AllowHrmpNotificationsFromRelayChain barrier for HRMP notifications from the relaychain (#4156)

This PR:
- introduces `AllowHrmpNotificationsFromRelayChain` barrier for allowing
HRMP notifications just from the relay chain (to fulfill safety
assumptions -
[see](https://github.com/paritytech/polkadot-sdk/blob/master/polkadot/xcm/src/v4/mod.rs#L532))
- sets it up for all testnet SP parachains

Continuation of: https://github.com/paritytech/polkadot-sdk/pull/3696

cumulus/parachains/runtimes/assets/asset-hub-rococo/src/xcm_config.rs

@@ -49,17 +49,17 @@ use testnet_parachains_constants::rococo::snowbridge::{
 };
 use xcm::latest::prelude::*;
 use xcm_builder::{
-	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowKnownQueryResponses,
-	AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom, DenyReserveTransferToRelayChain,
-	DenyThenTry, DescribeAllTerminal, DescribeFamily, EnsureXcmOrigin, FrameTransactionalProcessor,
-	FungibleAdapter, FungiblesAdapter, GlobalConsensusParachainConvertsFor, HashedDescription,
-	IsConcrete, LocalMint, NetworkExportTableItem, NoChecking, NonFungiblesAdapter,
-	ParentAsSuperuser, ParentIsPreset, RelayChainAsNative, SiblingParachainAsNative,
-	SiblingParachainConvertsVia, SignedAccountId32AsNative, SignedToAccountId32,
-	SovereignPaidRemoteExporter, SovereignSignedViaLocation, StartsWith,
-	StartsWithExplicitGlobalConsensus, TakeWeightCredit, TrailingSetTopicAsId, UsingComponents,
-	WeightInfoBounds, WithComputedOrigin, WithUniqueTopic, XcmFeeManagerFromComponents,
-	XcmFeeToAccount,
+	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowHrmpNotificationsFromRelayChain,
+	AllowKnownQueryResponses, AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom,
+	DenyReserveTransferToRelayChain, DenyThenTry, DescribeAllTerminal, DescribeFamily,
+	EnsureXcmOrigin, FrameTransactionalProcessor, FungibleAdapter, FungiblesAdapter,
+	GlobalConsensusParachainConvertsFor, HashedDescription, IsConcrete, LocalMint,
+	NetworkExportTableItem, NoChecking, NonFungiblesAdapter, ParentAsSuperuser, ParentIsPreset,
+	RelayChainAsNative, SiblingParachainAsNative, SiblingParachainConvertsVia,
+	SignedAccountId32AsNative, SignedToAccountId32, SovereignPaidRemoteExporter,
+	SovereignSignedViaLocation, StartsWith, StartsWithExplicitGlobalConsensus, TakeWeightCredit,
+	TrailingSetTopicAsId, UsingComponents, WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
+	XcmFeeManagerFromComponents, XcmFeeToAccount,
 };
 use xcm_executor::XcmExecutor;
 
@@ -285,6 +285,8 @@ pub type Barrier = TrailingSetTopicAsId<
 					)>,
 					// Subscriptions for version tracking are OK.
 					AllowSubscriptionsFrom<ParentRelayOrSiblingParachains>,
+					// HRMP notifications from the relay chain are OK.
+					AllowHrmpNotificationsFromRelayChain,
 				),
 				UniversalLocation,
 				ConstU32<8>,

cumulus/parachains/runtimes/assets/asset-hub-westend/src/xcm_config.rs

@@ -45,10 +45,10 @@ use polkadot_runtime_common::xcm_sender::ExponentialPrice;
 use sp_runtime::traits::{AccountIdConversion, ConvertInto};
 use xcm::latest::prelude::*;
 use xcm_builder::{
-	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowKnownQueryResponses,
-	AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom, DenyReserveTransferToRelayChain,
-	DenyThenTry, DescribeFamily, DescribePalletTerminal, EnsureXcmOrigin,
-	FrameTransactionalProcessor, FungibleAdapter, FungiblesAdapter,
+	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowHrmpNotificationsFromRelayChain,
+	AllowKnownQueryResponses, AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom,
+	DenyReserveTransferToRelayChain, DenyThenTry, DescribeFamily, DescribePalletTerminal,
+	EnsureXcmOrigin, FrameTransactionalProcessor, FungibleAdapter, FungiblesAdapter,
 	GlobalConsensusParachainConvertsFor, HashedDescription, IsConcrete, LocalMint,
 	NetworkExportTableItem, NoChecking, NonFungiblesAdapter, ParentAsSuperuser, ParentIsPreset,
 	RelayChainAsNative, SiblingParachainAsNative, SiblingParachainConvertsVia,
@@ -299,6 +299,8 @@ pub type Barrier = TrailingSetTopicAsId<
 					)>,
 					// Subscriptions for version tracking are OK.
 					AllowSubscriptionsFrom<Everything>,
+					// HRMP notifications from the relay chain are OK.
+					AllowHrmpNotificationsFromRelayChain,
 				),
 				UniversalLocation,
 				ConstU32<8>,

