Add validator to dispatch precompile (polkadot-evm#1042)

* Add dispatch filter

* Fix clippy

* Fix review

frame/evm/precompile/dispatch/src/lib.rs

@@ -42,15 +42,16 @@ use pallet_evm::{AddressMapping, GasWeightMapping};
 // `DecodeLimit` specifies the max depth a call can use when decoding, as unbounded depth
 // can be used to overflow the stack.
 // Default value is 8, which is the same as in XCM call decoding.
-pub struct Dispatch<T, DecodeLimit = ConstU32<8>> {
-	_marker: PhantomData<(T, DecodeLimit)>,
+pub struct Dispatch<T, DispatchValidator = (), DecodeLimit = ConstU32<8>> {
+	_marker: PhantomData<(T, DispatchValidator, DecodeLimit)>,
 }
 
-impl<T, DecodeLimit> Precompile for Dispatch<T, DecodeLimit>
+impl<T, DispatchValidator, DecodeLimit> Precompile for Dispatch<T, DispatchValidator, DecodeLimit>
 where
 	T: pallet_evm::Config,
 	T::RuntimeCall: Dispatchable<PostInfo = PostDispatchInfo> + GetDispatchInfo + Decode,
 	<T::RuntimeCall as Dispatchable>::RuntimeOrigin: From<Option<T::AccountId>>,
+	DispatchValidator: DispatchValidateT<T>,
 	DecodeLimit: Get<u32>,
 {
 	fn execute(handle: &mut impl PrecompileHandle) -> PrecompileResult {
@@ -64,13 +65,6 @@ where
 			})?;
 		let info = call.get_dispatch_info();
 
-		let valid_call = info.pays_fee == Pays::Yes && info.class == DispatchClass::Normal;
-		if !valid_call {
-			return Err(PrecompileFailure::Error {
-				exit_status: ExitError::Other("invalid call".into()),
-			});
-		}
-
 		if let Some(gas) = target_gas {
 			let valid_weight =
 				info.weight.ref_time() <= T::GasWeightMapping::gas_to_weight(gas, false).ref_time();
@@ -83,13 +77,19 @@ where
 
 		let origin = T::AddressMapping::into_account_id(context.caller);
 
+		if let Some(err) = DispatchValidator::validate_before_dispatch(&origin, &call) {
+			return Err(err);
+		}
+
 		match call.dispatch(Some(origin).into()) {
 			Ok(post_info) => {
-				let cost = T::GasWeightMapping::weight_to_gas(
-					post_info.actual_weight.unwrap_or(info.weight),
-				);
+				if post_info.pays_fee(&info) == Pays::Yes {
+					let cost = T::GasWeightMapping::weight_to_gas(
+						post_info.actual_weight.unwrap_or(info.weight),
+					);
 
-				handle.record_cost(cost)?;
+					handle.record_cost(cost)?;
+				}
 
 				Ok(PrecompileOutput {
 					exit_status: ExitSucceed::Stopped,
@@ -104,3 +104,31 @@ where
 		}
 	}
 }
+
+/// Dispatch validation trait.
+pub trait DispatchValidateT<T: pallet_evm::Config> {
+	fn validate_before_dispatch(
+		origin: &T::AccountId,
+		call: &T::RuntimeCall,
+	) -> Option<PrecompileFailure>;
+}
+
+/// The default implementation of `DispatchValidateT`.
+impl<T> DispatchValidateT<T> for ()
+where
+	T: pallet_evm::Config,
+	T::RuntimeCall: GetDispatchInfo,
+{
+	fn validate_before_dispatch(
+		_origin: &T::AccountId,
+		call: &T::RuntimeCall,
+	) -> Option<PrecompileFailure> {
+		let info = call.get_dispatch_info();
+		if !(info.pays_fee == Pays::Yes && info.class == DispatchClass::Normal) {
+			return Some(PrecompileFailure::Error {
+				exit_status: ExitError::Other("invalid call".into()),
+			});
+		}
+		None
+	}
+}

primitives/account/src/lib.rs

@@ -67,7 +67,7 @@ impl std::fmt::Display for AccountId20 {
 
 					acc
 				});
-		write!(f, "{}", checksum)
+		write!(f, "{checksum}")
 	}
 }