Add basic equivocation detection pipeline schema (#2338) (#2341)

* Move finality Engine to finality_base folder

* Define SubstrateFinalityPipeline

Extract basic parts of SubstrateFinalitySyncPipeline into
SubstrateFinalityPipeline

* Add equivocation detection pipeline

* Fix comment

bridges/relays/bin-substrate/src/bridges/kusama_polkadot/kusama_headers_to_bridge_hub_polkadot.rs

@@ -21,7 +21,8 @@ use crate::cli::bridge::{CliBridgeBase, RelayToRelayHeadersCliBridge};
 use async_trait::async_trait;
 use relay_substrate_client::{AccountKeyPairOf, Client};
 use substrate_relay_helper::{
-	finality::{engine::Grandpa as GrandpaFinalityEngine, SubstrateFinalitySyncPipeline},
+	finality::SubstrateFinalitySyncPipeline,
+	finality_base::{engine::Grandpa as GrandpaFinalityEngine, SubstrateFinalityPipeline},
 	TransactionParams,
 };
 
@@ -37,11 +38,15 @@ substrate_relay_helper::generate_submit_finality_proof_call_builder!(
 );
 
 #[async_trait]
-impl SubstrateFinalitySyncPipeline for KusamaFinalityToBridgeHubPolkadot {
+impl SubstrateFinalityPipeline for KusamaFinalityToBridgeHubPolkadot {
 	type SourceChain = relay_kusama_client::Kusama;
 	type TargetChain = relay_bridge_hub_polkadot_client::BridgeHubPolkadot;
 
 	type FinalityEngine = GrandpaFinalityEngine<Self::SourceChain>;
+}
+
+#[async_trait]
+impl SubstrateFinalitySyncPipeline for KusamaFinalityToBridgeHubPolkadot {
 	type SubmitFinalityProofCallBuilder = KusamaFinalityToBridgeHubPolkadotCallBuilder;
 
 	async fn start_relay_guards(

bridges/relays/bin-substrate/src/bridges/kusama_polkadot/polkadot_headers_to_bridge_hub_kusama.rs

@@ -21,7 +21,8 @@ use crate::cli::bridge::{CliBridgeBase, RelayToRelayHeadersCliBridge};
 use async_trait::async_trait;
 use relay_substrate_client::{AccountKeyPairOf, Client};
 use substrate_relay_helper::{
-	finality::{engine::Grandpa as GrandpaFinalityEngine, SubstrateFinalitySyncPipeline},
+	finality::SubstrateFinalitySyncPipeline,
+	finality_base::{engine::Grandpa as GrandpaFinalityEngine, SubstrateFinalityPipeline},
 	TransactionParams,
 };
 
@@ -37,11 +38,15 @@ substrate_relay_helper::generate_submit_finality_proof_call_builder!(
 );
 
 #[async_trait]
-impl SubstrateFinalitySyncPipeline for PolkadotFinalityToBridgeHubKusama {
+impl SubstrateFinalityPipeline for PolkadotFinalityToBridgeHubKusama {
 	type SourceChain = relay_polkadot_client::Polkadot;
 	type TargetChain = relay_bridge_hub_kusama_client::BridgeHubKusama;
 
 	type FinalityEngine = GrandpaFinalityEngine<Self::SourceChain>;
+}
+
+#[async_trait]
+impl SubstrateFinalitySyncPipeline for PolkadotFinalityToBridgeHubKusama {
 	type SubmitFinalityProofCallBuilder = PolkadotFinalityToBridgeHubKusamaCallBuilder;
 
 	async fn start_relay_guards(

bridges/relays/bin-substrate/src/bridges/rialto_millau/millau_headers_to_rialto.rs

@@ -17,20 +17,23 @@
 //! Millau-to-Rialto headers sync entrypoint.
 
 use crate::cli::bridge::{CliBridgeBase, MessagesCliBridge, RelayToRelayHeadersCliBridge};
-use substrate_relay_helper::finality::{
+use substrate_relay_helper::{
-	engine::Grandpa as GrandpaFinalityEngine, DirectSubmitGrandpaFinalityProofCallBuilder,
+	finality::{DirectSubmitGrandpaFinalityProofCallBuilder, SubstrateFinalitySyncPipeline},
-	SubstrateFinalitySyncPipeline,
+	finality_base::{engine::Grandpa as GrandpaFinalityEngine, SubstrateFinalityPipeline},
 };
 
 /// Description of Millau -> Rialto finalized headers bridge.
 #[derive(Clone, Debug)]
 pub struct MillauFinalityToRialto;
 
