#!/usr/bin/env python3
# -*- coding: utf-8 -*-
import os
from pathlib import Path
from Crypto.Cipher import PKCS1_OAEP    
from Crypto.PublicKey import RSA
from base64 import b64encode, b64decode
import argparse

def decrypt_symmetric_key(encrypted_key, private_key_path="id_rsa"):
    """
    Decrypts the symmetric key using the provided private key.
    
    :param encrypted_key_path: Path to the file containing the encrypted symmetric key.
    :param private_key_path: Path to the private RSA key file.
    :return: Decrypted symmetric key or None if decryption fails.
    """
    try:
        with open(private_key_path, "rb") as private_key_file:
            private_key = RSA.import_key(private_key_file.read())
        cipher_rsa = PKCS1_OAEP.new(private_key)
        
        encrypted_symmetric_key = encrypted_key.encode('utf-8') if isinstance(encrypted_key, str) else encrypted_key
        
        symmetric_key = cipher_rsa.decrypt(b64decode(encrypted_symmetric_key))
        return symmetric_key
    except Exception as e:
        print(f"Error decrypting symmetric key: {e}")
        return None

def main():
    parser = argparse.ArgumentParser(description="Decrypt a symmetric key using a private RSA key.")
    parser.add_argument("encrypted_key", type=str, help="Encrypted symmetric key")
    parser.add_argument("--private_key", type=str, default="id_rsa", help="Path to the private RSA key file (default: id_rsa)")
    args = parser.parse_args()

    symmetric_key = decrypt_symmetric_key(args.encrypted_key, args.private_key)
    if symmetric_key:
        print(symmetric_key.decode('utf-8') if isinstance(symmetric_key, bytes) else symmetric_key)
    else:
        print("Failed to decrypt the symmetric key.")   

if __name__ == "__main__":
    main()