Transfer Polkadot-native assets to Ethereum (paritytech#5546)

# Description

Adding support for send polkadot native assets(PNA) to Ethereum network
through snowbridge. Asset with location in view of AH Including:

- Relay token `(1,Here)`
- Native asset `(0,[PalletInstance(instance),GenereIndex(index)])`
managed by Assets Pallet
- Native asset of Parachain `(1,[Parachain(paraId)])` managed by Foreign
Assets Pallet

The original PR in #128
which has been internally reviewed by Snowbridge team.

# Notes

- This feature depends on the companion solidity change in
Snowfork/snowbridge#1155. Currently register PNA
is only allowed from
[sudo](https://github.com/Snowfork/polkadot-sdk/blob/46cb3528cd8cd1394af2335a6907d7ab8647717a/bridges/snowbridge/pallets/system/src/lib.rs#L621),
so it's actually not enabled. Will require another runtime upgrade to
make the call permissionless together with upgrading the Gateway
contract.

- To make things easy multi-hop transfer(i.e. sending PNA from Ethereum
through AH to Destination chain) is not support ed in this PR. For this
case user can switch to 2-phases transfer instead.

---------

Co-authored-by: Clara van Staden <[email protected]>
Co-authored-by: Alistair Singh <[email protected]>
Co-authored-by: Vincent Geddes <[email protected]>
Co-authored-by: Francisco Aguirre <[email protected]>
Co-authored-by: Adrian Catangiu <[email protected]>

bridges/snowbridge/pallets/inbound-queue/src/lib.rs

@@ -48,12 +48,11 @@ use frame_support::{
 };
 use frame_system::ensure_signed;
 use scale_info::TypeInfo;
-use sp_core::{H160, H256};
+use sp_core::H160;
 use sp_runtime::traits::Zero;
 use sp_std::vec;
 use xcm::prelude::{
-	send_xcm, Instruction::SetTopic, Junction::*, Location, SendError as XcmpSendError, SendXcm,
-	Xcm, XcmContext, XcmHash,
+	send_xcm, Junction::*, Location, SendError as XcmpSendError, SendXcm, Xcm, XcmContext, XcmHash,
 };
 use xcm_executor::traits::TransactAsset;
 
@@ -62,9 +61,8 @@ use snowbridge_core::{
 	sibling_sovereign_account, BasicOperatingMode, Channel, ChannelId, ParaId, PricingParameters,
 	StaticLookup,
 };
-use snowbridge_router_primitives::{
-	inbound,
-	inbound::{ConvertMessage, ConvertMessageError},
+use snowbridge_router_primitives::inbound::{
+	ConvertMessage, ConvertMessageError, VersionedMessage,
 };
 use sp_runtime::{traits::Saturating, SaturatedConversion, TokenError};
 
@@ -86,6 +84,7 @@ pub mod pallet {
 
 	use frame_support::pallet_prelude::*;
 	use frame_system::pallet_prelude::*;
+	use sp_core::H256;
 
 	#[pallet::pallet]
 	pub struct Pallet<T>(_);
@@ -276,12 +275,12 @@ pub mod pallet {
 				T::Token::transfer(&sovereign_account, &who, amount, Preservation::Preserve)?;
 			}
 
+			// Decode payload into `VersionedMessage`
+			let message = VersionedMessage::decode_all(&mut envelope.payload.as_ref())
+				.map_err(|_| Error::<T>::InvalidPayload)?;
+
 			// Decode message into XCM
-			let (xcm, fee) =
-				match inbound::VersionedMessage::decode_all(&mut envelope.payload.as_ref()) {
-					Ok(message) => Self::do_convert(envelope.message_id, message)?,
-					Err(_) => return Err(Error::<T>::InvalidPayload.into()),
-				};
+			let (xcm, fee) = Self::do_convert(envelope.message_id, message.clone())?;
 
