AW: Issue #4: Context Handler - Proposal

Hi Ray, all,

 

I like your edits and I think that they point out the flexibilities of XACML Context Handlers’ behavior. I would even go one step further and add some text blocks in these sentences, that highlight
 the option, that Context Handlers can also call Obligation Handlers. I have seen many use cases/requirements where XACML Context Handlers need to call Obligation Handlers to discharge the obligations included in an XACML authorization decision. Note that in
 these scenarios it was not possible/appropriate to discharge the obligations in the PEP (assuming that the Context Handler is not included in the PEP), as the Obligations had an effect on the representation of intercepted Web Service messages included in the
 XACML authorization decision request (which is only available in the Context Handler and not in the PEP).

 

Some background information on these use cases:

The underlying requirement of these use cases is to enforce rewrite effects on intercepted Web Service requests (or responses). Enforcing rewrite effects is needed in cases where you need to apply
 access restrictions on intercepted Web Service requests that shall e.g. limit read requests to certain objects (e.g. rewrite the query “select * from person” to the authorized query “select * from person
WHERE person.id = dereferenced-subject-id-attr”). The concepts behind this is a more general and DBMS independent form of what can e.g. be done through Oracle’s VPD mechanism. The attached word document describes the details how to use the XACML
 obligation mechanism to achieve a XACML policy controlled rewriting of intercepted Web Service messages. Feel free to contact me if you need further explanations. One more note: a very similar approach can be taken to generate sub-requests that will be forwarded
 to the PIP and tell him how to retrieve more data in order to avoid/solve indeterminate responses.

 

Best regards

Jan

 

PS: regrets that I can only irregularly attend the teleconferences but they take place during our family dinner time.

 

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Von:  [mailto:]
Im Auftrag von 

Gesendet: Freitag, 24. Februar 2012 16:31

An: 

Betreff: [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

 

Attachment:
example_rewrite-rule.pdf

Description: example_rewrite-rule.pdf

Attachment:
Details on how to use the XACML obligation mechanism to achieve a rewriting of intercepted Web Service messages.pdf

Description: Details on how to use the XACML obligation mechanism to achieve a rewriting of intercepted Web Service messages.pdf