Collide with an infinite plane

Hello everyone.

For the project that i'm developing I need the possibility to collide with an inifinite plane to control the transformation of an image (with finite size) even pressing outside its box (but inside the infinite plane on which it lays).

I think the best solution to this problem is to create a collider that verify a ray-plane collision (so basically a box collider 2D with less constraints and so a much easier logic) but there isn't anything like this in the engine and it doesn't seem possible to create a custom collider either.

Any ideas?