Initial version of bridging pallets as git subtree (#2458)

* Initial version of bridges pallet as subtree of https://github.com/paritytech/parity-bridges-common
Added `Bridges subtree files` pr review rule

* Squashed 'bridges/' content from commit d30927c08

git-subtree-dir: bridges
git-subtree-split: d30927c089bd9e73092d1ec1a62895603cb277a3

* Updated REAMDE.md and BRIDGES.md (inspired by original https://github.com/paritytech/polkadot/blob/d22eb62fe40e55e15eb91d375f48cc540d83a47e/BRIDGES.md)

* Squashed 'bridges/' changes from d30927c08..d3970944b

d3970944b Small simplifications (#2050)

git-subtree-dir: bridges
git-subtree-split: d3970944b0cfc4ea5226225e1ca07dab234c3556

* Squashed 'bridges/' changes from d3970944b..2180797fb

2180797fb Removed CODEOWNERS (#2051)

git-subtree-dir: bridges
git-subtree-split: 2180797fbf8a990490c67853dcffd81bc8dd083c

* Squashed 'bridges/' changes from 2180797fbf..4850aac8ce

4850aac8ce Removed relayer_account: &AccountId from MessageDispatch  (#2080)
8c8adafd54 Revert "Fix max-size messages at test chains (#2064)" (#2077)
c01a63efd8 Fixed off-by-one when confirming rewards in messages pallet (#2075)
a298be96aa Update subxt dependencies (#2072)
c0eef51eab Fix max-size messages at test chains (#2064)
3a658e3697 Messages relay fixes (#2073)
0022b5ab22 Slash relayers for invalid transactions (#2025)
198104007f Bump enumflags2 from 0.7.5 to 0.7.7
9229b257e5 [ci] Fix rules for docker build (#2069)
660d791390 [ci] Update buildah command and version (#2058)
e4535c0ca4 fix the way latest_confirmed_nonce_at_source is "calculated" (#2067)
dbc2d37590 select nothing if we have already selected nonces to submit or have submitted something (#2065)
a7eedd21fe [relay-substrate-client] Bump jsonrpsee (#2066)
8875d5aeae Bump clap from 4.2.2 to 4.2.4
25f9cf55e2 Another use of RangeInclusiveExt::checked_len() (#2060)
4942c12a5f submit lane unblock transactions from relay (#2030)
c0325d3c9c Test deployments fixes (#2057)
fc7b9b7ed7 Use the new matrix server (#2056)
63bcb5c10b Fixed delivery alert rule (#2052)

git-subtree-dir: bridges
git-subtree-split: 4850aac8ce6c34e5ca6246b88cd14c873a879cba

* Squashed 'bridges/' changes from 4850aac8ce..66aaf0dd23

66aaf0dd23 Nits (#2083)

git-subtree-dir: bridges
git-subtree-split: 66aaf0dd239dde40b64264061a77c921e2c82568

* Squashed 'bridges/' changes from 66aaf0dd23..557ecbcecc

557ecbcecc Fix sized messages (Follow-up on #2064) (#2103)
54f587a066 Add weight of refund extension post_dispatch to the weights of messages pallet (#2089)
5b1626f8c4 fix pallet param for nightly benchmarks check (#2099)
ae44c6b7a1 Add millau specific messages weights (#2097)
6ad0bd1f1e Add integrity tests to rialto parachain runtiime (#2096)
6919556de5 Bump tokio from 1.27.0 to 1.28.0
58795fcb75 Bump clap from 4.2.4 to 4.2.5
01bf31085b Bump scale-info from 2.5.0 to 2.6.0
8fe383240d Bump anyhow from 1.0.70 to 1.0.71
8d94e82ad5 deployments: add new BEEFY metrics and alarms (#2090)
e9a4749e7e Bump wasmtime from 6.0.1 to 6.0.2
9d9936c0d9 Bump wasmtime from 6.0.1 to 6.0.2 in /tools/runtime-codegen
5d77cd7bee Add more logs to relayer and message pallets (#2082)
75fbb9d3ef Update comment (#2081)
9904d09cf6 Benchmarks for new relayers pallet calls (#2040)

git-subtree-dir: bridges
git-subtree-split: 557ecbcecc585547b744a5ac9fb8d7f3b9de4521

