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OASIS eXtensible Access Control
Markup Language (XACML)
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Working Draft 16a, 10 September 2002
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Document identifier: draft-xacml-specification-16.doc
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Location: http://www.oasis-open.org/committees/xacml/docs/
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Send comments to: xacml-comment@lists.oasis-open.org
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Editors:
Simon Godik, Overxeer (simon.godik@overxeer.com)
Tim Moses, Entrust (tim.moses@entrust.com)
Contributors:
Anne Anderson, Sun Microsystems
Bill Parducci, Overxeer
Carlisle Adams, Entrust
Daniel Engovatov, Crosslogix
Don Flinn, Hitachi
Ernesto Damiani, University of Milan
James MacLean, Affinitex
Hal Lockhart, Entegrity
Ken Yagen, Crosslogix
Konstantin Besnozov, Hitachi
Michiharu Kudo, IBM, Japan
Pierangela Samarati, University of Milan
Polar Humenn, Syracuse University
Sekhar Vajjhala, Sun Microsystems
Gerald Brose, Xtradyne
Abstract:
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This specification defines an XML schema for an extensible access-control policy
language.
Status:
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This version of the specification is a working draft of the committee. As such, it is expected
to change prior to adoption as an OASIS standard.
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If you are on the xacml@lists.oasis-open.org list for committee members, send comments
there. If you are not on that list, subscribe to the xacml-comment@lists.oasis-open.org list
and send comments there. To subscribe, send an email message to xacml-commentrequest@lists.oasis-open.org with the word "subscribe" as the body of the message.
draft-xacml-specification-16a.doc
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Copyright (C) OASIS Open 2002. All Rights Reserved.
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Table of contents
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1.
Glossary (non-normative)
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1.1.
Preferred terms
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1.2.
Related terms
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2.
Introduction (non-normative)
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2.1.
Notation
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2.2.
Background
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2.3.
Requirements
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2.4.
Rule and policy combining
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2.5.
Combining algorithms
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2.6.
Policies based on subject and resource attributes
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2.7.
Policies based on resource contents
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2.8.
Operators
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2.9.
Policy distribution
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2.10.
Policy indexing
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2.11.
Abstraction layer
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2.12.
Actions performed in conjunction with enforcement
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2.13.
Schema organization and namespaces
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3.
Examples (non-normative)
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3.1.
Example one
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3.2.
Example two
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3.2.1
Example medical record instance
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3.2.2
Example request context
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3.2.3
Example plain-language rules
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3.2.4
Example XACML rule instances
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4.
Models (non-normative)
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4.1.
Data-flow model
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4.2.
XACML context
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4.3.
Policy language model
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4.3.1
Rule
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4.3.2
Policy
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4.3.3
Policy set
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5.
Functional requirements (normative)
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5.1.
Policy Decision Point
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5.2.
Hierarchical resources
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6.
Policy syntax (normative, with the exception of the schema fragments)
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6.1.
Element <PolicySet>
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6.2.
Element <Description>
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6.3.
Element <PolicySetDefaults>
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6.4.
Element <Target>
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6.5.
Element <Subjects>
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6.6.
Element <Subject>
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6.7.
Element <SubjectMatch>
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6.8.
Element <Resources>
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6.9.
Element <Resource>
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6.10.
Element <ResourceMatch>
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6.11.
Element <Actions>
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6.12.
Element <Action>
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6.13.
Element <ActionMatch>
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6.14.
Element <PolicySetIdReference>
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6.15.
Element <PolicyIdReference>
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6.16.
Element <Policy>
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6.17.
Element <Rule>
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6.18.
Simple type EffectType
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6.19.
Element <Condition>
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6.20.
Element <Apply>
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6.21.
Complex type AttributeDesignatorType
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6.22.
Element <SubjectAttributeDesignator>
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6.23.
Element <ResourceAttributeDesignator>
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6.24.
Element <ActionAttributeDesignator>
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6.25.
Element <EnvironmentAttributeDesignator>
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6.26.
Element <SubjectAttributeDesignatorWhere>
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6.27.
Element <AttributeSelector>
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6.28.
Element <AttributeValue>
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6.29.
Element <Obligations>
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6.30.
Element <Obligation>
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6.31.
Element <AttributeAssignment>
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Context syntax (normative with the exception of the schema fragments)
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7.1.
Element <Request>
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7.2.
Element <Subject>
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7.3.
Element <Resource>
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7.4.
Element <ResourceContent>
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7.5.
Element <Action>
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7.6.
Element <Environment>
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7.7.
Element <Attribute>
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7.8.
Element <AttributeValue>
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7.9.
Element <Response>
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7.10.
Element <Result>
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7.11.
Element <Decision>
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7.12.
Element <Status>
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7.13.
Element <StatusCode>
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7.14.
Element <StatusMessage>
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7.15.
Element <StatusDetail>
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8.
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XACML extensibility points (non-normative)
8.1.
9.
URIs
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Security and privacy considerations (non-normative)
9.1.
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Threat model
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9.1.1
Unauthorized disclosure
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9.1.2
Impersonation
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9.1.3
Message replay
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9.1.4
Message insertion
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9.1.5
Message deletion
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9.1.6
Message modification
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9.1.7
Resource matching
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9.1.8
Negative rules
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9.2.
Safeguards
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9.2.1
Authentication
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9.2.2
Confidentiality
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9.2.3
Policy integrity
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9.2.4
Message freshness
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9.2.5
Policy identifiers
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9.2.6
Trust model
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9.2.7
Privacy
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10.
Conformance (normative)
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10.1.
Introduction
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10.2.
XACML test suite
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10.3.
Conformance tables
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10.3.1
Schema elements
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10.3.2
Algorithms
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10.3.3
Identifiers
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10.3.4
Function identifier
References
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11.
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Appendix A. Function names and legal type combinations
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A.1.
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Appendix B. XACML identifiers (normative)
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B.1.
XACML namespaces
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B.2.
Authentication locality
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B.3.
Access subject categories
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B.4.
XACML functions
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B.5.
Data types
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Functions
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B.5.1.
X.500 distinguished name
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B.5.2.
RFC822 Name
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B.5.3.
Unix file-system path
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B.5.4.
Numeric
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B.6.
Environment attributes
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B.7.
Subject attributes
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B.8.
Resource attributes
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B.9.
Status codes
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B.10.
Combining algorithms
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B.10.
Identifiers used only in XACML conformance tests
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B.11.
Attributes used in examples
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B.12.
Actions used in examples
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Appendix C. Combining algorithms (normative)
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C.1.
Deny-overrides
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C.2.
Permit-overrides
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C.3.
First-applicable
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Appendix D. Acknowledgments
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Appendix E. Revision history
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Appendix F. Notices
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1. Glossary (non-normative)
1.1. Preferred terms
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Access - Performing an action
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Access control - Controlling access in accordance with a policy
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Action - An operation on a resource
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Applicable policy - The policy that governs access for a specific decision request
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Attribute - Characteristic of a subject, resource, action or environment that may be referenced
in a predicate or target
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Authorization decision - The result of evaluating applicable policy. A function that evaluates to
"permit, deny or indeterminate", and (optionally) a set of obligations
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Condition - An expression of predicates. A function that evaluates to "True" or "False"
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Context - The canonical representation of a decision request and an authorization decision
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Decision request - The request by a PEP to a PDP to render an authorization decision
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Effect - The intended consequence of a satisfied condition (either "Permit" or "Deny")
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Environment - The set of attributes that are independent of a particular subject, resource or
action
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Obligation - An operation specified in a policy or policy set that should be performed in
conjunction with the issuance of an authorization decision
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Policy - A set of rules, an identifier for the rule-combining algorithm and (optionally) a set of
obligations
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Policy administration point (PAP) - The system entity that creates a policy or policy set
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Policy-combining algorithm - The procedure for combining the target, obligations and
conditions from multiple policies
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Policy decision point (PDP) - The system entity that evaluates applicable policy and renders an
authorization decision
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Policy enforcement point (PEP) - The system entity that performs access control, by enforcing
authorization decisions
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Policy information point (PIP) - The system entity that acts as a source of attribute values
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Policy set - A set of policies, other policy sets, a policy-combining algorithm and (optionally) a
set of obligations
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Predicate - A statement about attributes whose truth can be evaluated
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Resource - Data, service or system component
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Rule - A target, an effect and a condition
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Rule-combining algorithm - The procedure for combining the target, effect and conditions from
multiple rules
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Subject - An actor whose attributes may be referenced by a predicate
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Target - The set of decision requests, identified by definitions for resource, subject and action,
that a rule, policy or policy set is intended to evaluate
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1.2. Related terms
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In the field of access control and authorization there are several closely related terms in common
use. For purposes of precision and clarity, certain of these terms are not used in this specification.
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For instance, the term attribute is used in place of the terms: group and role.
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In place of the terms: privilege, permission, authorization, entitlement and right, we use the
term rule.
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The term object is also in common use, but we use the term resource in this specification.
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Requestors and initiators are covered by the term subject.
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2. Introduction (non-normative)
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2.1. Notation
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This specification contains schema conforming to W3C XML Schema and normative text to
describe the syntax and semantics of XML-encoded policy statements.
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The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD",
"SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this specification are to be
interpreted as described in IETF RFC 2119 rfc2119:
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"they MUST only be used where it is actually required for interoperation or to limit
behavior which has potential for causing harm (e.g., limiting retransmissions)"
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These keywords are thus capitalized when used to unambiguously specify requirements over
protocol and application features and behavior that affect the interoperability and security of
implementations. When these words are not capitalized, they are meant in their natural-language
sense.
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Listings of XACML schemas appear like this.
Example code listings appear like this.
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Conventional XML namespace prefixes are used throughout the listings in this specification to
stand for their respective namespaces as follows, whether or not a namespace declaration is
present in the example:
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The prefix saml: stands for the SAML assertion namespace.
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The prefix ds: stands for the W3C XML Signature namespace.
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The prefix xs: stands for the W3C XML Schema namespace.
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This specification uses the following typographical conventions in text: <XACMLElement>,
<ns:ForeignElement>, Attribute, Datatype, OtherCode. Terms in italic bold-face are
intended to have the meaning defined in the Glossary.
2.2. Background
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The "economics of scale" have driven computing platform vendors to develop products with very
generalized functionality, so that they can be used in the widest possible range of situations. "Out
of the box", these products have the maximum possible privilege for accessing data and executing
software, so that they can be used in as many application environments as possible, including
those with the most permissive security policies. In the more common case of a relatively
restrictive security policy, the platform's inherent privileges must be constrained, by configuration.
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The security policy of a large enterprise has many elements and many points of enforcement.
Elements of policy may be managed by the Information Systems department, by Human
Resources, by the Legal department and by the Finance department. And the policy may be
enforced by the extranet, mail, WAN and remote-access systems; platforms which inherently
implement a permissive security policy. The current practice is to manage the configuration of each
point of enforcement independently in order to implement the security policy as accurately as
possible. Consequently, it is an expensive and unreliable proposition to modify the security policy.
And, it is virtually impossible to obtain a consolidated view of the safeguards in effect throughout
the enterprise to enforce the policy. At the same time, there is increasing pressure on corporate
and government executives from consumers, shareholders and regulators to demonstrate "best
practice" in the protection of the information assets of the enterprise and its customers.
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For these reasons, there is a pressing need for a common language for expressing security policy.
If implemented throughout an enterprise, a common policy language allows the enterprise to
manage the enforcement of all the elements of its security policy in all the components of its
information systems. Managing security policy may include some or all of the following steps:
writing, reviewing, testing, approving, issuing, combining, analyzing, modifying, withdrawing,
retrieving and enforcing policy.
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XML is a natural choice as the basis for the common security-policy language, due to the ease with
which its syntax and semantics can be extended to accommodate the unique requirements of this
application, and the widespread support that it enjoys from all the main platform and tool vendors.
2.3. Requirements
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The basic requirements of a policy language for expressing information system security policy are:
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To provide a method for combining individual rules and policies into a single policy set that
applies to a given action.
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To provide a method for flexible definition of the procedure by which rules and policies are
combined.
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To provide a method for basing an authorization decision on attributes of the subject and
resource.
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To provide a method for basing an authorization decision on the contents of an information
resource.
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To provide a set of logical and mathematical operators on attributes of the subject, resource
and environment.
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To provide a method for distribution of policies by means of an enterprise repository, or their
attachment to the resources to which they apply.
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To provide a method for rapidly identifying the policy that applies to a given action, based
either on the identity or attributes of either the subject or the resource.
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To provide an abstraction-layer that insulates the policy-writer from the details of the application
environment.
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To provide a method for specifying a set of actions that must be performed in conjunction with
policy enforcement.
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The motivation behind XACML is to express these well-established ideas in the field of accesscontrol policy using an extension language of XML. The XACML solutions for each of these
requirements are discussed in the following sections.
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2.4. Rule and policy combining
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The complete policy applicable to a particular decision request may be composed of a number of
individual rules or policies, specified by different policy writers. For instance, in a personal privacy
application, the owner of the personal information may define certain aspects of disclosure policy,
whereas the enterprise that holds the information may define certain other aspects. In order to
render an authorization decision, it must be possible to combine the two separate policies to
form the single policy applicable to the request.
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XACML defines three top-level policy elements: <Rule>, <Policy> and <PolicySet>. The
<Rule> element contains a boolean expression that can be evaluated in isolation, but that is not
intended to be passed between the major actors in the XACML architectural model. So, it is not
intended to form the basis of an authorization decision by itself. It is intended to exist in isolation
only within an XACML PAP, where it may form the basic unit of management, and be re-used in
multiple policies.
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The <Policy> element contains a set of <Rule> elements and a specified procedure for
combining the results of their evaluation. It is the basic unit of policy that may be exchanged
between the major actors in the XACML architectural model, and so it is intended to form the basis
of an authorization decision.
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The <PolicySet> element contains a set of <Policy> or other <PolicySet> elements and a
specified procedure for combining the results of their evaluation. It is the standard means for
combining separate policies into a single combined policy.
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Hinton et al [Hinton94] discuss the question of the compatibility of separate policies applicable to
the same decision request.
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2.5. Combining algorithms
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XACML defines a number of combining algorithms that can be identified by a
RuleCombiningAlgId or PolicyCombiningAlgId attribute of the <Policy> or <PolicySet>
elements, respectively. The rule-combining algorithm defines a procedure for arriving at an
authorization decision given the individual results of evaluation of a set of rules. Similarly, the
policy-combining algorithm defines a procedure for arriving at an authorization decision given
the individual results of evaluation of a set of policies. Standard combining algorithms are defined
for:
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Deny-overrides,
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
Permit-overrides and
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
First applicable.
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In the first case, if a single <Rule> or <Policy> element is encountered that evaluates to "Deny",
then, regardless of the evaluation result of the other <Rule> or <Policy> elements in the
applicable policy, the combined result is "Deny". Likewise, in the second case, if a single "Permit"
result is encountered, then the combined result is "Permit". In the case of the "First applicable"
combining algorithm, the combined result is the same as the result of evaluating the first rule in the
list of rules whose target is applicable to the decision request.
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Users of the standard may, if necessary, define their own combining algorithms. However, this
approach is harmful to interoperability. User defined combining algorithms should specify how the
combined result is to be derived from separate evaluation of the individual <Rule> or <Policy>
elements.
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2.6. Policies based on subject and resource attributes
Another common requirement is to base an authorization decision on some characteristic of the
subject other than its identity. Perhaps, the most common application of this idea is the subject's
role [RBAC]. XACML provides facilities to support this approach. Attributes of subjects are
identified by the <SubjectAttributeDesignator> element. This element may contain a URN
that identifies the attribute, or an XPath expression over the request context to identify a particular
subject attribute value by its location in the context (see section 2.11 for an explanation of
context). XACML provides a standard way to reference the attributes defined in the LDAP series
of specifications [LDAP]. This is intended to encourage implementers to use standard attribute
identifiers for some common subject attributes.
2.7. Policies based on resource contents
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In many applications, it is required to base an authorization decision on data contained in the
information resource to which access is requested. For instance, a common component of privacy
policy is that a person should be allowed to read records for which he or she is the subject. The
corresponding policy must contain a reference to the subject identified in the information resource
itself.
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XACML provides facilities for doing this when the information resource can be represented as an
XML document. The <AttributeSelector> element may contain an XPath expression over the
request context to identify data in the information resource to be used in the policy evaluation.
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In cases where the information resource is not an XML document, specified attributes of the
resource can be referenced.
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2.8. Operators
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Information security policies operate upon attributes of subjects and resources and the action
to be performed on the resource in order to arrive at an authorization decision. In the process of
arriving at the authorization decision, attributes of many different types may have to be
compared or computed. For instance, in a financial application, a person's available credit may
have to be calculated by adding their credit limit to their account balance. The result may then have
to be compared with the transaction value. This sort of situation gives rise to the need for
arithmetic operations on attributes of the subject (account balance and credit limit) and the
resource (transaction value).
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Even more commonly, a policy may identify the set of roles that are permitted to perform a
particular action. The corresponding operation involves checking whether there is a non-empty
intersection between the set of roles occupied by the subject and the set of roles identified in the
policy. Hence the need for set operations.
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XACML includes a number of built-in functions and a method of adding non-standard functions.
These functions may be applied recursively to build arbitrarily complex expressions. This is
achieved with the <Apply> element. The <Apply> element has an XML attribute called
FunctionId that identifies the function to be applied to the contents of the element. Each
standard function is defined for specific argument type combinations, and its return value is also
specified. Therefore, type consistency of the policy can be checked at the time the policy is
written. And, the types of the data values presented in the request context can be checked against
the values expected by the policy to ensure a predictable outcome.
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In addition to operators on numerical and set arguments, operators are defined for date, time and
duration arguments. Date operations are notoriously difficult to standardize, due to local rules for
handling weekends, statutory holidays, etc.. Therefore, the first level of XACML conformance does
not require support for date operations.