cumulus/parachains/runtimes/bridge-hubs/bridge-hub-rococo/src/xcm_config.rs

@@ -46,12 +46,13 @@ use testnet_parachains_constants::rococo::snowbridge::EthereumNetwork;
 use xcm::latest::prelude::*;
 use xcm_builder::{
 	deposit_or_burn_fee, AccountId32Aliases, AllowExplicitUnpaidExecutionFrom,
-	AllowKnownQueryResponses, AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom,
-	DenyReserveTransferToRelayChain, DenyThenTry, EnsureXcmOrigin, FrameTransactionalProcessor,
-	FungibleAdapter, HandleFee, IsConcrete, ParentAsSuperuser, ParentIsPreset, RelayChainAsNative,
-	SiblingParachainAsNative, SiblingParachainConvertsVia, SignedAccountId32AsNative,
-	SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit, TrailingSetTopicAsId,
-	UsingComponents, WeightInfoBounds, WithComputedOrigin, WithUniqueTopic, XcmFeeToAccount,
+	AllowHrmpNotificationsFromRelayChain, AllowKnownQueryResponses, AllowSubscriptionsFrom,
+	AllowTopLevelPaidExecutionFrom, DenyReserveTransferToRelayChain, DenyThenTry, EnsureXcmOrigin,
+	FrameTransactionalProcessor, FungibleAdapter, HandleFee, IsConcrete, ParentAsSuperuser,
+	ParentIsPreset, RelayChainAsNative, SiblingParachainAsNative, SiblingParachainConvertsVia,
+	SignedAccountId32AsNative, SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit,
+	TrailingSetTopicAsId, UsingComponents, WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
+	XcmFeeToAccount,
 };
 use xcm_executor::{
 	traits::{FeeManager, FeeReason, FeeReason::Export, TransactAsset},
@@ -150,6 +151,8 @@ pub type Barrier = TrailingSetTopicAsId<
 					)>,
 					// Subscriptions for version tracking are OK.
 					AllowSubscriptionsFrom<ParentRelayOrSiblingParachains>,
+					// HRMP notifications from the relay chain are OK.
+					AllowHrmpNotificationsFromRelayChain,
 				),
 				UniversalLocation,
 				ConstU32<8>,

cumulus/parachains/runtimes/bridge-hubs/bridge-hub-westend/src/xcm_config.rs

@@ -38,14 +38,14 @@ use polkadot_runtime_common::xcm_sender::ExponentialPrice;
 use sp_runtime::traits::AccountIdConversion;
 use xcm::latest::prelude::*;
 use xcm_builder::{
-	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowKnownQueryResponses,
-	AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom, DenyReserveTransferToRelayChain,
-	DenyThenTry, EnsureXcmOrigin, FrameTransactionalProcessor, FungibleAdapter, IsConcrete,
-	ParentAsSuperuser, ParentIsPreset, RelayChainAsNative, SiblingParachainAsNative,
-	SiblingParachainConvertsVia, SignedAccountId32AsNative, SignedToAccountId32,
-	SovereignSignedViaLocation, TakeWeightCredit, TrailingSetTopicAsId, UsingComponents,
-	WeightInfoBounds, WithComputedOrigin, WithUniqueTopic, XcmFeeManagerFromComponents,
-	XcmFeeToAccount,
+	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowHrmpNotificationsFromRelayChain,
+	AllowKnownQueryResponses, AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom,
+	DenyReserveTransferToRelayChain, DenyThenTry, EnsureXcmOrigin, FrameTransactionalProcessor,
+	FungibleAdapter, IsConcrete, ParentAsSuperuser, ParentIsPreset, RelayChainAsNative,
+	SiblingParachainAsNative, SiblingParachainConvertsVia, SignedAccountId32AsNative,
+	SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit, TrailingSetTopicAsId,
+	UsingComponents, WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
+	XcmFeeManagerFromComponents, XcmFeeToAccount,
 };
 use xcm_executor::XcmExecutor;
 
