Wall walking

I am trying to create a game where a character needs to be able to walk up walls and even on the ceilings. I also have another character that can fly and land on walls and ceilings. Does anyone know where I could find either a tutorial on the programming of the physics for this or that is willing to offer help in the java script programming?

A simple solution, could be to check if you could manipulate the gravity “vector” within unity itself. Thus being able to use some of the already available scripts.