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Relationship operators (equality and inequality) are also defined for a number of data-types,
including the RFC822 and X.500 name-forms, strings, URIs, etc..
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Also noteworthy are the operators over boolean data types, which permit the logical combination of
predicates in a rule. For example, a rule may contain the statement that access may be
permitted during business hours AND from a terminal on business premises.
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The XACML method of representing functions borrows heavily from MathML [MathML].
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2.9. Policy distribution
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In a distributed system, individual policy statements may be written by several policy writers and
enforced at several enforcement points. In addition to facilitating the collection and combination of
independent policy components, this approach allows policies to be updated as required. XACML
policy statements may be distributed in any one of a number of ways. But, XACML does not
describe any normative way to do this. Regardless of the means of distribution, PDPs are
expected to confirm, by examining the policy's <Target> element that the policy is applicable to
the decision request that it is processing.
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<Policy> elements may be attached to the information resources to which they apply, as
described by Perritt [Perritt93]. Alternatively, <Policy> elements may be maintained in a central
location from which they are retrieved for evaluation. In such cases, the applicable policy may be
referenced by an identifier or locator closely associated with the information resource.
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2.10. Policy indexing
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For efficiency of evaluation and ease of management, the overall security policy in force across an
enterprise may be expressed as multiple independent policy components. In this case, it is
necessary to identify and retrieve the applicable policy statement and verify that it is the correct
one for the requested action before evaluating it. This is the purpose of the <Target> element in
XACML.
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Two approaches are supported:
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1. Policy statements may be stored in a database, whose data-model is congruent with that of the
<Target> element. The PDP should use the contents of the decision request that it is
processing to form the database read command by which the applicable policy statement is
retrieved. Nevertheless, the PDP should still evaluate the <Target> element of the policy
statement returned as a result of the read command as defined by the XACML specification.
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2. Alternatively, the PDP may evaluate the <Target> element from each of the policies that it has
available to it, in the context of a particular decision request, in order to identify the single policy
that is applicable to that request.
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In either case, it is the policy writer's responsibility to ensure that only one policy statement applies
to a particular decision request.
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The use of constraints limiting the applicability of a policy were described by Sloman [Sloman94].
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2.11. Abstraction layer
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PEPs come in many forms. For instance, a PEP may be part of a remote-access gateway, part of
a Web server or part of an email user-agent, etc.. It is unrealistic to expect that all PEPs in an
enterprise do currently, or will in the future, issue decision requests to a PDP in a common format.
Nevertheless, a particular policy may have to be enforced by multiple PEPs. It would be inefficient
to force a policy writer to write the same policy several different ways in order to accommodate the
format requirements of each PEP. Therefore, there is a need for a canonical form of the request
and response handled by an XACML PDP. This canonical form is called the XACML "Context". Its
syntax is defined in XML schema.
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Naturally, XACML-conformant PEPs may issue requests and receive responses in the form of an
XACML context. But, where this situation does not exist, an intermediate step is required to
convert between the request/response format understood by the PEP and the XACML context
format understood by the PDP.
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The benefit of this approach is that policies may be written and analyzed independent of the
specific environment in which they are to be enforced.
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In the case where the native request/response format is specified in XML Schema (e.g. a SAMLconformant PEP), the transformation between the native format and the XACML context may be
specified in the form of an Extensible Stylesheet Language Transformation [XSLT].
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Similarly, in the case where the resource to which access is requested is an XML document, the
resource itself may be included in, or referenced by, the request context. Then, through the use
of XPath expressions [XPath] in the policy, values in the resource may be included in the policy
evaluation.
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2.12. Actions performed in conjunction with enforcement
In many applications, policies specify actions that MUST be performed, either instead of, or in
addition to, actions that MAY be performed. This idea was described by Sloman [Sloman94].
XACML provides facilities to specify actions that MUST be performed in conjunction with policy
evaluation in the <Obligations> element. There are no standard definitions for these actions in
version 1.0 of XACML. Therefore, bilateral agreement between a PAP and the PEP that will
enforce its policies is required for correct interpretation. PEPs that conform with v1.0 of XACML
are required to deny access unless they understand all the <Obligations> elements associated
with the applicable policy. <Obligations> elements are returned to the PEP for enforcement.
2.13. Schema organization and namespaces
The XACML policy syntax is defined in a schema associated with the following XML namespace:
urn:oasis:names:tc:xacml:1.0:policy
The XACML context syntax is defined in a schema associated with the following XML namespace:
urn:oasis:names:tc:xacml:1.0:context
XACML functions have the following namespace prefix.
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urn:oasis:names:tc:xacml:1.0:function
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Note: The XACML namespace names are temporary and may change when
XACML 1.0 is finalized.
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The XML Signature XMLSigXSD is imported into the XACML schema and is associated with the
following XML namespace:
http://www.w3.org/2000/09/xmldsig#
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3. Examples (non-normative)
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This section contains two examples of the use of XACML for illustrative purposes. The first example
is a relatively simple one to illustrate the function of target, context, matching functions and
subject attributes. The second example additionally illustrates the use of the rule-combining
algorithm and obligations.
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3.1. Example one
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Assume that a corporation named Medi Corp (medico.com) has an access control policy that
states, in English:
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Any user with an e-mail name in the "medico.com" namespace is allowed to perform any action on
any resource.
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In XACML, this policy is expressed as follows:
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<?xml version=1.0" encoding="UTF-8"?>
<Policy
xmlns="urn:oasis:names:tc:xacml:1.0:context"
xmlns:function="urn:oasis:names:tc:xacml:1.0:function"
xmlns:identifier="urn:oasis:names:tc:xacml:1.0"
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xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="urn:oasis:names:tc:xacml:1.0:policy
http://www.oasis-open.org/tc/xacml/1.0/cs-xacml-schema-policy01.xsd"
PolicyId="identifier:example:SimplePolicy1"
RuleCombiningAlgId="identifier:rule-combining-algorithm:denyoverrides">
<Description>
Medi Corp access control policy
</Description>
<Target>
<Subjects>
<AnySubject/>
</Subjects>
<Resources>
<AnyResource/>
</Resources>
<Actions>
<AnyAction/>
</Actions>
</Target>
<Rule
RuleId="identifier:example:SimpleRule1"
Effect="Permit">
<Description>
Any subject with an e-mail name in the medico.com domain
can perform any action on any resource.
</Description>
<Target>
<Subjects>
<Subject>
<SubjectMatch MatchId="function:rfc822name-match">
<SubjectAttributeDesignator
AttributeId="identifier:subject:subject-id"
DataType="identifier:datatype:rfc822name"/>
<AttributeValue
DataType="identifier:datatype:rfc822name">
*@medico.com
</AttributeValue>
</SubjectMatch>
</Subject>
</Subjects>
<Resources>
<AnyResource/>
</Resources>
<Actions>
<AnyAction/>
</Actions>
</Target>
</Rule>
</xacml:Policy>
If Bart Simpson, with e-mail name "bs@simpsons.com", attempts to read his medical record at
Medi Corp, the corresponding request context looks as follows:
<?xml version="1.0" encoding="UTF-8"?>
<Request
xmlns="urn:oasis:names:tc:xacml:1.0:context"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="urn:oasis:names:tc:xacml:1.0:context
http://www.oasis-open.org/tc/xacml/1.0/sc-xacml-schema-context01.xsd">
<Subject>
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<Attribute
AttributeId="urn:oasis:names:tc:xacml:1.0:subject:subject-id"
DataType="identifier:rfc822name">
<AttributeValue>
bs@simpsons.com
</AttributeValue>
</Attribute>
</Subject>
<Resource>
<Attribute
AttributeId="identifier:resource:resource-uri"
DataType="xs:anyURI">
<AttributeValue>
http://medico.com/record/patient/BartSimpson
</AttributeValue>
</Attribute>
</Resource>
<Action>
<Attribute
AttributeId="identifier:example:action"
DataType="xs:string">
<AttributeValue>
read
</AttributeValue>
</Attribute>
</Action>
</Request>
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The PDP processing this request context locates the policy in its policy repository. It compares
the subject, resource and action in the request context with the subjects, resources and
actions in the policy target. Since the policy target matches the <AnySubject/>,
<AnyResource/> and <AnyAction/> elements, the policy mathces this context.
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The PDP now compares the subject, resource and action in the request context with the target
of the one rule in this policy. The requested resource matches the <AnyResource/> element
and the requested action matches the <AnyAction/> element, but the requesting subject-id
attribute does not match "*@medico.com".
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As a result, there is no rule in this policy that returns a "Permit" result for this request. The rulecombining algorithm for the policy specifies that, in this case, a result of "Deny" should be
returned. The response context looks as follows:
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<?xml version="1.0" encoding="UTF-8"?>
<Response
xmlns="urn:oasis:names:tc:xacml:1.0:context"
xsi:schemaLocation="urn:oasis:names:tc:xacml:1.0:context
http://www.oasis-open.org/tc/xacml/1.0/sc-xacml-schemacontext-01.xsd">
<Result>
<Decision>
Deny
</Decision>
</Result>
</Response>
3.2. Example two
This section contains an example XML document, an example request context and example
XACML rules. The XML document is a medical record. Four separate rules are defined. These
illustrate rule-combining and obligations.
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3.2.1 Example medical record instance
Following is an instance of a medical record to which the example XACML rules can be applied.
The <record> schema is defined in the registered namespace administered by "//medico.com".
<?xml version="1.0" encoding="UTF-8"?>
<record xmlns="medico.com/records.xsd"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="medico.com/records.xsd
http://www.medico.com/schema/record.xsd">
<patient>
<patientName>
<first>Bartholomew</first>
<last>Simpson</last>
</patientName>
<patientContact>
<street>27 Shelbyville Road</street>
<city>Springfield</city>
<state>MA</state>
<zip>12345</zip>
<phone>555.123.4567</phone>
<fax/>
<email/>
</patientContact>
<patientDoB xsi:type="date">1992-03-21</patientDoB>
<patientGender xsi:type="string">male</patientGender>
<policyNumber xsi:type="string">555555</policyNumber>
</patient>
<parentGuardian>
<parentGuardianName>
<first>Homer</first>
<last>Simpson</last>
</parentGuardianName>
<parentGuardianContact>
<street>27 Shelbyville Road</street>
<city>Springfield</city>
<state>MA</state>
<zip>12345</zip>
<phone>555.123.4567</phone>
<fax/>
<email>homers@aol.com</email>
</parentGuardianContact>
</parentGuardian>
<primaryCarePhysician>
<physicianName>
<first>Julius</first>
<last>Hibbert</last>
</physicianName>
<physicianContact>
<street>1 First St</street>
<city>Springfield</city>
<state>MA</state>
<zip>12345</zip>
<phone>555.123.9012</phone>
<fax>555.123.9013</fax>
<email/>
</physicianContact>
<registrationID>ABC123</registrationID>
</primaryCarePhysician>
<insurer>
<name>Blue Cross</name>
<street>1234 Main St</street>
<city>Springfield</city>
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<state>MA</state>
<zip>12345</zip>
<phone>555.123.5678</phone>
<fax>555.123.5679</fax>
<email/>
</insurer>
<medical>
<treatment>
<drug>
<name>methylphenidate hydrochloride</name>
<dailyDosage>30mgs</dailyDosage>
<startDate>1999-01-12</startDate>
</drug>
<comment>patient exhibits side-effects of skin coloration and
carpal degeneration</comment>
</treatment>
<result>
<test>blood pressure</test>
<value>120/80</value>
<date>2001-06-09</date>
<performedBy>Nurse Betty</performedBy>
</result>
</medical>
</record>
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3.2.2 Example request context
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The following example illustrates a request context to which the example rules are intended to be
applicable. It represents a request by the physician Julius Hibbert to read the patient date of birth in
the record of Bartholomew Simpson.
<?xml version="1.0" encoding="UTF-8"?>
<Request xmlns="urn:oasis:names:tc:xacml:0.16f:context"
xmlns:identifier="urn:oasis:names:tc:xacml:identifier"
xmlns:xacml="urn:oasis:names:tc:xacml:0.16f:policy"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="urn:oasis:names:tc:xacml:0.16f:context draftxacml-schema-context-16f.xsd">
<Subject>
<Attribute
AttributeId="urn:oasis:names:tc:xacml:1.0:subject:subject-category"
Issuer="www.medco.com"
IssueInstant="2001-12-17T09:30:47-05:00">
<AttributeValue>urn:oasis:names:tc:xacml:1.0:subjectcategory:acces
s-subject</AttributeValue>
</Attribute>
<Attribute
AttributeId="urn:oasis:names:tc:xacml:1.0:subject:subject-id"
Issuer="www.medco.com"
IssueInstant="2001-12-17T09:30:47-05:00">
<AttributeValue>Julius Hibbert</AttributeValue>
</Attribute>
<Attribute
AttributeId="urn:oasis:names:tc:xacml:1.0:subject:name-format"
Issuer="www.medco.com"
IssueInstant="2001-12-17T09:30:47-05:00">
<AttributeValue>urn:oasis:names:tc:xacml:1.0:datatype:x500name</At
tributeValue>
</Attribute>
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<Attribute
AttributeId="urn:oasis:names:tc:xacml:1.0:example:attribute:role"
Issuer="www.medco.com"
IssueInstant="2001-12-17T09:30:47-05:00">
<AttributeValue>physician</AttributeValue>
</Attribute>
<Attribute
AttributeId="urn:oasis:names:tc:xacml:1.0:example:attribute:physicia
n-id" Issuer="www.medco.com"
IssueInstant="2001-12-17T09:30:47-05:00">
<AttributeValue>jh1234</AttributeValue>
</Attribute>
</Subject>
<Resource>
<ResourceContent>
<md:record xmlns:md="http:www.medco.com/shemas/record.xsd">
<md:patient>
<md:patientDoB>1992-03-21</md:patientDoB>
</md:patient>
<!-- other fields -->
</md:record>
</ResourceContent>
<Attribute
AttributeId="urn:oasis:names:tc:xacml:1.0:resource:resource-uri">
<AttributeValue>
//medco.com/records/bart-simpson.xml#
xmlns(md=http:www.medico.com/schemas/record.xsd)xpointer(/md:recor
d/md:patient/md:patientDoB)
</AttributeValue>
</Attribute>
<Attribute
AttributeId="urn:oasis:names:tc:xacml:1.0:resource:xpath">
<AttributeValue>
xmlns(md=http:www.medico.com/schemas/record.xsd)xpointer(/md:recor
d/md:patient/md:patientDoB)
</AttributeValue>
</Attribute>
</Resource>
<Action>
<Attribute AttributeId="urn:oasis:names:tc:xacml:1.0:action">
<AttributeValue>read</AttributeValue>
</Attribute>
</Action>
</Request>
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3.2.3 Example plain-language rules
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The following plain-language rules are to be enforced:
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1. A person may read any record for which he or she is the designated patient.
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2. A person may read any record for which he or she is the designated parent or guardian, and for
which the patient is under 16 years of age.
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3. A physician may write any medical element for which he or she is the designated primary care
physician, provided an email is sent to the patient.
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4. An administrator shall not be permitted to read or write medical elements of a patient record.
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These rules may be written by different PAPs, operating independently, or by a single PAP.
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3.2.4 Example XACML rule instances
3.2.4.1
Rule 1
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Rule 1 illustrates a simple rule with a single <Condition> element. The following XACML
<Rule> instance expresses Rule 1.
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<?xml version="1.0" encoding="UTF-8"?>
<Rule xmlns="urn:oasis:names:tc:xacml:0.16f:policy"
xmlns:function="urn:oasis:names:tc:xacml:0.16f:function"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="urn:oasis:names:tc:xacml:0.16f:policy draftxacml-schema-policy-16f.xsd"
xmlns:ctx="urn:oasis:names:tc:xacml:0.16f:context"
xmlns:md="http:www.medco.com/schemas/record.xsd"
RuleId="urn:oasis:names:tc:xacml:examples:ruleid:1" Effect="Permit">
<Description>
A person may read any record defined by the
http://www.medco.com/scheams/record.xsd namespace
for which he or she is a designated patient
</Description>
<Target>
<Subjects>
<AnySubject/>
</Subjects>
<Resources>
<Resource>
<ResourceMatch MatchId="function:string-match">
<ResourceAttributeDesignator
AttributeId="urn:oasis:names:tc:xacml:resource:target-namespace"
DataType="xsi:string"/>
<AttributeValue
DataType="xsi:string">http://www.medco.com/schemas/record.xsd</Attri
buteValue>
</ResourceMatch>
<ResourceMatch MatchId="function:node-match">
<ResourceAttributeDesignator
AttributeId="urn:oasis:names:tc:xacml:resource:xpath"
DataType="xsi:string"/>
<AttributeValue
DataType="xsi:string">/md:record</AttributeValue>
</ResourceMatch>
</Resource>
</Resources>
<Actions>
<Action>
<ActionMatch MatchId="function:string-equal">
<ActionAttributeDesignator
AttributeId="urn:oasis:names:tc:xacml:action"
DataType="xsi:string"/>
<AttributeValue
DataType="xsi:string">read</AttributeValue>
</ActionMatch>
</Action>
</Actions>
</Target>
<Condition FunctionId="function:string-equal">
<SubjectAttributeDesignatorWhere
AttributeId="urn:oasis:names:tc:xacml:examples:attribute:policynumber" DataType="xsi:string"/>
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<AttributeSelector RequestContextPath=
"/ctx:Request/ctx:Resource/ctx:ResourceContent/md:record/md:patien
t/md:policyNumber"
DataType="xsi:string"/>
</Condition>
</Rule>
3.2.4.2
Rule 2
Rule 2 illustrates the use of a mathematical function, i.e. the <Apply> element with functionId
value of "function:date-subtract" to calculate age. It also illustrates the use of predicate
expressions, with the functionId value of "function:and".
<?xml version="1.0" encoding="UTF-8"?>
<Rule xmlns="urn:oasis:names:tc:xacml:0.16f:policy"
xmlns:function="urn:oasis:names:tc:xacml:0.16f:function"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="urn:oasis:names:tc:xacml:0.16f:policy
draft-xacml-schema-policy-16f.xsd"
xmlns:ctx="urn:oasis:names:tc:xacml:0.16f:context"
xmlns:md="http:www.medco.com/schemas/record.xsd"
RuleId="urn:oasis:names:tc:xacml:examples:ruleid:2" Effect="Permit">
<Description>
A person may read any medical record defined by the
http://www.medco.com/records.xsd namespace
for which he or she is the designated patient or guardian, and
for which the patient is under 16 years of age
</Description>
<Target>
<Subjects>
<AnySubject/>
</Subjects>
<Resources>
<Resource>
<ResourceMatch MatchId="function:string-match">
<ResourceAttributeDesignator
AttributeId="urn:oasis:names:tc:xacml:resource:target-namespace"
DataType="xsi:string"/>
<AttributeValue
DataType="xsi:string">http://www.medco.com/schemas/record.xsd</Attri
buteValue>
</ResourceMatch>
<ResourceMatch MatchId="function:node-match">
<ResourceAttributeDesignator
AttributeId="urn:oasis:names:tc:xacml:resource:xpath"
DataType="xsi:string"/>
<AttributeValue
DataType="xsi:string">/md:record</AttributeValue>
</ResourceMatch>
</Resource>
</Resources>
<Actions>
<Action>
<ActionMatch MatchId="function:string-equal">
<ActionAttributeDesignator
AttributeId="urn:oasis:names:tc:xacml:action"
DataType="xsi:string"/>
<AttributeValue
DataType="xsi:string">read</AttributeValue>
</ActionMatch>
</Action>
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</Actions>
</Target>
<Condition FunctionId="function:and">
<Apply FunctionId="function:string-equal">
<SubjectAttributeDesignatorWhere
AttributeId="urn:oasis:names:tc:xacml:examples:attribute:parentguardian-id"
DataType="xs:string"/>
<AttributeSelector RequestContextPath=
"/ctx:Request//ctx:ResourceContent/md:record/md:parentGuardian/md:
parentGuardianId"
DataType="xs:string"/>
</Apply>
<Apply FunctionId="function:dayTimeDuration-greater-than">
<Apply FunctionId="function:date-substract">
<EnvironmentAttributeDesignator
AttributeId="urn:oasis:names:tc:xacml:env:date"
DataType="xs:date"/>
<AttributeSelector RequestContextPath=
"/ctx:Request//ctx:ResourceContent/md:patient/md:patientDoB"
DataType="xs:date"/>
</Apply>
<AttributeValue DataType="xs:dateTimeDuration">16-00</AttributeValue>
</Apply>
</Condition>
</Rule>
3.2.4.3
Rule 3
Rule 3 illustrates the use of an obligation. The XACML <Rule> element syntax does not include
an element suitable for carrying an obligation, therefore Rule 3 has to be formatted as a
<Policy> element.
<?xml version="1.0" encoding="UTF-8"?>
<Policy xmlns="urn:oasis:names:tc:xacml:0.16f:policy"
xmlns:function="urn:oasis:names:tc:xacml:0.16f:function"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="urn:oasis:names:tc:xacml:0.16f:policy draftxacml-schema-policy-16f.xsd"
xmlns:ctx="urn:oasis:names:tc:xacml:0.16f:context"
xmlns:md="http:www.medco.com/schemas/record.xsd"
PolicyId="urn:oasis:names:tc:xacml:examples:policyid:3"
RuleCombiningAlgId="urn:oasis:names:tc:xacml:1.0:rule-combiningalgorithm:deny-overrides">
<Description>
Policy for any medical record defined by the
http://www.medco.com/schemas/record.xsd namespace
</Description>
<Target>
<Subjects>
<AnySubject/>
</Subjects>
<Resources>
<Resource>
<ResourceMatch MatchId="function:string-match">
<ResourceAttributeDesignator
AttributeId="urn:oasis:names:tc:xacml:resource:target-namespace"
DataType="xsi:string"/>
draft-xacml-specification-16a.doc
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<AttributeValue
DataType="xsi:string">http://www.medco.com/schemas/record.xsd</Attri
buteValue>
</ResourceMatch>
</Resource>
</Resources>
<Actions>
<AnyAction/>
</Actions>
</Target>
<Rule RuleId="urn:oasis:names:tc:xacml:examples:ruleid:3"
Effect="Permit">
<Description>
A physician may write any medical element is a record for
which he or she is the designated primary
care physician, provided an email is sent to the patient
</Description>
<Target>
<Subjects>
<Subject>
<SubjectMatch MatchId="function:string-match">
<SubjectAttributeDesignator
AttributeId="urn:oasis:names:tc:xacml:1.0:examples:attribute:group"
DataType="xsi:string"/>
<AttributeValue
DataType="xs:string">physician</AttributeValue>
</SubjectMatch>
</Subject>
</Subjects>
<Resources>
<Resource>
<ResourceMatch MatchId="function:node-match">
<ResourceAttributeDesignator
AttributeId="urn:oasis:names:tc:xacml:resource:xpath"
DataType="xsi:string"/>
<AttributeValue
DataType="xsi:string">/md:record/md:medical</AttributeValue>
</ResourceMatch>
</Resource>
</Resources>
<Actions>
<Action>
<ActionMatch MatchId="function:string-equal">
<ActionAttributeDesignator
AttributeId="urn:oasis:names:tc:xacml:action"
DataType="xsi:string"/>
<AttributeValue
DataType="xsi:string">write</AttributeValue>
</ActionMatch>
</Action>
</Actions>
</Target>
<Condition FunctionId="function:string-equal">
<SubjectAttributeDesignatorWhere
AttributeId="urn:oasis:names:tc:xacml:examples:attribute:physician
-id" DataType="xsi:string"/>
<AttributeSelector RequestContextPath=
"/ctx:Request/ctx:Resource/ctx:ResourceContent/md:record/md:primar
yCarePhysician/md:physicianId"
DataType="xsi:string"/>
</Condition>
draft-xacml-specification-16a.doc
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1016
1017
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1020
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1064
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1067
1068
1069
</Rule>
<Obligations>
<Obligation
ObligationId="urn:oasis:names:tc:xacml:examples:obligation:email"
FulfilOn="Permit">
<AttributeAssignment
AttributeId="urn:oasis:names:tc:xacml:examples:attribute:mailto"
DataType="xs:string">
<AttributeSelector RequestContextPath=
"/ctx:Request//ctx:ResourceContent/md:/record/md:patient/md:patien
tContact/md:email"
DataType="xs:string"/>
</AttributeAssignment>
<AttributeAssignment
AttributeId="urn:oasis:names:tc:xacml:examples:attribute:text"
DataType="xs:string">
<AttributeValue DataType="xs:string">Your medical record
has been accessed by:</AttributeValue>
</AttributeAssignment>
<AttributeAssignment
AttributeId="urn:oasis:names:tc:xacml:examples:attribute:text"
DataType="xs:string">
<SubjectAttributeDesignator
AttributeId="urn:osasis:names:tc:xacml:subject:subject-id"
DataType="xs:string"/>
</AttributeAssignment>
</Obligation>
</Obligations>
</Policy>
3.2.4.4
Rule 4
Rule 4 illustrates the use of the "Deny" effect value, and a <Rule> with no <Condition>
element.
<?xml version="1.0" encoding="UTF-8"?>
<Rule xmlns="urn:oasis:names:tc:xacml:0.16f:policy"
xmlns:function="urn:oasis:names:tc:xacml:0.16f:function"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="urn:oasis:names:tc:xacml:0.16f:policy
draft-xacml-schema-policy-16f.xsd"
xmlns:ctx="urn:oasis:names:tc:xacml:0.16f:context"
xmlns:md="http:www.medco.com/schemas/record.xsd"
RuleId="urn:oasis:names:tc:xacml:example:ruleid:4" Effect="Deny">
<Description>
An Administrator shall not be permitted to read or write medical
elements of a patient record defined by
the http://www.medico.com/records.xsd namespace.
</Description>
<Target>
<Subjects>
<Subject>
<SubjectMatch MatchId="function:string-equal">
<SubjectAttributeDesignator
AttributeId="urn:oasis:names:tc:xacml:1.0:example:attribute:role"
DataType="xs:string"/>
<AttributeValue
DataType="xs:string">administrator</AttributeValue>
</SubjectMatch>
</Subject>
</Subjects>
draft-xacml-specification-16a.doc
24
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1071
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1101
1102
1103
1104
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1109
1110
<Resources>
<Resource>
<ResourceMatch MatchId="function:string-match">
<ResourceAttributeDesignator
AttributeId="urn:oasis:names:tc:xacml:resource:target-namespace"
DataType="xsi:string"/>
<AttributeValue
DataType="xsi:string">http://www.medco.com/schemas/record.xsd</Attri
buteValue>
</ResourceMatch>
<ResourceMatch MatchId="function:node-match">
<ResourceAttributeDesignator
AttributeId="urn:oasis:names:tc:xacml:resource:xpath"
DataType="xsi:string"/>
<AttributeValue
DataType="xsi:string">/md:record/md:medical</AttributeValue>
</ResourceMatch>
</Resource>
</Resources>
<Actions>
<Action>
<ActionMatch MatchId="function:string-equal">
<ActionAttributeDesignator
AttributeId="urn:oasis:names:tc:xacml:action"
DataType="xsi:string"/>
<AttributeValue
DataType="xsi:string">read</AttributeValue>
</ActionMatch>
</Action>
<Action>
<ActionMatch MatchId="function:string-equal">
<ActionAttributeDesignator
AttributeId="urn:oasis:names:tc:xacml:action"
DataType="xsi:string"/>
<AttributeValue
DataType="xsi:string">write</AttributeValue>
</ActionMatch>
</Action>
</Actions>
</Target>
</Rule>
1111
4. Models (non-normative)
1112
The domain model and language model of XACML are described in the following sub-sections.
1113
1114
4.1. Data-flow model
The major actors in the XACML domain are shown in the data-flow diagram of Figure 1.
draft-xacml-specification-16a.doc
25
access
requester
PEP
2. access request
11. obligations
obligations
service
7. resource
resource
3. request
10. response
PDP
8. request
context
9. response
context
context
handler
4. attribute
6. attribute
query
PIP
1. policy
5c. resource
attributes
5b. envrionment
attributes
5a. subject
attributes
PAP
subjects
environment
1115
1116
Figure 1 - Data-flow diagram
1117
1118
1119
1120
1121
Note: some of the data-flows shown in the diagram may be facilitated by a repository. For instance,
the communications between the context handler and the PIP or the communications between the
PDP and the PAP may be facilitated by a repository. The XACML specification is not intended to
place restrictions on the location of any such repository, or indeed to prescribe a particular
communication protocol for any of the data-flows.
1122
The model operates by the following steps.
1123
1124
1. PAPs write policies and make them available to the PDP. Its policies represent the complete
policy for a particular target.
1125
2. The access requester sends a request for access to the PEP.
1126
1127
3. The PEP sends the request for access to the context handler in its native request format. The
context handler constructs a request context in accordance with steps 4,5,6 and 7.
1128
4. Subject, resource and environment attributes are requested from a PIP.
1129
5. The PIP obtains the requested attributes.
1130
6. The PIP returns the requested attributes to the context handler.
1131
7. Optionally, the context handler includes the resource in the context.
draft-xacml-specification-16a.doc
26
1132
1133
8. The context handler sends the request context to the PDP. The PDP identifies the policy
applicable to the request context. The PDP evaluates the policy.
1134
9. The PDP returns the response context to the context handler.
1135
1136
10. The context handler translates the response context to the native response format of the PEP.
The context handler returns the response to the PEP.
1137
11. The PEP fulfills the obligations.
1138
12. If access is permitted, then PEP permits access to the resource.
4.2. XACML context
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
XACML is designed to be applicable to a variety of application environments. The core language is
insulated from the application environment by the XACML context, as shown in Figure 2, in which
the scope of the XACML specification is indicated by the shaded area. The XACML context is
defined in XML schema, describing a canonical representation for the inputs and outputs of the
PDP. Attributes referenced by an instance of XACML may be in the form of XPath expressions on
the context. Implementations must convert between the attribute representations in the
application environment (e.g., SAML, J2SE, CORBA, and so on) and the attribute representations
in the XACML context. How this is achieved is outside the scope of the XACML specification. In
some cases, such as SAML, this conversion may be accomplished in an automated way through
the use of an XSLT transformation.
xacml.xml
domain-specific
inputs
xacmlContext/
request.xml
PDP
xacmlContext/
response.xml
domain-specific
outputs
1150
1151
Figure 2 - XACML context
4.3. Policy language model
1152
1153
The policy language model is shown in Figure 3. The main components of the model are:
1154

