Biblio

Software development and deployment are generally fast-pacing practices, yet to date there is still a significant amount of legacy software running in various critical industries with years or even decades of lifespans. As the source code of some legacy software became unavailable, it is difficult for maintainers to actively patch the vulnerabilities, leaving the outdated binaries appealing targets of advanced security attacks. One of the most powerful attacks today is code reuse, a technique that can circumvent most existing system-level security facilities. While there have been various countermeasures against code reuse, applying them to sourceless software appears to be exceptionally challenging. Fine-grained code randomization is considered to be an effective strategy to impede modern code-reuse attacks. To apply it to legacy software, a technique called binary rewriting is employed to directly reconstruct binaries without symbol or relocation information. However, we found that current rewriting-based randomization techniques, regardless of their designs and implementations, share a common security defect such that the randomized binaries may remain vulnerable in certain cases. Indeed, our finding does not invalidate fine-grained code randomization as a meaningful defense against code reuse attacks, for it significantly raises the bar for exploits to be successful. Nevertheless, it is critical for the maintainers of legacy software systems to be aware of this problem and obtain a quantitative assessment of the risks in adopting a potentially incomprehensive defense. In this paper, we conducted a systematic investigation into the effectiveness of randomization techniques designed for hardening outdated binaries. We studied various state-of-the-art, fine-grained randomization tools, confirming that all of them can leave a certain part of the retrofitted binary code still reusable. To quantify the risks, we proposed a set of concrete criteria to classify gadgets immune to rewriting-based randomization and investigated their availability and capability.

Code randomization is considered as the basis of mitigation against code reuse attacks, fundamentally supporting some recent proposals such as execute-only memory (XOM) that aims at dynamic return-oriented programming (ROP) attacks. However, existing code randomization methods are hard to achieve a good balance between high-randomization entropy and semantic consistency. In particular, they always ignore code semantic consistency, incurring performance loss and incompatibility with current security schemes, e.g., control flow integrity (CFI). In this paper, we present an enhanced code randomization method termed as HCRESC, which can improve the randomization entropy significantly, meanwhile ensure the semantic consistency between variants and the original code. HCRESC reschedules instructions within the range of functions rather than basic blocks, thus producing more variants of the original code and preserving the code's semantic. We implement HCRESC on Linux platform of x86-64 architecture and demonstrate that HCRESC can increase the randomization entropy of x86-64 code over than 120% compared with existing methods while ensuring control flow and size of the code unaltered.

Bare-metal microcontrollers are a family of Internet of Things (IoT) devices which are increasingly deployed in critical industrial environments. Similar to other IoT devices, bare-metal microcontrollers are vulnerable to memory corruption and code-reuse attacks. We propose MicroGuard, a novel mitigation method based on component-level sandboxing and automated code randomization to securely encapsulate application components in isolated environments. We implemented MicroGuard and evaluated its efficacy and efficiency with a real-world benchmark against different types of attacks. As our evaluation shows, MicroGuard provides better security than ACES, current state-of-the-art protection framework for bare-metal microcontrollers, with a comparable performance overhead.

Code reuse attacks can bypass the DEP mechanism effectively. Meanwhile, because of the stealthy of the operation, it becomes one of the most intractable threats while securing the information system. Although the security solutions of code randomization and diversity can mitigate the threat at a certain extent, attackers can bypass these solutions due to the high cost and coarsely granularity, and the memory disclosure vulnerability is another magic weapon which can be used by attackers to bypass these solutions. After analyzing the principle of memory disclosure vulnerability, we propose a novel code pointer hiding method based on a resilient area. We expatiate how to create the resilient area and achieve code pointer hiding from four aspects, namely hiding return addresses in data pages, hiding function pointers in data pages, hiding target pointers of instruction JUMP in code pages, and hiding target pointers of instruction CALL in code pages. This method can stop attackers from reading and analyzing pages in memory, which is a critical stage in finding and creating ROP chains while executing a code reuse attack. Lastly, we test the method contrastively, and the results show that the method is feasible and effective while defending against ROP attacks.

Despite decades of research on software diversification, only address space layout randomization has seen widespread adoption. Code randomization, an effective defense against return-oriented programming exploits, has remained an academic exercise mainly due to i) the lack of a transparent and streamlined deployment model that does not disrupt existing software distribution norms, and ii) the inherent incompatibility of program variants with error reporting, whitelisting, patching, and other operations that rely on code uniformity. In this work we present compiler-assisted code randomization (CCR), a hybrid approach that relies on compiler-rewriter cooperation to enable fast and robust fine-grained code randomization on end-user systems, while maintaining compatibility with existing software distribution models. The main concept behind CCR is to augment binaries with a minimal set of transformation-assisting metadata, which i) facilitate rapid fine-grained code transformation at installation or load time, and ii) form the basis for reversing any applied code transformation when needed, to maintain compatibility with existing mechanisms that rely on referencing the original code. We have implemented a prototype of this approach by extending the LLVM compiler toolchain, and developing a simple binary rewriter that leverages the embedded metadata to generate randomized variants using basic block reordering. The results of our experimental evaluation demonstrate the feasibility and practicality of CCR, as on average it incurs a modest file size increase of 11.46% and a negligible runtime overhead of 0.28%, while it is compatible with link-time optimization and control flow integrity.

Memory-corruption vulnerabilities pose a severe threat on modern systems security. Although this problem is known for almost three decades it is unlikely to be solved in the near future because a large amount of modern software is still programmed in unsafe, legacy languages such as C/C++. With new vulnerabilities in popular software discovered almost every day, and with high third party demand for (purchasing) the corresponding exploits, runtime attacks are more prevalent than ever. Even perfect cryptography can easily be undermined by exploiting software vulnerabilities. Typically, one vulnerability in wide-spread software (e.g., Tor Browser) is sufficient for the adversary to compromise all users. Moving target approaches such as software diversity [2] and system randomization techniques [7] are considered to be effective and practical means to strongly reduce the scale of such attacks because ideally, the adversary would require to craft a unique exploit per user. However, recently it was shown that existing software-randomization schemes can be circumvented by practical exploitation techniques such as Just-In-Time Return Oriented Programming (JIT-ROP) that takes advantage of information leakage [1]. The attack demonstrated that even a single disclosed code pointer can be exploited to defeat any (fine-grained) code randomization scheme. Later, it was shown that there are various sources of information leakage that can be exploited such as virtual function pointers [4]. JIT-ROP motivated a number of subsequent works to prevent the adversary from reading code such as Readactor [3,5], or ASLR Guard [8]. For instance, Readactor and its successor Readactor++ [3,5] use various techniques to prevent direct and indirect code disclosure, which seems to be non-trivial in general [6]. The arms race will continue.