How To Secure A Linux Server With Ansible

Ansible playbooks of "How To Secure A Linux Server".

These Ansible playbooks are made to help install secure Linux servers faster.

How to get started

1. Install Ansible
2. git clone this repository

git clone https://github.com/moltenbit/How-To-Secure-A-Linux-Server-With-Ansible
cd How-To-Secure-A-Linux-Server-With-Ansible

4. Create SSH-Public/Private-Keys

ssh-keygen -t ed25519

5. Change all variables in group_vars/variables.yml according to your needs.
6. Enable SSH root access before running the playbooks:

nano /etc/ssh/sshd_config
[...]
PermitRootLogin yes
[...]

7. Recommended: configure static IP address on your system.
8. Add your systems IP address to hosts.yml.

 

Run the requirements playbook using the root password you specified while installing the server:

ansible-playbook --inventory hosts.yml --ask-pass requirements-playbook.yml

 

Run the main playbook with the new users password you specified in the variables.yml file:

ansible-playbook --inventory hosts.yml --ask-pass main-playbook.yml

 

If you need to run the playbooks multiple times remember to use the SSH key and the new SSH port:

ansible-playbook --inventory hosts.yml -e ansible_ssh_port=SSH_PORT --key-file /PATH/TO/SSH/KEY main-playbook.yml

 

Tested on Debian 12 Bookworm.

Configurations

The playbook uses most of the settings from "How To Secure A Linux Server" / my choices if the guide has more than one option to do something.

Requirements

• sudo installed
• groups created for sshusers, sudousers and suusers
• new user created with the name specified in variables.yml and added to groups
• use of sudo limited to sudousers group
• use of su limited to suusers group
• passwordless sudo enabled for the new user
• SSH public key added to authorized_keys file

auditd

Uses best practice rules from Neo23x0

ClamAV

ClamAV is set to run everyday at 3 AM to scan the full system, exluding sys folders.

Firewall: UFW

UFW is set to default deny in and out. The SSH-Port is set to limit in, allowed outgoing ports by default are 53 (DNS), 123 (NTP), 80 (http), 443 (https) and the mail port specified in variables.yml.

Firewall: PSAD and Fail2Ban

PSAD and Fail2Ban is configured according to "How To Secure A Linux Server" guide.

Lynis

Lynis is configured according to "How To Secure A Linux Server" guide and will run an audit + send the report as an attachment to your mail address configured in variables.yml. Current Lynis rating is 77.

Mail

For mailing I chose msmtp with the help from Decatec's guide. This will send a testmail.

Packages

Installed packages are:

• apt-transport-https
• ca-certificates
• host
• kbtin
• ntp
• libpam-pwquality
• unattended-upgrades
• apt-listchanges
• apticron
• ufw
• psad
• fail2ban
• msmtp
• msmtp-mta
• mailutils
• clamav
• clamav-freshclam
• clamav-daemon
• rkhunter
• auditd
• audispd-plugins

Password quality

Password quality is done via pam_pwquality according to "How To Secure A Linux Server" guide.

Rkhunter

Rkhunter is configured according to "How To Secure A Linux Server" guide.

SSH

SSH is configured according to "How To Secure A Linux Server" guide.

Unattended upgrades

Unattended upgrades is configured to only upgrade security upgrades automatically. Automatic restarts are enabled.

Plans / ToDos

• use Ansible vault to securely store secrets

Warning!

Read all tasks carefully and make sure they do not break your system before using these playbooks! Do not rely solely on the Ansible playbooks for security! It is your responsibility to make sure all settings you need have been set and are working. This is just a starting point! Depending on your needs and goals make sure to further secure your system.

Credits

• imthenachoman for creating the great How To Secure A Linux Server guide
• Neo23x0 for the auditd best practice rules
• Decatec for the easy mail configuration