-impl SubstrateFinalitySyncPipeline for MillauFinalityToRialto {
+impl SubstrateFinalityPipeline for MillauFinalityToRialto {
 	type SourceChain = relay_millau_client::Millau;
 	type TargetChain = relay_rialto_client::Rialto;
 
 	type FinalityEngine = GrandpaFinalityEngine<Self::SourceChain>;
+}
+
+impl SubstrateFinalitySyncPipeline for MillauFinalityToRialto {
 	type SubmitFinalityProofCallBuilder = DirectSubmitGrandpaFinalityProofCallBuilder<
 		Self,
 		rialto_runtime::Runtime,

bridges/relays/bin-substrate/src/bridges/rialto_millau/rialto_headers_to_millau.rs

@@ -17,20 +17,23 @@
 //! Rialto-to-Millau headers sync entrypoint.
 
 use crate::cli::bridge::{CliBridgeBase, MessagesCliBridge, RelayToRelayHeadersCliBridge};
-use substrate_relay_helper::finality::{
+use substrate_relay_helper::{
-	engine::Grandpa as GrandpaFinalityEngine, DirectSubmitGrandpaFinalityProofCallBuilder,
+	finality::{DirectSubmitGrandpaFinalityProofCallBuilder, SubstrateFinalitySyncPipeline},
-	SubstrateFinalitySyncPipeline,
+	finality_base::{engine::Grandpa as GrandpaFinalityEngine, SubstrateFinalityPipeline},
 };
 
 /// Description of Millau -> Rialto finalized headers bridge.
 #[derive(Clone, Debug)]
 pub struct RialtoFinalityToMillau;
 
-impl SubstrateFinalitySyncPipeline for RialtoFinalityToMillau {
+impl SubstrateFinalityPipeline for RialtoFinalityToMillau {
 	type SourceChain = relay_rialto_client::Rialto;
 	type TargetChain = relay_millau_client::Millau;
 
 	type FinalityEngine = GrandpaFinalityEngine<Self::SourceChain>;
+}
+
+impl SubstrateFinalitySyncPipeline for RialtoFinalityToMillau {
 	type SubmitFinalityProofCallBuilder = DirectSubmitGrandpaFinalityProofCallBuilder<
 		Self,
 		millau_runtime::Runtime,

bridges/relays/bin-substrate/src/bridges/rialto_parachain_millau/millau_headers_to_rialto_parachain.rs

@@ -35,8 +35,9 @@
 //! Millau-to-RialtoParachain headers sync entrypoint.
 
 use crate::cli::bridge::{CliBridgeBase, MessagesCliBridge, RelayToRelayHeadersCliBridge};
-use substrate_relay_helper::finality::{
+use substrate_relay_helper::{
-	engine::Grandpa as GrandpaFinalityEngine, SubstrateFinalitySyncPipeline,
+	finality::SubstrateFinalitySyncPipeline,
+	finality_base::{engine::Grandpa as GrandpaFinalityEngine, SubstrateFinalityPipeline},
 };
 
 substrate_relay_helper::generate_submit_finality_proof_call_builder!(
@@ -50,11 +51,14 @@ substrate_relay_helper::generate_submit_finality_proof_call_builder!(
 #[derive(Clone, Debug)]
 pub struct MillauFinalityToRialtoParachain;
 
-impl SubstrateFinalitySyncPipeline for MillauFinalityToRialtoParachain {
+impl SubstrateFinalityPipeline for MillauFinalityToRialtoParachain {
 	type SourceChain = relay_millau_client::Millau;
 	type TargetChain = relay_rialto_parachain_client::RialtoParachain;
 
 	type FinalityEngine = GrandpaFinalityEngine<Self::SourceChain>;
+}
+
+impl SubstrateFinalitySyncPipeline for MillauFinalityToRialtoParachain {
 	type SubmitFinalityProofCallBuilder = MillauFinalityToRialtoParachainCallBuilder;
 }
 

bridges/relays/bin-substrate/src/bridges/rococo_wococo/rococo_headers_to_bridge_hub_wococo.rs

@@ -21,7 +21,8 @@ use crate::cli::bridge::{CliBridgeBase, RelayToRelayHeadersCliBridge};
 use async_trait::async_trait;
 use relay_substrate_client::{AccountKeyPairOf, Client};
 use substrate_relay_helper::{
-	finality::{engine::Grandpa as GrandpaFinalityEngine, SubstrateFinalitySyncPipeline},
+	finality::SubstrateFinalitySyncPipeline,
+	finality_base::{engine::Grandpa as GrandpaFinalityEngine, SubstrateFinalityPipeline},
 	TransactionParams,
 };
 
