JITGuard: Hardening Just-in-time Compilers with SGX

Memory-corruption vulnerabilities pose a serious threat to modern computer security. Attackers exploit these vulnerabilities to manipulate code and data of vulnerable applications to generate malicious behavior by means of code-injection and code-reuse attacks. Researchers already demonstrated the power of data-only attacks by disclosing secret data such as cryptographic keys in the past. A large body of literature has investigated defenses against code-injection, code-reuse, and data-only attacks. Unfortunately, most of these defenses are tailored towards statically generated code and their adaption to dynamic code comes with the price of security or performance penalties. However, many common applications, like browsers and document viewers, embed just-in-time compilers to generate dynamic code. The contribution of this paper is twofold: first, we propose a generic data-only attack against JIT compilers, dubbed DOJITA. In contrast to previous data-only attacks that aimed at disclosing secret data, DOJITA enables arbitrary code-execution. Second, we propose JITGuard, a novel defense to mitigate code-injection, code-reuse, and data-only attacks against just-in-time compilers (including DOJITA). JITGuard utilizes Intel's Software Guard Extensions (SGX) to provide a secure environment for emitting the dynamic code to a secret region, which is only known to the JIT compiler, and hence, inaccessible to the attacker. Our proposal is the first solution leveraging SGX to protect the security critical JIT compiler operations, and tackles a number of difficult challenges. As proof of concept we implemented JITGuard for Firefox's JIT compiler SpiderMonkey. Our evaluation shows reasonable overhead of 9.8% for common benchmarks.