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1. SoK: Enabling Security Analyses of Embedded Systems via Rehosting

   Fasano, Andrew ; Ballo, Tiemoko ; Muench, Marius ; Leek, Tim ; Bulekov, Alexander ; Dolan-Gavitt, Brendan ; Egele, Manuel ; Francillon, Aurelien ; Lu, Long ; Gregory, Nick ; et al ( June 2021 , ACM ASIA Conference on Computer and Communications Security (ASIACCS))

   null (Ed.)

   Closely monitoring the behavior of a software system during its execution enables developers and analysts to observe, and ultimately understand, how it works. This kind of dynamic analysis can be instrumental to reverse engineering, vulnerability discovery, exploit development, and debugging. While these analyses are typically well-supported for homogeneous desktop platforms (e.g., x86 desktop PCs), they can rarely be applied in the heterogeneous world of embedded systems. One approach to enable dynamic analyses of embedded systems is to move software stacks from physical systems into virtual environments that sufficiently model hardware behavior. This process which we call “rehosting” poses a significant research challenge with major implications for security analyses. Although rehosting has traditionally been an unscientific and ad-hoc endeavor undertaken by domain experts with varying time and resources at their disposal, researchers are beginning to address rehosting challenges systematically and in earnest. In this paper, we establish that emulation is insufficient to conduct large-scale dynamic analysis of real-world hardware systems and present rehosting as a firmware-centric alternative. Furthermore, we taxonomize preliminary rehost- ing efforts, identify the fundamental components of the rehosting process, and propose directions for future research. 

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2. Decomperson: How Humans Decompile and What We Can Learn From It

   Burk, K. ; Pagani, F. ; Kruegel, C. ; Vigna, G ( January 2023 , Proceedings of the USENIX conference)

   Human analysts must reverse engineer binary programs as a prerequisite for a number of security tasks, such as vulnerability analysis, malware detection, and firmware re-hosting. Existing studies of human reversers and the processes they follow are limited in size and often use qualitative metrics that require subjective evaluation. In this paper, we reframe the problem of reverse engineering binaries as the problem of perfect decompilation, which is the process of recovering, from a binary program, source code that, when compiled, produces binary code that is identical to the original binary. This gives us a quantitative measure of understanding, and lets us examine the reversing process programmatically. We developed a tool, called Decomperson, that supported a group of reverse engineers during a large-scale security competition designed to collect information about the participants' reverse engineering process, with the well-defined goal of achieving perfect decompilation. Over 150 people participated, and we collected more than 35,000 code submissions, the largest manual reverse engineering dataset to date. This includes snapshots of over 300 successful perfect decompilation attempts. In this paper, we show how perfect decompilation allows programmatic analysis of such large datasets, providing new insights into the reverse engineering process. 

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3. HALucinator: Firmware Re-hosting Through Abstraction Layer Emulation

   Clements, A ; Gustafson, E ; Scharnowski, T ; Grosen, P ; Fritz, D ; Kruegel, C ; Vigna, G ; Bagchi, S ; Payer, M. ( August 2020 , Proceedings of the 29th USENIX Security Symposium)

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   Given the increasing ubiquity of online embedded devices, analyzing their firmware is important to security, privacy, and safety. The tight coupling between hardware and firmware and the diversity found in embedded systems makes it hard to perform dynamic analysis on firmware. However, firmware developers regularly develop code using abstractions, such as Hardware Abstraction Layers (HALs), to simplify their job. We leverage such abstractions as the basis for the re-hosting and analysis of firmware. By providing high-level replacements for HAL functions (a process termed High-Level Emulation – HLE), we decouple the hardware from the firmware. This approach works by first locating the library functions in a firmware sample, through binary analysis, and then providing generic implementations of these functions in a full-system emulator. We present these ideas in a prototype system, HALucinator, able to re-host firmware, and allow the virtual device to be used normally. First, we introduce extensions to existing library matching techniques that are needed to identify library functions in binary firmware, to reduce collisions, and for inferring additional function names. Next, we demonstrate the re-hosting process, through the use of simplified handlers and peripheral models, which make the process fast, flexible, and portable between firmware samples and chip vendors. Finally, we demonstrate the practicality of HLE for security analysis, by supplementing HALucinator with the American Fuzzy Lop fuzzer, to locate multiple previously-unknown vulnerabilities in firmware middleware libraries. 

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4. Exploiting Memory Corruption Vulnerabilities in Connman for IoT Devices

   https://doi.org/10.1109/DSN.2019.00036  

   English, K. Virgil ; Obaidat, Islam ; Sridhar, Meera ( June 2019 , 49th Annual IEEE/IFIP International Conference on Dependable Systems and Networks (DSN))

   In the recent past, there has been a rapid increase in attacks on consumer Internet-of-Things (IoT) devices. Several attacks currently focus on easy targets for exploitation, such as weak configurations (weak default passwords). However, with governments, industries, and organizations proposing new laws and regulations to reduce and prevent such easy targets in the IoT space, attackers will move to more subtle exploits in these devices. Memory corruption vulnerabilities are a significant class of vulnerabilities in software security through which attackers can gain control of the entire system. Numerous memory corruption vulnerabilities have been found in IoT firmware already deployed in the consumer market. This paper presents an approach for exploiting stack-based buffer-overflow attacks in IoT firmware, to hijack the device remotely. To show the feasibility of this approach, we demonstrate exploiting a common network software application, Connman, used widely in IoT firmware such as Samsung smart TVs. A series of experiments are reported on, including: crashing and executing arbitrary code in the targeted software application in a controlled environment, adopting the attacks in uncontrolled environments (with standard software defenses such as W⊕X and ASLR enabled), and installing publicly available IoT firmware that uses this software application on a Raspberry Pi. The presented exploits demonstrate the ease in which an adversary can control IoT devices. 

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5. UPGRADVISOR: Early Adopting Dependency Updates Using Hybrid Program Analysis and Hardware Tracing

   Yaniv David ; Xudong Sun ; Raphael J. Sofaer ; Aditya Senthilnathan ; Junfeng Yang ; Zhiqiang Zuo ; Guoqing Harry Xu ; Jason Nieh ; Ronghui Gu ( July 2022 , USENIX Symposium on Operating Systems Design and Implementation)

   Applications often have fast-paced release schedules, but adoption of software dependency updates can lag by years, leaving applications susceptible to security risks and unexpected breakage. To address this problem, we present UPGRADVISOR, a system that reduces developer effort in evaluating dependency updates and can, in many cases, automatically determine which updates are backward-compatible versus API-breaking. UPGRADVISOR introduces a novel co-designed static analysis and dynamic tracing mechanism to gauge the scope and effect of dependency updates on an application. Static analysis prunes changes irrelevant to an application and clusters relevant ones into targets. Dynamic tracing needs to focus only on whether targets affect an application, making it fast and accurate. UPGRADVISOR handles dynamic interpreted languages and introduces call graph over-approximation to account for their lack of type information and selective hardware tracing to capture program execution while ignoring interpreter machinery. We have implemented UPGRADVISOR for Python and evaluated it on 172 dependency updates previously blocked from being adopted in widely-used open-source software, including Django, aws-cli, tfx, and Celery. UPGRADVISOR automatically determined that 56% of dependencies were safe to update and reduced by more than an order of magnitude the number of code changes that needed to be considered by dynamic tracing. Evaluating UPGRADVISOR’s tracer in a production-like environment incurred only 3% overhead on average, making it fast enough to deploy in practice. We submitted safe updates that were previously blocked as pull requests for nine projects, and their developers have already merged most of them. 

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