Enforce target candidate is part of the signature

Signed-off-by: Alexandru Gheorghe <alexandru.gheorghe@parity.io>

node/core/approval-voting/src/lib.rs

@@ -2268,9 +2268,9 @@ where
 		let candidate_hashes: Vec<CandidateHash> =
 			approved_candidates_info.iter().map(|candidate| candidate.1).collect();
 		// Signature check:
-		match DisputeStatement::Valid(ValidDisputeStatementKind::ApprovalCheckingV2(
-			candidate_hashes.clone(),
-		))
+		match DisputeStatement::Valid(
+			ValidDisputeStatementKind::ApprovalCheckingMultipleCandidates(candidate_hashes.clone()),
+		)
 		.check_signature(
 			&pubkey,
 			*candidate_hashes.first().expect("Checked above this is not empty; qed"),
@@ -3243,7 +3243,7 @@ fn sign_approval(
 ) -> Option<ValidatorSignature> {
 	let key = keystore.key_pair::<ValidatorPair>(public).ok().flatten()?;
 
-	let payload = ApprovalVoteMultipleCandidates(candidate_hashes).signing_payload(session_index);
+	let payload = ApprovalVoteMultipleCandidates(&candidate_hashes).signing_payload(session_index);
 
 	Some(key.sign(&payload[..]))
 }

node/core/approval-voting/src/tests.rs

@@ -1975,9 +1975,9 @@ fn test_signing_a_single_candidate_is_backwards_compatible() {
 		session_index,
 	);
 
-	assert!(DisputeStatement::Valid(ValidDisputeStatementKind::ApprovalCheckingV2(vec![
-		candidate_hash
-	]))
+	assert!(DisputeStatement::Valid(
+		ValidDisputeStatementKind::ApprovalCheckingMultipleCandidates(vec![candidate_hash])
+	)
 	.check_signature(&Sr25519Keyring::Alice.public().into(), candidate_hash, session_index, &sig_c,)
 	.is_ok());
 
@@ -1990,9 +1990,9 @@ fn test_signing_a_single_candidate_is_backwards_compatible() {
 		)
 		.is_ok());
 
-	assert!(DisputeStatement::Valid(ValidDisputeStatementKind::ApprovalCheckingV2(vec![
-		candidate_hash
-	]))
+	assert!(DisputeStatement::Valid(
+		ValidDisputeStatementKind::ApprovalCheckingMultipleCandidates(vec![candidate_hash])
+	)
 	.check_signature(&Sr25519Keyring::Alice.public().into(), candidate_hash, session_index, &sig_a,)
 	.is_ok());
 
@@ -2002,9 +2002,9 @@ fn test_signing_a_single_candidate_is_backwards_compatible() {
 		session_index,
 	);
 
-	assert!(DisputeStatement::Valid(ValidDisputeStatementKind::ApprovalCheckingV2(
-		candidate_hashes.clone()
-	))
+	assert!(DisputeStatement::Valid(
+		ValidDisputeStatementKind::ApprovalCheckingMultipleCandidates(candidate_hashes.clone())
+	)
 	.check_signature(
 		&Sr25519Keyring::Alice.public().into(),
 		*candidate_hashes.first().expect("test"),

node/core/dispute-coordinator/src/import.rs

@@ -528,7 +528,7 @@ impl ImportResult {
 				{
 					let pub_key = &env.session_info().validators.get(index).expect("indices are validated by approval-voting subsystem; qed");
 					let session_index = env.session_index();
-					candidate_hashes.contains(&votes.candidate_receipt.hash()) && DisputeStatement::Valid(ValidDisputeStatementKind::ApprovalCheckingV2(candidate_hashes.clone()))
+					candidate_hashes.contains(&votes.candidate_receipt.hash()) && DisputeStatement::Valid(ValidDisputeStatementKind::ApprovalCheckingMultipleCandidates(candidate_hashes.clone()))
 						.check_signature(pub_key, *candidate_hashes.first().expect("Valid votes have at least one candidate; qed"), session_index, &sig)
 						.is_ok()
 				},

node/primitives/src/disputes/mod.rs

@@ -46,6 +46,15 @@ pub struct SignedDisputeStatement {
 	session_index: SessionIndex,
 }
 
