CTF Study Part 1 (Kali Linux Installation on VirtualBox, Environment Setup, and OpenVPN)
管理人Introduction
In this post, to study for CTF (Capture The Flag), I set up a Kali Linux environment and configured connections using OpenVPN.
I am planning to participate in a CTF competition soon, so I am currently studying, even if it is a bit of a last-minute effort.
▼Kali Linux was introduced in the following book. It is useful for working on TryHackMe.
ポチップ
▼Previous articles are here:
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Kali Linux Environment Setup
▼I am using a gaming laptop purchased for around 100,000 yen, running Windows 11.
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ポチップ
I usually use an Ubuntu environment with WSL2, but this time I will run Kali Linux on VirtualBox.
▼The VirtualBox page is here:
https://www.oracle.com/jp/virtualization/technologies/vm/downloads/virtualbox-downloads.html
I installed the Kali Linux image specifically for VirtualBox.
▼I downloaded it from this page. It is about 3.5GB.
https://www.kali.org/get-kali/#kali-virtual-machines
▼After extracting, it was about 14GB.
▼I added the downloaded file to VirtualBox.
After adding it, I tried to start it.
▼After a short while, the login screen appeared.
It seems both the default username and password are "kali".
▼I was able to log in!
Just in case, I also changed the password using the "passwd" command.
Changing Settings and Installing Software
The screen was small, so I made it larger.
▼I changed the Resolution from the Display settings.
▼The display became larger.
I thought about keeping the language in English, but I changed the keyboard layout because the special symbols differ if it is not set to Japanese.
▼I changed it via the Keyboard app.
▼I changed the Layout to Japanese.
I updated the packages using the following commands:
sudo apt update
sudo apt upgrade -y▼In the middle of the process, I was asked if it was okay to restart services.
▼There seems to be a terminal that allows you to enter and execute as Root from the start.
I also installed Google Chrome. Although packages can be downloaded via command line, I downloaded it through Firefox. Unlike using Ubuntu on WSL2, having a desktop screen makes it easy to operate.
▼When I opened the default browser, a page appeared that seemed to provide access to various tools.
After downloading, I installed it using "apt install":
cd Downloads
sudo apt install ./google-chrome-stable_current_amd64.deb▼Installation was successful.
I also installed VS Code.
▼This was also installed without any issues.
The screen was automatically turning off after a period of inactivity, so I disabled that feature.
▼I opened the Power Manager.
▼I went to Screensaver Management and turned it off.
When I searched for "power," I noticed that even though it is Linux, PowerShell exists! I am curious about how people use them for different purposes.
There was also something called "starkiller," so I looked it up.
▼It is described as a frontend for PowerShell Empire.
https://github.com/BC-SECURITY/Starkiller
▼Empire is introduced as a framework for red teams and penetration testers.
https://github.com/BC-SECURITY/Empire
In books, Kali Linux is introduced as a "hacker tool all-in-one pack," and it seems that just the terminal-related tools are more numerous than in a standard Ubuntu environment.
Overall, the operation felt slow, and even "apt upgrade" was taking a considerable amount of time. Looking at the Task Manager, there was plenty of memory, but it seemed that swap memory was being allocated.
▼I have allocated swap memory before out of necessity because the Raspberry Pi Zero 2 had very little memory.
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VirtualBox's memory allocation was originally small at 2048MB, so I expanded it.
▼I have replaced the memory in my laptop with 64GB to run local LLMs.
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▼Change this from the VirtualBox settings.
I couldn't change it while Kali Linux was running, so I changed it after shutting it down.
▼From the System settings, I allocated about 16GB of memory.
▼I increased the processors from 2 to 4 CPUs.
▼The changes were applied.
Since this is for security studies like CTF, I don't think I will be performing very heavy processing, but I plan to adjust it further if it still feels slow.
Confirming OpenVPN Connection
I logged into TryHackMe using Google Chrome on Kali Linux and performed a VPN connection according to the OpenVPN room instructions.
▼The TryHackMe OpenVPN room is here:
https://tryhackme.com/room/openvpn
I proceeded according to the TryHackMe instructions.
▼I clicked on Access Machine.
▼This time, I will connect using OpenVPN.
▼Instructions for connecting on Linux were displayed.
I clicked Download to download the Configuration pack.
By the way, openvpn was already installed in Kali Linux.
▼In the WSL2 Ubuntu 20.04 environment I often use, OpenVPN did not seem to be included.
The file was downloaded into the Downloads folder with the name "download," so I ran openvpn using the following command:
sudo openvpn ./Downloads/downloadIn this state, I accessed the website through the browser.
▼I selected Start Machine.
When I accessed the IP address displayed at the top of the room, the website appeared, and I entered the flag found on the page as the answer. It seems the VPN connection worked without any problems.
Finally
The Kali Linux environment I built this time is being used for CTF. It was my first time using VirtualBox, and unlike WSL2, having a desktop screen is very convenient.
▼There is a CTF site called AlpacaHack, and I am trying out various things while studying.
