decode_django_session.py

import base64
import zlib


def b64_decode(s):
    pad = b'=' * (-len(s) % 4)
    return base64.urlsafe_b64decode(s + pad)


def decode_session_data(session_data: str):
    session_data = session_data.encode()
    is_compressed = True if session_data.startswith(b'.') else False
    decoded_data = b64_decode(session_data[1:])
    if is_compressed:
        return zlib.decompress(decoded_data)
    return decoded_data


def test_decode_session_data():
    test_session_data = '.eJxVjkEOwiAQRe_CWpoCA-O404s0wxTSxgYTS1fGu0tNF7qcP__9vJcaeKvTsK3pOcyjuihAQuIImtiCBomoCa3ohBYsc4gmoTr9YpHlnsrO8rLscccij63U7ts53mt3bVcqdRau86PcDupvauJ12h2Ck8xifbBNxoyAeSQmIxYEjHcMzhN5Hykm7lvcnHwfzrlnzMROvT_zl0Tb:1lRz1Z:859enAty6xE12vX17o0fySraDDrP1fo2Sgu1lalUmN'
    expected_result = b'{"_auth_user_id":"47979ab4-9a24-4cb7-972c-e7242aa6b1e7","_auth_user_backend":"allauth.account.auth_backends.AuthenticationBackend","_auth_user_hash":"463cfac25629791d47fd9a91c24c4153a4359955b9bea01c21e75068f0a7f9a3"}'
    assert decode_session_data(test_session_data) == expected_result


test_decode_session_data()