Comment 3 for bug 1639940

Regarding the security implications of exposing the direct image URL via endpoints, this is documented in the Ceph Openstack integration docs.
http://docs.ceph.com/docs/jewel/rbd/rbd-openstack/#any-openstack-version

"Note that this exposes the back end location via Glance’s API, so the endpoint with this option enabled should not be publicly accessible."

What I do to mitigate this concern is run two sets of glance containers, both tied to the same RBD cluster/database behind my load balancers. The public endpoints route to a set of glance containers that does not have show_image_direct_url enabled. The "backend" containers bind to the internal LB endpoint and have show_image_direct_url enabled to allow for ceph rbd copy on write.