Add equivocation detector crate and implement clients (#2348) (#2353)

* Split FinalitySyncPipeline and SourceClient

* Move some logic to finality_base

* Add empty equivocation detection clients

* Add equivocation reporting logic to the source client

* Use convenience trait for SubstrateFinalitySyncPipeline

* Define JustificationVerificationContext for GRANDPA

* Equivocation source client: finality_verification_context()

* Equivocation source client: synced_headers_finality_info()

* reuse HeaderFinalityInfo

* Define EquivocationsFinder

* Fix spellcheck

* Address review comments

* Avoid equivocations lookup errors

bridges/primitives/header-chain/src/justification/mod.rs

@@ -23,10 +23,11 @@ mod verification;
 
 use crate::ChainWithGrandpa;
 pub use verification::{
-	equivocation::{EquivocationsCollector, Error as EquivocationsCollectorError},
+	equivocation::{EquivocationsCollector, GrandpaEquivocationsFinder},
 	optimizer::verify_and_optimize_justification,
 	strict::verify_justification,
-	AncestryChain, Error as JustificationVerificationError, PrecommitError,
+	AncestryChain, Error as JustificationVerificationError, JustificationVerificationContext,
+	PrecommitError,
 };
 
 use bp_runtime::{BlockNumberOf, Chain, HashOf, HeaderId};

bridges/primitives/header-chain/src/justification/verification/equivocation.rs

@@ -16,33 +16,26 @@
 
 //! Logic for extracting equivocations from multiple GRANDPA Finality Proofs.
 
-use crate::justification::{
-	verification::{
-		Error as JustificationVerificationError, JustificationVerifier, PrecommitError,
-		SignedPrecommit,
+use crate::{
+	justification::{
+		verification::{
+			Error as JustificationVerificationError, IterationFlow,
+			JustificationVerificationContext, JustificationVerifier, PrecommitError,
+			SignedPrecommit,
+		},
+		GrandpaJustification,
 	},
-	GrandpaJustification,
+	ChainWithGrandpa, FindEquivocations,
 };
 
-use crate::justification::verification::IterationFlow;
-use finality_grandpa::voter_set::VoterSet;
-use frame_support::RuntimeDebug;
-use sp_consensus_grandpa::{AuthorityId, AuthoritySignature, EquivocationProof, Precommit, SetId};
+use bp_runtime::{BlockNumberOf, HashOf, HeaderOf};
+use sp_consensus_grandpa::{AuthorityId, AuthoritySignature, EquivocationProof, Precommit};
 use sp_runtime::traits::Header as HeaderT;
 use sp_std::{
 	collections::{btree_map::BTreeMap, btree_set::BTreeSet},
 	prelude::*,
 };
 
-/// Justification verification error.
-#[derive(Eq, RuntimeDebug, PartialEq)]
-pub enum Error {
-	/// Justification is targeting unexpected round.
-	InvalidRound,
-	/// Justification verification error.
-	JustificationVerification(JustificationVerificationError),
-}
-
 enum AuthorityVotes<Header: HeaderT> {
 	SingleVote(SignedPrecommit<Header>),
 	Equivocation(
@@ -53,8 +46,7 @@ enum AuthorityVotes<Header: HeaderT> {
 /// Structure that can extract equivocations from multiple GRANDPA justifications.
 pub struct EquivocationsCollector<'a, Header: HeaderT> {
 	round: u64,
-	authorities_set_id: SetId,
-	authorities_set: &'a VoterSet<AuthorityId>,
+	context: &'a JustificationVerificationContext,
 