Rule;
1155

Policy; and
1156

Policy set.
1157
These are described in the following sub-sections.
draft-xacml-specification-16a.doc
27
1
PolicySet
1
1
0..*
1
1
Policy
Combining
Alogorithm
1
1
0..*
0..*
0..1
1
Target
Policy
Obligations
0..1
1
1
1..*
1
1
1
1..*
1..*
Subject
0..1
Resource
1
Rule
Combining
Algorithm
Action
1
0..*
1
Rule
Condition
1
0..1
1
1
Effect
1158
Figure 3 - Policy language model
1159
4.3.1 Rule
1160
1161
The main components of a rule are:
1162

a target;
1163

an effect; and
1164

a condition.
draft-xacml-specification-16a.doc
28
1165
These are discussed in the following sub-sections.
4.3.1.1
1166
Rule target
1167
The target defines the set of:
1168

resources;
1169

subjects; and
1170

actions
1171
1172
1173
1174
1175
to which the rule is intended to apply. If the rule is intended to apply to all entities of a particular
type, then an empty element named <AnySubject/>, <AnyResource/> or <AnyAction/> is
used. An XACML PDP verifies that the resources, subjects and actions identified in the request
context are all present in the target of the rules that it uses to evaluate the decision request.
Target definitions are discrete, in order that they may be indexed by the PDP.
1176
1177
The <Target> element may be absent from a <Rule>. In this case, the <Rule> inherits its target
from the parent <Policy> element.
1178
1179
1180
1181
1182
1183
1184
1185
1186
4.3.1.2
Effect
The effect of the rule indicates the rule-writer's intended consequence of a "True" evaluation for
the rule. Two values are allowed: "Permit" and "Deny".
4.3.1.3
Condition
Condition is a general expression of predicates of attributes. It should not duplicate the exact
predicates implied by the target. Therefore, it may be absent.
4.3.1.4
Rule evaluation
A rule has a value that can be calculated by evaluating its contents. Rule evaluation involves
separate evaluation of the rule's target and condition. The rule truth table is shown in Table 1.
Target
Condition
Rule
Match
True
Effect
Match
False
Not applicable
Match
Indeterminate
Indeterminate
No-match
True
Not applicable
No-match
False
Not applicable
No-match
Indeterminate
Not applicable
1187
Table 1 - Rule truth table
1188
1189
The target value is "Match" if the resource, subject and action specified in the request context
are all present in the target defined in the rule. Otherwise, its value is "No-match".
1190
1191
The condition value is "True" if the <Condition> element is absent, or if it evaluates to "True" for
the attribute values supplied in the request context. Its value is "False" if the <Condition>
draft-xacml-specification-16a.doc
29
1192
1193
1194
element evaluates to "False" for the attribute values supplied in the request context. If any
attribute value referenced in the condition cannot be obtained, then the condition evaluates to
"Indeterminate".
4.3.2 Policy
1195
1196
1197
From the data-flow model one can see that rules are not exchanged amongst system entities.
Therefore, a PAP combines rules in a policy. A policy comprises four main components:
1198

a target;
1199

a rule-combining algorithm-identifier;
1200

a set of rules; and
1201

obligations.
1202
1203
Rules are described above. The remaining components are described in the following subsections.
4.3.2.1
1204
Policy target
1205
1206
1207
The target of a policy must include all the decision requests that the policy is intended to
evaluate. The target may be declared by the writer of the policy, or computed from the targets of
its component rules.
1208
1209
If the target of the policy is computed from the targets of the component rules, two approaches
are permitted:
1210
1211

the target of the policy may be the union of the target definitions for resource, subject and
action that are contained in the component rules; or
1212
1213

the target of the policy may be the intersection of the target definitions for resource, subject
and action that are contained in the component rules.
1214
1215
1216
1217
In the case where the policy target is computed as the union of the targets of the individual rules,
the target may be omitted from the individual rules, and the targets from the component rules
must be included in the form of conditions in their respective rules. As an example, the following
rule target and condition may be merged in a single condition.
1218
Target
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
<Target>
<Subjects MatchId="function:rfc822Name-equal"
DataType="xs:boolean">
<AttributeDesignator
Designator="//xacmlContext/Request/Subject/Attribute[@DataType='iden
tifier:rfc822Name']" DataType="identifier:rfc822Name"/>
<Attribute DataType="identifier:rfc822Name">@</Attribute>
</Subjects>
<Resources MatchId="function:string-match" DataType="xs:boolean">
<AttributeDesignator
Designator="//xacmlContext/Request/Resource/@ResourceURI"
DataType="xs:anyURI"/>
<Attribute
DataType="xs:anyURI">//medico.com/record.*</Attribute>
</Resources>
<Actions MatchId="function:subset" DataType="xs:boolean">
draft-xacml-specification-16a.doc
30
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
<AttributeDesignator
Designator="//xacmlContext/Action[@Namespace=]"
DataType="xs:string"/>
<Attribute DataType="xs:string">read</Attribute>
</Actions>
</Target>
Condition
<Condition FunctionId="function:string-equal" DataType="xs:boolean">
<AttributeDesignator
Designator="//xacmlContext/Request/Subject/Attribute[@DataType='iden
tifier:patientName']" DataType="xs:string"/>
<AttributeDesignator
Designator="//xacmlContext/Request/Resource/patientName"
DataType="xs:string"/>
</Condition>
merged Condition.
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
<Condition FunctionId="function:and" DataType="xs:boolean">
<Function FunctionId="function:string-match"
DataType="xs:boolean">
<AttributeDesignator
Designator="//xacmlContext/Request/Resource/@ResourceURI"
DataType="xs:anyURI"/>
<Attribute
DataType="xs:anyURI">//medico.com/record.*</Attribute>
</Function>
<Function FunctionId="function:subset" DataType="xs:boolean">
<AttributeDesignator
Designator="//xacmlContext/Action[@Namespace=]"
DataType="xs:string"/>
<Attribute DataType="xs:string">read</Attribute>
</Function>
<Function FunctionId="function:string-equal"
DataType="xs:boolean">
<AttributeDesignator
Designator="//xacmlContext/Request/Subject/Attribute[@DataType='iden
tifier:patientName']" DataType="xs:string"/>
<AttributeDesignator
Designator="//xacmlContext/Request/Resource/patientName"
DataType="xs:string"/>
</Function>
</Condition>
1276
1277
In the case where the policy target is computed as the intersection of the targets of the individual
rules, the targets may be omitted from the individual rules.
1278
1279
In the case that a rule target is present, the rule is evaluated according to the truth table of Table
1.
1280
4.3.2.2
Rule-combining algorithm
1281
1282
The rule-combining algorithm specifies the procedure by which the results of evaluating the
component rules are combined, when evaluating the policy.
1283
1284
1285
The result of evaluating the policy is defined by the rule-combining algorithm. In the case that
the PDP uses a policy to determine its response to a decision request, the Decision value is
the value of the policy, as defined by the rule-combining algorithm.
1286
See Appendix C for an example of a rule-combining algorithm.
draft-xacml-specification-16a.doc
31
4.3.2.3
1287
Obligations
1288
1289
The XACML <Rule> syntax does not contain an element suitable for carrying obligations,
therefore, if required in a policy, obligations must be added by the writer of the policy.
1290
1291
1292
When a PDP evaluates a policy containing obligations, it returns certain of those obligations to
the PEP in its response context. The obligations that it returns to the PEP are those whose
xacml:FulfilOn attributes have the same value as the result of evaluating the policy.
4.3.2.4
1293
Example policy
1294
1295
1296
This section uses the example of Section 3 to illustrate the process of combining rules. The policy
governing read access to medical elements of a record is formed from each of the four rules
described in Section 3.2.4. In plain language, the combined rule is:
1297

Either the requestor is the patient; or
1298

the requestor is the parent or guardian and the patient is under 16; or
1299

the requestor is the primary care physician and a notification is sent to the patient; and
1300

the requestor is not an administrator.
1301
1302
The following XACML <Policy> illustrates the combined rules. Rules 1 and 4 are included by
reference, rule 2 is included as a digest and rule 3 is explicitly included.
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
<?xml version="1.0" encoding="UTF-8"?>
<saml:Assertion MajorVersion="0" MinorVersion="28"
AssertionID="A7F34K90" Issuer="medico.com" IssueInstant="2002-0322T08:23:47-05:00">
<PolicyStatement PolicyId="//medico.com/rules/policy5"
RuleCombiningAlgId="urn:oasis:names:tc:XACML:identifier:ruleCombinin
gAlgorithms:denyOverrides"
xmlns="urn:oasis:names:tc:xacml:0.15i:policy"
xmlns:function="urn:oasis:names:tc:xacml:0.15i:function"
xmlns:saml="urn:oasis:names:tc:SAML:1.0:assertion"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="urn:oasis:names:tc:xacml:0.15i:policy
D:\MYDOCU~1\Standards\XACML\v15\draft-xacml-schema-policy-15i.xsd">
<Target>
<Subjects MatchId="function:superset" DataType="xs:boolean">
<AttributeDesignator
Designator="//xacmlContext/Request/Subject/Attribute[@DataType='iden
tifier:role']" DataType="xs:string"/>
<Attribute DataType="xs:string"></Attribute>
</Subjects>
<Resources MatchId="function:anyURI-equal"
DataType="xs:boolean">
<AttributeDesignator
Designator="//xacmlContext/Request/Resource/@ResourceURI"
DataType="xs:anyURI"/>
<Attribute
DataType="xs:anyURI">//medico.com/record/medical.*</Attribute>
</Resources>
<Actions MatchId="function:subset" DataType="xs:boolean">
<AttributeDesignator
Designator="//xacmlContext/Action[@Namespace=]"
DataType="xs:string"/>
<Attribute DataType="xs:string">read</Attribute>
</Actions>
</Target>
draft-xacml-specification-16a.doc
32
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
<RuleSet>
<RuleDesignator>
<RuleId>//medico.com/rules/rule1</RuleId>
</RuleDesignator>
<RuleDesignator>
<RuleDigest
Base64Digest="H7jiE0+jwkn63k/JhB3+D9aI4V3J9z/o0"/>
</RuleDesignator>
<Rule RuleId="//medico.com/rules/rule3" Effect="Permit">
<Description>A physician may write any medical element for
which he or she is the designated primary care
physician</Description>
<Condition FunctionId="function:and"
DataType="xs:boolean">
<Function FunctionId="function:string-equal"
DataType="xs:boolean">
<AttributeDesignator
Designator="//xacmlContext/Request/Subject/SubjectId"
DataType="xs:string"/>
<AttributeDesignator
Designator="//xacmlContext/Request/Resource/physicianName"
DataType="xs:string"/>
</Function>
<Function FunctionId="function:present"
DataType="xs:boolean">
<AttributeDesignator
Designator="//xacmlContext/Request/Resource/patient/email"
DataType="xs:string"/>
</Function>
</Condition>
</Rule>
<RuleDesignator>
<RuleId>//medico.com/rules/rule4</RuleId>
</RuleDesignator>
</RuleSet>
<Obligations>
<Obligation ObligationId="//medico.com/emailer"
FulfilOn="Permit">
<AttributeDesignator
Designator="//xacmlContext/Request/Resource/patient/email"
DataType="xs:string"/>
<AttributeAssignment DataType="xs:string"
AttributeId="//medico.com/text">Your medical record has been
accessed by:</AttributeAssignment>
<AttributeDesignator
Designator="//xacmlContext/Request/Subject/SubjectId"
DataType="xs:string"/>
</Obligation>
</Obligations>
</PolicyStatement>
</saml:Assertion>
1389
4.3.3 Policy set
1390
A policy set comprises four main components:
1391

