Config fail2ban

What is fail2ban ?

Fail2ban is an intrusion prevention software framework which protects computer servers from brute-force attacks. Written in the Python programming language, it is able to run on POSIX systems that have an interface to a packet-control system or firewall installed locally, for example, iptables or TCP Wrapper.

(Definition from wikipedia - https://en.wikipedia.org/wiki/Fail2ban)

Why do I need to install this fail2ban's filter ?

To protect your seafile website against brute force attemps. Each time a user/computer tries to connect and fails 3 times, a new line will be write in your seafile logs (seahub.log).

Fail2ban will check this log file and will ban all failed authentications with a new rule in your firewall.

Installation

Change to right Time Zone in seahub_settings.py

WARNING: Without this your Fail2Ban filter will not work.

You need to add the following settings to seahub_settings.py but change it to your own time zone.

# TimeZone
TIME_ZONE = 'Europe/Stockholm'

Copy and edit jail.local file

WARNING: this file may override some parameters from your jail.conf file

Edit jail.local with :

  • ports used by your seafile website (e.g. http,https) ;

  • logpath (e.g. /home/yourusername/logs/seahub.log) ;

  • maxretry (default to 3 is equivalent to 9 real attemps in seafile, because one line is written every 3 failed authentications into seafile logs).

Create the file jail.local in /etc/fail2ban with the following content:

# All standard jails are in the file configuration located
# /etc/fail2ban/jail.conf
# Warning you may override any other parameter (e.g. banaction,
# action, port, logpath, etc) in that section within jail.local
# Change logpath with your file log used by seafile (e.g. seahub.log)
# Also you can change the max retry var (3 attemps = 1 line written in the
# seafile log)
# So with this maxrety to 1, the user can try 3 times before his IP is banned
[seafile]
enabled = true
port = http,https
filter = seafile-auth
logpath = /home/yourusername/logs/seahub.log
maxretry = 3

Create the fail2ban filter file seafile-auth.conf in /etc/fail2ban/filter.d with the following content:

# Fail2Ban filter for seafile
#
[INCLUDES]
# Read common prefixes. If any customizations available -- read them from
# common.local
before = common.conf
[Definition]
_daemon = seaf-server
failregex = Login attempt limit reached.*, ip: <HOST>
ignoreregex =
# DEV Notes:
#
# pattern : 2015-10-20 15:20:32,402 [WARNING] seahub.auth.views:155 login Login attempt limit reached, username: <user>, ip: 1.2.3.4, attemps: 3
# 2015-10-20 17:04:32,235 [WARNING] seahub.auth.views:163 login Login attempt limit reached, ip: 1.2.3.4, attempts: 3

Restart fail2ban

Finally, just restart fail2ban and check your firewall (iptables for me) :

sudo fail2ban-client reload
sudo iptables -S

Fail2ban will create a new chain for this jail. So you should see these new lines :

...
-N fail2ban-seafile
...
-A fail2ban-seafile -j RETURN

Tests

To do a simple test (but you have to be an administrator on your seafile server) go to your seafile webserver URL and try 3 authentications with a wrong password.

Actually, when you have done that, you are banned from http and https ports in iptables, thanks to fail2ban.

To check that :

on fail2ban

[email protected]:~$ sudo fail2ban-client status seafile
Status for the jail: seafile
|- filter
| |- File list: /home/<youruser>/logs/seahub.log
| |- Currently failed: 0
| `- Total failed: 1
`- action
|- Currently banned: 1
| `- IP list: 1.2.3.4
`- Total banned: 1

on iptables :

sudo iptables -S
...
-A fail2ban-seafile -s 1.2.3.4/32 -j REJECT --reject-with icmp-port-unreachable
...

To unban your IP address, just execute this command :

sudo fail2ban-client set seafile unbanip 1.2.3.4

Note

As three (3) failed attempts to login will result in one line added in seahub.log a Fail2Ban jail with the settings maxretry = 3 is the same as nine (9) failed attempts to login.