+/// Errors encountered while signing a dispute statement
+#[derive(Debug)]
+pub enum SignedDisputeStatementError {
+	/// Encountered a keystore error while signing
+	KeyStoreError(KeystoreError),
+	/// Could not generate signing payload
+	PayloadError,
+}
+
 /// Tracked votes on candidates, for the purposes of dispute resolution.
 #[derive(Debug, Clone)]
 pub struct CandidateVotes {
@@ -108,7 +117,7 @@ impl ValidCandidateVotes {
 				ValidDisputeStatementKind::BackingSeconded(_) => false,
 				ValidDisputeStatementKind::Explicit |
 				ValidDisputeStatementKind::ApprovalChecking |
-				ValidDisputeStatementKind::ApprovalCheckingV2(_) => {
+				ValidDisputeStatementKind::ApprovalCheckingMultipleCandidates(_) => {
 					occupied.insert((kind.clone(), sig));
 					kind != occupied.get().0
 				},
@@ -214,16 +223,19 @@ impl SignedDisputeStatement {
 		candidate_hash: CandidateHash,
 		session_index: SessionIndex,
 		validator_public: ValidatorId,
-	) -> Result<Option<Self>, KeystoreError> {
+	) -> Result<Option<Self>, SignedDisputeStatementError> {
 		let dispute_statement = if valid {
 			DisputeStatement::Valid(ValidDisputeStatementKind::Explicit)
 		} else {
 			DisputeStatement::Invalid(InvalidDisputeStatementKind::Explicit)
 		};
 
-		let data = dispute_statement.payload_data(candidate_hash, session_index);
+		let data = dispute_statement
+			.payload_data(candidate_hash, session_index)
+			.map_err(|_| SignedDisputeStatementError::PayloadError)?;
 		let signature = keystore
-			.sr25519_sign(ValidatorId::ID, validator_public.as_ref(), &data)?
+			.sr25519_sign(ValidatorId::ID, validator_public.as_ref(), &data)
+			.map_err(SignedDisputeStatementError::KeyStoreError)?
 			.map(|sig| Self {
 				dispute_statement,
 				candidate_hash,

primitives/src/v5/mod.rs

@@ -1069,9 +1069,9 @@ impl ApprovalVote {
 
 /// A vote of approvalf for multiple candidates.
 #[derive(Clone, RuntimeDebug)]
-pub struct ApprovalVoteMultipleCandidates(pub Vec<CandidateHash>);
+pub struct ApprovalVoteMultipleCandidates<'a>(pub &'a Vec<CandidateHash>);
 
-impl ApprovalVoteMultipleCandidates {
+impl<'a> ApprovalVoteMultipleCandidates<'a> {
 	/// Yields the signing payload for this approval vote.
 	pub fn signing_payload(&self, session_index: SessionIndex) -> Vec<u8> {
 		const MAGIC: [u8; 4] = *b"APPR";
@@ -1260,28 +1260,39 @@ pub enum DisputeStatement {
 
 impl DisputeStatement {
 	/// Get the payload data for this type of dispute statement.
-	pub fn payload_data(&self, candidate_hash: CandidateHash, session: SessionIndex) -> Vec<u8> {
+	pub fn payload_data(
+		&self,
+		candidate_hash: CandidateHash,
+		session: SessionIndex,
+	) -> Result<Vec<u8>, ()> {
 		match self {
 			DisputeStatement::Valid(ValidDisputeStatementKind::Explicit) =>
-				ExplicitDisputeStatement { valid: true, candidate_hash, session }.signing_payload(),
+				Ok(ExplicitDisputeStatement { valid: true, candidate_hash, session }
+					.signing_payload()),
 			DisputeStatement::Valid(ValidDisputeStatementKind::BackingSeconded(
 				inclusion_parent,
-			)) => CompactStatement::Seconded(candidate_hash).signing_payload(&SigningContext {
+			)) => Ok(CompactStatement::Seconded(candidate_hash).signing_payload(&SigningContext {
 				session_index: session,
 				parent_hash: *inclusion_parent,
-			}),
+			})),
 			DisputeStatement::Valid(ValidDisputeStatementKind::BackingValid(inclusion_parent)) =>
-				CompactStatement::Valid(candidate_hash).signing_payload(&SigningContext {
+				Ok(CompactStatement::Valid(candidate_hash).signing_payload(&SigningContext {
 					session_index: session,
 					parent_hash: *inclusion_parent,
-				}),
+				})),
 			DisputeStatement::Valid(ValidDisputeStatementKind::ApprovalChecking) =>
-				ApprovalVote(candidate_hash).signing_payload(session),
-			DisputeStatement::Valid(ValidDisputeStatementKind::ApprovalCheckingV2(
-				candidate_hashes,
-			)) => ApprovalVoteMultipleCandidates(candidate_hashes.clone()).signing_payload(session),
+				Ok(ApprovalVote(candidate_hash).signing_payload(session)),
+			DisputeStatement::Valid(
+				ValidDisputeStatementKind::ApprovalCheckingMultipleCandidates(candidate_hashes),
+			) =>
+				if candidate_hashes.contains(&candidate_hash) {
+					Ok(ApprovalVoteMultipleCandidates(candidate_hashes).signing_payload(session))
+				} else {
+					Err(())
+				},
 			DisputeStatement::Invalid(InvalidDisputeStatementKind::Explicit) =>
-				ExplicitDisputeStatement { valid: false, candidate_hash, session }.signing_payload(),
+				Ok(ExplicitDisputeStatement { valid: false, candidate_hash, session }
+					.signing_payload()),
 		}
 	}
 