a target;
1392

a policy-combining algorithm-identifier
1393

a set of policies; and
draft-xacml-specification-16a.doc
33
1394

obligations.
1395

.
1396
1397
The target and policy statement components are described above. The other components are
described in the following sub-sections.
1398
1399
1400
1401
4.3.3.1
Obligations
The writer of a policy set may add obligations to the policy set, in addition to those contained in
the component policies and policy sets.
4.3.3.2
Policy-combining algorithm
1402
1403
1404
1405
The policy-combining algorithm is the procedure by which the results of evaluating the
component policies are combined to form the value of the policy set. In the case that the PDP
uses a policy set to determine its response to a decision request, the Decision value is the
result of evaluating the policy set.
1406
1407
1408
1409
When a PDP evaluates a policy set containing obligations, it returns certain of those obligations
to the PEP in its response context. The XACML <Obligation> elements that are returned to the
PEP are those whose xacml:FulfilOn attributes have the same value as the result of evaluating
the policy set.
1410
1411
1412
As a consequence of this procedure, no obligations are returned to the PEP if the policies from
which they are drawn are not evaluated, or their evaluated result is "Indeterminate" or "Not
applicable".
1413
See Appendix C for an example of a policy-combining algorithm.
1414
5. Functional requirements (normative)
1415
1416
This section specifies certain functional requirements that are not directly associated with the
production or consumption of a particular XACML element-.
1417
5.1. Policy Decision Point
1418
1419
1420
Given a valid XACML policy or policy set, a compliant XACML PDP MUST evaluate the policy as
specified in Sections 5 and 6. The PDP MUST return a response context, with one <Decision>
element values "Permit", "Deny", "Indeterminate" or "NotApplicable".
1421
1422
If the "Permit" value is returned, then the PEP MAY permit access to the resource. If the "Deny"
value is returned, then the PEP SHALL deny access to the resource.
1423
1424
1425
1426
1427
1428
1429
If the "Permit" value is returned with one or more obligations, then the PEP MAY permit access
provided that all the obligations are successfully fulfilled. If the "Deny" value is returned with one
or more obligations, then the PEP SHALL deny access, but it MUST still fulfill the obligations. In
the case that an obligation cannot be fulfilled, the PEP SHOULD raise an error. How the error is
raised is outside the scope of XACML. In any case, the PDP MAY return additional information in
the <statusCode> element of the response context. In the case of a "Permit" decision, the PDP
MAY specify which rules were used in arriving at the decision.
1430
1431
If an "Indeterminate" decision value is returned, it means that the PDP could not make a decision.
The PDP MAY return a decision value of "Indeterminate" with a status code of:
draft-xacml-specification-16a.doc
34
1432
"urn:oasis:names:tc:xacml:1.0:missing-attribute",
1433
1434
1435
1436
signifying that more information is needed. In this case, the <Status> element MAY list the names
of any attributes of the subject and the resource that are needed by the PDP to refine its
decision. A PEP MAY resubmit a refined request context in response to a decision of
"Indeterminate" with a status code of
1437
"urn:oasis:names:tc:xacml:1.0:missing-attribute",
1438
1439
by adding attribute values for the attribute names that were listed in the response. When the PDP
returns a decision of "Indeterminate", with a status code of
1440
"urn:oasis:names:tc:xacml:1.0:missing-attribute",
1441
1442
1443
1444
it MUST NOT list the names of any attribute of the subject or the resource of the request for
which values were supplied in the request. Note, this requirement forces the PDP to eventually
return a decision of "Permit", "Deny" or "Indeterminate" with some other reason, in response to
successively-refined requests.
1445
1446
If a decision value of "NotApplicable" is returned, it means that the PDP's policy is not applicable to
the request, implying that the PEP should send its request to another PDP.
1447
1448
1449
1450
XACML says nothing about how top-level XACML policies should be configured. For example, a
top-level policy might be a <Policy> element containing a <Target> element that matches
every request, or it might be a <Policy> element containing a <Target> element that matches
only a specific subject.
1451
1452
1453
1454
1455
1456
1457
5.2. Hierarchical resources
It is often the case that a resource is organized as a hierarchy (e.g. file system, XML document).
Some applications may require access to an entire subtree of the resource specified by a node.
XACML allows the PEP (or Context Handler) to specify whether the access is just for a single
resource or for a subtree below the specified resource. The latter is equivalent to repeating a
single request for each node in the entire subtree. When a request context contains a resource
attribute of type
1458
"urn:oasis:names:tc:xacml:1.0:resource:scope"
1459
1460
with a value of "Immediate", or if it does not contain that attribute, then access is requested to just
the single resource specified by the ResourceId attribute.
1461
When the
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
"urn:oasis:names:tc:xacml:1.0:resource:scope"
attribute has the value "Children", access is requested for both the specified resource and its
children resources. When the
"urn:oasis:names:tc:xacml:1.0:resource:scope"
attribute has the value "Descendant", access is requested for both the specified resource and all
its descendant resources. In the case of "Children" and "Descendant", the authorization
decision MAY include multiple results for the multiple resources. An XACML response can
contain multiple <Result> elements. In this case, the <Status> element SHOULD be included
only in the first <Result> element (the remaining <Result> elements SHOULD NOT include the
<Status> element). Note that the method by which the PDP discovers whether the resource is
hierarchically organized or not is outside the scope of XACML.
1473
draft-xacml-specification-16a.doc
35
1475
Policy syntax (normative, with the exception of
the schema fragments)
1476
6.1. Element <PolicySet>
1474
6.
1477
1478
1479
1480
1481
The <PolicySet> element is a top-level element in the XACML policy schema. <PolicySet> is
an aggregation of other policy sets and policies. Policy sets MAY be included in an enclosing
<PolicySet> element either directly by the <PolicySet> element or indirectly by the
<PolicySetIdReference> element. Policies MAY be included in an enclosing <PolicySet>
either directly by the <Policy> element or indirectly by the <PolicyIdReference> element.
1482
1483
1484
If a<PolicySet> element contains references to other policy sets or policies in the form of
URIs, then these references MAY be resolvable. Applications MAY use SAML protocol extensions
to query for the <PolicySetAssertion> or <PolicyAssertion> by reference.
1485
1486
Policies included in the <PolicySet> element MUST be combined by the algorithm specified by
the PolicyCombiningAlgId attribute.
1487
1488
1489
1490
The <Target> element defines the applicability of the <PolicySet> to decision requests. If
there is a match between the <Target> element within <PolicySet> and the authorization
request, then the <PolicySet> element MAY be used by the PDP in making the authorization
decision.
1491
1492
1493
The <Obligations> element is a set of obligations that MUST be fulfilled by the PEP in
conjunction with the authorization decision. If the PEP does not understand any obligation, then
it MUST act as if the PDP returned a “Deny” authorization decision value.
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
<xs:element name="PolicySet" type="xacml:PolicySetType"/>
<xs:complexType name="PolicySetType">
<xs:sequence>
<xs:element ref="xacml:Description" minOccurs="0"/>
<xs:element ref="xacml:PolicySetDefaults" minOccurs="0"/>
<xs:element ref="xacml:Target"/>
<xs:choice minOccurs="0" maxOccurs="unbounded">
<xs:element ref="xacml:PolicySet"/>
<xs:element ref="xacml:Policy"/>
<xs:element ref="xacml:PolicySetIdReference"/>
<xs:element ref="xacml:PolicyIdReferece"/>
</xs:choice>
<xs:element ref="xacml:Obligations" minOccurs="0"/>
</xs:sequence>
<xs:attribute name="PolicySetId" type="xs:anyURI"
use="required"/>
<xs:attribute name="PolicyCombiningAlgId" type="xs:anyURI"
use="required"/>
</xs:complexType>
1513
The <PolicySet> element is of PolicySetType complex type.
1514
The <PolicySet> element contains the following attributes and elements:
1515
PolicySetId [Required]
1516
1517
1518
1519
Policy set identifier. The party assigning the identifier MUST minimize the potential of
some other party reusing the same identifier. This MAY be achieved by following a
predefined URN or URI scheme. If the policy set identifier is in the form of a URI it MAY be
resolvable.
draft-xacml-specification-16a.doc
36
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
PolicyCombiningAlgId [Required]
The identifier of the policy-combining algorithm by which the <PolicySet>
components MUST be combined. Standard policy-combining algorithms are listed in
Appendix C. Standard policy-combining algorithm identifiers are listed in Section B.10.
<Description> [Optional]
A free-form description of the <PolicySet>.
<PolicySetDefaults> [Optional]
A set of default values applicable to the <PolicySet>. This set of policy defaults does not
propagate down into <PolicySet> components.
<Target> [Required]
1530
The <Target> element defines the applicability of a <PolicySet> to decision requests.
1531
1532
1533
The <Target> element MAY be declared by the creator of the <PolicySet> or it MAY be
computed from the <Target> elements of the referenced <Policy> elements, either as
an intersection or as a union.
1534
1535
1536
1537
1538
If the <xacml-context:Subject>, <xacml-context:Resource>, and <xacmlcontext:Action> elements of the <xacml-context:Request> element match the
<Subjects>, <Resources>, and <Actions> elements of the <Target> within the
<PolicySet> element, then it MAY be used by the PDP in making an authorization
decision.
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
<PolicySet> [Any Number]
A policy set component that is included in this policy set.
<Policy> [Any Number]
The policy component that is included in this policy set.
<PolicySetIdReference> [Any Number]
A reference to the <PolicySet> component that MUST be included in this policy set. If
<PolicySetIdReference> is an URI, then it MAY be resolvable. Applications MAY use
SAML protocol extensions to query <PolicySet> by reference.
<PolicyIdReference> [Any Number]
A reference to the <Policy> component that MUST be included in this policy set. If the
<PolicyIdReference> is an URI, then it MAY be resolvable. Applications MAY use
SAML protocol extensions to query <Policy> by reference.
<Obligations> [Optional]
Contains the set of <Obligation> elements that MUST be discharged by the PEP. If the
PEP does not understand any obligation in this set, then it MUST act as if the decision
request was denied by the PDP.
6.2. Element <Description>
The <Description> element is used for a free-form description of the <PolicySet> element
and <Policy> element. The <Description> element is of xs:string simple type.
draft-xacml-specification-16a.doc
37
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
<xs:element name="Description" type="xs:string"/>
6.3. Element <PolicySetDefaults>
The <PolicySetDefaults> element is used to specify default values for the <PolicySet>
element.
<xs:element name="PolicySetDefaults" type="xacml:DefaultsType"/>
<xs:complexType name="DefaultsType">
<xs:sequence minOccurs="0" maxOccurs="unbounded">
<xs:element ref="xacml:AbstractDefaults"/>
</xs:sequence>
</xs:complexType>
1568
<PolicySetDefaults> element is of DefaultsType complex type.
1569
<AbstractDefaults> [Any Number]
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
This is the head of a substitution group to specify default parameters. The only element in
this substitution group defined at this time is the <XpathVersion> element.
6.4. Element <Target>
The <Target> element identifies the set of decision requests that the parent element is intended
to evaluate. The <Target> element appears as a child of <PolicySet>, <Policy>, and
<Rule> elements. It contains definitions for subjects, resources and actions.
<xs:element name="Target" type="xacml:TargetType"/>
<xs:complexType name="TargetType">
<xs:sequence>
<xs:element ref="xacml:Subjects"/>
<xs:element ref="xacml:Resources"/>
<xs:element ref="xacml:Actions"/>
</xs:sequence>
</xs:complexType>
1584
1585
1586
If the subject, resource and action in the <xacml-context:Request> element match the
definitions of subjects, resources and actions in the <Target> element, then the policy
component containing the <Target> element MAY be applicable to the decision request.
1587
1588
1589
1590
1591
For the purposes of matching, the <Subjects>, <Resources>, and <Actions> children of the
<Target> element are combined using the logical ‘AND’ operation. For the parent of the
<Target> element to be applicable to the decision request, at least one <Subject>, one
<Resource>, and one <Action> MUST match the corresponding elements in the <xacmlcontext:Request> element.
1592
The <Target> element is of TargetType complex type.
1593
Note: a disjunctive sequence is a sequence of elements combined using the logical ‘OR’ operation.
1594
<Subjects> [Required]
1595
1596
1597
1598
This element is either a disjunctive sequence of <Subject> elements that match this
target with subject attributes in the request context, or a special element
<AnySubject> that matches any subject attribute in the request context.
<Resources> [Required]
draft-xacml-specification-16a.doc
38
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
This element is either a disjunctive sequence of <Resource> elements that match this
target with resource attributes in the request context, or a special element
<AnyResource> that matches any resource attribute in the request context.
<Actions> [Required]
This element is either a disjunctive sequence of <Action> elements that match this target
with action attributes in the request context, or a special element <AnyAction> that
matches any action attribute in the request context.
6.5. Element <Subjects>
The <Subjects> element is a child of the <Target> element and is a wrapper for the disjunctive
sequence of <Subject> elements. The <Subjects> element is combined using the logical ‘AND’
operation with other children of the <Target> element.
<xs:element name="Subjects" type="xacml:SubjectsType"/>
<xs:complexType name="SubjectsType">
<xs:choice>
<xs:element ref="xacml:Subject" maxOccurs="unbounded"/>
<xs:element ref="xacml:AnySubject"/>
</xs:choice>
</xs:complexType>
1617
The <Subjects> element is of SubjectsType complex type.
1618
<Subject> [Required]
1619
1620
1621
1622
1623
A disjunctive sequence of one or more matching specifications against subject attributes
in the request context.
<AnySubject> [Required]
An element matching any subject attribute in the request context.
6.6. Element <Subject>
1624
1625
Note: a conjunctive sequence is a sequence of elements combined using the logical ‘AND’
operation.
1626
1627
The <Subject> element is a conjunctive sequence of individual matches against subject
attributes in the request context.
1628
1629
1630
1631
1632
1633
<xs:element name="Subject" type="xacml:SubjectType"/>
<xs:complexType name="SubjectType">
<xs:sequence>
<xs:element ref="xacml:SubjectMatch" maxOccurs="unbounded"/>
</xs:sequence>
</xs:complexType>
1634
The <Subject> element is of SubjectType complex type.
1635
<Subject> element contains following elements:
1636
<SubjectMatch> [One to Many]
1637
1638
A conjunctive sequence of individual matches with the subject attributes in the request
context.
draft-xacml-specification-16a.doc
39
1639
6.7. Element <SubjectMatch>
1640
1641
The <SubjectMatch> element identifies a set of subject-related entities by matching values in
the <Subject> element of the context with values embedded in the <Policy> element.
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
<xs:element name="SubjectMatch" type="xacml:SubjectMatchType"/>
<xs:complexType name="SubjectMatchType">
<xs:sequence>
<xs:choice>
<xs:element ref="xacml:SubjectAttributeDesignator"/>
<xs:element ref="xacml:AttributeSelector"/>
</xs:choice>
<xs:element ref="xacml:AttributeValue"/>
</xs:sequence>
<xs:attribute name="MatchId" type="xs:QName" use="required"/>
</xs:complexType>
1653
The <SubjectMatch> element is of SubjectMatchType complex type.
1654
The <SubjectMatch> element contains following attributes and elements:
1655
MatchId [required]
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
Specifies a matching function. The value of this attribute MUST be of type Qname, with
legal values documented inAppendix A.
<SubjectAttributeDesignator> [required]
Identifies one or more values in the <Subject> element of the <xacmlcontext:Request> element.
<AttributeSelector> [required]
MAY be used to identify one or more values in the <Subject> element of <xacmlcontext:Request> element. It MUST contain a legal xpath expression over the
<Subject> element of the <xacml-context:Request> element.
6.8. Element <Resources>
The <Resources> element is a child of the <Target> element and is a wrapper for the disjunctive
sequence of <Resource> elements. The <Resources> element is combined using the logical
‘AND’ operation with other children of the <xacml:Target> element.
<xs:element name="Resources" type="xacml:ResourcesType"/>
<xs:complexType name="ResourcesType">
<xs:choice>
<xs:element ref="xacml:Resource" maxOccurs="unbounded"/>
<xs:element ref="xacml:AnyResource"/>
</xs:choice>
</xs:complexType>
1676
The <Resources> element is of ResourcesType complex type.
1677
The <Resources> element consists of the following elements:
1678
<Resource> [Required]
1679
1680
A disjunctive sequence of one or more matching specifications against resource attributes
in the request context.
draft-xacml-specification-16a.doc
40
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
<AnyResource> [Required]
An element matching any resource attribute in the request context.
6.9. Element <Resource>
The <Resource> element is a conjunctive sequence of individual matches against the resource
attributes in the request context.
<xs:element name="Resource" type="xacml:ResourceType"/>
<xs:complexType name="ResourceType">
<xs:sequence>
<xs:element ref="xacml:ResourceMatch" maxOccurs="unbounded"/>
</xs:sequence>
</xs:complexType>
1692
The <Resource> element is of ResourceType complex type.
1693
The <Resource> element contains the following elements:
1694
<ResourceMatch> [One to Many]
1695
1696
1697
A conjunctive sequence of individual matches with the resource attributes in the request
context.
6.10. Element <ResourceMatch>
1698
1699
The <ResourceMatch> element identifies a set of resource-related entities by matching values in
the <Resource> element of the request context with values embedded in the <Policy> element.
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
<xs:element name="ResourceMatch" type="xacml:ResourceMatchType"/>
<xs:complexType name="ResourceMatchType">
<xs:sequence>
<xs:choice>
<xs:element ref="xacml:ResourceAttributeDesignator"/>
<xs:element ref="xacml:AttributeSelector"/>
</xs:choice>
<xs:element ref="xacml:AttributeValue"/>
</xs:sequence>
<xs:attribute name="MatchId" type="xs:QName" use="required"/>
</xs:complexType>
1711
The <ResourceMatch> element is of ResourceMatchType complex type.
1712
The <ResourceMatch> element contains the following attributes and elements:
1713
MatchId [Required]
1714
1715
1716
1717
1718
1719
Specifies a matching function. Value of this attribute MUST be of type Qname, with legal
values documented in Appendix A.
<ResourceAttributeDesignator> [Required]
Identifies one or more values in the <Resource> element of the <xacmlcontext:Request> element.
<AttributeSelector> [Required]
draft-xacml-specification-16a.doc
41
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
MAY be used to identify one or more values in the <Resource> element of the <xacmlcontext:Request> element. It MUST contain a legal xpath expression over the
<Resource> element of the <xacml-context:Request> element.
6.11. Element <Actions>
The <Actions> element is a child of the <Target> element and is a wrapper for the disjunctive
sequence of the <Action> elements. The <Actions> element is combined by logical ‘AND’ with
other children of the <Target> element.
<xs:element name="Actions" type="xacml:ActionsType"/>
<xs:complexType name="ActionsType">
<xs:choice>
<xs:element ref="xacml:Action" maxOccurs="unbounded"/>
<xs:element ref="xacml:AnyAction"/>
</xs:choice>
</xs:complexType>
1734
The <Actions> element is of ActionsType complex type.
1735
The <Actions> element contains the following elements:
1736
<Action> [Required]
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
A disjunctive sequence of one or more matching specifications against action attributes in
the request context.
<AnyAction> [Required]
An element matching any action attribute in the request context.
6.12. Element <Action>
The <Action> element is a conjunctive sequence of individual matches against the action
attributes in the request context.
<xs:element name="Action" type="xacml:ActionType"/>
<xs:complexType name="ActionType">
<xs:sequence>
<xs:element ref="xacml:ActionMatch" maxOccurs="unbounded"/>
</xs:sequence>
</xs:complexType>
1750
The <Action> element is of ActionType complex type.
1751
The <Action> element contains the following elements:
1752
<ActionMatch> [One to Many]
1753
1754
1755
1756
1757
1758
1759
A conjunctive sequence of individual action matches with the action in the request
context.
6.13. Element <ActionMatch>
The <ActionMatch> element identifies a set of action-related entities by matching values in the
<Action> element of the context with values embedded in the <Policy> element.
<xs:element name="ActionMatch" type="xacml:ActionMatchType"/>
<xs:complexType name="ActionMatchType">
draft-xacml-specification-16a.doc
42
1760
1761
1762
1763
1764
1765
1766
1767
1768
<xs:sequence>
<xs:choice>
<xs:element ref="xacml:ActionAttributeDesignator"/>
<xs:element ref="xacml:AttributeSelector"/>
</xs:choice>
<xs:element ref="xacml:AttributeValue"/>
</xs:sequence>
<xs:attribute name="MatchId" type="xs:QName" use="required"/>
</xs:complexType>
1769
The <ActionMatch> element is of ActionMatchType complex type.
1770
The <ActionMatch> element contains the following attributes and elements:
1771
MatchId [Required]
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
Specifies a matching function. The value of this attribute MUST be of type Qname, with
legal values documented in Appendix A.
<ActionAttributeDesignator> [Required]
Identifies one or more values in the <Resource> element of the <xacmlcontext:Request> element.
<AttributeSelector> [Required]
MAY be used to identify one or more values in the <Action> element of the <xacmlcontext:Request> element. It MUST contain a legal xpath expression over the
<Resource> element of <xacml-context:Request> element.
6.14. Element <PolicySetIdReference>
The <PolicySetIdReference> element is used to reference a <PolicySet> element by id. If
<PolicySetIdReference> is a URI, then it MAY be resolvable to the <PolicySet>. The
mechanism for resolving a policy set reference to the corresponding policy set is implementation
dependent. Applications MAY use the xacml SAML protocol extension to query
<PolicySetStatement> by id.
<xs:element name="PolicySetIdReference" type="xs:anyURI"/>
Element <PolicySetIdReference> is of xs:anyURI simple type.
6.15. Element <PolicyIdReference>
The <xacml:PolicyIdReference> element is used to reference a <Policy> element by id. If
<PolicyIdReference> is a URI, then it MAY be resolvable to the <Policy>. The mechanism
for resolving a policy reference to the corresponding policy is implementation dependent.
Applications MAY use the xacml SAML protocol extension to query <PolicyStatement> by id.
<xs:element name="PolicyIdReference" type="xs:anyURI"/>
Element <PolicyIdReference> is of xs:anyURI simple type.
6.16. Element <Policy>
The <Policy> element is the smallest entity that can be presented to the PDP for evaluation.
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The main components of this element are the <Target>, <Rule>, and <Obligations> elements
and the RuleCombiningAlgId attribute.
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1802
1803
The <Target> element defines <Policy> applicability to decision requests. A sequence of
<Rule> elements specifies authorizations that MUST be combined according to the
RuleCombiningAlgId attribute. The <Obligations> element contains a set of obligations
that MUST be discharged by the PDP in conjunction with the authorization decision.
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<xs:element name="Policy" type="xacml:PolicyType"/>
<xs:complexType name="PolicyType">
<xs:sequence>
<xs:element ref="xacml:Description" minOccurs="0"/>
<xs:element ref="xacml:PolicyDefaults" minOccurs="0"/>
<xs:element ref="xacml:Target"/>
<xs:element ref="xacml:Rule" minOccurs="0"
maxOccurs="unbounded"/>
<xs:element ref="xacml:Obligations" minOccurs="0"/>
</xs:sequence>
<xs:attribute name="PolicyId" type="xs:anyURI" use="required"/>
<xs:attribute name="RuleCombiningAlgId" type="xs:anyURI"
use="required"/>
</xs:complexType>
1818
The <Policy> element is of PolicyType complex type.
1819
The <Policy> element contains the following attributes and elements:
1820
PolicyId [Required]
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1823
1824
Policy identifier. The party assigning this identifier MUST minimize the potential of some
other party reusing the same identifier. This MAY be achieved by following a predefined
URN or URI scheme. It is OPTIONAL for the PolicyId URI to be resolvable to the
corresponding <Policy> object.
1825
RuleCombiningAlgId [Required]
1826
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1828
The identifier of the rule-combining algorithm by which the <Policy> components MUST be
combined. Standard rule-combining algorithms are listed in Appendix C. Standard rulecombining algorithm identifiers are listed in Section B.10.<Description> [Optional]
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1831
1832
1833
A free-form description of the policy.
<PolicyDefaults> [Optional]
Defines a set of default values applicable to the policy. The scope of
<PolicyDefaults> element is the enclosing policy.
<Target> [Required]
1834
The <Target> element defines the applicability of a <Policy> to decision requests.
1835
1836
1837
The <Target> element MAY be declared by the creator of the <Policy> element, or it
MAY be computed from the <Target> elements of the referenced <Rule> elements either
as an intersection or as a union.
1838
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1840
1841
<Rule> [Any Number]
A sequence of authorizations that MUST be combined according to the
RuleCombiningAlgId attribute. Rules with <Target> elements matching the decision
request MUST be considered. Rules with <Target> elements that do not match the
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decision request MUST NOT be considered. Applicability of rules to the decision
request is detailed in Appendix C.
<Obligations> [Optional]
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A conjunctive sequence of obligations that MUST be discharged by the PEP in
conjunction with the authorization decision. If the PEP does not understand the
obligations, then it MUST act as if the PDP denied access to the requested resource.
6.17. Element <Rule>
The <Rule> element defines individual rules in the policy. The main components of this element
are the <Target> and <Condition> elements, and the Effect attribute.
<xs:element name="Rule" type="xacml:RuleType"/>
<xs:complexType name="RuleType">
<xs:sequence>
<xs:element ref="xacml:Description" minOccurs="0"/>
<xs:element ref="xacml:Target" minOccurs="0"/>
<xs:element ref="xacml:Condition" minOccurs="0"/>
</xs:sequence>
<xs:attribute name="RuleId" type="xs:anyURI" use="required"/>
<xs:attribute name="Effect" type="xacml:EffectType"
use="required"/>
</xs:complexType>
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1862
The <Rule> element is of RuleType complex type.
1863
The <Rule> element contains the following attributes and elements:
