Configuring Fail2ban to work with firewalld

This document (000021067) is provided subject to the disclaimer at the end of this document.

Environment

SUSE Linux Enterprise Server 15 SP4
SUSE Linux Enterprise Server for SAP Applications 15 SP4

Situation

This document details how to configure Fail2ban service to work with firewalld on SLES15. Fail2ban can dynamically add rich rules to firewalld to block banned IPs. It will remove them if the Fail2ban service is stopped.

Resolution

1) Open /etc/fail2ban/jail.local file and add the banaction and banaction_allports parameters:

# Do all your modifications to the jail's configuration in jail.local!
[DEFAULT]
banaction = firewallcmd-rich-rules[actiontype=<multiport>]
banaction_allports = firewallcmd-rich-rules[actiontype=<allports>]

[sshd]
enabled = true

2) Restart Fail2ban service:

systemctl restart fail2ban.service

When Fail2ban blocks an IP it will also add a related rich rule to firewalld.
To verify all the firewalld rich rules:

firewall-cmd --list-all

firewall-cmd --list-rich-rules

Fail2ban deletes the rich rules from firewalld when Fail2ban service is stopped or the jail (in this case the [sshd] jail) is stopped (fail2ban-client stop sshd).

Additional Information

The banaction and banaction_allports parameters can be redefined centrally in the [DEFAULT] section inside jail.local (to apply it to all jails at once) or separately in each jail, where this substitution will be used.

jail.conf man page: https://manpages.opensuse.org/Tumbleweed/fail2ban/jail.conf.5.en.html

Fail2ban: https://www.fail2ban.org/wiki/index.php/Main_Page
https://github.com/fail2ban/fail2ban
Firewalld : https://firewalld.org/
Firewalld runtime vs permanent: https://firewalld.org/documentation/configuration/runtime-versus-permanent.html

Please note: Fail2ban package is supported only on SLES 15 SP4 and later versions. In previous releases of SLES Fail2ban is provided only through SUSE Package Hub. While the packages from the SUSE Package Hub are not officially supported by SUSE, SUSE Linux Enterprise Server remains supported and supportable when using these packages.

Disclaimer

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