xcm_config.rs

// Copyright 2019-2022 Parity Technologies (UK) Ltd.
// This file is part of Cumulus.

// Cumulus 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.

// Cumulus 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 Cumulus.  If not, see <http://www.gnu.org/licenses/>.

//! Holds the XCM specific configuration that would otherwise be in lib.rs
//!
//! This configuration dictates how the Penpal chain will communicate with other chains.
//!
//! One of the main uses of the penpal chain will be to be a benefactor of reserve asset transfers
//! with statemine as the reserve. At present no derivative tokens are minted on receipt of a
//! ReserveAssetTransferDeposited message but that will but the intension will be to support this soon.
use super::{
	AccountId, AssetId as AssetIdPalletAssets, Assets, Balance, Balances, Origin, ParachainInfo,
	ParachainSystem, PolkadotXcm, Runtime, RuntimeCall, RuntimeEvent, WeightToFee, XcmpQueue,
};
use core::marker::PhantomData;
use frame_support::{
	log, match_types, parameter_types,
	traits::{
		fungibles::{self, Balanced, CreditOf},
		Contains, Everything, Get, Nothing,
	},
};
use pallet_asset_tx_payment::HandleCredit;
use pallet_xcm::XcmPassthrough;
use polkadot_parachain::primitives::Sibling;
use polkadot_runtime_common::impls::ToAuthor;
use sp_runtime::traits::Zero;
use xcm::latest::{prelude::*, Weight as XCMWeight};
use xcm_builder::{
	AccountId32Aliases, AllowKnownQueryResponses, AllowSubscriptionsFrom,
	AllowTopLevelPaidExecutionFrom, AllowUnpaidExecutionFrom, AsPrefixedGeneralIndex,
	ConvertedConcreteAssetId, CurrencyAdapter, EnsureXcmOrigin, FixedWeightBounds,
	FungiblesAdapter, IsConcrete, LocationInverter, NativeAsset, ParentIsPreset,
	RelayChainAsNative, SiblingParachainAsNative, SiblingParachainConvertsVia,
	SignedAccountId32AsNative, SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit,
	UsingComponents,
};
use xcm_executor::{
	traits::{FilterAssetLocation, JustTry, ShouldExecute},
	XcmExecutor,
};

parameter_types! {
	pub const RelayLocation: MultiLocation = MultiLocation::parent();
	pub const RelayNetwork: NetworkId = NetworkId::Any;
	pub RelayChainOrigin: Origin = cumulus_pallet_xcm::Origin::Relay.into();
	pub Ancestry: MultiLocation = Parachain(ParachainInfo::parachain_id().into()).into();
}

/// Type for specifying how a `MultiLocation` can be converted into an `AccountId`. This is used
/// when determining ownership of accounts for asset transacting and when attempting to use XCM
/// `Transact` in order to determine the dispatch Origin.
pub type LocationToAccountId = (
	// The parent (Relay-chain) origin converts to the parent `AccountId`.
	ParentIsPreset<AccountId>,
	// Sibling parachain origins convert to AccountId via the `ParaId::into`.
	SiblingParachainConvertsVia<Sibling, AccountId>,
	// Straight up local `AccountId32` origins just alias directly to `AccountId`.
	AccountId32Aliases<RelayNetwork, AccountId>,
);

/// Means for transacting assets on this chain.
pub type CurrencyTransactor = CurrencyAdapter<
	// Use this currency:
	Balances,
	// Use this currency when it is a fungible asset matching the given location or name:
	IsConcrete<RelayLocation>,
	// Do a simple punn to convert an AccountId32 MultiLocation into a native chain account ID:
	LocationToAccountId,
	// Our chain's account ID type (we can't get away without mentioning it explicitly):
	AccountId,
	// We don't track any teleports.
	(),
>;

