Question

Hardening CentOS 7 (firewalld, selinux)

  • Posted on September 10, 2014
  • storrgieAsked by storrgie

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
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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

systemctl restart sshd