* fmt

* Squashed 'bridges/' changes from 557ecbcecc..04b3dda6aa

04b3dda6aa Remove from subtree (#2111)
f8ff15e7e7 Add `MessagesPalletInstance` for integrity tests (#2107)
92ccef58e6 Use generated runtimes for BHR/BHW (#2106)
b33e0a585b Fix comment (#2105)

git-subtree-dir: bridges
git-subtree-split: 04b3dda6aa38599e612ff637710b6d2cff275ef3

* ".git/.scripts/commands/fmt/fmt.sh"

---------

Co-authored-by: parity-processbot <>

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

@@ -0,0 +1,390 @@
+// Copyright 2019-2021 Parity Technologies (UK) Ltd.
+// This file is part of Parity Bridges Common.
+
+// Parity Bridges Common 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.
+
+// Parity Bridges Common 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 Parity Bridges Common.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Pallet for checking GRANDPA Finality Proofs.
+//!
+//! Adapted copy of substrate/client/finality-grandpa/src/justification.rs. If origin
+//! will ever be moved to the sp_consensus_grandpa, we should reuse that implementation.
+
+use crate::ChainWithGrandpa;
+
+use bp_runtime::{BlockNumberOf, Chain, HashOf};
+use codec::{Decode, Encode, MaxEncodedLen};
+use finality_grandpa::voter_set::VoterSet;
+use frame_support::RuntimeDebug;
+use scale_info::TypeInfo;
+use sp_consensus_grandpa::{AuthorityId, AuthoritySignature, SetId};
+use sp_runtime::{traits::Header as HeaderT, SaturatedConversion};
+use sp_std::{
+	collections::{btree_map::BTreeMap, btree_set::BTreeSet},
+	prelude::*,
+};
+
+/// A GRANDPA Justification is a proof that a given header was finalized
+/// at a certain height and with a certain set of authorities.
+///
+/// This particular proof is used to prove that headers on a bridged chain
+/// (so not our chain) have been finalized correctly.
+#[derive(Encode, Decode, RuntimeDebug, Clone, PartialEq, Eq, TypeInfo)]
+pub struct GrandpaJustification<Header: HeaderT> {
+	/// The round (voting period) this justification is valid for.
+	pub round: u64,
+	/// The set of votes for the chain which is to be finalized.
+	pub commit:
+		finality_grandpa::Commit<Header::Hash, Header::Number, AuthoritySignature, AuthorityId>,
+	/// A proof that the chain of blocks in the commit are related to each other.
+	pub votes_ancestries: Vec<Header>,
+}
+
+impl<H: HeaderT> GrandpaJustification<H> {
+	/// Returns reasonable size of justification using constants from the provided chain.
+	///
+	/// An imprecise analogue of `MaxEncodedLen` implementation. We don't use it for
+	/// any precise calculations - that's just an estimation.
+	pub fn max_reasonable_size<C>(required_precommits: u32) -> u32
+	where
+		C: Chain<Header = H> + ChainWithGrandpa,
+	{
+		// we don't need precise results here - just estimations, so some details
+		// are removed from computations (e.g. bytes required to encode vector length)
+
+		// structures in `finality_grandpa` crate are not implementing `MaxEncodedLength`, so
+		// here's our estimation for the `finality_grandpa::Commit` struct size
+		//
+		// precommit is: hash + number
+		// signed precommit is: precommit + signature (64b) + authority id
+		// commit is: hash + number + vec of signed precommits
+		let signed_precommit_size: u32 = BlockNumberOf::<C>::max_encoded_len()
+			.saturating_add(HashOf::<C>::max_encoded_len().saturated_into())
+			.saturating_add(64)
+			.saturating_add(AuthorityId::max_encoded_len().saturated_into())
+			.saturated_into();
+		let max_expected_signed_commit_size = signed_precommit_size
+			.saturating_mul(required_precommits)
+			.saturating_add(BlockNumberOf::<C>::max_encoded_len().saturated_into())
