Remove Parent Hash to Session mapping (#928)

* Adds a SigningContext type

* Bump spec versions

* Fixes requested changes

* Bump ParachainHost api_version and guard signing_context call

* Improve error message

* If there is no signing_context api use default value

Co-authored-by: Robert Habermeier <rphmeier@gmail.com>

polkadot/validation/src/lib.rs

@@ -34,12 +34,11 @@ use std::{
 	sync::Arc,
 };
 use codec::Encode;
-use polkadot_primitives::Hash;
 use polkadot_primitives::parachain::{
 	Id as ParaId, Chain, DutyRoster, AbridgedCandidateReceipt,
 	Statement as PrimitiveStatement,
 	PoVBlock, ErasureChunk, ValidatorSignature, ValidatorIndex,
-	ValidatorPair, ValidatorId,
+	ValidatorPair, ValidatorId, SigningContext,
 };
 use primitives::Pair;
 
@@ -135,9 +134,13 @@ pub struct GroupInfo {
 /// Sign a table statement against a parent hash.
 /// The actual message signed is the encoded statement concatenated with the
 /// parent hash.
-pub fn sign_table_statement(statement: &Statement, key: &ValidatorPair, parent_hash: &Hash) -> ValidatorSignature {
+pub fn sign_table_statement(
+	statement: &Statement,
+	key: &ValidatorPair,
+	signing_context: &SigningContext,
+) -> ValidatorSignature {
 	let mut encoded = PrimitiveStatement::from(statement).encode();
-	encoded.extend(parent_hash.as_ref());
+	encoded.extend(signing_context.encode());
 
 	key.sign(&encoded)
 }
@@ -147,12 +150,12 @@ pub fn check_statement(
 	statement: &Statement,
 	signature: &ValidatorSignature,
 	signer: ValidatorId,
-	parent_hash: &Hash,
+	signing_context: &SigningContext,
 ) -> bool {
 	use runtime_primitives::traits::AppVerify;
 
 	let mut encoded = PrimitiveStatement::from(statement).encode();
-	encoded.extend(parent_hash.as_ref());
+	encoded.extend(signing_context.encode());
 
 	signature.verify(&encoded[..], &signer)
 }
@@ -214,11 +217,19 @@ mod tests {
 	fn sign_and_check_statement() {
 		let statement: Statement = GenericStatement::Valid([1; 32].into());
 		let parent_hash = [2; 32].into();
+		let signing_context = SigningContext {
+			session_index: Default::default(),
+			parent_hash,
+		};
 
-		let sig = sign_table_statement(&statement, &Sr25519Keyring::Alice.pair().into(), &parent_hash);
+		let sig = sign_table_statement(&statement, &Sr25519Keyring::Alice.pair().into(), &signing_context);
 
-		assert!(check_statement(&statement, &sig, Sr25519Keyring::Alice.public().into(), &parent_hash));
-		assert!(!check_statement(&statement, &sig, Sr25519Keyring::Alice.public().into(), &[0xff; 32].into()));
-		assert!(!check_statement(&statement, &sig, Sr25519Keyring::Bob.public().into(), &parent_hash));
+		let wrong_signing_context = SigningContext {
+			session_index: Default::default(),
+			parent_hash: [0xff; 32].into(),
+		};
+		assert!(check_statement(&statement, &sig, Sr25519Keyring::Alice.public().into(), &signing_context));
+		assert!(!check_statement(&statement, &sig, Sr25519Keyring::Alice.public().into(), &wrong_signing_context));
+		assert!(!check_statement(&statement, &sig, Sr25519Keyring::Bob.public().into(), &signing_context));
 	}
 }

polkadot/validation/src/shared_table/mod.rs

@@ -25,7 +25,7 @@ use table::{self, Table, Context as TableContextTrait};
 use polkadot_primitives::{Block, Hash};
 use polkadot_primitives::parachain::{
 	Id as ParaId, AbridgedCandidateReceipt, ValidatorPair, ValidatorId,
-	AttestedCandidate, ParachainHost, PoVBlock, ValidatorIndex,
+	AttestedCandidate, ParachainHost, PoVBlock, ValidatorIndex, SigningContext,
 };
 
 use parking_lot::Mutex;
@@ -48,7 +48,7 @@ pub use table::{SignedStatement, Statement};
 pub use table::generic::Statement as GenericStatement;
 
