Is Partial SSL Possible? ( multisite )

I have recently been invited to the letsencrypt SSL beta, and have now spotted a potential problem.

My main site tomjn.com is a multisite, and I have the opportunity to add certificates for tomjn.com and www.tomjn.com, but I also have other subdomains, subdomains i do not have SSL certificates for.

Is it possible to have tomjn.com served over SSL via WordPress, but only tomjn.com? Or must I force all the blogs/sites in my install to use SSL? If so, how is this best done?

Yes – entirely possible to use SSL on only 1 site in a WP network. In the past, we have done this using .htaccess to force HTTPS for all URLs of a particular site, leaving all others HTTP.

This was done using carefully written Apache URL rewrites.

The SSL used was a wildcard cert although that will not impact how the server rewrites URLs.