+			.saturating_add(HashOf::<C>::max_encoded_len().saturated_into());
+
+		// justification is a signed GRANDPA commit, `votes_ancestries` vector and round number
+		let max_expected_votes_ancestries_size = C::REASONABLE_HEADERS_IN_JUSTIFICATON_ANCESTRY
+			.saturating_mul(C::AVERAGE_HEADER_SIZE_IN_JUSTIFICATION);
+
+		8u32.saturating_add(max_expected_signed_commit_size)
+			.saturating_add(max_expected_votes_ancestries_size)
+	}
+}
+
+impl<H: HeaderT> crate::FinalityProof<H::Number> for GrandpaJustification<H> {
+	fn target_header_number(&self) -> H::Number {
+		self.commit.target_number
+	}
+}
+
+/// Justification verification error.
+#[derive(Eq, RuntimeDebug, PartialEq)]
+pub enum Error {
+	/// Failed to decode justification.
+	JustificationDecode,
+	/// Justification is finalizing unexpected header.
+	InvalidJustificationTarget,
+	/// Justification contains redundant votes.
+	RedundantVotesInJustification,
+	/// Justification contains unknown authority precommit.
+	UnknownAuthorityVote,
+	/// Justification contains duplicate authority precommit.
+	DuplicateAuthorityVote,
+	/// The authority has provided an invalid signature.
+	InvalidAuthoritySignature,
+	/// The justification contains precommit for header that is not a descendant of the commit
+	/// header.
+	PrecommitIsNotCommitDescendant,
+	/// The cumulative weight of all votes in the justification is not enough to justify commit
+	/// header finalization.
+	TooLowCumulativeWeight,
+	/// The justification contains extra (unused) headers in its `votes_ancestries` field.
+	ExtraHeadersInVotesAncestries,
+}
+
+/// Given GRANDPA authorities set size, return number of valid authorities votes that the
+/// justification must have to be valid.
+///
+/// This function assumes that all authorities have the same vote weight.
+pub fn required_justification_precommits(authorities_set_length: u32) -> u32 {
+	authorities_set_length - authorities_set_length.saturating_sub(1) / 3
+}
+
+/// Decode justification target.
+pub fn decode_justification_target<Header: HeaderT>(
+	raw_justification: &[u8],
+) -> Result<(Header::Hash, Header::Number), Error> {
+	GrandpaJustification::<Header>::decode(&mut &*raw_justification)
+		.map(|justification| (justification.commit.target_hash, justification.commit.target_number))
+		.map_err(|_| Error::JustificationDecode)
+}
+
+/// 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>,
+	justification: GrandpaJustification<Header>,
+) -> Result<GrandpaJustification<Header>, Error>
+where
+	Header::Number: finality_grandpa::BlockNumberOps,
+{
+	let mut optimizer = OptimizationCallbacks(Vec::new());
+	verify_justification_with_callbacks(
+		finalized_target,
+		authorities_set_id,
+		authorities_set,
+		&justification,
+		&mut optimizer,
+	)?;
+	Ok(optimizer.optimize(justification))
+}
+
+/// 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>,
+	justification: &GrandpaJustification<Header>,
+) -> Result<(), Error>
+where
+	Header::Number: finality_grandpa::BlockNumberOps,
+{
+	verify_justification_with_callbacks(
+		finalized_target,
+		authorities_set_id,
+		authorities_set,
+		justification,
+		&mut StrictVerificationCallbacks,
+	)
+}
+
+/// Verification callbacks.
+trait VerificationCallbacks {
+	/// Called when we see a precommit from unknown authority.
+	fn on_unkown_authority(&mut self, precommit_idx: usize) -> Result<(), Error>;
+	/// Called when we see a precommit with duplicate vote from known authority.
+	fn on_duplicate_authority_vote(&mut self, precommit_idx: usize) -> Result<(), Error>;
+	/// Called when we see a precommit after we've collected enough votes from authorities.
