Merge pull request #17 from paritytech/gui-candidate-justification

implementation of BlockAnnounceValidator

Cargo.toml

@@ -1,6 +1,7 @@
 [workspace]
 members = [
 	"consensus",
+	"network",
 	"runtime",
 	"test/runtime",
 	"test/client",

network/Cargo.toml

@@ -0,0 +1,21 @@
+[package]
+name = "cumulus-network"
+version = "0.1.0"
+authors = ["Parity Technologies <admin@parity.io>"]
+description = "Cumulus-specific networking protocol"
+edition = "2018"
+
+[dependencies]
+# substrate deps
+substrate-client = { git = "https://github.com/paritytech/substrate", branch = "bkchr-cumulus-branch" }
+substrate-consensus-common = { git = "https://github.com/paritytech/substrate", branch = "bkchr-cumulus-branch" }
+sr-primitives = { git = "https://github.com/paritytech/substrate", branch = "bkchr-cumulus-branch" }
+
+# polkadot deps
+polkadot-primitives = { git = "https://github.com/paritytech/polkadot", branch = "bkchr-cumulus-branch" }
+polkadot-statement-table = { git = "https://github.com/paritytech/polkadot", branch = "bkchr-cumulus-branch" }
+polkadot-validation = { git = "https://github.com/paritytech/polkadot", branch = "bkchr-cumulus-branch" }
+polkadot-network = { git = "https://github.com/paritytech/polkadot", branch = "bkchr-cumulus-branch" }
+
+# other deps
+codec = { package = "parity-scale-codec", version = "1.0.5", features = [ "derive" ] }

network/src/lib.rs

@@ -0,0 +1,121 @@
+// Copyright 2019 Parity Technologies (UK) Ltd.
+// This file is part of Polkadot.
+
+// Polkadot 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.
+
+// Polkadot 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 Polkadot.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Cumulus-specific network implementation.
+//!
+//! Contains message send between collators and logic to process them.
+
+use substrate_client::error::{Error as ClientError};
+use sr_primitives::traits::{Block as BlockT};
+use substrate_consensus_common::block_validation::{Validation, BlockAnnounceValidator};
+
+use polkadot_primitives::parachain::ValidatorId;
+use polkadot_statement_table::{SignedStatement, Statement};
+use polkadot_validation::check_statement;
+use polkadot_network::gossip::{GossipStatement, GossipMessage};
+
+use codec::{Decode, Encode};
+
+use std::marker::PhantomData;
+
+/// Validate that data is a valid justification from a relay-chain validator that the block is a
+/// valid parachain-block candidate.
+/// Data encoding is just `GossipMessage`, the relay-chain validator candidate statement message is
+/// the justification.
+///
+/// Note: if no justification is provided the annouce is considered valid.
+pub struct JustifiedBlockAnnounceValidator<B> {
+	authorities: Vec<ValidatorId>,
+	phantom: PhantomData<B>,
+}
+
+impl<B: BlockT> JustifiedBlockAnnounceValidator<B> {
+	pub fn new(authorities: Vec<ValidatorId>) -> Self {
+		Self {
+			authorities,
+			phantom: Default::default(),
+		}
+	}
+}
+
+impl<B: BlockT> BlockAnnounceValidator<B> for JustifiedBlockAnnounceValidator<B> {
+	fn validate(&mut self, header: &B::Header, mut data: &[u8])
+		-> Result<Validation, Box<dyn std::error::Error + Send>>
+	{
+		// If no data is provided the announce is valid.
+		if data.is_empty() {
+			return Ok(Validation::Success)
+		}
+
+		// Check data is a gossip message.
+		let gossip_message = GossipMessage::decode(&mut data)
+			.map_err(|_| Box::new(ClientError::BadJustification(
+				"cannot decode block announced justification, must be a gossip message".to_string()
+			)) as Box<_>)?;
+
+		// Check message is a gossip statement.
+		let gossip_statement = match gossip_message {
+			GossipMessage::Statement(gossip_statement) => gossip_statement,
+			_ => return Err(Box::new(ClientError::BadJustification(
+				"block announced justification statement must be a gossip statement".to_string()
+			)) as Box<_>)
+		};
+
+		let GossipStatement {
+				relay_chain_leaf,
+				signed_statement: SignedStatement {
+					statement,
+					signature,
+					sender,
+				}
+		} = gossip_statement;
+
+		// Check that the signer is a legit validator.
+		let signer = self.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()
+			)) as Box<_>)?;
+
+		// Check statement is correctly signed.
+		if !check_statement(
+			&statement,
+			&signature,
+			signer.clone(),
+			&relay_chain_leaf,
+		) {
+			return Err(Box::new(ClientError::BadJustification(
+				"block announced justification signature is invalid".to_string()
+			)) as Box<_>)
+		}
+
+		// Check statement is a candidate statement.
+		let candidate_receipt = match statement {
+			Statement::Candidate(candidate_receipt) => candidate_receipt,
+			_ => return Err(Box::new(ClientError::BadJustification(
+				"block announced justification statement must be a candidate statement".to_string()
+			)) as Box<_>)
+		};
+
+		// Check the header in the candidate_receipt match header given header.
+		if header.encode() != candidate_receipt.head_data.0 {
+			return Err(Box::new(ClientError::BadJustification(
+				"block announced header does not match the one justified".to_string()
+			)) as Box<_>)
+		}
+
+		Ok(Validation::Success)
+	}
+}