Monday, November 24, 2014

Monitoring HTTPS (and other SSL) certificates with Zabbix

In this year, we had a lot of security issues with SSL certificates, mostly in HTTPS, but also in other protocols using TLS/SSL.

The most serious concern is the poodle attack on SSLv3 connections.
The recommended setting is to disable SSLv3 in all your services.

The other issue is, that SHA1 is deprecated for HTTPS certificates, especially when the certificate expiration date is after 1. january 2017.
Google (and other web browser software developper) will gradually tell you, that
the certificates are not thrustworthy or even invalid.

You will find a lot of links in the web how to secury your server systems against poodle, and also on how to renew your certificates, so they don't use SHA1 anymore.

But how to make sure all your systems are correctly configured and the certificates in a valid range?
With Zabbix this is very simple, I have made a Zabbix template available, so you can integrate monitoring and alerting of SSL certificates in Zabbix.

You can download the Zabbix Template(s) and the ssl/tls check script from this link.
  1. Place the ssltls.check script in your zabbix external script folder and make it executable.
  2. Then import the template(s) and assign them to your server(s).
The HTTPS Template checks on Port 443 for the SSL things we described above. In addition it also checks the expirationdate and hash of your certificate.

The FTP template checks if TLS is activated on your FTP server and then checks for correct ssl working. It does no hash and 2017 expiration checks, since this is only relevant for webbrowsers.
The POP_IMAP_SMTP template checks if TLS is activae on POP,IMAP,SMTP,SMTP Submission and the POP3/IMAPS and SMTP services. It does no hash and 2017 expiration checks, since this is only relevant for webbrowsers.

The ssl check script is based on a version from Simon Kowallik, I did extend it to
also be able to check for the digest algorithm and detect the poodle vulnerability.

Link for SSLv3 disabling on various server products

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