1864
RuleId
1865
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1880
1881
A URN identifying this rule.
Effect
Rule effect. Values of this attribute are either “Permit” or “Deny”.
<Description> [optional]
A free-form description of the rule.
<Target> [optional]
Identifies the set of decision requests that the <Rule> element is intended to evaluate. If
this element is omitted, then the target for the <Rule> is defined by the enclosing
<Policy> element. See Section 6.4for details.
<Condition> [optional]
A predicate that MUST be satisfied for the rule to be assigned its Effect value. A
condition is a boolean function over a combination of subject, resource and
environment attributes or other functions.
6.18. Simple type EffectType
The EffectType simple type defines the values allowed for the Effect attribute of the <Rule>
element and for the FulfillOn attribute of the <Obligation> element.
<xs:simpleType name="EffectType">
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1886
1887
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1889
1890
1891
1892
1893
1894
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1900
1901
1902
1903
1904
1905
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1911
1912
1913
<xs:restriction base="xs:string">
<xs:enumeration value="Permit"/>
<xs:enumeration value="Deny"/>
</xs:restriction>
</xs:simpleType>
6.19. Element <Condition>
The <Condition> element is a boolean function over subject, resource, action and
environment attributes or functions of attributes. If the <Condition> element evaluates to
"True", then the enclosing <Rule> element is assigned its Effect value.
<xs:element name="Condition" type="xacml:ApplyType"/>
The <Condition> element if of ApplyType complex type.
6.20. Element <Apply>
The <Apply> element denotes application of a function to its arguments, thus encoding a function
call. The <Apply> element can be applied to any combination of <Apply>,
<AttributeValue>, <SubjectAttributeDesignator>,
<SubjectAttributeDesignatorWhere>, <ResourceAttributeDesignator>,
<ActionAttributeDesignator>, <EnvironmentAttributeDesignator> and
<AttributeSelector> arguments.
<xs:element name="Apply" type="xacml:ApplyType"/>
<xs:complexType name="ApplyType">
<xs:choice minOccurs="0" maxOccurs="unbounded">
<xs:element ref="xacml:Apply"/>
<xs:element ref="xacml:AttributeValue"/>
<xs:element ref="xacml:SubjectAttributeDesignatorWhere"/>
<xs:element ref="xacml:SubjectAttributeDesignator"/>
<xs:element ref="xacml:ResourceAttributeDesignator"/>
<xs:element ref="xacml:ActionAttributeDesignator"/>
<xs:element ref="xacml:EnvironmentAttributeDesignator"/>
<xs:element ref="xacml:AttributeSelector"/>
</xs:choice>
<xs:attribute name="FunctionId" type="xs:QName" use="required"/>
</xs:complexType>
1914
1915
The <Apply> element is of ApplyType complex type. The top-level element of the ApplyType is
a <Condition> element described in Section6.19.
1916
The <Apply> element contains the following attributes and elements:
1917
FunctionId [Required]
1918
1919
1920
The QName of a function. Xacml-defined functions are described in Appendix A.
<Apply> [Optional]
A nested function-call argument.
1921
<AttributeValue> [Optional]
1922
A literal value argument.
1923
1924
<SubjectAttributeDesignatorWhere>
A subject attribute argument.
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1926
<SubjectAttributeDesignator> [Optional]
A subject attribute argument.
1927
<ResourceAttributeDesignator> [Optional]
1928
A resource attribute argument.
1929
<ActionAttributeDesignator> [Optional]
1930
An action attribute argument.
1931
<EnvironmentAttributeDesignator> [Optional]
1932
An environment attribute argument.
1933
1934
1935
<AttributeSelector> [Optional]
An attribute selector argument.
6.21. Complex type AttributeDesignatorType
1936
1937
1938
Elements of the AttributeDesignatorType complex type are used as a pointing device into various
elements of the <xacml-context:Request> element. <AttributeDesignatorType> is an
XML syntax alternative to the xpath expressions used by the <AttributeSelector> element.
1939
1940
1941
Elements of AttributeDesignatorType type select a set of attributes from the request context,
each of them having the same AttributeId value. As such, the attribute designator semantics
are identical to those of an xpath expression.
1942
1943
1944
1945
1946
1947
<xs:complexType name="AttributeDesignatorType">
<xs:attribute name="AttributeId" type="xs:anyURI"
use="required"/>
<xs:attribute name="DataType" type="xs:anyURI" use="required"/>
<xs:attribute name="Issuer" type="xs:anyURI" use="optional"/>
</xs:complexType>
1948
The <AttributeDesignatorType> contains the following attributes:
1949
AttributeId [Required]
1950
The attribute identifier selecting an attribute within the <xacml-context:Request> element.
1951
DataType [Required]
1952
1953
The data type for interpreting the corresponding attribute value in the <xacmlcontext:Request> element.
1954
Issuer [Optional]
1955
1956
1957
1958
1959
1960
The authority that issued the attribute.
6.22. Element <SubjectAttributeDesignator>
The <SubjectAttributeDesignator> element selects a set of subject attribute values having
the same attribute identifier from within all <Subject> elements of the <xacmlcontext:Request> element. As such, the <SubjectAttributeDesignator> element
behaves like an xpath expression.
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1962
1963
1964
Note that because the <xacml-context:Request> element MAY have multiple <xacmlcontext:Subject> elements, attribute values from all of them are selected. The
<SubjectAttributeDesignatorWhere> element provides a way to narrow down this selection
to a specific subject.
1965
1966
The <SubjectAttributeDesignator> element is used by the <SubjectMatch> element and
can be passed to the <Apply> element as an argument.
1967
1968
1969
1970
<xs:element name="SubjectAttributeDesignator"
type="xacml:AttributeDesignatorType"/>
The <SubjectAttributeDesignator> element is of AttributeDesignatorType complex type.
6.23. Element <ResourceAttributeDesignator>
1971
1972
1973
1974
The <ResourceAttributeDesignator> element selects a set of resource attribute values
having the same attribute identifier from within <Resource> element of the <xacmlcontext:Request> element. As such, the <ResourceAttributeDesignator> element
behaves like an xpath expression.
1975
1976
The <ResourceAttributeDesignator> element is used by the <ResourceMatch> element
and can be passed to the <Apply> element as an argument.
1977
1978
1979
1980
<xs:element name="ResourceAttributeDesignator"
type="xacml:AttributeDesignatorType"/>
The <ResourceAttributeDesignator> element is of AttributeDesignatorType complex type.
6.24. Element <ActionAttributeDesignator>
1981
1982
1983
1984
The <ActionAttributeDesignator> element selects a set of action attribute values having
the same attribute identifier from within the <Action> element of the <xacmlcontext:Request> element. As such, the <ActionAttributeDesignator> element
behaves like an xpath expression.
1985
1986
The <ActionAttributeDesignator> element is used by the <ActionMatch> element and
can be passed to the <Apply> element as an argument.
1987
1988
1989
1990
<xs:element name="ActionAttributeDesignator"
type="xacml:AttributeDesignatorType"/>
The <ActionAttributeDesignator> element is of AttributeDesignatorType complex type.
6.25. Element <EnvironmentAttributeDesignator>
1991
1992
1993
1994
The <EnvironmentAttributeDesignator> element selects a set of environment attribute
values having the same attribute identifier from within the <Environment> element of the
<xacml-context:Request> element. As such, the <EnvironmentAttributeDesignator>
element behaves like an xpath expression.
1995
1996
The <EnvironmentAttributeDesignator> element can be passed to the <Apply> element
as an argument.
1997
1998
<xs:element name="EnvironmentAttributeDesignator"
type="xacml:AttributeDesignatorType"/>
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2000
2001
The <EnvironmentAttributeDesignator> element is of AttributeDesignatorType complex
type.
6.26. Element <SubjectAttributeDesignatorWhere>
2002
2003
The element <SubjectAttributeDesignatorWhere> specifies additional subject matches
when a subject attribute value is selected from the <xacml-contex:Request> element.
2004
2005
2006
Because the <xacml-context:Request> element MAY contain multiple <xacmlcontext:Subject> elements, the <SubjectAttributeDesignatorWhere> element provides
a way to focus the subject attribute selection on a particular subject.
2007
2008
2009
2010
The <SubjectAttributeDesignatorWhere> element is designed to make Complex selections
such as: Select the attribute value for the subject attribute whose id is “A”, such that the attribute
value for the subject attribute whose id is “B” is “valueB” and the attribute value for the subject
attribute whose id is “C” is “valueC”.
2011
Every subject match narrows down a set of attributes selected by the previous match.
2012
2013
Element <SubjectAttributeDesignatorWhere> is passed as an argument to the <Apply>
element.
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
<xs:element name="SubjectAttributeDesignatorWhere"
type="xacml:SubjectAttributeDesignatorWhereType"/>
<xs:complexType name="SubjectAttributeDesignatorWhereType">
<xs:complexContent>
<xs:extension base="xacml:AttributeDesignatorType">
<xs:sequence>
<xs:element ref="xacml:SubjectMatch" minOccurs="0"/>
</xs:sequence>
</xs:extension>
</xs:complexContent>
</xs:complexType>
2026
2027
The <SubjectAttributeDesignatorWhere> element is of
SubjectAttributeDesignatorWhereType complex type.
2028
2029
In addition to its base type, the <SubjectAttributeDesignatorWhere> element contains the
following elements:
2030
<SubjectMatch> [Any Number]
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
A conjunctive sequence of matches against the <Subject> element of the <xacmlcontext:Request> element. Each subject match in a sequence narrows down a set of
subject attributes selected by the previous match.
6.27. Element <AttributeSelector>
The <AttributeSelector> element is a free-form pointing device into the <xacmlcontext:Request> element. It uses xpath syntax to select elements from the request context.
There are no restrictions on the xpath. However, the full power of the xpath syntax should be used
with care: a policy writer MUST ensure that, when the <AttributeSelector> element is used in
place of one of the elements of type AttributeDesignatorType, it is pointing to the correct section
of the <xacml-context:Request> element. Support for the <AttributeSelector>
element is OPTIONAL.
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2044
2045
2046
2047
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2049
2050
<xs:element name="AttributeSelector"
type="xacml:AttributeSelectorType"/>
<xs:complexType name="AttributeSelectorType">
<xs:attribute name="RequestContextPath" type="xs:anyURI"
use="required"/>
<xs:attribute name="DataType" type="xs:anyURI" use="required"/>
<xs:attribute name="XPathVersion" type="xs:anyURI"
use="optional"/>
</ xs:complexType>
2051
The <AttributeSelector> element is of AttributeSelectorType complex type.
2052
The <AttributeSelector> element has the following attributes:
2053
RequestContextPath [Required]
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
An Xpath expression into the request context. There is no restriction on the xpath syntax.
DataType [Required]
The data type of the selected item. It could be an xml-schema-defined data type or any
other derived data type.
XpathVersion [Optional]
Xpath version. The default value for this attribute is: http://www.w3.org/TR/1999/Recxpath-19991116, which is xpath 1.0. It could be overwritten by another value or by the
<XpathVersion> element of the <PolicySetDefaults> element..
6.28. Element <AttributeValue>
The <AttributeValue> element contains a literal attribute value. The type of the value MUST
be contained in the DataType attribute.
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
<xs:element name="AttributeValue"
type="xacml:AttributeValueType"/>
<xs:complexType name="AttributeValueType">
<xs:complexContent>
<xs:extension base="xs:anyType">
<xs:attribute name="DataType" type="xs:anyURI"
use="required"/>
</xs:extension>
</xs:complexContent>
</xs:complexType>
2075
The <AttributeValue> element is of AttributeValueType complex type.
2076
The <AttributeValue> element contains the following attributes:
2077
DataType [required]
2078
2079
2080
2081
2082
2083
The type of the value. The attribute MAY be one of the xml-schema-defined types.
Alternatively, it MAY be of a structured type defined in some other namespace.
6.29. Element <Obligations>
The <Obligations> element contains a set of <Obligation> elements. A PEP MUST fulfill all
obligations returned by the PDP. If a PEP does not understand an obligation, then it MUST act
as if the PDP had returned a “Deny” authorization decision.
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2085
2086
2087
2088
2089
<xs:element name="Obligations" type="xacml:ObligationsType"/>
<xs:complexType name="ObligationsType">
<xs:sequence>
<xs:element ref="xacml:Obligation" maxOccurs="unbounded"/>
</xs:sequence>
</xs:complexType>
2090
The <Obligations> element is of ObligationsType complexType.
2091
<Obligation> [One to Many]
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
A sequence of obligations that MUST be fulfilled by the PEP. If the PEP does not
understand an obligation, then it MUST act as if the PDP had returned a “Deny”
authorization decision.
6.30. Element <Obligation>
The <Obligation> element contains an identifier for the obligation and a set of attributes that
form arguments of the action defined by the obligation. The FulfillOn attribute indicates the
decision value for which this obligation MUST be fulfilled.
<xs:element name="Obligation" type="xacml:ObligationType"/>
<xs:complexType name="ObligationType">
<xs:choice maxOccurs="unbounded">
<xs:element ref="xacml:AttributeAssignment"/>
</xs:choice>
<xs:attribute name="ObligationId" type="xs:anyURI"
use="required"/>
<xs:attribute name="FulfilOn" type="xacml:EffectType"
use="required"/>
</xs:complexType>
2109
The <Obligation> element is of ObligationType complexType.
2110
The ObligationId [required]
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
Obligation identifier. The value of the obligation identifier is interpreted by the PEP.
FulfillOn [required]
The decision value for which this obligation MUST be fulfilled.
<AttributeAssignment> [required]
Obligation arguments assignment. The values of the obligation arguments are
interpreted by the PEP.
6.31. Element <AttributeAssignment>
The <AttributeAssignment> element contains an AttributeId and the corresponding
attribute value. The AttributeId is part of attribute meta-data, and is used when the attribute
cannot be referenced by its location in the <xacml-context:Request>. This situation may arise
in an <Obligation> element if the obligation includes parameters.
<xs:element name="AttributeAssignment"
type="xacml:AttributeAssignmentType"/>
<xs:complexType name="AttributeAssignmentType">
<xs:complexContent>
<xs:extension base="xacml:AttributeValueType">
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2128
2129
2130
2131
<xs:attribute name="AttributeId" type="xs:anyURI"
use="required"/>
</xs:extension>
</xs:complexContent>
</xs:complexType>
2132
The <AttributeAssignment> element is of AttributeAssignmentType complex type.
2133
AttributeId [Required]
2134
2135
2136
2137
2138
2139
The attribute Identifier
DataType [Required]
The data type for the assigned value.
7. Context syntax (normative with the exception of
the schema fragments)
7.1. Element <Request>
2140
2141
2142
The <Request> element is a top-level element in the XACML context schema. A <Request>
element is an abstraction layer used by the policy language. Any proprietary system using the
XACML specification MUST transform its input into the xacml context request form.
2143
2144
The <Request> element consists of four sections denoted by the <Subject>, <Resource>,
<Action>, and <Environment> elements.
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
<xs:element name="Request" type="xacml-context:RequestType"/>
<xs:complexType name="RequestType">
<xs:sequence>
<xs:element ref="xacml-context:Subject"
maxOccurs="unbounded"/>
<xs:element ref="xacml-context:Resource"/>
<xs:element ref="xacml-context:Action"/>
<xs:element ref="xacml-context:Environment" minOccurs="0"/>
</xs:sequence>
</xs:complexType>
2155
The <Request> element is of RequestType complex type.
2156
The <Request> element contains the following elements:
2157
<Subject> [One to Many]
2158
2159
2160
Identifies a subject in the request context. One or more <Subject> elements are
allowed. Each <Subject> element MUST contain a number of predefined <Attribute>
elements. It MAY contain additional <Attribute> elements.
2161
[Issue: list required attributes]
2162
2163
<Resource> [Required]
Contains information about the resource to which access is being requested. It MAY
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2165
include a <ResourceContent> element, and it MUST contain a number of predefined
<Attribute> elements. Additional <Attribute> elements MAY be included.
2166
[Issue: list required attributes]
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
<Action> [Required]
Identifies the requested action by listing a set of <Attribute> elements associated with
the action.
<Environment> [Optional]
Contains a set of <Attribute> elements of the environment. These <Attribute>
elements MAY form a part of policy evaluation.
7.2. Element <Subject>
The <Subject> element specifies a subject of a decision request context by listing a sequence
of <Attribute> elements associated with the subject.
<xs:element name="Subject" type="xacml-context:SubjectType"/>
<xs:complexType name="SubjectType">
<xs:sequence>
<xs:element ref="xacml-context:Attribute" minOccurs="0"
maxOccurs="unbounded"/>
</xs:sequence>
</xs:complexType>
2183
The <Subject> element is of SubjectType complex type.
2184
<Attribute> [Any Number]
2185
2186
A sequence of attributes associated with the subject. A number of attributes MUST be
present for each <Subject> element upon construction of the request context.
2187
[Issue: Describe required attributes]
2188
7.3. Element <Resource>
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
The <Resource> element encapsulates the requested resource and lists a sequence of
<Attribute> elements associated with that resource and optional resource content.
<xs:element name="Resource" type="xacml-context:ResourceType"/>
<xs:complexType name="ResourceType">
<xs:sequence>
<xs:element ref="xacml-context:ResourceContent"
minOccurs="0"/>
<xs:element ref="xacml-context:Attribute" minOccurs="0"
maxOccurs="unbounded"/>
</xs:sequence>
</xs:complexType>
2200
The <Resource> element is of ResourceType complex type.
2201
The <Resource> element contains the following elements:
2202
<ResourceContent> [Optional]
2203
The resource content.
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2205
2206
2207
<Attribute> [Any Number]
A sequence of resource attributes. A number of <Attribute> elements MUST be
included. Additional <Attribute> elements MAY be present.
7.4. Element <ResourceContent>
2208
2209
2210
The <ResourceContent> element is a notional placeholder for the resource content. If an xacml
policy references the contents of the resource, then the <ResourceContent> element is used
as the reference point.
2211
2212
2213
2214
2215
2216
2217
<xs:complexType name="ResourceContentType">
<xs:sequence>
<xs:any namespace="##any" processContents="lax" minOccurs="0"
maxOccurs="unbounded"/>
</xs:sequence>
<xs:anyAttribute namespace="##any" processContents="lax"/>
</xs:complexType>
2218
The <ResourceContent> element is of ResourceContentType complex type.
2219
The <ResourceContent> element allows arbitrary elements and attributes.
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
7.5. Element <Action>
The <Action> element identifies the requested action by listing a set of <Attribute> elements
associated with the action.
<xs:element name="Action" type="xacml-context:ActionType"/>
<xs:complexType name="ActionType">
<xs:sequence>
<xs:element ref="xacml-context:Attribute" minOccurs="0"
maxOccurs="unbounded"/>
</xs:sequence>
</xs:complexType>
2230
The <Action> element is of ActionType complex type.
2231
The <Attribute> [Any Number]
2232
Action attributes.
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
7.6. Element <Environment>
The <Environment> element contains a set of attributes of the environment. These attributes
MAY form part of policy evaluation.
<xs:element name="Environment" type="xacmlcontext:EnvironmentType"/>
<xs:complexType name="EnvironmentType">
<xs:sequence>
<xs:element ref="xacml-context:Attribute" minOccurs="0"
maxOccurs="unbounded"/>
</xs:sequence>
</xs:complexType>
2244
The <Environment> element is of EnvironmentType complex type.
2245
The <Environment> element contains the following elements:
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2246
2247
2248
2249
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<Attribute> [Any Number]
A list of environment attributes. Environment attributes are attributes that are not
associated with either the subject, resource or action.
7.7. Element <Attribute>
The <Attribute> element is a central abstraction of the request context. It contains an attribute
value and attribute meta-data. The attribute meta-data comprises the attribute identifier,
attribute issuer and attribute issue instant. Attribute designators and attribute selectors in the
policy refer to attributes by this meta-data.
<xs:element name="Attribute" type="xacml-context:AttributeType"/>
<xs:complexType name="AttributeType">
<xs:sequence>
<xs:element ref="xacml-context:AttributeValue" minOccurs="0"
maxOccurs="unbounded"/>
</xs:sequence>
<xs:attribute name="AttributeId" type="xs:anyURI"
use="required"/>
<xs:attribute name="Issuer" type="xs:string" use="optional"/>
<xs:attribute name="IssueInstant" type="xs:dateTime"
use="optional"/>
</xs:complexType>
2266
The <Attribute> element is of AttributeType complex type.
2267
The <Attribute> element contains the following attributes and elements:
2268
AttributeId [Required]
2269
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2285
Attribute identifier. A number of identifiers are reserved by XACML to denote commonly
used attributes.
Issuer [Optional]
Attribute issuer. This MAY be a URIthat binds to a public key, or some other identifier
exchanged out-of-band by issuing and relying parties.
IssueInstant [Optional]
Attribute issue instant.
7.8. Element <AttributeValue>
The <AttributeValue> element contains the value of an attribute.
<xs:element name="AttributeValue" type="xs:anyType"/>
The <AttributeValue> element is of xs:anyType type.
7.9. Element <Response>
The <Response> element encapsulates the authorization decision returned by the PDP. It
includes a sequence of one or more results with one <Result> element per requested resource.
Multiple results MAY be returned when the value of the “urn:oasis:xacml:1.0:resource:scope”
resource attribute in the request context is “Descendants”. Support for multiple results is
OPTIONAL.
draft-xacml-specification-16a.doc
55
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2292
<xs:element name="Response" type="xacml-context:ResponseType"/>
<xs:complexType name="ResponseType">
<xs:sequence>
<xs:element ref="xacml-context:Result"
maxOccurs="unbounded"/>
</xs:sequence>
</xs:complexType>
2293
The <Response> element is of ResponseType complex type.
2294
The <Response> element contains the following elements:
2295
<Result> [One to Many]
2296
2297
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2299
2300
2301
2302
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2311
An authorization decision result.
7.10. Element <Result>
The <Result> element represents an authorization decision result for the resource specified by
the ResourceURI attribute. It MAY include a set of obligations that MUST be fulfilled by the
PEP. If the PEP does not understand an obligation, then it MUST act as if the PDP had denied
access to the requested resource.
<xs:element name="Result" type="xacml-context:ResultType"/>
<xs:complexType name="ResultType">
<xs:sequence>
<xs:element ref="xacml-context:Decision"/>
<xs:element ref="xacml-context:Status" minOccurs="0"/>
<xs:element ref="xacml:Obligations" minOccurs="0"/>
</xs:sequence>
<xs:attribute name="ResourceURI" type="xs:anyURI"
use="optional"/>
</xs:complexType>
2312
The <Result> element is of ResultType complex type.
2313
The <Result> element contains the following attributes and elements:
2314
ResourceURI [Optional]
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
The URI for the requested resource. If this attribute is omitted, then the resource URI is
specified by the “urn:oasis:names:tc:xacml:1.0:resource:resource-uri” resource attribute in
the <Request> element.
<Decision> [Required]
The authorization decision
<Status> [Optional]
Indicates whether the request succeeded or not.
<Obligations> [Optional]
A list of obligations that MUST be discharged by the PEP. If the PEP does not
understand an obligation, then it MUST act as if the PDP had denied access to the
requested resource.
draft-xacml-specification-16a.doc
56
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2327
2328
2329
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2331
2332
2333
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2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
7.11. Element <Decision>
The <Decision> element contains the result of policy evaluation.
<xs:element name="Decision" type="xacml-context:DecisionType"/>
<xs:simpleType name="DecisionType">
<xs:restriction base="xs:string">
<xs:enumeration value="Permit"/>
<xs:enumeration value="Deny"/>
<xs:enumeration value="Indeterminate"/>
<xs:enumeration value="NotApplicable"/>
</xs:restriction>
</xs:simpleType>
The <Decision> element is of DecisionType simple type.
7.12. Element <Status>
The <Status> element represents the status of the authorization decision result.
<xs:element name="Status" type="xacml-context:StatusType"/>
<xs:complexType name="StatusType">
<xs:sequence>
<xs:element ref="xacml-context:StatusCode"/>
<xs:element ref="xacml-context:StatusMessage" minOccurs="0"/>
<xs:element ref="xacml-context:StatusDetail" minOccurs="0"/>
</xs:sequence>
</xs:complexType>
2348
The <Status> element is of StatusType complex type.
2349
The <Status> element contains the following elements:
2350
<StatusCode> [Required]
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
Status code.
<StatusMessage> [Optional]
A status message describing the status code.
<StatusDetail> [Optional]
Additional status information.
7.13. Element <StatusCode>
The <StatusCode> element contains a major status code value and an optional sequence of
minor status codes.
<xs:element name="StatusCode" type="xacmlcontext:StatusCodeType"/>
<xs:complexType name="StatusCodeType">
<xs:sequence>
<xs:element ref="xacml-context:StatusCode" minOccurs="0"/>
</xs:sequence>
<xs:attribute name="Value" type="xs:QName" use="required"/>
</xs:complexType>
The <StatusCode> element is of StatusCodeType complex type.
draft-xacml-specification-16a.doc
57
2368
The <StatusCode> element contains the following attributes and elements:
2369
Value [Required]
2370
2371
See Section B.9 for a list of values.
<StatusCode> [Any Number]
2372
Minor status code. This status code qualifies its parent status code.
7.14. Element <StatusMessage>
2373
2374
The <StatusMessage> element is a free-form description of the status code.
<xs:element name="StatusMessage" type="xs:string"/>
2375
2376
The <StatusMessage> element is of xs:string type.
7.15. Element <StatusDetail>
2377
2378
The <StatusDetail> element qualifies the <Status> element with additional information.
<xs:element name="StatusDetail" type="xacmlcontext:StatusDetailType"/>
<xs:complexType name="StatusDetailType">
<xs:sequence>
<xs:any namespace="##any" processContents="lax" minOccurs="0"
maxOccurs="unbounded"/>
</xs:sequence>
</xs:complexType>
2379
2380
2381
2382
2383
2384
2385
2386
2387
The <StatusDetail> element is of StatusDetailType complex type.
2388
The <StatusDetail> element allows arbitrary xml content.
2389
8. XACML extensibility points (non-normative)
2390
2391
This section describes the points within the XACML model and schema where extensions can be
added
8.1. URIs
2392
2393
The following XML attributes are URIs.
2394

