[Openid-specs-ab] [External Sender] Re: OIDC Session Management and third party cookie blocking

Fri Sep 2 18:58:35 UTC 2022

What happens and what should happen are very dependent on the use case so
this might not address your questions specifically.

Generally, a session represents an authentication performed in a single
application (e.g. browser instance). So the user could be logged into the
same browser across multiple tabs and each tab could represent a different
relying party. When the user logs out, generally the user wants all the
tabs to know that they are no longer logged in.

Now if each tab was a SPA and only checking the session state by calling a
backend service, then the SPA won’t know that the user has logged out until
the backend call is made. Note that the OpenID Connect session management
spec allows a SPA running in a tab to know much more quickly via embedded
iframes and postMessage() (though some of that functionality no longer
works with the browsers move to disable 3rd party cookies).

The only risk to the SPA continuing in a logged in state is if the user has
“logged out” and left the device and the SPA continues to think the user is
logged in, then it’s possible someone else could get access to the personal
information being displayed by the SPA. Whether this is a risk for your use
case or not may vary.

One final thought about “who’s computer is it”? In most cases it will be
the owners computer and the risk is low. However, in some cases (especially
for SPAs) the computer could be in a library or other public place in which
case it’s not the user’s computer.

Hope that helps:)
George

On Fri, Sep 2, 2022 at 11:19 AM Tom Jones via Openid-specs-ab <
openid-specs-ab at lists.openid.net> wrote:

> what's the threat from the spa (aka pwa) running on w/o knowing that the
> session is no longer active?
> Who is it that cares until the app tries to access a remote resource?
> Please don't tell me that the app should not be allowed to access a local
> resource on the computer!  Who's computer is it exactly?
>
> Be the change you want to see in the world ..tom
>
>
> On Thu, Sep 1, 2022 at 6:48 PM Vittorio Bertocci via Openid-specs-ab <
> openid-specs-ab at lists.openid.net> wrote:
>
>> I am not sure there's the need to introduce new endpoints and grants for
>> this.
>> The scenario initially identified is the pure SPA, where the app cannot
>> rely on a backend component. The main primitive is an affordance for the
>> app to verify whether there's still an active OP session, eg no other RP
>> participating in the OP session triggered a sign out.
>> You can easily obtain that affordance by implementing session bound
>> refresh tokens. If your refresh tokens are session bound, attempts to use
>> them when the session is no more will fail. Simple. Existing endpoints,
>> artifacts, grants.
>> If your refresh tokens are meant to be used with a SPA, their lifetime
>> should have an upper bound tied to the session anyway - SPA SDKs
>> implementing the code grant routinely drop from whatever local cache they
>> maintain access and refresh tokens upon their own sign out, hence having
>> refresh tokens surviving that is a security hindrance anyway. In fact, some
>> vendors even require calling their token revocation APIs on logout (which
>> wouldn't be necessary if their refresh and access tokens would
>> automatically be invalidated when the session it originated them
>> terminates).
>> One of the challenges of the above (already discussed on this list a
>> while ago) is that although it is a perfectly legitimate behavior for  the
>> authorization server, we have no interoperable way to request it. In fact,
>> the only affordance ever offered to request a refresh token is the famous
>> "offline_access" scope, that does the exact opposite (refresh tokens are
>> now guaranteed to be decoupled from the session) and many providers use
>> that scope as the ONLY way to cause their authorization server to issue
>> refresh tokens, which complicates things. Even ignoring that, basically the
>> behavior of refresh tokens is at complete discretion of the authorization
>> server hence today there's no way to know whether the refresh token as
>> check session trick will work.
>> At Okta we implemented "online_access", a scope that causes our
>> authorization server to issue refresh tokens that will automatically become
>> invalid when the corresponding OP session is terminated (eg because of a
>> logout). Few years ago we suggested standardizing it, but there was
>> pushback on the account that "offline_access was a mistake hence adding
>> online_access would be doubling down", if I remember correctly. If the
>> browser crisis is making people reconsider, there should still be the draft
>> somewhere :-)
>>
>> On the inactivity timeout. One thing that gets lost with using RTs rather
>> than iframe tricks for session renewal is that RTs no longer "touch" the
>> authorization endpoint, hence cannot extend the life of session cookies
>> with sliding expiration settings. This isn't a trivial problem: whether one
>> uses the token endpoint as I described here or a new backend (eg nonbrowser
>> UX) endpoint, allowing a backend operation to affect a front channel
>> session would mix two completely different threat models, and throw away
>> all the protective measures we already have in place on the authorization
>> endpoint (eg anomaly detection based on signal entropy of the front
>> channel). I don't think we can safely get back session extension
>> functionality without first getting some mechanism to prove that calls to
>> the token endpoint are coming from the same user agent that benefited from
>> the initial session setting top level redirects. Sender constraint of some
>> form, perhaps.
>>
>>
>> On Tue, Aug 30, 2022 at 6:13 PM Jake Feasel via Openid-specs-ab <
>> openid-specs-ab at lists.openid.net> wrote:
>>
>>> *This message originated outside your organization.*
>>>
>>> ------------------------------
>>>
>>> While this concern is important, if we follow it through completely it
>>> kills the entire auth code grant for the same reasons. Looking at it from
>>> the browser point-of-view, the auth code grant is just some redirection
>>> across domains involving the transmission of an opaque "code" generated by
>>> the OP back to the RP, followed by an additional call from the RP to the OP
>>> passing it back; who is to say that this code isn't used for tracking users
>>> across sites?
>>>
>>> "The browser people don’t seem to care about that at the moment." -
>>> There is a good reason why the privacy-conscious should not be opposed to
>>> this general technique (both the auth code and the proposed session check
>>> grants). Both grants can only work in a third-party cookie blocking
>>> environment if the browser is redirected through the OP at the top-level
>>> (i.e. as a first party interaction). I believe this is the critical point
>>> that shifts the usage from "nefarious" to "legitimate".
>>>
>>> Put another way - if a privacy-abusing marketing company wanted to try
>>> to copy this pattern for their own nefarious purposes, they would have to
>>> require every page they advertise on to have a top-level redirect for all
>>> visitors through their own domain and back again (passing the requisite
>>> tracking id back in the URL). I feel like this extremely obtrusive pattern
>>> would not be acceptable for most pages that just want to show ads - it's
>>> only acceptable in the case of authentication because the site and the user
>>> have very tangible benefits from the interruption in flow associated with
>>> logging in.
>>>
>>> I think we are on safe ground here, in terms of what patterns are likely
>>> to be shut down in the future. As such I would like to continue with this
>>> "session_check" grant proposal.
>>>
>>> Thanks
>>>
>>>
>>>
>>> On Wed, Aug 10, 2022 at 3:25 AM Mischa Salle via Openid-specs-ab <
>>> openid-specs-ab at lists.openid.net> wrote:
>>>
>>>> On Tue, Aug 09, 2022 at 06:39:27PM +0000, Nicole Roy via
>>>> Openid-specs-ab wrote:
>>>> > My concern would be that a browser employing “Intelligent Tracking
>>>> Prevention” would see the POST of the SID as tracking and prevent it. Of
>>>> course, doing so breaks all sorts of other things, but the browser people
>>>> don’t seem to care about that at the moment.
>>>>
>>>> probably would have the same problems with "nonce" and "state" then?
>>>> Plus makes one wonder whether these three could not have been a single
>>>> parameter?
>>>>
>>>> Mischa
>>>>
>>>> > > On Aug 2, 2022, at 4:30 PM, Jake Feasel via Openid-specs-ab <
>>>> openid-specs-ab at lists.openid.net> wrote:
>>>> > >
>>>> > > This topic has been raised before, but based on the traffic from
>>>> this list it seems to not be going anywhere. I would like to revive it.
>>>> > >
>>>> > > I had a quick talk at Identiverse this year covering the OIDC
>>>> Session Management draft spec, in particular my take on the upcoming
>>>> "Cookiepocalypse" and how it will render the current draft completely
>>>> obsolete. You can see my slides here:
>>>> https://docs.google.com/presentation/d/1uU3KvK6ayTpjB2OEmrSqQnUdJDPSdfxxetJrks1czvI/edit#slide=id.g11aa5093f19_0_63
>>>> <
>>>> https://docs.google.com/presentation/d/1uU3KvK6ayTpjB2OEmrSqQnUdJDPSdfxxetJrks1czvI/edit#slide=id.g11aa5093f19_0_63
>>>> >
>>>> > >
>>>> >
>>>> > [snip]
>>>> >
>>>> > > The OP will include the "sid" claim (as defined in the Front and
>>>> Back-channel logout drafts) as a claim in the id_token used in an auth_code
>>>> grant. This "sid" value will be included in a POST request to the "token"
>>>> endpoint on the OP on a periodic basis (likely prompted from user activity
>>>> within the RP). It would like something like so (note the absence of a
>>>> cookie in this request):
>>>> > >
>>>> > >   POST /token HTTP/1.1
>>>> > >   Host: server.example.com
>>>> <https://urldefense.com/v3/__http://server.example.com__;!!PwKahg!-sNCnmvAkBWaB80MnJiytMhdTvP9mHClc2CeSSyiYIOENf4mecfQl_wKoHP_uR0dlBcwvqmjJb3Bahnn0_uXULQ7mR5vWQ$>
>>>> <http://server.example.com/
>>>> <https://urldefense.com/v3/__http://server.example.com/__;!!PwKahg!-sNCnmvAkBWaB80MnJiytMhdTvP9mHClc2CeSSyiYIOENf4mecfQl_wKoHP_uR0dlBcwvqmjJb3Bahnn0_uXULSFUiVTrA$>
>>>> >
>>>> > >   Content-Type: application/x-www-form-urlencoded
>>>> > >   Authorization: Basic czZCaGRSa3F0MzpnWDFmQmF0M2JW
>>>> > >
>>>> > >   grant_type=session_check&sid=1234xyz
>>>> > >
>>>> > > The response code from this could be a 401 if the sid is not
>>>> associated with a valid OP session, or 200 if it is. The response body in
>>>> the case of a 200 could include a new id_token with updated session claims
>>>> (to provide better context for when the session expires or if other
>>>> important details about the session change).
>>>> > >
>>>> >
>>>> > [snip]
>>>> >
>>>>
>>>>
>>>>
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>>>>
>>>>
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George Fletcher (he/him)

Executive Distinguished Engineer • Identity Architect
[image: address]8020 Towers Crescent Drive, Vienna, VA 22128
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assistant: [image: email] sharon.anderson at capitalone.com

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