eXtensible Access Control Markup Language OASIS Standard

1
eXtensible Access Control Markup LanguageOASIS
Standard

• Kailash Bhoopalam
• Java and XML

2
Contents

• Introduction to Access Control
• Introduction to XACML
• The XACML schema.
• Access Control Examples and Experiments with
  XACML.
• The XACML framework.
• Installing and using the XACML package.
• Beyond Vanilla XACML
• User Extensions to XACML Implementation
• XACML in Secure Distributed Digital Libraries

3
Introduction to Access Control
John wants access to protected file
PatientRecord1.doc
File Server
Authentication
Authorization (Access Control)
PatientRecord1.doc PatientRecord2.doc
4
Access Control, contd.
5
Introduction to XACML
John wants access to protected file
PatientRecord1.doc
XACML Policy
Request Context
Response Context
ltrule effectpermitgt lttargetgt
ltsubjectgt ltvaluegtJohnlt/valuegt
lt/subjectgt ltresourcegt
ltvaluegtPatientRecord1.doclt/valuegt
lt/resourcegt ltactiongt
ltvaluegtRlt/valuegt
lt/actiongt lt/targetgt lt/rulegt
ltresponsegt ltdecisiongt
ltvaluegtPermitlt/valuegt lt/decisiongt lt/responsegt
ltrequestgt ltsubjectgt
ltvaluegtJohnlt/valuegt lt/subjectgt
ltresourcegt
ltvaluegtPatientRecord1.doclt/valuegt
lt/resourcegt ltactiongt
ltvaluegtRlt/valuegt
lt/actiongt lt/requestgt
6
Introduction to XACML contd.
How does XACML Work?
7
XACML Schemas
Policy Schema
Request Schema
Response Schema
Response Decision Obligation
PolicySet (Combining Alg) Policy (Combining
Alg) Rule (Effect) Subject
Resource Action
Condition Obgligation
Request Subject Resource
Action
8
Some Experiments

• Ex1
• Ex2
• Ex3

9
XACML Framework (Data flow model)
10
XACML Framework (Policy Language Model)
11
Installing and using the XACML Implementation

• Available Implementations
• Sun Microsystems (here) (download)
• You may also optionally copy from
  kbhoopal/public_html/xacml/sunxacml.jar
• Jiffy Software (here)
• More on Suns XACML implementation
• Available as zip file.
• unzip and build with ant (download ant)
• include the sunxacml.jar in the class path.

12
Using the XACML Implementation(A Programmers
Guide)

• Using Suns XACML Implementation
• Overview of APIs
• Building a basic PDP
• Building the basic PEP
• Validating Policies and Requests
• Some Experiments

13
Beyond Vanilla Access Control

• Policy Rule Combining algorithms
• Permit Overrides
• If a single rule permits a request,
  irrespective of the other rules, the result of
  the PDP is Permit
• Deny Overrides
• If a single rule denies a request,
  irrespective of the other rules, the result of
  the PDP is deny.
• First Applicable
• The first applicable rule that satisfies the
  request is the result of the PDP
• Only-one-applicable
• If there are two rules with different effects
  for the same request, the result is indeterminate

14
Beyond Vanilla, contd.

• Conditions
• Declarative use of boolean expressions
• Using Environment variables like time, etc.
• E.g., John can access patientrecord1.doc only
  between 9am and 4pm.
• Obligations
• An operation performed in a policy or policy set
  that should be performed in conjunction with the
  enforcement of an authorization decision.

15
Beyond Vanilla, contd.

• XACML Functions
• Equality Predicates
• Arithmetic Arithmetic comparison
• String Conversion
• Numeric Data Type Conversion
• Logical
• Date and Time
• Set
• And Many more.

16
User Extensions to XACML Implementation

• Extend
• Attributes
• Functions
• Combining algorithms
• Finder modules.

17
XACML in SDDL

• Implementation PAP, PIP using a Policy Editor
  (here)
• Implementation of SunXACMLs PDP with a custom
  PEP and integration with Shibboleth and Archon.
  (here)

18
References

• XACML Specification
• Suns XACML Implementation