@@ -37,11 +38,15 @@ substrate_relay_helper::generate_submit_finality_proof_call_builder!(
 );
 
 #[async_trait]
-impl SubstrateFinalitySyncPipeline for RococoFinalityToBridgeHubWococo {
+impl SubstrateFinalityPipeline for RococoFinalityToBridgeHubWococo {
 	type SourceChain = relay_rococo_client::Rococo;
 	type TargetChain = relay_bridge_hub_wococo_client::BridgeHubWococo;
 
 	type FinalityEngine = GrandpaFinalityEngine<Self::SourceChain>;
+}
+
+#[async_trait]
+impl SubstrateFinalitySyncPipeline for RococoFinalityToBridgeHubWococo {
 	type SubmitFinalityProofCallBuilder = RococoFinalityToBridgeHubWococoCallBuilder;
 
 	async fn start_relay_guards(

bridges/relays/bin-substrate/src/bridges/rococo_wococo/wococo_headers_to_bridge_hub_rococo.rs

@@ -21,7 +21,8 @@ use crate::cli::bridge::{CliBridgeBase, RelayToRelayHeadersCliBridge};
 use async_trait::async_trait;
 use relay_substrate_client::{AccountKeyPairOf, Client};
 use substrate_relay_helper::{
-	finality::{engine::Grandpa as GrandpaFinalityEngine, SubstrateFinalitySyncPipeline},
+	finality::SubstrateFinalitySyncPipeline,
+	finality_base::{engine::Grandpa as GrandpaFinalityEngine, SubstrateFinalityPipeline},
 	TransactionParams,
 };
 
@@ -37,11 +38,15 @@ substrate_relay_helper::generate_submit_finality_proof_call_builder!(
 );
 
 #[async_trait]
-impl SubstrateFinalitySyncPipeline for WococoFinalityToBridgeHubRococo {
+impl SubstrateFinalityPipeline for WococoFinalityToBridgeHubRococo {
 	type SourceChain = relay_wococo_client::Wococo;
 	type TargetChain = relay_bridge_hub_rococo_client::BridgeHubRococo;
 
 	type FinalityEngine = GrandpaFinalityEngine<Self::SourceChain>;
+}
+
+#[async_trait]
+impl SubstrateFinalitySyncPipeline for WococoFinalityToBridgeHubRococo {
 	type SubmitFinalityProofCallBuilder = WococoFinalityToBridgeHubRococoCallBuilder;
 
 	async fn start_relay_guards(

bridges/relays/bin-substrate/src/bridges/westend_millau/westend_headers_to_millau.rs

@@ -17,20 +17,23 @@
 //! Westend-to-Millau headers sync entrypoint.
 
 use crate::cli::bridge::{CliBridgeBase, RelayToRelayHeadersCliBridge};
-use substrate_relay_helper::finality::{
+use substrate_relay_helper::{
-	engine::Grandpa as GrandpaFinalityEngine, DirectSubmitGrandpaFinalityProofCallBuilder,
+	finality::{DirectSubmitGrandpaFinalityProofCallBuilder, SubstrateFinalitySyncPipeline},
-	SubstrateFinalitySyncPipeline,
+	finality_base::{engine::Grandpa as GrandpaFinalityEngine, SubstrateFinalityPipeline},
 };
 
 /// Description of Westend -> Millau finalized headers bridge.
 #[derive(Clone, Debug)]
 pub struct WestendFinalityToMillau;
 
-impl SubstrateFinalitySyncPipeline for WestendFinalityToMillau {
+impl SubstrateFinalityPipeline for WestendFinalityToMillau {
 	type SourceChain = relay_westend_client::Westend;
 	type TargetChain = relay_millau_client::Millau;
 
 	type FinalityEngine = GrandpaFinalityEngine<Self::SourceChain>;
+}
+
+impl SubstrateFinalitySyncPipeline for WestendFinalityToMillau {
 	type SubmitFinalityProofCallBuilder = DirectSubmitGrandpaFinalityProofCallBuilder<
 		Self,
 		millau_runtime::Runtime,

bridges/relays/bin-substrate/src/cli/init_bridge.rs

@@ -41,7 +41,7 @@ use relay_substrate_client::{AccountKeyPairOf, Chain, UnsignedTransaction};
 use sp_core::Pair;
 use structopt::StructOpt;
 use strum::{EnumString, EnumVariantNames, VariantNames};
-use substrate_relay_helper::finality::engine::{Engine, Grandpa as GrandpaFinalityEngine};
+use substrate_relay_helper::finality_base::engine::{Engine, Grandpa as GrandpaFinalityEngine};
 
