Intel Software Guard Extensions (SGX) is a set of extensions built into Intel CPUs for the trusted computation. It creates a hardware-assisted secure container, within which programs are protected from data leakage and data manipulations by privileged software and hypervisors. With the trend that more and more machine learning based programs are moving to cloud computing, SGX can be used in cloud-based Machine Learning applications to protect user data from malicious privileged programs.However, applications running in SGX suffer from several overheads, including frequent context switching, memory page encryption/decryption, and memory page swapping, which significantly degrade the execution efficiency. In this paper, we aim to i) comprehensively explore the execution of general AI applications running on SGX, ii) systematically characterize the data reuses at both page granularity and cacheline granularity, and iii) provide optimization insights for efficient deployment of machine learning based applications on SGX. To the best of our knowledge, our work is the first to study machine learning applications on SGX and explore the potential of data reuses to reduce the runtime overheads in SGX.

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legacy software became unavailable, it is difficult for maintainers to actively patch the vulnerabilities, leaving the outdated binaries appealing targets of advanced security attacks.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.

With the thriving of mobile app markets, third-party libraries are pervasively used in Android applications. The libraries provide functionalities such as advertising, location, and social networking services, making app development much more productive. However, the spread of vulnerable and harmful third-party libraries can also hurt the mobile ecosystem, leading to various security problems. Therefore, third-party library identification has emerged as an important problem, being the basis of many security applications such as repackaging detection, vulnerability identification, and malware analysis. Previously, we proposed a novel approach to identifying third-party Android libraries at a massive scale. Our method uses the internal code dependencies of an app to recognize library candidates and further classify them. With a fine-grained feature hashing strategy, we can better handle code whose package and method names are obfuscated than historical work. We have developed a prototypical tool called LibD and evaluated it with an up-to-date dataset containing 1,427,395 Android apps. Our experiment results show that LibD outperforms existing tools in detecting multi-package third-party libraries with the presence of name-based obfuscation, leading to significantly improved precision without the loss of scalability. In this paper, we extend our early work by investigating the possibility of employing effective and scalable library detection to boost the performance of large-scale app analyses in the real world. We show that the technique of LibD can be used to accelerate whole-app Android vulnerability detection and quickly identify variants of vulnerable third-party libraries. This extension paper sheds light on the practical value of our previous research.

Intel Software Guard eXtension (SGX), a hardware supported trusted execution environment (TEE), is designed to protect security critical applications. However, it does not terminate traditional memory corruption vulnerabilities for the software running inside enclave, since enclave software is still developed with type unsafe languages such as C/C++. This paper presents RUST-SGX, an efficient and layered approach to exterminating memory corruption for software running inside SGX enclaves. The key idea is to enable the development of enclave programs with an efficient memory safe system language Rust with a RUST-SGX SDK by solving the key challenges of how to (1) make the SGX software memory safe and (2) meanwhile run as efficiently as with the SDK provided by Intel. We therefore propose to build RUST-SGX atop Intel SGX SDK, and tame unsafe components with formally proven memory safety. We have implemented RUST-SGX and tested with a series of benchmark programs. Our evaluation results show that RUST-SGX imposes little extra overhead (less than 5% with respect to the SGX specific features and services compared to software developed by Intel SGX SDK), and meanwhile have stronger memory safety.

Summary In recent years, mobile apps have become the infrastructure of many popular Internet services. It is now common that a mobile app serves millions of users across the globe. By examining the code of these apps, reverse engineers can learn various knowledge about the design and implementation of the apps. Real‐world cases have shown that the disclosed critical information allows malicious parties to abuse or exploit the app‐provided services for unrightful profits, leading to significant financial losses. One of the most viable mitigations against malicious reverse engineering is to obfuscate the apps. Despite that security by obscurity is typically considered to be an unsound protection methodology, software obfuscation can indeed increase the cost of reverse engineering, thus delivering practical merits for protecting mobile apps. In this paper, we share our experience of applying obfuscation to multiple commercial iOS apps, each of which has millions of users. We discuss the necessity of adopting obfuscation for protecting modern mobile business, the challenges of software obfuscation on the iOS platform, and our efforts in overcoming these obstacles. We especially focus on factors that are unique to mobile software development that may affect the design and deployment of obfuscation techniques. We report the outcome of our obfuscation with empirical experiments. We additionally elaborate on the follow‐up case studies about how our obfuscation affected the app publication process and how we responded to the negative impacts. This experience report can benefit mobile developers, security service providers, and Apple as the administrator of the iOS ecosystem.

