padding.py 文件源码

def finalize(self):
        if self._buffer is None:
            raise AlreadyFinalized("Context was already finalized.")

        if len(self._buffer) != self.block_size // 8:
            raise ValueError("Invalid padding bytes.")

        valid = _lib.Cryptography_check_pkcs7_padding(
            self._buffer, self.block_size // 8
        )

        if not valid:
            raise ValueError("Invalid padding bytes.")

        pad_size = six.indexbytes(self._buffer, -1)
        res = self._buffer[:-pad_size]
        self._buffer = None
        return res