/// Means for transacting assets besides the native currency on this chain.
pub type FungiblesTransactor = FungiblesAdapter<
	// Use this fungibles implementation:
	Assets,
	// Use this currency when it is a fungible asset matching the given location or name:
	ConvertedConcreteAssetId<
		AssetIdPalletAssets,
		Balance,
		AsPrefixedGeneralIndex<CommonGoodAssetsPalletLocation, AssetIdPalletAssets, JustTry>,
		JustTry,
	>,
	// Convert an XCM MultiLocation into a local account id:
	LocationToAccountId,
	// Our chain's account ID type (we can't get away without mentioning it explicitly):
	AccountId,
	// We only want to allow teleports of known assets. We use non-zero issuance as an indication
	// that this asset is known.
	NonZeroIssuance<AccountId, Assets>,
	// The account to use for tracking teleports.
	CheckingAccount,
>;

/// Means for transacting assets on this chain.
pub type AssetTransactors = (CurrencyTransactor, FungiblesTransactor);

/// This is the type we use to convert an (incoming) XCM origin into a local `Origin` instance,
/// ready for dispatching a transaction with Xcm's `Transact`. There is an `OriginKind` which can
/// biases the kind of local `Origin` it will become.
pub type XcmOriginToTransactDispatchOrigin = (
	// Sovereign account converter; this attempts to derive an `AccountId` from the origin location
	// using `LocationToAccountId` and then turn that into the usual `Signed` origin. Useful for
	// foreign chains who want to have a local sovereign account on this chain which they control.
	SovereignSignedViaLocation<LocationToAccountId, Origin>,
	// Native converter for Relay-chain (Parent) location; will converts to a `Relay` origin when
	// recognized.
	RelayChainAsNative<RelayChainOrigin, Origin>,
	// Native converter for sibling Parachains; will convert to a `SiblingPara` origin when
	// recognized.
	SiblingParachainAsNative<cumulus_pallet_xcm::Origin, Origin>,
	// Native signed account converter; this just converts an `AccountId32` origin into a normal
	// `Origin::Signed` origin of the same 32-byte value.
	SignedAccountId32AsNative<RelayNetwork, Origin>,
	// Xcm origins can be represented natively under the Xcm pallet's Xcm origin.
	XcmPassthrough<Origin>,
);

parameter_types! {
	// One XCM operation is 1_000_000_000 weight - almost certainly a conservative estimate.
	pub UnitWeightCost: u64 = 1_000_000_000;
	pub const MaxInstructions: u32 = 100;
}

match_types! {
	pub type ParentOrParentsExecutivePlurality: impl Contains<MultiLocation> = {
		MultiLocation { parents: 1, interior: Here } |
		MultiLocation { parents: 1, interior: X1(Plurality { id: BodyId::Executive, .. }) }
	};
	pub type CommonGoodAssetsParachain: impl Contains<MultiLocation> = {
		MultiLocation { parents: 1, interior: X1(Parachain(1000)) }
	};
}

//TODO: move DenyThenTry to polkadot's xcm module.
/// Deny executing the xcm message if it matches any of the Deny filter regardless of anything else.
/// If it passes the Deny, and matches one of the Allow cases then it is let through.
pub struct DenyThenTry<Deny, Allow>(PhantomData<Deny>, PhantomData<Allow>)
where
	Deny: ShouldExecute,
	Allow: ShouldExecute;

impl<Deny, Allow> ShouldExecute for DenyThenTry<Deny, Allow>
where
	Deny: ShouldExecute,
	Allow: ShouldExecute,
{
	fn should_execute<RuntimeCall>(
		origin: &MultiLocation,
		message: &mut Xcm<RuntimeCall>,
		max_weight: XCMWeight,
		weight_credit: &mut XCMWeight,
	) -> Result<(), ()> {
		Deny::should_execute(origin, message, max_weight, weight_credit)?;
		Allow::should_execute(origin, message, max_weight, weight_credit)
	}
}

// See issue #5233
pub struct DenyReserveTransferToRelayChain;
impl ShouldExecute for DenyReserveTransferToRelayChain {
	fn should_execute<RuntimeCall>(
		origin: &MultiLocation,
		message: &mut Xcm<RuntimeCall>,
		_max_weight: XCMWeight,
		_weight_credit: &mut XCMWeight,
	) -> Result<(), ()> {
		if message.0.iter().any(|inst| {
			matches!(
				inst,
				InitiateReserveWithdraw {
					reserve: MultiLocation { parents: 1, interior: Here },
					..
				} | DepositReserveAsset { dest: MultiLocation { parents: 1, interior: Here }, .. } |
					TransferReserveAsset {
						dest: MultiLocation { parents: 1, interior: Here },
						..
					}
			)
		}) {
			return Err(()) // Deny
		}