The prosperity of smartphone markets has raised new concerns about software security on mobile platforms, leading to a growing demand for effective software obfuscation techniques. Due to various differences between the mobile and desktop ecosystems, obfuscation faces both technical and non-technical challenges when applied to mobile software. Although there have been quite a few software security solution providers launching their mobile app obfuscation services, it is yet unclear how real-world mobile developers perform obfuscation as part of their software engineering practices.

With the thriving of the mobile app markets, third-party libraries are pervasively integrated in the Android applications. Third-party libraries provide functionality such as advertisements, location services, and social networking services, making multi-functional app development much more productive. However, the spread of vulnerable or harmful third-party libraries may also hurt the entire mobile ecosystem, leading to various security problems. The Android platform suffers severely from such problems due to the way its ecosystem is constructed and maintained. Therefore, third-party Android library identification has emerged as an important problem which is the basis of many security applications such as repackaging detection and malware analysis. According to our investigation, existing work on Android library detection still requires improvement in many aspects, including accuracy and obfuscation resilience. In response to these limitations, we propose a novel approach to identifying third-party Android libraries. Our method utilizes the internal code dependencies of an Android app to detect and classify library candidates. Different from most previous methods which classify detected library candidates based on similarity comparison, our method is based on feature hashing and can better handle code whose package and method names are obfuscated. Based on this approach, we have developed a prototypical tool called LibD and evaluated it with an update-to-date and large-scale dataset. Our experimental results on 1,427,395 apps show that compared to existing tools, LibD can better handle multi-package third-party libraries in the presence of name-based obfuscation, leading to significantly improved precision without the loss of scalability.

Many techniques of software vulnerability exploitation rely on deep and comprehensive analysis of vulnerable program binaries. If a copy of the vulnerable software is available to attackers, they can compose their attack scripts and payloads by studying the sample copy and launch attacks on other copies of the same software in deployment. By transforming software into different forms before deployment, software diversification is considered as an effective mitigation of attacks originated from malicious binary analyses.Essentially, developing a software diversification transformation is nontrivial because it has to preserve the original functionality, provide strong enough unpredictability, and introduce negligible cost. Enlightened by research in other areas, we seek to apply different diversification transformations to the same program for a synergy effect such that the resulting hybrid transformations can have boosted diversification effects with modest cost. We name this approach the composite software diversification.Although the concept is straightforward, it becomes challenging when searching for satisfactory compositions of primitive transformations that maximize the synergy effect and make a balance between effectiveness and cost. In this work, we undertake an in-depth study and develop a reasonably well working selection strategy to find a transformation composition that performs better than any single transformation used in the composition. We believe our work can provide guidelines for practitioners who would like to improve the design of diversification tools in the future.

Function recognition in program binaries serves as the foundation for many binary instrumentation and analysis tasks. However, as binaries are usually stripped before distribution, function information is indeed absent in most binaries. By far, identifying functions in stripped binaries remains a challenge. Recent research work proposes to recognize functions in binary code through machine learning techniques. The recognition model, including typical function entry point patterns, is automatically constructed through learning. However, we observed that as previous work only leverages syntax-level features to train the model, binary obfuscation techniques can undermine the pre-learned models in real-world usage scenarios. In this paper, we propose FID, a semantics-based method to recognize functions in stripped binaries. We leverage symbolic execution to generate semantic information and learn the function recognition model through well-performing machine learning techniques.FID extracts semantic information from binary code and, therefore, is effectively adapted to different compilers and optimizations. Moreover, we also demonstrate that FID has high recognition accuracy on binaries transformed by widely-used obfuscation techniques. We evaluate FID with over four thousand test cases. Our evaluation shows that FID is comparable with previous work on normal binaries and it notably outperforms existing tools on obfuscated code.

