Shining Light On Shadow Stacks

Control-Flow Hijacking attacks are the dominant attack vector against C/C++ programs. Control-Flow Integrity (CFI) solutions mitigate these attacks on the forward edge,i.e., indirect calls through function pointers and virtual calls. Protecting the backward edge is left to stack canaries, which are easily bypassed through information leaks. Shadow Stacks are a fully precise mechanism for protecting backwards edges, and should be deployed with CFI mitigations. We present a comprehensive analysis of all possible shadow stack mechanisms along three axes: performance, compatibility, and security. For performance comparisons we use SPEC CPU2006, while security and compatibility are qualitatively analyzed. Based on our study, we renew calls for a shadow stack design that leverages a dedicated register, resulting in low performance overhead, and minimal memory overhead, but sacrifices compatibility. We present case studies of our implementation of such a design, Shadesmar, on Phoronix and Apache to demonstrate the feasibility of dedicating a general purpose register to a security monitor on modern architectures, and the deployability of Shadesmar. Our comprehensive analysis, including detailed case studies for our novel design, allows compiler designers and practitioners to select the correct shadow stack design for different usage scenarios.Comment: To Appear in IEEE Security and Privacy 201

ProbeGuard:Mitigating Probing Attacks Through Reactive Program Transformations

Many modern defenses against code reuse rely on hiding sensitive data such as shadow stacks in a huge memory address space. While much more efficient than traditional integritybased defenses, these solutions are vulnerable to probing attacks which quickly locate the hidden data and compromise security. This has led researchers to question the value of information hiding in real-world software security. Instead, we argue that such a limitation is not fundamental and that information hiding and integrity-based defenses are two extremes of a continuous spectrum of solutions. We propose a solution, ProbeGuard, that automatically balances performance and security by deploying an existing information hiding based baseline defense and then incrementally moving to more powerful integrity-based defenses by hotpatching when probing attacks occur. ProbeGuard is efficient, provides strong security, and gracefully trades off performance upon encountering more probing primitives

Position-Independent Code Reuse:On the Effectiveness of ASLR in the Absence of Information Disclosure

Address-space layout randomization is a wellestablished defense against code-reuse attacks. However, it can be completely bypassed by just-in-time code-reuse attacks that rely on information disclosure of code addresses via memory or side-channel exposure. To address this fundamental weakness, much recent research has focused on detecting and mitigating information disclosure. The assumption being that if we perfect such techniques, we will not only maintain layout secrecy but also stop code reuse. In this paper, we demonstrate that an advanced attacker can mount practical code-reuse attacks even in the complete absence of information disclosure. To this end, we present Position-Independent Code-Reuse Attacks, a new class of codereuse attacks relying on the relative rather than absolute location of code gadgets in memory. By means of memory massaging, the attacker first makes the victim program generate a rudimentary ROP payload (for instance, containing code pointers that target instructions 'close' to relevant gadgets). Afterwards, the addresses in this payload are patched with small offsets via relative memory writes. To establish the practicality of such attacks, we present multiple Position-Independent ROP exploits against real-world software. After showing that we can bypass ASLR in current systems without requiring information disclosures, we evaluate the impact of our technique on other defenses, such as fine-grained ASLR, multi-variant execution, execute-only memory and re-randomization. We conclude by discussing potential mitigations