Cracking PicoCTF Challenge: GDB Baby Step 1 — StackZero

This article was originally published in its entirety at https://www.stackzero.net/gdb-baby-step-1/

Are you a beginner in the intriguing world of reverse engineering? Or perhaps you’re keen to delve into the workings of Linux’s GDB debugger? Either way, we’ve got you covered. Welcome to Stackzero, your one-stop destination for all things related to these topics. Here, we’ve curated a wealth of resources to guide your learning journey.
If you’re just starting out, we recommend our foundation guides on Reverse Engineering and GDB.
These easy-to-understand tutorials cover the basics of reverse engineering and using the GDB debugger. So why not take a few moments to read through them? It will give you the background knowledge you need to tackle the more complex challenges that lie ahead.
Today, we’re going to take on a particular challenge — the PicoCTF “GDB Baby Step 1”.
It’s an exciting task that tests your understanding of both reverse engineering and the GDB debugger.

Don’t worry if you’re new to these concepts, we’ll walk through it step by step.
Ready to embark on this exciting journey of discovery? Let’s jump in!

Preparations and File Analysis

Kickstart this adventurous journey by firing up your Kali Linux virtual machine.
Navigate to the PicoCTF website, locate the challenge named “GDB Baby Step 1,” in the “reverse engineering section”, familiarize yourself with the task by reading the description, and download the file.

After downloading, shift this file into your dedicated workspace where we can take our time to analyse it. Curious to know more about the file?
So run:

$ file debugger0_a 
debugger0_a: ELF 64-bit LSB pie executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, BuildID[sha1]=15a10290db2cd2ec0c123cf80b88ed7d7f5cf9ff, for GNU/Linux 3.2.0, not stripped