Where is damage calculated

[UMK]

The task is to make hediff that will affect stats such as damage resistances. As I see it is not possible because theese stats are bound to pawn def and apparel def. My next thought is to override pawn code where is damage applied to check for some hediffs and their severity. But I can't find any method which must be overriden to do so.
Do you have any elegant way to solve the problem or at least do you know the place in code where is damage calculated?