+	fn on_redundant_authority_vote(&mut self, precommit_idx: usize) -> Result<(), Error>;
+}
+
+/// Verification callbacks that reject all unknown, duplicate or redundant votes.
+struct StrictVerificationCallbacks;
+
+impl VerificationCallbacks for StrictVerificationCallbacks {
+	fn on_unkown_authority(&mut self, _precommit_idx: usize) -> Result<(), Error> {
+		Err(Error::UnknownAuthorityVote)
+	}
+
+	fn on_duplicate_authority_vote(&mut self, _precommit_idx: usize) -> Result<(), Error> {
+		Err(Error::DuplicateAuthorityVote)
+	}
+
+	fn on_redundant_authority_vote(&mut self, _precommit_idx: usize) -> Result<(), Error> {
+		Err(Error::RedundantVotesInJustification)
+	}
+}
+
+/// Verification callbacks for justification optimization.
+struct OptimizationCallbacks(Vec<usize>);
+
+impl OptimizationCallbacks {
+	fn optimize<Header: HeaderT>(
+		self,
+		mut justification: GrandpaJustification<Header>,
+	) -> GrandpaJustification<Header> {
+		for invalid_precommit_idx in self.0.into_iter().rev() {
+			justification.commit.precommits.remove(invalid_precommit_idx);
+		}
+		justification
+	}
+}
+
+impl VerificationCallbacks for OptimizationCallbacks {
+	fn on_unkown_authority(&mut self, precommit_idx: usize) -> Result<(), Error> {
+		self.0.push(precommit_idx);
+		Ok(())
+	}
+
+	fn on_duplicate_authority_vote(&mut self, precommit_idx: usize) -> Result<(), Error> {
+		self.0.push(precommit_idx);
+		Ok(())
+	}
+
+	fn on_redundant_authority_vote(&mut self, precommit_idx: usize) -> Result<(), Error> {
+		self.0.push(precommit_idx);
+		Ok(())
+	}
+}
+
+/// Verify that justification, that is generated by given authority set, finalizes given header.
+fn verify_justification_with_callbacks<Header: HeaderT, C: VerificationCallbacks>(
+	finalized_target: (Header::Hash, Header::Number),
+	authorities_set_id: SetId,
+	authorities_set: &VoterSet<AuthorityId>,
+	justification: &GrandpaJustification<Header>,
+	callbacks: &mut C,
+) -> Result<(), Error>
+where
+	Header::Number: finality_grandpa::BlockNumberOps,
+{
+	// ensure that it is justification for the expected header
+	if (justification.commit.target_hash, justification.commit.target_number) != finalized_target {
+		return Err(Error::InvalidJustificationTarget)
+	}
+
+	let threshold = authorities_set.threshold().0.into();
+	let mut chain = AncestryChain::new(&justification.votes_ancestries);
+	let mut signature_buffer = Vec::new();
+	let mut votes = BTreeSet::new();
+	let mut cumulative_weight = 0u64;
+
+	for (precommit_idx, signed) in justification.commit.precommits.iter().enumerate() {
+		// if we have collected enough precommits, we probabably want to fail/remove extra
+		// precommits
+		if cumulative_weight >= threshold {
+			callbacks.on_redundant_authority_vote(precommit_idx)?;
+			continue
+		}
+
+		// authority must be in the set
+		let authority_info = match authorities_set.get(&signed.id) {
+			Some(authority_info) => authority_info,
+			None => {
+				callbacks.on_unkown_authority(precommit_idx)?;
+				continue
+			},
+		};
+
+		// check if authority has already voted in the same round.
+		//
+		// there's a lot of code in `validate_commit` and `import_precommit` functions inside
+		// `finality-grandpa` crate (mostly related to reporting equivocations). But the only thing
+		// that we care about is that only first vote from the authority is accepted
+		if !votes.insert(signed.id.clone()) {
+			callbacks.on_duplicate_authority_vote(precommit_idx)?;
+			continue
+		}
+
+		// everything below this line can't just `continue`, because state is already altered
+
+		// precommits aren't allowed for block lower than the target
