Towards Effective Verification of Multi-Model Access Control Properties

Many existing software systems like logistics systems or enterprise applications employ data security in a more or less ad hoc fashion. Our approach focuses on access control such as permission-based discretionary access control (DAC), variants of role-based access control (RBAC) with delegation, and attribute-based access control (ABAC). Typically, software systems implement hybrid access control making an effective security analysis and assessment rather difficult. We propose an analysis methodology to reconstruct access control using a novel modular access control model. Our modular approach allows us to flexibly model exactly those access properties that are relevant for a given system. As formalism we use the Object Constraint Language (OCL) with Ecore from the Eclipse Modeling Framework (EMF). We demonstrate the suitability of our access control model for three software systems: a port community system (PCS), a clinical information system (CIS), and an identity management system (IdMS). For the PCS and CIS we model concrete roles and policies. For the IdMS we evaluate our analysis methodology in-depth by reconstructing access control policies from byte code using the Soot analysis framework as well as model transformation techniques (QVTo). The resulting model helped us to identify design deficiencies. Violated OCL invariants such as for mutually exclusive roles or cardinality constraints revealed non-trivial security vulnerabilities.