Decrypt and encrypt Flask session cookies

flask_cookie.py

import hashlib
from typing import Any, Dict

from flask.json.tag import TaggedJSONSerializer
from itsdangerous import URLSafeTimedSerializer


def _get_serializer(
    secret_key: str,
    salt="cookie-session",
    key_derivation="hmac",
    digest_method=hashlib.sha1,
):
    serializer = TaggedJSONSerializer()
    return URLSafeTimedSerializer(
        secret_key,
        salt=salt,
        serializer=serializer,
        signer_kwargs={
            "key_derivation": key_derivation,
            "digest_method": digest_method,
        },
    )


def decrypt_flask_cookie(secret_key: str, cookie_str: str) -> Dict[str, Any]:
    """
    Decrypt a Flask session cookie.
    """
    serializer = _get_serializer(secret_key)
    data = serializer.loads(cookie_str)
    assert type(data) is dict
    return data


def encrypt_flask_cookie(secret_key, data: Dict[str, Any]) -> str:
    """
    Encrypt a dictionary into a Flask session cookie.
    """
    serializer = _get_serializer(secret_key)
    cookie_str = serializer.dumps(data)
    assert type(cookie_str) is str
    return cookie_str