Function,
2395

RuleCombiningAlgId,
2396

PolicyCombiningAlgId,
draft-xacml-specification-16a.doc
58
2398
9. Security and privacy considerations (nonnormative)
2399
2400
2401
2402
This section identifies possible security and privacy compromise scenarios that should be
considered when implementing an XACML-based system. The section is informative only. It is left
to the implementer to decide whether these compromise scenarios are practical in their
environment and to select appropriate safeguards.
2397
2403
9.1. Threat model
2404
2405
The general Internet threat model described in the IETF guidelines for security considerations [ref.]
is the basis for the XACML threat model.
2406
2407
We assume here that the adversary has access to the communication channel between the
XACML actors and is able to interpret, insert, delete and modify messages or parts of messages.
2408
2409
2410
2411
Additionally, an actor may use information from a former transaction maliciously in subsequent
transactions. It is further assumed that rules and policies are only as reliable as the actors that
produce them. Thus it is incumbent on each actor to establish appropriate trust in the other actors
upon which it relies. Mechanisms for trust establishment are outside the scope of this specification.
2412
2413
2414
2415
The messages that are transmitted between the actors in the XACML model are susceptible to
attack by malicious third parties. Other points of vulnerability include the PEP, the PDP and the
PAP. While some of these entities are not strictly within the scope of this specification, their
compromise could lead to the compromise of access control enforced by the PEP.
2416
2417
2418
It should be noted that there are other components of a distributed system that may be
compromised, such as an operating system and the domain-name system (DNS) that are outside
the scope of this discussion of threat models. And such compromise may lead to a policy violation.
2419
The following sections detail specific compromise scenarios that are relevant to an XACML system.
2420
9.1.1 Unauthorized disclosure
2421
2422
2423
2424
2425
2426
2427
XACML does not specify any inherent mechanisms for confidentiality of the messages exchanged
between actors. Therefore, an adversary could observe the messages in transit. Under certain
security policies, disclosure of this information is a violation. Disclosure of attributes or the types
of decision requests that a subject makes may be a breach of privacy policy. In the commercial
sector, the consequences of unauthorized disclosure of personal data may range from
embarrassment to the custodian to imprisonment and large fines in the case of medical or financial
data.
2428
Unauthorized disclosure is addressed by confidentiality mechanisms.
2429
9.1.2 Impersonation
2430
2431
2432
2433
2434
9.1.3 Message replay
A message replay attack is one in which the adversary records and replays legitimate messages
between XACML actors. This attack may lead to denial of service, the use of out-of-date
information or impersonation.
draft-xacml-specification-16a.doc
59
2435
Prevention of replay attacks requires the use of message freshness mechanisms.
2436
2437
Note that encryption of the message does not mitigate a replay attack since the message is just
replayed and does not have to be understood by the adversary.
2438
9.1.4 Message insertion
2439
2440
A message insertion attack is one in which the adversary inserts messages in the sequence of
messages between XACML actors.
2441
2442
2443
2444
2445
The solution to a message insertion attack is to use mutual authentication and a message integrity
mechanism between the actors. It should be noted that just using SSL mutual authentication is not
sufficient. This only proves that the other party is the one identified by the subject of the X.509
certificate. In order to be effective it is necessary to confirm that the certificate subject is authorized
to send the message.
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
9.1.5 Message deletion
A message deletion attack is one in which the adversary deletes messages in the sequence of
messages between XACML actors. Message deletion may lead to denial of service. However, a
properly designed XACML system should not render an incorrect authorization decision as a
result of a message deletion attack.
The solution to a message deletion attack is to use a message integrity mechanism between the
actors.
9.1.6 Message modification
If an adversary can intercept a message and change its contents they may be able to alter an
authorization decision. Message integrity mechanisms can prevent a successful message
modification attack.
9.1.7 Resource matching
2459
2460
2461
2462
2463
2464
2465
It is vital that the matching algorithm used by the PDP to identify the applicable policy based on
the target resource be functionally equivalent to the one used by the PEP to form the decision
request. This requirement applies particularly in the case where the <Decision> value of
“NotApplicable” is treated as equivalent to the value “Permit” (as is common in many Web servers).
This situation does not usually occur when the PEP intercepts the decision request at the point of
execution, but is frequently an issue if the PEP is implemented as a proxy or filter by developers
other than those that developed the resource server.
2466
2467
2468
2469
2470
2471
2472
A common example of this behavior is found in Web servers. Commercial http responders permit a
variety of syntaxes to be treated equivalently. The “%” character can be used to represent
characters by hex value. In the URL path, the character string: “/../” provides multiple ways of
specifying the same value. Multiple character sets may be permitted and in some cases, the same
printed character can be represented by different binary values. If the target-matching algorithm
considers two resource strings to be different, and the underlying Web server considers them to be
the same, this may result in unauthorized access.
2473
2474
2475
2476
The usual solution to this problem is to put the decision request in a canonical form before
matching. There may be practical difficulties with this strategy if the transformations are not
completely documented or subject to change without notice from one version to the next.
Therefore, it is important to be aware of this issue and perform careful checking of marginal cases.
draft-xacml-specification-16a.doc
60
9.1.8 Negative rules
2477
2478
2479
2480
2481
2482
A negative rule is one that is based on a predicate not being "True". If not used with care,
negative rules can lead to policy violation, therefore some authorities recommend that they NOT be
used. However, negative rules can be extremely efficient in certain cases, so XACML has chosen
to include them. Nevertheless, it is recommended that they be used with care and avoided if
possible.
2483
2484
2485
2486
2487
2488
2489
2490
2491
A common use for negative rules is to deny access to an individual or subgroup when their
membership in a larger group would otherwise permit them access. For example, we might want to
write a rule that allows all Vice Presidents to see the unpublished financial data, except for Joe,
who is only a Ceremonial Vice President and can be indiscreet in his communications. If we have
complete control of the administration of subject attributes, a superior approach would be to
define “Vice President” and “Ceremonial Vice President” as distinct groups and then define rules
accordingly. However, in some environments this approach may not be feasible. (It is worth noting
in passing that, generally speaking, referring to individuals in rules does not scale well. Generally,
shared attributes are preferred.)
2492
2493
2494
2495
2496
2497
2498
If not used with care, negative rules can lead to policy violation in two common cases. They are:
when attributes are suppressed and when the base group changes. An example of suppressed
attributes would be if we have a policy that access should be permitted, unless the subject is a
credit risk. If it is possible that the attribute of being a credit risk may be unknown to the PDP for
some reason, unauthorized access may be permitted. In some environments, the subject may be
able to suppress the publication of attributes by the application of privacy controls, or the server or
repository that contains the information may be unavailable for accidental or intentional reasons.
2499
2500
2501
2502
2503
2504
2505
2506
An example of a changing base group would be if there is a policy that everyone in the engineering
department may change software source code, except for secretaries. Suppose now that the
department were to merge with another engineering department and the intent is to maintain the
same policy. However, the new department also includes individuals identified as administrative
assistants, who ought to be treated in the same way as secretaries. Unless the policy is altered,
they will unintentionally be permitted to change software source code. Problems of this type are
easy to avoid when one individual administers all policies, but when administration is distributed,
as XACML allows, this type of situation must be explicitly guarded against.
9.2. Safeguards
2507
9.2.1 Authentication
2508
2509
2510
Authentication provides the means for one party in a transaction to determine the identity of the
other party in the transaction. Authentication may be in one direction, or it may be bilateral 1.
2511
2512
2513
Given the sensitive nature of access control systems, it is important for a PEP to authenticate the
identity of the PDP to which it sends decision requests. Otherwise, there is a risk that an
adversary could provide false or invalid authorization decisions, leading to a policy violation.
2514
2515
2516
2517
It is equally important for a PDP to authenticate the identity of the PEP and assess the level of trust
to determine what, if any, sensitive data should be passed. One should keep in mind that even
simple "Permit" or "Deny" responses could be exploited if an adversary were allowed to make
unlimited requests to a PDP.
1
Security and Privacy Considerations for the OASIS Security Assertion Markup Language (SAML)
section 4.1
draft-xacml-specification-16a.doc
61
2518
2519
2520
2521
Many different techniques may be used to provide authentication, such as co-located code, a
private network, a VPN or digital signatures. Authentication may also be performed as part of the
communication protocol used to exchange the contexts. In this case, authentication may be
performed at the message level or at the session level.
9.2.2 Confidentiality
2522
2523
2524
2525
2526
Confidentiality mechanisms ensure that the contents of a message can be read only by the desired
recipients and not by anyone else who encounters the message while it is in transit 2. There are two
areas in which confidentiality should be considered: one is confidentiality during transmission; the
other is confidentiality within a <Policy> element.
9.2.2.1
2527
Communication confidentiality
2528
2529
2530
2531
2532
2533
In some environments it is deemed good practice to treat all data within an access control system
as confidential. In other environments, policies may be made freely available for distribution,
inspection and audit. The idea behind keeping policy information secret is to make it more difficult
for an adverary to know what steps might be sufficient to obtain unauthorized access. Regardless
of the approach chosen, the security of the access control system should not depend on the
secrecy of the policy.
2534
2535
2536
2537
2538
Any security concerns or requirements related to transmitting or exchanging XACML <policy>
elements are outside the scope of the XACML standard. While it is often important to ensure that
the integrity and confidentiality of <policy> elements is maintained when they are exchanged
between two parties, it is left to the implementers to determine the appropriate mechanisms for their
environment.
2539
2540
2541
Communications confidentiality can be provided by a confidentiality mechanism, such as SSL.
Using a point-to-point scheme like SSL may lead to other vulnerabilities when one of the recipients
of a particular point-to-point hop is compromised.
9.2.2.2
2542
Statement level confidentiality
2543
2544
In some cases, an implementation may want to encrypt only parts of an XACML <Policy>
element.
2545
2546
2547
The XML Encryption Syntax and Processing Candidate Recommendation from W3C can be used
to encrypt all or parts of an XML document. This specification is recommended for use with
XACML.
2548
2549
2550
It should go without saying that if a repository is used to facilitate the communication of cleartext
(i.e., unencrypted) policy between the PAP and PDP, then a secure repository should be used to
store this sensitive data.
9.2.3 Policy integrity
2551
2552
2553
2554
2555
2556
The XACML policy, used by the PDP to evaluate the request context, is the heart of the system.
Therefore, maintaining its integrity is essential. There are two aspects to maintaining the integrity of
the policy. One is to ensure that <Policy> elements have not been altered since they were
originally created by the PAP. The other is to ensure that <Policy> elements have not been
inserted or deleted from the set of policies.
2
Security and Privacy Considerations for the OASIS Security Assertion Markup Language (SAML)
section 4.
draft-xacml-specification-16a.doc
62
2557
2558
2559
2560
2561
2562
In many cases, both aspects can be achieved by ensuring the integrity of the actors and
implementing session-level mechanisms to secure the communication between actors. The
selection of the appropriate mechanisms is left to the implementers. However, when policy is
distributed between organizations to be acted on at a later time, or when the policy travels with the
protected resource, it would be useful to sign the policy. In these cases, the XML Signature
Syntax and Processing standard from W3C is recommended to be used with XACML.
2563
2564
2565
2566
2567
2568
Digital signatures should only be used to ensure the integrity of the statements. Digital signatures
should not be use as a method of selecting or evaluating policy. That is, the PDP should not
request a policy based on who signed it or whether or not it has been signed (as such a basis for
selection would, itself, be a matter of policy). However, the PDP must verify that the key used to
sign the policy is one controlled by the purported issuer of the policy. The means to do this are
dependent on the specific signature technology chosen and are outside the scope of this document.
9.2.4 Message freshness
2569
2570
Timestamp or nonce.
9.2.5 Policy identifiers
2571
2572
2573
2574
2575
2576
2577
2578
2579
Since policies can be referenced by their identifiers, it is the responsibility of the PAP to ensure
that these are unique. Confusion between identifiers could lead to misidentification of the
applicable policy. This specification is silent on whether a PAP must generate a new identifier
when a policy is modified or may use the same identifier in the modified policy. This is a matter of
administrative practice. However, care must be taken in either case. If the identifier is reused,
there is a danger that other policies or policy sets that reference it may be adversely affected.
Conversely, if a new identifier is used, these other policies may continue to use the prior policy,
unless it is deleted. In either case the results may not be what the policy administrator intends.
9.2.6 Trust model
2580
2581
2582
2583
2584
2585
Discussions of authentication, integrity and confidentiality mechanisms necessarily assume an
underlying trust model: how can one actor come to believe that a given key is uniquely associated
with a specific, identified actor so that the key can be used to encrypt data for that actor or verify
signatures (or other integrity structures) from that actor? Many different types of trust model exist,
including strict hierarchies, distributed authorities, the Web, the bridge and so on.
2586
2587
It is worth considering the relationships between the various actors of the access control system in
terms of the interdependencies that do and do not exist.
2588
2589

None of the entities of the authorization system are dependent on the PEP. They may
collect data from it, for example authentication, but are responsible for verifying it.
2590
2591

The correct operation of the system depends on the ability of the PEP to actually enforce
policy decisions.
2592
2593
2594

The PEP depends on the PDP to correctly evaluate policies. This in turn implies that the
PDP is supplied with the correct inputs. Other than that, the PDP does not depend on the
PEP.
2595
2596

The PDP depends on the PAP to supply appropriate policies. The PAP is not dependent
on other components.
draft-xacml-specification-16a.doc
63
9.2.7 Privacy
2597
2598
2599
2600
2601
2602
2603
2604
2605
It is important to be aware that any transactions that occur with respect to access control may
reveal private information about the actors. For example, if an XACML policy states that certain
data may only be read by subjects with “Gold Card Member” status, then any transaction in which
a subject is permitted access to that data leaks information to an adversary about the subject's
status. Privacy considerations may therefore lead to encryption and/or to access control policies
surrounding the enforcement of XACML policy instances themselves: confidentiality-protected
channels for the request/response protocol messages, protection of subject attributes in storage
and in transit, and so on.
2606
2607
2608
Selection and use of privacy mechanisms appropriate to a given environment are outside the scope
of XACML. The decision regarding whether, how and when to deploy such mechanisms is left to
the implementers associated with the environment.
2609
10. Conformance (normative)
10.1. Introduction
2610
2611
Conformance claims MAY be made by either one of two components in the XACML model:
2612
2613
1. An implementation of a PAP that produces <Policy> elements that conform with the XACML
schema; and
2614
2615
2. An implementation of a PDP that produces authorization decisions in response to a request
context on the basis of XACML <Policy> elements that conform with the XACML schema.
2616
2617
PAPs MAY claim conformance with the XACML specification provided merely that they produce
schema-compliant policy statements.
2618
2619
PDPs MAY claim conformance with the XACML specification provided that they correctly execute
the XACML conformance test suite provided at:
…
2620
http://www.oasis-open.org/
2621
10.2. XACML test suite
2622
2623
An implementation that "successfully uses" the XACML specification MUST pass the test suite.
The test suite comprises three directories:
2624

