Adds Snowbridge to Rococo runtime (#2522)

# Description

Adds Snowbridge to the Rococo bridge hub runtime. Includes config
changes required in Rococo asset hub.

---------

Co-authored-by: Alistair Singh <alistair.singh7@gmail.com>
Co-authored-by: ron <yrong1997@gmail.com>
Co-authored-by: Vincent Geddes <vincent.geddes@hey.com>
Co-authored-by: claravanstaden <Cats 4 life!>

bridges/snowbridge/parachain/pallets/outbound-queue/Cargo.toml

@@ -0,0 +1,78 @@
+[package]
+name = "snowbridge-outbound-queue"
+description = "Snowbridge Outbound Queue"
+version = "0.1.1"
+edition = "2021"
+authors = ["Snowfork <contact@snowfork.com>"]
+repository = "https://github.com/Snowfork/snowbridge"
+license = "Apache-2.0"
+
+[package.metadata.docs.rs]
+targets = ["x86_64-unknown-linux-gnu"]
+
+[dependencies]
+serde = { version = "1.0.188", features = ["alloc", "derive"], default-features = false }
+codec = { version = "3.6.1", package = "parity-scale-codec", default-features = false, features = ["derive"] }
+scale-info = { version = "2.9.0", default-features = false, features = ["derive"] }
+hex-literal = { version = "0.4.1", optional = true }
+
+frame-benchmarking = { path = "../../../../../substrate/frame/benchmarking", default-features = false, optional = true }
+frame-support = { path = "../../../../../substrate/frame/support", default-features = false }
+frame-system = { path = "../../../../../substrate/frame/system", default-features = false }
+sp-core = { path = "../../../../../substrate/primitives/core", default-features = false }
+sp-std = { path = "../../../../../substrate/primitives/std", default-features = false }
+sp-runtime = { path = "../../../../../substrate/primitives/runtime", default-features = false }
+sp-io = { path = "../../../../../substrate/primitives/io", default-features = false }
+sp-arithmetic = { path = "../../../../../substrate/primitives/arithmetic", default-features = false }
+
+bridge-hub-common = { path = "../../../../../cumulus/parachains/runtimes/bridge-hubs/common", default-features = false }
+
+snowbridge-core = { path = "../../primitives/core", features = ["serde"], default-features = false }
+snowbridge-outbound-queue-merkle-tree = { path = "merkle-tree", default-features = false }
+ethabi = { git = "https://github.com/snowfork/ethabi-decode.git", package = "ethabi-decode", branch = "master", default-features = false }
+
+xcm = { package = "staging-xcm", path = "../../../../../polkadot/xcm", default-features = false }
+
+[dev-dependencies]
+pallet-message-queue = { path = "../../../../../substrate/frame/message-queue", default-features = false }
+sp-keyring = { path = "../../../../../substrate/primitives/keyring" }
+hex-literal = { version = "0.4.1" }
+
+[features]
+default = ["std"]
+std = [
+	"bridge-hub-common/std",
+	"codec/std",
+	"ethabi/std",
+	"frame-benchmarking/std",
+	"frame-support/std",
+	"frame-system/std",
+	"pallet-message-queue/std",
+	"scale-info/std",
+	"serde/std",
+	"snowbridge-core/std",
+	"snowbridge-outbound-queue-merkle-tree/std",
+	"sp-arithmetic/std",
+	"sp-core/std",
+	"sp-io/std",
+	"sp-runtime/std",
+	"sp-std/std",
+	"xcm/std",
+]
+runtime-benchmarks = [
+	"bridge-hub-common/runtime-benchmarks",
+	"frame-benchmarking",
+	"frame-benchmarking/runtime-benchmarks",
+	"frame-support/runtime-benchmarks",
+	"frame-system/runtime-benchmarks",
+	"hex-literal",
+	"pallet-message-queue/runtime-benchmarks",
+	"snowbridge-core/runtime-benchmarks",
+	"sp-runtime/runtime-benchmarks",
+]
+try-runtime = [
+	"frame-support/try-runtime",
+	"frame-system/try-runtime",
+	"pallet-message-queue/try-runtime",
+	"sp-runtime/try-runtime",
+]

bridges/snowbridge/parachain/pallets/outbound-queue/merkle-tree/Cargo.toml

@@ -0,0 +1,33 @@
+[package]
+name = "snowbridge-outbound-queue-merkle-tree"
+description = "Snowbridge Outbound Queue Merkle Tree"
+version = "0.1.1"
+edition = "2021"
+authors = ["Snowfork <contact@snowfork.com>"]
+repository = "https://github.com/Snowfork/snowbridge"
+license = "Apache-2.0"
+
+[package.metadata.docs.rs]
+targets = ["x86_64-unknown-linux-gnu"]
+
+[dependencies]
+codec = { version = "3.1.5", package = "parity-scale-codec", default-features = false, features = ["derive"] }
+scale-info = { version = "2.7.0", default-features = false, features = ["derive"] }
+
+sp-core = { path = "../../../../../../substrate/primitives/core", default-features = false }
+sp-runtime = { path = "../../../../../../substrate/primitives/runtime", default-features = false }
+
+[dev-dependencies]
+hex-literal = { version = "0.4.1" }
+env_logger = "0.9"
+hex = "0.4"
+array-bytes = "4.1"
+
+[features]
+default = ["std"]
+std = [
+	"codec/std",
+	"scale-info/std",
+	"sp-core/std",
+	"sp-runtime/std",
+]