 struct TableContext {
-	parent_hash: Hash,
+	signing_context: SigningContext,
 	key: Option<Arc<ValidatorPair>>,
 	groups: HashMap<ParaId, GroupInfo>,
 	validators: Vec<ValidatorId>,
@@ -87,7 +87,12 @@ impl TableContext {
 	fn sign_statement(&self, statement: table::Statement) -> Option<table::SignedStatement> {
 		self.local_index().and_then(move |sender|
 			self.key.as_ref()
-				.map(|key| crate::sign_table_statement(&statement, key, &self.parent_hash).into())
+				.map(|key| crate::sign_table_statement(
+						&statement,
+						key,
+						&self.signing_context,
+					).into()
+				)
 				.map(move |signature| table::SignedStatement { statement, signature, sender })
 		)
 	}
@@ -189,7 +194,7 @@ impl SharedTableInner {
 
 		work.map(|work| ParachainWork {
 			availability_store: self.availability_store.clone(),
-			relay_parent: context.parent_hash.clone(),
+			relay_parent: context.signing_context.parent_hash.clone(),
 			work,
 			max_block_data_size,
 			n_validators: context.validators.len(),
@@ -408,12 +413,12 @@ impl SharedTable {
 		validators: Vec<ValidatorId>,
 		groups: HashMap<ParaId, GroupInfo>,
 		key: Option<Arc<ValidatorPair>>,
-		parent_hash: Hash,
+		signing_context: SigningContext,
 		availability_store: AvailabilityStore,
 		max_block_data_size: Option<u64>,
 	) -> Self {
 		SharedTable {
-			context: Arc::new(TableContext { groups, key, parent_hash, validators: validators.clone(), }),
+			context: Arc::new(TableContext { groups, key, signing_context, validators: validators.clone(), }),
 			max_block_data_size,
 			inner: Arc::new(Mutex::new(SharedTableInner {
 				table: Table::default(),
@@ -425,8 +430,8 @@ impl SharedTable {
 	}
 
 	/// Get the parent hash this table should hold statements localized to.
-	pub fn consensus_parent_hash(&self) -> &Hash {
-		&self.context.parent_hash
+	pub fn signing_context(&self) -> &SigningContext {
+		&self.context.signing_context
 	}
 
 	/// Get the local validator session key.
@@ -654,7 +659,11 @@ mod tests {
 		let mut groups = HashMap::new();
 
 		let para_id = ParaId::from(1);
-		let parent_hash = Default::default();
+		let parent_hash = Hash::default();
+		let signing_context = SigningContext {
+			session_index: Default::default(),
+			parent_hash: parent_hash.clone(),
+		};
 
 		let local_key = Sr25519Keyring::Alice.pair();
 		let local_id: ValidatorId = local_key.public().into();
@@ -673,7 +682,7 @@ mod tests {
 			[local_id, validity_other].to_vec(),
 			groups,
 			Some(local_key.clone()),
-			parent_hash,
+			signing_context.clone(),
 			AvailabilityStore::new_in_memory(DummyErasureNetworking),
 			None,
 		);
@@ -684,7 +693,11 @@ mod tests {
 
 		let candidate_statement = GenericStatement::Candidate(candidate);
 
-		let signature = crate::sign_table_statement(&candidate_statement, &validity_other_key.into(), &parent_hash);
+		let signature = crate::sign_table_statement(
+			&candidate_statement,
+			&validity_other_key.into(),
+			&signing_context,
+		);
 		let signed_statement = ::table::generic::SignedStatement {
 			statement: candidate_statement,
 			signature: signature.into(),
@@ -702,7 +715,11 @@ mod tests {
 		let mut groups = HashMap::new();
 
 		let para_id = ParaId::from(1);
-		let parent_hash = Default::default();
+		let parent_hash = Hash::default();
+		let signing_context = SigningContext {
+			session_index: Default::default(),
+			parent_hash: parent_hash.clone(),
+		};
 
 		let local_key = Sr25519Keyring::Alice.pair();
 		let local_id: ValidatorId = local_key.public().into();
@@ -721,7 +738,7 @@ mod tests {
 			[local_id, validity_other].to_vec(),
 			groups,
 			Some(local_key.clone()),
-			parent_hash,
+			signing_context.clone(),
 			AvailabilityStore::new_in_memory(DummyErasureNetworking),
 			None,
 		);
@@ -732,7 +749,11 @@ mod tests {
 
 		let candidate_statement = GenericStatement::Candidate(candidate);
 
