#!/usr/bin/perl
# -------------------------------------------------------
# -=- <check_fail2ban> -=-
# -------------------------------------------------------
#
# Description : This plugin checks if the fail2ban server is running
# and how many IPs are currently banned.
#
#
# inspired by the work of Sebastian Mueller - http://www.elchtest.eu
#
#
# Version : 0.1
# -------------------------------------------------------
# In :
# - see the How to use section
#
# Out :
# - only print on the standard output
#
# Features :
# - perfdata output
# - works with only a specific jail
#
# Fix Me/Todo :
# - too many things ;) but let me know what do you think about it
#
# ####################################################################
# ####################################################################
# GPL v2
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version 2
# of the License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
# ####################################################################
# ####################################################################
# How to use :
# ------------
#
# Just have to run the following command:
# $ ./check_fail2ban --help
#
# If you need to use this script with NRPE you just have to do the
# following steps:
#
# 1 allow your user to run the script with the sudo rights. Just add
# something like that in your /etc/sudoers (use visudo) :
# nagios ALL=(ALL) NOPASSWD: /<path-to>/check_fail2ban
#
# 2 then just add this kind of line in your NRPE config file :
# command[check_fail2ban]=/usr/bin/sudo /<path-to>/check_fail2ban
#
# 3 don't forget to restart your NRPE daemon
#
#
# /!\ be careful to let no one able to update the check_fail2ban ;)
# ------------------------------------------------------------------------------
#
# ####################################################################
# ####################################################################
# Changelog :
# -----------
#
# --------------------------------------------------------------------
# Date:12/03/2013 Version:0.1 Author:Erwan Ben Souiden
# >> creation
# ####################################################################
# ####################################################################
# Don't touch anything under this line!
# You shall not pass - Gandalf is watching you
# ####################################################################
use strict;
use warnings;
use Getopt::Long qw(:config no_ignore_case);
# Generic variables
# -----------------
my $version = '0.1';
my $author = 'Erwan Labynocle Ben Souiden';
my $a_mail = 'erwan@aleikoum.net';
my $script_name = 'check_fail2ban';
my $verbose_value = 0;
my $version_value = 0;
my $more_value = 0;
my $help_value = 0;
my $perfdata_value = 0;
my %ERRORS=('OK'=>0,'WARNING'=>1,'CRITICAL'=>2,'UNKNOWN'=>3,'DEPENDENT'=>4);
# Plugin default variables
# ------------------------
my $display = 'CHECK FAIL2BAN ACTIVITY';
my ($critical,$warning) = (2,1);
my $fail2ban_client_path = '/usr/bin/fail2ban-client';
my $fail2ban_socket = '';
my $jail_specific = '';
my $jail_name = '';
GetOptions (
'P=s' => \ $fail2ban_client_path,
'path-fail2ban_client=s' => \ $fail2ban_client_path,
'j=s' => \ $jail_specific,
'jail=s' => \ $jail_specific,
'w=i' => \ $warning,
'warning=i' => \ $warning,
'socket=s' => \ $fail2ban_socket,
'S=s' => \ $fail2ban_socket,
'c=i' => \ $critical,
'critical=i' => \ $critical,
'V' => \ $version_value,
'version' => \ $version_value,
'h' => \ $help_value,
'H' => \ $help_value,
'help' => \ $help_value,
'display=s' => \ $display,
'D=s' => \ $display,
'perfdata' => \ $perfdata_value,
'p' => \ $perfdata_value,
'v' => \ $verbose_value,
'verbose' => \ $verbose_value
);
print_usage() if ($help_value);
print_version() if ($version_value);
# Syntax check of your specified options
# --------------------------------------
print "DEBUG : fail2ban_client_path: $fail2ban_client_path\n" if ($verbose_value);
if (($fail2ban_client_path eq "")) {
print $display.'- one or more following arguments are missing: fail2ban_client_path'."\n";
exit $ERRORS{"UNKNOWN"};
}
if(! -x $fail2ban_client_path) {
print $display.' - '.$fail2ban_client_path.' is not executable by you'."\n";
exit $ERRORS{"UNKNOWN"};
}
print "DEBUG : $fail2ban_client_path exists and is executable\n" if ($verbose_value);
my $fail2ban_cmd = $fail2ban_client_path;
$fail2ban_cmd .= " -s $fail2ban_socket" if ($fail2ban_socket);
print "DEBUG : final fail2ban command: $fail2ban_cmd\n" if ($verbose_value);
print "DEBUG : warning threshold : $warning, critical threshold : $critical\n" if ($verbose_value);
if (($critical < 0) or ($warning < 0) or ($critical < $warning)) {
print $display.' - the thresholds must be integers and the critical threshold higher or equal than the warning threshold'."\n";
