flask-oidc creates two JWS signers using the Flask se

Key reuse is potentially dangerous about flask-oidc HOT 3 CLOSED

puiterwijk commented on July 16, 2024 2

Key reuse is potentially dangerous

from flask-oidc.

Comments (3)

nelhage commented on July 16, 2024 1

Looking further, it looks like itsdangerous has a built-in solution for this: The salt parameter to signers

I believe you can just change the lines to

        self.extra_data_serializer = JSONWebSignatureSerializer(
            app.config['SECRET_KEY'], salt='flask-oidc-extra-data-serializer')
        self.cookie_serializer = TimedJSONWebSignatureSerializer(
            app.config['SECRET_KEY'], salt='flask-oidc-cookie-data-serializer')

I don't have time to test that change locally but I'll send a PR when I get a chance to.

from flask-oidc.

alex commented on July 16, 2024

FWIW, if you wanted to use pyca/cryptography to resolve this you could change these lines to:

self.extra_data_serializer = JSONWebSignatureSerializer(
    HKDF(
        algorithm=hashes.SHA256(),
        length=32,
        salt=None,
        info="extra-data-serializer",
        backend=default_backend(),
    ).derive(app.config['SECRET_KEY'])
)
 self.cookie_serializer = TimedJSONWebSignatureSerializer( 
    HKDF(
        algorithm=hashes.SHA256(),
        length=32,
        salt=None,
        info="cookie-serializer",
        backend=default_backend(),
    ).derive(app.config['SECRET_KEY'])
)