server/server/netwrapper.py

#!/usr/bin/env python3
import json
from base64 import b64encode, b64decode
import pyDH
from Crypto.Cipher import PKCS1_OAEP
from Crypto.PublicKey import RSA
from Crypto.Cipher import ChaCha20
from Crypto.PublicKey.RSA import RsaKey
from Crypto.Random import get_random_bytes

from netsim import network_interface
from server.server import Server


class NetWrapper:

    def __init__(self, clientPublicKey: dict, serverPrivateKey: RsaKey, serverInstance: Server):
        self.clientPublicKey = clientPublicKey
        self.currentClientPublicKey = "".encode('UTF-8')
        self.serverPrivateKey = serverPrivateKey
        self.cipherkey = "".encode('UTF-8')
        self.network = network_interface('./', 'A')
        self.clientAddr = ""
        self.currentUser = ""
        self.serverInstance = serverInstance

    def serverIdentify(self, msg: bytes) -> None:
        incommingJson = json.loads(msg.decode('UTF-8'))
        if incommingJson['type'] != "IDY":
            raise Exception('Wrong message type encountered')
        self.clientAddr = incommingJson['source']
        self.currentUser = incommingJson['username']
        self.currentClientPublicKey = self.clientPublicKey[self.currentUser]
        cipher_rsa = PKCS1_OAEP.new(self.serverPrivateKey)
        retmsg = cipher_rsa.decrypt(b64decode(incommingJson['message'])).decode('UTF-8')
        cipher = PKCS1_OAEP.new(self.currentClientPublicKey)
        identMsg = json.dumps(
            {'type': 'IDY', 'source': self.network.own_addr,
             'message': b64encode(cipher.encrypt(retmsg.encode('UTF-8')))}).decode(
            'ASCII')
        self.network.send_msg(self.clientAddr, identMsg)

    def sendMessage(self, message: bytes) -> None:
        cipher = ChaCha20.new(self.cipherkey, get_random_bytes(12))
        ciphertext = cipher.encrypt(message)
        nonce = b64encode(cipher.nonce).decode('ASCII')
        ct = b64encode(ciphertext).decode('ASCII')
        sendjson = json.dumps({'type': 'CMD', 'source': self.network.own_addr, 'nonce': nonce, 'message': ct}).encode(
            'UTF-8')
        self.network.send_msg(self.clientAddr, sendjson)

    def keyExchange(self) -> None:
        dh = pyDH.DiffieHellman()
        cipher = PKCS1_OAEP.new(self.currentClientPublicKey)
        mypubkey = b64encode(cipher.encrypt(str(dh.gen_public_key()).encode('UTF-8'))).decode('ASCII')
        jsonmsg = json.dumps({'type': 'DH', 'source': self.network.own_addr, 'message': mypubkey}).encode('UTF-8')
        self.network.send_msg(self.clientAddr, jsonmsg)
        decodedmsg = {'source': '', 'type': ''}
        while not (decodedmsg['source'] == self.clientAddr and decodedmsg['type'] == 'DH'):
            status, msg = self.network.receive_msg(blocking=True)
            if not status:
                raise Exception('Network error during connection.')
            decodedmsg = json.loads(msg.decode('UTF-8'))
        cipher_rsa = PKCS1_OAEP.new(self.serverPrivateKey)
        serverpubkey = int(cipher_rsa.decrypt(b64decode(decodedmsg['message'])).decode('UTF-8'))
        self.cipherkey = dh.gen_shared_key(serverpubkey).encode('UTF-8')

    def login(self) -> bool:
        b64 = {'source': '', 'type': ''}
        while not (b64['source'] == self.clientAddr and b64['type'] == 'AUT'):
            status, msg = self.network.receive_msg(blocking=True)
            if not status:
                raise Exception('Network error during connection.')
            b64 = json.loads(msg.decode('UTF-8'))
        try:
            retnonce = b64decode(b64['nonce'])
            retciphertext = b64decode(b64['message'])
            retcipher = ChaCha20.new(self.cipherkey, nonce=retnonce)
            plaintext = retcipher.decrypt(retciphertext).decode('UTF-8').split(' ')
            linsuccess = (not (len(plaintext) != 3 or plaintext[0] != "LIN" or plaintext[
                1] != self.currentUser)) and self.serverInstance.login(plaintext[1], plaintext[2])
            if linsuccess:
                message = "OK".encode('UTF-8')
            else:
                message = "ERROR".encode('UTF-8')
            cipher = ChaCha20.new(self.cipherkey, get_random_bytes(12))
            ciphertext = cipher.encrypt(message)
            nonce = b64encode(cipher.nonce).decode('ASCII')
            ct = b64encode(ciphertext).decode('ASCII')
            sendjson = json.dumps(
                {'type': 'AUT', 'source': self.network.own_addr, 'nonce': nonce, 'message': ct}).encode(
                'UTF-8')
            self.network.send_msg(self.clientAddr, sendjson)
            return linsuccess
        except Exception:
            print("Incorrect decryption")

    def initClientConnection(self, msg: bytes) -> bytes:
        try:
            self.serverIdentify(msg)
            self.keyExchange()
            success = self.login()
            if success:
                return "LINOK".encode('UTF-8')
            else:
                self.logout()
                return "LINERROR".encode('UTF-8')
        except Exception:
            self.logout()
            return "LINERROR".encode('UTF-8')

    def recieveMessage(self) -> bytes:
        status, msg = self.network.receive_msg(blocking=True)
        if not status:
            raise Exception('Network error during connection.')
        if not self.clientAddr:
            return self.initClientConnection(msg)
        else:
            return self.recieveEncryptedMessage(msg)

    def logout(self) -> None:
        self.serverInstance.logout()
        self.clientAddr = ""
        self.cipherkey = "".encode('UTF-8')
        self.currentClientPublicKey = "".encode('UTF-8')
        self.currentUser = ""

    def recieveEncryptedMessage(self, msg: bytes) -> bytes:
        try:
            b64 = json.loads(msg)
            retnonce = b64decode(b64['nonce'])
            retciphertext = b64decode(b64['message'])
            retcipher = ChaCha20.new(self.cipherkey, nonce=retnonce)
            plaintext = retcipher.decrypt(retciphertext)
            return plaintext
        except Exception:
            print("Incorrect decryption")