		// allow reserve transfers to arrive from relay chain
		if matches!(origin, MultiLocation { parents: 1, interior: Here }) &&
			message.0.iter().any(|inst| matches!(inst, ReserveAssetDeposited { .. }))
		{
			log::warn!(
				target: "xcm::barriers",
				"Unexpected ReserveAssetDeposited from the relay chain",
			);
		}
		// Permit everything else
		Ok(())
	}
}

pub type Barrier = DenyThenTry<
	DenyReserveTransferToRelayChain,
	(
		TakeWeightCredit,
		AllowTopLevelPaidExecutionFrom<Everything>,
		// Parent and its exec plurality get free execution
		AllowUnpaidExecutionFrom<ParentOrParentsExecutivePlurality>,
		// Assets Common Good parachain gets free execution
		AllowUnpaidExecutionFrom<CommonGoodAssetsParachain>,
		// Expected responses are OK.
		AllowKnownQueryResponses<PolkadotXcm>,
		// Subscriptions for version tracking are OK.
		AllowSubscriptionsFrom<Everything>,
	),
>;

/// Type alias to conveniently refer to `frame_system`'s `Config::AccountId`.
pub type AccountIdOf<R> = <R as frame_system::Config>::AccountId;

/// Asset filter that allows all assets from a certain location.
pub struct AssetsFrom<T>(PhantomData<T>);
impl<T: Get<MultiLocation>> FilterAssetLocation for AssetsFrom<T> {
	fn filter_asset_location(asset: &MultiAsset, origin: &MultiLocation) -> bool {
		let loc = T::get();
		&loc == origin &&
			matches!(asset, MultiAsset { id: AssetId::Concrete(asset_loc), fun: Fungible(_a) }
			if asset_loc.match_and_split(&loc).is_some())
	}
}

/// Allow checking in assets that have issuance > 0.
pub struct NonZeroIssuance<AccountId, Assets>(PhantomData<(AccountId, Assets)>);
impl<AccountId, Assets> Contains<<Assets as fungibles::Inspect<AccountId>>::AssetId>
	for NonZeroIssuance<AccountId, Assets>
where
	Assets: fungibles::Inspect<AccountId>,
{
	fn contains(id: &<Assets as fungibles::Inspect<AccountId>>::AssetId) -> bool {
		!Assets::total_issuance(*id).is_zero()
	}
}

/// A `HandleCredit` implementation that naively transfers the fees to the block author.
/// Will drop and burn the assets in case the transfer fails.
pub struct AssetsToBlockAuthor<R>(PhantomData<R>);
impl<R> HandleCredit<AccountIdOf<R>, pallet_assets::Pallet<R>> for AssetsToBlockAuthor<R>
where
	R: pallet_authorship::Config + pallet_assets::Config,
	AccountIdOf<R>:
		From<polkadot_primitives::v2::AccountId> + Into<polkadot_primitives::v2::AccountId>,
{
	fn handle_credit(credit: CreditOf<AccountIdOf<R>, pallet_assets::Pallet<R>>) {
		if let Some(author) = pallet_authorship::Pallet::<R>::author() {
			// In case of error: Will drop the result triggering the `OnDrop` of the imbalance.
			let _ = pallet_assets::Pallet::<R>::resolve(&author, credit);
		}
	}
}

pub trait Reserve {
	/// Returns assets reserve location.
	fn reserve(&self) -> Option<MultiLocation>;
}

// Takes the chain part of a MultiAsset
impl Reserve for MultiAsset {
	fn reserve(&self) -> Option<MultiLocation> {
		if let AssetId::Concrete(location) = self.id.clone() {
			let first_interior = location.first_interior();
			let parents = location.parent_count();
			match (parents, first_interior.clone()) {
				(0, Some(Parachain(id))) => Some(MultiLocation::new(0, X1(Parachain(id.clone())))),
				(1, Some(Parachain(id))) => Some(MultiLocation::new(1, X1(Parachain(id.clone())))),
				(1, _) => Some(MultiLocation::parent()),
				_ => None,
			}
		} else {
			None
		}
	}
}