@@ -139,6 +139,8 @@ pub type Barrier = TrailingSetTopicAsId<
 					)>,
 					// Subscriptions for version tracking are OK.
 					AllowSubscriptionsFrom<ParentRelayOrSiblingParachains>,
+					// HRMP notifications from the relay chain are OK.
+					AllowHrmpNotificationsFromRelayChain,
 				),
 				UniversalLocation,
 				ConstU32<8>,

cumulus/parachains/runtimes/collectives/collectives-westend/src/xcm_config.rs

@@ -35,14 +35,15 @@ use polkadot_runtime_common::xcm_sender::ExponentialPrice;
 use westend_runtime_constants::xcm as xcm_constants;
 use xcm::latest::prelude::*;
 use xcm_builder::{
-	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowKnownQueryResponses,
-	AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom, DenyReserveTransferToRelayChain,
-	DenyThenTry, EnsureXcmOrigin, FixedWeightBounds, FrameTransactionalProcessor, FungibleAdapter,
-	IsConcrete, LocatableAssetId, OriginToPluralityVoice, ParentAsSuperuser, ParentIsPreset,
-	RelayChainAsNative, SiblingParachainAsNative, SiblingParachainConvertsVia,
-	SignedAccountId32AsNative, SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit,
-	TrailingSetTopicAsId, UsingComponents, WithComputedOrigin, WithUniqueTopic,
-	XcmFeeManagerFromComponents, XcmFeeToAccount,
+	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowHrmpNotificationsFromRelayChain,
+	AllowKnownQueryResponses, AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom,
+	DenyReserveTransferToRelayChain, DenyThenTry, EnsureXcmOrigin, FixedWeightBounds,
+	FrameTransactionalProcessor, FungibleAdapter, IsConcrete, LocatableAssetId,
+	OriginToPluralityVoice, ParentAsSuperuser, ParentIsPreset, RelayChainAsNative,
+	SiblingParachainAsNative, SiblingParachainConvertsVia, SignedAccountId32AsNative,
+	SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit, TrailingSetTopicAsId,
+	UsingComponents, WithComputedOrigin, WithUniqueTopic, XcmFeeManagerFromComponents,
+	XcmFeeToAccount,
 };
 use xcm_executor::XcmExecutor;
 
@@ -156,6 +157,8 @@ pub type Barrier = TrailingSetTopicAsId<
 					AllowExplicitUnpaidExecutionFrom<ParentOrParentsPlurality>,
 					// Subscriptions for version tracking are OK.
 					AllowSubscriptionsFrom<ParentRelayOrSiblingParachains>,
+					// HRMP notifications from the relay chain are OK.
+					AllowHrmpNotificationsFromRelayChain,
 				),
 				UniversalLocation,
 				ConstU32<8>,

cumulus/parachains/runtimes/contracts/contracts-rococo/src/xcm_config.rs

@@ -38,14 +38,14 @@ use sp_runtime::traits::AccountIdConversion;
 use testnet_parachains_constants::rococo::currency::CENTS;
 use xcm::latest::prelude::*;
 use xcm_builder::{
-	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowKnownQueryResponses,
-	AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom, DenyReserveTransferToRelayChain,
-	DenyThenTry, EnsureXcmOrigin, FixedWeightBounds, FrameTransactionalProcessor, FungibleAdapter,
-	IsConcrete, NativeAsset, ParentAsSuperuser, ParentIsPreset, RelayChainAsNative,
-	SiblingParachainAsNative, SiblingParachainConvertsVia, SignedAccountId32AsNative,
-	SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit, TrailingSetTopicAsId,
-	UsingComponents, WithComputedOrigin, WithUniqueTopic, XcmFeeManagerFromComponents,
-	XcmFeeToAccount,
+	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowHrmpNotificationsFromRelayChain,
+	AllowKnownQueryResponses, AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom,
+	DenyReserveTransferToRelayChain, DenyThenTry, EnsureXcmOrigin, FixedWeightBounds,
+	FrameTransactionalProcessor, FungibleAdapter, IsConcrete, NativeAsset, ParentAsSuperuser,
+	ParentIsPreset, RelayChainAsNative, SiblingParachainAsNative, SiblingParachainConvertsVia,
+	SignedAccountId32AsNative, SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit,
+	TrailingSetTopicAsId, UsingComponents, WithComputedOrigin, WithUniqueTopic,
+	XcmFeeManagerFromComponents, XcmFeeToAccount,
 };
 use xcm_executor::XcmExecutor;
 
