I am not sure where to start. My tub is leaking (hence the title

). I cut a hole in the ceiling to see the area better and I have the advantage that a closet shares a wall with the shower where the faucets are and a hole has been cut so I can see the pipes. It looks like it is coming from the cold faucet (there is a wet spot in the drywall at that point) The drain is leaking, and it looks like it is leaking behind the spout.
I am up for lots of ideas or suggestions, but my main concern is how do I fix or reseal the drain, as it looks like it is coming from the pipes on the under side.
Any thoughts anyone?
Sorry for the lengthy message
Mikey