#!/usr/bin/env python2

import uuid
import hashlib
from xmlrpc.server import SimpleXMLRPCServer
from xmlrpc.server import SimpleXMLRPCRequestHandler

# Restrict to a particular path.
class RequestHandler(SimpleXMLRPCRequestHandler):
    rpc_paths = ('/RPC2',)

# Create server
server = SimpleXMLRPCServer(("localhost", 8000),
                            requestHandler=RequestHandler)
server.register_introspection_functions()


# Register an instance; all the methods of the instance are
# published as XML-RPC methods
class CHAP:
    test_password = 'Test123'
    # initializes class-instance and instance variables
    def __init__( self ):
        self.keys = {}
        self.authenticated = {}

    # tells the server to start the autentification process
    # and send the generated random salt
    def init( self ):
        session = str( uuid.uuid4() )
        key = str( uuid.uuid4() )
        while session in self.keys:
            session = str( uuid.uuid4() )

        self.keys[ session ] = key
        return [ session, key ]

    # checks if send hash is same as internally generated to validate if the correct
    # password was used
    def auth( self, session, password_hash ):
        if session in self.keys:
            combined = CHAP.test_password + self.keys[ session ]
            passhash = hashlib.sha256( combined.encode( 'utf-8' ) ).hexdigest()
            self.authenticated[ session ] = passhash == password_hash
            return self.authenticated[ session ] == True
        else:
            return False

    # adds functionality for users to log them selfes off, but also need the
    # the password_hash to ensure, that nobody else logs you off
    def logout( self, session, password_hash ):
        if self.auth( session, password_hash ):
            del self.authenticated[ session ]
            del self.keys[ session ]
        return self.authenticated.get( session ) != True

    # a little method that refuses to say hi, if you
    # are not authenticated
    def hello( self, session ):
        if ( self.authenticated.get( session ) == True ):
            return 'Hi, you are authenticated'
        else:
            return 'Sorry, please authenticate first'
server.register_instance(CHAP())
# Run the server's main loop
server.serve_forever()