-		let signature = crate::sign_table_statement(&candidate_statement, &validity_other_key.into(), &parent_hash);
+		let signature = crate::sign_table_statement(
+			&candidate_statement,
+			&validity_other_key.into(),
+			&signing_context,
+		);
 		let signed_statement = ::table::generic::SignedStatement {
 			statement: candidate_statement,
 			signature: signature.into(),
@@ -874,7 +895,11 @@ mod tests {
 		let mut groups = HashMap::new();
 
 		let para_id = ParaId::from(1);
-		let parent_hash = Default::default();
+		let parent_hash = Hash::default();
+		let signing_context = SigningContext {
+			session_index: Default::default(),
+			parent_hash: parent_hash.clone(),
+		};
 
 		let local_key = Sr25519Keyring::Alice.pair();
 		let local_id: ValidatorId = local_key.public().into();
@@ -893,7 +918,7 @@ mod tests {
 			[local_id, validity_other].to_vec(),
 			groups,
 			Some(local_key.clone()),
-			parent_hash,
+			signing_context.clone(),
 			AvailabilityStore::new_in_memory(DummyErasureNetworking),
 			None,
 		);
@@ -905,7 +930,11 @@ mod tests {
 		let candidate_hash = candidate.hash();
 		let candidate_statement = GenericStatement::Candidate(candidate);
 
-		let signature = crate::sign_table_statement(&candidate_statement, &validity_other_key.into(), &parent_hash);
+		let signature = crate::sign_table_statement(
+			&candidate_statement,
+			&validity_other_key.into(),
+			&signing_context,
+		);
 		let signed_statement = ::table::generic::SignedStatement {
 			statement: candidate_statement,
 			signature: signature.into(),
@@ -934,7 +963,11 @@ mod tests {
 
 		let para_id = ParaId::from(1);
 		let pov_block = pov_block_with_data(vec![1, 2, 3]);
-		let parent_hash = Default::default();
+		let parent_hash = Hash::default();
+		let signing_context = SigningContext {
+			session_index: Default::default(),
+			parent_hash: parent_hash.clone(),
+		};
 
 		let local_key = Sr25519Keyring::Alice.pair();
 		let local_id: ValidatorId = local_key.public().into();
@@ -952,7 +985,7 @@ mod tests {
 			[local_id, validity_other].to_vec(),
 			groups,
 			Some(local_key.clone()),
-			parent_hash,
+			signing_context.clone(),
 			AvailabilityStore::new_in_memory(DummyErasureNetworking),
 			None,
 		);

polkadot/validation/src/validation_service/mod.rs

@@ -36,7 +36,7 @@ use consensus::SelectChain;
 use futures::{future::ready, prelude::*, task::{Spawn, SpawnExt}};
 use polkadot_primitives::{Block, Hash, BlockId};
 use polkadot_primitives::parachain::{
-	Chain, ParachainHost, Id as ParaId, ValidatorIndex, ValidatorId, ValidatorPair,
+	Chain, ParachainHost, Id as ParaId, ValidatorIndex, ValidatorId, ValidatorPair, SigningContext,
 };
 use babe_primitives::BabeApi;
 use keystore::KeyStorePtr;
@@ -44,7 +44,7 @@ use sp_api::{ApiExt, ProvideRuntimeApi};
 use runtime_primitives::traits::HashFor;
 use availability_store::Store as AvailabilityStore;
 
-use log::{warn, error, info, debug};
+use log::{warn, error, info, debug, trace};
 
 use super::{Network, Collators, SharedTable, TableRouter};
 use crate::Error;
@@ -334,11 +334,29 @@ impl<C, N, P, SP> ParachainValidationInstances<C, N, P, SP> where
 			}
 		}
 
+		let api = self.client.runtime_api();
+
+		let signing_context = if api.has_api_with::<dyn ParachainHost<Block, Error = ()>, _>(
+			&BlockId::hash(parent_hash),
+			|version| version >= 3,
+		)? {
+			api.signing_context(&id)?
+		} else {
+			trace!(
+				target: "validation",
+				"Expected runtime with ParachainHost version >= 3",
+			);
+			SigningContext {
+				session_index: 0,
+				parent_hash,
+			}
+		};
+
 		let table = Arc::new(SharedTable::new(
 			validators.clone(),
 			group_info,
 			sign_with,
-			parent_hash,
+			signing_context,
 			self.availability_store.clone(),
 			max_block_data_size,
 		));