exit $ERRORS{"UNKNOWN"};
}
# Core script
# -----------
my ($how_many_jail,$how_many_banned,$return_print,$perf_print,$plugstate) = (0,0,"","","OK");
### Test the connection to the fail2ban server
my @command_output = `$fail2ban_cmd ping`;
my $return_code = $?;
if ($return_code) {
print $display.'CRITICAL - non-zero exit code during testing fail2ban-client ping, check if the server is running and if you have the good permissions';
exit $ERRORS{"CRITICAL"};
}
else {
print "DEBUG : it seems the connection with the fail2ban server is ok\n" if ($verbose_value);
}
### Only if you specify one jail
if ($jail_specific) {
my $current_ban_number = currently_ban("$fail2ban_cmd","$jail_specific");
if ($current_ban_number == -1) {
print $display.' - CRITICAL - impossible to retrieve info about the jail '.$jail_specific;
exit $ERRORS{"CRITICAL"};
}
else {
$how_many_banned = int($current_ban_number);
$return_print = $how_many_banned.' current banned IP(s) for the specific jail '.$jail_specific;
$perf_print .= "$current_ban_number " if ($perfdata_value);
}
}
### To analyze all the jail
else {
# Retrieve the jails list
my @jail_list = obtain_jail_list("$fail2ban_cmd");
if ($jail_list[0] eq "-1") {
print $display.' - CRITICAL - impossible to retrieve the jail list'."\n";
exit $ERRORS{"CRITICAL"};
}
foreach (@jail_list) {
$how_many_jail ++;
my $jail_name = $_;
$jail_name =~ tr/ //ds;
my $current_ban_number = currently_ban("$fail2ban_cmd","$jail_name");
if ($current_ban_number == -1) {
print "DEBUG : problem to parse the current banned IPs for jail $jail_name\n" if ($verbose_value);
}
else {
print "DEBUG : the jail $jail_name has currently $current_ban_number banned IPs\n" if ($verbose_value);
$how_many_banned += int($current_ban_number);
$perf_print .= "$jail_name.currentBannedIP=$current_ban_number " if ($perfdata_value);
}
}
$return_print = $how_many_jail.' detected jails with '.$how_many_banned.' current banned IP(s)';
}
### Final
$plugstate = "CRITICAL" if ($how_many_banned >= $critical);
$plugstate = "WARNING" if (($how_many_banned >= $warning) && ($how_many_banned < $critical));
$return_print = $display." - ".$plugstate." - ".$return_print;
$return_print .= " | $perf_print" if ($perfdata_value);
print $return_print;
exit $ERRORS{"$plugstate"};
# ####################################################################
# function 1 : display the help
# -----------------------------
sub print_usage {
print <<EOT;
$script_name version $version by $author
This plugin checks if the fail2ban server is running and how many IPs are currently banned.
You can use this plugin to monitor all the jails or just a specific jail.
Usage: /<path-to>/$script_name [-p] [-D "$display"] [-v] [-c 2] [-w 1] [-s /<path-to>/socket] [-P /usr/bin/fail2ban-client]
Options:
-h, --help
Print detailed help screen
-V, --version
Print version information
-D, --display=STRING
To modify the output display
default is "CHECK FAIL2BAN ACTIVITY"
-P, --path-fail2ban_client=STRING
Specify the path to the tw_cli binary
default value is /usr/bin/fail2ban-client
-c, --critical=INT
Specify a critical threshold
default is 2
-w, --warning=INT
Specify a warning threshold
default is 1
-s, --socket=STRING
Specify a socket path
default is unset
-p, --perfdata
If you want to activate the perfdata output
-v, --verbose
Show details for command-line debugging (Nagios may truncate the output)
Send email to $a_mail if you have questions
regarding use of this software. To submit patches or suggest improvements,
send email to $a_mail
This plugin has been created by $author
Hope you will enjoy it ;)
Remember :
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
EOT
exit $ERRORS{"UNKNOWN"};
}
# function 2 : display version information
# ----------------------------------------
sub print_version {
print <<EOT;
$script_name version $version
EOT
exit $ERRORS{"UNKNOWN"};
}
# function 3 : return the jail list
# ---------------------------------
sub obtain_jail_list {
my ($fail2ban_client_path) = @_;
my @command_output = `$fail2ban_client_path status`;
my $return_code = $?;
if ($return_code) {
return -1;
}
my @jail_list;
foreach (@command_output) {
if ($_=~/^.*Jail list:\t+(.*)/) {
print "DEBUG : jails list: $1\n" if ($verbose_value);
@jail_list = split(/,/, $1);
}
}
return @jail_list;
}
# function 4 : return how many IP are currently ban for a given jail
# ------------------------------------------------------------------
sub currently_ban {
my ($fail2ban_client_path,$jail_name) = @_;
my @command_output = `$fail2ban_client_path status $jail_name`;
my $return_code = $?;
if ($return_code) {
return -1;
}
foreach (@command_output) {
if ($_=~/^.*Currently banned:\t+(.*)/) {
my $current_count = $1;
$current_count =~ tr/ //ds;
return $current_count;
}
}
return -1;
}
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