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

[Brian Campbell <[e-mail]>]

Thanks Denis, I agree the word "cannot" isn't quite right there. I
struggled with trying to find the right wording (more than I probably
should have) attempting to add a note/reminder without getting into
normative sounding language. But I also wanted to make a firm statement.
Words are hard sometimes. Oftentimes! But reading it again today, "cannot"
doesn't work very well. I think changing to "must not" is appropriate. The
privacy implications of opaque tokens are inherent to OAuth in general and
I don't believe this draft is an appropriate place to attempt to give them
treatment.

On Tue, Oct 11, 2022 at 2:57 AM Denis <[e-mail]> wrote:

> 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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>>>>
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