protocol.py 文件源码

def decrypt(ciphertext: bytes, token: bytes) -> bytes:
        """Decrypt ciphertext with a given token.

        :param bytes ciphertext: Ciphertext to decrypt
        :param bytes token: Token to use
        :return: Decrypted bytes object"""
        if not isinstance(ciphertext, bytes):
            raise TypeError("ciphertext requires bytes")
        Utils.verify_token(token)
        key, iv = Utils.key_iv(token)
        cipher = Cipher(algorithms.AES(key), modes.CBC(iv),
                        backend=default_backend())

        decryptor = cipher.decryptor()
        padded_plaintext = decryptor.update(ciphertext) + decryptor.finalize()

        unpadder = padding.PKCS7(128).unpadder()
        unpadded_plaintext = unpadder.update(padded_plaintext)
        unpadded_plaintext += unpadder.finalize()
        return unpadded_plaintext