bridges/snowbridge/parachain/pallets/outbound-queue/merkle-tree/src/lib.rs

@@ -0,0 +1,464 @@
+// SPDX-License-Identifier: Apache-2.0
+// SPDX-FileCopyrightText: 2023 Snowfork <hello@snowfork.com>
+// SPDX-FileCopyrightText: 2021-2022 Parity Technologies (UK) Ltd.
+#![cfg_attr(not(feature = "std"), no_std)]
+#![warn(missing_docs)]
+
+//! This crate implements a simple binary Merkle Tree utilities required for inter-op with Ethereum
+//! bridge & Solidity contract.
+//!
+//! The implementation is optimised for usage within Substrate Runtime and supports no-std
+//! compilation targets.
+//!
+//! Merkle Tree is constructed from arbitrary-length leaves, that are initially hashed using the
+//! same `\[`Hasher`\]` as the inner nodes.
+//! Inner nodes are created by concatenating child hashes and hashing again. The implementation
+//! does not perform any sorting of the input data (leaves) nor when inner nodes are created.
+//!
+//! If the number of leaves is not even, last leaf (hash of) is promoted to the upper layer.
+
+#[cfg(not(feature = "std"))]
+extern crate alloc;
+#[cfg(not(feature = "std"))]
+use alloc::vec;
+#[cfg(not(feature = "std"))]
+use alloc::vec::Vec;
+
+use codec::{Decode, Encode};
+use scale_info::TypeInfo;
+use sp_core::{RuntimeDebug, H256};
+use sp_runtime::traits::Hash;
+
+/// Construct a root hash of a Binary Merkle Tree created from given leaves.
+///
+/// See crate-level docs for details about Merkle Tree construction.
+///
+/// In case an empty list of leaves is passed the function returns a 0-filled hash.
+pub fn merkle_root<H, I>(leaves: I) -> H256
+where
+	H: Hash<Output = H256>,
+	I: Iterator<Item = H256>,
+{
+	merkelize::<H, _, _>(leaves, &mut ())
+}
+
+fn merkelize<H, V, I>(leaves: I, visitor: &mut V) -> H256
+where
+	H: Hash<Output = H256>,
+	V: Visitor,
+	I: Iterator<Item = H256>,
+{
+	let upper = Vec::with_capacity(leaves.size_hint().0);
+	let mut next = match merkelize_row::<H, _, _>(leaves, upper, visitor) {
+		Ok(root) => return root,
+		Err(next) if next.is_empty() => return H256::default(),
+		Err(next) => next,
+	};
+
+	let mut upper = Vec::with_capacity((next.len() + 1) / 2);
+	loop {
+		visitor.move_up();
+
+		match merkelize_row::<H, _, _>(next.drain(..), upper, visitor) {
+			Ok(root) => return root,
+			Err(t) => {
+				// swap collections to avoid allocations
+				upper = next;
+				next = t;
+			},
+		};
+	}
+}
+
+/// A generated merkle proof.
+///
+/// The structure contains all necessary data to later on verify the proof and the leaf itself.
+#[derive(Encode, Decode, RuntimeDebug, PartialEq, Eq, TypeInfo)]
+pub struct MerkleProof {
+	/// Root hash of generated merkle tree.
+	pub root: H256,
+	/// Proof items (does not contain the leaf hash, nor the root obviously).
+	///
+	/// This vec contains all inner node hashes necessary to reconstruct the root hash given the
+	/// leaf hash.
+	pub proof: Vec<H256>,
+	/// Number of leaves in the original tree.
+	///
+	/// This is needed to detect a case where we have an odd number of leaves that "get promoted"
+	/// to upper layers.
+	pub number_of_leaves: u64,
+	/// Index of the leaf the proof is for (0-based).
+	pub leaf_index: u64,
+	/// Leaf content (hashed).
+	pub leaf: H256,
+}
+
+/// A trait of object inspecting merkle root creation.
+///
+/// It can be passed to [`merkelize_row`] or [`merkelize`] functions and will be notified
+/// about tree traversal.
+trait Visitor {
+	/// We are moving one level up in the tree.
+	fn move_up(&mut self);
+
+	/// We are creating an inner node from given `left` and `right` nodes.
+	///
+	/// Note that in case of last odd node in the row `right` might be empty.
+	/// The method will also visit the `root` hash (level 0).
+	///
+	/// The `index` is an index of `left` item.
+	fn visit(&mut self, index: u64, left: &Option<H256>, right: &Option<H256>);
+}
+
+/// No-op implementation of the visitor.
+impl Visitor for () {
+	fn move_up(&mut self) {}
+	fn visit(&mut self, _index: u64, _left: &Option<H256>, _right: &Option<H256>) {}
+}
+
+/// Construct a Merkle Proof for leaves given by indices.
+///
+/// The function constructs a (partial) Merkle Tree first and stores all elements required
+/// to prove the requested item (leaf) given the root hash.
+///
+/// Both the Proof and the Root Hash are returned.
+///
+/// # Panic
+///
+/// The function will panic if given `leaf_index` is greater than the number of leaves.
+pub fn merkle_proof<H, I>(leaves: I, leaf_index: u64) -> MerkleProof
+where
+	H: Hash<Output = H256>,
+	I: Iterator<Item = H256>,
+{
+	let mut leaf = None;
+	let mut hashes = vec![];
+	let mut number_of_leaves = 0;
+	for (idx, l) in (0u64..).zip(leaves) {
+		// count the leaves
+		number_of_leaves = idx + 1;
+		hashes.push(l);
+		// find the leaf for the proof
+		if idx == leaf_index {
+			leaf = Some(l);
+		}
+	}
+
+	/// The struct collects a proof for single leaf.
+	struct ProofCollection {
+		proof: Vec<H256>,
+		position: u64,
+	}
+
+	impl ProofCollection {
+		fn new(position: u64) -> Self {
+			ProofCollection { proof: Default::default(), position }
+		}
+	}
+
+	impl Visitor for ProofCollection {
+		fn move_up(&mut self) {
+			self.position /= 2;
+		}
+
+		fn visit(&mut self, index: u64, left: &Option<H256>, right: &Option<H256>) {
+			// we are at left branch - right goes to the proof.
+			if self.position == index {
+				if let Some(right) = right {
+					self.proof.push(*right);
+				}
+			}
+			// we are at right branch - left goes to the proof.
+			if self.position == index + 1 {
+				if let Some(left) = left {
+					self.proof.push(*left);
+				}
+			}
+		}
+	}
+
+	let mut collect_proof = ProofCollection::new(leaf_index);
+
+	let root = merkelize::<H, _, _>(hashes.into_iter(), &mut collect_proof);
+	let leaf = leaf.expect("Requested `leaf_index` is greater than number of leaves.");
+
+	#[cfg(feature = "debug")]
+	log::debug!(
+		"[merkle_proof] Proof: {:?}",
+		collect_proof.proof.iter().map(hex::encode).collect::<Vec<_>>()
+	);
+
+	MerkleProof { root, proof: collect_proof.proof, number_of_leaves, leaf_index, leaf }
+}
+
+/// Leaf node for proof verification.
+///
+/// Can be either a value that needs to be hashed first,
+/// or the hash itself.
+#[derive(Debug, PartialEq, Eq)]
+pub enum Leaf<'a> {
+	/// Leaf content.
+	Value(&'a [u8]),
+	/// Hash of the leaf content.
+	Hash(H256),
+}
+
+impl<'a, T: AsRef<[u8]>> From<&'a T> for Leaf<'a> {
+	fn from(v: &'a T) -> Self {
+		Leaf::Value(v.as_ref())
+	}
+}
+
+impl<'a> From<H256> for Leaf<'a> {
+	fn from(v: H256) -> Self {
+		Leaf::Hash(v)
+	}
+}
+
+/// Verify Merkle Proof correctness versus given root hash.
+///
+/// The proof is NOT expected to contain leaf hash as the first
+/// element, but only all adjacent nodes required to eventually by process of
+/// concatenating and hashing end up with given root hash.
+///
+/// The proof must not contain the root hash.
+pub fn verify_proof<'a, H, P, L>(
+	root: &'a H256,
+	proof: P,
+	number_of_leaves: u64,
+	leaf_index: u64,
+	leaf: L,
+) -> bool
+where
+	H: Hash<Output = H256>,
+	P: IntoIterator<Item = H256>,
+	L: Into<Leaf<'a>>,
+{
+	if leaf_index >= number_of_leaves {
+		return false
+	}
+
+	let leaf_hash = match leaf.into() {
+		Leaf::Value(content) => <H as Hash>::hash(content),
+		Leaf::Hash(hash) => hash,
+	};
+
+	let hash_len = <H as sp_core::Hasher>::LENGTH;
+	let mut combined = [0_u8; 64];
+	let computed = proof.into_iter().fold(leaf_hash, |a, b| {
+		if a < b {
+			combined[..hash_len].copy_from_slice(a.as_ref());
+			combined[hash_len..].copy_from_slice(b.as_ref());
+		} else {
+			combined[..hash_len].copy_from_slice(b.as_ref());
+			combined[hash_len..].copy_from_slice(a.as_ref());
+		}
+		<H as Hash>::hash(&combined)
+	});
+
+	root == &computed
+}
+
+/// Processes a single row (layer) of a tree by taking pairs of elements,
+/// concatenating them, hashing and placing into resulting vector.
+///
+/// In case only one element is provided it is returned via `Ok` result, in any other case (also an
+/// empty iterator) an `Err` with the inner nodes of upper layer is returned.
+fn merkelize_row<H, V, I>(
+	mut iter: I,
+	mut next: Vec<H256>,
+	visitor: &mut V,
+) -> Result<H256, Vec<H256>>
+where
+	H: Hash<Output = H256>,
+	V: Visitor,
+	I: Iterator<Item = H256>,
+{
+	#[cfg(feature = "debug")]
+	log::debug!("[merkelize_row]");
+	next.clear();
+
+	let hash_len = <H as sp_core::Hasher>::LENGTH;
+	let mut index = 0;
+	let mut combined = vec![0_u8; hash_len * 2];
+	loop {
+		let a = iter.next();
+		let b = iter.next();
+		visitor.visit(index, &a, &b);
+
+		#[cfg(feature = "debug")]
+		log::debug!("  {:?}\n  {:?}", a.as_ref().map(hex::encode), b.as_ref().map(hex::encode));
+
+		index += 2;
+		match (a, b) {
+			(Some(a), Some(b)) => {
+				if a < b {
+					combined[..hash_len].copy_from_slice(a.as_ref());
+					combined[hash_len..].copy_from_slice(b.as_ref());
+				} else {
+					combined[..hash_len].copy_from_slice(b.as_ref());
+					combined[hash_len..].copy_from_slice(a.as_ref());
+				}
+
+				next.push(<H as Hash>::hash(&combined));
+			},
+			// Odd number of items. Promote the item to the upper layer.
+			(Some(a), None) if !next.is_empty() => {
+				next.push(a);
+			},
+			// Last item = root.
+			(Some(a), None) => return Ok(a),
+			// Finish up, no more items.
+			_ => {
+				#[cfg(feature = "debug")]
+				log::debug!(
+					"[merkelize_row] Next: {:?}",
+					next.iter().map(hex::encode).collect::<Vec<_>>()
+				);
+				return Err(next)
+			},
+		}
+	}
+}
+
+#[cfg(test)]
+mod tests {
+	use super::*;
+	use hex_literal::hex;
+	use sp_core::keccak_256;
+	use sp_runtime::traits::Keccak256;
+
+	fn make_leaves(count: u64) -> Vec<H256> {
+		(0..count).map(|i| keccak_256(&i.to_le_bytes()).into()).collect()
+	}
+
+	#[test]
+	fn should_generate_empty_root() {
+		// given
+		let _ = env_logger::try_init();
+		let data = vec![];
+
+		// when
+		let out = merkle_root::<Keccak256, _>(data.into_iter());
+
+		// then
+		assert_eq!(
+			hex::encode(out),
+			"0000000000000000000000000000000000000000000000000000000000000000"
+		);
+	}
+
+	#[test]
+	fn should_generate_single_root() {
+		// given
+		let _ = env_logger::try_init();
+		let data = make_leaves(1);
+
+		// when
+		let out = merkle_root::<Keccak256, _>(data.into_iter());
+
+		// then
+		assert_eq!(
+			hex::encode(out),
+			"011b4d03dd8c01f1049143cf9c4c817e4b167f1d1b83e5c6f0f10d89ba1e7bce"
+		);
+	}
+
+	#[test]
+	fn should_generate_root_pow_2() {
+		// given
+		let _ = env_logger::try_init();
+		let data = make_leaves(2);
+
+		// when
+		let out = merkle_root::<Keccak256, _>(data.into_iter());
+
+		// then
+		assert_eq!(
+			hex::encode(out),
+			"e497bd1c13b13a60af56fa0d2703517c232fde213ad20d2c3dd60735c6604512"
+		);
+	}
+
+	#[test]
+	fn should_generate_root_complex() {
+		let _ = env_logger::try_init();
+		let test = |root, data: Vec<H256>| {
+			assert_eq!(
+				array_bytes::bytes2hex("", merkle_root::<Keccak256, _>(data.into_iter()).as_ref()),
+				root
+			);
+		};
+
+		test("816cc37bd8d39f7b0851838ebc875faf2afe58a03e95aca3b1333b3693f39dd3", make_leaves(3));
+
+		test("7501ea976cb92f305cca65ab11254589ea28bb8b59d3161506350adaa237d22f", make_leaves(4));
+
+		test("d26ba4eb398747bdd39255b1fadb99b803ce39696021b3b0bff7301ac146ee4e", make_leaves(10));
+	}
+
+	#[test]
+	#[ignore]
+	fn should_generate_and_verify_proof() {
+		// given
+		let _ = env_logger::try_init();
+		let data: Vec<H256> = make_leaves(3);
+
+		// when
+		let proof0 = merkle_proof::<Keccak256, _>(data.clone().into_iter(), 0);
+		assert!(verify_proof::<Keccak256, _, _>(
+			&proof0.root,
+			proof0.proof.clone(),
+			data.len() as u64,
+			proof0.leaf_index,
+			&data[0],
+		));
+
+		let proof1 = merkle_proof::<Keccak256, _>(data.clone().into_iter(), 1);
+		assert!(verify_proof::<Keccak256, _, _>(
+			&proof1.root,
+			proof1.proof,
+			data.len() as u64,
+			proof1.leaf_index,
+			&proof1.leaf,
+		));
+
+		let proof2 = merkle_proof::<Keccak256, _>(data.clone().into_iter(), 2);
+		assert!(verify_proof::<Keccak256, _, _>(
+			&proof2.root,
+			proof2.proof,
+			data.len() as u64,
+			proof2.leaf_index,
+			&proof2.leaf
+		));
+
+		// then
+		assert_eq!(hex::encode(proof0.root), hex::encode(proof1.root));
+		assert_eq!(hex::encode(proof2.root), hex::encode(proof1.root));
+
+		assert!(!verify_proof::<Keccak256, _, _>(
+			&H256::from_slice(&hex!(
+				"fb3b3be94be9e983ba5e094c9c51a7d96a4fa2e5d8e891df00ca89ba05bb1239"
+			)),
+			proof0.proof,
+			data.len() as u64,
+			proof0.leaf_index,
+			&proof0.leaf
+		));
+
+		assert!(!verify_proof::<Keccak256, _, _>(
+			&proof0.root,
+			vec![],
+			data.len() as u64,
+			proof0.leaf_index,
+			&proof0.leaf
+		));
+	}
+
+	#[test]
+	#[should_panic]
+	fn should_panic_on_invalid_leaf_index() {
+		let _ = env_logger::try_init();
+		merkle_proof::<Keccak256, _>(make_leaves(1).into_iter(), 5);
+	}
+}