 	votes: BTreeMap<AuthorityId, AuthorityVotes<Header>>,
 }
@@ -62,38 +54,34 @@ pub struct EquivocationsCollector<'a, Header: HeaderT> {
 impl<'a, Header: HeaderT> EquivocationsCollector<'a, Header> {
 	/// Create a new instance of `EquivocationsCollector`.
 	pub fn new(
-		authorities_set_id: SetId,
-		authorities_set: &'a VoterSet<AuthorityId>,
+		context: &'a JustificationVerificationContext,
 		base_justification: &GrandpaJustification<Header>,
-	) -> Result<Self, Error> {
-		let mut checker = Self {
-			round: base_justification.round,
-			authorities_set_id,
-			authorities_set,
-			votes: BTreeMap::new(),
-		};
+	) -> Result<Self, JustificationVerificationError> {
+		let mut checker = Self { round: base_justification.round, context, votes: BTreeMap::new() };
+
+		checker.verify_justification(
+			(base_justification.commit.target_hash, base_justification.commit.target_number),
+			checker.context,
+			base_justification,
+		)?;
 
-		checker.parse_justification(base_justification)?;
 		Ok(checker)
 	}
 
-	/// Parse an additional justification for equivocations.
-	pub fn parse_justification(
-		&mut self,
-		justification: &GrandpaJustification<Header>,
-	) -> Result<(), Error> {
-		// The justification should target the same round as the base justification.
-		if self.round != justification.round {
-			return Err(Error::InvalidRound)
+	/// Parse additional justifications for equivocations.
+	pub fn parse_justifications(&mut self, justifications: &[GrandpaJustification<Header>]) {
+		let round = self.round;
+		for justification in
+			justifications.iter().filter(|justification| round == justification.round)
+		{
+			// We ignore the Errors received here since we don't care if the proofs are valid.
+			// We only care about collecting equivocations.
+			let _ = self.verify_justification(
+				(justification.commit.target_hash, justification.commit.target_number),
+				self.context,
+				justification,
+			);
 		}
-
-		self.verify_justification(
-			(justification.commit.target_hash, justification.commit.target_number),
-			self.authorities_set_id,
-			self.authorities_set,
-			justification,
-		)
-		.map_err(Error::JustificationVerification)
 	}
 
 	/// Extract the equivocation proofs that have been collected.
@@ -102,7 +90,7 @@ impl<'a, Header: HeaderT> EquivocationsCollector<'a, Header> {
 		for (_authority, vote) in self.votes {
 			if let AuthorityVotes::Equivocation(equivocation) = vote {
 				equivocations.push(EquivocationProof::new(
-					self.authorities_set_id,
+					self.context.authority_set_id,
 					sp_consensus_grandpa::Equivocation::Precommit(equivocation),
 				));
 			}
@@ -177,3 +165,29 @@ impl<'a, Header: HeaderT> JustificationVerifier<Header> for EquivocationsCollect
 		Ok(())
 	}
 }
+
+/// Helper struct for finding equivocations in GRANDPA proofs.
+pub struct GrandpaEquivocationsFinder<C>(sp_std::marker::PhantomData<C>);
+
+impl<C: ChainWithGrandpa>
+	FindEquivocations<
+		GrandpaJustification<HeaderOf<C>>,
+		JustificationVerificationContext,
+		EquivocationProof<HashOf<C>, BlockNumberOf<C>>,
+	> for GrandpaEquivocationsFinder<C>
+{
+	type Error = JustificationVerificationError;
+
+	fn find_equivocations(
+		verification_context: &JustificationVerificationContext,
+		synced_proof: &GrandpaJustification<HeaderOf<C>>,
+		source_proofs: &[GrandpaJustification<HeaderOf<C>>],
+	) -> Result<Vec<EquivocationProof<HashOf<C>, BlockNumberOf<C>>>, Self::Error> {
+		let mut equivocations_collector =
+			EquivocationsCollector::new(verification_context, synced_proof)?;
+
+		equivocations_collector.parse_justifications(source_proofs);
+
+		Ok(equivocations_collector.into_equivocation_proofs())
+	}
+}

bridges/primitives/header-chain/src/justification/verification/mod.rs

@@ -20,7 +20,7 @@ pub mod equivocation;
 pub mod optimizer;
 pub mod strict;
 