 /// Initialize bridge pallet.
 #[derive(StructOpt)]

bridges/relays/client-kusama/Cargo.toml

@@ -17,3 +17,4 @@ bp-runtime = { path = "../../primitives/runtime" }
 # Substrate Dependencies
 
 sp-core = { git = "https://github.com/paritytech/substrate", branch = "master" }
+sp-session = { git = "https://github.com/paritytech/substrate", branch = "master" }

bridges/relays/client-kusama/src/lib.rs

@@ -22,6 +22,7 @@ use relay_substrate_client::{
 	Chain, ChainWithBalances, ChainWithGrandpa, RelayChain, UnderlyingChainProvider,
 };
 use sp_core::storage::StorageKey;
+use sp_session::MembershipProof;
 use std::time::Duration;
 
 /// Kusama header id.
@@ -52,6 +53,8 @@ impl Chain for Kusama {
 impl ChainWithGrandpa for Kusama {
 	const SYNCED_HEADERS_GRANDPA_INFO_METHOD: &'static str =
 		KUSAMA_SYNCED_HEADERS_GRANDPA_INFO_METHOD;
+
+	type KeyOwnerProof = MembershipProof;
 }
 
 impl ChainWithBalances for Kusama {

bridges/relays/client-millau/Cargo.toml

@@ -24,3 +24,4 @@ frame-system = { git = "https://github.com/paritytech/substrate", branch = "mast
 pallet-transaction-payment = { git = "https://github.com/paritytech/substrate", branch = "master" }
 sp-core = { git = "https://github.com/paritytech/substrate", branch = "master" }
 sp-runtime = { git = "https://github.com/paritytech/substrate", branch = "master" }
+sp-session = { git = "https://github.com/paritytech/substrate", branch = "master" }

bridges/relays/client-millau/src/lib.rs

@@ -27,6 +27,7 @@ use relay_substrate_client::{
 };
 use sp_core::{storage::StorageKey, Pair};
 use sp_runtime::{generic::SignedPayload, traits::IdentifyAccount};
+use sp_session::MembershipProof;
 use std::time::Duration;
 
 /// Millau header id.
@@ -69,6 +70,8 @@ impl Chain for Millau {
 impl ChainWithGrandpa for Millau {
 	const SYNCED_HEADERS_GRANDPA_INFO_METHOD: &'static str =
 		MILLAU_SYNCED_HEADERS_GRANDPA_INFO_METHOD;
+
+	type KeyOwnerProof = MembershipProof;
 }
 
 impl ChainWithBalances for Millau {

bridges/relays/client-polkadot/Cargo.toml

@@ -17,3 +17,4 @@ bp-runtime = { path = "../../primitives/runtime" }
 # Substrate Dependencies
 
 sp-core = { git = "https://github.com/paritytech/substrate", branch = "master" }
+sp-session = { git = "https://github.com/paritytech/substrate", branch = "master" }

bridges/relays/client-polkadot/src/lib.rs

@@ -22,6 +22,7 @@ use relay_substrate_client::{
 	Chain, ChainWithBalances, ChainWithGrandpa, RelayChain, UnderlyingChainProvider,
 };
 use sp_core::storage::StorageKey;
+use sp_session::MembershipProof;
 use std::time::Duration;
 
 /// Polkadot header id.
@@ -52,6 +53,8 @@ impl Chain for Polkadot {
 impl ChainWithGrandpa for Polkadot {
 	const SYNCED_HEADERS_GRANDPA_INFO_METHOD: &'static str =
 		POLKADOT_SYNCED_HEADERS_GRANDPA_INFO_METHOD;
+
+	type KeyOwnerProof = MembershipProof;
 }
 
 impl ChainWithBalances for Polkadot {

bridges/relays/client-rialto/Cargo.toml

@@ -24,3 +24,4 @@ frame-support = { git = "https://github.com/paritytech/substrate", branch = "mas
 pallet-transaction-payment = { git = "https://github.com/paritytech/substrate", branch = "master" }
 sp-core = { git = "https://github.com/paritytech/substrate", branch = "master" }
 sp-runtime = { git = "https://github.com/paritytech/substrate", branch = "master" }
+sp-session = { git = "https://github.com/paritytech/substrate", branch = "master" }

bridges/relays/client-rialto/src/lib.rs

@@ -27,6 +27,7 @@ use relay_substrate_client::{
 };
 use sp_core::{storage::StorageKey, Pair};
 use sp_runtime::{generic::SignedPayload, traits::IdentifyAccount};
+use sp_session::MembershipProof;
 use std::time::Duration;
 