bridges/snowbridge/parachain/pallets/outbound-queue/runtime-api/Cargo.toml

@@ -0,0 +1,34 @@
+[package]
+name = "snowbridge-outbound-queue-runtime-api"
+description = "Snowbridge Outbound Queue Runtime API"
+version = "0.1.0"
+edition = "2021"
+authors = ["Snowfork <contact@snowfork.com>"]
+repository = "https://github.com/Snowfork/snowbridge"
+license = "Apache-2.0"
+
+[package.metadata.docs.rs]
+targets = ["x86_64-unknown-linux-gnu"]
+
+[dependencies]
+codec = { version = "3.1.5", package = "parity-scale-codec", features = ["derive"], default-features = false }
+sp-core = { path = "../../../../../../substrate/primitives/core", default-features = false }
+sp-std = { path = "../../../../../../substrate/primitives/std", default-features = false }
+sp-api = { path = "../../../../../../substrate/primitives/api", default-features = false }
+frame-support = { path = "../../../../../../substrate/frame/support", default-features = false }
+xcm = { package = "staging-xcm", path = "../../../../../../polkadot/xcm", default-features = false }
+snowbridge-outbound-queue-merkle-tree = { path = "../merkle-tree", default-features = false }
+snowbridge-core = { path = "../../../primitives/core", default-features = false }
+
+[features]
+default = ["std"]
+std = [
+	"codec/std",
+	"frame-support/std",
+	"snowbridge-core/std",
+	"snowbridge-outbound-queue-merkle-tree/std",
+	"sp-api/std",
+	"sp-core/std",
+	"sp-std/std",
+	"xcm/std",
+]

bridges/snowbridge/parachain/pallets/outbound-queue/runtime-api/src/lib.rs

@@ -0,0 +1,20 @@
+// SPDX-License-Identifier: Apache-2.0
+// SPDX-FileCopyrightText: 2023 Snowfork <hello@snowfork.com>
+#![cfg_attr(not(feature = "std"), no_std)]
+
+use frame_support::traits::tokens::Balance as BalanceT;
+use snowbridge_core::outbound::Message;
+use snowbridge_outbound_queue_merkle_tree::MerkleProof;
+
+sp_api::decl_runtime_apis! {
+	pub trait OutboundQueueApi<Balance> where Balance: BalanceT
+	{
+		/// Generate a merkle proof for a committed message identified by `leaf_index`.
+		/// The merkle root is stored in the block header as a
+		/// `\[`sp_runtime::generic::DigestItem::Other`\]`
+		fn prove_message(leaf_index: u64) -> Option<MerkleProof>;
+
+		/// Calculate the delivery fee for `message`
+		fn calculate_fee(message: Message) -> Option<Balance>;
+	}
+}

bridges/snowbridge/parachain/pallets/outbound-queue/src/api.rs

@@ -0,0 +1,30 @@
+// SPDX-License-Identifier: Apache-2.0
+// SPDX-FileCopyrightText: 2023 Snowfork <hello@snowfork.com>
+//! Helpers for implementing runtime api
+
+use crate::{Config, MessageLeaves};
+use frame_support::storage::StorageStreamIter;
+use snowbridge_core::outbound::{Message, SendMessage};
+use snowbridge_outbound_queue_merkle_tree::{merkle_proof, MerkleProof};
+
+pub fn prove_message<T>(leaf_index: u64) -> Option<MerkleProof>
+where
+	T: Config,
+{
+	if !MessageLeaves::<T>::exists() {
+		return None
+	}
+	let proof =
+		merkle_proof::<<T as Config>::Hashing, _>(MessageLeaves::<T>::stream_iter(), leaf_index);
+	Some(proof)
+}
+
+pub fn calculate_fee<T>(message: Message) -> Option<T::Balance>
+where
+	T: Config,
+{
+	match crate::Pallet::<T>::validate(&message) {
+		Ok((_, fees)) => Some(fees.total()),
+		_ => None,
+	}
+}

bridges/snowbridge/parachain/pallets/outbound-queue/src/benchmarking.rs

@@ -0,0 +1,85 @@
+// SPDX-License-Identifier: Apache-2.0
+// SPDX-FileCopyrightText: 2023 Snowfork <hello@snowfork.com>
+use super::*;
+
+use bridge_hub_common::AggregateMessageOrigin;
+use codec::Encode;
+use frame_benchmarking::v2::*;
+use snowbridge_core::{
+	outbound::{Command, Initializer},
+	ChannelId,
+};
+use sp_core::{H160, H256};
+
+#[allow(unused_imports)]
+use crate::Pallet as OutboundQueue;
+
+#[benchmarks(
+	where
+		<T as Config>::MaxMessagePayloadSize: Get<u32>,
+)]
+mod benchmarks {
+	use super::*;
+
+	/// Benchmark for processing a message.
+	#[benchmark]
+	fn do_process_message() -> Result<(), BenchmarkError> {
+		let enqueued_message = QueuedMessage {
+			id: H256::zero(),
+			channel_id: ChannelId::from([1; 32]),
+			command: Command::Upgrade {
+				impl_address: H160::zero(),
+				impl_code_hash: H256::zero(),
+				initializer: Some(Initializer {
+					params: [7u8; 256].into_iter().collect(),
+					maximum_required_gas: 200_000,
+				}),
+			},
+		};
+		let origin = AggregateMessageOrigin::Snowbridge([1; 32].into());
+		let encoded_enqueued_message = enqueued_message.encode();
+
+		#[block]
+		{
+			let _ = OutboundQueue::<T>::do_process_message(origin, &encoded_enqueued_message);
+		}
+
+		assert_eq!(MessageLeaves::<T>::decode_len().unwrap(), 1);
+
+		Ok(())
+	}
+
+	/// Benchmark for producing final messages commitment
+	#[benchmark]
+	fn commit() -> Result<(), BenchmarkError> {
+		// Assume worst case, where `MaxMessagesPerBlock` messages need to be committed.
+		for i in 0..T::MaxMessagesPerBlock::get() {
+			let leaf_data: [u8; 1] = [i as u8];
+			let leaf = <T as Config>::Hashing::hash(&leaf_data);
+			MessageLeaves::<T>::append(leaf);
+		}
+
+		#[block]
+		{
+			OutboundQueue::<T>::commit();
+		}
+
+		Ok(())
+	}
+
+	/// Benchmark for producing commitment for a single message
+	#[benchmark]
+	fn commit_single() -> Result<(), BenchmarkError> {
+		let leaf = <T as Config>::Hashing::hash(&[100; 1]);
+		MessageLeaves::<T>::append(leaf);
+
+		#[block]
+		{
+			OutboundQueue::<T>::commit();
+		}
+
+		Ok(())
+	}
+
+	impl_benchmark_test_suite!(OutboundQueue, crate::mock::new_tester(), crate::mock::Test,);
+}