-use crate::justification::GrandpaJustification;
+use crate::{justification::GrandpaJustification, AuthoritySet};
 
 use bp_runtime::HeaderId;
 use finality_grandpa::voter_set::VoterSet;
@@ -114,6 +114,8 @@ impl<Header: HeaderT> AncestryChain<Header> {
 /// Justification verification error.
 #[derive(Eq, RuntimeDebug, PartialEq)]
 pub enum Error {
+	/// Could not convert `AuthorityList` to `VoterSet`.
+	InvalidAuthorityList,
 	/// Justification is finalizing unexpected header.
 	InvalidJustificationTarget,
 	/// Error validating a precommit
@@ -141,6 +143,24 @@ pub enum PrecommitError {
 	UnrelatedAncestryVote,
 }
 
+/// The context needed for validating GRANDPA finality proofs.
+pub struct JustificationVerificationContext {
+	/// The authority set used to verify the justification.
+	pub voter_set: VoterSet<AuthorityId>,
+	/// The ID of the authority set used to verify the justification.
+	pub authority_set_id: SetId,
+}
+
+impl TryFrom<AuthoritySet> for JustificationVerificationContext {
+	type Error = Error;
+
+	fn try_from(authority_set: AuthoritySet) -> Result<Self, Self::Error> {
+		let voter_set =
+			VoterSet::new(authority_set.authorities).ok_or(Error::InvalidAuthorityList)?;
+		Ok(JustificationVerificationContext { voter_set, authority_set_id: authority_set.set_id })
+	}
+}
+
 enum IterationFlow {
 	Run,
 	Skip,
@@ -185,8 +205,7 @@ trait JustificationVerifier<Header: HeaderT> {
 	fn verify_justification(
 		&mut self,
 		finalized_target: (Header::Hash, Header::Number),
-		authorities_set_id: SetId,
-		authorities_set: &VoterSet<AuthorityId>,
+		context: &JustificationVerificationContext,
 		justification: &GrandpaJustification<Header>,
 	) -> Result<(), Error> {
 		// ensure that it is justification for the expected header
@@ -196,7 +215,7 @@ trait JustificationVerifier<Header: HeaderT> {
 			return Err(Error::InvalidJustificationTarget)
 		}
 
-		let threshold = authorities_set.threshold().get();
+		let threshold = context.voter_set.threshold().get();
 		let mut chain = AncestryChain::new(justification);
 		let mut signature_buffer = Vec::new();
 		let mut cumulative_weight = 0u64;
@@ -211,7 +230,7 @@ trait JustificationVerifier<Header: HeaderT> {
 			}
 
 			// authority must be in the set
-			let authority_info = match authorities_set.get(&signed.id) {
+			let authority_info = match context.voter_set.get(&signed.id) {
 				Some(authority_info) => {
 					// The implementer may want to do extra checks here.
 					// For example to see if the authority has already voted in the same round.
@@ -248,7 +267,7 @@ trait JustificationVerifier<Header: HeaderT> {
 				&signed.id,
 				&signed.signature,
 				justification.round,
-				authorities_set_id,
+				context.authority_set_id,
 				&mut signature_buffer,
 			) {
 				self.process_invalid_signature_vote(precommit_idx).map_err(Error::Precommit)?;

bridges/primitives/header-chain/src/justification/verification/optimizer.rs

@@ -21,9 +21,10 @@ use crate::justification::{
 	GrandpaJustification,
 };
 
-use crate::justification::verification::{IterationFlow, SignedPrecommit};
-use finality_grandpa::voter_set::VoterSet;
-use sp_consensus_grandpa::{AuthorityId, SetId};
+use crate::justification::verification::{
+	IterationFlow, JustificationVerificationContext, SignedPrecommit,
+};
+use sp_consensus_grandpa::AuthorityId;
 use sp_runtime::traits::Header as HeaderT;
 use sp_std::{collections::btree_set::BTreeSet, prelude::*};
 