 /// Rialto header id.
@@ -54,6 +55,8 @@ impl Chain for Rialto {
 impl ChainWithGrandpa for Rialto {
 	const SYNCED_HEADERS_GRANDPA_INFO_METHOD: &'static str =
 		RIALTO_SYNCED_HEADERS_GRANDPA_INFO_METHOD;
+
+	type KeyOwnerProof = MembershipProof;
 }
 
 impl RelayChain for Rialto {

bridges/relays/client-rococo/Cargo.toml

@@ -17,3 +17,4 @@ bp-runtime = { path = "../../primitives/runtime" }
 # Substrate Dependencies
 
 sp-core = { git = "https://github.com/paritytech/substrate", branch = "master" }
+sp-session = { git = "https://github.com/paritytech/substrate", branch = "master" }

bridges/relays/client-rococo/src/lib.rs

@@ -22,6 +22,7 @@ use relay_substrate_client::{
 	Chain, ChainWithBalances, ChainWithGrandpa, RelayChain, UnderlyingChainProvider,
 };
 use sp_core::storage::StorageKey;
+use sp_session::MembershipProof;
 use std::time::Duration;
 
 /// Rococo header id.
@@ -52,6 +53,8 @@ impl Chain for Rococo {
 impl ChainWithGrandpa for Rococo {
 	const SYNCED_HEADERS_GRANDPA_INFO_METHOD: &'static str =
 		ROCOCO_SYNCED_HEADERS_GRANDPA_INFO_METHOD;
+
+	type KeyOwnerProof = MembershipProof;
 }
 
 impl ChainWithBalances for Rococo {

bridges/relays/client-substrate/src/chain.rs

@@ -85,6 +85,9 @@ pub trait ChainWithGrandpa: Chain + UnderlyingChainWithGrandpaProvider {
 	/// Keep in mind that this method is normally provided by the other chain, which is
 	/// bridged with this chain.
 	const SYNCED_HEADERS_GRANDPA_INFO_METHOD: &'static str;
+
+	/// The type of the key owner proof used by the grandpa engine.
+	type KeyOwnerProof;
 }
 
 /// Substrate-based parachain from minimal relay-client point of view.

bridges/relays/client-westend/Cargo.toml

@@ -17,3 +17,4 @@ bp-westend = { path = "../../primitives/chain-westend" }
 # Substrate Dependencies
 
 sp-core = { git = "https://github.com/paritytech/substrate", branch = "master" }
+sp-session = { git = "https://github.com/paritytech/substrate", branch = "master" }

bridges/relays/client-westend/src/lib.rs

@@ -22,6 +22,7 @@ use relay_substrate_client::{
 	Chain, ChainWithBalances, ChainWithGrandpa, RelayChain, UnderlyingChainProvider,
 };
 use sp_core::storage::StorageKey;
+use sp_session::MembershipProof;
 use std::time::Duration;
 
 /// Westend header id.
@@ -52,6 +53,8 @@ impl Chain for Westend {
 impl ChainWithGrandpa for Westend {
 	const SYNCED_HEADERS_GRANDPA_INFO_METHOD: &'static str =
 		WESTEND_SYNCED_HEADERS_GRANDPA_INFO_METHOD;
+
+	type KeyOwnerProof = MembershipProof;
 }
 
 impl RelayChain for Westend {

bridges/relays/client-wococo/Cargo.toml

@@ -16,3 +16,4 @@ bp-wococo = { path = "../../primitives/chain-wococo" }
 
 # Substrate Dependencies
 sp-core = { git = "https://github.com/paritytech/substrate", branch = "master" }
+sp-session = { git = "https://github.com/paritytech/substrate", branch = "master" }

bridges/relays/client-wococo/src/lib.rs

@@ -22,6 +22,7 @@ use relay_substrate_client::{
 	Chain, ChainWithBalances, ChainWithGrandpa, RelayChain, UnderlyingChainProvider,
 };
 use sp_core::storage::StorageKey;
+use sp_session::MembershipProof;
 use std::time::Duration;
 