bridges/snowbridge/parachain/pallets/outbound-queue/src/lib.rs

@@ -0,0 +1,413 @@
+// SPDX-License-Identifier: Apache-2.0
+// SPDX-FileCopyrightText: 2023 Snowfork <hello@snowfork.com>
+//! Pallet for committing outbound messages for delivery to Ethereum
+//!
+//! # Overview
+//!
+//! Messages come either from sibling parachains via XCM, or BridgeHub itself
+//! via the `snowbridge-system` pallet:
+//!
+//! 1. `snowbridge_router_primitives::outbound::EthereumBlobExporter::deliver`
+//! 2. `snowbridge_system::Pallet::send`
+//!
+//! The message submission pipeline works like this:
+//! 1. The message is first validated via the implementation for
+//!    [`snowbridge_core::outbound::SendMessage::validate`]
+//! 2. The message is then enqueued for later processing via the implementation for
+//!    [`snowbridge_core::outbound::SendMessage::deliver`]
+//! 3. The underlying message queue is implemented by [`Config::MessageQueue`]
+//! 4. The message queue delivers messages back to this pallet via the implementation for
+//!    [`frame_support::traits::ProcessMessage::process_message`]
+//! 5. The message is processed in `Pallet::do_process_message`: a. Assigned a nonce b. ABI-encoded,
+//!    hashed, and stored in the `MessageLeaves` vector
+//! 6. At the end of the block, a merkle root is constructed from all the leaves in `MessageLeaves`.
+//! 7. This merkle root is inserted into the parachain header as a digest item
+//! 8. Offchain relayers are able to relay the message to Ethereum after: a. Generating a merkle
+//!    proof for the committed message using the `prove_message` runtime API b. Reading the actual
+//!    message content from the `Messages` vector in storage
+//!
+//! On the Ethereum side, the message root is ultimately the thing being
+//! verified by the Polkadot light client.
+//!
+//! # Message Priorities
+//!
+//! The processing of governance commands can never be halted. This effectively
+//! allows us to pause processing of normal user messages while still allowing
+//! governance commands to be sent to Ethereum.
+//!
+//! # Fees
+//!
+//! An upfront fee must be paid for delivering a message. This fee covers several
+//! components:
+//! 1. The weight of processing the message locally
+//! 2. The gas refund paid out to relayers for message submission
+//! 3. An additional reward paid out to relayers for message submission
+//!
+//! Messages are weighed to determine the maximum amount of gas they could
+//! consume on Ethereum. Using this upper bound, a final fee can be calculated.
+//!
+//! The fee calculation also requires the following parameters:
+//! * ETH/DOT exchange rate
+//! * Ether fee per unit of gas
+//!
+//! By design, it is expected that governance should manually update these
+//! parameters every few weeks using the `set_pricing_parameters` extrinsic in the
+//! system pallet.
+//!
+//! ## Fee Computation Function
+//!
+//! ```text
+//! LocalFee(Message) = WeightToFee(ProcessMessageWeight(Message))
+//! RemoteFee(Message) = MaxGasRequired(Message) * FeePerGas + Reward
+//! Fee(Message) = LocalFee(Message) + (RemoteFee(Message) / Ratio("ETH/DOT"))
+//! ```
+//!
+//! By design, the computed fee is always going to conservative, to cover worst-case
+//! costs of dispatch on Ethereum. In future iterations of the design, we will optimize
+//! this, or provide a mechanism to asynchronously refund a portion of collected fees.
+//!
+//! # Extrinsics
+//!
+//! * [`Call::set_operating_mode`]: Set the operating mode
+//!
+//! # Runtime API
+//!
+//! * `prove_message`: Generate a merkle proof for a committed message
+//! * `calculate_fee`: Calculate the delivery fee for a message
+#![cfg_attr(not(feature = "std"), no_std)]
+pub mod api;
+pub mod process_message_impl;
+pub mod send_message_impl;
+pub mod types;
+pub mod weights;
+
+#[cfg(feature = "runtime-benchmarks")]
+mod benchmarking;
+
+#[cfg(test)]
+mod mock;
+
+#[cfg(test)]
+mod test;
+
+use bridge_hub_common::{AggregateMessageOrigin, CustomDigestItem};
+use codec::Decode;
+use frame_support::{
+	storage::StorageStreamIter,
+	traits::{tokens::Balance, Contains, Defensive, EnqueueMessage, Get, ProcessMessageError},
+	weights::{Weight, WeightToFee},
+};
+use snowbridge_core::{
+	outbound::{Fee, GasMeter, QueuedMessage, VersionedQueuedMessage, ETHER_DECIMALS},
+	BasicOperatingMode, ChannelId,
+};
+use snowbridge_outbound_queue_merkle_tree::merkle_root;
+pub use snowbridge_outbound_queue_merkle_tree::MerkleProof;
+use sp_core::{H256, U256};
+use sp_runtime::{
+	traits::{CheckedDiv, Hash},
+	DigestItem,
+};
+use sp_std::prelude::*;
+pub use types::{CommittedMessage, FeeConfigRecord, ProcessMessageOriginOf};
+pub use weights::WeightInfo;
+
+pub use pallet::*;
+
+#[frame_support::pallet]
+pub mod pallet {
+	use super::*;
+	use frame_support::pallet_prelude::*;
+	use frame_system::pallet_prelude::*;
+	use snowbridge_core::PricingParameters;
+	use sp_arithmetic::FixedU128;
+
+	#[pallet::pallet]
+	pub struct Pallet<T>(_);
+
+	#[pallet::config]
+	pub trait Config: frame_system::Config {
+		type RuntimeEvent: From<Event<Self>> + IsType<<Self as frame_system::Config>::RuntimeEvent>;
+
+		type Hashing: Hash<Output = H256>;
+
+		type MessageQueue: EnqueueMessage<AggregateMessageOrigin>;
+
+		/// Measures the maximum gas used to execute a command on Ethereum
+		type GasMeter: GasMeter;
+
+		type Balance: Balance + From<u128>;
+
+		/// Number of decimal places in native currency
+		#[pallet::constant]
+		type Decimals: Get<u8>;
+
+		/// Max bytes in a message payload
+		#[pallet::constant]
+		type MaxMessagePayloadSize: Get<u32>;
+
+		/// Max number of messages processed per block
+		#[pallet::constant]
+		type MaxMessagesPerBlock: Get<u32>;
+
+		/// Check whether a channel exists
+		type Channels: Contains<ChannelId>;
+
+		type PricingParameters: Get<PricingParameters<Self::Balance>>;
+
+		/// Convert a weight value into a deductible fee based.
+		type WeightToFee: WeightToFee<Balance = Self::Balance>;
+
+		/// Weight information for extrinsics in this pallet
+		type WeightInfo: WeightInfo;
+	}
+
+	#[pallet::event]
+	#[pallet::generate_deposit(pub(super) fn deposit_event)]
+	pub enum Event<T: Config> {
+		/// Message has been queued and will be processed in the future
+		MessageQueued {
+			/// ID of the message. Usually the XCM message hash or a SetTopic.
+			id: H256,
+		},
+		/// Message will be committed at the end of current block. From now on, to track the
+		/// progress the message, use the `nonce` of `id`.
+		MessageAccepted {
+			/// ID of the message
+			id: H256,
+			/// The nonce assigned to this message
+			nonce: u64,
+		},
+		/// Some messages have been committed
+		MessagesCommitted {
+			/// Merkle root of the committed messages
+			root: H256,
+			/// number of committed messages
+			count: u64,
+		},
+		/// Set OperatingMode
+		OperatingModeChanged {
+			mode: BasicOperatingMode,
+		},
+		FeeConfigChanged {
+			fee_config: FeeConfigRecord,
+		},
+	}
+
+	#[pallet::error]
+	pub enum Error<T> {
+		/// The message is too large
+		MessageTooLarge,
+		/// The pallet is halted
+		Halted,