@@ -111,8 +112,7 @@ impl<Header: HeaderT> JustificationVerifier<Header> for JustificationOptimizer<H
 /// Verify and optimize given justification by removing unknown and duplicate votes.
 pub fn verify_and_optimize_justification<Header: HeaderT>(
 	finalized_target: (Header::Hash, Header::Number),
-	authorities_set_id: SetId,
-	authorities_set: &VoterSet<AuthorityId>,
+	context: &JustificationVerificationContext,
 	justification: &mut GrandpaJustification<Header>,
 ) -> Result<(), Error> {
 	let mut optimizer = JustificationOptimizer {
@@ -120,12 +120,7 @@ pub fn verify_and_optimize_justification<Header: HeaderT>(
 		extra_precommits: vec![],
 		redundant_votes_ancestries: Default::default(),
 	};
-	optimizer.verify_justification(
-		finalized_target,
-		authorities_set_id,
-		authorities_set,
-		justification,
-	)?;
+	optimizer.verify_justification(finalized_target, context, justification)?;
 	optimizer.optimize(justification);
 
 	Ok(())

bridges/primitives/header-chain/src/justification/verification/strict.rs

@@ -21,9 +21,10 @@ use crate::justification::{
 	GrandpaJustification,
 };
 
-use crate::justification::verification::{IterationFlow, SignedPrecommit};
-use finality_grandpa::voter_set::VoterSet;
-use sp_consensus_grandpa::{AuthorityId, SetId};
+use crate::justification::verification::{
+	IterationFlow, JustificationVerificationContext, SignedPrecommit,
+};
+use sp_consensus_grandpa::AuthorityId;
 use sp_runtime::traits::Header as HeaderT;
 use sp_std::collections::btree_set::BTreeSet;
 
@@ -92,15 +93,9 @@ impl<Header: HeaderT> JustificationVerifier<Header> for StrictJustificationVerif
 /// Verify that justification, that is generated by given authority set, finalizes given header.
 pub fn verify_justification<Header: HeaderT>(
 	finalized_target: (Header::Hash, Header::Number),
-	authorities_set_id: SetId,
-	authorities_set: &VoterSet<AuthorityId>,
+	context: &JustificationVerificationContext,
 	justification: &GrandpaJustification<Header>,
 ) -> Result<(), Error> {
 	let mut verifier = StrictJustificationVerifier { votes: BTreeSet::new() };
-	verifier.verify_justification(
-		finalized_target,
-		authorities_set_id,
-		authorities_set,
-		justification,
-	)
+	verifier.verify_justification(finalized_target, context, justification)
 }

bridges/primitives/header-chain/src/lib.rs

@@ -19,6 +19,9 @@
 
 #![cfg_attr(not(feature = "std"), no_std)]
 
+use crate::justification::{
+	GrandpaJustification, JustificationVerificationContext, JustificationVerificationError,
+};
 use bp_runtime::{
 	BasicOperatingMode, Chain, HashOf, HasherOf, HeaderOf, RawStorageProof, StorageProofChecker,
 	StorageProofError, UnderlyingChainProvider,
@@ -30,7 +33,7 @@ use scale_info::TypeInfo;
 use serde::{Deserialize, Serialize};
 use sp_consensus_grandpa::{AuthorityList, ConsensusLog, SetId, GRANDPA_ENGINE_ID};
 use sp_runtime::{traits::Header as HeaderT, Digest, RuntimeDebug};
-use sp_std::boxed::Box;
+use sp_std::{boxed::Box, vec::Vec};
 
 pub mod justification;
 pub mod storage_keys;
@@ -172,13 +175,48 @@ impl<Number: Codec> ConsensusLogReader for GrandpaConsensusLogReader<Number> {
 	}
 }
 