/// A `FilterAssetLocation` implementation. Filters multi native assets whose
/// reserve is same with `origin`.
pub struct MultiNativeAsset;
impl FilterAssetLocation for MultiNativeAsset {
	fn filter_asset_location(asset: &MultiAsset, origin: &MultiLocation) -> bool {
		if let Some(ref reserve) = asset.reserve() {
			if reserve == origin {
				return true
			}
		}
		false
	}
}

parameter_types! {
	pub CommonGoodAssetsLocation: MultiLocation = MultiLocation::new(1, X1(Parachain(1000)));
	// ALWAYS ensure that the index in PalletInstance stays up-to-date with
	// Statemint's Assets pallet index
	pub CommonGoodAssetsPalletLocation: MultiLocation =
		MultiLocation::new(1, X2(Parachain(1000), PalletInstance(50)));
	pub CheckingAccount: AccountId = PolkadotXcm::check_account();
}

pub type Reserves = (NativeAsset, AssetsFrom<CommonGoodAssetsLocation>);

pub struct XcmConfig;
impl xcm_executor::Config for XcmConfig {
	type RuntimeCall = RuntimeCall;
	type XcmSender = XcmRouter;
	// How to withdraw and deposit an asset.
	type AssetTransactor = AssetTransactors;
	type OriginConverter = XcmOriginToTransactDispatchOrigin;
	type IsReserve = MultiNativeAsset; // TODO: maybe needed to be replaced by Reserves
	type IsTeleporter = NativeAsset;
	type LocationInverter = LocationInverter<Ancestry>;
	type Barrier = Barrier;
	type Weigher = FixedWeightBounds<UnitWeightCost, RuntimeCall, MaxInstructions>;
	type Trader =
		UsingComponents<WeightToFee, RelayLocation, AccountId, Balances, ToAuthor<Runtime>>;
	type ResponseHandler = PolkadotXcm;
	type AssetTrap = PolkadotXcm;
	type AssetClaims = PolkadotXcm;
	type SubscriptionService = PolkadotXcm;
}

/// No local origins on this chain are allowed to dispatch XCM sends/executions.
pub type LocalOriginToLocation = SignedToAccountId32<Origin, AccountId, RelayNetwork>;

/// The means for routing XCM messages which are not for local execution into the right message
/// queues.
pub type XcmRouter = (
	// Two routers - use UMP to communicate with the relay chain:
	cumulus_primitives_utility::ParentAsUmp<ParachainSystem, PolkadotXcm>,
	// ..and XCMP to communicate with the sibling chains.
	XcmpQueue,
);

impl pallet_xcm::Config for Runtime {
	type RuntimeEvent = RuntimeEvent;
	type SendXcmOrigin = EnsureXcmOrigin<Origin, LocalOriginToLocation>;
	type XcmRouter = XcmRouter;
	type ExecuteXcmOrigin = EnsureXcmOrigin<Origin, LocalOriginToLocation>;
	type XcmExecuteFilter = Nothing;
	// ^ Disable dispatchable execute on the XCM pallet.
	// Needs to be `Everything` for local testing.
	type XcmExecutor = XcmExecutor<XcmConfig>;
	type XcmTeleportFilter = Everything;
	type XcmReserveTransferFilter = Everything;
	type Weigher = FixedWeightBounds<UnitWeightCost, RuntimeCall, MaxInstructions>;
	type LocationInverter = LocationInverter<Ancestry>;
	type Origin = Origin;
	type RuntimeCall = RuntimeCall;

	const VERSION_DISCOVERY_QUEUE_SIZE: u32 = 100;
	// ^ Override for AdvertisedXcmVersion default
	type AdvertisedXcmVersion = pallet_xcm::CurrentXcmVersion;
}

impl cumulus_pallet_xcm::Config for Runtime {
	type RuntimeEvent = RuntimeEvent;
	type XcmExecutor = XcmExecutor<XcmConfig>;
}