Recently, I took it upon myself to do some reverse engineering. From compressed binary back to directory structure, here’s how I did it:
The first step involved unpacking the compressed binary files. For this, I utilized a combination of open-source tools available for analyzing binary formats. Tools like Binwalk and LZMA SDK proved invaluable in extracting the contents of the binary. Binwalk, in particular, allowed me to analyze the file structure, revealing embedded files that were previously hidden. By finding and setting up the right Docker Container, I recovered files and directories that mirrored the original structure.
Once I had a grasp on the extracted content, I shifted my focus to understanding the file formats and their respective purposes. Then I selectively started flipping binaries back, one by one. Back to Assembly. And scanned the code for vulnerabilities.
The analysis involved using tools like IDA Free, Binwalk, Sasquatch, Strings, objdump, and diff to extract and examine the firmware’s components. The goal was to identify potential security flaws that could be exploited by malicious actors.
3. Analysis Methodology
The analysis process involved several key steps:
- Binary Inspection: Using IDA Free to examine the firmware binary structure. Use Claude 3.7 to translate this.
- Firmware Extraction: Employing Binwalk with Sasquatch to extract the filesystem from the compressed firmware image. The 3rd Docker Container with prebuilt Sasquatch worked, I was stuck here for over an hour.
- Filesystem Analysis: Investigating the extracted files, including configuration files, scripts, and binaries.
- Code Examination: Scrutinizing scripts (e.g., Lua scripts) for vulnerabilities such as command injection and insecure authentication practices.
- Binary Reverse Engineering: Decompiling and disassembling binaries like `debug_monitor` and `nvramUpdate` to identify security flaws.
During my exploration, I uncovered several vulnerabilities that raised significant concerns about the security of the hardware drivers. One particularly glaring issue was the presence of a manufacturer function that had been inadvertently left in the production code. ‘debug_monitor’ was likely intended for internal debugging or configuration, exposed sensitive operations to potential attackers.
Examining this function revealed that it could be exploited to gain unauthorized access to critical system controls. The lack of proper input validation and error handling in this code segment presented an easy entry point for malicious actors. Furthermore, the test suite included 1 set of updates credentials in plain-text, looking vulnerable to MITM or DNS SSL Spoofing or TFTP spoofing. All of this takes practice and time efforts I want to give to this project, and yet I hesitate.
It is clar that even minor oversights in code management could lead to significant security risks, potentially compromising entire systems. This realization not only heightens my awareness of software vulnerabilities but also reinforces the need for ongoing Source Code Auditor vigilance in the realm of hardware security. Identifying such vulnerabilities emphasizes the importance of rigorous code auditing and the necessity for manufacturers to implement better practices in their development processes.
As I continue my exploration, it is abundantly clear that there is a vast landscape yet to cover in the realm of reverse engineering firmware drivers. The Manufacturer wrote me back and requested POC (Proof-of-Compromise). This is a standard in Vulnerability reporting and espeically a requirement for CVE issuance.
Each step of this journey opens new avenues for investigation and discovery, particularly in the context of identifying vulnerabilities that could lead to creating a Common Vulnerabilities and Exposures (CVE) entry.
Additionally, delving into system call interfaces can reveal misconfigurations or overlooked functions that allow for privilege escalation, a critical area for security concerns. Lastly, the use of static and dynamic analysis tools to probe deeper into the driver’s runtime behavior could uncover timing attacks or race conditions, both of which are fertile ground for discovering security flaws that warrant CVE identification.
The more I explore, the more I realize that the potential for uncovering vulnerabilities is practically limitless, underscoring the hiring source code auditors, hiring reverse engineers, and other proactive measures in firmware security.
