Similarity testing for access control

Context: Access control is among the most important security mechanisms, and XACML is the de facto standard for specifying, storing and deploying access control policies. Since it is critical that enforced policies are correct, policy testing must be performed in an effective way to identify potential security flaws and bugs. In practice, exhaustive testing is impossible due to budget constraints. Therefore the tests need to be prioritized so that resources are focused on their most relevant subset. Objective: This paper tackles the issue of access control test prioritization. It proposes a new approach for access control test prioritization that relies on similarity. Method: The approach has been applied to several policies and the results have been compared to random prioritization (as a baseline). To assess the different prioritization criteria, we use mutation analysis and compute the mutation scores reached by each criterion. This helps assessing the rate of fault detection. Results: The empirical results indicate that our proposed approach is effective and its rate of fault detection is higher than that of random prioritization. Conclusion: We conclude that prioritization of access control test cases can be usefully based on similarity criteria.