vfGuard: Strict Protection for Virtual Function Calls in COTS C++ Binaries Aravind Prakash Xunchao Hu Heng Yin Department of EECS Department of EECS Department of EECS Syracuse University Syracuse University Syracuse University
[email protected] [email protected] [email protected] Abstract—Control-Flow Integrity (CFI) is an important se- these binary-only solutions are unfortunately coarse-grained curity property that needs to be enforced to prevent control- and permissive. flow hijacking attacks. Recent attacks have demonstrated that existing CFI protections for COTS binaries are too permissive, While coarse-grained CFI solutions have significantly re- and vulnerable to sophisticated code reusing attacks. Accounting duced the attack surface, recent efforts by Goktas¸¨ et al. [9] for control flow restrictions imposed at higher levels of semantics and Carlini [10] have demonstrated that coarse-grained CFI is key to increasing CFI precision. In this paper, we aim to provide solutions are too permissive, and can be bypassed by reusing more stringent protection for virtual function calls in COTS large gadgets whose starting addresses are allowed by these C++ binaries by recovering C++ level semantics. To achieve this solutions. The primary reason for such permissiveness is the goal, we recover C++ semantics, including VTables and virtual lack of higher level program semantics that introduce certain callsites. With the extracted C++ semantics, we construct a sound mandates on the control flow. For example, given a class CFI policy and further improve the policy precision by devising two filters, namely “Nested Call Filter” and “Calling Convention inheritance, target of a virtual function dispatch in C++ must Filter”.