seg/trabalho4/service.py

from common import *
from AES import AESCipher
from random import randint
import socket
import os
import base64
import time

HOST = "127.0.0.1"
PORT = SERVICE_PORT

SERVICE_KEY = os.urandom(32)

def process_message(message):
    message = message.split("||")
    if message[0] == "getkey":
        return f"{base64.b64encode(SERVICE_KEY)}"
    if message[0] == "request":
        """
        T_c_s = {ID_C + T_A + K_c_s}K_s

        M5 = [{ID_C + T_A + S_R + N3}K_c_s + T_c_s]
        M6 = [{Resposta, N3}K_c_s]
        """
        body = message[1].split("<>")
        K_s = SERVICE_KEY
        T_c_s_AES = AESCipher(K_s)

        M5_inner = body[0]
        T_c_s = body[1]

        T_c_s = T_c_s_AES.decrypt(T_c_s)
        T_c_s = T_c_s.split("<>")
        ID_C = T_c_s[0]
        T_A = T_c_s[1]

        if int(T_A) < int(time.time()):
            print("Invalid ticket [expired]")
            return "Invalid ticket [expired]"

        K_c_s = eval(T_c_s[2])

        M5_inner_AES = AESCipher(K_c_s)
        M5_inner = M5_inner_AES.decrypt(M5_inner)
        M5_inner = M5_inner.split("<>")
        ID_S = M5_inner[2]
        N3 = M5_inner[3]

        # generate M6
        message = "OPEN"
        M6_inner = f"{message}<>{N3}"
        M6_inner_AES = AESCipher(K_c_s)
        M6_inner = M6_inner_AES.encrypt(M6_inner)

        print("Sending M6", f"[{message}<>{N3}]")

        M6 = f"{M6_inner}"
        return M6

def main():
    with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
        s.bind((HOST, PORT))
        s.listen()
        while True:
            conn, addr = s.accept()
            with conn:
                all_data = ""
                data = conn.recv(4096)
                all_data += data.decode()

                response = process_message(all_data)

                conn.sendall(response.encode())

if __name__ == "__main__":
    main()