@@ -149,6 +149,8 @@ pub type Barrier = TrailingSetTopicAsId<
 					)>,
 					// Subscriptions for version tracking are OK.
 					AllowSubscriptionsFrom<ParentRelayOrSiblingParachains>,
+					// HRMP notifications from the relay chain are OK.
+					AllowHrmpNotificationsFromRelayChain,
 				),
 				UniversalLocation,
 				ConstU32<8>,

cumulus/parachains/runtimes/coretime/coretime-rococo/src/xcm_config.rs

@@ -39,13 +39,13 @@ use polkadot_runtime_common::xcm_sender::ExponentialPrice;
 use sp_runtime::traits::AccountIdConversion;
 use xcm::latest::prelude::*;
 use xcm_builder::{
-	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowKnownQueryResponses,
-	AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom, DenyReserveTransferToRelayChain,
-	DenyThenTry, EnsureXcmOrigin, FrameTransactionalProcessor, FungibleAdapter, IsConcrete,
-	NonFungibleAdapter, ParentAsSuperuser, ParentIsPreset, RelayChainAsNative,
-	SiblingParachainAsNative, SiblingParachainConvertsVia, SignedAccountId32AsNative,
-	SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit, TrailingSetTopicAsId,
-	UsingComponents, WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
+	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowHrmpNotificationsFromRelayChain,
+	AllowKnownQueryResponses, AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom,
+	DenyReserveTransferToRelayChain, DenyThenTry, EnsureXcmOrigin, FrameTransactionalProcessor,
+	FungibleAdapter, IsConcrete, NonFungibleAdapter, ParentAsSuperuser, ParentIsPreset,
+	RelayChainAsNative, SiblingParachainAsNative, SiblingParachainConvertsVia,
+	SignedAccountId32AsNative, SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit,
+	TrailingSetTopicAsId, UsingComponents, WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
 	XcmFeeManagerFromComponents, XcmFeeToAccount,
 };
 use xcm_executor::XcmExecutor;
@@ -156,6 +156,8 @@ pub type Barrier = TrailingSetTopicAsId<
 					AllowExplicitUnpaidExecutionFrom<ParentOrParentsPlurality>,
 					// Subscriptions for version tracking are OK.
 					AllowSubscriptionsFrom<ParentRelayOrSiblingParachains>,
+					// HRMP notifications from the relay chain are OK.
+					AllowHrmpNotificationsFromRelayChain,
 				),
 				UniversalLocation,
 				ConstU32<8>,

cumulus/parachains/runtimes/coretime/coretime-westend/src/xcm_config.rs

@@ -39,13 +39,13 @@ use polkadot_runtime_common::xcm_sender::ExponentialPrice;
 use sp_runtime::traits::AccountIdConversion;
 use xcm::latest::prelude::*;
 use xcm_builder::{
-	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowKnownQueryResponses,
-	AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom, DenyReserveTransferToRelayChain,
-	DenyThenTry, EnsureXcmOrigin, FrameTransactionalProcessor, FungibleAdapter, IsConcrete,
-	NonFungibleAdapter, ParentAsSuperuser, ParentIsPreset, RelayChainAsNative,
-	SiblingParachainAsNative, SiblingParachainConvertsVia, SignedAccountId32AsNative,
-	SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit, TrailingSetTopicAsId,
-	UsingComponents, WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
+	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowHrmpNotificationsFromRelayChain,
+	AllowKnownQueryResponses, AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom,
+	DenyReserveTransferToRelayChain, DenyThenTry, EnsureXcmOrigin, FrameTransactionalProcessor,
+	FungibleAdapter, IsConcrete, NonFungibleAdapter, ParentAsSuperuser, ParentIsPreset,
+	RelayChainAsNative, SiblingParachainAsNative, SiblingParachainConvertsVia,
+	SignedAccountId32AsNative, SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit,
+	TrailingSetTopicAsId, UsingComponents, WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
 	XcmFeeManagerFromComponents, XcmFeeToAccount,
 };
 use xcm_executor::XcmExecutor;
@@ -164,6 +164,8 @@ pub type Barrier = TrailingSetTopicAsId<
 					AllowExplicitUnpaidExecutionFrom<(ParentOrParentsPlurality, FellowsPlurality)>,
 					// Subscriptions for version tracking are OK.
 					AllowSubscriptionsFrom<ParentRelayOrSiblingParachains>,
+					// HRMP notifications from the relay chain are OK.
+					AllowHrmpNotificationsFromRelayChain,
 				),
 				UniversalLocation,
 				ConstU32<8>,

