What are the best practices and tools for firmware extraction and dumping?

1 Identify the device and firmware

In order to extract and dump the firmware, you must first identify the device and its firmware. To do this, you can leverage various sources of information such as the model number, serial number, labels or stickers, user manual, datasheet or specification sheet, web interface or configuration page, network traffic or protocols, and the firmware download link, file name or checksum. With this information you can select the appropriate tools and methods for your task.

3 Analyze the firmware file

Once you have extracted and dumped the firmware file, you need to analyze it to understand its structure, format, and content. You can employ various tools and techniques to analyze the firmware file, such as the File command-line tool to identify the file type and magic number; Binwalk to extract the files and partitions from the firmware file; a Hex editor to inspect the firmware file; and a Firmware analysis framework to automate the analysis of firmware files. These tools can help you identify devices, libraries, and vulnerabilities; emulate firmware execution; and uncover strings, patterns, or signatures that may indicate its features, functions, or secrets.

4 Decompile and disassemble the code

Once you have analyzed the firmware file and extracted the code files, you need to decompile and disassemble them to convert them into a human-readable format. Various tools and languages can be used for this purpose, including a decompiler that converts binary code into high-level source code, such as C or Python. This tool can help you reconstruct the logic, syntax, and variables of the code to understand its functionality and features. On the other hand, a disassembler can convert binary code into low-level assembly code, such as ARM or MIPS. This tool can be used to examine instructions, registers, and memory addresses to understand the behavior and operations of the code. Additionally, a reverse engineering tool combines decompilation and disassembly with analysis and debugging features to perform tasks such as renaming variables and functions or modifying code.

5 Modify and repackage the firmware

Once you have decompiled and disassembled the code and implemented the desired changes, you need to modify and repackage the firmware file for flashing back to the device. Compilers and assemblers can be used to rebuild the code files after modifications, while binwalk and dd can be employed to replace old code files and generate a new firmware file with the same structure as the original. Hex editors and checksum calculators can then be used to modify the headers, footers, or signatures of the firmware file, as well as to calculate its checksum or hash value for validating its integrity.