Modeling Dynamic Role- based Access Constraints using UML Khaled Alghathbar George Mason University, USA and King Saud University, Riyadh, Saudi Arabia Duminda Wijesekera Center for Secure Information Systems George Mason University, USA

© Khaled Alghathbar 2 How to achieve a good security? Security requirements of a software product need to receive attention throughout its development life cycle.

© Khaled Alghathbar 3 Why? Because the security requirements specified at early stages of the life cycle affect later stages and are likely to feature in the eventual product. Defects, if undetected, can propagate downstream*. Reduce cost + prevent faults * P. T. Devanbu and S. Stubblebine. Software engineering for security: A roadmap. In A. Finkelstein, editor, The Future of Software Engineering. ACM Press, 2000.

© Khaled Alghathbar 4 However! “Non functional requirements are generally more difficult to express in a measurable way, making them more difficult to analyze. In particular, NFRs tends to be properties of system as a whole.”*. lack of tools that model security software engineers lack security expertise * B. Nuseibeh and S. Easterbrook. Requirements engineering: A roadmap. In A. Finkelstein, editor, The Future of Software Engineering. ACM Press, 2000

© Khaled Alghathbar 5 Objective There is a need for unified representations of security features.

© Khaled Alghathbar 6 How to represent security UML extension Advantages: –Unified design of systems and security policies. –Modularity, and Reuse in policy representation. –Leverage of existing standards-based tools for design and analysis.

© Khaled Alghathbar 7 Security Policies Software Development Life cycle Modeling Security Policies Using UML UML Our Goal

© Khaled Alghathbar 8 Security Policies Software Development Life cycle Access control policies Design Phase Our Focus

© Khaled Alghathbar 9 Access control policies Discretionary Access Control (DAC). Mandatory Access Control (MAC). Role-based Access control (RBAC). Static policies: –Manager  Sign check. Dynamic policies: –Supervisor shall not write and sign the same check.

© Khaled Alghathbar 10 Our Proposal Modeling Dynamic Role-based Access Constraints using UML.

© Khaled Alghathbar 11 Related Work (1) 1. Lodderstedt et al.* propose a methodology to model access control policies and integrate them into a model- driven software development process. It is the most related work, but our metamodel allows the specification of more authorization policies. 2. Brose et al. ** extend UML to support the automatic generation of access control policies in order to configure a CORBA-based infrastructure However, It does not model dynamic access control policies. *T. Lodderstedt, D. Basin, J. Doser. “SecureUML: A UML-Based Modeling Language for Model-Driven Security”. In the proceedings of the 5th International Conference on the Unified Modeling Language, Dresden, Germany. ** G. Brose, M. Koch, K.-P. Löhr. “Integrating Access Control Design into the Software Development Process”. In the Proc. of the sixth biennial world conference on the Integrated Design and Process Technology (IDPT), Pasadena, CA. June 2002.

© Khaled Alghathbar 12 Related Work (2) 3. Fernandez-Medina et al.* propose an extension to the Use Case and Class models of UML. Also, they introduce a language Object Security constraint Language (OSCL). 4. Jurjens’s ** extends UML to integrate standard concepts from formal methods regarding multi-level secure system and security protocols. However, 3 and 4 focus on database and multilevel security. * E. Fernadez-Medina, M.G. Piattini, M.A Serrano. “Specification of Security Constraints in UML”. In the 35th International Carnahan Conference on Security Technology (ICCST), London, UK, October * E. Fernandez-Medina, A. Martinez, C. Medina, And M. Piattini. “Integrating Multilevel Security in the Database Design Process”. In the Proc. of the sixth biennial world conference on the Integrated Design and Process Technology (IDPT), Pasadena, CA. June ** J. Jurjens. “Towards development of secure systems using UMLsec”. In the Proceedings of Fundamental Approaches to Software Engineering, 4th Internacional Conference, LNCS, pages Springer, 2001.

© Khaled Alghathbar 13 Advantages over other works: Enforcing dynamic access control and flow control policies. Constraints are written on object constraints language (OCL).

© Khaled Alghathbar 14 Example

© Khaled Alghathbar 15 Examples of access and flow control policies Required Sequence of operations. Role Restriction. Dynamic Separation of Duty. Avoiding Conflicts.

© Khaled Alghathbar 16 The proposed extension Security Policy Constraints (SPC). History Log. Business Task. Conflict Sets.

© Khaled Alghathbar 17 Security Policy Constraints (SPC) The Core of UML

© Khaled Alghathbar 18 Security Policy Constraints (SPC) Example of SPC constraint

© Khaled Alghathbar 19 History Log History Log: It keeps in record all authorization requests.

© Khaled Alghathbar 20 Business Task A reference of related operations. An essentials element to enforce Separation of Duty and workflow policies. Example: BT={Record, verify, authorize}

© Khaled Alghathbar 21 Conflict Sets A reference of conflicting: Users. Roles. Operations. It is essential to avoid conflict. An example conflicting roles: {Purchasing Manager, Account Payable Manager } An example conflicting operations: {writing checks, signing checks}

© Khaled Alghathbar 22 The interactions between elements

© Khaled Alghathbar 23 An Example of a Constraint in the SPC Required sequence of operations (Workflow policies)

© Khaled Alghathbar 24 OCL Representation of the Required Sequence of Operations constraints Context Invoice::Authorize_Payment():Void Pre: Historty_Log-> select(Action=(Business_Task  select(Task="Purchasing”).Operation  Prior (Operation=CurrentOperation)) AND Object=CurrentObject)  notEmpty

© Khaled Alghathbar 25 RBAC Metamodel RBAC Policies: Dynamic separation of duty (DSOD) Static separation of duty (SSOD) Flow control and workflow: Conflicts of User, Role and Operation: Cardinality in Roles and User elements.

© Khaled Alghathbar 26 Conclusion We proposed a Metamodel that allow designers to: –Model access control policies (static and dynamic) –Model flow control policies. Future Work Integrating security policies on other phases of the software lifecycle. Providing a unified representations of security policies.

© Khaled Alghathbar 27 Questions Thank you