[OpenID] What about Logout?

Peter Williams pwilliams at rapattoni.com
Wed Apr 8 15:08:31 UTC 2009

In our environment, a user typically has several SSO sessions open at several RPs, each operating in different (sub) domains. Some subset of them (called them RP1  and RP2) may be sharing session management with Facebook - the OP.

We have been told numerous times by folks in control of their business rules that any decision to logout the user from one RP1 MUST not log the user out of RP2. Assuming RP1 and RP2 are both talking to Facebook OP, RP2 must be able to continue to use its association to the OP after a logout exchange between RP1/OP, without the user having to re-authenticate (create a new IDP session).

From: general-bounces at openid.net [mailto:general-bounces at openid.net] On Behalf Of Luke Shepard
Sent: Wednesday, April 08, 2009 7:39 AM
To: Santosh Rajan; general at openid.net
Subject: Re: [OpenID] What about Logout?

I agree, logout seems to be more and more important for a full single sign-on / sign-out experience. We found with Facebook Connect that we had to offer RPs the ability to log the user out of Facebook, for consistency.

Consider this: the user goes to the RP, clicks the "login" button, and then a popup comes up onto their OP. The user happily enters their credentials, popup closes, and they're in. Great! Then they hit "logout" on the site they're on, and go on their way. But if this is a shared terminal, then they still have a cookie onto their OP, which leaves them exposed. A better solution would be to let the RP log them out of their provider.

There are workarounds, some of which were suggested by Allen in previous threads - for instance, having a short cookie timeout, trying to detect recent activity, etc, but none are quite as clean as a solid logout trick.

I think it would be relatively easy to add to the next spec. We could add an additional mode or two - say, "logout_setup" or "logout_immediate". They would be behave the same as checkid_immediate and checkid_setup, except in reverse - the RP must supply the correct user credentials, and the OP can then log them out and return only "success" or "failure".

On 4/8/09 7:05 AM, "Santosh Rajan" <santrajan at gmail.com> wrote:

If an RP wants to logout the user not only from his site, but also from the
OP, there is no easy way for him to do it. Currently it is a pain. He needs
to figure how to log out from each OP himself, while most OP's havent even
documented this.
Eg. This is the Google Logout URL.
This is Yahoo's undocumented Logout URL.

Maybe we need to address this in 2.1? Like the OP may provide the Logout URL
in the discovery itself along with the endpoint URL?
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