Objective: Get the SSL certificate expiration date of a website from the command line.
To decode SSL certificates from the command line, we can make use of the
s_client sub command found under the
openssl tool. The general syntax of the command is:
echo | openssl s_client -connect host:port 2>/dev/null | openssl x509 -dates -noout
port parameters have to be modified accordingly, based on the server that you want to check and the port that the web services are running on. To check the SSL certificate expiration dates for
$ echo | openssl s_client -connect google.com:443 2>/dev/null | openssl x509 -dates -noout notBefore=Dec 15 13:48:27 2016 GMT notAfter=Mar 9 13:35:00 2017 GMT
The above output indicates that the SSL certificate for
google.com is valid from
15-Dec-2016 13:48:27 GMT till
9-Mar-2017 13:35:00 GMT. The SSL certificate will expire on 9-Mar-2017 and will have to be replaced by then.