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

[Brian Campbell <[e-mail]>]

I don't know offhand a better place or if your specific privacy
consideration is already covered. Honestly, with that comment, I was just
aiming to keep the scope of this document concise and relevant.

On Tue, Oct 11, 2022 at 10:06 AM Denis <[e-mail]> wrote:

> Hi Brian,
>
> I agree with you that "must not" is more appropriate in that context.
>
> I also agree with you that the "privacy implications of opaque tokens are
> inherent to OAuth in general".
> However, I have not reviewed all the RFCs and I wonder whether such a
> privacy consideration has already been mentioned.
>
> It would be nice to start to mention it, rather than to continue to omit
> it. Do you see a better place to mention it ?
>
> Denis
>
> 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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