Request context
2625

Policy
2626

Response context
2627
2628
The input context directory contains a set of text/xml/ xacmlContext:RequestType files that are
valid XACML input contexts.
2629
2630
The policy directory contains precisely one XACML policy file whose target is appropriate for each
of the input contexts.
2631
2632
The output context directory contains a set of text/xml/ xacmlContext:ResponseType files
containing the output contexts that correspond to the input contexts in the input context directory.
draft-xacml-specification-16a.doc
64
2633
2634
2635
A conformant XACML PDP implementation shall create an output context in response to each and
every input context. The output contexts are linked to the corresponding input contexts by the
request context ID attribute. [There’s no such thing at the moment.]
2636
2637
2638
XACML implementations that target a specific application domain (e.g., SAML or J2SE) may use a
tool or process that is not an integral part of the XACML implementation to convert between the
XACML contexts and its private data representation.
2639
2640
2641
Disclaimer: Implementers SHALL NOT consider the test cases provided in the XACML
conformance test suite as providing 100% test coverage. OASIS does not represent that a
conformant implementation will operate correctly in all respects nor that it is fit for its purpose.
2642
10.3. Conformance tables
2643
2644
This section lists those portions of the specification that MUST be included in an implementation of
a PDP that claims to conform with XACML v1.0.
2645
Note: "M" means mandatory-to-implement. "O" means optional.
2646
10.3.1
Namespace
xacml:Policy
xacml:Policy
xacml:Policy
xacml:Policy
xacml:Policy
xacml:Policy
xacml:Policy
xacml:Policy
xacml:Policy
xacml:Policy
xacml:Policy
xacml:Policy
xacml:Policy
xacml:Policy
xacml:Policy
xacml:Policy
xacml:Policy
xacml:Policy
xacml:Policy
xacml:Policy
xacml:Policy
xacml:Policy
xacml:Policy
xacml:Policy
xacml:Policy
xacml:Policy
xacml:Policy
xacml:Policy
xacml:Policy
xacml:Policy
xacml:Policy
xacml:Policy
xacml:Policy
xacml:Policy
Schema elements
Element
AbstractDefaults
Action
ActionAttributeDesignator
ActionMatch
Actions
AnyAction
AnyResource
AnySubject
Apply
AttributeAssignment
AttributeSelector
AttributeValue
Condition
Description
EnvironmentAttributeDesignator
Obligation
Obligations
Policy
PolicyDefaults
PolicyId
PolicySet
PolicySetDefaults
PolicySetId
Resource
ResourceAttributeDesignator
ResourceMatch
Resources
Rule
Subject
SubjectAttributeDesignator
SubjectAttributeDesignatorWhere
SubjectMatch
Subjects
Target
draft-xacml-specification-16a.doc
M/O
?
M
M
M
M
M
M
M
M
O
O
M
M
M
M
O
O
M
?
M
M
?
M
M
M
M
M
M
M
M
M
M
M
M
65
xacml:Policy
xacml:Context
xacml:Context
xacml:Context
xacml:Context
xacml:Context
xacml:Context
xacml:Context
xacml:Context
xacml:Context
xacml:Context
xacml:Context
xacml:Context
xacml:Context
xacml:Context
xacml:Context
xacml:Context
2647
2648
XPathVersion
Action
Attribute
AttributeValue
Decision
Environment
Obligations
Request
Resource
ResourceContent
Response
Result
Status
StatusCode
StatusDetail
StatusMessage
Subject
10.3.2
2650
Algorithms
The implementation MUST include the rule- and policy-combining algorithms marked "M".
Algorithm
Deny-Overrides
First-Applicable
Permit-Overrides
2649
O
M
M
M
M
M
O
M
M
O
M
M
O
O
O
O
M
10.3.3
M/O
M
M
M
Identifiers
The implementation MUST properly process those identifiers marked with an "M".
Identifier
urn:oasis:names:tc:xacml:1.0
urn:oasis:names:tc:xacml:1.0:auth-locality:dns-name
urn:oasis:names:tc:xacml:1.0:auth-locality:ip-address
urn:oasis:names:tc:xacml:1.0:conformance-test
urn:oasis:names:tc:xacml:1.0:context
urn:oasis:names:tc:xacml:1.0:datatype:numeric
urn:oasis:names:tc:xacml:1.0:datatype:rfc822name
urn:oasis:names:tc:xacml:1.0:datatype:ufs-path
urn:oasis:names:tc:xacml:1.0:datatype:x500name
urn:oasis:names:tc:xacml:1.0:environment:current-time
urn:oasis:names:tc:xacml:1.0:example:action
urn:oasis:names:tc:xacml:1.0:example:action:read
urn:oasis:names:tc:xacml:1.0:example:action:xml-ac
urn:oasis:names:tc:xacml:1.0:example:attribute
urn:oasis:names:tc:xacml:1.0:example:attribute:group
urn:oasis:names:tc:xacml:1.0:example:attribute:role
urn:oasis:names:tc:xacml:1.0:function
urn:oasis:names:tc:xacml:1.0:policy
urn:oasis:names:tc:xacml:1.0:policy-combining-algorithm:denyoverrides
urn:oasis:names:tc:xacml:1.0:policy-combining-algorithm:firstapplicable
urn:oasis:names:tc:xacml:1.0:policy-combining-algorithm:permitoverrides
urn:oasis:names:tc:xacml:1.0:resource:resource-location
draft-xacml-specification-16a.doc
M/O
M
M
O
M
M
M
M
M
M
M
O
O
O
O
O
O
M
M
M
M
M
M
66
urn:oasis:names:tc:xacml:1.0:resource:resource-uri
urn:oasis:names:tc:xacml:1.0:resource:simple-file-name
urn:oasis:names:tc:xacml:1.0:resource:xpath
urn:oasis:names:tc:xacml:1.0:rule-combining-algorithm:denyoverrides
urn:oasis:names:tc:xacml:1.0:rule-combining-algorithm:firstapplicable
urn:oasis:names:tc:xacml:1.0:rule-combining-algorithm:permitoverrides
urn:oasis:names:tc:xacml:1.0:status:missing-attribute
urn:oasis:names:tc:xacml:1.0:status:ok
urn:oasis:names:tc:xacml:1.0:status:processing-error
urn:oasis:names:tc:xacml:1.0:status:syntax-error
urn:oasis:names:tc:xacml:1.0:subject:authentication-method
urn:oasis:names:tc:xacml:1.0:subject:authentication-time
urn:oasis:names:tc:xacml:1.0:subject:key-info
urn:oasis:names:tc:xacml:1.0:subject:request-time
urn:oasis:names:tc:xacml:1.0:subject:session-start-time
urn:oasis:names:tc:xacml:1.0:subject:subject-category
urn:oasis:names:tc:xacml:1.0:subject:subject-id
urn:oasis:names:tc:xacml:1.0:subject:subject-id-qualifier
urn:oasis:names:tc:xacml:1.0:subject-category:access-subject
urn:oasis:names:tc:xacml:1.0:subject-category:codebase
urn:oasis:names:tc:xacml:1.0:subject-category:intermediary-subject
urn:oasis:names:tc:xacml:1.0:subject-category:recipient-subject
urn:oasis:names:tc:xacml:1.0:subject-category:requesting-machine
xs:Gregorian
xs:dayTimeDuration
xs:yearMonthDuration
2651
2652
10.3.4
M
M
M
M
M
O
O
O
O
M
M
M
M
M
M
M
M
M
O
O
O
O
M
O
O
Function identifier
The implementation MUST properly process those functions marked with an "M".
Function
function:integer-add
function:decimal-add
function:add-yearMonthDuration-to-date
function:add-yearMonthDuration-to-date
function:add-dayTimeDuration-to-time
function:add-yearMonthDuration-to dateTime
function:add-dayTimeDuration-to-dateTime
function:add-yearMonthDurations
function:add-dayTimeDurations
function:integer-subtract
function:decimal-subtract
function:date-subtract
function:subtract-yearMonthDuration-from-date
function:subtract-dayTimeDuration-from-date
function:time-subtract
function:subtract-dayTimeDuration-from-time
function:datetime-subtract
function:subtract-yearMonthDuration-from-dateTime
function:subtract-dayTimeDuration-from-dateTime
function:subtract-yearMonthDurations
function:subtract-dayTimeDurations
function:integer-multiply
draft-xacml-specification-16a.doc
M/O
M
M
O
O
O
O
O
O
O
M
M
O
O
O
O
O
O
O
O
O
O
M
67
function:decimal-multiply
function:multiply-yearMonthDurations
function:multiply-dayTimeDurations
function:integer-divide
function:decimal-divide
function:divide-yearMonthDurations
function:divide-dayTimeDurations
function:integer-mod
function:decimal-mod
function:round
function:floor
function:abs
function:integer
function:decimal
function:integer-equal
function:decimal-equal
function:boolean-equal
function:string-equal
function:rfc822Name-equal
function:x500Name-equal
function:date-equal
function:time-equal
function:datetime-equal
function:yearMonthDuration-equal
function:dayTimeDuration-equal
function:gregorian-equal
function:hex-binary-equal
function:base64-binary-equal
function:anyURI-equal
function:QName-equal
function:NOTATION-equal
function:numeric-not-equal
function:boolean-not-equal
function:string-not-equal
function:date-not-equal
function:time-not-equal
function:datetime-not-equal
function:yearMonthDuration-not-equal
function:dayTimeDuration-not-equal
function:gregorian-not-equal
function:hex-binary-not-equal
function:base64-binary-not-equal
function:anyURI-not-equal
function:QName-not-equal
function:NOTATION-not-equal
function:integer-greater-than
function:decimal-greater-than
function:string-greater-than
function:date-greater-than
function:time-greater-than
function:datetime-greater-than
function:yearMonthDuration-greater-than
function:dayTimeDuration-greater-than
function:integer-less-than
function:decimal-less-than
function:string-less-than
function:date-less-than
draft-xacml-specification-16a.doc
M
O
O
M
M
O
O
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
O
O
M
M
M
M
M
M
O
O
O
O
O
O
O
O
O
O
O
O
O
O
M
M
M
M
M
M
O
O
O
O
O
O
68
function:time-less-than
function:datetime-less-than
function:yearMonthDuration-less-than
function:dayTimeDuration-less-than
function:integer-greater-than-or-equal
function:decimal-greater-than-or-equal
function:string-greater-than-or-equal
function:date-greater-than-or-equal
function:time-greater-than-or-equal
function:datetime-greater-than-or-equal
function:yearMonthDuration-greater-than-or-equal
function:dayTimeDuration-greater-than-or-equal
function:integer-less-than-or-equal
function:decimal-less-than-or-equal
function:numeric-less-than-or-equal
function:date-less-than-or-equal
function:time-less-than-or-equal
function:datetime-less-than-or-equal
function:yearMonthDuration-less-than-or-equal
function:dayTimeDuration-less-than-or-equal
function:string-match
function:rfc822Name-match
function:x500Name-match
function:and
function:ordered-and
function:or
function:ordered-or
function:n-of
function:not
function:present
X-intersection
X-union
X-member-of
X-first
X-rest
x-length
2653
Where "X" can be any supported data type.
2654
11. References
O
O
O
O
M
M
M
M
M
M
O
O
O
O
O
O
O
O
O
O
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
2655
2656
2657
[Hinton94]
Hinton, H, M, Lee,, E, S, The Compatibility of Policies, Proceedings 2nd
ACM Conference on Computer and Communications Security, Nov 1994,
Fairfax, Virginia, USA.
2658
2659
[LDAP]
RFC2798, Definition of the inetOrgPerson, M. Smith, April 2000
http://www.ietf.org/rfc/rfc2798.txt
2660
2661
2662
[MathML]
Mathematical Markup Language (MathML), Version 2.0, W3C
Recommendation, 21 February 2001. Available at:
http://www.w3.org/TR/MathML2/
2663
2664
2665
2666
[Perritt93]
Perritt, H. Knowbots, Permissions Headers and Contract Law, Conference
on Technological Strategies for Protecting Intellectual Property in the
Networked Multimedia Environment, April 1993. Available at:
http://www.ifla.org/documents/infopol/copyright/perh2.txt
draft-xacml-specification-16a.doc
69
2667
2668
2669
[RBAC]
Role-Based Access Controls, David Ferraiolo and Richard Kuhn, 15th
National Computer Security Conference, 1992. Available at:
http://csrc.nist.gov/rbac
2670
2671
[RegEx]
XML Schema Part 0: Primer, W3C Recommendation, 2 May 2001,
Appendix D. Available at: http://www.w3.org/TR/xmlschema-0/
2672
2673
[RFC2119]
S. Bradner, Key words for use in RFCs to Indicate Requirement Levels,
http://www.ietf.org/rfc/rfc2119.txt, IETF RFC 2119, March 1997
2674
2675
[SAML]
Security Assertion Markup Language available from http://www.oasisopen.org/committees/security/#documents
2676
2677
2678
[Sloman94]
Sloman, M. Policy Driven Management for Distributed Systems. Journal
of Network and Systems Management, Volume 2, part 4. Plenum Press.
1994.
2679
2680
[XMLSig]
D. Eastlake et al., XML-Signature Syntax and Processing,
http://www.w3.org/TR/xmldsig-core/, World Wide Web Consortium.
2681
2682
[XMLSig-XSD]
XML Signature Schema available from http://www.w3.org/TR/2000/CRxmldsig-core-20001031/xmldsig-core-schema.xsd.
2683
2684
[XPath]
XML Path Language (XPath), Version 1.0, W3C Recommendation 16
November 1999. Available at: http://www.w3.org/TR/xpath
2685
2686
[XSLT]
XSL Transformations (XSLT) Version 1.0, W3C Recommendation 16
November 1999. Available at: http://www.w3.org/TR/xslt
draft-xacml-specification-16a.doc
70
2688
Appendix A. Function names and legal type
combinations
2689
A.1. Functions
2690
2691
The table in this section lists the legal combinations of datatypes for the various functions. For each
function name, the table indicates the valid combination of datatypes and the datatype of the result.
2687
Function name
Return type
First argument
Second argument
Third and Can be used Can be used
subsequent
In
in <Match>
<Condition>
arguments
string-equal
single<xs:boolean> single<xs:string>
single<xs:string>
yes
yes
boolean-equal
single<xs:boolean> single<xs:boolean>
single<xs:boolean
>
yes
yes
integer-equal
single<xs:boolean> single<xs:integer>
single<xs:integer>
yes
yes
decimal-equal
single<xs:boolean> single<xs:decimal>
single<xs:decimal>
yes
yes
date-equal
single<xs:boolean> single<xs:date>
single<xs:date>
yes
yes
time-equal
single<xs:boolean> single<xs_time>
single<xs_time>
yes
yes
datetime-equal
single<xs:boolean> single<xs:dateTime> single<xs:dateTim
e>
yes
yes
anyURI-equal
single<xs:boolean> single<xs:anyURI>
single<xs:anyURI>
yes
yes
Qname-equal
single<xs:boolean> single<xs:Qname>
single<xs:Qname>
yes
yes
single<x500Name
>
yes
yes
rfc822Nameequal
single<xs:boolean> single<rfc822Name> single<rfc822Nam
e>
yes
yes
NOTATIONequal
single<xs:boolean> single<xs:NOTATION single<xs:NOTATI
>
ON>
yes
yes
gregorian-equal
single<xs:boolean> single<xs:gregorian> single<rfc822Nam
e>
yes
yes
x500Name-equal single<xs:boolean> single<x500Name>
hex-binary-equal single<xs:boolean> single<xs:hexbinary>
single<xs:hexbinary>
yes
yes
base64-equal
single<xs:boolean> single<xs:base64>
single<xs:base64>
yes
yes
integer-add
single<xs:integer>
single<xs:integer>
single<xs:int
eger>
no
no
decimal-add
single<xs:decimal> single<xs:decimal>
single<xs:decimal> single<xs:de
cimal>
no
no
integer-subtract
single<xs:integer>
single<xs:integer>
no
no
decimal-subtract single<xs:decimal> single<xs:decimal>
single<xs:decimal>
no
no
integer-multiply
single<xs:integer>
no
no
decimal-multiply single<xs:decimal> single<xs:decimal>
single<xs:decimal>
no
no
integer-divide
single<xs:integer>
no
no
single<xs:integer>
single<xs:integer>
single<xs:integer>
single<xs:integer>
single<xs:integer>
single<xs:integer>
draft-xacml-specification-16a.doc
71
decimal-divide
single<xs:decimal> single<xs:decimal>
single<xs:decimal>
no
no
integer-mod
single<xs:integer>
single<xs:integer>
no
no
decimal-mod
single<xs:decimal> single<xs:decimal>
single<xs:decimal>
no
no
round
ne_sequence<xs:de ne_sequence<xs:dec
cimal>
imal>
no
no
floor
ne_sequence<xs:de ne_sequence<xs:dec
cimal>
imal>
no
no
abs
ne_sequence<xs:de ne_sequence<xs:dec
cimal>
imal>
no
no
decimal-tointeger
ne_sequence<xs:int ne_sequence<xs:dec
eger>
imal>
no
no
integer-todecimal
ne_sequence<xs:de ne_sequence<xs:inte
cimal>
ger>
no
no
ordered-or
single<xs:boolean> single<xs:boolean>
single<xs:boolean
>
single<xs:bo
olean>
no
yes
or
single<xs:boolean> single<xs:boolean>
single<xs:boolean
>
single<xs:bo
olean>
no
yes
ordered-and
single<xs:boolean> single<xs:boolean>
single<xs:boolean
>
single<xs:bo
olean>
no
yes
and
single<xs:boolean> single<xs:boolean>
single<xs:boolean
>
single<xs:bo
olean>
no
yes
not
single<xs:boolean> single<xs:boolean>
single<xs:boolean
>
single<xs:bo
olean>
no
yes
n-of
single<xs:boolean> single<xs:integer>
single<xs:boolean
>
single<xs:bo
olean>
no
yes
integer-greaterthen
single<xs:boolean> single<xs:integer>
single<xs:integer>
no
yes
integer-greaterthen-or-equal
single<xs:boolean> single<xs:integer>
single<xs:integer>
no
yes
time-greaterthen
single<xs:boolean> single<xs:time>
single<xs:time>
no
yes
time-greaterthen-or-equal
single<xs:boolean> single<xs:time>
single<xs:time>
no
yes
date-greaterthen
single<xs:boolean> single<xs:date>
single<xs:date>
no
yes
date-greaterthen-or-equal
single<xs:boolean> single<xs:date>
single<xs:date>
no
yes
datetimegreater-then
single<xs:boolean> single<xs:datetime>
single<xs:datetime
>
no
yes
datetimegreater-then-orequal
single<xs:boolean> single<xs:datetime>
single<xs:datetime
>
no
yes
decimal-greater
single<xs:boolean> single<xs:decimal>
single<xs:decimal>
no
yes
decimal-greater- single<xs:boolean> single<xs:decimal>
then-or-equal
single<xs:decimal>
no
yes
string-greater
single<xs:boolean> single<xs:string>
single<xs:string>
no
yes
string-greater-
single<xs:boolean> single<xs:string>
single<xs:string>
no
yes
single<xs:integer>
draft-xacml-specification-16a.doc
72
then-or-equal
string-match
single<xs:boolean> single<xs:string>
single<xs:string>
yes
yes
x500Namematch
single<xs:boolean> single<x500Name>
single<x500Name
>
yes
yes
rfc822Namematch
single<xs:boolean> single<rfc822Name> single<rfc822Nam
e>
yes
yes
present
single<xs:boolean> single<xs:anyURI>
no
yes
string-intesection set<xs:string>
set<xs:string>
set<xs:string>
no
no
booleanintersection
set<xs:boolean>
set<xs:boolean>
set<xs:boolean>
no
no
integerintersection
set<xs:integer>
set<xs:integer>
set<xs:integer>
no
no
decimalintersection
set<xs:decimal>
set<xs:decimal>
set<xs:decimal>
no
no
date-intersection set<xs:date>
set<xs:date>
set<xs:date>
no
no
time-intersection set<xs_time>
set<xs_time>
set<xs_time>
no
no
dateTimeintersection
set<xs:dateTime>
set<xs:dateTime>
set<xs:dateTime>
no
no
anyURIintersection
set<xs:anyURI>
set<xs:anyURI>
set<xs:anyURI>
no
no
Qnameintersection
set<xs:Qname>
set<xs:Qname>
set<xs:Qname>
no
no
x500Nameintersection
set<x500Name>
set<x500Name>
set<x500Name>
no
no
rfc822Nameintersection
set<rfc822Name>
set<rfc822Name>
set<rfc822Name>
no
no
NOTATIONintersection
set<xs:NOTATION> set<xs:NOTATION>
set<xs:NOTATION
>
no
no
gregorianintersection
set<xs:gregorian>
set<xs:gregorian>
set<rfc822Name>
no
no
hex-binaryintersection
set<xs:hex-binary>
set<xs:hex-binary>
set<xs:hex-binary>
no
no
base64intersection
set<xs:base64>
set<xs:base64>
set<xs:base64>
no
no
date-union
set<xs:date>
set<xs:date>
set<xs:date>
no
no
time-union
set<xs_time>
set<xs_time>
set<xs_time>
no
no
dateTime-union
set<xs:dateTime>
set<xs:dateTime>
set<xs:dateTime>
no
no
anyURI-union
set<xs:anyURI>
set<xs:anyURI>
set<xs:anyURI>
no
no
Qname-union
set<xs:Qname>
set<xs:Qname>
set<xs:Qname>
no
no
x500Name-union set<x500Name>
set<x500Name>
set<x500Name>
no
no
rfc822Nameunion
set<rfc822Name>
set<rfc822Name>
set<rfc822Name>
no
no
NOTATIONunion
set<xs:NOTATION> set<xs:NOTATION>
set<xs:NOTATION
>
yes
yes
gregorian-union
set<xs:gregorian>
set<rfc822Name>
yes
yes
set<xs:gregorian>
draft-xacml-specification-16a.doc
73
hex-binary-union set<xs:hex-binary>
set<xs:hex-binary>
set<xs:hex-binary>
yes
yes
base64-union
set<xs:base64>
set<xs:base64>
yes
yes
date-member-of single<xs:boolean> single<xs:date>
set<xs:date>
yes
yes
time-member-of single<xs:boolean> single<xs_time>
set<xs_time>
yes
yes
set<xs:base64>
dateTimemember-of
single<xs:boolean> single<xs:dateTime> set<xs:dateTime>
yes
yes
anyURImember-of
single<xs:boolean> single<xs:anyURI>
set<xs:anyURI>
yes
yes
Qname-member- single<xs:boolean> single<xs:Qname>
of
set<xs:Qname>
yes
yes
x500Namemember-of
single<xs:boolean> single<x500Name>
set<x500Name>
yes
yes
rfc822Namemember-of
single<xs:boolean> single<rfc822Name> set<rfc822Name>
yes
yes
NOTATIONmember-of
single<xs:boolean> single<xs:NOTATION set<xs:NOTATION
>
>
yes
yes
gregorianmember-of
single<xs:boolean> single<xs:gregorian> set<rfc822Name>
yes
yes
hex-binarymember-of
single<xs:boolean> single<xs:hexbinary>
set<xs:hex-binary>
yes
yes
set<xs:base64>
yes
yes
base64-member- single<xs:boolean> single<xs:base64>
of
date-first
single<xs:date>
ne_sequence<xs:dat
e>
no
no
time-first
single<xs_time>
ne_sequence<xs_tim
e>
no
no
dateTime-first
single<xs:dateTime ne_sequence<xs:dat
>
eTime>
no
no
anyURI-first
single<xs:anyURI>
ne_sequence<xs:any
URI>
no
no
Qname-first
single<xs:Qname>
ne_sequence<xs:Qn
ame>
no
no
x500Name-first
single<x500Name> ne_sequence<x500N
ame>
no
no
rfc822Name-first single<rfc822Name ne_sequence<rfc822
>
Name>
no
no
NOTATION-first single<xs:NOTATIO ne_sequence<xs:NO
N>
TATION>
no
no
gregorian-first
single<xs:gregorian ne_sequence<xs:gre
>
gorian>
no
no
hex-binary-first
single<xs:hexbinary>
ne_sequence<xs:hex
-binary>
no
no
base64-first
single<xs:base64>
ne_sequence<xs:bas
e64>
no
no
date-rest
sequence<xs:date> ne_sequence<xs:dat
e>
no
no
time-rest
sequence<xs_time> ne_sequence<xs_tim
no
no
draft-xacml-specification-16a.doc
74
e>
dateTime-rest
sequence<xs:dateTi ne_sequence<xs:dat
me>
eTime>
no
no
anyURI-rest
sequence<xs:anyU ne_sequence<xs:any
RI>
URI>
no
no
Qname-rest
sequence<xs:Qnam ne_sequence<xs:Qn
e>
ame>
no
no
x500Name-rest
sequence<x500Na
me>
ne_sequence<x500N
ame>
no
no
rfc822Name-rest sequence<rfc822Na ne_sequence<rfc822
me>
Name>
no
no
NOTATION-rest sequence<xs:NOTA single<xs:NOTATION
TION>
>
no
no
gregorian-rest
sequence<xs:gregor single<xs:gregorian>
ian>
no
no
hex-binary-rest
sequence<xs:hexbinary>
no
no
base64-rest
sequence<xs:base6 single<xs:base64>
4>
no
no
date-length
single<xs:integer>
sequence<xs:date>
no
no
time-length
single<xs:integer>
sequence<xs_time>
no
no
dateTime-length single<xs:integer>
sequence<xs:dateTi
me>
no
no
anyURI-length
single<xs:integer>
sequence<xs:anyURI
>
no
no
Qname-length
single<xs:integer>
sequence<xs:Qname
>
no
no
x500Namelength
single<xs:integer>
sequence<x500Nam
e>
no
no
rfc822Namelength
single<xs:integer>
sequence<rfc822Na
me>
no
no
NOTATIONlength
single<xs:integer>
sequence<xs:NOTAT
ION>
no
no
gregorian-length single<xs:integer>
sequence<xs:gregori
an>
no
no
hex-binarylength
single<xs:integer>
sequence<xs:hexbinary>
no
no
base64-length
single<xs:integer>
sequence<xs:base64
>
no
no
single<xs:hexbinary>
2692
draft-xacml-specification-16a.doc
75
2693
Appendix B. XACML identifiers (normative)
2694
2695
This section defines standard identifiers for commonly used entities. All XACML-defined identifiers
have the common base:
2696
urn:oasis:names:tc:xacml:1.0
2697
B.1. XACML namespaces
2698
There are currently two defined XACML namespaces.
2699
Policies are defined using this identifier.
2700
2701
2702
urn:oasis:names:tc:xacml:1.0:policy
Input and output contexts are defined using this identifier.
urn:oasis:names:tc:xacml:1.0:context
2703
B.2. Authentication locality
2704
2705
The following identifiers indicate the location where an authentication credentials were activated.
They are intended to support the corresponding entities from the SAML authentication statement.
2706
This identifier indicates that the location is expressed as an IP address.
2707
2708
2709
urn:oasis:names:tc:xacml:1.0:authn-locality:ip-address
This identifier indicates that the location is expressed as a DNS name.
urn:oasis:names:tc:xacml:1.0:authn-locality:dns-name
2710
B.3. Access subject categories
2711
2712
This identifier indicates the system entity that is directly requesting access, that is the final entity in
a request chain. If subject category is not specified, this is the default value.
2713
2714
2715
2716
2717
2718
2719
2720
2721
2722
2723
2724
urn:oasis:names:tc:xacml:1.0:subjectcategory:access-subject
This identifier indicates the system entity that will receive the results of the request. Used when it is
distinct from the access-subject.
urn:oasis:names:tc:xacml:1.0:subjectcategory:recipient-subject
This identifier indicates a system entity through which the request was passed. There may be more
