On Fri, Mar 21, 2008 at 9:36 AM, Valerio Venturi <valerio.venturi@cnaf.infn.it> wrote:
The authorization problem is still unsorted. Currently the prototype allows for specifying which subjects are allowed to query for other subjects.
Right, you could implement something at the attribute authority (AA) that suitably restricts the set of requesters, but that doesn't solve the problem. Since the profile specifies that the name identifier in the query is a DN, there is no way to prove user presence at the Grid SP. Without proof of user presence, an SP could phish for attributes to its heart's content. Note there is no such problem for the self-query (of which traditional VOMS is an example), rather the problem involves a query where the requester is acting on behalf of the subject. In that case, the subject must pass some piece of information to the Grid SP that the SP can forward to the AA. In Shibboleth attribute query, for example, that piece of information is a transient and/or encrypted identifier. We don't have that here, and so the profile is lacking. Consequently, I'm convinced we've specified the name identifier in the query (DN) incorrectly. The requester has to prove user presence. More than a DN is needed. Since the user is authenticating to the Grid SP with an X.509 certificate, the obvious conclusion is that 1) there is some piece of info in the cert that proves user presence, and 2) the SP passes the complete cert (not just the DN) to the AA.
I have seen that an implementation for the SAML Attribute Query for X.509 Subjects has made in as a Google Summer of Code 2008 project mentored by Globus. Keep us informed about the thing and let us know if you think that VOMS or UVOS implementations can somehow participate in the demo.
Thanks, I'll do that. Tom