After a program has crashed and terminated abnormally, it typically leaves behind a snapshot of its crashing state in the form of a core dump. While a core dump carries a large amount of information, which has long been used for software debugging, it barely serves as informative debugging aids in locating software faults, particularly memory corruption vulnerabilities. A memory corruption vulnerability is a special type of software faults that an attacker can exploit to manipulate the content at a certain memory. As such, a core dump may contain a certain amount of corrupted data, which increases the difficulty in identifying useful debugging information (e.g. , a crash point and stack traces). Without a proper mechanism to deal with this problem, a core dump can be practically useless for software failure diagnosis. In this work, we develop CREDAL, an automatic tool that employs the source code of a crashing program to enhance core dump analysis and turns a core dump to an informative aid in tracking down memory corruption vulnerabilities. Specifically, CREDAL systematically analyzes a core dump potentially corrupted and identifies the crash point and stack frames. For a core dump carrying corrupted data, it goes beyond the crash point and stack trace. In particular, CREDAL further pinpoints the variables holding corrupted data using the source code of the crashing program along with the stack frames. To assist software developers (or security analysts) in tracking down a memory corruption vulnerability, CREDAL also performs analysis and highlights the code fragments corresponding to data corruption.

Program obfuscation is an important software protection technique that prevents attackers from revealing the programming logic and design of the software. We introduce translingual obfuscation, a new software obfuscation scheme which makes programs obscure by "misusing" the unique features of certain programming languages. Translingual obfuscation translates part of a program from its original language to another language which has a different programming paradigm and execution model, thus increasing program complexity and impeding reverse engineering. In this paper, we investigate the feasibility and effectiveness of translingual obfuscation with Prolog, a logic programming language. We implement translingual obfuscation in a tool called BABEL, which can selectively translate C functions into Prolog predicates. By leveraging two important features of the Prolog language, i.e., unification and backtracking, BABEL obfuscates both the data layout and control flow of C programs, making them much more difficult to reverse engineer. Our experiments show that BABEL provides effective and stealthy software obfuscation, while the cost is only modest compared to one of the most popular commercial obfuscators on the market. With BABEL, we verified the feasibility of translingual obfuscation, which we consider to be a promising new direction for software obfuscation.

Software instrumentation techniques are widely used in program analysis tasks such as program profiling, vulnerability discovering, and security-oriented transforming. In this paper, we present an instrumentation tool called UROBOROS, which supports static instrumentation on stripped binaries. Due to the lack of relocation and debug information, reverse engineering of stripped binaries is challenging. Compared with the previous work, UROBOROS can provide complete, easy-to-use, transparent, and efficient static instrumentation on stripped binaries. UROBOROS supports complete instrumentation by statically recovering the relocatable program (including both code and data sections) and the control flow structures from binary code. UROBOROS provides a rich API to access and manipulate different levels of the program tructure. The instrumentation facilities of UROBOROS are easy-to-use, users with no binary rewriting and patching skills can directly manipulate stripped binaries to perform smooth program transformations. Distinguished from most instrumentation tools that need to patch the instrumentation code as new sections, UROBOROS can directly inline the instrumentation code into the disassembled program, which provides transparent instrumentation on stripped binaries. For efficiency, in the rewritten output of existing tools, frequent control transfers between the attached and original sections can incur a considerable performance penalty. However, the output from UROBOROS incurs no extra cost because the original and instrumentation code are connected by "fall-through" transfers. We perform comparative evaluations between UROBOROS and the state-of-the-art binary instrumentation tools, including DynInst and Pin. To demonstrate the versatility of UROBOROS, we also implement two real-world reengineering tasks which could be challenging for other instrumentation tools to accomplish. Our experimental results show that UROBOROS outperforms theexisting binary instrumentation tools with better performance, lower labor cost, and a broader scope of applications.