runtime: use babe as randomness source (#2504)

* runtime: use babe as randomness source

* runtime: fix randomness api

* bridges: fix random_seed

* parachains: use mock TestRandomness from frame_support_test

* parachains: use mock TestRandomness from frame_support_test

* runtime: update randomness source in test-runtime

* runtime: remove unused import

* parachains: add todo to audit usage of randomness api

* "Update Substrate"

Co-authored-by: parity-processbot <>

polkadot/bridges/bin/millau/runtime/src/lib.rs

@@ -458,7 +458,7 @@ impl_runtime_apis! {
 		}
 
 		fn random_seed() -> <Block as BlockT>::Hash {
-			RandomnessCollectiveFlip::random_seed()
+			RandomnessCollectiveFlip::random_seed().0
 		}
 	}
 

polkadot/bridges/bin/rialto/runtime/src/lib.rs

@@ -569,7 +569,7 @@ impl_runtime_apis! {
 		}
 
 		fn random_seed() -> <Block as BlockT>::Hash {
-			RandomnessCollectiveFlip::random_seed()
+			RandomnessCollectiveFlip::random_seed().0
 		}
 	}
 

polkadot/runtime/common/Cargo.toml

@@ -48,6 +48,7 @@ sp-trie = { git = "https://github.com/paritytech/substrate", branch = "master" }
 pallet-babe = { git = "https://github.com/paritytech/substrate", branch = "master" }
 sp-application-crypto = { git = "https://github.com/paritytech/substrate", branch = "master" }
 sp-election-providers = { git = "https://github.com/paritytech/substrate", branch = "master" }
+frame-support-test = { git = "https://github.com/paritytech/substrate", branch = "master" }
 pallet-randomness-collective-flip = { git = "https://github.com/paritytech/substrate", branch = "master" }
 pallet-staking-reward-curve = { git = "https://github.com/paritytech/substrate", branch = "master" }
 pallet-treasury = { git = "https://github.com/paritytech/substrate", branch = "master" }

polkadot/runtime/common/src/paras_registrar.rs

@@ -262,9 +262,10 @@ mod tests {
 	};
 	use frame_system::limits;
 	use frame_support::{
-		traits::{Randomness, OnInitialize, OnFinalize},
+		traits::{OnInitialize, OnFinalize},
 		assert_ok, assert_noop, parameter_types,
 	};
+	use frame_support_test::TestRandomness;
 	use keyring::Sr25519Keyring;
 	use runtime_parachains::{
 		initializer, configuration, inclusion, session_info, scheduler, dmp, ump, hrmp, shared,
@@ -511,16 +512,8 @@ mod tests {
 
 	impl session_info::Config for Test { }
 
-	pub struct TestRandomness;
-
-	impl Randomness<H256> for TestRandomness {
-		fn random(_subject: &[u8]) -> H256 {
-			Default::default()
-		}
-	}
-
 	impl initializer::Config for Test {
-		type Randomness = TestRandomness;
+		type Randomness = TestRandomness<Self>;
 	}
 
 	impl scheduler::Config for Test { }

polkadot/runtime/common/src/slots.rs

@@ -54,7 +54,7 @@ pub trait Config: frame_system::Config {
 	type LeasePeriod: Get<Self::BlockNumber>;
 
 	/// Something that provides randomness in the runtime.
-	type Randomness: Randomness<Self::Hash>;
+	type Randomness: Randomness<Self::Hash, Self::BlockNumber>;
 }
 
 /// Parachain registration API.
@@ -582,7 +582,8 @@ impl<T: Config> Module<T> {
 			let ending_period = T::EndingPeriod::get();
 			if early_end + ending_period == now {
 				// Just ended!
-				let offset = T::BlockNumber::decode(&mut T::Randomness::random_seed().as_ref())
+				let (seed, _) = T::Randomness::random_seed();
+				let offset = T::BlockNumber::decode(&mut seed.as_ref())
 					.expect("secure hashes always bigger than block numbers; qed") % ending_period;
 				let res = <Winning<T>>::get(offset).unwrap_or_default();
 				let mut i = T::BlockNumber::zero();

polkadot/runtime/kusama/src/lib.rs

@@ -818,7 +818,7 @@ parameter_types! {
 impl pallet_society::Config for Runtime {
 	type Event = Event;
 	type Currency = Balances;
-	type Randomness = RandomnessCollectiveFlip;
+	type Randomness = pallet_babe::RandomnessFromOneEpochAgo<Runtime>;
 	type CandidateDeposit = CandidateDeposit;
 	type WrongSideDeduction = WrongSideDeduction;
 	type MaxStrikes = MaxStrikes;
@@ -1140,7 +1140,7 @@ sp_api::impl_runtime_apis! {
 		}
 
 		fn random_seed() -> <Block as BlockT>::Hash {
-			RandomnessCollectiveFlip::random_seed()
+			pallet_babe::RandomnessFromOneEpochAgo::<Runtime>::random_seed().0
 		}
 	}
 

polkadot/runtime/parachains/Cargo.toml

@@ -49,6 +49,7 @@ keyring = { package = "sp-keyring", git = "https://github.com/paritytech/substra
 sp-trie = { git = "https://github.com/paritytech/substrate", branch = "master" }
 pallet-babe = { git = "https://github.com/paritytech/substrate", branch = "master" }
 sp-application-crypto = { git = "https://github.com/paritytech/substrate", branch = "master" }
+frame-support-test = { git = "https://github.com/paritytech/substrate", branch = "master" }
 pallet-randomness-collective-flip = { git = "https://github.com/paritytech/substrate", branch = "master" }
 pallet-staking-reward-curve = { git = "https://github.com/paritytech/substrate", branch = "master" }
 pallet-treasury = { git = "https://github.com/paritytech/substrate", branch = "master" }