 			log::info!(
 				target: LOG_TARGET,
@@ -323,12 +322,10 @@ pub mod pallet {
 	impl<T: Config> Pallet<T> {
 		pub fn do_convert(
 			message_id: H256,
-			message: inbound::VersionedMessage,
+			message: VersionedMessage,
 		) -> Result<(Xcm<()>, BalanceOf<T>), Error<T>> {
-			let (mut xcm, fee) =
-				T::MessageConverter::convert(message).map_err(|e| Error::<T>::ConvertMessage(e))?;
-			// Append the message id as an XCM topic
-			xcm.inner_mut().extend(vec![SetTopic(message_id.into())]);
+			let (xcm, fee) = T::MessageConverter::convert(message_id, message)
+				.map_err(|e| Error::<T>::ConvertMessage(e))?;
 			Ok((xcm, fee))
 		}
 

bridges/snowbridge/pallets/inbound-queue/src/mock.rs

@@ -10,12 +10,12 @@ use snowbridge_beacon_primitives::{
 use snowbridge_core::{
 	gwei,
 	inbound::{Log, Proof, VerificationError},
-	meth, Channel, ChannelId, PricingParameters, Rewards, StaticLookup,
+	meth, Channel, ChannelId, PricingParameters, Rewards, StaticLookup, TokenId,
 };
 use snowbridge_router_primitives::inbound::MessageToXcm;
 use sp_core::{H160, H256};
 use sp_runtime::{
-	traits::{IdentifyAccount, IdentityLookup, Verify},
+	traits::{IdentifyAccount, IdentityLookup, MaybeEquivalence, Verify},
 	BuildStorage, FixedU128, MultiSignature,
 };
 use sp_std::{convert::From, default::Default};
@@ -112,6 +112,9 @@ parameter_types! {
 	pub const SendTokenExecutionFee: u128 = 1_000_000_000;
 	pub const InitialFund: u128 = 1_000_000_000_000;
 	pub const InboundQueuePalletInstance: u8 = 80;
+	pub UniversalLocation: InteriorLocation =
+		[GlobalConsensus(Westend), Parachain(1002)].into();
+	pub AssetHubFromEthereum: Location = Location::new(1,[GlobalConsensus(Westend),Parachain(1000)]);
 }
 
 #[cfg(feature = "runtime-benchmarks")]
@@ -205,6 +208,16 @@ impl TransactAsset for SuccessfulTransactor {
 	}
 }
 
+pub struct MockTokenIdConvert;
+impl MaybeEquivalence<TokenId, Location> for MockTokenIdConvert {
+	fn convert(_id: &TokenId) -> Option<Location> {
+		Some(Location::parent())
+	}
+	fn convert_back(_loc: &Location) -> Option<TokenId> {
+		None
+	}
+}
+
 impl inbound_queue::Config for Test {
 	type RuntimeEvent = RuntimeEvent;
 	type Verifier = MockVerifier;
@@ -218,6 +231,9 @@ impl inbound_queue::Config for Test {
 		InboundQueuePalletInstance,
 		AccountId,
 		Balance,
+		MockTokenIdConvert,
+		UniversalLocation,
+		AssetHubFromEthereum,
 	>;
 	type PricingParameters = Parameters;
 	type ChannelLookup = MockChannelLookup;

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

@@ -164,13 +164,11 @@ pub fn mock_message(sibling_para_id: u32) -> Message {
 	Message {
 		id: None,
 		channel_id: ParaId::from(sibling_para_id).into(),
-		command: Command::AgentExecute {
+		command: Command::TransferNativeToken {
 			agent_id: Default::default(),
-			command: AgentExecuteCommand::TransferToken {
-				token: Default::default(),
-				recipient: Default::default(),
-				amount: 0,
-			},
+			token: Default::default(),
+			recipient: Default::default(),
+			amount: 0,
 		},
 	}
 }

bridges/snowbridge/pallets/system/src/benchmarking.rs

@@ -159,6 +159,29 @@ mod benchmarks {
 		Ok(())
 	}
 
+	#[benchmark]
+	fn register_token() -> Result<(), BenchmarkError> {
+		let caller: T::AccountId = whitelisted_caller();
+
+		let amount: BalanceOf<T> =
+			(10_000_000_000_000_u128).saturated_into::<u128>().saturated_into();
+
+		T::Token::mint_into(&caller, amount)?;
+
+		let relay_token_asset_id: Location = Location::parent();
+		let asset = Box::new(VersionedLocation::V4(relay_token_asset_id));
+		let asset_metadata = AssetMetadata {
+			name: "wnd".as_bytes().to_vec().try_into().unwrap(),
+			symbol: "wnd".as_bytes().to_vec().try_into().unwrap(),
+			decimals: 12,
+		};
+
+		#[extrinsic_call]
+		_(RawOrigin::Root, asset, asset_metadata);
+
+		Ok(())
+	}
+
 	impl_benchmark_test_suite!(
 		SnowbridgeControl,
 		crate::mock::new_test_ext(true),

