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This is a text-only version of the following page on https://raymii.org:
---
Title : Nagios plugin to check CRL expiry in minutes
Author : Remy van Elst
Date : 02-05-2013
URL : https://raymii.org/s/software/Nagios_plugin_to_check_CRL_expiry.html
Format : Markdown/HTML
---

This is a nagios plugin which you can use to check if a CRL (Certificate
Revocation List, public list with revoked certificates) is still valid. This is
based on the check_crl.py plugin from [Michele Baldessari][1]. It is modified it
so that it checks the time in minutes (for more precision) instead of days, it
has a GMT time comparison bug fixed and I've added error handling so that if the
plugin cannot get a crl file (because the webserver is down) it gives a Critical
error in nagios.

Recently I removed all Google Ads from this site due to their invasive tracking, as well as Google Analytics. Please, if you found this content useful, consider a small donation using any of the options below: <a href="https://leafnode.nl">I'm developing an open source monitoring app called Leaf Node Monitoring, for windows, linux & android. Go check it out!</a> <a href="https://github.com/sponsors/RaymiiOrg/">Consider sponsoring me on Github. It means the world to me if you show your appreciation and you'll help pay the server costs.</a> <a href="https://www.digitalocean.com/?refcode=7435ae6b8212">You can also sponsor me by getting a Digital Ocean VPS. With this referral link you'll get $100 credit for 60 days. </a>

#### Download

[Download the plugin from my github][3]
[Download the plugin from raymii.org][4]

#### Install and Usage

This guide covers the steps needed for Ubuntu 10.04/12.04 and Debian 6. It
should also work on other distro's, but make sure to modify the commands where
needed.

Make sure you have openssl, python3 and a module needed by the script installed
on the nagios host:

apt-get install python3 openssl python-m2crypto

Now place the script on the host. I've placed in _/etc/nagios/plugins/check_
crl.py_.

wget -O /etc/nagios/plugins/check_crl.py http://raymii.org/s/inc/downloads/check_crl.py

Make sure the script is executable:

chmod +x /etc/nagios/plugins/check_crl.py

Now test the script. I'm using the URL of the Comodo CA CRL file which is the CA
that signed my certificate for raymii.org.

/etc/nagios/plugins/check_crl.py -u http://crl.comodoca.com/PositiveSSLCA2.crl -w 480 -c 360
OK CRL Expires in 5109 minutes (on Thu May 9 07:30:32 2013 GMT)

/etc/nagios/plugins/check_crl.py -u http://crl.comodoca.com/PositiveSSLCA2.crl -w 5200 -c 360
WARNING CRL Expires in 5108 minutes (on Thu May 9 07:30:32 2013 GMT)

/etc/nagios/plugins/check_crl.py -u http://crl.comodoca.com/PositiveSSLCA2.crl -w 5000 -c 5300
CRITICAL CRL Expires in 5108 minutes (on Thu May 9 07:30:32 2013 GMT)

Lets add the nagios command:

define command{
command_name crl_check
command_line /etc/nagios-plugins/check_crl.py -u $ARG1$ -w $ARG2$ -c $ARG3$
}

And lets add the command to a service check:

define service {
use generic-service
host_name localhost
service_description Comodo PositiveSSL CA2 CRL
contact nagiosadmin
check_command crl_check!http://crl.comodoca.com/PositiveSSLCA2.crl!24!12
}

The above service check runs on the nagios defined host "localhost", uses the
(default) service template "generic-service" and had the contact "nagiosadmin".
As you can see, the URL maps to $ARG1$, the warning hours to $ARG2$ and the
critical hours to $ARG3$. This means that if the field _"Next Update:"_ is less
then 8 hours in the future you get a warning and if it is less then 6 hours you
get a critical.

#### Changelog

03-04-2013: - Changed time to minutes for more precision - Fixed timezone bug by
comparing GMT with GMT

06-11-2012: - Changed checking interval from dates to hours - Added error
catching if a crl file cannot be retrieved.

[1]: http://acksyn.org/?p=690
[2]: https://www.digitalocean.com/?refcode=7435ae6b8212
[3]: https://github.com/RaymiiOrg/nagios
[4]: https://raymii.org/s/inc/downloads/check_crl.py

---

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