Whole-Program Privilege and Compartmentalization Analysis with the Object-Encapsulation Model

Abstract

We present the object-encapsulation model, a low-level program representation and analysis framework that exposes and quantifies privilege within a program. Successfully compartmentalizing an application today requires significant expertise, but is an attractive goal as it reduces connectability of attack vectors in exploit chains. The object-encapsulation model enables understanding how a program can best be compartmentalized without requiring deep knowledge of program internals. We translate a program to a new representation, the Program Capability Graph (PCG), mapping each operation to the code and data objects it may access. We aggregate PCG elements into encapsulated-object groups. The resulting encapsulated-objects PCG enables measuring program interconnectedness and encapsulated-object privileges in order to explore and compare compartmentalization strategies. Our deep dive of parsers reveals they are well encapsulated, requiring access to an average of 545/4902 callable interfaces and 1201/29198 external objects. This means the parsers we evaluate can be easily compartmentalized, applying the encapsulated-objects PCG and our analysis to facilitate automatic or manual trust boundary placement. Overall, the object-encapsulation model provides an essential element to language-level analysis of least-privilege in complex systems to aid codebase understanding and refactoring.