We are making a web-based application that will be installed in intranets as a virtual machine image (we send the user a CD with the virtual machine image, user runs it in a VMWare/VirtualBox/...).
We want to protect the application frontend by using HTTPS. We thought about getting a single certificate (issued by some known CA) for domain
app.ourdomain.com and installing it on all instances, but that obviously means that one could take apart an installation, take out the private key and make a man in the middle attack on some other installation (provided he had access to its network). While this is an unlikely scenario, we would still like to avoid taking the risk.
Is it possible to get a wildcard certificate that would allow us to sign our own subdomains, so that we could issue certificates
app2.ourdomain.com,... and they would be accepted by users browsers? (we have no control over users' browsers) If yes, how are these certificates called?
If not, is there some other way we can protect the users from one another?
UPDATE: I have since found a similar question on serverfault so it seems it is technically possible, but "you hardly will find any CA willing to provide you with such a certificate". I would still love to know if there is a CA that issues such certificates?