Born2beroot

The goal of this project is to set up a ssh server in a virtual machine (VM) using Virtual Box. A VM is a great way to test and/or use programs that should work on a specific Operating System other than yours, like a computer inside another computer.

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Operating System

We had to choose between CentOS and Debian. I have chosen Debian because it is easier to configure and a more user-friendly interface.

Setup

I had to make sure I followed some guidelines given by the subject:

• Create a VDI disk with dynamic allocation;
• Use Bridge Adapter mode;
• No graphic interface is allowed;
• Hostname should be my intranet username + 42
• Create a user besides root named after my intranet username
• Create a separate /home directory
• Install the least possible packages
• Enable GRUB (a bootloader, that is, a way to choose which OS will run once you start your VM)

Sudo setup

Sudo has to comply with a set of restrictions, which can be configured using sudo visudo.

These policies are:

• 3 password retries
• Add a custom error message when user types a wrong password.
• Enable TTY mode
• Create a sudo log in the /var/log/sudo directory
• Configure the secure path to /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/snap/bin

Users and Groups

I had to be able to create users besides root and to designate those users to certain groups.

Commands such as user add -m and groupadd and the respective variations were extremely useful for this part.

SSH service

I should be able to explain what a SSH service is, activate it in my VM and be able to use it only for the users that are not root. I also had to configure ssh to work only on port 4242.

UFW service

I also had to configure UFW firewall, explain what it is and how it works, and set it up to allow only port 4242.

Password policy

I had to implement a strong password policy. This was made by editing the /etc/login.def file fo the time-related configurations and installing libpa-pwquality package to implement the other, such as:

• min 10 characters
• no more than 3 consecutive equal characters
• restrict username
• and more

Cron and Wall

I should be able to explain what cron is and how to set it up. Cron in this case will be used to schedule the run of a script every 10 minutes since the VM is started. This configuration can be done via crontab -e.

Another useful command is wall, with which we can broadcast messages throughout the connected terminals.