Re: [credential management] Identity Credentials API Extension

Hi Brad,

>From my reading of the communications to date the primary issue that has
been raised by the Credentials CG is the restriction within the current API
to be same-origin.

The existing FederatedCredential proposal makes no sense if it is
restricted to same-origin use. Federation is, by definition, cross-origin.

With the same-origin restriction in place, I am unsure what value the
current proposed API adds or what problem it solves. The use case is so
simple, and so close to the existing password-autocomplete functionality
built into most browsers.

As a user when I visit a site I have logged into before and have no current
session I see a login form with my username and password already filled in
and have the ability to explicitly re-use those "credentials" to login
again. One click and I have achieved the same outcome as this API AND had
the opportunity to do so explicitly. Is this API potentially making things
worse for the user by hiding their control of the login process behind
configuration screens? Also, given that this is a client side API I see
little utility for server technology vendors who already do complex session
management using existing technology.

Unless WebAppSec considers cross-origin credentials in it's scope I see
little value in this API. On the contrary, I see an API which will annex
the use of the word "credential" in a very narrow use case which makes a
more broad and valuable use case more challenging to implement in the
future AND an API that purports to support federated login but is unable to
solve the biggest usability issue in federated identity; the ability to
filter the providers offered to the user so they are not presented with a
wall of badges.

Storing usernames and passwords in a same-origin only system makes sense.
Storing any other credentials under such a restricted system doesn't. I
propose that if the API is to be published it is vastly simplified to only
support username/passwords and is renamed to "Password API" or "Login API".

Adrian


On 27 May 2015 at 05:20, Brad Hill <hillbrad@gmail.com> wrote:

> I know Mike has gotten quite in-depth on this, and I'm willing to be told
> I'm wrong, but the more I look at the Credentials CG's use cases as
> presented here, the less I'm convinced they are good fit for the
> "Credential Management API Level 1" spec.  Asynchrony is a nice and broad
> abstraction behind which many things can be hidden. BUT...
>
> If use case #1 is: wait locally on a promise to return some very finite
> set of information (username/password or username/federation provider pair)
> that is stored or hopefully cached locally, with the worst case being the
> user has to re-authenticate one time to their password manager and fetch
> them from the cloud.
>
> And use case #2 is: take as input a "query", assess the satisfiability of
> the query against available credentials and providers and perform an
> unbounded set of recursively defined fetching, aggregation and
> cryptographic operations, including queries to some as-yet-unspecified "new
> mechanism where the URLs refer to decentralized network that holds onto
> documents that include decentralized identifiers and public keys" in order
> to resolve them, including possibly having the user perform authentication
> or add new providers and credentials....
>
> Then I just don't see how it is in any way possible or sane to expect the
> same API shape.  The latter case has so many more potential failure and
> timeout cases and places which may require user interaction and resolution,
> you'll either overcomplicate case #1 or never adequately deal with the
> actual necessary complexity of #2.
>
> Even more so, the vast differences here mean there will never be a client
> to the API that calls it in an abstract function without knowing in advance
> which path they expect to be travelled.  Forcing callers with clearly
> different intents into overly-abstracted APIs when there is no driving
> use-case for the commonality is bad design, even if we can find a way to
> make them fit.
>
> I think in particular the use cases desired by the Credentials CG will
> suffer from further trying to achieve commonality here, because the APIs
> will lack the necessary richness and specificity to purpose that are
> required by the innovative patterns you're contemplating.
> <hat=individual>I also believe it is naive to think you can understand what
> the best API shape will look like until all of these moving parts are
> themselves better defined in their success and failure cases.
> </hat=individual>
>
> Additionally, there are fundamental changes to the web security and
> privacy model which are contemplated by the Credentials CG's proposal which
> should be dealt with independently.  Not using HTTPS and inventing an
> entirely new method to locate and establish trust in keys is a huge thing
> in and of itself, as big a thing as has ever been tried in this space, and
> way too big an elephant to hide under the cafe table of this little API.
>
> My current opinion therefore, as chair, is that the proposals on the table
> in the WebAppSec 2015 charter and from the Credentials CG are quite
> different things, which may share some similarities in common naming and
> broad intent, but which neither will benefit technically from further
> efforts to converge.
>
> -Brad
>
> On Thu, May 21, 2015 at 12:21 PM Manu Sporny <msporny@digitalbazaar.com>
> wrote:
>
>> bcc: Web Payments IG, Web Payments CG, Credentials CG
>>
>> Mike, Brad, Dan, and WebAppSec'ers,
>>
>> As promised on Monday, Dave Longley and I have put together an
>> experimental extension spec for the Identity Credentials API, based on
>> the WebAppSec Credential Management API:
>>
>>
>> https://docs.google.com/document/d/1tI0CJ4wAKKPQacrxOmTtl_GQUBeVtbg8e1ZSXs2SWag/edit?pli=1#
>>
>> We followed Section 8.2 "Extension Points" in the CMAPI spec to do so.
>> The document:
>>
>> 1. Starts out by providing an overview of what the Credentials CG and
>>    Web Payments CG/IG would most likely need for their use cases.
>> 2. We then elaborate on more-or-less how the extension would work in
>>    practice, following the guidance given in section 8.2 on how to
>>    write extensions. We provide all algorithms necessary to do a
>>    simple cross-origin credential storage, request and transmission.
>> 3. We close by listing the problems that we see with the current
>>    specification as well as open questions wrt. browser implementation
>>    concerns.
>>
>> At this point, we ask that:
>>
>> 1. The WebAppSec WG Review the extension specification, and
>> 2. Make comments/suggestions either onlist or in the Google Doc, and
>> 3. that Mike West schedules some time to chat with us to answer any
>>    questions that he may have after reviewing the document.
>>
>> We're happy to jump on the next WebAppSec call and present this work if
>> that's deemed helpful to the group.
>>
>> -- manu
>>
>> --
>> Manu Sporny (skype: msporny, twitter: manusporny, G+: +Manu Sporny)
>> Founder/CEO - Digital Bazaar, Inc.
>> blog: Web Payments: The Architect, the Sage, and the Moral Voice
>> https://manu.sporny.org/2015/payments-collaboration/
>>
>>