GHIDRA for Reverse Engineering (PicoCTF 2022 #42 'bbbloat')

Summary

In this video, the presenter dives into the 'Bloat' reverse engineering challenge from Pico CTF 2022. Using Kali Linux, they explore the binary executable, attempting to uncover its operations. They utilize tools like ltrace and strace to trace library and system calls, then proceed with Ghidra for a deeper analysis. The video demonstrates how to use Ghidra to disassemble and decompile the binary, eventually discovering the logic behind the 'favorite number' prompt. The presenter successfully identifies the correct number, retrieves the flag, and concludes with encouragement to embrace the learning process of reverse engineering.

Takeaways

• 💻 The video is a tutorial on reverse engineering a binary file named 'bloat' from the pico CTF 2022 competition.
• 🐧 The presenter uses Kali Linux as the operating system for the hacking challenge.
• 🔍 The initial approach involves checking the binary with command line utilities like ltrace and strace to understand its behavior.
• 🛠 The binary is identified as a 64-bit LSB PIE (Position Independent Executable), suggesting it might have obfuscation techniques.
• 🔢 The binary prompts the user to guess a 'favorite number', with the number 42 being an incorrect guess.
• 🔧 Tools like objdump and Ghidra are mentioned for disassembling and analyzing the binary.
• 📜 Ghidra, developed by the NSA, is highlighted as a powerful reverse engineering tool, with instructions on how to install and use it.
• 🔄 The script mentions the use of Ghidra's decompilation feature to understand the program's logic and to find the 'favorite number'.
• 🎯 The video demonstrates how to use Ghidra to rename functions, analyze data types, and step through the program's logic to find the correct number.
• 🏁 The final step involves running the binary with the correct number, extracting the flag, and completing the challenge.

Q & A

What is the main topic of the video?

The main topic of the video is a walkthrough of a reverse engineering challenge called 'bloat' from the pico CTF 2022 competition.

What operating system is the presenter using for the challenge?

The presenter is using Kali Linux as the virtual machine for the challenge.

What tools does the presenter consider using for reverse engineering the binary?

The presenter considers using command line utilities like ltrace, strace, and more advanced tools like IDA Pro, GDB, Ghidra, and objdump for reverse engineering the binary.

What does the binary ask for when it is run?

When the binary is run, it asks for the presenter's favorite number.

What is the significance of the number 42 in the video?

The number 42 is mentioned as a potential favorite number input into the binary, referencing the answer to 'life, the universe, and everything' from The Hitchhiker's Guide to the Galaxy.

Why does the presenter decide to install ltrace and strace?

The presenter decides to install ltrace and strace to intercept and record the dynamic library calls and system calls made by the binary without stopping it, to gain insight into its behavior.

What does the presenter find out about the binary using file command?

The presenter finds out that the binary is a 64-bit LSB PIE (Position Independent Executable) executable.

What does Ghidra do and why is it used in the video?

Ghidra is a software reverse engineering tool developed by the National Security Agency, used in the video to analyze and decompile the binary to understand its functionality and to find the flag.

What is the presenter's approach to solving the challenge?

The presenter's approach involves running the binary to understand its behavior, using various tools to analyze it, and then using Ghidra to decompile the binary and find the logic that determines the correct favorite number.

How does the presenter confirm the correct favorite number to input into the binary?

The presenter confirms the correct favorite number by analyzing the decompiled code in Ghidra, finding the hexadecimal value that is checked against the input, converting it to decimal, and then entering it into the binary.