You are correct that the idea behind the "scope" parameter at
registration is a constraint on authorization-time scopes that are made
available. It's both a means for the client to request a set of valid
scopes and for the server to provision (and echo back to the client) a
set of valid scopes.
I *really* don't want to try to define a matching language for scope
expressions. For that to work, all servers would need to be able to
process the regular expressions for all clients, even if the servers
themselves only support simple-string scope values. Any regular
expression syntax we pick here is guaranteed to be incompatible with
something, and I think the complexity doesn't buy much. Also, I think
you suddenly have a potential security issue if you have a bad regex in
place on either end.
As it stands today, the server can interpret the incoming registration
scopes and enforce them however it wants to. The real trick comes not
from assigning the values to a particular client but to enforcing them,
and I think that's always going to be service-specific. We're just not
as clear on that as we could be.
After looking over everyone's comments so far, I'd like to propose the
following text for that section:
scope
OPTIONAL. Space separated list of scope values (as described in
OAuth 2.0Section 3.3 [RFC6749]
<http://tools.ietf.org/html/rfc6749#section-3.3>) that the client can use when
requesting access tokens. As scope values are service-specific,
the Authorization Server MAY define its own matching rules when
determining if a scope value used during an authorization request
is valid according to the scope values assigned during
registration. Possible matching rules include wildcard patterns,
regular expressions, or exactly matching the string. If omitted,
an Authorization Server MAY register a Client with a default
set of scopes.
Comments? Improvements?
-- Justin
On 04/14/2013 08:23 PM, Manger, James H wrote:
Presumably at app registration time any scope specification is really a
constraint on the scope values that can be requested in an authorization flow.
So ideally registration should accept rules for matching scopes, as opposed to
actual scope values.
You can try to use scope values as their own matching rules. That is fine for a small set of
"static" scopes. It starts to fail when there are a large number of scopes, or scopes that can
include parameters (resource paths? email addresses?). You can try to patch those failures by allowing
services to define service-specific special "wildcard" scope values that can only be used during
registration (eg "read:*").
Alternatively, replace 'scope' in registration with 'scope_regex' that holds a
regular expression that all scope values in an authorization flow must match.
--
James Manger
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