 /// Wococo header id.
@@ -52,6 +53,8 @@ impl Chain for Wococo {
 impl ChainWithGrandpa for Wococo {
 	const SYNCED_HEADERS_GRANDPA_INFO_METHOD: &'static str =
 		WOCOCO_SYNCED_HEADERS_GRANDPA_INFO_METHOD;
+
+	type KeyOwnerProof = MembershipProof;
 }
 
 impl ChainWithBalances for Wococo {

bridges/relays/lib-substrate-relay/Cargo.toml

@@ -43,6 +43,7 @@ bp-messages = { path = "../../primitives/messages" }
 frame-support = { git = "https://github.com/paritytech/substrate", branch = "master" }
 frame-system = { git = "https://github.com/paritytech/substrate", branch = "master" }
 pallet-balances = { git = "https://github.com/paritytech/substrate", branch = "master" }
+pallet-grandpa = { git = "https://github.com/paritytech/substrate", branch = "master" }
 sp-core = { git = "https://github.com/paritytech/substrate", branch = "master" }
 sp-consensus-grandpa = { git = "https://github.com/paritytech/substrate", branch = "master" }
 sp-runtime = { git = "https://github.com/paritytech/substrate", branch = "master" }

bridges/relays/lib-substrate-relay/src/equivocation/mod.rs

@@ -0,0 +1,83 @@
+// Copyright 2019-2023 Parity Technologies (UK) Ltd.
+// This file is part of Parity Bridges Common.
+
+// Parity Bridges Common is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity Bridges Common is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity Bridges Common.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Types and functions intended to ease adding of new Substrate -> Substrate
+//! equivocation detection pipelines.
+
+use crate::finality_base::SubstrateFinalityPipeline;
+use std::marker::PhantomData;
+
+use crate::finality_base::engine::Engine;
+use async_trait::async_trait;
+use bp_runtime::{BlockNumberOf, HashOf};
+use pallet_grandpa::{Call as GrandpaCall, Config as GrandpaConfig};
+use relay_substrate_client::CallOf;
+use sp_runtime::traits::{Block, Header};
+
+/// Substrate -> Substrate equivocation detection pipeline.
+#[async_trait]
+pub trait SubstrateEquivocationDetectionPipeline: SubstrateFinalityPipeline {
+	/// How the `report_equivocation` call is built ?
+	type ReportEquivocationCallBuilder: ReportEquivocationCallBuilder<Self>;
+}
+
+type EquivocationProofOf<P> = <<P as SubstrateFinalityPipeline>::FinalityEngine as Engine<
+	<P as SubstrateFinalityPipeline>::SourceChain,
+>>::EquivocationProof;
+type KeyOwnerProofOf<P> = <<P as SubstrateFinalityPipeline>::FinalityEngine as Engine<
+	<P as SubstrateFinalityPipeline>::SourceChain,
+>>::KeyOwnerProof;
+
+/// Different ways of building `report_equivocation` calls.
+pub trait ReportEquivocationCallBuilder<P: SubstrateEquivocationDetectionPipeline> {
+	/// Build a `report_equivocation` call to be executed on the source chain.
+	fn build_report_equivocation_call(
+		equivocation_proof: EquivocationProofOf<P>,
+		key_owner_proof: KeyOwnerProofOf<P>,
+	) -> CallOf<P::SourceChain>;
+}
+
+/// Building the `report_equivocation` call when having direct access to the target chain runtime.
+pub struct DirectReportGrandpaEquivocationCallBuilder<P, R> {
+	_phantom: PhantomData<(P, R)>,
+}
+
+impl<P, R> ReportEquivocationCallBuilder<P> for DirectReportGrandpaEquivocationCallBuilder<P, R>
+where
+	P: SubstrateEquivocationDetectionPipeline,
+	P::FinalityEngine: Engine<
+		P::SourceChain,
+		EquivocationProof = sp_consensus_grandpa::EquivocationProof<
+			HashOf<P::SourceChain>,
+			BlockNumberOf<P::SourceChain>,
+		>,
+	>,
+	R: frame_system::Config<Hash = HashOf<P::SourceChain>>
+		+ GrandpaConfig<KeyOwnerProof = KeyOwnerProofOf<P>>,
+	<R::Block as Block>::Header: Header<Number = BlockNumberOf<P::SourceChain>>,
+	CallOf<P::SourceChain>: From<GrandpaCall<R>>,
+{
+	fn build_report_equivocation_call(
+		equivocation_proof: EquivocationProofOf<P>,
+		key_owner_proof: KeyOwnerProofOf<P>,
+	) -> CallOf<P::SourceChain> {
+		GrandpaCall::<R>::report_equivocation {
+			equivocation_proof: Box::new(equivocation_proof),
+			key_owner_proof,
+		}
+		.into()
+	}
+}

bridges/relays/lib-substrate-relay/src/finality/initialize.rs

@@ -21,7 +21,7 @@
 //! and authorities set from source to target chain. The finality sync starts
 //! with this header.
 