cumulus/parachains/runtimes/people/people-rococo/src/xcm_config.rs

@@ -36,13 +36,13 @@ use polkadot_parachain_primitives::primitives::Sibling;
 use sp_runtime::traits::AccountIdConversion;
 use xcm::latest::prelude::*;
 use xcm_builder::{
-	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowKnownQueryResponses,
-	AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom, DenyReserveTransferToRelayChain,
-	DenyThenTry, DescribeTerminus, EnsureXcmOrigin, FrameTransactionalProcessor, FungibleAdapter,
-	HashedDescription, IsConcrete, ParentAsSuperuser, ParentIsPreset, RelayChainAsNative,
-	SiblingParachainAsNative, SiblingParachainConvertsVia, SignedAccountId32AsNative,
-	SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit, TrailingSetTopicAsId,
-	UsingComponents, WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
+	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowHrmpNotificationsFromRelayChain,
+	AllowKnownQueryResponses, AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom,
+	DenyReserveTransferToRelayChain, DenyThenTry, DescribeTerminus, EnsureXcmOrigin,
+	FrameTransactionalProcessor, FungibleAdapter, HashedDescription, IsConcrete, ParentAsSuperuser,
+	ParentIsPreset, RelayChainAsNative, SiblingParachainAsNative, SiblingParachainConvertsVia,
+	SignedAccountId32AsNative, SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit,
+	TrailingSetTopicAsId, UsingComponents, WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
 	XcmFeeManagerFromComponents, XcmFeeToAccount,
 };
 use xcm_executor::XcmExecutor;
@@ -165,6 +165,8 @@ pub type Barrier = TrailingSetTopicAsId<
 					AllowExplicitUnpaidExecutionFrom<ParentOrParentsPlurality>,
 					// Subscriptions for version tracking are OK.
 					AllowSubscriptionsFrom<ParentRelayOrSiblingParachains>,
+					// HRMP notifications from the relay chain are OK.
+					AllowHrmpNotificationsFromRelayChain,
 				),
 				UniversalLocation,
 				ConstU32<8>,

cumulus/parachains/runtimes/people/people-westend/src/xcm_config.rs

@@ -36,13 +36,13 @@ use polkadot_parachain_primitives::primitives::Sibling;
 use sp_runtime::traits::AccountIdConversion;
 use xcm::latest::prelude::*;
 use xcm_builder::{
-	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowKnownQueryResponses,
-	AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom, DenyReserveTransferToRelayChain,
-	DenyThenTry, DescribeTerminus, EnsureXcmOrigin, FrameTransactionalProcessor, FungibleAdapter,
-	HashedDescription, IsConcrete, ParentAsSuperuser, ParentIsPreset, RelayChainAsNative,
-	SiblingParachainAsNative, SiblingParachainConvertsVia, SignedAccountId32AsNative,
-	SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit, TrailingSetTopicAsId,
-	UsingComponents, WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
+	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowHrmpNotificationsFromRelayChain,
+	AllowKnownQueryResponses, AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom,
+	DenyReserveTransferToRelayChain, DenyThenTry, DescribeTerminus, EnsureXcmOrigin,
+	FrameTransactionalProcessor, FungibleAdapter, HashedDescription, IsConcrete, ParentAsSuperuser,
+	ParentIsPreset, RelayChainAsNative, SiblingParachainAsNative, SiblingParachainConvertsVia,
+	SignedAccountId32AsNative, SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit,
+	TrailingSetTopicAsId, UsingComponents, WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
 	XcmFeeManagerFromComponents, XcmFeeToAccount,
 };
 use xcm_executor::XcmExecutor;
@@ -173,6 +173,8 @@ pub type Barrier = TrailingSetTopicAsId<
 					AllowExplicitUnpaidExecutionFrom<(ParentOrParentsPlurality, FellowsPlurality)>,
 					// Subscriptions for version tracking are OK.
 					AllowSubscriptionsFrom<ParentRelayOrSiblingParachains>,
+					// HRMP notifications from the relay chain are OK.
+					AllowHrmpNotificationsFromRelayChain,
 				),
 				UniversalLocation,
 				ConstU32<8>,

