Enhancing and Extending Software Diversity

Software immunity through diversity is a promising research direction. Address Space Layout Randomization has been widely deployed to defend against code-reuse attacks and significantly raises the bar for attackers. However, automated software diversity is still exploitable by adroit and adaptable adversaries. Using powerful memory disclosure attacks, offensive researchers have demonstrated weaknesses in conventional randomization techniques. In addition, current defenses are largely passive and allow attackers to continuously brute-force randomized defenses with little impediment. Building on the foundation of automated software diversity, we propose novel techniques to strengthen the security and broaden the impact of code randomization. We first discuss software booby traps, a new active defense technique enabled by randomized program contents. We then propose, implement, and evaluate a comprehensive randomization-based system, Readactor++, which is resilient to all types of memory disclosure attacks. Readactor++ enforces execute-only memory protections on commodity x86 processors, thus preventing direct disclosure of randomized code. We also identify the indirect disclosure attack, a new class of code leakage via data disclosure, and mitigate this attack as well. By integrating booby traps into our system, we protect against brute-force memory disclosure attempts. In our evaluation we find that Readactor++ compares favorably to other memory-disclosure resilient code-reuse defenses and that it scales effectively to complex, real-world software. Finally, we propose a novel extension of code randomization to mitigate side-channel rather than code-reuse attacks. Using control-flow diversity, a novel control-flow transformation, we introduce dynamic behavior into program side effects with fast, static code. As an example, we apply this technique to mitigate an AES cache side-channel attack. With our techniques, software diversity can now be efficiently secured against advanced attacks, including memory disclosure and function table reuse, and is adaptable to combat new classes of threats, such as side-channel attacks