OASIS eXtensible Access Control Markup Language (XACML) TC

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attribute with AttributeId="...:subject-id" containing the "identity"of a subject ?

  • 1.  attribute with AttributeId="...:subject-id" containing the "identity"of a subject ?

    Posted 04-04-2005 23:36
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    Subject: attribute with AttributeId="...:subject-id" containing the "identity"of a subject ?


    In XACML, we don't seem to distinguish the attributes by type as being 
    either identity-attributes or "just-attributes", where the identity 
    attributes would be special as they would uniquely identify that 
    subject/resource/action.
    
    Instead we use this special subject-id/resource-id/action-id AttributeId 
    that fullfills a similar role.
    
    However, if a requester comes in, the request context creation code has 
    to "know" what identifier to use for that subject-id, otherwise it 
    wouldn't match the one used in the policy matching rules.
    
    So, one should know to use a X509 subject-name's DN, or the public key, 
    and if that same user authenticates tomorrow with kerberos, then 
    principal@realm will only work if you "know" to use an associated 
    identity assertion that federates those names and to fill-in the right 
    one for that subject-id.
    
    We have the added issue that when issuers are associated with policies, 
    then we need the issuer's attributes to use a subject-id such that we 
    can match it to additional attributes that may be available when that 
    issuer is substituted by the PDP in the xacml-context:Request.
    
    As an alternative, could we maybe label the attributes with a boolean 
    "Identifier", such that we could use that in our matching functions 
    like: see if any of the subject's attributes for which 
    "Identifier==TRUE", match my subject-id value.
    
    Having such an "Identifier" attribute for Attribute, would also allow 
    you to specify a true XACML Attribute assertion as a collection of 
    Attributes with at least one Attribute for which "Identifier==TRUE".
    (I guess the latter would also be possible if the attribute set included 
    one for which AttributeId=="...:subject-id")
    
    -Frank.
    
    
    -- 
    Frank Siebenlist               franks@mcs.anl.gov
    The Globus Alliance - Argonne National Laboratory
    
    


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