Various articles online have lead me to believe that a server certificate's common name must be an exact match to the root URL it is valid for. However, when I look at a bunch of the files in /etc/ssl/certs, via the command
openssl x509 -inform PEM -in <certfile.pem> -text, I see that the CN value is generally a human readable description of the site (e.g. "Google Internet Authority"), not a domain name. In fact, I can't see anything in any of the files that looks like a domain name or ip address, either in them or in the output from
openssl s_client -connect <ip>.
So, is my understanding of 'common name' incorrect? How do I retrieve the url from the certificate, for which the certificate is valid?