OASIS eXtensible Access Control Markup Language (XACML) TC

Notes from Focus Group 14 August 2003

  • 1.  Notes from Focus Group 14 August 2003

    Posted 08-14-2003 17:39
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    Subject: Notes from Focus Group 14 August 2003


    Present:
      Frank Siebenlist
      Anne Anderson
      Hal Lockhart
      Steve Crocker
    
    There was no prior agenda, so topics discussed were at the
    initiative of the attendees.
    
    1. SAML Authz Req/Resp sidebar at SAML F2F
    
    Frank Siebenlist expressed a preference for holding the proposed
    working session between OGSA and XACML TC people on Tuesday or
    Wednesday, rather than on Monday.  Anne has sent this preference
    to the SSTC chairs.
    
    Frank mentioned that Rebekah Lepro (bekah@nas.nasa.gov, working
    on Grid projects at NASA Ames) has a lot of experience with the
    difficulty of mapping Attributes between the SAML Attribute
    format and the XACML Request format.  He hopes this can also be
    addressed in SAML 2.0.
    
    2. New web services policy language use case
    
    Frank described a use case that occurs in the Grid environment
    that is not currently included in the "Web-services policy
    language use-Cases and requirements" document:
    
      Schedulers/Brokers match scientists needing computational
      resources (CPU cycles, disk space, bandwidth) with sites
      offering such resources.  Each site has its own policies
      regarding which scientists are authorized to use computational
      resources at that sites, and what limits exist on the use of
      such resources.  This means each site must have a way of
      publishing its access requirements for use by the
      Schedulers/Brokers.
    
    It looks like the XACML Profile for Web-services could handle
    this.  It might be easiest if the Profile allowed a published
    policy or rule to include attributes of the applicable subjects
    in the Target.
    
    Frank said WS-Policy can't handle such a requirement.  It is
    clearly in the access control domain, so it is XACML's business
    to address it.
    
    3. XACML Policy in SAML Response/Request Conditions
    
    Hal asked for the use cases behind XACML 2.0 Work Items #16 and
    17.
    
    Anne said these came from Grid requirements, but also come up in
    support of authorization decision optimization.
    
    Use case for XACML Policy in Conditions of AuthzDecision:
    
    An XACML Policy might be included in the response to an SAML
    AuthorizationDecisionQuery in cases where a PDP associated with
    the Initiator of a Request was unable to completely evaluate the
    policy due to lack of information, but where another PDP
    associated with the Resource has the missing information (but
    perhaps not other information that was available to the first
    PDP).  If the first PDP can return an AuthorizationDecision of
    the form "Permit IF Condition", where the Condition contains a
    partially evaluated policy stripped down to just the predicates
    involving the missing information.
    
    Use case#1 for XACML Policy in Conditions of AuthzDecisionQuery:
    
    Used by a resource that has received a Request for services along
    with an AuthorizationDecision of the above form.  It passes the
    Condition containing the remaining policy to its own PDP for
    evaluation.
    
    Use case#2 for XACML Policy in Conditions of AuthzDecisionQuery:
    
    A resource may have its own policy.  It receives requests
    directly from subjects.  It passes its policy in the to the PDP
    as part of the Conditions element of the SAML
    AuthzDecisionQuery.
    
    4. XACML TC FAQ
    
    Hal mentioned that he has a message for the DSS TC that is sent
    in response to requests for membership.  This message explains
    that the requester should change their member status from
    Prospective Member to Observer if they do not intend to
    participate regularly in meetings.
    
    Anne
    -- 
    Anne H. Anderson             Email: Anne.Anderson@Sun.COM
    Sun Microsystems Laboratories
    1 Network Drive,UBUR02-311     Tel: 781/442-0928
    Burlington, MA 01803-0902 USA  Fax: 781/442-1692
    
    


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