Illegal drugs are no more legal on site than off, and the police are patrolling.
If you are going to experiment with drugs, this really isn't the place to start. If you react badly, the crowds and the sheer size of the Festival can be very frightening indeed. Drunkenness is at the very least antisocial. Prolonged exposure to high volume noise can cause severe hearing damage. It has taken several million years to evolve your precious body, so please look after it.