Re: [OAUTH-WG] WGLC for Step-up Authentication

[Denis <[e-mail]>]

Hi Brian,

The text states:

    Also recall that OAuth 2.0 [RFC6749] assumes access tokens are
    treated as
    opaque by clients. So, during the course of any token caching
    strategy, a client *cannot* inspect the content of the access token to
    determine the associated authentication information or other details.
    The token format might be unreadable to the client or might change at
    any time to become unreadable.

A client *can *inspect the content of the access token.

A better wording  would be:

    ...  a client *should not *inspect the content of the access token ...

It would be worthwhile to add a Privacy Considerations section:

    10. Privacy Considerations

    Since access tokens are presumed to be opaque to clients, clients
    (and hence users) are not supposed to inspect the content of the
    access tokens.
    Authorizations Servers are able to disclose more information than
    strictly necessary about the authenticated user without the end user
    being
    able to know it. Such additional information may endanger the
    privacy of the user.

Denis


> I've published an -04. It has that very minor change. There was also 
> an off-list discussion during WGLC that resulted in thinking it'd be 
> worthwhile
> *_to add a reminder that access tokens are opaque to clients_*. So I 
> took that as LC feedback and -04 adds a brief note towards that end.
>
> https://datatracker.ietf.org/doc/draft-ietf-oauth-step-up-authn-challenge/
>
>
>
> On Mon, Oct 10, 2022 at 1:22 PM Vittorio Bertocci 
> <vittorio=[e-mail]> wrote:
>
>     Thanks Dima for the comment. Some thoughts:
>
>     > (editorial)...
>     Good point. "statically" would characterize the simplest of the
>     scenarios, but in fact any case where the AS is the only arbiter
>     of the authn level works for the point we are trying to make.
>     We'll drop "statically". Thanks!
>
>     > Apart from...
>     This spec focuses on empowering an RS to communicate its ACR and
>     freshness requirements, regardless of the reasons leading the RS
>     to make that determination: the logic by which that happens is
>     explicitly out of scope, and in many real life cases it might
>     simply be unknowable (eg anomaly detection engines based on ML are
>     often back boxes). The mechanism described here can be used
>     alongside other mechanisms that might require the client to get
>     the user to interact with the AS, as it is the case for
>     insufficient_scope, but those remain distinct cases (eg
>     insufficient _scope might not require any step up but simply
>     explicit user consent, and if it does require a stepup, that's
>     entirely determined by the AS without any communication with
>     client or RS required).
>
>     On Fri, Oct 7, 2022 at 17:43 Dima Postnikov <[e-mail]>
>     wrote:
>
>         *This message originated outside your organization.*
>
>
>         ------------------------------------------------------------------------
>
>         Couple of quick comments from me:
>
>         1) (Editorial) >In simple API authorization scenarios, an
>         authorization server will statically determine what
>         authentication technique
>
>         In many scenarios, authorization servers will use *dynamic*
>         decisioning to determine authentication techniques; it's just
>         not exposed to the client in a way to make it actionable
>         (which is why this specification's intent makes perfect sense).
>
>         2) Apart from authentication level, there might be other
>         reasons why users might be forced to go through the
>         authorization flow, for example, insufficient authorization /
>         scopes / claims / etc.
>
>         If there is a mechanism to let the client know, as a
>         practitioner, i'd rather have the same approach for both
>         authentication and authorization. There are a range of
>         authorization policy engines in the market that could return
>         "STEP UP is required" after looking at authentication,
>         authorisation and many other real-time signals. It's just not
>         standardized...
>
>
>         On Sat, Oct 8, 2022 at 7:30 AM Pieter Kasselman
>         <pieter.kasselman=[e-mail]> wrote:
>
>             I am very supportive of this work and have been working
>             through different use cases to see whether it can satisfy
>             the requirements that arise from them.
>
>             One observation from working through these uses cases is
>             that as customers move to Zero Trust architectures, we are
>             seeing customers adopting finer grained policy
>             segmentation. Consequently customers are planning to
>             deploy segmented access control by data or action
>             sensitivity, within a service. This approach to policy
>             design makes it more common for a single service to depend
>             on multiple authentication context values or combinations
>             of authentication context values.
>
>             An example of this is a policy that has multiple acr
>             values (e.g. acr1=password, acr2=FIDO, acr3=selfie check,
>             acr4=trusted network). A customer may define a policy that
>             requires different combinations of these acr values, for
>             example, a file server may requires password for general
>             access (e.g. acr1), FIDO authentication (acr2) or password
>             access and being on a trusted network to read sensitive
>             data (acr 2 of (acr1 + acr 4), FIDO authentication and
>             password (acr1 + acr2) for accessing editing sensitive
>             documents and a real-time selfie check on top of FIDO and
>             presence on a trusted network  (acr1 + acr2 + acr3 + acr4)
>             to initiate a sensitive workflow (e.g. check-in code).
>             Other variations of this includes database access with
>             different types of access requirement for certain rows
>             (row-level permissions) or columns (column level
>             permissions) with different combinations of acr values.
>
>             I was curious if this type of scenario where multiple
>             authentication contexts and combinations of contexts are
>             required is something others see (or are beginning to see)
>             as well?
>
>             Cheers
>
>             Pieter
>
>             *From:*OAuth <[e-mail]> *On Behalf Of
>             *Rifaat Shekh-Yusef
>             *Sent:* Thursday, September 22, 2022 3:02 PM
>             *To:* oauth <[e-mail]>
>             *Subject:* Re: [OAUTH-WG] WGLC for Step-up Authentication
>
>             *Correction:*
>
>             Please, review the document and provide your feedback on
>             the mailing list by *Oct 7th, 2022*.
>
>             On Thu, Sep 22, 2022 at 9:52 AM Rifaat Shekh-Yusef
>             <[e-mail]> wrote:
>
>                 All,
>
>                 This is to start a *WG Last Call *for the *Step-up
>                 Authentication *document:
>                 https://www.ietf.org/archive/id/draft-ietf-oauth-step-up-authn-challenge-03.html
>                 <https://urldefense.com/v3/__https://nam06.safelinks.protection.outlook.com/?url=https*3A*2F*2Fwww.ietf.org*2Farchive*2Fid*2Fdraft-ietf-oauth-step-up-authn-challenge-03.html&data=05*7C01*7Cpieter.kasselman*40microsoft.com*7C0078f809101147bc978308da9ca32020*7C72f988bf86f141af91ab2d7cd011db47*7C1*7C0*7C637994521713812011*7CUnknown*7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0*3D*7C3000*7C*7C*7C&sdata=18sfemyWqYb06PvUA9eTLaq0ccDY14*2F6ETo58JpE*2FJQ*3D&reserved=0__;JSUlJSUlJSUlJSUlJSUlJSUlJSUlJSUl!!PwKahg!537tJQfGj3Z_Yi2waywl1VPGyDs9818JE-M-KNFgPtoB0O26a7ksRvAYrPyzfKKXsMKCVblAomtRXj8$>
>
>
>                 Please, review the document and provide your feedback
>                 on the mailing list by *Sep 30th, 2022*.
>
>                 Regards,
>                  Rifaat & Hannes
>
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