-use crate::{error::Error, finality::engine::Engine};
+use crate::{error::Error, finality_base::engine::Engine};
 use sp_core::Pair;
 
 use bp_runtime::HeaderIdOf;

bridges/relays/lib-substrate-relay/src/finality/mod.rs

@@ -19,26 +19,25 @@
 
 use crate::{
 	finality::{
-		engine::Engine,
 		source::{SubstrateFinalityProof, SubstrateFinalitySource},
 		target::SubstrateFinalityTarget,
 	},
 	TransactionParams,
 };
 
+use crate::finality_base::{engine::Engine, SubstrateFinalityPipeline};
 use async_trait::async_trait;
 use bp_header_chain::justification::GrandpaJustification;
 use finality_relay::FinalitySyncPipeline;
 use pallet_bridge_grandpa::{Call as BridgeGrandpaCall, Config as BridgeGrandpaConfig};
 use relay_substrate_client::{
-	transaction_stall_timeout, AccountIdOf, AccountKeyPairOf, BlockNumberOf, CallOf, Chain,
+	transaction_stall_timeout, AccountIdOf, AccountKeyPairOf, BlockNumberOf, CallOf, Chain, Client,
-	ChainWithTransactions, Client, HashOf, HeaderOf, SyncHeader,
+	HashOf, HeaderOf, SyncHeader,
 };
 use relay_utils::metrics::MetricsParams;
 use sp_core::Pair;
 use std::{fmt::Debug, marker::PhantomData};
 
-pub mod engine;
 pub mod initialize;
 pub mod source;
 pub mod target;
@@ -51,14 +50,7 @@ pub(crate) const RECENT_FINALITY_PROOFS_LIMIT: usize = 4096;
 
 /// Substrate -> Substrate finality proofs synchronization pipeline.
 #[async_trait]
-pub trait SubstrateFinalitySyncPipeline: 'static + Clone + Debug + Send + Sync {
+pub trait SubstrateFinalitySyncPipeline: SubstrateFinalityPipeline {
-	/// Headers of this chain are submitted to the `TargetChain`.
-	type SourceChain: Chain;
-	/// Headers of the `SourceChain` are submitted to this chain.
-	type TargetChain: ChainWithTransactions;
-
-	/// Finality engine.
-	type FinalityEngine: Engine<Self::SourceChain>;
 	/// How submit finality proof call is built?
 	type SubmitFinalityProofCallBuilder: SubmitFinalityProofCallBuilder<Self>;
 
@@ -144,16 +136,16 @@ macro_rules! generate_submit_finality_proof_call_builder {
 			fn build_submit_finality_proof_call(
 				header: relay_substrate_client::SyncHeader<
 					relay_substrate_client::HeaderOf<
-						<$pipeline as $crate::finality::SubstrateFinalitySyncPipeline>::SourceChain
+						<$pipeline as $crate::finality_base::SubstrateFinalityPipeline>::SourceChain
 					>
 				>,
 				proof: bp_header_chain::justification::GrandpaJustification<
 					relay_substrate_client::HeaderOf<
-						<$pipeline as $crate::finality::SubstrateFinalitySyncPipeline>::SourceChain
+						<$pipeline as $crate::finality_base::SubstrateFinalityPipeline>::SourceChain
 					>
 				>,
 			) -> relay_substrate_client::CallOf<
-				<$pipeline as $crate::finality::SubstrateFinalitySyncPipeline>::TargetChain
+				<$pipeline as $crate::finality_base::SubstrateFinalityPipeline>::TargetChain
 			> {
 				bp_runtime::paste::item! {
 					$bridge_grandpa($submit_finality_proof {

bridges/relays/lib-substrate-relay/src/finality/source.rs

@@ -16,8 +16,12 @@
 
 //! Default generic implementation of finality source for basic Substrate client.
 
-use crate::finality::{engine::Engine, FinalitySyncPipelineAdapter, SubstrateFinalitySyncPipeline};
+use crate::{
+	finality::{FinalitySyncPipelineAdapter, SubstrateFinalitySyncPipeline},
+	finality_base::engine::Engine,
+};
 
+use crate::finality_base::SubstrateFinalityPipeline;
 use async_std::sync::{Arc, Mutex};
 use async_trait::async_trait;
 use bp_header_chain::FinalityProof;
@@ -42,10 +46,9 @@ pub type SubstrateFinalityProofsStream<P> =
 	Pin<Box<dyn Stream<Item = SubstrateFinalityProof<P>> + Send>>;
 