cumulus/parachains/runtimes/testing/penpal/src/xcm_config.rs

@@ -43,14 +43,15 @@ use polkadot_runtime_common::{impls::ToAuthor, xcm_sender::ExponentialPrice};
 use sp_runtime::traits::{AccountIdConversion, ConvertInto, Identity, TryConvertInto};
 use xcm::latest::prelude::*;
 use xcm_builder::{
-	AccountId32Aliases, AllowKnownQueryResponses, AllowSubscriptionsFrom,
-	AllowTopLevelPaidExecutionFrom, AsPrefixedGeneralIndex, ConvertedConcreteId, EnsureXcmOrigin,
-	FixedWeightBounds, FrameTransactionalProcessor, FungibleAdapter, FungiblesAdapter, IsConcrete,
-	LocalMint, NativeAsset, NoChecking, ParentAsSuperuser, ParentIsPreset, RelayChainAsNative,
-	SiblingParachainAsNative, SiblingParachainConvertsVia, SignedAccountId32AsNative,
-	SignedToAccountId32, SovereignSignedViaLocation, StartsWith, TakeWeightCredit,
-	TrailingSetTopicAsId, UsingComponents, WithComputedOrigin, WithUniqueTopic,
-	XcmFeeManagerFromComponents, XcmFeeToAccount,
+	AccountId32Aliases, AllowHrmpNotificationsFromRelayChain, AllowKnownQueryResponses,
+	AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom, AsPrefixedGeneralIndex,
+	ConvertedConcreteId, EnsureXcmOrigin, FixedWeightBounds, FrameTransactionalProcessor,
+	FungibleAdapter, FungiblesAdapter, IsConcrete, LocalMint, NativeAsset, NoChecking,
+	ParentAsSuperuser, ParentIsPreset, RelayChainAsNative, SiblingParachainAsNative,
+	SiblingParachainConvertsVia, SignedAccountId32AsNative, SignedToAccountId32,
+	SovereignSignedViaLocation, StartsWith, TakeWeightCredit, TrailingSetTopicAsId,
+	UsingComponents, WithComputedOrigin, WithUniqueTopic, XcmFeeManagerFromComponents,
+	XcmFeeToAccount,
 };
 use xcm_executor::{traits::JustTry, XcmExecutor};
 
@@ -217,6 +218,8 @@ pub type Barrier = TrailingSetTopicAsId<(
 			AllowTopLevelPaidExecutionFrom<Everything>,
 			// Subscriptions for version tracking are OK.
 			AllowSubscriptionsFrom<Everything>,
+			// HRMP notifications from the relay chain are OK.
+			AllowHrmpNotificationsFromRelayChain,
 		),
 		UniversalLocation,
 		ConstU32<8>,

cumulus/parachains/runtimes/testing/rococo-parachain/src/lib.rs

@@ -74,9 +74,9 @@ use parachains_common::{
 	AccountId, AssetIdForTrustBackedAssets, Signature,
 };
 use xcm_builder::{
-	AllowKnownQueryResponses, AllowSubscriptionsFrom, AsPrefixedGeneralIndex, ConvertedConcreteId,
-	FrameTransactionalProcessor, FungiblesAdapter, LocalMint, TrailingSetTopicAsId,
-	WithUniqueTopic,
+	AllowHrmpNotificationsFromRelayChain, AllowKnownQueryResponses, AllowSubscriptionsFrom,
+	AsPrefixedGeneralIndex, ConvertedConcreteId, FrameTransactionalProcessor, FungiblesAdapter,
+	LocalMint, TrailingSetTopicAsId, WithUniqueTopic,
 };
 use xcm_executor::traits::JustTry;
 
@@ -444,6 +444,8 @@ pub type Barrier = TrailingSetTopicAsId<(
 	AllowKnownQueryResponses<PolkadotXcm>,
 	// Subscriptions for version tracking are OK.
 	AllowSubscriptionsFrom<Everything>,
+	// HRMP notifications from the relay chain are OK.
+	AllowHrmpNotificationsFromRelayChain,
 )>;
 
 parameter_types! {

polkadot/runtime/common/src/lib.rs

@@ -14,7 +14,7 @@
 // You should have received a copy of the GNU General Public License
 // along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.
 
-//! Common runtime code for Polkadot and Kusama.
+//! Common runtime code for the Relay Chain, e.g. Rococo, Westend, Polkadot, Kusama ...
 
