SFAuthenticationSession/ASWebAuthenticationSession and logging out

Question

I'm planning to switch an app from the old OAuth flow with the SFSafariViewController to the new flow with iOS 11's SFAuthenticationSession. Logging in isn't an issue, the transfer to the new API took me a few minutes to implement. However logging out has me baffled.

How?

I can't find any mentioning of wanting to offer the option of logging out anywhere in the docs. Using the old SFSafariViewController to invalidate the cookies? Nope, they're not shared anymore with SFAuthenticationSession. As soon as I restart the authentication session the user get's logged in automatically and there's no way out. So how to enable logging out? Or am I simply overlooking something completely obvious?

Update: I found a "way that works" in a technical sense, but it's bonkers for the user: Open a new SFAuthenticationSession on the logout page that clears the cookie. But that means when logging out the alert view asks the user again whether he'd like to log in via the service. If yes is selected ("logging in"), the cookie clearing logout page is opened, the user has to manually dismiss the view, which can be caught by the completion handler and we know we can open the login view again.. displaying the login prompt to log out? I really don't like this solution.

Any ideas? Am I still overlooking a completely obvious solution?

Update 2: As no one has any clue about this issue so far, this is probably not an easy one. I have filed a suggestion with Apple via their report tool to either clarify how to handle this or build it into the API if not available. Will post if I get an answer.

Update 3: After pondering the issue a bit more we found another possible (although also unattractive) solution if you can influence the login page of the OAuth provider: make cookies very short lived. Then the login page can be opened without automatic log in. However this kills the whole purpose of sharing login sessions between apps.. and you need to be able to influence the login page.

Update 4: Since iOS 12 SFAuthenticationSession is deprecated and got replaced by ASWebAuthenticationSession. However ASWebAuthenticationSession does not change anything in regard to logging out. It's still not possible. Same issue as before.

Answer 1

Update November 2020: We used @react-native-community/cookies to clear cookies as a workaround. See the snipped below as an example.

import CookieManager from '@react-native-community/cookies';

CookieManager.clearAll().catch(e => alert("Error deleting cookies during logout"))

Previous answer from April 2020. This may be helpful for anybody struggling with this. I've spent few hours testing different options, going through apps and looking how they do it and reading forums/discussions.

1. I haven't find a way to programatically clear cookies and there is no documentation on Apple on this.
2. Using FB as an example. Logging out from Safari and deleting FB app doesn't help. Any app which is downloaded will not ask for login to FB if you logged in once before through ASWebAuthenticationSession or SFAuthenticationSession.
3. If users ask how to force login (even though it's not your problem as a developer) you can point them to: Settings -> Safari -> Advanced -> Website Data -> Remove All Website Data (or just the ones for the provider).
4. If your use case needs switching of users (like in my case where we use Azure AD and users share 1 phone) you have 2 options. A) Open ASWebAuthenticationSession with the logout endpoint (as mentioned, this is very weird UX). B) Open Safari as a separate app (not inside yours) and do login/logout there. Unfortunately, there is no way to redirect the user to your app after logout if the OAuth provider doesn't support redirect on logout.

It sucks because this prevents developers from creating nice experiences on iOS for use cases where a business needs to share device between multiple users and OAuth is used as identity provider.