I'm trying to deploy a wordpress installation to Openshift but I can't refer my custom domain without a ssl certificate error when in the backend. I read a article and it says that it is expected, but I coundn't find how to get it working properly. The CNAME and domain related issues with Openshift are OK. Is there a way to manage it or is it just a thing they aren't allowing non premium users have access to?
At this time the free developer preview does not have the ability to use custom SSL on domain aliases. However, that will be part of the paid plans as described on https://www.openshift.com/developers/pricing. More updates to those plans coming very soon.
Update: Now with the Bronze Plan you can add custom SSL certificates and it is also free as long as you don't have more than 3 small gears.
First, the free plan of Openshift doesn't allow you to add your own SSL, you need to upgrade to the silver plan if you want to add a SSL certificate to your application.
Second, once you upgrade to silver plan, you can follow the instructions here to add the SSL certification to your app.