Forwarded/custom domain names and SSL

Question

Assume I have a website that offers a web-based service to companies:

myservice.com

Each company has a subdomain wildcarded via mod_rewrite:

client1.myservice.com

(This is typical of many companies e.g. Wufoo)

My site has a wildcard SSL certificate for *.myservice.com, allowing clients to connect to their account securely.

As an option, clients can re-point their domain name to my website by changing the A record:

www.client1.com > client1.myservice.com

(as is possible at Tumblr)

Is it possible to still offer SSL security on the forwarding domain, so that www.client1.com (pointing to client1.myservice.com) is secured over HTTPS? Either by:

1. Extending my certificate to cover the clients' domain
2. Somehow allowing the client to upload a certificate to be hosted on my server
3. Any other method?

I've done some work with SSL certificates in the past and don't think this is possible. Can anyone prove me wrong?

Thanks, Adam

Answer 1

Your server would need to serve up a valid certificate for the domain name that the client wants to use. You would probably need to have a different IP address for each client that wanted to do this, since the last time I checked, there still wasn't great support for name based virtual hosts with SSL. If you had the client on their own IP address, their clients DNS resolving to that IP address, and you had a valid certificate (either that they provided, or you provided for them), then it should be possible.