CryptSan: Leveraging ARM Pointer Authentication for Memory Safety in C/C++

Abstract

Memory safety bugs remain in the top ranks of security vulnerabilities, even after decades of research on their detection and prevention. Various mitigations have been proposed for C/C++, ranging from language dialects to instrumentation. Among these, compiler-based instrumentation is particularly promising, not requiring manual code modifications and being able to achieve precise memory safety. Unfortunately, existing compiler-based solutions compromise in many areas, including performance but also usability and memory safety guarantees. New developments in hardware can help improve performance and security of compiler-based memory safety. ARM Pointer Authentication, added in the ARMv8.3 architecture, is intended to enable hardware-assisted Control Flow Integrity (CFI). But since its operations are generic, it also enables other, more comprehensive hardware-supported runtime integrity approaches. As such, we propose CryptSan, a memory safety approach based on ARM Pointer Authentication. CryptSan uses pointer signatures to retrofit memory safety to C/C++ programs, protecting heap, stack, and globals against temporal and spatial vulnerabilities. We present a full LLVM-based prototype implementation, running on an M1 MacBook Pro, i.e., on actual ARMv8.3 hardware. Our prototype evaluation shows that the system outperforms similar approaches under real-world conditions. This, together with its interoperability with uninstrumented libraries and cryptographic protection against attacks on metadata, makes CryptSan a viable solution for retrofitting memory safety to C/C++ programs.