+		// Invalid fee config
+		InvalidFeeConfig,
+		/// Invalid Channel
+		InvalidChannel,
+	}
+
+	/// Messages to be committed in the current block. This storage value is killed in
+	/// `on_initialize`, so should never go into block PoV.
+	///
+	/// Is never read in the runtime, only by offchain message relayers.
+	///
+	/// Inspired by the `frame_system::Pallet::Events` storage value
+	#[pallet::storage]
+	#[pallet::unbounded]
+	pub(super) type Messages<T: Config> = StorageValue<_, Vec<CommittedMessage>, ValueQuery>;
+
+	/// Hashes of the ABI-encoded messages in the [`Messages`] storage value. Used to generate a
+	/// merkle root during `on_finalize`. This storage value is killed in
+	/// `on_initialize`, so should never go into block PoV.
+	#[pallet::storage]
+	#[pallet::unbounded]
+	#[pallet::getter(fn message_leaves)]
+	pub(super) type MessageLeaves<T: Config> = StorageValue<_, Vec<H256>, ValueQuery>;
+
+	/// The current nonce for each message origin
+	#[pallet::storage]
+	pub type Nonce<T: Config> = StorageMap<_, Twox64Concat, ChannelId, u64, ValueQuery>;
+
+	/// The current operating mode of the pallet.
+	#[pallet::storage]
+	#[pallet::getter(fn operating_mode)]
+	pub type OperatingMode<T: Config> = StorageValue<_, BasicOperatingMode, ValueQuery>;
+
+	#[pallet::hooks]
+	impl<T: Config> Hooks<BlockNumberFor<T>> for Pallet<T>
+	where
+		T::AccountId: AsRef<[u8]>,
+	{
+		fn on_initialize(_: BlockNumberFor<T>) -> Weight {
+			// Remove storage from previous block
+			Messages::<T>::kill();
+			MessageLeaves::<T>::kill();
+			// Reserve some weight for the `on_finalize` handler
+			T::WeightInfo::commit()
+		}
+
+		fn on_finalize(_: BlockNumberFor<T>) {
+			Self::commit();
+		}
+
+		fn integrity_test() {
+			let decimals = T::Decimals::get();
+			assert!(decimals == 10 || decimals == 12, "Decimals should be 10 or 12");
+		}
+	}
+
+	#[pallet::call]
+	impl<T: Config> Pallet<T> {
+		/// Halt or resume all pallet operations. May only be called by root.
+		#[pallet::call_index(0)]
+		#[pallet::weight((T::DbWeight::get().reads_writes(1, 1), DispatchClass::Operational))]
+		pub fn set_operating_mode(
+			origin: OriginFor<T>,
+			mode: BasicOperatingMode,
+		) -> DispatchResult {
+			ensure_root(origin)?;
+			OperatingMode::<T>::put(mode);
+			Self::deposit_event(Event::OperatingModeChanged { mode });
+			Ok(())
+		}
+	}
+
+	impl<T: Config> Pallet<T> {
+		/// Generate a messages commitment and insert it into the header digest
+		pub(crate) fn commit() {
+			let count = MessageLeaves::<T>::decode_len().unwrap_or_default() as u64;
+			if count == 0 {
+				return
+			}
+
+			// Create merkle root of messages
+			let root = merkle_root::<<T as Config>::Hashing, _>(MessageLeaves::<T>::stream_iter());
+
+			let digest_item: DigestItem = CustomDigestItem::Snowbridge(root).into();
+
+			// Insert merkle root into the header digest
+			<frame_system::Pallet<T>>::deposit_log(digest_item);
+
+			Self::deposit_event(Event::MessagesCommitted { root, count });
+		}
+
+		/// Process a message delivered by the MessageQueue pallet
+		pub(crate) fn do_process_message(
+			_: ProcessMessageOriginOf<T>,
+			mut message: &[u8],
+		) -> Result<bool, ProcessMessageError> {
+			use ProcessMessageError::*;
+
+			// Yield if the maximum number of messages has been processed this block.
+			// This ensures that the weight of `on_finalize` has a known maximum bound.
+			ensure!(
+				MessageLeaves::<T>::decode_len().unwrap_or(0) <
+					T::MaxMessagesPerBlock::get() as usize,
+				Yield
+			);
+
+			// Decode bytes into versioned message
+			let versioned_queued_message: VersionedQueuedMessage =
+				VersionedQueuedMessage::decode(&mut message).map_err(|_| Corrupt)?;
+
+			// Convert versioned message into latest supported message version
+			let queued_message: QueuedMessage =
+				versioned_queued_message.try_into().map_err(|_| Unsupported)?;
+
+			// Obtain next nonce
+			let nonce = <Nonce<T>>::try_mutate(
+				queued_message.channel_id,
+				|nonce| -> Result<u64, ProcessMessageError> {
+					*nonce = nonce.checked_add(1).ok_or(Unsupported)?;
+					Ok(*nonce)
+				},
+			)?;
+
+			let pricing_params = T::PricingParameters::get();
+			let command = queued_message.command.index();
+			let params = queued_message.command.abi_encode();
+			let max_dispatch_gas =
+				T::GasMeter::maximum_dispatch_gas_used_at_most(&queued_message.command);
+			let reward = pricing_params.rewards.remote;
+
+			// Construct the final committed message
+			let message = CommittedMessage {
+				channel_id: queued_message.channel_id,
+				nonce,
+				command,
+				params,
+				max_dispatch_gas,
+				max_fee_per_gas: pricing_params
+					.fee_per_gas
+					.try_into()
+					.defensive_unwrap_or(u128::MAX),
+				reward: reward.try_into().defensive_unwrap_or(u128::MAX),
+				id: queued_message.id,
+			};
+
+			// ABI-encode and hash the prepared message
+			let message_abi_encoded = ethabi::encode(&[message.clone().into()]);
+			let message_abi_encoded_hash = <T as Config>::Hashing::hash(&message_abi_encoded);
+
+			Messages::<T>::append(Box::new(message));
+			MessageLeaves::<T>::append(message_abi_encoded_hash);
+
+			Self::deposit_event(Event::MessageAccepted { id: queued_message.id, nonce });
+
+			Ok(true)
+		}
+
+		/// Calculate total fee in native currency to cover all costs of delivering a message to the
+		/// remote destination. See module-level documentation for more details.
+		pub(crate) fn calculate_fee(
+			gas_used_at_most: u64,
+			params: PricingParameters<T::Balance>,
+		) -> Fee<T::Balance> {
+			// Remote fee in ether
+			let fee = Self::calculate_remote_fee(
+				gas_used_at_most,
+				params.fee_per_gas,
+				params.rewards.remote,
+			);
+
+			// downcast to u128
+			let fee: u128 = fee.try_into().defensive_unwrap_or(u128::MAX);
+
+			// convert to local currency
+			let fee = FixedU128::from_inner(fee)
+				.checked_div(&params.exchange_rate)
+				.expect("exchange rate is not zero; qed")
+				.into_inner();
+
+			// adjust fixed point to match local currency
+			let fee = Self::convert_from_ether_decimals(fee);
+
+			Fee::from((Self::calculate_local_fee(), fee))
+		}
+
+		/// Calculate fee in remote currency for dispatching a message on Ethereum
+		pub(crate) fn calculate_remote_fee(
+			gas_used_at_most: u64,
+			fee_per_gas: U256,
+			reward: U256,
+		) -> U256 {
+			fee_per_gas.saturating_mul(gas_used_at_most.into()).saturating_add(reward)
+		}
+
+		/// The local component of the message processing fees in native currency
+		pub(crate) fn calculate_local_fee() -> T::Balance {
+			T::WeightToFee::weight_to_fee(
+				&T::WeightInfo::do_process_message().saturating_add(T::WeightInfo::commit_single()),
+			)
+		}
+
+		// 1 DOT has 10 digits of precision
+		// 1 KSM has 12 digits of precision
+		// 1 ETH has 18 digits of precision
+		pub(crate) fn convert_from_ether_decimals(value: u128) -> T::Balance {
+			let decimals = ETHER_DECIMALS.saturating_sub(T::Decimals::get()) as u32;
+			let denom = 10u128.saturating_pow(decimals);
+			value.checked_div(denom).expect("divisor is non-zero; qed").into()
+		}
+	}
+}