@@ -1293,7 +1304,7 @@ impl DisputeStatement {
 		session: SessionIndex,
 		validator_signature: &ValidatorSignature,
 	) -> Result<(), ()> {
-		let payload = self.payload_data(candidate_hash, session);
+		let payload = self.payload_data(candidate_hash, session)?;
 
 		if validator_signature.verify(&payload[..], &validator_public) {
 			Ok(())
@@ -1325,7 +1336,7 @@ impl DisputeStatement {
 			Self::Valid(ValidDisputeStatementKind::BackingValid(_)) => true,
 			Self::Valid(ValidDisputeStatementKind::Explicit) |
 			Self::Valid(ValidDisputeStatementKind::ApprovalChecking) |
-			Self::Valid(ValidDisputeStatementKind::ApprovalCheckingV2(_)) |
+			Self::Valid(ValidDisputeStatementKind::ApprovalCheckingMultipleCandidates(_)) |
 			Self::Invalid(_) => false,
 		}
 	}
@@ -1350,7 +1361,7 @@ pub enum ValidDisputeStatementKind {
 	/// TODO: Fixme this probably means we can't create this version
 	/// untill all nodes have been updated to support it.
 	#[codec(index = 4)]
-	ApprovalCheckingV2(Vec<CandidateHash>),
+	ApprovalCheckingMultipleCandidates(Vec<CandidateHash>),
 }
 
 /// Different kinds of statements of invalidity on a candidate.

runtime/parachains/src/disputes.rs

@@ -1330,24 +1330,29 @@ fn check_signature(
 	statement: &DisputeStatement,
 	validator_signature: &ValidatorSignature,
 ) -> Result<(), ()> {
-	let payload = match *statement {
+	let payload = match statement {
 		DisputeStatement::Valid(ValidDisputeStatementKind::Explicit) =>
 			ExplicitDisputeStatement { valid: true, candidate_hash, session }.signing_payload(),
 		DisputeStatement::Valid(ValidDisputeStatementKind::BackingSeconded(inclusion_parent)) =>
 			CompactStatement::Seconded(candidate_hash).signing_payload(&SigningContext {
 				session_index: session,
-				parent_hash: inclusion_parent,
+				parent_hash: *inclusion_parent,
 			}),
 		DisputeStatement::Valid(ValidDisputeStatementKind::BackingValid(inclusion_parent)) =>
 			CompactStatement::Valid(candidate_hash).signing_payload(&SigningContext {
 				session_index: session,
-				parent_hash: inclusion_parent,
+				parent_hash: *inclusion_parent,
 			}),
 		DisputeStatement::Valid(ValidDisputeStatementKind::ApprovalChecking) =>
 			ApprovalVote(candidate_hash).signing_payload(session),
-		DisputeStatement::Valid(ValidDisputeStatementKind::ApprovalCheckingV2(_)) =>
-		// TODO: Fixme
-			ApprovalVoteMultipleCandidates(vec![candidate_hash]).signing_payload(session),
+		DisputeStatement::Valid(ValidDisputeStatementKind::ApprovalCheckingMultipleCandidates(
+			candidates,
+		)) =>
+			if candidates.contains(&candidate_hash) {
+				ApprovalVoteMultipleCandidates(candidates).signing_payload(session)
+			} else {
+				return Err(())
+			},
 		DisputeStatement::Invalid(InvalidDisputeStatementKind::Explicit) =>
 			ExplicitDisputeStatement { valid: false, candidate_hash, session }.signing_payload(),
 	};