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Testing Implementations Of Access Control Systems (New Proposal)

Testing Implementations Of Access Control Systems (New Proposal). Ammar Masood: Graduate Student Arif Ghafoor (ECE) and Aditya Mathur (CS) Purdue University, West Lafayette SERC Showcase, June 7-8, 2006 Motorola Labs, Schaumburg, IL. Research Objectives.

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Testing Implementations Of Access Control Systems (New Proposal)

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  1. Testing Implementations Of Access Control Systems(New Proposal) Ammar Masood: Graduate Student Arif Ghafoor (ECE) and Aditya Mathur (CS) Purdue University, West Lafayette SERC Showcase, June 7-8, 2006 Motorola Labs, Schaumburg, IL 1

  2. Research Objectives • To develop, experiment with and study the effectiveness of techniques for the generation of tests to validate conformance of implementations of access control policies (in particular Role Based Access Control [RBAC] with or without temporal constraints) 2

  3. Related Work • R. Chandramouli. M. Blackburn. Automated Testing of Security Functions using a combined Model & Interface driven Approach. Proc. 37th Hawaii International Conference on System Sciences, pp. 299-308, 2004 • J. Springintveld, F. Vaandrager and P.R. D'Argenio. Testing timed automata. Theoretical Computer Science, 254(1-2), pp. 225-257, 2001 • A. En-Nouaary, R. Dssouli and F. Khendek. Timed Wp method: testing real time systems. IEEE Transactions on Software Engineering, 28(11), pp. 1023 – 1038, 2002. • K.G. Larsen, M. Mikucionis and B. Nielsen. Online Testing of Real-time Systems Using UPPAAL. Formal Approaches to Testing of Software. Linz, Austria. September 21, 2004 3

  4. Access Control policy Policy tests Test harness Policy verifier plugin Test generator plugin IUT Policy (internal representation) Modeling plugin Policy model Proposed Test Infrastructure 4

  5. Challenges • Modeling: • Naïve FSM or timed automata models are prohibitively large even for policies with 10 users and 5 roles (and 3 clocks). • How to reduce model size and the tests generated? • Test generation: • How to generate tests to detect (ideally) all policy violation faults that might lead to violation of the policy? • Test execution: • Distributed policy enforcement? 5

  6. Proposed Approach • Express behavior implied by a policy as an FSM. • Apply heuristics to scale down the model. • Use the W- method, or its variant, to generate tests from the scaled down model. • Generate additional tests using a combination of stress and random testing aimed at faults that might go undetected due to scaling. 6

  7. 0000 DS11 DS21 AS21 AS11 DS21 DS11 1000 0010 DS11 AS21 AC21 AS11 DS21 AC11 DC11 DS21 DC21 DS11 1100 1010 0011 DS21 DS11 AC21 DC21 AC11 DC11 AS21 AS11 1110 1011 Sample Model Two users, one role. Only one user can activate the role. Number of states≤32. AS: assign. DS: De-assign. AC: activate. DC: deactivate. Xij: do X for user i role j. 7

  8. Heuristics H1: Separate assignment and activation H2: Use FSM for activation and single test sequence for assignment H3: Use single test sequence for assignment and activation H4: Use a separate FSM for each user H5: Use a separate FSM for each role H6: Create user groups for FSM modeling. 8

  9. 00 00 AS11 AC11 AC21 DS11 DS21 DC11 DC21 DS21 DS11 AC21 AC11 10 10 AS21 01 01 11 AC21 00 AC11 00 AS21 AS11 DS21 DS21 DS11 DS11 AC21 AC11 10 11 10 11 DC21 DC11 Reduced Models Assignment Machine Activation Machine Heuristic 1 User u1 Machine User u2 Machine Heuristic 4 9

  10. Tests Generated 10

  11. Fault Model 11

  12. Claim The proposed method for generating the complete behavior model and tests guarantees a test set that detects all faults in the IUT that correspond to the proposed fault model when the number of states in the IUT is correctly estimated. 12

  13. Future Research • Modeling: • Handling timing constraints? (timed automata, fault model, heuristics) • Experimentation: • With large/realistic policies to assess the efficiency and effectiveness of the test generation methods. • Prototype tool development 13

  14. Schedule • Month 1: Extend the un-timed Fault Model for temporal RBAC • Months 2-4: Study applicability/extensions in existing timed automata test generation techniquesfor complete fault coverage with respect to the timed fault model • Months: 5-8: Develop techniques to reduce the cost of testing (Number of test cases) • Months 9-11: Perform a case study to verify the efficacy of the finally proposed approach. • Month 12: Final report. 14

  15. Deliverables • A methodology for testing access control implementations that employ temporal constraints. • Evaluation of the methodology through a case study. • A set of recommendations on the implementation of the methodology as an integral part of the software development lifecycle. 15

  16. Budget- Year 1 • Salaries (faculty + graduate student): $30,000 • Travel: $8,000 • Miscellaneous: $2000 • Indirect costs: $10,000 • Total: $50,000 16

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  18. Access Control Policy Specifications Specificationverification Step 1 Consistent Specifications Policy Implementation Step 2 Access Control System Implementation Security Testing Step 3 Security Verified Implementation Sequential Steps to a Verified Implementation 18

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