polkadot/runtime/parachains/src/initializer.rs

@@ -81,7 +81,7 @@ pub trait Config:
 	+ hrmp::Config
 {
 	/// A randomness beacon.
-	type Randomness: Randomness<Self::Hash>;
+	type Randomness: Randomness<Self::Hash, Self::BlockNumber>;
 }
 
 decl_storage! {
@@ -181,7 +181,9 @@ impl<T: Config> Module<T> {
 
 		let random_seed = {
 			let mut buf = [0u8; 32];
-			let random_hash = T::Randomness::random(&b"paras"[..]);
+			// TODO: audit usage of randomness API
+			// https://github.com/paritytech/polkadot/issues/2601
+			let (random_hash, _) = T::Randomness::random(&b"paras"[..]);
 			let len = sp_std::cmp::min(32, random_hash.as_ref().len());
 			buf[..len].copy_from_slice(&random_hash.as_ref()[..len]);
 			buf

polkadot/runtime/parachains/src/mock.rs

@@ -22,7 +22,8 @@ use sp_runtime::traits::{
 	BlakeTwo256, IdentityLookup,
 };
 use primitives::v1::{AuthorityDiscoveryId, Balance, BlockNumber, Header, ValidatorIndex};
-use frame_support::{parameter_types, traits::Randomness as RandomnessT};
+use frame_support::parameter_types;
+use frame_support_test::TestRandomness;
 use std::cell::RefCell;
 use std::collections::HashMap;
 use crate::{
@@ -54,14 +55,6 @@ frame_support::construct_runtime!(
 	}
 );
 
-pub struct TestRandomness;
-
-impl RandomnessT<H256> for TestRandomness {
-	fn random(_subject: &[u8]) -> H256 {
-		Default::default()
-	}
-}
-
 parameter_types! {
 	pub const BlockHashCount: u32 = 250;
 	pub BlockWeights: frame_system::limits::BlockWeights =
@@ -108,7 +101,7 @@ impl pallet_balances::Config for Test {
 }
 
 impl crate::initializer::Config for Test {
-	type Randomness = TestRandomness;
+	type Randomness = TestRandomness<Self>;
 }
 
 impl crate::configuration::Config for Test { }

polkadot/runtime/polkadot/src/lib.rs

@@ -1133,7 +1133,7 @@ sp_api::impl_runtime_apis! {
 		}
 
 		fn random_seed() -> <Block as BlockT>::Hash {
-			RandomnessCollectiveFlip::random_seed()
+			pallet_babe::RandomnessFromOneEpochAgo::<Runtime>::random_seed().0
 		}
 	}
 

polkadot/runtime/rococo/src/lib.rs

@@ -39,7 +39,9 @@ use runtime_parachains::{
 	runtime_api_impl::v1 as runtime_api_impl,
 };
 use frame_support::{
-	parameter_types, construct_runtime, traits::{KeyOwnerProofSystem, Filter, EnsureOrigin}, weights::Weight,
+	construct_runtime, parameter_types,
+	traits::{EnsureOrigin, Filter, KeyOwnerProofSystem, Randomness},
+	weights::Weight,
 };
 use sp_runtime::{
 	create_runtime_str, generic, impl_opaque_keys,
@@ -587,7 +589,7 @@ impl parachains_inclusion_inherent::Config for Runtime {}
 impl parachains_scheduler::Config for Runtime {}
 
 impl parachains_initializer::Config for Runtime {
-	type Randomness = Babe;
+	type Randomness = pallet_babe::RandomnessFromOneEpochAgo<Runtime>;
 }
 
 impl paras_sudo_wrapper::Config for Runtime {}
@@ -681,7 +683,7 @@ sp_api::impl_runtime_apis! {
 		}
 
 		fn random_seed() -> <Block as BlockT>::Hash {
-			Babe::randomness().into()
+			pallet_babe::RandomnessFromOneEpochAgo::<Runtime>::random_seed().0
 		}
 	}
 

polkadot/runtime/test-runtime/src/lib.rs

@@ -470,7 +470,7 @@ impl parachains_inclusion::Config for Runtime {
 impl parachains_inclusion_inherent::Config for Runtime {}
 
 impl parachains_initializer::Config for Runtime {
-	type Randomness = Babe;
+	type Randomness = pallet_babe::RandomnessFromOneEpochAgo<Runtime>;
 }
 
 impl parachains_session_info::Config for Runtime {}
@@ -617,7 +617,7 @@ sp_api::impl_runtime_apis! {
 		}
 
 		fn random_seed() -> <Block as BlockT>::Hash {
-			RandomnessCollectiveFlip::random_seed()
+			RandomnessCollectiveFlip::random_seed().0
 		}
 	}
 

polkadot/runtime/westend/src/lib.rs

@@ -851,7 +851,7 @@ sp_api::impl_runtime_apis! {
 		}
 
 		fn random_seed() -> <Block as BlockT>::Hash {
-			RandomnessCollectiveFlip::random_seed()
+			pallet_babe::RandomnessFromOneEpochAgo::<Runtime>::random_seed().0
 		}
 	}