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Subject: Re: [xacml] Groups - XACML v3.0 Obligation and Advice Authority (OAA) Profile Version 1.0 uploaded

Hi Mohammad,

On 28/05/2013 2:17 PM, Mohammad Jafari wrote:
Thanks Steven for posting this.

In Section 2 there is a use-case which motivates the profile. To summarize, your use-case requires:

-Bob can “create”, “read”, “update” and “destroy” documents.

-Alice can only “read” document.

-“Create”, “update” and “destroy” by anyone must be logged.

-Any operation on sensitive resources must take approval.

You have argued that adding the obligations requires splitting the authorization rules, but I don’t see why
this is necessary. Correct me if I am wrong but I think these requirements can be formulated by the
following PolicySet without splitting the rules:

(I have attached a PDF if you are reading in plain text):


  * PolicySet 1 (deny-overrides)
      o PolicySet 1.1 (deny-unless-permit)
          + Policy: 1.1.1 (deny-overrides)
              # If Resource.type=*document:*
              # Rule:
                  * Permit, if Subject.id=*Alice,* and Action.id=*read*
              # Rule:
                  * Permit, if**Subject.id=*Bob* and Action.id in {*create*, *read*, *update*, *destroy*}
      o Policy: 1.2 (deny-overrides)
          + Rule 1.2.1: CUP-log
              # Permit if Action.id in {*create*, *update*, *destroy* }, and Resource.type=*document:*
              # Obligation (OnPermit): log
          + Rule 1.2.2: Sensitive-docs
              # Permit if Resource.approval-required*=true *and**Action.id in {*create*, *read*, *update*,
              # Obligation (OnPermit): approval-required


Suppose Bob wants to update a sensitive document. This will match policyset 1, 1.1, and 1.1.1 and causes
rule to evaluate, permitting the access. But since the overarching combining algorithm is
deny-overrides, policy 1.2 is also evaluated. Again since the combing algorithm is deny-override, both rules
are evaluated triggering both obligations to log and take approval.

Any other authorization rule can go under policyset 1.1 and any other obligation rule can go under policy 1.2.

PolicySet 1 isn't entirely equivalent to my example because it turns NotApplicable and
Indeterminate decisions into Deny decisions, so it depends on an assumption that the
PEPs were deny-biased. However, it isn't a general solution because it doesn't support
deny obligations (and it would suppress any useful missing-attribute errors). I tried
a range of variations on the same theme to support both permit and deny obligations,
but the best I could come up with was an arrangment that had the unfortunate side-effect
of turning NotApplicable and Indeterminate decisions into Deny decisions with obligations.



Mohammad Jafari, Ph.D.

Security Architect, Edmond Scientific Company

*From:*xacml@lists.oasis-open.org [mailto:xacml@lists.oasis-open.org] *On Behalf Of *Steven Legg
*Sent:* Monday, May 27, 2013 7:56 PM
*To:* xacml@lists.oasis-open.org
*Subject:* [xacml] Groups - XACML v3.0 Obligation and Advice Authority (OAA) Profile Version 1.0 uploaded

/Submitter's message/
This is the initial draft for the Obligation and Advice Authority Profile.
-- Dr. Steven Legg

*Document Name*: XACML v3.0 Obligation and Advice Authority (OAA) Profile Version 1.0


This specification defines a new XACML system entity, the Obligation and
Advice Authority (OAA), which makes obligations and advice easier to manage
by separating the determination of applicable obligations and advice from
the determination of the access decision by the PDP.
Download Latest Revision
Public Download Link <https://www.oasis-open.org/committees/document.php?document_id=49348&wg_abbrev=xacml>


*Submitter*: Dr. Steven Legg
*Group*: OASIS eXtensible Access Control Markup Language (XACML) TC
*Folder*: Specifications and Working Drafts
*Date submitted*: 2013-05-27 18:56:15

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