bridges/snowbridge/parachain/pallets/outbound-queue/src/mock.rs

@@ -0,0 +1,189 @@
+// SPDX-License-Identifier: Apache-2.0
+// SPDX-FileCopyrightText: 2023 Snowfork <hello@snowfork.com>
+use super::*;
+
+use frame_support::{
+	parameter_types,
+	traits::{Everything, Hooks},
+	weights::IdentityFee,
+};
+
+use snowbridge_core::{
+	gwei, meth,
+	outbound::*,
+	pricing::{PricingParameters, Rewards},
+	ParaId, PRIMARY_GOVERNANCE_CHANNEL,
+};
+use sp_core::{ConstU32, ConstU8, H160, H256};
+use sp_runtime::{
+	traits::{BlakeTwo256, IdentityLookup, Keccak256},
+	AccountId32, BuildStorage, FixedU128,
+};
+use sp_std::marker::PhantomData;
+
+type Block = frame_system::mocking::MockBlock<Test>;
+type AccountId = AccountId32;
+
+frame_support::construct_runtime!(
+	pub enum Test
+	{
+		System: frame_system::{Pallet, Call, Storage, Event<T>},
+		MessageQueue: pallet_message_queue::{Pallet, Call, Storage, Event<T>},
+		OutboundQueue: crate::{Pallet, Storage, Event<T>},
+	}
+);
+
+parameter_types! {
+	pub const BlockHashCount: u64 = 250;
+}
+
+impl frame_system::Config for Test {
+	type BaseCallFilter = Everything;
+	type BlockWeights = ();
+	type BlockLength = ();
+	type RuntimeOrigin = RuntimeOrigin;
+	type RuntimeCall = RuntimeCall;
+	type RuntimeTask = RuntimeTask;
+	type Hash = H256;
+	type Hashing = BlakeTwo256;
+	type AccountId = AccountId;
+	type Lookup = IdentityLookup<Self::AccountId>;
+	type RuntimeEvent = RuntimeEvent;
+	type BlockHashCount = BlockHashCount;
+	type DbWeight = ();
+	type Version = ();
+	type PalletInfo = PalletInfo;
+	type AccountData = ();
+	type OnNewAccount = ();
+	type OnKilledAccount = ();
+	type SystemWeightInfo = ();
+	type SS58Prefix = ();
+	type OnSetCode = ();
+	type MaxConsumers = frame_support::traits::ConstU32<16>;
+	type Nonce = u64;
+	type Block = Block;
+}
+
+parameter_types! {
+	pub const HeapSize: u32 = 32 * 1024;
+	pub const MaxStale: u32 = 32;
+	pub static ServiceWeight: Option<Weight> = Some(Weight::from_parts(100, 100));
+}
+
+impl pallet_message_queue::Config for Test {
+	type RuntimeEvent = RuntimeEvent;
+	type WeightInfo = ();
+	type MessageProcessor = OutboundQueue;
+	type Size = u32;
+	type QueueChangeHandler = ();
+	type HeapSize = HeapSize;
+	type MaxStale = MaxStale;
+	type ServiceWeight = ServiceWeight;
+	type QueuePausedQuery = ();
+}
+
+parameter_types! {
+	pub const OwnParaId: ParaId = ParaId::new(1013);
+	pub Parameters: PricingParameters<u128> = PricingParameters {
+		exchange_rate: FixedU128::from_rational(1, 400),
+		fee_per_gas: gwei(20),
+		rewards: Rewards { local: DOT, remote: meth(1) }
+	};
+}
+
+pub const DOT: u128 = 10_000_000_000;
+
+impl crate::Config for Test {
+	type RuntimeEvent = RuntimeEvent;
+	type Hashing = Keccak256;
+	type MessageQueue = MessageQueue;
+	type Decimals = ConstU8<12>;
+	type MaxMessagePayloadSize = ConstU32<1024>;
+	type MaxMessagesPerBlock = ConstU32<20>;
+	type GasMeter = ConstantGasMeter;
+	type Balance = u128;
+	type PricingParameters = Parameters;
+	type Channels = Everything;
+	type WeightToFee = IdentityFee<u128>;
+	type WeightInfo = ();
+}
+
+fn setup() {
+	System::set_block_number(1);
+}
+
+pub fn new_tester() -> sp_io::TestExternalities {
+	let storage = frame_system::GenesisConfig::<Test>::default().build_storage().unwrap();
+	let mut ext: sp_io::TestExternalities = storage.into();
+	ext.execute_with(setup);
+	ext
+}
+
+pub fn run_to_end_of_next_block() {
+	// finish current block
+	MessageQueue::on_finalize(System::block_number());
+	OutboundQueue::on_finalize(System::block_number());
+	System::on_finalize(System::block_number());
+	// start next block
+	System::set_block_number(System::block_number() + 1);
+	System::on_initialize(System::block_number());
+	OutboundQueue::on_initialize(System::block_number());
+	MessageQueue::on_initialize(System::block_number());
+	// finish next block
+	MessageQueue::on_finalize(System::block_number());
+	OutboundQueue::on_finalize(System::block_number());
+	System::on_finalize(System::block_number());
+}
+
+pub fn mock_governance_message<T>() -> Message
+where
+	T: Config,
+{
+	let _marker = PhantomData::<T>; // for clippy
+
+	Message {
+		id: None,
+		channel_id: PRIMARY_GOVERNANCE_CHANNEL,
+		command: Command::Upgrade {
+			impl_address: H160::zero(),
+			impl_code_hash: H256::zero(),
+			initializer: None,
+		},
+	}
+}
+
+// Message should fail validation as it is too large
+pub fn mock_invalid_governance_message<T>() -> Message
+where
+	T: Config,
+{
+	let _marker = PhantomData::<T>; // for clippy
+
+	Message {
+		id: None,
+		channel_id: PRIMARY_GOVERNANCE_CHANNEL,
+		command: Command::Upgrade {
+			impl_address: H160::zero(),
+			impl_code_hash: H256::zero(),
+			initializer: Some(Initializer {
+				params: (0..1000).map(|_| 1u8).collect::<Vec<u8>>(),
+				maximum_required_gas: 0,
+			}),
+		},
+	}
+}
+
+pub fn mock_message(sibling_para_id: u32) -> Message {
+	Message {
+		id: None,
+		channel_id: ParaId::from(sibling_para_id).into(),
+		command: Command::AgentExecute {
+			agent_id: Default::default(),
+			command: AgentExecuteCommand::TransferToken {
+				token: Default::default(),
+				recipient: Default::default(),
+				amount: 0,
+			},
+		},
+	}
+}

bridges/snowbridge/parachain/pallets/outbound-queue/src/process_message_impl.rs

@@ -0,0 +1,23 @@
+//! Implementation for [`frame_support::traits::ProcessMessage`]
+use super::*;
+use crate::weights::WeightInfo;
+use frame_support::{
+	traits::{ProcessMessage, ProcessMessageError},
+	weights::WeightMeter,
+};
+
+impl<T: Config> ProcessMessage for Pallet<T> {
+	type Origin = AggregateMessageOrigin;
+	fn process_message(
+		message: &[u8],
+		origin: Self::Origin,
+		meter: &mut WeightMeter,
+		_: &mut [u8; 32],
+	) -> Result<bool, ProcessMessageError> {
+		let weight = T::WeightInfo::do_process_message();
+		if meter.try_consume(weight).is_err() {
+			return Err(ProcessMessageError::Overweight(weight))
+		}
+		Self::do_process_message(origin, message)
+	}
+}

bridges/snowbridge/parachain/pallets/outbound-queue/src/send_message_impl.rs

@@ -0,0 +1,98 @@
+//! Implementation for [`snowbridge_core::outbound::SendMessage`]
+use super::*;
+use bridge_hub_common::AggregateMessageOrigin;
+use codec::Encode;
+use frame_support::{
+	ensure,
+	traits::{EnqueueMessage, Get},
+	CloneNoBound, PartialEqNoBound, RuntimeDebugNoBound,
+};
+use frame_system::unique;
+use snowbridge_core::{
+	outbound::{
+		Fee, Message, QueuedMessage, SendError, SendMessage, SendMessageFeeProvider,
+		VersionedQueuedMessage,
+	},
+	ChannelId, PRIMARY_GOVERNANCE_CHANNEL,
+};
+use sp_core::H256;
+use sp_runtime::BoundedVec;
+
+/// The maximal length of an enqueued message, as determined by the MessageQueue pallet
+pub type MaxEnqueuedMessageSizeOf<T> =
+	<<T as Config>::MessageQueue as EnqueueMessage<AggregateMessageOrigin>>::MaxMessageLen;
+
+#[derive(Encode, Decode, CloneNoBound, PartialEqNoBound, RuntimeDebugNoBound)]
+pub struct Ticket<T>
+where
+	T: Config,
+{
+	pub message_id: H256,
+	pub channel_id: ChannelId,
+	pub message: BoundedVec<u8, MaxEnqueuedMessageSizeOf<T>>,
+}
+
+impl<T> SendMessage for Pallet<T>
+where
+	T: Config,
+{
+	type Ticket = Ticket<T>;
+
+	fn validate(
+		message: &Message,
+	) -> Result<(Self::Ticket, Fee<<Self as SendMessageFeeProvider>::Balance>), SendError> {
+		// The inner payload should not be too large
+		let payload = message.command.abi_encode();
+		ensure!(
+			payload.len() < T::MaxMessagePayloadSize::get() as usize,
+			SendError::MessageTooLarge
+		);
+
+		// Ensure there is a registered channel we can transmit this message on
+		ensure!(T::Channels::contains(&message.channel_id), SendError::InvalidChannel);
+
+		// Generate a unique message id unless one is provided
+		let message_id: H256 = message
+			.id
+			.unwrap_or_else(|| unique((message.channel_id, &message.command)).into());
+
+		let gas_used_at_most = T::GasMeter::maximum_gas_used_at_most(&message.command);
+		let fee = Self::calculate_fee(gas_used_at_most, T::PricingParameters::get());
+
+		let queued_message: VersionedQueuedMessage = QueuedMessage {
+			id: message_id,
+			channel_id: message.channel_id,
+			command: message.command.clone(),
+		}
+		.into();
+		// The whole message should not be too large
+		let encoded = queued_message.encode().try_into().map_err(|_| SendError::MessageTooLarge)?;
+
+		let ticket = Ticket { message_id, channel_id: message.channel_id, message: encoded };
+
+		Ok((ticket, fee))
+	}
+
+	fn deliver(ticket: Self::Ticket) -> Result<H256, SendError> {
+		let origin = AggregateMessageOrigin::Snowbridge(ticket.channel_id);
+
+		if ticket.channel_id != PRIMARY_GOVERNANCE_CHANNEL {
+			ensure!(!Self::operating_mode().is_halted(), SendError::Halted);
+		}
+
+		let message = ticket.message.as_bounded_slice();
+
+		T::MessageQueue::enqueue_message(message, origin);
+		Self::deposit_event(Event::MessageQueued { id: ticket.message_id });
+		Ok(ticket.message_id)
+	}
+}
+
+impl<T: Config> SendMessageFeeProvider for Pallet<T> {
+	type Balance = T::Balance;
+
+	/// The local component of the message processing fees in native currency
+	fn local_fee() -> Self::Balance {
+		Self::calculate_local_fee()
+	}
+}