 #![cfg_attr(not(feature = "std"), no_std)]
 

polkadot/xcm/xcm-builder/src/barriers.rs

@@ -399,6 +399,41 @@ impl<T: Contains<Location>> ShouldExecute for AllowSubscriptionsFrom<T> {
 	}
 }
 
+/// Allows execution for the Relay Chain origin (represented as `Location::parent()`) if it is just
+/// a straight `HrmpNewChannelOpenRequest`, `HrmpChannelAccepted`, or `HrmpChannelClosing`
+/// instruction.
+///
+/// Note: This barrier fulfills safety recommendations for the mentioned instructions - see their
+/// documentation.
+pub struct AllowHrmpNotificationsFromRelayChain;
+impl ShouldExecute for AllowHrmpNotificationsFromRelayChain {
+	fn should_execute<RuntimeCall>(
+		origin: &Location,
+		instructions: &mut [Instruction<RuntimeCall>],
+		_max_weight: Weight,
+		_properties: &mut Properties,
+	) -> Result<(), ProcessMessageError> {
+		log::trace!(
+			target: "xcm::barriers",
+			"AllowHrmpNotificationsFromRelayChain origin: {:?}, instructions: {:?}, max_weight: {:?}, properties: {:?}",
+			origin, instructions, _max_weight, _properties,
+		);
+		// accept only the Relay Chain
+		ensure!(matches!(origin.unpack(), (1, [])), ProcessMessageError::Unsupported);
+		// accept only HRMP notifications and nothing else
+		instructions
+			.matcher()
+			.assert_remaining_insts(1)?
+			.match_next_inst(|inst| match inst {
+				HrmpNewChannelOpenRequest { .. } |
+				HrmpChannelAccepted { .. } |
+				HrmpChannelClosing { .. } => Ok(()),
+				_ => Err(ProcessMessageError::BadFormat),
+			})?;
+		Ok(())
+	}
+}
+
 /// Deny executing the XCM 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>)

polkadot/xcm/xcm-builder/src/lib.rs

@@ -35,10 +35,11 @@ pub use asset_conversion::{
 
 mod barriers;
 pub use barriers::{
-	AllowExplicitUnpaidExecutionFrom, AllowKnownQueryResponses, AllowSubscriptionsFrom,
-	AllowTopLevelPaidExecutionFrom, AllowUnpaidExecutionFrom, DenyReserveTransferToRelayChain,
-	DenyThenTry, IsChildSystemParachain, IsParentsOnly, IsSiblingSystemParachain,
-	RespectSuspension, TakeWeightCredit, TrailingSetTopicAsId, WithComputedOrigin,
+	AllowExplicitUnpaidExecutionFrom, AllowHrmpNotificationsFromRelayChain,
+	AllowKnownQueryResponses, AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom,
+	AllowUnpaidExecutionFrom, DenyReserveTransferToRelayChain, DenyThenTry, IsChildSystemParachain,
+	IsParentsOnly, IsSiblingSystemParachain, RespectSuspension, TakeWeightCredit,
+	TrailingSetTopicAsId, WithComputedOrigin,
 };
 
 mod controller;

polkadot/xcm/xcm-builder/src/tests/barriers.rs

@@ -315,56 +315,150 @@ fn allow_subscriptions_from_should_work() {
 	// allow only parent
 	AllowSubsFrom::set(vec![Location::parent()]);
 