+		if signed.precommit.target_number < justification.commit.target_number {
+			return Err(Error::PrecommitIsNotCommitDescendant)
+		}
+		// all precommits must be descendants of target block
+		chain = chain
+			.ensure_descendant(&justification.commit.target_hash, &signed.precommit.target_hash)?;
+		// since we know now that the precommit target is the descendant of the justification
+		// target, we may increase 'weight' of the justification target
+		//
+		// there's a lot of code in the `VoteGraph::insert` method inside `finality-grandpa` crate,
+		// but in the end it is only used to find GHOST, which we don't care about. The only thing
+		// that we care about is that the justification target has enough weight
+		cumulative_weight = cumulative_weight.checked_add(authority_info.weight().0.into()).expect(
+			"sum of weights of ALL authorities is expected not to overflow - this is guaranteed by\
+				existence of VoterSet;\
+				the order of loop conditions guarantees that we can account vote from same authority\
+				multiple times;\
+				thus we'll never overflow the u64::MAX;\
+				qed",
+		);
+
+		// verify authority signature
+		if !sp_consensus_grandpa::check_message_signature_with_buffer(
+			&finality_grandpa::Message::Precommit(signed.precommit.clone()),
+			&signed.id,
+			&signed.signature,
+			justification.round,
+			authorities_set_id,
+			&mut signature_buffer,
+		) {
+			return Err(Error::InvalidAuthoritySignature)
+		}
+	}
+
+	// check that there are no extra headers in the justification
+	if !chain.unvisited.is_empty() {
+		return Err(Error::ExtraHeadersInVotesAncestries)
+	}
+
+	// check that the cumulative weight of validators voted for the justification target (or one
+	// of its descendents) is larger than required threshold.
+	if cumulative_weight >= threshold {
+		Ok(())
+	} else {
+		Err(Error::TooLowCumulativeWeight)
+	}
+}
+
+/// Votes ancestries with useful methods.
+#[derive(RuntimeDebug)]
+pub struct AncestryChain<Header: HeaderT> {
+	/// Header hash => parent header hash mapping.
+	pub parents: BTreeMap<Header::Hash, Header::Hash>,
+	/// Hashes of headers that were not visited by `is_ancestor` method.
+	pub unvisited: BTreeSet<Header::Hash>,
+}
+
+impl<Header: HeaderT> AncestryChain<Header> {
+	/// Create new ancestry chain.
+	pub fn new(ancestry: &[Header]) -> AncestryChain<Header> {
+		let mut parents = BTreeMap::new();
+		let mut unvisited = BTreeSet::new();
+		for ancestor in ancestry {
+			let hash = ancestor.hash();
+			let parent_hash = *ancestor.parent_hash();
+			parents.insert(hash, parent_hash);
+			unvisited.insert(hash);
+		}
+		AncestryChain { parents, unvisited }
+	}
+
+	/// Returns `Ok(_)` if `precommit_target` is a descendant of the `commit_target` block and
+	/// `Err(_)` otherwise.
+	pub fn ensure_descendant(
+		mut self,
+		commit_target: &Header::Hash,
+		precommit_target: &Header::Hash,
+	) -> Result<Self, Error> {
+		let mut current_hash = *precommit_target;
+		loop {
+			if current_hash == *commit_target {
+				break
+			}
+
+			let is_visited_before = !self.unvisited.remove(&current_hash);
+			current_hash = match self.parents.get(&current_hash) {
+				Some(parent_hash) => {
+					if is_visited_before {
+						// `Some(parent_hash)` means that the `current_hash` is in the `parents`
+						// container `is_visited_before` means that it has been visited before in
+						// some of previous calls => since we assume that previous call has finished
+						// with `true`, this also will be finished with `true`
+						return Ok(self)
+					}
+
+					*parent_hash
+				},
+				None => return Err(Error::PrecommitIsNotCommitDescendant),
+			};
+		}
+		Ok(self)
+	}
+}