bridges/snowbridge/parachain/pallets/outbound-queue/src/test.rs

@@ -0,0 +1,268 @@
+// SPDX-License-Identifier: Apache-2.0
+// SPDX-FileCopyrightText: 2023 Snowfork <hello@snowfork.com>
+use crate::{mock::*, *};
+
+use frame_support::{
+	assert_err, assert_noop, assert_ok,
+	traits::{Hooks, ProcessMessage, ProcessMessageError},
+	weights::WeightMeter,
+};
+
+use codec::Encode;
+use snowbridge_core::{
+	outbound::{Command, SendError, SendMessage},
+	ParaId,
+};
+use sp_arithmetic::FixedU128;
+use sp_core::H256;
+use sp_runtime::FixedPointNumber;
+
+#[test]
+fn submit_messages_and_commit() {
+	new_tester().execute_with(|| {
+		for para_id in 1000..1004 {
+			let message = mock_message(para_id);
+			let (ticket, _) = OutboundQueue::validate(&message).unwrap();
+			assert_ok!(OutboundQueue::deliver(ticket));
+		}
+
+		ServiceWeight::set(Some(Weight::MAX));
+		run_to_end_of_next_block();
+
+		for para_id in 1000..1004 {
+			let origin: ParaId = (para_id as u32).into();
+			let channel_id: ChannelId = origin.into();
+			assert_eq!(Nonce::<Test>::get(channel_id), 1);
+		}
+
+		let digest = System::digest();
+		let digest_items = digest.logs();
+		assert!(digest_items.len() == 1 && digest_items[0].as_other().is_some());
+		assert_eq!(Messages::<Test>::decode_len(), Some(4));
+	});
+}
+
+#[test]
+fn submit_message_fail_too_large() {
+	new_tester().execute_with(|| {
+		let message = mock_invalid_governance_message::<Test>();
+		assert_err!(OutboundQueue::validate(&message), SendError::MessageTooLarge);
+	});
+}
+
+#[test]
+fn convert_from_ether_decimals() {
+	assert_eq!(
+		OutboundQueue::convert_from_ether_decimals(1_000_000_000_000_000_000),
+		1_000_000_000_000
+	);
+}
+
+#[test]
+fn commit_exits_early_if_no_processed_messages() {
+	new_tester().execute_with(|| {
+		// on_finalize should do nothing, nor should it panic
+		OutboundQueue::on_finalize(System::block_number());
+
+		let digest = System::digest();
+		let digest_items = digest.logs();
+		assert_eq!(digest_items.len(), 0);
+	});
+}
+
+#[test]
+fn process_message_yields_on_max_messages_per_block() {
+	new_tester().execute_with(|| {
+		for _ in 0..<Test as Config>::MaxMessagesPerBlock::get() {
+			MessageLeaves::<Test>::append(H256::zero())
+		}
+
+		let channel_id: ChannelId = ParaId::from(1000).into();
+		let origin = AggregateMessageOrigin::Snowbridge(channel_id);
+		let message = QueuedMessage {
+			id: Default::default(),
+			channel_id,
+			command: Command::Upgrade {
+				impl_address: Default::default(),
+				impl_code_hash: Default::default(),
+				initializer: None,
+			},
+		}
+		.encode();
+
+		let mut meter = WeightMeter::new();
+
+		assert_noop!(
+			OutboundQueue::process_message(message.as_slice(), origin, &mut meter, &mut [0u8; 32]),
+			ProcessMessageError::Yield
+		);
+	})
+}
+
+#[test]
+fn process_message_fails_on_max_nonce_reached() {
+	new_tester().execute_with(|| {
+		let sibling_id = 1000;
+		let channel_id: ChannelId = ParaId::from(sibling_id).into();
+		let origin = AggregateMessageOrigin::Snowbridge(channel_id);
+		let message: QueuedMessage = QueuedMessage {
+			id: H256::zero(),
+			channel_id,
+			command: mock_message(sibling_id).command,
+		};
+		let versioned_queued_message: VersionedQueuedMessage = message.try_into().unwrap();
+		let encoded = versioned_queued_message.encode();
+		let mut meter = WeightMeter::with_limit(Weight::MAX);
+
+		Nonce::<Test>::set(channel_id, u64::MAX);
+
+		assert_noop!(
+			OutboundQueue::process_message(encoded.as_slice(), origin, &mut meter, &mut [0u8; 32]),
+			ProcessMessageError::Unsupported
+		);
+	})
+}
+
+#[test]
+fn process_message_fails_on_overweight_message() {
+	new_tester().execute_with(|| {
+		let sibling_id = 1000;
+		let channel_id: ChannelId = ParaId::from(sibling_id).into();
+		let origin = AggregateMessageOrigin::Snowbridge(channel_id);
+		let message: QueuedMessage = QueuedMessage {
+			id: H256::zero(),
+			channel_id,
+			command: mock_message(sibling_id).command,
+		};
+		let versioned_queued_message: VersionedQueuedMessage = message.try_into().unwrap();
+		let encoded = versioned_queued_message.encode();
+		let mut meter = WeightMeter::with_limit(Weight::from_parts(1, 1));
+		assert_noop!(
+			OutboundQueue::process_message(encoded.as_slice(), origin, &mut meter, &mut [0u8; 32]),
+			ProcessMessageError::Overweight(<Test as Config>::WeightInfo::do_process_message())
+		);
+	})
+}
+
+// Governance messages should be able to bypass a halted operating mode
+// Other message sends should fail when halted
+#[test]
+fn submit_upgrade_message_success_when_queue_halted() {
+	new_tester().execute_with(|| {
+		// halt the outbound queue
+		OutboundQueue::set_operating_mode(RuntimeOrigin::root(), BasicOperatingMode::Halted)
+			.unwrap();
+
+		// submit a high priority message from bridge_hub should success
+		let message = mock_governance_message::<Test>();
+		let (ticket, _) = OutboundQueue::validate(&message).unwrap();
+		assert_ok!(OutboundQueue::deliver(ticket));
+
+		// submit a low priority message from asset_hub will fail as pallet is halted
+		let message = mock_message(1000);
+		let (ticket, _) = OutboundQueue::validate(&message).unwrap();
+		assert_noop!(OutboundQueue::deliver(ticket), SendError::Halted);
+	});
+}
+
+#[test]
+fn governance_message_does_not_get_the_chance_to_processed_in_same_block_when_congest_of_low_priority_sibling_messages(
+) {
+	use snowbridge_core::PRIMARY_GOVERNANCE_CHANNEL;
+	use AggregateMessageOrigin::*;
+
+	let sibling_id: u32 = 1000;
+	let sibling_channel_id: ChannelId = ParaId::from(sibling_id).into();
+
+	new_tester().execute_with(|| {
+		// submit a lot of low priority messages from asset_hub which will need multiple blocks to
+		// execute(20 messages for each block so 40 required at least 2 blocks)
+		let max_messages = 40;
+		for _ in 0..max_messages {
+			// submit low priority message
+			let message = mock_message(sibling_id);
+			let (ticket, _) = OutboundQueue::validate(&message).unwrap();
+			OutboundQueue::deliver(ticket).unwrap();
+		}
+
+		let footprint = MessageQueue::footprint(Snowbridge(sibling_channel_id));
+		assert_eq!(footprint.storage.count, (max_messages) as u64);
+
+		let message = mock_governance_message::<Test>();
+		let (ticket, _) = OutboundQueue::validate(&message).unwrap();
+		OutboundQueue::deliver(ticket).unwrap();
+
+		// move to next block
+		ServiceWeight::set(Some(Weight::MAX));
+		run_to_end_of_next_block();
+
+		// first process 20 messages from sibling channel
+		let footprint = MessageQueue::footprint(Snowbridge(sibling_channel_id));
+		assert_eq!(footprint.storage.count, 40 - 20);
+
+		// and governance message does not have the chance to execute in same block
+		let footprint = MessageQueue::footprint(Snowbridge(PRIMARY_GOVERNANCE_CHANNEL));
+		assert_eq!(footprint.storage.count, 1);
+
+		// move to next block
+		ServiceWeight::set(Some(Weight::MAX));
+		run_to_end_of_next_block();
+
+		// now governance message get executed in this block
+		let footprint = MessageQueue::footprint(Snowbridge(PRIMARY_GOVERNANCE_CHANNEL));
+		assert_eq!(footprint.storage.count, 0);
+
+		// and this time process 19 messages from sibling channel so we have 1 message left
+		let footprint = MessageQueue::footprint(Snowbridge(sibling_channel_id));
+		assert_eq!(footprint.storage.count, 1);
+
+		// move to the next block, the last 1 message from sibling channel get executed
+		ServiceWeight::set(Some(Weight::MAX));
+		run_to_end_of_next_block();
+		let footprint = MessageQueue::footprint(Snowbridge(sibling_channel_id));
+		assert_eq!(footprint.storage.count, 0);
+	});
+}
+
+#[test]
+fn convert_local_currency() {
+	new_tester().execute_with(|| {
+		let fee: u128 = 1_000_000;
+		let fee1 = FixedU128::from_inner(fee).into_inner();
+		let fee2 = FixedU128::from(fee)
+			.into_inner()
+			.checked_div(FixedU128::accuracy())
+			.expect("accuracy is not zero; qed");
+		assert_eq!(fee, fee1);
+		assert_eq!(fee, fee2);
+	});
+}
+
+#[test]
+fn encode_digest_item_with_correct_index() {
+	new_tester().execute_with(|| {
+		let digest_item: DigestItem = CustomDigestItem::Snowbridge(H256::default()).into();
+		let enum_prefix = match digest_item {
+			DigestItem::Other(data) => data[0],
+			_ => u8::MAX,
+		};
+		assert_eq!(enum_prefix, 0);
+	});
+}
+
+#[test]
+fn encode_digest_item() {
+	new_tester().execute_with(|| {
+		let digest_item: DigestItem = CustomDigestItem::Snowbridge([5u8; 32].into()).into();
+		let digest_item_raw = digest_item.encode();
+		assert_eq!(digest_item_raw[0], 0); // DigestItem::Other
+		assert_eq!(digest_item_raw[2], 0); // CustomDigestItem::Snowbridge
+		assert_eq!(
+			digest_item_raw,
+			[
+				0, 132, 0, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
+				5, 5, 5, 5, 5, 5, 5, 5
+			]
+		);
+	});
+}

