Hardening CentOS 7 (firewalld, selinux)

Posted on September 10, 2014

I recently launched a CentOS 7 droplet and noticed that both firewalld and selinux were disabled by default. Does anyone have a good introductory guide on hardening CentOS 7?

I’m used to setting up an Ubuntu Server install such as:

ssh hardening (ports, retries, key_auth. fail2ban)
firewall hardening (ufw)
application specific hardening

This textbox defaults to using Markdown to format your answer.

You can type !ref in this text area to quickly search our full set of tutorials, documentation & marketplace offerings and insert the link!

These answers are provided by our Community. If you find them useful, show some love by clicking the heart. If you run into issues leave a comment, or add your own answer to help others.

Vehemeni

September 10, 2014

Read this post: https://www.digitalocean.com/community/tutorials/an-introduction-to-securing-your-linux-vps

conceptblossom

November 2, 2014

See here: RHEL7 Security Guide

And here: RHEL7 SELinux

In particular:

systemctl start firewalld
systemctl enable firewalld

And

vi /etc/selinux/config
set enforcing or permissive.
shutdown -r now     (or reboot)

After reboot, confirm:

 sestatus

And to harden ssh: First confirm you’re able to login via ssh keys. Then generate a list of all authentication methods, like this:

man sshd_config | grep 'Authentication$'

Then

vi /etc/ssh/sshd_config

Search for all instances of “Authentication” and comment them out. Paste the afore-generated list, as follows:

PubkeyAuthentication yes
RSAAuthentication no
ChallengeResponseAuthentication no
GSSAPIAuthentication no
HostbasedAuthentication no
KerberosAuthentication no
PasswordAuthentication no
RhostsRSAAuthentication no

And restart sshd