Reduce the number of macros used for SignedExtensions

Reduce the number of macros used for SignedExtensions

Signed-off-by: Serban Iorga <serban@parity.io>

bridges/bin/runtime-common/src/lib.rs

@@ -18,6 +18,9 @@
 
 #![cfg_attr(not(feature = "std"), no_std)]
 
+use bp_runtime::FilterCall;
+use sp_runtime::transaction_validity::TransactionValidity;
+
 pub mod messages;
 pub mod messages_api;
 pub mod messages_benchmarking;
@@ -26,3 +29,167 @@ pub mod parachains_benchmarking;
 
 #[cfg(feature = "integrity-test")]
 pub mod integrity;
+
+/// A duplication of the `FilterCall` trait.
+///
+/// We need this trait in order to be able to implement it for the messages pallet,
+/// since the implementation is done outside of the pallet crate.
+pub trait BridgeRuntimeFilterCall<Call> {
+	/// Checks if a runtime call is valid.
+	fn validate(call: &Call) -> TransactionValidity;
+}
+
+impl<Call, T, I> BridgeRuntimeFilterCall<Call> for pallet_bridge_grandpa::Pallet<T, I>
+where
+	pallet_bridge_grandpa::Pallet<T, I>: FilterCall<Call>,
+{
+	fn validate(call: &Call) -> TransactionValidity {
+		<pallet_bridge_grandpa::Pallet<T, I> as FilterCall<Call>>::validate(call)
+	}
+}
+
+impl<Call, T, I> BridgeRuntimeFilterCall<Call> for pallet_bridge_parachains::Pallet<T, I>
+where
+	pallet_bridge_parachains::Pallet<T, I>: FilterCall<Call>,
+{
+	fn validate(call: &Call) -> TransactionValidity {
+		<pallet_bridge_parachains::Pallet<T, I> as FilterCall<Call>>::validate(call)
+	}
+}
+
+/// Declares a runtime-specific `BridgeRejectObsoleteHeadersAndMessages` signed extension.
+///
+/// ## Example
+///
+/// ```nocompile
+/// generate_bridge_reject_obsolete_headers_and_messages!{
+///     Call, AccountId
+///     BridgeRialtoGrandpa, BridgeWestendGrandpa,
+///     BridgeRialtoParachains
+/// }
+/// ```
+///
+/// The goal of this extension is to avoid "mining" transactions that provide outdated bridged
+/// headers and messages. Without that extension, even honest relayers may lose their funds if
+/// there are multiple relays running and submitting the same information.
+#[macro_export]
+macro_rules! generate_bridge_reject_obsolete_headers_and_messages {
+	($call:ty, $account_id:ty, $($filter_call:ty),*) => {
+		#[derive(Clone, codec::Decode, codec::Encode, Eq, PartialEq, frame_support::RuntimeDebug, scale_info::TypeInfo)]
+		pub struct BridgeRejectObsoleteHeadersAndMessages;
+		impl sp_runtime::traits::SignedExtension for BridgeRejectObsoleteHeadersAndMessages {
+			const IDENTIFIER: &'static str = "BridgeRejectObsoleteHeadersAndMessages";
+			type AccountId = $account_id;
+			type Call = $call;
+			type AdditionalSigned = ();
+			type Pre = ();
+
+			fn additional_signed(&self) -> sp_std::result::Result<
+				(),
+				sp_runtime::transaction_validity::TransactionValidityError,
+			> {
+				Ok(())
+			}
+
+			fn validate(
+				&self,
+				_who: &Self::AccountId,
+				call: &Self::Call,
+				_info: &sp_runtime::traits::DispatchInfoOf<Self::Call>,
+				_len: usize,
+			) -> sp_runtime::transaction_validity::TransactionValidity {
+				let valid = sp_runtime::transaction_validity::ValidTransaction::default();
+				$(
+					let valid = valid
+						.combine_with(<$filter_call as $crate::BridgeRuntimeFilterCall<$call>>::validate(call)?);
+				)*
+				Ok(valid)
+			}
+
+			fn pre_dispatch(
+				self,
+				who: &Self::AccountId,
+				call: &Self::Call,
+				info: &sp_runtime::traits::DispatchInfoOf<Self::Call>,
+				len: usize,
+			) -> Result<Self::Pre, sp_runtime::transaction_validity::TransactionValidityError> {
+				self.validate(who, call, info, len).map(drop)
+			}
+		}
+	};
+}
+
+#[cfg(test)]
+mod tests {
+	use crate::BridgeRuntimeFilterCall;
+	use frame_support::{assert_err, assert_ok};
+	use sp_runtime::{
+		traits::SignedExtension,
+		transaction_validity::{InvalidTransaction, TransactionValidity, ValidTransaction},
+	};
+
+	pub struct MockCall {
+		data: u32,
+	}
+
+	impl sp_runtime::traits::Dispatchable for MockCall {
+		type Origin = ();
+		type Config = ();
+		type Info = ();
+		type PostInfo = ();
+
+		fn dispatch(
+			self,
+			_origin: Self::Origin,
+		) -> sp_runtime::DispatchResultWithInfo<Self::PostInfo> {
+			unimplemented!()
+		}
+	}
+
+	struct FirstFilterCall;
+	impl BridgeRuntimeFilterCall<MockCall> for FirstFilterCall {
+		fn validate(call: &MockCall) -> TransactionValidity {
+			if call.data <= 1 {
+				return InvalidTransaction::Custom(1).into()
+			}
+
+			Ok(ValidTransaction { priority: 1, ..Default::default() })
+		}
+	}
+
+	struct SecondFilterCall;
+	impl BridgeRuntimeFilterCall<MockCall> for SecondFilterCall {
+		fn validate(call: &MockCall) -> TransactionValidity {
+			if call.data <= 2 {
+				return InvalidTransaction::Custom(2).into()
+			}
+
+			Ok(ValidTransaction { priority: 2, ..Default::default() })
+		}
+	}
+
+	#[test]
+	fn test() {
+		generate_bridge_reject_obsolete_headers_and_messages!(
+			MockCall,
+			(),
+			FirstFilterCall,
+			SecondFilterCall
+		);
+
+		assert_err!(
+			BridgeRejectObsoleteHeadersAndMessages.validate(&(), &MockCall { data: 1 }, &(), 0),
+			InvalidTransaction::Custom(1)
+		);
+
+		assert_err!(
+			BridgeRejectObsoleteHeadersAndMessages.validate(&(), &MockCall { data: 2 }, &(), 0),
+			InvalidTransaction::Custom(2)
+		);
+
+		assert_ok!(
+			BridgeRejectObsoleteHeadersAndMessages.validate(&(), &MockCall { data: 3 }, &(), 0),
+			ValidTransaction { priority: 3, ..Default::default() }
+		)
+	}
+}