bridges/snowbridge/pallets/system/src/lib.rs

@@ -35,8 +35,14 @@
 //!
 //! Typically, Polkadot governance will use the `force_transfer_native_from_agent` and
 //! `force_update_channel` and extrinsics to manage agents and channels for system parachains.
+//!
+//! ## Polkadot-native tokens on Ethereum
+//!
+//! Tokens deposited on AssetHub pallet can be bridged to Ethereum as wrapped ERC20 tokens. As a
+//! prerequisite, the token should be registered first.
+//!
+//! * [`Call::register_token`]: Register a token location as a wrapped ERC20 contract on Ethereum.
 #![cfg_attr(not(feature = "std"), no_std)]
-
 #[cfg(test)]
 mod mock;
 
@@ -63,13 +69,16 @@ use frame_system::pallet_prelude::*;
 use snowbridge_core::{
 	meth,
 	outbound::{Command, Initializer, Message, OperatingMode, SendError, SendMessage},
-	sibling_sovereign_account, AgentId, Channel, ChannelId, ParaId,
-	PricingParameters as PricingParametersRecord, PRIMARY_GOVERNANCE_CHANNEL,
+	sibling_sovereign_account, AgentId, AssetMetadata, Channel, ChannelId, ParaId,
+	PricingParameters as PricingParametersRecord, TokenId, TokenIdOf, PRIMARY_GOVERNANCE_CHANNEL,
 	SECONDARY_GOVERNANCE_CHANNEL,
 };
 use sp_core::{RuntimeDebug, H160, H256};
 use sp_io::hashing::blake2_256;
-use sp_runtime::{traits::BadOrigin, DispatchError, SaturatedConversion};
+use sp_runtime::{
+	traits::{BadOrigin, MaybeEquivalence},
+	DispatchError, SaturatedConversion,
+};
 use sp_std::prelude::*;
 use xcm::prelude::*;
 use xcm_executor::traits::ConvertLocation;
@@ -99,7 +108,7 @@ where
 }
 
 /// Hash the location to produce an agent id
-fn agent_id_of<T: Config>(location: &Location) -> Result<H256, DispatchError> {
+pub fn agent_id_of<T: Config>(location: &Location) -> Result<H256, DispatchError> {
 	T::AgentIdOf::convert_location(location).ok_or(Error::<T>::LocationConversionFailed.into())
 }
 
@@ -127,6 +136,7 @@ where
 
 #[frame_support::pallet]
 pub mod pallet {
+	use frame_support::dispatch::PostDispatchInfo;
 	use snowbridge_core::StaticLookup;
 	use sp_core::U256;
 
@@ -164,6 +174,12 @@ pub mod pallet {
 
 		type WeightInfo: WeightInfo;
 
+		/// This chain's Universal Location.
+		type UniversalLocation: Get<InteriorLocation>;
+
+		// The bridges configured Ethereum location
+		type EthereumLocation: Get<Location>;
+
 		#[cfg(feature = "runtime-benchmarks")]
 		type Helper: BenchmarkHelper<Self::RuntimeOrigin>;
 	}
@@ -211,6 +227,13 @@ pub mod pallet {
 		PricingParametersChanged {
 			params: PricingParametersOf<T>,
 		},
+		/// Register Polkadot-native token as a wrapped ERC20 token on Ethereum
+		RegisterToken {
+			/// Location of Polkadot-native token
+			location: VersionedLocation,
+			/// ID of Polkadot-native token on Ethereum
+			foreign_token_id: H256,
+		},
 	}
 
 	#[pallet::error]
@@ -243,6 +266,16 @@ pub mod pallet {
 	pub type PricingParameters<T: Config> =
 		StorageValue<_, PricingParametersOf<T>, ValueQuery, T::DefaultPricingParameters>;
 