than one. No means is provided to specify the order in which they passed the message.
urn:oasis:names:tc:xacml:1.0:subjectcategory:intermediary-subject
This identifier indicates a system entity associated with a local or remote codebase that generated
the request. Corresponding subject attributes might include the URLfrom which it was loaded
and/or the identity of the code-signer. There may be more than one. No means is provided to
specify the order they passed the message.
urn:oasis:names:tc:xacml:1.0:subjectcategory:codebase
draft-xacml-specification-16a.doc
76
2725
2726
2727
This identifier indicates a system entity associated with the computer that initiated the request. An
example would be an IPsec identity.
urn:oasis:names:tc:xacml:1.0:subjectcategory:requesting-machine
2728
B.4. XACML functions
2729
This identifier is the base for all the identifiers in the table of functions. See Appendix A.1.
2730
urn:oasis:names:tc:xacml:1.0:function
2731
B.5. Data types
2732
The following identifiers indicate useful datatypes.
2733
B.5.1. X.500 distinguished name
2734
This identifier indicates an X.500 distinguished name.
2735
2736
2737
2738
2739
2740
2741
2742
2743
2744
2745
2746
urn:oasis:names:tc:xacml:1.0:datatype:x500name
B.5.2. RFC822 Name
This identifier indicates an RFC822-style name.
urn:oasis:names:tc:xacml:1.0:datatype:rfc822name
B.5.3. Unix file-system path
This identifier indicates a UNIX file-system path.
urn:oasis:names:tc:xacml:1.0:datatype:ufs-path
B.5.4. Numeric
This identifier indicates a numeric value.
urn:oasis:names:tc:xacml:1.0:datatype:numeric
The following date identifiers are defined by XML Schema.
http://www.w3.org/2001/XMLSchema:yearMonthDuration
2747
2748
http://www.w3.org/2001/XMLSchema:dayTimeDuration
2749
2750
http://www.w3.org/2001/XMLSchema:Gregorian
draft-xacml-specification-16a.doc
77
2751
B.6. Environment attributes
2752
2753
This identifier indicates the current time at the PDP. In practice it is the time the input context was
created.
2754
urn:oasis:names:tc:xacml:1.0:environment:current-time
2755
B.7. Subject attributes
2756
2757
2758
These identifiers indicate attributes of a subject. At most one of each of these attributes is
associated with each subject. Each attribute associated with authentication relates to the same
authentication event.
2759
2760
This identifier indicates the name of the subject. The default format is xs:string. To indicate other
formats, use data type attributes listed in B.5
2761
2762
2763
2764
2765
2766
2767
2768
2769
2770
2771
2772
2773
2774
2775
2776
2777
2778
urn:oasis:names:tc:xacml:1.0:subject:subject-id
This identifier indicates the subject category. Access-subject is the default.
urn:oasis:names:tc:xacml:1.0:subject:subject-category
This identifier indicates the security domain of the subject. Identifies the administrator and policy
that manages the name-space in which the subject id is administered.
urn:oasis:names:tc:xacml:1.0:subject:subject-id-qualifier
This identifier indicates a public key used to confirm the subject’s identity.
urn:oasis:names:tc:xacml:1.0:subject:key-info
This identifier indicates the time at which the subject was authenticated.
urn:oasis:names:tc:xacml:1.0:subject:authentication-time
This identifier indicates the method used to authenticate the subject.
urn:oasis:names:tc:xacml:1.0:subject:authentication-method
This identifier indicates the time at which the subject initiated the access request, according to the
PEP.
urn:oasis:names:tc:xacml:1.0:subject:request-time
This identifier indicates the time at which the subject’s current session began, according to the
PEP.
urn:oasis:names:tc:xacml:1.0:subject:session-start-time
2779
Add the LDAP attributes.
2780
B.8. Resource attributes
2781
This identifier indicates the entire URI of the resource.
2782
2783
2784
urn:oasis:names:tc:xacml:1.0:resource:resource-uri
This identifier indicates the last (rightmost) component of the file name. For example, if the URI is:
“file://home/my/status#pointer”, the simple-file-name is "status".)
draft-xacml-specification-16a.doc
78
2785
2786
2787
urn:oasis:names:tc:xacml:1.0:resource:simple-file-name
This identifier indicates that the resource is specified by an XPath expression.
urn:oasis:names:tc:xacml:1.0:resource:xpath
2788
B.9. Status codes
2789
The following status code identifiers are defined.
2790
This identifier indicates success.
2791
2792
2793
2794
2795
2796
2797
2798
2799
urn:oasis:names:tc:xacml:1.0:status:ok
This identifier indicates that attributes necessary to make a policy decision where not available.
urn:oasis:names:tc:xacml:1.0:status:missing-attribute
This identifier indicates that some attribute value contained a syntax error, such as a letter in a
numeric field.
urn:oasis:names:tc:xacml:1.0:status:syntax-error
This identifier indicates that an error occurred during policy evaluation. An example would be
division by zero.
urn:oasis:names:tc:xacml:1.0:status:processing-error
2800
B.10.
2801
The deny-overrides rule-combining algorithm has the following value for ruleCombiningAlgId:
2802
urn:oasis:names:tc:xacml:1.0:policy-combining-algorithm:deny-overrides
2803
2804
2805
2806
2807
2808
Combining algorithms
The deny-overrides policy-combining algorithm has the following value for policyCombiningAlgId:
urn:oasis:names:tc:xacml:1.0:rule-combining-algorithm:deny-overrides
The permit-overrides rule-combining algorithm has the following value for ruleCombiningAlgId:
urn:oasis:names:tc:xacml:1.0:rule-combining-algorithm:permit-overrides
The permit-overrides policy-combining algorithm has the following value for policyCombiningAlgId:
urn:oasis:names:tc:xacml:1.0:policy-combining-algorithm:permit-overrides
2809
The first-applicable rule-combining algorithm has the following value for ruleCombiningAlgId:
2810
urn:oasis:names:tc:xacml:1.0:rule-combining-algorithm:first-applicable
2811
2812
The first-applicable policy-combining algorithm has the following value for policyCombiningAlgId:
urn:oasis:names:tc:xacml:1.0:policy-combining-algorithm:first-applicable
2814
B.10.
Identifiers used only in XACML
conformance tests
2815
All identifiers used in conformance tests will use this identifier as a base.
2813
draft-xacml-specification-16a.doc
79
2816
urn:oasis:names:tc:xacml:1.0:conformance-test
2817
B.11.
2818
2819
The following subject attributes are defined for the purpose of giving examples. Application
environments are expected to define their own identifiers as needed.
2820
Attributes used in examples
urn:oasis:names:tc:xacml:1.0:example:attribute
2821
2822
urn:oasis:names:tc:xacml:1.0:example:attribute:group
2823
2824
urn:oasis:names:tc:xacml:1.0:example:attribute:role
2825
B.12.
Actions used in examples
2826
This identifier is used as the base for actions used in examples.
2827
urn:oasis:names:tc:xacml:1.0:example:action
2828
2829
urn:oasis:names:tc:xacml:1.0:example:action:xml-ac
draft-xacml-specification-16a.doc
80
2830
Appendix C. Combining algorithms (normative)
2831
2832
This section contains a description of the rule-combining and policy-combining algorithms specified
by XACML.
2833
C.1. Deny-overrides
2834
The following specification defines the "Deny Overrides" rule-combining algorithm of a policy.
2835
2836
2837
2838
2839
2840
In the entire set of rules to be evaluated, if any rule evaluates to "Deny", then the result of
the rule combination shall be "Deny". If any rule evaluates to "Permit" and all other rules
evaluate to "NotApplicable", then the result of the combination shall be "Permit". In other
words, "Deny" takes precedence, regardless of the result of evaluating any of the other
rules in the combination. If all rules are found to be "NotApplicable" to the decision
request, then the rule combination returns "NotApplicable".
2841
2842
2843
If there is any error evaluating the target or condition of a rule that contains an effect of
"Deny" then the evaluation continues looking for a result of "Deny". If no other rule
evaluates to a "Deny", then the result of the combination is "Indeterminate".
2844
2845
2846
If at least one rule evaluates to "Permit", all other rules that do not have evaluation errors
evaluate to "Permit" or "NotApplicable", and all rules that do have evaluation errors contain
effects of "Permit", then the result of the combination shall be "Permit".
2847
2848
2849
2850
2851
2852
2853
2854
2855
2856
2857
2858
2859
2860
2861
2862
2863
2864
2865
2866
2867
2868
2869
2870
2871
2872
2873
2874
2875
2876
The following pseudo-code represents the evaluation strategy of this rule-combining algorithm.
Decision denyOverridesRuleCombiningAlgorithm(Rule rule[])
{
Boolean atLeastOneError = false;
Boolean potentialDeny
= false;
Boolean atLeastOnePermit = false;
for( i=0 ; i < lengthOf(rules) ; i++ )
{
Decision decision = evaluate(rule[i]);
if (decision == Deny)
{
return Deny;
}
if (decision == Permit)
{
atLeastOnePermit = true;
continue;
}
if (decision == NotApplicable)
{
continue;
}
if (decision == Indeterminate)
{
atLeastOneError = true;
if (effect(rule[i]) == Deny)
{
potentialDeny = true;
}
draft-xacml-specification-16.doc
81
2877
2878
2879
2880
2881
2882
2883
2884
2885
2886
2887
2888
2889
2890
2891
2892
2893
2894
2895
continue;
}
}
if (potentialDeny)
{
return Indeterminate;
}
if (atLeastOnePermit)
{
return Permit;
}
if (atLeastOneError)
{
return Indeterminate;
}
return NotApplicable;
}
The following specification defines the "Deny Overrides" policy-combining algorithm of a policy
set.
2896
2897
2898
2899
2900
In the entire set of policies to be evaluated, if any policy evaluates to "Deny", then the
result of the policy combination shall be "Deny". In other words, "Deny" takes precedence,
regardless of the result of evaluating any of the other policies in the combination. If all
policies are found to be "NotApplicable" to the decision request, the policy combination
returns "NotApplicable".
2901
2902
2903
If there is any error evaluating the target of a policy, or a reference to a policy is
considered invalid, or the policy evaluation results in "Indeterminate", then the result of the
combination shall be "Deny".
2904
The following pseudo-code represents the evaluation strategy of this policy-combining algorithm.
2905
2906
2907
2908
2909
2910
2911
2912
2913
2914
2915
2916
2917
2918
2919
2920
2921
2922
2923
2924
2925
2926
2927
2928
2929
2930
2931
2932
2933
Decision denyOverridesPolicyCombiningAlgorithm(Policy policy[])
{
Boolean atLeastOnePermit = false;
for( i=0 ; i < lengthOf(policy) ; i++ )
{
Decision decision = evaluate(policy[i]);
if (decision == Deny)
{
return Deny;
}
if (decision == Permit)
{
atLeastOnePermit = true;
continue;
}
if (decision == NotApplicable)
{
continue;
}
if (decision == Indeterminate)
{
return Deny;
}
}
if (atLeastOnePermit)
{
return Permit;
}
return NotApplicable;
draft-xacml-specification-16a.doc
82
2934
}
2935
Obligations of the individual policies shall be combined as described in Section 4.3.2.3.
2936
C.2. Permit-overrides
2937
The following specification defines the "Permit Overrides" rule-combining algorithm of a policy.
2938
2939
2940
2941
2942
2943
In the entire set of rules to be evaluated, if any rule evaluates to "Permit", then the result of
the rule combination shall be "Permit". If any rule evaluates to "Deny" and all other rules
evaluate to "NotApplicable", then the result of the combination shall be "Deny". In other
words, "Permit" takes precedence, regardless of the result of evaluating any of the other
rules in the combination. If all rules are found to be "NotApplicable" to the decision
request, then the rule combination returns "NotApplicable".
2944
2945
2946
If there is any error evaluating the target or condition of a rule that contains an effect of
"Permit" then the evaluation continues looking for a result of "Permit". If no other rule
evaluates to a "Permit", then the result of the combination is "Indeterminate".
2947
2948
2949
If at least one rule evaluates to "Deny", all other rules that do not have evaluation errors
evaluate to "Deny" or "NotApplicable", and all rules that do have evaluation errors contain
effects of "Deny", then the result of the combination shall be "Deny".
2950
2951
2952
2953
2954
2955
2956
2957
2958
2959
2960
2961
2962
2963
2964
2965
2966
2967
2968
2969
2970
2971
2972
2973
2974
2975
2976
2977
2978
2979
2980
2981
2982
2983
2984
The following pseudo-code represents the evaluation strategy of this rule-combining algorithm.
Decision permitOverridesRuleCombiningAlgorithm(Rule rule[])
{
Boolean atLeastOneError = false;
Boolean potentialPermit = false;
Boolean atLeastOneDeny
= false;
for( i=0 ; i < lengthOf(rule) ; i++ )
{
Decision decision = evaluate(rule[i]);
if (decision == Deny)
{
atLeastOneDeny = true;
continue;
}
if (decision == Permit)
{
return Permit;
}
if (decision == NotApplicable)
{
continue;
}
if (decision == Indeterminate)
{
atLeastOneError = true;
if (effect(rule[i]) == Permit)
{
potentialPermit = true;
}
continue;
}
}
if (potentialPermit)
{
draft-xacml-specification-16a.doc
83
2985
2986
2987
2988
2989
2990
2991
2992
2993
2994
2995
2996
2997
2998
return Indeterminate;
}
if (atLeastOneDeny)
{
return Deny;
}
if (atLeastOneError)
{
return Indeterminate;
}
return NotApplicable;
}
The following specification defines the "Permit Overrides" policy-combining algorithm of a policy
set.
2999
3000
3001
3002
3003
In the entire set of policies to be evaluated, if any policy evaluates to "Permit", then the
result of the policy combination shall be "Permit". In other words, "Permit" takes
precedence, regardless of the result of evaluating any of the other policies in the
combination. If all policies are found to be "NotApplicable" to the decision request, the
policy combination returns "NotApplicable".
3004
3005
3006
3007
If there is any error evaluating the target of a policy, a reference to a policy is considered
invalid, or the policy evaluation results in "Indeterminate", then the result of the
combination shall be "Indeterminate" only if no other policies evaluate to "Permit" or
"Deny".
3008
3009
3010
3011
3012
3013
3014
3015
3016
3017
3018
3019
3020
3021
3022
3023
3024
3025
3026
3027
3028
3029
3030
3031
3032
3033
3034
3035
3036
3037
3038
3039
3040
3041
The following pseudo-code represents the evaluation strategy of this policy-combining algorithm.
Decision permitOverridesPolicyCombiningAlgorithm(Policy policy[])
{
Boolean atLeastOneError = false;
Boolean atLeastOneDeny = false;
for( i=0 ; i < lengthOf(policy) ; i++ )
{
Decision decision = evaluate(policy[i]);
if (decision == Deny)
{
atLeastOneDeny = true;
continue;
}
if (decision == Permit)
{
return Permit;
}
if (decision == NotApplicable)
{
continue;
}
if (decision == Indeterminate)
{
atLeastOneError = true;
continue;
}
}
if (atLeastOneDeny)
{
return Deny;
}
if (atLeastOneError)
{
return Indeterminate;
draft-xacml-specification-16a.doc
84
3042
3043
3044
}
return NotApplicable;
}
3045
Obligations of the individual policies shall be combined as described in Section 4.3.2.3.
3046
C.3. First-applicable
3047
The following specification defines the "First-Applicable " rule-combining algorithm of a policy.
3048
3049
3050
3051
3052
3053
3054
Each rule is evaluated in the order it is listed in the policy. Of a particular rule, if the
target matches and the condition evaluates to "True", the evaluation of the combination
shall halt and the corresponding effect of the rule shall be the result of the evaluation of
the combination (i.e. "Permit" or "Deny"). Of a particular rule selected in the evaluation, if
the target does not matchor the condition evaluates to "False", then the next rule in the
order is evaluated. If no further rule in the order exists, then "NotApplicable" shall be the
result of the evaluation of the combination.
3055
3056
If there is any error evaluating the target or condition of a rule then the evaluation shall
halt, and the result shall be "Indeterminate" with the appropriate error status.
3057
The following pseudo-code represents the evaluation strategy of this rule-combining algorithm.
3058
3059
3060
3061
3062
3063
3064
3065
3066
3067
3068
3069
3070
3071
3072
3073
3074
3075
3076
3077
3078
3079
3080
3081
3082
3083
3084
3085
3086
3087
3088
3089
3090
Decision firstApplicableEffectRuleCombiningAlgorithm(Rule rule[])
{
for( i = 0 ; i < lengthOf(rule) ; i++ )
{
Decision decision = evaluate(rule[i]);
if (decision == Deny)
{
return Deny;
}
if (decision == Permit)
{
return Permit;
}
if (decision == NotApplicable)
{
continue;
}
if (decision == Indeterminate)
{
return Indeterminate;
}
}
return NotApplicable;
}
The following specification defines the "First-Appplicable" policy-combining algorithm of a policy
set.
Each policy is evaluated in the order that it appears in the policy set. Of a particular
policy, if the target matches and the policy evaluates to a determinate decision of
"Permit" or "Deny", the evaluation shall halt and that effect shall be the result of the
evaluation of the combination. Of a particular policy, if the target does not matchor the
policy evaluates to "NotApplicable", then the next policy in the order is evaluated. If no
further policy exists in the order, then "NotApplicable" shall be the result of the evaluation
of the combination.
draft-xacml-specification-16a.doc
85
3091
3092
3093
If there is any error evaluating the target or the policy, or a reference to a policy is
considered invalid, then the evaluation shall continue looking for an applicable policy, if no
applicable policy is found, then the result of the combination is "Indeterminate".
3094
3095
The following pseudo-code represents the evaluation strategy of this policy-combination
algorithm.
3096
3097
3098
3099
3100
3101
3102
3103
3104
3105
3106
3107
3108
3109
3110
3111
3112
3113
3114
3115
3116
3117
3118
3119
3120
3121
3122
3123
3124
3125
3126
Decision firstApplicableEffectPolicyCombiningAlgorithm(Policy
policy[])
{
Boolean atLeastOneError = false;
for( i = 0 ; i < lengthOf(policy) ; i++ )
{
Decision decision = evaluate(policy[i]);
if(decision == Deny)
{
return Deny;
}
if(decision == Permit)
{
return Permit;
}
if (decision == NotApplicable)
{
continue;
}
if (decision == Indeterminate)
{
atLeastOneError = true;
continue;
}
}
if (atLeastOneError)
{
return Indeterminate;
}
return NotApplicable;
}
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Obligations of the individual policies shall be combined as described in Section 4.3.2.3
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Appendix D. Acknowledgments
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The following individuals were voting members of the XACML committee at the time that this
version of the specification was issued:
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3141
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Affinitex James MacLean JMaclean@affinitex.com
Crosslogix Ken Yagen kyagen@crosslogix.com
Crosslogix Daniel Engovatov dengovatov@crosslogix.com
Entegrity Hal Lockhart hal.lockhart@entegrity.com
Entrust Carlisle Adams carlisle.adams@entrust.com
Entrust Tim Moses tim.moses@entrust.com
Hitachi Don Flinn Don.Flinn@hitachisoftware.com
Hitachi Konstantin Beznosov konstantin.beznosov@quadrasis.com
Overxeer Bill Parducci bill.parducci@overxeer.com
Overxeer Simon Godik simon.godik@overxeer.com
IBM Michiharu Kudoh kudo@jp.ibm.com
Self Polar Humenn polar@syr.edu
Sterling Commerce Suresh Damodaran Suresh_Damodaran@stercomm.com
University of Milan Pierangela Samarati samarati@pinky.crema.unimi.it
University of Milan Ernesto Damiani edamiani@crema.unimi.it
Sun Microsystems Sekhar Vajjhala sekhar.vajjhala@sun.com
Sun Microsystems Anne Anderson Anne.Anderson@Sun.com
Xtradyne Gerald Brose Gerald.Brose@xtradyne.com
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Appendix E. Revision history
Rev
Date
By whom
What
V14
14 June 2002
Tim Moses
Added the XACML context schema.
Added the Security and Privacy
section.
V15
18 July 2002
Tim Moses
Changed the representation of
<Function>
V16
16 Aug 2002
Tim Moses
Updated policy schema, identifiers,
combining algorithms. Deleted
LDAP profile.
V16a
10 Sep 2002
Tim Moses
Updated Figure 3, updated "Security
and privacy" section and created
"Functional requirements" section.
3150
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Appendix F. Notices
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OASIS takes no position regarding the validity or scope of any intellectual property or other rights
that might be claimed to pertain to the implementation or use of the technology described in this
document or the extent to which any license under such rights might or might not be available;
neither does it represent that it has made any effort to identify any such rights. Information on
OASIS's procedures with respect to rights in OASIS specifications can be found at the OASIS
website. Copies of claims of rights made available for publication and any assurances of licenses to
be made available, or the result of an attempt made to obtain a general license or permission for
the use of such proprietary rights by implementors or users of this specification, can be obtained
from the OASIS Executive Director.
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OASIS has been notified of intellectual property rights claimed in regard to some or all of the
contents of this specification. For more information consult the online list of claimed rights.
3163
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OASIS invites any interested party to bring to its attention any copyrights, patents or patent
applications, or other proprietary rights which may cover technology that may be required to
implement this specification. Please address the information to the OASIS Executive Director.
3166
Copyright (C) OASIS Open 2002. All Rights Reserved.
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This document and translations of it may be copied and furnished to others, and derivative works
that comment on or otherwise explain it or assist in its implementation may be prepared, copied,
published and distributed, in whole or in part, without restriction of any kind, provided that the above
copyright notice and this paragraph are included on all such copies and derivative works. However,
this document itself may not be modified in any way, such as by removing the copyright notice or
references to OASIS, except as needed for the purpose of developing OASIS specifications, in
which case the procedures for copyrights defined in the OASIS Intellectual Property Rights
document must be followed, or as required to translate it into languages other than English.
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The limited permissions granted above are perpetual and will not be revoked by OASIS or its
successors or assigns.
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This document and the information contained herein is provided on an “AS IS” basis and OASIS
DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO
ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY
RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A
PARTICULAR PURPOSE.
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