It's right there in the definition:

If the value contains multiple space-delimited strings, their order does not 
matter, and each string adds an additional access range to the requested scope.

EHL

From: oauth-boun...@ietf.org [mailto:oauth-boun...@ietf.org] On Behalf Of 
Torsten Lodderstedt
Sent: Saturday, August 28, 2010 11:38 AM
To: David Recordon
Cc: OAuth WG
Subject: Re: [OAUTH-WG] comments/questions on draft 10

I think a bit more then just defining the delimiter is required in order to 
make things work as you described (in a interoperable way).

5.2.1 states "The "scope" attribute is a space-delimited list of scope values 
indicating the required scope of the access token for accessing the requested 
resource."

So in my understanding the resource may indicate the scope required for access, 
no word about addition. There is no relation stated to the scope associated 
with a insufficient token sent to a resource.

Even if this attribute would contain a scope diff, some more questions are 
open: How does the client know what scope values from different 
WWW-Authenticate headers can be combined? Moreover, the draft does not support 
to extend a token's scope. So how should the client use that knowledge? 
Kick-off another authorization process?

regards,
Torsten.

Am 25.08.2010 00:59, schrieb David Recordon:
Giving scope basic structure (space delimitated) allows any app developer to 
store a list of scopes which they have and compare any desired scopes to that 
list. While the meaning of each scope is not standardized, it allows for this 
sort of simple operation on scope. 5.2.1 also defines how a protected resource 
can tell the client what additional scope(s) are needed in order to make their 
request successful. Standardizing the delimiter allows for this sort of 
"addition" interaction.

--David


On Tue, Aug 24, 2010 at 10:41 PM, Torsten Lodderstedt 
<tors...@lodderstedt.net<mailto:tors...@lodderstedt.net>> wrote:
 --- p.6 terminology/authorization server
"         A server capable of issuing tokens after successfully
        authenticating the resource owner and obtaining authorization.
        The authorization server may be the same server as the resource
        server, or a separate entity. "
Based on the discussion in 
http://www.ietf.org/mail-archive/web/oauth/current/msg03812.html, I would 
suggest to add the following: "A single authorization server may issue tokens 
for different resource servers."

--- p.11 What is the meaning of "... the authentication of the client is based 
on the user-agent's same-origin policy." ? As far as I know, this policy 
restricts the hosts the JavaScript client is allowed to interact with. How does 
this "feature" authenticate the client on the authorization server?

--- Examples and client authentication: Since BASIC authentication is the 
default mechanisms for client authentication, I would suggest to use it in all 
examples.

--- Scope syntax and usage
The discussion in 
http://www.ietf.org/mail-archive/web/oauth/current/msg03812.html revealed most 
WG members do not want to define the scope's syntax and semantics in the spec. 
Instead these aspects shall be kept deployment specific. Accepted. To me, this 
means the scope is specified as a placeholder/pattern only and not as a 
fullblown parameter. In contrast, the draft raises the expectation to specify 
more than that e.g. by defining delimiters and talking about orders on scopes 
(less/equal). In my opinion, we should not pretend to standardize something we 
don't really standardize. Moreover, if we want to give the deployments the 
freedom to define the scope's syntax and semantics, then we should not impose 
any needless restrictions. Here are some examples:

p. 17
scope
        OPTIONAL.  The scope of the access request expressed as a list
        of space-delimited strings.  ..

Why is it neccessary to define a delimiter for a parameter that otherwise is 
completly left unspecified? What is the benefit? I would suggest to remove the 
delimiter definition and let the scope just be an opaque string that can be 
used by the deployment in any way. Lists of spec-delimited strings are one 
options, other deployments would probably use JSON documents or an elaborated 
scope-expression language.

p.22 "If the access grant being used already
        represents an approved scope (e.g. authorization code,
        assertion), the requested scope MUST be equal or lesser than
        the scope previously granted."

This statement is useless without a definition of an order and equality among 
scope values. And there might also be a sets, subsets and supersets of scopes.
Proposal:
Either (a) add an clarification that equality, order, e.t.c. of scopes is 
deployment specific or (b) remove the statement.

p. 33    The "scope" attribute is a space-delimited list of scope values
  indicating the required scope of the access token for accessing the
  requested resource."

There is no explanation what a compliant client should do with the scope 
attribute value of a WWW-Authenticate header.
Proposal:
Either a) state that usage of the scope value is deployment specific or b) that 
the client shall pass this attribute to the respective scope parameters on 
end-user authorization and tokens endpoint or c) remove the attribute.

--- section 3: "The authorization server MUST support the use of
  the HTTP "GET" method for the end-user authorization endpoint, and
  MAY support the use of the "POST" method as well."

What is the use case behind POST on that endpoint? Is the authorization server 
expected to behave differently with respect to the redirect back to the client? 
For example, shall HTML FORM Redirection be used for the way back?

section 4.3. In my opinion, unauthorized_client should be used on conjunction 
with status code 403.

section 5.1.1. access token charset: This definition allows authorization 
server for the issuance of token, which cannot be safely passed with URI query 
parameters (e.g. they are allowd to contain "&"). But section 5.1.2 specifies 
that access tokens can directly be used as such parameters. This may cause 
problems.

Proposal: Either a) modify the access token charset to be URI query parameter 
compliant or b) advice resource server/clients using URI query parameters to 
additionaly URL-safe-base64-encode tokens before sending them to the resource 
server.

regards,
Torsten.
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