RE: Issue #4: Context Handler

I agree with these changes.

I would also add under 7.3.5 Attribute Retrieval something like:

“Regardless of any dynamic modifications of the request context during policy evaluation, the PDP SHALL behave as if each bag of attribute values is fully populated in the context before it is first tested, and is thereafter immutable during evaluation. (That is, every subsequent test of that attribute shall use the same bag of values that was initially tested.)”

This seems like an obvious requirement, but I don’t see anything in the spec that requires a conformant PDP to act this way. It’s even hard to imagine such an ill-behaved context handler, but if it were especially lazy and there were many attribute sources (perhaps even different sources could contribute to the same multi-valued attribute), it is not out of the question.

Note that this statement does not impose any particular evaluation order on the policy rules, allowing for optimized policy rewrites. Nor does it rule out highly optimized attribute acquisition strategies, such as determining early in the evaluation what subset of attributes it might need and not asking for any others.

Regards,

--Paul

From: xacml@lists.oasis-open.org [mailto:xacml@lists.oasis-open.org] On Behalf Of remon.sinnema@emc.com
Sent: Friday, 24 February, 2012 09:31
To: xacml@lists.oasis-open.org
Subject: [xacml] Issue #4: Context Handler - Proposal

All,

Current text

30 Context handler

31 The system entity that converts decision requests in the native request format to the XACML

32 canonical form and converts authorization decisions in the XACML canonical form to the native

33 response format

Proposal

Context handler

The system entity that converts decision requests in the native request format to the XACML canonical form, coordinates with Policy Information Points to add attribute values to the request context, and converts authorization decisions in the XACML canonical form to the native response format.

Current text

474 4. The context handler constructs an XACML request context and sends it to the PDP.

Proposal

4. The context handler constructs an XACML request context, optionally adds attributes, and sends it to the PDP.

Current text

3280 7.3.5 Attribute Retrieval

3281 The PDP SHALL request the values of attributes in the request context from the context handler. The

3282 PDP SHALL reference the attributes as if they were in a physical request context document, but the

3283 context handler is responsible for obtaining and supplying the requested values by whatever means it

3284 deems appropriate.

Proposal

7.3.5 Attribute Retrieval

The PDP SHALL request the values of attributes in the request context from the context handler. The context handler MAY also add attributes to the request context without the PDP requesting them. The PDP SHALL reference the attributes as if they were in a physical request context document, but the context handler is responsible for obtaining and supplying the requested values by whatever means it deems appropriate, including by retrieving them from one or more Policy Information Points.

Thanks,

Ray

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