Re: [OAUTH-WG] Registration: Scope Values

["Donald F Coffin" <[e-mail]>]

Justin,

 

Thanks for the clarification.

 

Best regards,

Don

Donald F. Coffin

Founder/CTO

 

REMI Networks

22751 El Prado Suite 6216

Rancho Santa Margarita, CA  92688-3836

 

Phone:      [phone]

Email:        <mailto:[e-mail]>
[e-mail]

 

From: Justin Richer [mailto:[e-mail]] 
Sent: Friday, April 12, 2013 12:49 PM
To: Donald F Coffin
Cc: [e-mail]
Subject: Re: [OAUTH-WG] Registration: Scope Values

 

The question refers to the Dynamic Registration draft specifically, since
that's what's still editable. RFC6749 treats scopes as bags of strings that
are specific to the API that they're protecting, which lets them be either
static strings or expressions (or, really, whatever you like them to be).
The problem is that the Dynamic Registration draft isn't defining just the
conveyance of the scope string during the authorization process, it's got to
have language on what a scope is *for* in order for it to make sense in
registration. In other words, what does it mean to be "registered" with a
scope? What does it mean to ask for a scope at registration time? What does
it mean for a server to "grant" a scope at registration time? 

I had thought that the current language (which is mostly lifted from
RFC6749) was sufficient, but there's been question as to its intent, so I
want to make sure that it's very clear that Dynamic Registration is as
hands-off about scope values as RFC6749 is.

 -- Justin

On 04/12/2013 03:38 PM, Donald F Coffin wrote:

Justin,

 

While I understand the need to clarify the usage of the scope metadata, I'm
not clear on whether your question refers to the Dynamic Registration draft
or to RFC 6749?  

 

The current language of the Dynamic Registration draft to describe the scope
metadata usage is the same language used to describe the scope parameter
that appears in Section 3.3 of RFC 6749.  If the Dynamic Registration draft
uses language different than what is contained in the scope parameter
definition of RFC 6749 additional confusion about the usage of the scope
parameter may arise.  Perhaps the best way to address the issue within the
Dynamic Registration draft is to provide an explanation.  The examples you
provided in your posting could easily be included in the Dynamic
Registration draft and would achieve the desired effect of demonstrating how
the OAuth 2.0 scope parameter might be used.

 

Best regards,

Don

Donald F. Coffin

Founder/CTO

 

REMI Networks

22751 El Prado Suite 6216

Rancho Santa Margarita, CA  92688-3836

 

Phone:      [phone]

Email:       [e-mail]

 

From: Justin Richer [mailto:[e-mail]] 
Sent: Friday, April 12, 2013 11:25 AM
To: [e-mail]
Subject: [OAUTH-WG] Registration: Scope Values

 

Currently, the Dynamic Registration draft defines a "scope" value as part of
the client metadata table, with the following definition:

   scope
      OPTIONAL.  Space separated list of scope values (as described in
      OAuth 2.0 Section <http://tools.ietf.org/html/rfc6749#section-3.3>
3.3 [RFC6749]) that the client is declaring that
      it may use when requesting access tokens.  If omitted, an
      Authorization Server MAY register a Client with a default set of
      scopes.


The idea here is that a client can request a particular set of available
scopes from the AS (analogous as to what's available from many/most manual
registration pages today), and the AS can communicate back to the client
what scopes it's allowed to ask for at authz time. In a strictly-enforced
implementation, the client wouldn't be able to ask for any scopes that it
wasn't registered for in the first place.

However, it's been brought up in some side conversations that the language
as found in the DynReg spec might get in the way of people using the "scope"
field as an expression language. That is to say, you could have a scope like
<mailto:send_email_to:[e-mail]>
"send_email_to:[e-mail]" where the email address portion is
variable, or something like "read:*" which stands in for any scopes starting
with "read:" like "read:profile", "read:lists", etc. Precluding this
behavior wasn't my intent, and a liberal interpretation of the text
as-written would (I believe) lead to this being perfectly OK. Namely:

Client requests and is granted a service specific scope value like
"send_email_to" in registration. At runtime, the client knows how to turn
"send_email_to" into  <mailto:send_email_to:[e-mail]>
"send_email_to:[e-mail]", and the AS knows that a client that's
been granted "send_email_to" can ask for
<mailto:send_email_to:[e-mail]>
"send_email_to:[e-mail]". The fact that "send_email_to" expands
into an expression language is something specific to the service, and I
personally think it's up to the service to document "register for this" and
"ask for this at authn time" for clients, since this is all part of the API
more than it is part of the underlying OAuth protocol. OAuth merely provides
a handy place to communicate these values in an interoperable way, the
values themselves aren't intended to be interoperable. 


But my question to the group is simple: how can we rework the "scope"
metadata claim such that it works in both the simple "bag of discreet
strings" approach to scope as well as the "list of expressions" approach?
Does the language need to change at all?

 -- Justin