Supporting User Authorization Queries in RBAC Systems by Role-Permission Reassignment.

The User Authorization Query (UAQ) Problem is a key issue related to efficiently handling users’ access requests in RBAC systems. In practice, there may not exist any solution for the UAQ problem, as missing any requested permissions may make the failure of this task, while any extra permissions may bring the intolerable risk to the system. Hence, making a desirable update of the RBAC system state to support the UAQ problem is desirable. However, this task is generally complex and challenging as usually the resulting state is expected to meet various necessary objectives and constraints. In this paper, we study a fundamental problem of how generate a valid role-permission assignment to satisfy all objectives and constraints, such as reassignment objectives, prerequisite constraints and permission-capacity constraints. The computational complexity result shows that it is intractable (NP-complete) in general. We also propose an approach to reduce it to SAT that benefit from SAT solvers to reduce the running time. Experiment results show that the proposed approach scales well in large RBAC systems.