 /// Substrate finality proof. Specific to the used `FinalityEngine`.
-pub type SubstrateFinalityProof<P> =
+pub type SubstrateFinalityProof<P> = <<P as SubstrateFinalityPipeline>::FinalityEngine as Engine<
-	<<P as SubstrateFinalitySyncPipeline>::FinalityEngine as Engine<
+	<P as SubstrateFinalityPipeline>::SourceChain,
-		<P as SubstrateFinalitySyncPipeline>::SourceChain,
+>>::FinalityProof;
-	>>::FinalityProof;
 
 /// Substrate node as finality source.
 pub struct SubstrateFinalitySource<P: SubstrateFinalitySyncPipeline> {

bridges/relays/lib-substrate-relay/src/finality/target.rs

@@ -18,9 +18,10 @@
 
 use crate::{
 	finality::{
-		engine::Engine, source::SubstrateFinalityProof, FinalitySyncPipelineAdapter,
+		source::SubstrateFinalityProof, FinalitySyncPipelineAdapter,
 		SubmitFinalityProofCallBuilder, SubstrateFinalitySyncPipeline,
 	},
+	finality_base::engine::Engine,
 	TransactionParams,
 };
 

bridges/relays/lib-substrate-relay/src/finality_base/engine.rs

@@ -47,6 +47,10 @@ pub trait Engine<C: Chain>: Send {
 	type FinalityClient: SubstrateFinalityClient<C>;
 	/// Type of finality proofs, used by consensus engine.
 	type FinalityProof: FinalityProof<BlockNumberOf<C>> + Decode + Encode;
+	/// The type of the equivocation proof used by the consensus engine.
+	type EquivocationProof;
+	/// The type of the key owner proof used by the consensus engine.
+	type KeyOwnerProof;
 	/// Type of bridge pallet initialization data.
 	type InitializationData: std::fmt::Debug + Send + Sync + 'static;
 	/// Type of bridge pallet operating mode.
@@ -138,6 +142,8 @@ impl<C: ChainWithGrandpa> Engine<C> for Grandpa<C> {
 	type ConsensusLogReader = GrandpaConsensusLogReader<<C::Header as Header>::Number>;
 	type FinalityClient = SubstrateGrandpaFinalityClient;
 	type FinalityProof = GrandpaJustification<HeaderOf<C>>;
+	type EquivocationProof = sp_consensus_grandpa::EquivocationProof<HashOf<C>, BlockNumberOf<C>>;
+	type KeyOwnerProof = C::KeyOwnerProof;
 	type InitializationData = bp_header_chain::InitializationData<C::Header>;
 	type OperatingMode = BasicOperatingMode;
 

bridges/relays/lib-substrate-relay/src/finality_base/mod.rs

@@ -0,0 +1,35 @@
+// Copyright 2019-2023 Parity Technologies (UK) Ltd.
+// This file is part of Parity Bridges Common.
+
+// Parity Bridges Common is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity Bridges Common is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity Bridges Common.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Types and functions intended to ease adding of new Substrate -> Substrate
+//! finality pipelines.
+
+pub mod engine;
+
+use async_trait::async_trait;
+use relay_substrate_client::{Chain, ChainWithTransactions};
+use std::fmt::Debug;
+
+/// Substrate -> Substrate finality related pipeline.
+#[async_trait]
+pub trait SubstrateFinalityPipeline: 'static + Clone + Debug + Send + Sync {
+	/// Headers of this chain are submitted to the `TargetChain`.
+	type SourceChain: Chain;
+	/// Headers of the `SourceChain` are submitted to this chain.
+	type TargetChain: ChainWithTransactions;
+	/// Finality engine.
+	type FinalityEngine: engine::Engine<Self::SourceChain>;
+}

bridges/relays/lib-substrate-relay/src/lib.rs

@@ -22,8 +22,10 @@ use relay_substrate_client::{Chain, ChainWithUtilityPallet, UtilityPallet};
 
 use std::marker::PhantomData;
 
+pub mod equivocation;
 pub mod error;
 pub mod finality;
+pub mod finality_base;
 pub mod messages_lane;
 pub mod messages_metrics;
 pub mod messages_source;

bridges/relays/lib-substrate-relay/src/on_demand/headers.rs

@@ -38,11 +38,11 @@ use relay_utils::{
 
 use crate::{
 	finality::{
-		engine::Engine,
 		source::{RequiredHeaderNumberRef, SubstrateFinalitySource},
 		target::SubstrateFinalityTarget,
 		SubstrateFinalitySyncPipeline, RECENT_FINALITY_PROOFS_LIMIT,
 	},
+	finality_base::engine::Engine,
 	on_demand::OnDemandRelay,
 	TransactionParams,
 };