Operations | Monitoring | ITSM | DevOps | Cloud

Does a TLS Certificate Need a Common Name?

Technically: no. In practice: maybe. Lot’s of teams are experimenting with shorter duration certificates from Let’s Encrypt to get ready for the 47-day mandate. Those certs come with a big gotcha: no more Common Name. A modern browser is perfectly happy with a TLS certificate that has no Common Name. Your VPN or mail server might have other opinions. And since those are probably things you’d like to keep working, there’s a little more nuance to the answer.

CT alerts: know when someone gets a certificate for your domains

A couple days ago, I told you how a spammer got a certificate for dev-docs.trackjs.com, and that we only found out because Google emailed us. Google knew because the spammer claimed the hostname in Search Console. An attacker running a phishing page wouldn’t have done that, but they would still need a certificate. Every publicly trusted certificate gets written to a public log, and we track that log in our database. We just weren’t watching it. Now we are, and you can too.

Certificate monitoring for your intranet hosts

Certificate monitoring from the cloud only sees what the internet sees, like your public websites. But the vCenter console, the internal API, the switch management page, or that thing on db01.corp.internal are invisible to it. Those certificates expire just like public ones. They just don’t warn anybody first. This gap became very clear when we shipped Private PKI. Now CertKit can issue certificates for internal names and IP addresses, deploy them, and install the root into your trust stores.