Can I use a single (non-wildcard) SSL cert on multiple hostnames of the same domain?

If I have test.example.com and prod.example.com (two hostnames, but same domain name) can I use the same SSL cert on both machines?

In the past when I tried using a prod.example.com cert on test.example.com it resulted in browser warnings for host-mismatch, which led me to believe that I needed a wildcard (or else multiple distinct certs). (Perhaps my mistake was in generating the CSR for prod.example.com rather than simply example.com ?)

But the various SSL vendors' websites mention needing a wildcard cert for subdomains, which is not at all what I am using.

Is their language simply incorrect? (My cynical side wonders if this helps vendors sell more expensive certs...)

Solution 1:

You would need a certificate that supports the Subject Alternate Name field and you would have test.example.com in there for it to work in the example that you described.

A cert for example.com will not magically work for *.example.com like you are describing unless it is a wildcard cert, which you explicitly say that you do not have. The SAN field listing each sub-domain is what you need if you're not going to get a wildcard.

Solution 2:

Is their language simply incorrect?

No, yours is.

If I have test.example.com and prod.example.com (two hostnames, but same domain name)

These are not the same domain name. They are both separate domain names that happen to be subdomains of example.com.

A domain name is any name that exists at any level in the DNS, not just the ones you get from your domain registrar.

An SSL certificate can only cover:

1. An exact domain name
2. As above, but with additional "Subject Alternate Names", or
3. every sub-domain, i.e a wildcard cert.

Hence you can't just get a cert for example.com and have it automatically cover the subdomains too.