Ensure relay chain parent is the relay chain head (#103)

Author: cecton

Cargo.lock

@@ -6,6 +6,7 @@ edition = "2018"
 
 [dependencies]
 # Substrate dependencies
+sp-blockchain = { git = "https://github.com/paritytech/substrate", branch = "cumulus-branch" }
 sp-runtime = { git = "https://github.com/paritytech/substrate", branch = "cumulus-branch" }
 sp-core = { git = "https://github.com/paritytech/substrate", branch = "cumulus-branch" }
 sp-consensus = { git = "https://github.com/paritytech/substrate", branch = "cumulus-branch" }

collator/Cargo.toml

@@ -25,6 +25,7 @@ use cumulus_primitives::{
 };
 use cumulus_runtime::ParachainBlockData;
 
+use sp_blockchain::HeaderBackend;
 use sp_consensus::{
 	BlockImport, BlockImportParams, BlockOrigin, Environment, Error as ConsensusError,
 	ForkChoiceStrategy, Proposal, Proposer, RecordProof,
@@ -350,14 +351,15 @@ where
 		polkadot_network: impl CollatorNetwork + Clone + 'static,
 	) -> Result<Self::ParachainContext, ()>
 	where
-		PClient: ProvideRuntimeApi<PBlock> + Send + Sync + BlockchainEvents<PBlock> + 'static,
+		PClient: ProvideRuntimeApi<PBlock> + BlockchainEvents<PBlock> + HeaderBackend<PBlock>
+			+ Send + Sync + 'static,
 		PClient::Api: RuntimeApiCollection<Extrinsic>,
 		<PClient::Api as ApiExt<PBlock>>::StateBackend: StateBackend<HashFor<PBlock>>,
 		Spawner: Spawn + Clone + Send + Sync + 'static,
 		Extrinsic: codec::Codec + Send + Sync + 'static,
 	{
 		self.delayed_block_announce_validator.set(
-			Box::new(JustifiedBlockAnnounceValidator::new(Vec::new(), polkadot_client.clone())),
+			Box::new(JustifiedBlockAnnounceValidator::new(polkadot_client.clone())),
 		);
 
 		let follow =

collator/src/lib.rs

@@ -24,3 +24,14 @@ codec = { package = "parity-scale-codec", version = "1.3.0", features = [ "deriv
 futures = { version = "0.3.1", features = ["compat"] }
 log = "0.4.8"
 parking_lot = "0.10.2"
+
+[dev-dependencies]
+cumulus-test-runtime = { path = "../test/runtime" }
+
+# substrate deps
+sc-client-api = { git = "https://github.com/paritytech/substrate", branch = "cumulus-branch" }
+sp-core = { git = "https://github.com/paritytech/substrate", branch = "cumulus-branch" }
+sp-keyring = { git = "https://github.com/paritytech/substrate", branch = "cumulus-branch" }
+
+# polkadot deps
+polkadot-test-runtime-client = { git = "https://github.com/paritytech/polkadot", branch = "cumulus-branch" }

network/Cargo.toml

@@ -18,15 +18,18 @@
 //!
 //! Contains message send between collators and logic to process them.
 
+#[cfg(test)]
+mod tests;
+
 use sp_api::ProvideRuntimeApi;
-use sp_blockchain::Error as ClientError;
+use sp_blockchain::{Error as ClientError, HeaderBackend};
 use sp_consensus::block_validation::{BlockAnnounceValidator, Validation};
 use sp_runtime::{generic::BlockId, traits::Block as BlockT};
 
 use polkadot_collator::Network as CollatorNetwork;
 use polkadot_network::legacy::gossip::{GossipMessage, GossipStatement};
 use polkadot_primitives::{
-	parachain::{ParachainHost, ValidatorId},
+	parachain::ParachainHost,
 	Block as PBlock, Hash as PHash,
 };
 use polkadot_statement_table::{SignedStatement, Statement};
@@ -49,15 +52,13 @@ use parking_lot::Mutex;
 ///
 /// Note: if no justification is provided the annouce is considered valid.
 pub struct JustifiedBlockAnnounceValidator<B, P> {
-	authorities: Vec<ValidatorId>,
 	phantom: PhantomData<B>,
 	polkadot_client: Arc<P>,
 }
 
 impl<B, P> JustifiedBlockAnnounceValidator<B, P> {
-	pub fn new(authorities: Vec<ValidatorId>, polkadot_client: Arc<P>) -> Self {
+	pub fn new(polkadot_client: Arc<P>) -> Self {
 		Self {
-			authorities,
 			phantom: Default::default(),
 			polkadot_client,
 		}
@@ -66,7 +67,7 @@ impl<B, P> JustifiedBlockAnnounceValidator<B, P> {
 
 impl<B: BlockT, P> BlockAnnounceValidator<B> for JustifiedBlockAnnounceValidator<B, P>
 where
-	P: ProvideRuntimeApi<PBlock>,
+	P: ProvideRuntimeApi<PBlock> + HeaderBackend<PBlock>,
 	P::Api: ParachainHost<PBlock>,
 {
 	fn validate(
@@ -106,14 +107,42 @@ where
 			},
 		} = gossip_statement;
 
-		let signing_context = self
-			.polkadot_client
-			.runtime_api()
-			.signing_context(&BlockId::Hash(relay_chain_leaf))
+		// Check that the relay chain parent of the block is the relay chain head
+		let best_number = self.polkadot_client.info().best_number;
+
+		match self.polkadot_client.number(relay_chain_leaf) {
+			Err(err) => {
+				return Err(Box::new(ClientError::Backend(format!(
+					"could not find block number for {}: {}",
+					relay_chain_leaf, err,
+				))));
+			},
+			Ok(Some(x)) if x == best_number => {},
+			Ok(None) => {
+				return Err(Box::new(ClientError::UnknownBlock(relay_chain_leaf.to_string())));
+			},
+			Ok(Some(_)) => {
+				trace!(
+					target: "cumulus-network",
+					"validation failed because the relay chain parent ({}) is not the relay chain \
+					head ({})",
+					relay_chain_leaf, best_number,
+				);
+
+				return Ok(Validation::Failure);
+			},
+		}
+
+		let runtime_api = self.polkadot_client.runtime_api();
+		let runtime_api_block_id = BlockId::Hash(relay_chain_leaf);
+		let signing_context = runtime_api
+			.signing_context(&runtime_api_block_id)
 			.map_err(|e| Box::new(ClientError::Msg(format!("{:?}", e))) as Box<_>)?;
 
 		// Check that the signer is a legit validator.
-		let signer = self.authorities.get(sender as usize).ok_or_else(|| {
+		let authorities = runtime_api.validators(&runtime_api_block_id)
+			.map_err(|e| Box::new(ClientError::Msg(format!("{:?}", e))) as Box<_>)?;
+		let signer = authorities.get(sender as usize).ok_or_else(|| {
 			Box::new(ClientError::BadJustification(
 				"block accounced justification signer is a validator index out of bound"
 					.to_string(),