Return-Oriented Programming on RISC-V

This paper provides the first analysis on the feasibility of Return-Oriented Programming (ROP) on RISC-V, a new instruction set architecture targeting embedded systems. We show the existence of a new class of gadgets, using several Linear Code Sequences And Jumps (LCSAJ), undetected by current Galileo-based ROP gadget searching tools. We argue that this class of gadgets is rich enough on RISC-V to mount complex ROP attacks, bypassing traditional mitigation like DEP, ASLR, stack canaries, G-Free, as well as some compiler-based backward-edge CFI, by jumping over any guard inserted by a compiler to protect indirect jump instructions. We provide examples of such gadgets, as well as a proof-of-concept ROP chain, using C code injection to leverage a privilege escalation attack on two standard Linux operating systems. Additionally, we discuss some of the required mitigations to prevent such attacks and provide a new ROP gadget finder algorithm that handles this new class of gadgets.Comment: 27 pages, 8 figures, originally published at AsiaCCS 202

VPS: Excavating high-level C++ constructs from low-level binaries to protect dynamic dispatching

Polymorphism and inheritance make C++ suitable for writing complex software, but significantly increase the attack surface because the implementation relies on virtual function tables (vtables). These vtables contain function pointers that attackers can potentially hijack and in practice, vtable hijacking is one of the most important attack vector for C++ binaries. In this paper, we present VTable Pointer Separation (vps), a practical binary-level defense against vtable hijacking in C++ applications. Unlike previous binary-level defenses, which rely on unsound static analyses to match classes to virtual callsites, vps achieves a more accurate protection by restricting virtual callsites to validly created objects. More specifically, vps ensures that virtual callsites can only use objects created at valid object construction sites, and only if those objects can reach the callsite. Moreover, vps explicitly prevents false positives (falsely identified virtual callsites) from breaking the binary, an issue existing work does not handle correctly or at all. We evaluate the prototype implementation of vps on a diverse set of complex, real-world applications (MongoDB, MySQL server, Node.js, SPEC CPU2017/CPU2006), showing that our approach protects on average 97.8% of all virtual callsites in SPEC CPU2006 and 97.4% in SPEC CPU2017 (all C++ benchmarks), with a moderate performance overhead of 11% and 9% geomean, respectively. Furthermore, our evaluation reveals 86 false negatives in VTV, a popular source-based defense which is part of GCC

Mitigating code-reuse attacks with control-flow locking

Code-reuse attacks are software exploits in which an attacker directs control flow through existing code with a malicious result. One such technique, return-oriented programming, is based on“gadgets”(short pre-existing sequences of code end-ing in a ret instruction) being executed in arbitrary order as a result of a stack corruption exploit. Many existing code-reuse defenses have relied upon a particular attribute of the attack in question (e.g., the frequency of ret instructions in a return-oriented attack), which leads to an incomplete pro-tection, while a smaller number of efforts in protecting all exploitable control flow transfers suffer from limited deploy-ability due to high performance overhead. In this paper, we present a novel cost-effective defense technique called con-trol flow locking, which allows for effective enforcement of control flow integrity with a small performance overhead. Specifically, instead of immediately determining whether a control flow violation happens before the control flow trans-fer takes place, control flow locking lazily detects the viola-tion after the transfer. To still restrict attackers ’ capability, our scheme guarantees that the deviation of the normal con-trol flow graph will only occur at most once. Further, our scheme ensures that this deviation cannot be used to craft a malicious system call, which denies any potential gains an attacker might obtain from what is permitted in the threat model. We have developed a proof-of-concept prototype in Linux and our evaluation demonstrates desirable effective-ness and competitive performance overhead with existing techniques. In several benchmarks, our scheme is able to achieve significant gains. 1

On the Expressiveness of Return-into-libc Attacks

Abstract. Return-into-libc (RILC) is one of the most common forms of code-reuse attacks. In this attack, an intruder uses a buffer overflow or other exploit to redirect control flow through existing (libc) functions within the legitimate program. While dangerous, it is generally consid-ered limited in its expressive power since it only allows the attacker to ex-ecute straight-line code. In other words, RILC attacks are believed to be incapable of arbitrary computation—they are not Turing complete. Con-sequently, to address this limitation, researchers have developed other code-reuse techniques, such as return-oriented programming (ROP). In this paper, we make the counterargument and demonstrate that the orig-inal RILC technique is indeed Turing complete. Specifically, we present a generalized RILC attack called Turing complete RILC (TC-RILC) that allows for arbitrary computations. We demonstrate that TC-RILC sat-isfies formal requirements of Turing-completeness. In addition, because it depends on the well-defined semantics of libc functions, we also show that a TC-RILC attack can be portable between different versions (or even different families) of operating systems and naturally has negative implications for some existing anti-ROP defenses. The development of TC-RILC on both Linux and Windows platforms demonstrates the ex-pressiveness and practicality of the generalized RILC attack

Speculative Probing:Hacking Blind in the Spectre Era

To defeat ASLR or more advanced fine-grained and leakage-resistant code randomization schemes, modern software exploits rely on information disclosure to locate gadgets inside the victim's code. In the absence of such info-leak vulnerabilities, attackers can still hack blind and derandomize the address space by repeatedly probing the victim's memory while observing crash side effects, but doing so is only feasible for crash-resistant programs. However, high-value targets such as the Linux kernel are not crash-resistant. Moreover, the anomalously large number of crashes is often easily detectable. In this paper, we show that the Spectre era enables an attacker armed with a single memory corruption vulnerability to hack blind without triggering any crashes. Using speculative execution for crash suppression allows the elevation of basic memory write vulnerabilities into powerful speculative probing primitives that leak through microarchitectural side effects. Such primitives can repeatedly probe victim memory and break strong randomization schemes without crashes and bypass all deployed mitigations against Spectre-like attacks. The key idea behind speculative probing is to break Spectre mitigations using memory corruption and resurrect Spectre-style disclosure primitives to mount practical blind software exploits. To showcase speculative probing, we target the Linux kernel, a crash-sensitive victim that has so far been out of reach of blind attacks, mount end-to-end exploits that compromise the system with just-in-time code reuse and data-only attacks from a single memory write vulnerability, and bypass strong Spectre and strong randomization defenses. Our results show that it is crucial to consider synergies between different (Spectre vs. code reuse) threat models to fully comprehend the attack surface of modern systems