Binary firmware fuzzing has garnered attention in recent years. Compared to source-code-based approaches, binary approaches require less semantic information and are therefore more applicable. This is particularly relevant in firmware analysis, as most firmware vendors distribute only binaries, withholding source code due to proprietary concerns.Pivoting away from the traditional hardware-in-the-loop (HiL) methodology, researchers are exploring more efficient ways to engage real hardware for fuzzing. However, existing approaches have inherent drawbacks, such as reliance on high-end hardware features, inability to recover complete coverage, and slow execution speeds. We propose DRIFT, a novel approach for on-device binary firmware testing that follows the semihosting methodology. DRIFT addresses all the aforementioned drawbacks. The core insight of DRIFT is to use the Debug Monitor (DM) for firmware fuzzing. DM is a Arm Cortex-M CPU feature that allows triggering interrupt when a breakpoint is hit. Through chaining the DM interrupts, DRIFT is able let firmware to trace itself. This self-tracing approach minimizes interference from the workstation, significantly boosting fuzzing performance.We designed DRIFT to be highly flexible, accommodating a number of hardware resource limitations. When applied to new firmware, DRIFT discovered three previously unknown bugs that were not identified by existing binary fuzzing techniques. Furthermore, DRIFT outperforms all state-of-the-art binary firmware fuzzers in terms of speed and fidelity, trailing only SHiFT, an approach that requires source code.

Programmable Logic Controllers (PLCs) play a critical role in the industrial control systems. Vulnerabilities in PLC programs might lead to attacks causing devastating consequences to the critical infrastructure, as shown in Stuxnet and similar attacks. In recent years, we have seen an exponential increase in vulnerabilities reported for PLC control logic. Looking back on past research, we found extensive studies explored control logic modification attacks, as well as formal verification-based security solutions. We performed systematization on these studies, and found attacks that can compromise a full chain of control and evade detection. However, the majority of the formal verification research investigated ad-hoc techniques targeting PLC programs. We discovered challenges in every aspect of formal verification, rising from (1) the ever-expanding attack surface from evolved system design, (2) the real-time constraint during the program execution, and (3) the barrier in security evaluation given proprietary and vendor-specific dependencies on different techniques. Based on the knowledge systematization, we provide a set of recommendations for future research directions, and we highlight the need of defending security issues besides safety issues.

Microcontroller-based embedded devices are at the core of Internet-of-Things (IoT) and Cyber-Physical Systems (CPS). The security of these devices is of paramount importance. Among the approaches to securing embedded devices, dynamic firmware analysis (e.g., vulnerability detection) gained great attention lately, thanks to its offline nature and low false-positive rates. However, regardless of the analysis and emulation techniques used, existing dynamic firmware analyzers share a major limitation, namely the inability to handle firmware using DMA (Direct Memory Access). It severely limits the types of devices supported and firmware code coverage.We present DICE, a drop-in solution for firmware analyzers to emulate DMA input channels and generate or manipulate DMA inputs (from peripherals to firmware). DICE is designed to be hardware-independent (i.e., no actual peripherals or DMA controllers needed) and compatible with common MCU firmware (i.e., no firmware-specific DMA usages assumed) and embedded architectures. The high-level idea behind DICE is the identification and emulation of the abstract DMA input channels, rather than the highly diverse peripherals and controllers. DICE identifies DMA input channels as the firmware writes the source and destination DMA transfer pointers into the DMA controller. Then DICE manipulates the input transferred through DMA on behalf of the firmware analyzer. DICE does not require firmware source code or additional features from firmware analyzers.We integrated DICE to the recently proposed firmware analyzer P2IM (for ARM Cortex-M architecture) and a PIC32 emulator (for MIPS M4K/M-Class architecture). We evaluated it on 83 benchmarks and sample firmware, representing 9 different DMA controllers from 5 different vendors. DICE detected 33 out of 37 DMA input channels, with 0 false positives. It correctly supplied DMA inputs to 21 out of 22 DMA buffers that firmware actually use, which previous firmware analyzers cannot achieve due to the lack of DMA emulation. DICE’s overhead is fairly low, it adds 3.4% on average to P2IM execution time. We also fuzz-tested 7 real-world firmware using DICE and compared the results with the original P2IM. DICE uncovered tremendously more execution paths (as much as 79X) and found 5 unique previously-unknown bugs that are unreachable without DMA emulation. All our source code and dataset are publicly available.