Re: [OAUTH-WG] Seeking Clarification: Potential Ambiguity in Specification

agks mehx <> Tue, 10 January 2012 01:57 UTC

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Date: Mon, 09 Jan 2012 17:57:36 -0800
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From: agks mehx <>
To: William Mills <>,
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Subject: Re: [OAUTH-WG] Seeking Clarification: Potential Ambiguity in Specification
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That's fine and still consistent with the essence of (a), which is to
require implementations to accept requests without a scope parameter.  If
an implementation chooses to issue scoped credentials, that's perfectly

My focus is solely on whether the scope parameter should be termed as
OPTIONAL or REQUIRED within the specification.

Perhaps, (b) is a better choice -- to make it REQUIRED?

On Mon, Jan 9, 2012 at 5:51 PM, William Mills <> wrote:

> Re your "a" below: No, implementations may issue scoped credentials if
> they have a default scope.  It says elsewhere in the spec that the scope
> issued by the server may not match the requested scope, which is why the
> server returns a scope value.  This is for informational purposes only for
> the client so it can know what scopes it should already have.
> You don't have to support empty scopes, and it would be completely valid
> for the auth server to reject a request for an unknown scope, which could
> include the empty scope if the auth server doesn't support it.
> -bill
>   ------------------------------
> *From:* agks mehx <>
> *To:* William Mills <>;
> *Cc:* SM <>; Eran Hammer <>
> *Sent:* Monday, January 9, 2012 5:44 PM
> *Subject:* Re: [OAUTH-WG] Seeking Clarification: Potential Ambiguity in
> Specification
> scope parameter in the HTTP requests.
> Two choices stand out to me:  (a) keep the scope parameter truly optional
> which implies requiring all implementations to implement un-scoped
> credentials;  (b) make the scope parameter REQUIRED thus removing the
> confusion and letting implementations choose whether or not they want to
> allow an empty scope.
> The former, (a), imposes a little bit of extra work for implementations
> but benefits users, clients, and arguably implementations, by allowing the
> un-scoped credentials use-case.
> The latter, (b), merely improves the quality of the specification -- I do
> not see what purpose is served by calling the scope parameter OPTIONAL when
> vendors are free to require it as they please and still claim conformance.
> On Mon, Jan 9, 2012 at 4:53 PM, William Mills <>wrote:
> There are definitely use cases for un-scoped credentials, which the
> implementations I have seen implement as an empty scope.  Are you worried
> specifically about the scope parameter in the HTTP requests, or as
> represented in the credential used to access the PR?
>   ------------------------------
> *From:* agks mehx <>
> *To:* SM <>; Eran Hammer <>;
> *Sent:* Monday, January 9, 2012 4:17 PM
> *Subject:* Re: [OAUTH-WG] Seeking Clarification: Potential Ambiguity in
> Specification
> Hi SM and Eran,
> I am confused again, after re-reading Eran's response, whether or not an
> implementation that rejects *missing* (as opposed to empty) scope is
> conformant or not.  (Eran, your response was a bit ambiguous on whether an
> implementation is free to error out on an missing scope parameter or not --
> I can clearly see it is free to error out on an empty scope parameter, but
> that's a different situation than the one I am concerned about.)
> The vendor definitely gives a higher priority to claiming conformance and
> I believe they would change their implementation, but they believe they are
> conformant.
> I do feel the IETF Working Group should make this part of the spec less
> ambiguous -- why not just make 'scope' REQUIRED and end the misery?  Or,
> make it clear that an implementation is not conformant to the spec if it
> requires optional parameters?
> Additionally, I will resend a use-case for the no-scope parameter because
> my earlier reply unintentionally went privately to Eran and not to the list:
> I can suggest a spec modification that says that an implementation MUST
> accept a request without a scope parameter, in which case one possibility
> for an implementing server is to return an access token or code that does
> not allow any operations.  The purpose of this otherwise "useless"
> token/code is that the OAuth server confirms that the user is *some* user
> without any information on *which* user it is.  (If the user is not
> authenticated by the vendor then of course no valid token/code is returned.)
> An example might help:  Facebook, when it started, would manage social
> networks based on college email domain --, etc.  Facebook
> used to do it by asking for your email address and sending a confirmation
> mail.  But what if I wanted to tell Facebook just the fact that I was at
> but I did not want to share my email address with Facebook, or
> any other unique identifier?  If the spec required implementations to work
> without a scope parameter, it would solve this use case perfectly.
>  Facebook wouldn't really care about my school email address or unique id
> -- I could use my non-school personal email and all Facebook wanted to know
> was whether I should be in that school network or not simply by using the
> barebones no-scope OAuth request.
> Vendors do not lose anything if the spec requires such no-scope requests
> to be fulfilled. They are merely confirming that a user is *some* user with
> the user's consent.  There are valid cases on the client side such as
> determining network membership without needing network identity.  And it
> cleans out the optional semantics of scope.
> Users win in that they have a way to confirm network membership without
> having to reveal a unique identifier.
> Clients win in that users will be more willing to confirm network
> membership if they are not also required to reveal a unique identitfier.
> This is off-the-cuff but I will be very happy to formalize it and present
> it to the list.  I hope the essential concept made it through my writing!
> A.
> On Mon, Jan 9, 2012 at 3:47 PM, SM <> wrote:
> Hello,
> At 15:14 09-01-2012, agks mehx wrote:
> Thank you for the response.  If I understand correctly, the vendor is
> correctly that their implementation conforms to the specification even
> though it rejects requests that do not specify the scope parameter.  That
> answers my question.
> The better answer is from Eran (
> ).
>  Whether I was asking for (i) a clarification; or (ii) trying to resolve a
> disagreement.  I think I was trying to verify whether indeed there was a
> disagreement. I. e. whether my understanding of the specification was
> correct or not.  It seems I was mistaken in understanding the spec.
> See comment below.
>  There is no disagreement with the vendor at this point because the two
> responses from this list indicate that the vendor is right.  (I still don't
> understand why scope isn't made a required parameter in the specification
> so that such confusion can be avoided, but that's a minor point.)
> You locked in on the term "optional" without going into the details of the
> draft.  I would not claim conformance with a specification if my API
> specifies that the optional parts are required as someone writing an
> implementation from the draft will run into the same problem as you.
>  Saying that the vendor is wrong will not get them to fix it.
> Regards,
> -sm
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