bridges/snowbridge/parachain/pallets/outbound-queue/src/types.rs

@@ -0,0 +1,99 @@
+use codec::{Decode, Encode, MaxEncodedLen};
+use ethabi::Token;
+use frame_support::traits::ProcessMessage;
+use scale_info::TypeInfo;
+use serde::{Deserialize, Serialize};
+use sp_arithmetic::FixedU128;
+use sp_core::H256;
+use sp_runtime::{traits::Zero, RuntimeDebug};
+use sp_std::prelude::*;
+
+use super::Pallet;
+
+use snowbridge_core::ChannelId;
+pub use snowbridge_outbound_queue_merkle_tree::MerkleProof;
+
+pub type ProcessMessageOriginOf<T> = <Pallet<T> as ProcessMessage>::Origin;
+
+pub const LOG_TARGET: &str = "snowbridge-outbound-queue";
+
+/// Message which has been assigned a nonce and will be committed at the end of a block
+#[derive(Encode, Decode, Clone, PartialEq, RuntimeDebug, TypeInfo)]
+pub struct CommittedMessage {
+	/// Message channel
+	pub channel_id: ChannelId,
+	/// Unique nonce to prevent replaying messages
+	#[codec(compact)]
+	pub nonce: u64,
+	/// Command to execute in the Gateway contract
+	pub command: u8,
+	/// Params for the command
+	pub params: Vec<u8>,
+	/// Maximum gas allowed for message dispatch
+	#[codec(compact)]
+	pub max_dispatch_gas: u64,
+	/// Maximum fee per gas
+	#[codec(compact)]
+	pub max_fee_per_gas: u128,
+	/// Reward in ether for delivering this message, in addition to the gas refund
+	#[codec(compact)]
+	pub reward: u128,
+	/// Message ID (Used for tracing messages across route, has no role in consensus)
+	pub id: H256,
+}
+
+/// Convert message into an ABI-encoded form for delivery to the InboundQueue contract on Ethereum
+impl From<CommittedMessage> for Token {
+	fn from(x: CommittedMessage) -> Token {
+		Token::Tuple(vec![
+			Token::FixedBytes(Vec::from(x.channel_id.as_ref())),
+			Token::Uint(x.nonce.into()),
+			Token::Uint(x.command.into()),
+			Token::Bytes(x.params.to_vec()),
+			Token::Uint(x.max_dispatch_gas.into()),
+			Token::Uint(x.max_fee_per_gas.into()),
+			Token::Uint(x.reward.into()),
+			Token::FixedBytes(Vec::from(x.id.as_ref())),
+		])
+	}
+}
+
+/// Configuration for fee calculations
+#[derive(
+	Encode,
+	Decode,
+	Copy,
+	Clone,
+	PartialEq,
+	RuntimeDebug,
+	MaxEncodedLen,
+	TypeInfo,
+	Serialize,
+	Deserialize,
+)]
+pub struct FeeConfigRecord {
+	/// ETH/DOT exchange rate
+	pub exchange_rate: FixedU128,
+	/// Ether fee per unit of gas
+	pub fee_per_gas: u128,
+	/// Ether reward for delivering message
+	pub reward: u128,
+}
+
+#[derive(RuntimeDebug)]
+pub struct InvalidFeeConfig;
+
+impl FeeConfigRecord {
+	pub fn validate(&self) -> Result<(), InvalidFeeConfig> {
+		if self.exchange_rate == FixedU128::zero() {
+			return Err(InvalidFeeConfig)
+		}
+		if self.fee_per_gas == 0 {
+			return Err(InvalidFeeConfig)
+		}
+		if self.reward == 0 {
+			return Err(InvalidFeeConfig)
+		}
+		Ok(())
+	}
+}

bridges/snowbridge/parachain/pallets/outbound-queue/src/weights.rs

@@ -0,0 +1,81 @@
+
+//! Autogenerated weights for `snowbridge_outbound_queue`
+//!
+//! THIS FILE WAS AUTO-GENERATED USING THE SUBSTRATE BENCHMARK CLI VERSION 4.0.0-dev
+//! DATE: 2023-10-19, STEPS: `2`, REPEAT: `1`, LOW RANGE: `[]`, HIGH RANGE: `[]`
+//! WORST CASE MAP SIZE: `1000000`
+//! HOSTNAME: `192.168.1.7`, CPU: `<UNKNOWN>`
+//! WASM-EXECUTION: `Compiled`, CHAIN: `Some("bridge-hub-rococo-dev")`, DB CACHE: `1024`
+
+// Executed Command:
+// target/release/polkadot-parachain
+// benchmark
+// pallet
+// --chain=bridge-hub-rococo-dev
+// --pallet=snowbridge_outbound_queue
+// --extrinsic=*
+// --execution=wasm
+// --wasm-execution=compiled
+// --template
+// ../parachain/templates/module-weight-template.hbs
+// --output
+// ../parachain/pallets/outbound-queue/src/weights.rs
+
+#![cfg_attr(rustfmt, rustfmt_skip)]
+#![allow(unused_parens)]
+#![allow(unused_imports)]
+#![allow(missing_docs)]
+
+use frame_support::{traits::Get, weights::{Weight, constants::RocksDbWeight}};
+use core::marker::PhantomData;
+
+/// Weight functions needed for `snowbridge_outbound_queue`.
+pub trait WeightInfo {
+	fn do_process_message() -> Weight;
+	fn commit() -> Weight;
+	fn commit_single() -> Weight;
+}
+
+// For backwards compatibility and tests.
+impl WeightInfo for () {
+	/// Storage: EthereumOutboundQueue MessageLeaves (r:1 w:1)
+	/// Proof Skipped: EthereumOutboundQueue MessageLeaves (max_values: Some(1), max_size: None, mode: Measured)
+	/// Storage: EthereumOutboundQueue PendingHighPriorityMessageCount (r:1 w:1)
+	/// Proof: EthereumOutboundQueue PendingHighPriorityMessageCount (max_values: Some(1), max_size: Some(4), added: 499, mode: MaxEncodedLen)
+	/// Storage: EthereumOutboundQueue Nonce (r:1 w:1)
+	/// Proof: EthereumOutboundQueue Nonce (max_values: None, max_size: Some(20), added: 2495, mode: MaxEncodedLen)
+	/// Storage: EthereumOutboundQueue Messages (r:1 w:1)
+	/// Proof Skipped: EthereumOutboundQueue Messages (max_values: Some(1), max_size: None, mode: Measured)
+	fn do_process_message() -> Weight {
+		// Proof Size summary in bytes:
+		//  Measured:  `42`
+		//  Estimated: `3485`
+		// Minimum execution time: 39_000_000 picoseconds.
+		Weight::from_parts(39_000_000, 3485)
+			.saturating_add(RocksDbWeight::get().reads(4_u64))
+			.saturating_add(RocksDbWeight::get().writes(4_u64))
+	}
+	/// Storage: EthereumOutboundQueue MessageLeaves (r:1 w:0)
+	/// Proof Skipped: EthereumOutboundQueue MessageLeaves (max_values: Some(1), max_size: None, mode: Measured)
+	/// Storage: System Digest (r:1 w:1)
+	/// Proof Skipped: System Digest (max_values: Some(1), max_size: None, mode: Measured)
+	fn commit() -> Weight {
+		// Proof Size summary in bytes:
+		//  Measured:  `1094`
+		//  Estimated: `2579`
+		// Minimum execution time: 28_000_000 picoseconds.
+		Weight::from_parts(28_000_000, 2579)
+			.saturating_add(RocksDbWeight::get().reads(2_u64))
+			.saturating_add(RocksDbWeight::get().writes(1_u64))
+	}
+
+	fn commit_single() -> Weight {
+		// Proof Size summary in bytes:
+		//  Measured:  `1094`
+		//  Estimated: `2579`
+		// Minimum execution time: 9_000_000 picoseconds.
+		Weight::from_parts(9_000_000, 1586)
+			.saturating_add(RocksDbWeight::get().reads(2_u64))
+			.saturating_add(RocksDbWeight::get().writes(1_u64))
+	}
+}