[Openid-specs-ab] Single Sign-On is dead on iOS 11

Iain McGinniss iainmcgin at google.com
Tue Jun 13 21:57:39 UTC 2017

Each SFSafariViewController (SFSVC) instance is essentially a new browser,
with the following consequences:

1. If the user signs in to the OP in Safari, this signed in state is not
visible from any SFSVC instance.
2. If the user signs in via an SFSVC, this signed in state also cannot be
synchronized to Safari.

As a result, there's no shared OP session between any apps; the user must
re-authenticate with the OP within every app that uses it.

Furthermore, the Intelligent Tracking Prevention
<https://webkit.org/blog/7675/intelligent-tracking-prevention/> *may* flag
the OP domain as a capable of tracking the user, at which point any cookie
/ local storage state associated with that domain is "redacted" if the user
has not interacted with the OP domain in the last 24 hours. "Interaction"
here specifically means loading a top-level page on that domain and
clicking on something. It seems highly likely that *.google.com is going to
be marked as a tracking domain in Safari.

So, if you do anything in iframes with your OP domains (we do at Google),
your cookies are going to appear and disappear in a very unpredictable way.
Session state is going to become very unreliable.

I plan to give an impromptu short talk on these changes at CIS.


On Tue, Jun 13, 2017 at 2:40 PM, rich levinson via Openid-specs-ab <
openid-specs-ab at lists.openid.net> wrote:

> Hi Nat, et al,
> I am not sure I understand why this situation should cause anything to
> "break".
> Let me explain my view of this situation, in the context of general
> session mgmt,
> which is the following:
> In the "OpenID Connect Session Management 1.0" spec:
>     http://openid.net/specs/openid-connect-session-1_0.html
>  it says:
> "In OpenID Connect, the session at the RP typically starts
>  when the RP validates the End-User's ID Token.
>   ...
> When the OP supports session management, it MUST also return the Session State
>  as an additional session_state parameter in the Authentication Response.
>   ...
> This parameter is:
>     session_state
>      Session State.
>      JSON [RFC7159] string that represents the End-User's login state at the OP.
>      It MUST NOT contain the space (" ") character.
>      This value is opaque to the RP.
>      This is REQUIRED if session management is supported.
> The Session State value is initially calculated on the server."
> This indicates that the OP has knowledge of the End-User's login state at
> the OP.
> However, this login state is independent of the "session at the RP", which
> is
> created when the client app (RP) rcv's the identity token which, in the
> protocol,
> is well after the End-User logged in at the OP.
> Later in the spec, section 5, it is also stated that:
> "5.  RP-Initiated Logout
> An RP can notify the OP that the End-User has logged out of the site and
>  might want to log out of the OP as well.
> In this case, the RP, after having logged the End-User out of the RP,
>  redirects the End-User's User Agent to the OP's logout endpoint URL.
> This URL is normally obtained via the end_session_endpoint element
>  of the OP's Discovery response or may be learned via other mechanisms."
> This basically confirms the supposition above that the OP login and the RP
> session are
> effectively independent entities.
> Now, let's consider the case where a 2nd RP decides to start a session w
> the same End-User,
> presumably, a 2nd RP on the same device where the 1st RP established a
> session.
> When the 2nd RP sends the Authentication Request to the OP's /authorize
> endpoint,
> it seems obvious to me that the OP knows the End-User is logged in and
> would have
> no problem issuing a 2nd id-token to the 2nd RP, w/o re-logging in the
> End-User.
> Assuming this is the case, then I do not understand why ios-11, by
> "siloing" the apps
> prevents the OP from issuing new id-tokens to each app, all under the
> original
> OP-login by the End-User.
> Am I missing something?
>   Thanks,
>   Rich
> On 6/12/2017 8:04 PM, Nat Sakimura via Openid-specs-ab wrote:
> Maybe we can call upon the privacy community as well raising the voice
> that this is very bad for privacy.
> I wonder what is the privacy enhancement they have in mind.
> On Fri, Jun 9, 2017 at 2:34 AM 'Iain McGinniss' via OIDF Account Chooser
> list <oidf-account-chooser-list at googlegroups.com> wrote:
>> Hello all,
>> Just to bring this to your attention: Apple has essentially killed single
>> sign-on for native apps in iOS 11. Changes made to SFSafariViewController
>> (used by AppAuth, and the recommended mechanism for federated login by
>> Apple) now mean that browser state is partitioned per app, so there is no
>> way for an existing authentication in the browser to be reused by an app.
>> This fundamentally breaks an important part of OpenID Connect - users
>> will now need to re-authenticate with their IDP in every app that they use.
>> There is still time to provide feedback to Apple on this change, though
>> they have been discussing this change in terms of "enhancing privacy" and
>> I'd be very surprised if they change tack now.
>> Iain
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> --
> Nat Sakimura
> Chairman of the Board, OpenID Foundation
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