Example Authorization Requests and Policies

The following examples of policies and associated requests are meant to illustrate some of the possible policies, requests, and resulting authorization decisions.

Note, the examples below use the PAP's simplified policy language to express policies. So please review this syntax, before proceeding, if you are not yet familiar with it.

User Based Authorization

In this example one user is permitted, and one is denied, the ability to submit jobs on the CERN CE resource. Each user is identified by a X.509 subject DN. This example also shows how identity-based access control is simply a degenerate case of attribute-based access control.

Authorization Policy

resource "http://cern.ch/authz/ce1" {
   action "http://cern.ch/authz/actions/ce-submit" {
      rule permit {
         subject="CN=John Doe,OU=Standard Commercial Certificate,O=Acme,L=Zuerich,ST=Zuerich,C=CH"
      }
      rule deny {
         subject="CN=Jane Smith,OU=Standard Commercial Certificate,O=Acme,L=Zuerich,ST=Zuerich,C=CH"
      }
   }
}

Requests

A request of:
  • resource attributes:
    • id: urn:oasis:names:tc:xacml:1.0:resource:resource-id, value: http://cern.ch/authz/ce1
    • any other attributes
  • action attributes:
    • id: urn:oasis:names:tc:xacml:1.0:action:action-id, value: http://cern.ch/authz/actions/ce-submit
    • any other attributes
  • subject attributes:
    • id: urn:oasis:names:tc:xacml:1.0:subject:subject-id, value: CN=John Doe,OU=Standard Commercial Certificate,O=Acme,L=Zuerich,ST=Zuerich,C=CH

would result in an authorization decision of permit because the given resource and actions IDs match what was given in the policy and the subject ID DN matches what was given in the permit rule. If the request contained any other resource, action, or subject attribute these would be ignored since the policy does not reference them. If the request had not contained the attributes listed it would have resulted in an authorization decision of not applicable since no policy would have matched the request.

A request of:

  • resource attributes:
    • id: urn:oasis:names:tc:xacml:1.0:resource:resource-id, value: http://cern.ch/authz/ce1
    • any other attributes
  • action attributes:
    • id: urn:oasis:names:tc:xacml:1.0:action:action-id, value: http://cern.ch/authz/actions/ce-submit
    • any other attributes
  • subject attributes:
    • id: urn:oasis:names:tc:xacml:1.0:subject:subject-id, value: CN=Jane Smith,OU=Standard Commercial Certificate,O=Acme,L=Zuerich,ST=Zuerich,C=CH

would result in an authorization decision of deny since the resource and action IDs match and this time the subject ID matches the requirement for the deny rule.

Note, in the second request, if the subject ID had contained at least the values CN=John Doe ,OU=Standard Commercial Certificate,O=Acme,L=Zuerich,ST=Zuerich,C=CH and CN=Jane Smith,OU=Standard Commercial Certificate,O=Acme,L=Zuerich,ST=Zuerich,C=CH the authorization decision would have been permit since the permit rule would have been evaluated first and would have returned the result.

Per-VO Pilot Job Authorization Policy

This example shows a policy that allows pilot jobs from one VO, atlas, and denies pilot jobs from others. It also demonstrates rules that rely on more than one attribute.

Authorization Policy

resource "http://cern.ch/authz/ce1" {
   action "http://cern.ch/authz/actions/ce-submit" {
      rule permit {
         vo="atlas"
         pilot-job="true"
      }
      rule deny {
         pilot-job="true"
      }
   }
}

Requests

A request of:
  • resource attributes:
    • id: urn:oasis:names:tc:xacml:1.0:resource:resource-id, value: http://cern.ch/authz/ce1
    • any other attributes
  • action attributes:
    • id: urn:oasis:names:tc:xacml:1.0:action:action-id, value: http://cern.ch/authz/actions/ce-submit
    • any other attributes
  • subject attributes:
    • id: http://authz-interop.org/xacml/subject/vo, value: atlas
    • id: http://example.org/authz/attribute/pilot-job, value: true
would result in a decision of permit since the atlas VO is permitted to submit pilot jobs. A request where the VO was lhcb or cms would result in a decision of deny since these VOs are not permitted to submit jobs.

A request of: * resource attributes:

    • id: urn:oasis:names:tc:xacml:1.0:resource:resource-id, value: http://cern.ch/authz/ce1
    • any other attributes
  • action attributes:
    • id: urn:oasis:names:tc:xacml:1.0:action:action-id, value: http://cern.ch/authz/actions/ce-submit
    • any other attributes
  • subject attributes:
    • id: http://authz-interop.org/xacml/subject/vo, value: atlas
would result in a decision of not applicable since the current policy indicates that only jobs from the VO atlas that are also pilot jobs are permitted. Requests without a pilot-job attribute are not addressed by this policy.
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Topic revision: r3 - 2009-10-19 - unknown
 
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