Drag is passive, therefore it does not act on gravity. Drag is a mechanical resistance to motion. If the motion in question was induced by gravity drag it can impede that motion, but has no effect on the gravity.
Drag is a force of resistance that acts in fluid motion. When there is relative motion with respect to a fluid, a drag force acts in the opposite direction to the motion. Drag depends on viscosity, compressibility of the fluid and mass of the object.
When the sum of drag force and buoyant force are equal to the downward force of gravity, the object falls with a constant velocity known as terminal velocity.
