Zabbix 4 Network Monitoring - Third Edition

Determining certificate validity

A simpler approach might be passing the threshold to the OpenSSL utilities and letting them determine whether the certificate will be good after that many seconds. A command to check whether the certificate is good for seven days would be as follows:

$ echo | openssl s_client -connect www.google.com:443 2>/dev/null | openssl x509 -checkend 604800
Certificate will not expire

That looks simple enough. If the certificate expires in the given time, the message would say Certificate will expire. The great thing is that the exit code also differs based on the expiry status, so we could return 1 when the certificate is still good and 0 when it expires.

This approach returns 1 upon success, similar to many built-in ...