data.splitlines():
                    if line.strip().startswith('"state":'):
                        edit = True
                    elif edit == True and line.strip().startswith('"open":'):
                        line = replace_entry(line, status)
                    elif edit == True and line.strip().startswith('"lastchange":'):
                        line = replace_entry(line, timestamp)
                        edit = False
                    try:
                        api_file.write(line)
                        api_file.write('\n')
                    except Exception as e:
                        logging.error('Failed to write line to API file')
                        logging.error('Line: {}'.format(line))
                        logging.error('{}'.format(e))
                logging.debug('API file changed')
        else:
            logging.error('API file is not writable. Wrong permissions?')
            return False
        logging.info('Status successfull changed to {}'.format(status))
        return True
    return False


def read_api(api):
    '''
    Reads the API file in an buffer und returns the buffer. If anything goes
    wrong, it returns False - otherwise it returns the buffer.
    param 1: string
    return: string or boolean
    '''
    logging.debug('Open API file: {}'.format(api))
    if os.access(api, os.R_OK):
       logging.debug('API is readable')
       with open(api, 'r') as api_file:
           logging.debug('API opened successfull')
           try:
              api_data = api_file.read()
              logging.debug('API read successfull')
           except Exception as e:
               logging.error('Failed to read API file(): {}'.format(e))
               return False
       return (api_data)
    logging.error('Failed to read API file')
    return False
    

def set_values(raw_data):
    '''
    Create a timestamp, changes the value of the given byte into a string
    and returns both.
    param 1: byte
    return: tuple
    '''
    timestamp = str(time()).split('.')[0]
    if raw_data == 'b\x01':
        status = "true"
    else:
        status = "false"
    return (status, timestamp)


def main():
    '''
    The main function - opens a socket, create a ssl context, load certs and
    listen for connections. at ssl context we set some security options like 
    OP_NO_SSLv2 (SSLv3): they are insecure
    PROTOCOL_TLS: only use tls
    OP_NO_COMPRESSION: prevention against crime attack
    OP_DONT_ISERT_EMPTY_FRAGMENTS: prevention agains cbc 4 attack (cve-2011-3389)

    '''
    CONFIG = {
        'HOST': 'localhost',
        'PORT': 10001,
        'SERVER_CERT': './server.crt',
        'SERVER_KEY' : './server.key',
        'CLIENT_CERT': './client.crt',
        'TIMEOUT': 3.0,
        'API': './api',
        'API_TEMPLATE': './api_template',
        'VERBOSITY': 'info'
        }
    CONFIG_FILE = './statusd.conf'
    FINGERPRINT = \
    '35:8E:35:FA:58:0A:DD:2B:C8:6A:F9:EA:A3:7B:10:F5:62:89:AB:D0:AB:53:3E:B5:8B:AB:E1:23:CF:93:F5:F9'

    loglevel = logging.DEBUG
    logging.basicConfig(format='%(levelname)s: %(message)s', level=loglevel)
    read_config(CONFIG_FILE, CONFIG)
    print_config(CONFIG)

    if certs_readable(CONFIG) == False:
        logging.error('Cert check failed\nExit')
        exit()

    context = ssl.create_default_context(ssl.Purpose.CLIENT_AUTH)
    context.options &= ~ssl.OP_NO_SSLv2
    context.options &= ~ssl.OP_NO_SSLv3
    context.options &= ~ssl.PROTOCOL_TLS
    context.options &= ~ssl.OP_CIPHER_SERVER_PREFERENCE
    # context.options &= ~ssl.OP_DONT_INSERT_EMPTY_FRAGMENTS
    context.options |= getattr(ssl._ssl, 'OP_NO_COMPRESSION', 0)
    # context.set_ciphers('HIGHT:!aNULL:!RC4:!DSS')
    context.verify_mode = ssl.CERT_REQUIRED
    context.load_cert_chain(certfile = CONFIG['SERVER_CERT'],
                            keyfile = CONFIG['SERVER_KEY'])
    context.load_verify_locations(cafile = CONFIG['CLIENT_CERT'])
    logging.debug('SSL context created')

    with socket.socket(socket.AF_INET, socket.SOCK_STREAM, 0) as mySocket:
        logging.debug('Socket created')
        try:
            mySocket.bind((CONFIG['HOST'], int(CONFIG['PORT'])))
            mySocket.listen(5)
            logging.info('Listen on {} at Port {}'.format(CONFIG['HOST'], CONFIG['PORT']))
        except Exception as e:
            logging.error('unable to bind and listen')
            logging.error('{}'.format(e))
            exit()
        while True:
            try:
                fromSocket, fromAddr = mySocket.accept()
                logging.info('Client connected: {}:{}'.format(fromAddr[0], fromAddr[1]))
                try:
                    fromSocket.settimeout(float(CONFIG['TIMEOUT']))
                    logging.debug('Connection timeout set to {}'.format(CONFIG['TIMEOUT']))
                except Exception as e:
                    logging.error('Canot set timeout to {}'.format(CONFIG['TIMEOUT']))
                    logging.error('Use default value: 3.0')
                    fromSocket.settimeout(3.0)
                try:
                    conn = context.wrap_socket(fromSocket, server_side = True)
                    # display_peercert(conn.getpeercert())
                    logging.debug('SSL established. Peer: {}'.format(conn.getpeercert()))
                except Exception as e:
                    logging.error('SSL handshake failed: {}'.format(e))
                raw_data = conn.recv(1)
                if receive_buffer_is_valid(raw_data) == True:
                    if change_status(raw_data, CONFIG['API']) == True:
                        logging.debug('Send {} back'.format(raw_data))
                        conn.send(raw_data)
                    # change_status returns false:
                    else:
                        logging.info('Failed to change status')
                        if conn:
                            conn.send(b'\x03')
                # recive_handle returns false:
                else:
                    logging.info('Inalid argument recived: {}'.format(raw_data))
                    logging.debug('Send {} back'.format(b'\x03'))
                    if conn:
                        conn.send(b'\x03')
                sleep(0.1) # protection against dos
            except KeyboardInterrupt:
                print('\rExit')
                logging.info('Exit')
                exit()
            except Exception as e:
                logging.error('{}'.format(e))
                continue
    return 0


if __name__ == '__main__':
    main()