Re: [OAUTH-WG] AD Review: draft-ietf-oauth-resource-indicators-02

[Brian Campbell <[e-mail]>]

Doh, I got distracted with the registration question and lost track of this
fork of the thread. I'll need to do a -04 also (after maybe some more
discussion too) before I pass the ball back to the AD.

On Wed, Jul 17, 2019, 4:04 PM Roman Danyliw <[e-mail]> wrote:

> Hi Brian!
>
>
>
> *From:* Brian Campbell [mailto:[e-mail]]
> *Sent:* Wednesday, July 17, 2019 4:35 PM
> *To:* Roman Danyliw <[e-mail]>
> *Cc:* [e-mail]
> *Subject:* Re: [OAUTH-WG] AD Review:
> draft-ietf-oauth-resource-indicators-02
>
>
>
> Thank you, Roman, for the review. Some replies are inline below. I'll aim
> to push out a -03 addressing this stuff sometime not too long after the I-D
> submission embargo is lifted next week.
>
>
>
>
>
> On Tue, Jul 16, 2019 at 5:23 PM Roman Danyliw <[e-mail]> wrote:
>
> Hi!
>
> The following is my AD review of draft-ietf-oauth-resource-indicators-02.
> The document is in good shape.
>
>
>
> That's always nice to hear :-)
>
>
>
>
> (1) Section 2. Per "The parameter can carry the location of a protected
> resource, typically as an https URL, or a more abstract identifier", is
> this "abstract identifier" still an absolute URI per Section 4.3 of RFC3986?
>
>
>
> Absolutely (see what I did there? sigh...). Syntactically it's an absolute
> URI. Semantically, while it might be an actual network addressable location
> identified by an HTTPS URL, it might also be a URN or something that more
> abstractly indicates a resource or grouping of resources. But its format is
> an absolute URI regardless.
>
>
>
> I'm not sure what, if anything, can be added or changed here to help
> clarify. But I'm happy to entertain suggestions, if you've got em and/or
> think something is needed.
>
>
>
> [Roman] Understood.  Concur there is nothing to do here.
>
>
>
>
> (2) Section 2.2.  in the sentence "To the extent possible, when issuing
> access tokens, the authorization server should adapt the scope value
> associated with an access token to the value the respective resource is
> able to process and needs to know":
>
> --  is this language suggesting that the authorization server is modifying
> the scope value based on the resource it sees?  I'm trying to understand
> what "adapt" means, especially in relation to the improved security and
> privacy the subsequent sentence suggests.
>
>
>
> Perhaps "adapt" wasn't the best choice of word but it's meant to say that
> an authorization server with sufficient understanding of what scopes are
> applicable to what resources (which won't always be the case or even
> possible but sometimes) could limit the scope associated with an access
> token (downscoping really) to only the scope that is applicable to the
> resource.
>
>
>
> Some of the examples (figures 2 - 6) attempt to show, among other things,
> a hypothetical case of how this might go down.
>
>
>
> In Figure 2 the initial authorization request that's approved has scope of
> calendar & contacts and resources https://contacts.example.com/ &
> https://cal.example.com/
>
>
>
> A subsequent access token request (Figure 3) has resource
> https://cal.example.com/ and the issued access token scope (Figure 4) is
> "adapted" to that resource to be only calendar
>
>
>
> Another subsequent access token request (Figure 5) has resource
> https://contacts.example.com/ and the issued access token scope (Figure
> 6) is downscoped based on that resource to be only contacts
>
>
>
> Would it be easier to understand if the word "downscope" was used rather
> than "adapt"?
>
>
>
> [Roman] Using “downscope” does work for me.  It captures that the server
> is going to reduce the scope (and certainly not expand it).
>
>
>
>
> -- (Depending on the above) Is there a security consideration here for the
> server relative to confidential scope values and how they might be modified?
>
>
>
> I'm not sure, to be honest. Downscopping when possible and to the extent
> possible is usually a good idea (least privilege and all that) but I think
> maybe I'm missing your point/question.
>
>
>
> [Roman] Yes, least privilege was part of it and I think the text above
> gets at it.  However, the other part is the relationship with the next
> sentence in the paragraph, “This further improves privacy as scope values
> give an indication of what services the resource owner uses and it improves
> security as scope values may contain confidential data”.  If the initial
> request was notionally a scope of “all the houses on the block”, but the
> server knew that this request was too broad and down-scoped to “only the
> corner house”, wouldn’t this actually be worse for privacy?  I also don’t
> follow how reducing the scope impacts confidential data.
>
>
>
>
> (3) Editorial
> ** Section 1 and 2.1.  Multiple Typo.  s/the the/the/g
>
>
>
> Apparently I'm fond of the double "the" and have a hard time spotting it
> myself. I think this is the second review in as many weeks that you've
> caught a few of those. Will fix.
>
>
>
>
> ** Section 2.  Editorial. s/resource at which/resource to which/
>
>
>
> Okay.
>
>
>
>
> ** Section 2.  Editorial.
> s/ And can also be used to inform the client that it has requested an
> invalid combination of resource and scope./
>         It can also be used to inform the client that it has requested an
> invalid combination of resource and scope./
>
>
>
> Yup.
>
>
>
>
> ** Section 2.1. Multiple Typo. s/an an/an/g
>
>
>
> Again with the double words. Sigh. A double double even.
>
>
>
>
>
>
> ** Section 2.2.  Editorial. s/token request and response/token request
> (Figure 3) and response (Figure 4)/
>
>
>
> Makes sense.
>
>
>
>
>
> ** Section 3.  Typo.  s/a invalid/an invalid/
>
>
>
> Of course.
>
>
>
>
> ** Section 3.  Missing words.  "A bearer token that has multiple intended
> recipients (audiences) can be used by any one of those recipients at any
> other."  Is it protected resource?
>
>
>
> Well, those are all the words that I'd intended to be there :/ But it does
> read a little curtly. How about the following instead?
>
>
>
> "A bearer token that has multiple intended recipients (audiences)
> indicating that the token is valid at more than one protected resource can
> be used by any one of those protected resources to access any of the other
> protected resources."
>
>
>
> [Roman] Thanks for fixing all of these.
>
>
>
>
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