remove signed reward factor due to its attack potential

bin/node/runtime/src/lib.rs

@@ -557,7 +557,6 @@ impl pallet_election_provider_multi_phase::Config for Runtime {
 	type MinerTxPriority = MultiPhaseUnsignedPriority;
 	type SignedMaxSubmissions = SignedMaxSubmissions;
 	type SignedRewardBase = SignedRewardBase;
-	type SignedRewardFactor = (); // no score-based reward
 	type SignedRewardMax = SignedRewardBase;
 	type SignedDepositBase = SignedDepositBase;
 	type SignedDepositByte = SignedDepositByte;

frame/election-provider-multi-phase/src/lib.rs

@@ -571,9 +571,6 @@ pub mod pallet {
 		/// Base reward for a signed solution
 		#[pallet::constant]
 		type SignedRewardBase: Get<BalanceOf<Self>>;
-		/// Per-score reward for a signed solution.
-		#[pallet::constant]
-		type SignedRewardFactor: Get<Perbill>;
 		/// Maximum cap for a signed solution.
 		#[pallet::constant]
 		type SignedRewardMax: Get<Option<BalanceOf<Self>>>;

frame/election-provider-multi-phase/src/mock.rs

@@ -263,7 +263,6 @@ parameter_types! {
 	pub static SignedDepositByte: Balance = 0;
 	pub static SignedDepositWeight: Balance = 0;
 	pub static SignedRewardBase: Balance = 7;
-	pub static SignedRewardFactor: Perbill = Perbill::zero();
 	pub static SignedRewardMax: Balance = 10;
 	pub static SignedMaxWeight: Weight = BlockWeights::get().max_block;
 	pub static MinerMaxIterations: u32 = 5;
@@ -368,7 +367,6 @@ impl crate::Config for Runtime {
 	type MinerMaxLength = MinerMaxLength;
 	type MinerTxPriority = MinerTxPriority;
 	type SignedRewardBase = SignedRewardBase;
-	type SignedRewardFactor = SignedRewardFactor;
 	type SignedRewardMax = SignedRewardMax;
 	type SignedDepositBase = SignedDepositBase;
 	type SignedDepositByte = ();
@@ -485,9 +483,8 @@ impl ExtBuilder {
 		<SignedDepositWeight>::set(weight);
 		self
 	}
-	pub fn reward(self, base: u64, factor: Perbill, max: u64) -> Self {
+	pub fn reward(self, base: u64, max: u64) -> Self {
 		<SignedRewardBase>::set(base);
-		<SignedRewardFactor>::set(factor);
 		<SignedRewardMax>::set(max);
 		self
 	}

frame/election-provider-multi-phase/src/signed.rs

@@ -202,7 +202,7 @@ impl<T: Config> Pallet<T> {
 		}
 
 		// add to the designated spot. If the length is too much, remove one.
-		let reward = Self::reward_for(&solution);
+		let reward = Self::reward_for();
 		let deposit = Self::deposit_for(&solution, size);
 		let submission =
 			SignedSubmission { who: who.clone(), deposit, reward, solution };
@@ -256,9 +256,8 @@ impl<T: Config> Pallet<T> {
 
 	/// The reward for this solution, if successfully chosen as the best one at the end of the
 	/// signed phase.
-	pub fn reward_for(solution: &RawSolution<CompactOf<T>>) -> BalanceOf<T> {
-		let raw_reward = T::SignedRewardBase::get()
-			+ T::SignedRewardFactor::get() * solution.score[0].saturated_into::<BalanceOf<T>>();
+	pub fn reward_for() -> BalanceOf<T> {
+		let raw_reward = T::SignedRewardBase::get();
 
 		match T::SignedRewardMax::get() {
 			Some(cap) => raw_reward.min(cap),
@@ -357,7 +356,7 @@ mod tests {
 
 	#[test]
 	fn reward_is_capped() {
-		ExtBuilder::default().reward(5, Perbill::from_percent(25), 10).build_and_execute(|| {
+		ExtBuilder::default().reward(5, 10).build_and_execute(|| {
 			roll_to(15);
 			assert!(MultiPhase::current_phase().is_signed());
 
@@ -369,11 +368,11 @@ mod tests {
 			assert_eq!(balances(&99), (95, 5));
 
 			assert!(MultiPhase::finalize_signed_phase().0);
-			// expected reward is 5 + 10
-			assert_eq!(balances(&99), (100 + 10, 0));
+			// expected reward is 5
+			assert_eq!(balances(&99), (100 + 5, 0));
 		});
 
-		ExtBuilder::default().reward(5, Perbill::from_percent(25), 20).build_and_execute(|| {
+		ExtBuilder::default().reward(5, 20).build_and_execute(|| {
 			roll_to(15);
 			assert!(MultiPhase::current_phase().is_signed());
 
@@ -385,8 +384,8 @@ mod tests {
 			assert_eq!(balances(&99), (95, 5));
 
 			assert!(MultiPhase::finalize_signed_phase().0);
-			// expected reward is 5 + 10
-			assert_eq!(balances(&99), (100 + 15, 0));
+			// expected reward is 5
+			assert_eq!(balances(&99), (100 + 5, 0));
 		});
 	}