Using Flask-OAuthlib, how do I force Facebook to ask for account on reauthentication?

Question

I'm implementing authentication with OAuth 2 providers by Google and Facebook using Flask-OAuthlib package.

For Google, I'm using this:

google = oauth.remote_app(
    "google",
    consumer_key=client_id,
    consumer_secret=client_secret,
    request_token_params={"scope": "email"},
    base_url="https://www.googleapis.com/oauth2/v1/",
    request_token_url=None,
    access_token_method="POST",
    access_token_url="https://accounts.google.com/o/oauth2/token",
    authorize_url="https://accounts.google.com/o/oauth2/auth",
)

For Facebook, the code is similar:

facebook = oauth.remote_app(
    "facebook",
    consumer_key=client_id,
    consumer_secret=client_secret,
    request_token_params={"scope": "email"},
    base_url="https://graph.facebook.com/",
    request_token_url=None,
    access_token_method="GET",
    access_token_url="/oauth/access_token",
    authorize_url="https://www.facebook.com/dialog/oauth",
)

More complete examples are available here.

When using Google provider, I can successfully login, and once I logoff, when I try to login again, I'm redirected to Google's page which shows the list of accounts and let me chose one.

When using Facebook provider, I can successfully login, but once I logoff, when I login again, Facebook doesn't ask anything any longer, and simply logins me automatically with the previously used account.

How do I force Facebook to reauthenticate, i.e. show every time to the user the Facebook page which makes it possible to select a given account?

Answer 1

Found it.

The line:

request_token_params={"scope": "email"},

should be replaced by:

request_token_params={"scope": "email", "auth_type": "reauthenticate"},

In fact, according to the official documentation:

To re-authenticate, you can use these same steps with additional parameters to force it:

[...]

reauthenticate - asks the person to re-authenticate unconditionally