CentOS6 - Apache2 working but when installing / enabling SSL, server won't start because of permissions error

Solution 1:

So for anyone who doesn't understand what the answer actually is here:

This is an selinux issue. Files can have different selinux "contexts" and a file with the wrong context will be unreadable by the httpd daemon even if the regular permissions are correct. In my case, the solution was to do the following:

chcon --reference /file/with/correct/context /path/to/certificate/file

Which will copy the context from the referenced file to the certificate. In case you don't have a file you can reference, the slightly trickier way (because of having to type it out) to set the correct context is:

chcon unconfined_u:object_r:httpd_config_t:s0 /path/to/certificate/file