beacon: process randao

beacon/src/executive/transition/per_block/mod.rs

 mod header;
+mod randao;

beacon/src/executive/transition/per_block/randao.rs

+use crate::primitives::*;
+use crate::types::*;
+use crate::{Config, BeaconState, Error};
+use bm_le::tree_root;
+
+impl<C: Config> BeaconState<C> {
+	/// Process randao information given in a block.
+	pub fn process_randao(&mut self, body: &BeaconBlockBody<C>) -> Result<(), Error> {
+		let proposer = &self.validators[
+			self.beacon_proposer_index()? as usize
+		];
+
+		if !C::bls_verify(
+			&proposer.pubkey,
+			&tree_root::<C::Digest, _>(&self.current_epoch()),
+			&body.randao_reveal,
+			self.domain(C::domain_randao(), None)
+		) {
+			return Err(Error::RandaoSignatureInvalid)
+		}
+
+		let current_epoch = self.current_epoch();
+		self.randao_mixes[
+			(current_epoch % C::epochs_per_historical_vector()) as usize
+		] = self.randao_mix(current_epoch) ^
+			C::hash(&[&body.randao_reveal[..]]);
+
+		Ok(())
+	}
+}