This is why redirects with a custom UI are so essential. This allows other 
forms of HRD without a NASCAR button list too. I hope that this will remain 
possible, as it's crucial to so many business use cases.


-Brock

On 5/9/2024 11:06:23 AM, Dick Hardt <dick.ha...@gmail.com> wrote:
The NASCAR problem is rooted in the RP does not know which provider(s) the user 
has, so sites showed all the choices. FedCM only shows the provider(s) the user 
has. 

On Thu, May 9, 2024 at 5:33 AM Warren Parad <wparad=40rhosys...@dmarc.ietf.org 
[mailto:40rhosys...@dmarc.ietf.org]> wrote:

I think I'm still missing something, and I'm sure it was discussed somewhere 
and I just didn't see it. How will this help avoid the NASCAR problem, for 
sites when a user signs up or when the user signs in on a new browser?

On Thu, May 9, 2024 at 1:07 AM Sam Goto <goto=40google....@dmarc.ietf.org 
[mailto:40google....@dmarc.ietf.org]> wrote:



On Wed, May 8, 2024 at 3:50 PM Neil Madden <neil.e.mad...@gmail.com 
[mailto:neil.e.mad...@gmail.com]> wrote:

On 8 May 2024, at 22:01, Joseph Heenan <jos...@authlete.com 
[mailto:jos...@authlete.com]> wrote:

On 8 May 2024, at 21:43, Sam Goto <g...@google.com [mailto:g...@google.com]> 
wrote:



On Wed, May 8, 2024 at 1:34 PM Joseph Heenan <jos...@authlete.com 
[mailto:jos...@authlete.com]> wrote:

Hi Neil


On 8 May 2024, at 18:45, Neil Madden <neil.e.mad...@gmail.com 
[mailto:neil.e.mad...@gmail.com]> wrote:


On 8 May 2024, at 17:52, Sam Goto <g...@google.com [mailto:g...@google.com]> 
wrote:


On Wed, May 8, 2024 at 7:23 AM Neil Madden <neil.e.mad...@gmail.com 
[mailto:neil.e.mad...@gmail.com]> wrote:


 
In particular, the call to the accounts endpoint assumes that the IdP is 
willing to provide PII about the user to the browser. That seems questionable. 

Aside from a privacy/security threat model perspective (meaning, the user agent 
already has visibility over every network request made available to the content 
area)

Sure, but if I use the recommended auth code flow or encrypted ID tokens, then 
PII is not exposed to the browser. And it’s not just the browser itself in the 
current proposal, as the token is exposed to javascript, of course, so the 
usual XSS risks. 

Sam’s response here is fair, but also note that as far as I understand it you 
can still use the authorization code flow or encrypted id tokens with the FedCM 
API 

That's correct: the browser doesn't open the response from the IdP to the RP, 
so it can, for example, be encrypted.

I was assuming that Neil was referring to the fact that the 
id_assertion_endpoint (which contains the user's IdP's PII accounts 
[https://fedidcg.github.io/FedCM/#dictdef-identityprovideraccount]) become, 
suddenly, transparent to the browser.

Oh yes, that’s true - but (I think) the data from the id_assertion_endpoint at 
least isn’t exposed to javascript and isn’t vulnerable to XSS?

That depends on whether the IdP correctly enforces the presence of the 
sec-fetch-dest header. If it doesn’t then yes, it would be vulnerable. 
Presumably it’s also vulnerable on older/niche browsers that don’t block sec-* 
headers: caniuse.com [http://caniuse.com] reckons > 8% of users globally are 
using browsers that don’t understand any sec-fetch-* headers. I’m not sure when 
sec-* was added to the forbidden list.

I guess, flipping this around, we might ask what is the legitimate purpose for 
which browsers need to access the user’s name, email address (both requires) 
and other identifying information? I’d have thought an identifier (possibly 
randomised) and some user-supplied account nickname would be sufficient.

That's easier to answer: the browser needs name/email/picture to construct an 
account chooser 
[https://docs.google.com/presentation/d/1iURrPakaHgBfQ6mAefKijjxToiTTgBSPz1rtaV0od98/edit#slide=id.p],
 which is the UX that tested best with users by a far margin. 

Static/unpersonalized permission prompts - example 
[https://www.cookiestatus.com/images/content/storage-access-api.jpg] in Safari, 
example 
[https://developers.google.com/static/privacy-sandbox/assets/images/storage-access-api-permission-prompt.png]
 in Chrome - perform extremely poorly (in comparison to account choosers), 
although have other benefits too (namely ergonomics and extensibility), so 
Chrome (and others) expose that too in the form of the Storage Access API 
[https://developer.mozilla.org/en-US/docs/Web/API/Storage_Access_API].
 

— Neil

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