-/// The Grandpa-related info associated to a header.
+/// The finality-related info associated to a header.
 #[derive(Encode, Decode, Debug, PartialEq, Clone, TypeInfo)]
-pub struct HeaderGrandpaInfo<Header: HeaderT> {
-	/// The header justification
-	pub justification: justification::GrandpaJustification<Header>,
-	/// The authority set introduced by the header.
-	pub authority_set: Option<AuthoritySet>,
+pub struct HeaderFinalityInfo<FinalityProof, FinalityVerificationContext> {
+	/// The header finality proof.
+	pub finality_proof: FinalityProof,
+	/// The new verification context introduced by the header.
+	pub new_verification_context: Option<FinalityVerificationContext>,
+}
+
+/// Grandpa-related info associated to a header. This info can be saved to events.
+pub type StoredHeaderGrandpaInfo<Header> =
+	HeaderFinalityInfo<GrandpaJustification<Header>, AuthoritySet>;
+
+/// Processed Grandpa-related info associated to a header.
+pub type HeaderGrandpaInfo<Header> =
+	HeaderFinalityInfo<GrandpaJustification<Header>, JustificationVerificationContext>;
+
+impl<Header: HeaderT> TryFrom<StoredHeaderGrandpaInfo<Header>> for HeaderGrandpaInfo<Header> {
+	type Error = JustificationVerificationError;
+
+	fn try_from(grandpa_info: StoredHeaderGrandpaInfo<Header>) -> Result<Self, Self::Error> {
+		Ok(Self {
+			finality_proof: grandpa_info.finality_proof,
+			new_verification_context: match grandpa_info.new_verification_context {
+				Some(authority_set) => Some(authority_set.try_into()?),
+				None => None,
+			},
+		})
+	}
+}
+
+/// Helper trait for finding equivocations in finality proofs.
+pub trait FindEquivocations<FinalityProof, FinalityVerificationContext, EquivocationProof> {
+	/// The type returned when encountering an error while looking for equivocations.
+	type Error;
+
+	/// Find equivocations.
+	fn find_equivocations(
+		verification_context: &FinalityVerificationContext,
+		synced_proof: &FinalityProof,
+		source_proofs: &[FinalityProof],
+	) -> Result<Vec<EquivocationProof>, Self::Error>;
 }
 
 /// A minimized version of `pallet-bridge-grandpa::Call` that can be used without a runtime.
@@ -244,16 +282,17 @@ pub trait ChainWithGrandpa: Chain {
 	const AVERAGE_HEADER_SIZE_IN_JUSTIFICATION: u32;
 }
 
-/// A trait that provides the type of the underlying `ChainWithGrandpa`.
-pub trait UnderlyingChainWithGrandpaProvider: UnderlyingChainProvider {
-	/// Underlying `ChainWithGrandpa` type.
-	type ChainWithGrandpa: ChainWithGrandpa;
-}
-
-impl<T> UnderlyingChainWithGrandpaProvider for T
+impl<T> ChainWithGrandpa for T
 where
-	T: UnderlyingChainProvider,
+	T: Chain + UnderlyingChainProvider,
 	T::Chain: ChainWithGrandpa,
 {
-	type ChainWithGrandpa = T::Chain;
+	const WITH_CHAIN_GRANDPA_PALLET_NAME: &'static str =
+		<T::Chain as ChainWithGrandpa>::WITH_CHAIN_GRANDPA_PALLET_NAME;
+	const MAX_AUTHORITIES_COUNT: u32 = <T::Chain as ChainWithGrandpa>::MAX_AUTHORITIES_COUNT;
+	const REASONABLE_HEADERS_IN_JUSTIFICATON_ANCESTRY: u32 =
+		<T::Chain as ChainWithGrandpa>::REASONABLE_HEADERS_IN_JUSTIFICATON_ANCESTRY;
+	const MAX_HEADER_SIZE: u32 = <T::Chain as ChainWithGrandpa>::MAX_HEADER_SIZE;
+	const AVERAGE_HEADER_SIZE_IN_JUSTIFICATION: u32 =
+		<T::Chain as ChainWithGrandpa>::AVERAGE_HEADER_SIZE_IN_JUSTIFICATION;
 }