+	/// Lookup table for foreign token ID to native location relative to ethereum
+	#[pallet::storage]
+	pub type ForeignToNativeId<T: Config> =
+		StorageMap<_, Blake2_128Concat, TokenId, xcm::v4::Location, OptionQuery>;
+
+	/// Lookup table for native location relative to ethereum to foreign token ID
+	#[pallet::storage]
+	pub type NativeToForeignId<T: Config> =
+		StorageMap<_, Blake2_128Concat, xcm::v4::Location, TokenId, OptionQuery>;
+
 	#[pallet::genesis_config]
 	#[derive(frame_support::DefaultNoBound)]
 	pub struct GenesisConfig<T: Config> {
@@ -574,6 +607,34 @@ pub mod pallet {
 			});
 			Ok(())
 		}
+
+		/// Registers a Polkadot-native token as a wrapped ERC20 token on Ethereum.
+		/// Privileged. Can only be called by root.
+		///
+		/// Fee required: No
+		///
+		/// - `origin`: Must be root
+		/// - `location`: Location of the asset (relative to this chain)
+		/// - `metadata`: Metadata to include in the instantiated ERC20 contract on Ethereum
+		#[pallet::call_index(10)]
+		#[pallet::weight(T::WeightInfo::register_token())]
+		pub fn register_token(
+			origin: OriginFor<T>,
+			location: Box<VersionedLocation>,
+			metadata: AssetMetadata,
+		) -> DispatchResultWithPostInfo {
+			ensure_root(origin)?;
+
+			let location: Location =
+				(*location).try_into().map_err(|_| Error::<T>::UnsupportedLocationVersion)?;
+
+			Self::do_register_token(&location, metadata, PaysFee::<T>::No)?;
+
+			Ok(PostDispatchInfo {
+				actual_weight: Some(T::WeightInfo::register_token()),
+				pays_fee: Pays::No,
+			})
+		}
 	}
 
 	impl<T: Config> Pallet<T> {
@@ -663,6 +724,42 @@ pub mod pallet {
 			let secondary_exists = Channels::<T>::contains_key(SECONDARY_GOVERNANCE_CHANNEL);
 			primary_exists && secondary_exists
 		}
+
+		pub(crate) fn do_register_token(
+			location: &Location,
+			metadata: AssetMetadata,
+			pays_fee: PaysFee<T>,
+		) -> Result<(), DispatchError> {
+			let ethereum_location = T::EthereumLocation::get();
+			// reanchor to Ethereum context
+			let location = location
+				.clone()
+				.reanchored(&ethereum_location, &T::UniversalLocation::get())
+				.map_err(|_| Error::<T>::LocationConversionFailed)?;
+
+			let token_id = TokenIdOf::convert_location(&location)
+				.ok_or(Error::<T>::LocationConversionFailed)?;
+
+			if !ForeignToNativeId::<T>::contains_key(token_id) {
+				NativeToForeignId::<T>::insert(location.clone(), token_id);
+				ForeignToNativeId::<T>::insert(token_id, location.clone());
+			}
+
+			let command = Command::RegisterForeignToken {
+				token_id,
+				name: metadata.name.into_inner(),
+				symbol: metadata.symbol.into_inner(),
+				decimals: metadata.decimals,
+			};
+			Self::send(SECONDARY_GOVERNANCE_CHANNEL, command, pays_fee)?;
+
+			Self::deposit_event(Event::<T>::RegisterToken {
+				location: location.clone().into(),
+				foreign_token_id: token_id,
+			});
+
+			Ok(())
+		}
 	}
 
 	impl<T: Config> StaticLookup for Pallet<T> {
@@ -684,4 +781,13 @@ pub mod pallet {
 			PricingParameters::<T>::get()
 		}
 	}
+
+	impl<T: Config> MaybeEquivalence<TokenId, Location> for Pallet<T> {
+		fn convert(foreign_id: &TokenId) -> Option<Location> {
+			ForeignToNativeId::<T>::get(foreign_id)
+		}
+		fn convert_back(location: &Location) -> Option<TokenId> {
+			NativeToForeignId::<T>::get(location)
+		}
+	}
 }