-	let valid_xcm_1 = Xcm::<TestCall>(vec![SubscribeVersion {
-		query_id: 42,
-		max_response_weight: Weight::from_parts(5000, 5000),
-	}]);
-	let valid_xcm_2 = Xcm::<TestCall>(vec![UnsubscribeVersion]);
-	let invalid_xcm_1 = Xcm::<TestCall>(vec![
-		SetAppendix(Xcm(vec![])),
-		SubscribeVersion { query_id: 42, max_response_weight: Weight::from_parts(5000, 5000) },
-	]);
-	let invalid_xcm_2 = Xcm::<TestCall>(vec![
-		SubscribeVersion { query_id: 42, max_response_weight: Weight::from_parts(5000, 5000) },
-		SetTopic([0; 32]),
-	]);
-
-	let test_data = vec![
-		(
-			valid_xcm_1.clone(),
-			Parachain(1).into_location(),
-			// not allowed origin
-			Err(ProcessMessageError::Unsupported),
-		),
-		(valid_xcm_1, Location::parent(), Ok(())),
-		(
-			valid_xcm_2.clone(),
-			Parachain(1).into_location(),
-			// not allowed origin
-			Err(ProcessMessageError::Unsupported),
-		),
-		(valid_xcm_2, Location::parent(), Ok(())),
-		(
-			invalid_xcm_1,
-			Location::parent(),
-			// invalid XCM
-			Err(ProcessMessageError::BadFormat),
-		),
-		(
-			invalid_xcm_2,
-			Location::parent(),
-			// invalid XCM
-			Err(ProcessMessageError::BadFormat),
-		),
-	];
-
-	for (mut message, origin, expected_result) in test_data {
-		let r = AllowSubscriptionsFrom::<IsInVec<AllowSubsFrom>>::should_execute(
-			&origin,
-			message.inner_mut(),
-			Weight::from_parts(10, 10),
-			&mut props(Weight::zero()),
+	// closure for (xcm, origin) testing with `AllowSubscriptionsFrom`
+	let assert_should_execute = |mut xcm: Vec<Instruction<()>>, origin, expected_result| {
+		assert_eq!(
+			AllowSubscriptionsFrom::<IsInVec<AllowSubsFrom>>::should_execute(
+				&origin,
+				&mut xcm,
+				Weight::from_parts(10, 10),
+				&mut props(Weight::zero()),
+			),
+			expected_result
 		);
-		assert_eq!(r, expected_result, "Failed for origin: {origin:?} and message: {message:?}");
-	}
+	};
+
+	// invalid origin
+	assert_should_execute(
+		vec![SubscribeVersion {
+			query_id: Default::default(),
+			max_response_weight: Default::default(),
+		}],
+		Parachain(1).into_location(),
+		Err(ProcessMessageError::Unsupported),
+	);
+	assert_should_execute(
+		vec![UnsubscribeVersion],
+		Parachain(1).into_location(),
+		Err(ProcessMessageError::Unsupported),
+	);
+
+	// invalid XCM (unexpected instruction before)
+	assert_should_execute(
+		vec![
+			SetAppendix(Xcm(vec![])),
+			SubscribeVersion {
+				query_id: Default::default(),
+				max_response_weight: Default::default(),
+			},
+		],
+		Location::parent(),
+		Err(ProcessMessageError::BadFormat),
+	);
+	assert_should_execute(
+		vec![SetAppendix(Xcm(vec![])), UnsubscribeVersion],
+		Location::parent(),
+		Err(ProcessMessageError::BadFormat),
+	);
+	// invalid XCM (unexpected instruction after)
+	assert_should_execute(
+		vec![
+			SubscribeVersion {
+				query_id: Default::default(),
+				max_response_weight: Default::default(),
+			},
+			SetTopic([0; 32]),
+		],
+		Location::parent(),
+		Err(ProcessMessageError::BadFormat),
+	);
+	assert_should_execute(
+		vec![UnsubscribeVersion, SetTopic([0; 32])],
+		Location::parent(),
+		Err(ProcessMessageError::BadFormat),
+	);
+	// invalid XCM (unexpected instruction)
+	assert_should_execute(
+		vec![SetAppendix(Xcm(vec![]))],
+		Location::parent(),
+		Err(ProcessMessageError::BadFormat),
+	);
+
+	// ok
+	assert_should_execute(
+		vec![SubscribeVersion {
+			query_id: Default::default(),
+			max_response_weight: Default::default(),
+		}],
+		Location::parent(),
+		Ok(()),
+	);
+	assert_should_execute(vec![UnsubscribeVersion], Location::parent(), Ok(()));
+}
+
+#[test]
+fn allow_hrmp_notifications_from_relay_chain_should_work() {
+	// closure for (xcm, origin) testing with `AllowHrmpNotificationsFromRelayChain`
+	let assert_should_execute = |mut xcm: Vec<Instruction<()>>, origin, expected_result| {
+		assert_eq!(
+			AllowHrmpNotificationsFromRelayChain::should_execute(
+				&origin,
+				&mut xcm,
+				Weight::from_parts(10, 10),
+				&mut props(Weight::zero()),
+			),
+			expected_result
+		);
+	};
+
+	// invalid origin
+	assert_should_execute(
+		vec![HrmpChannelAccepted { recipient: Default::default() }],
+		Location::new(1, [Parachain(1)]),
+		Err(ProcessMessageError::Unsupported),
+	);
+
+	// invalid XCM (unexpected instruction before)
+	assert_should_execute(
+		vec![SetAppendix(Xcm(vec![])), HrmpChannelAccepted { recipient: Default::default() }],
+		Location::parent(),
+		Err(ProcessMessageError::BadFormat),
+	);
+	// invalid XCM (unexpected instruction after)
+	assert_should_execute(
+		vec![HrmpChannelAccepted { recipient: Default::default() }, SetTopic([0; 32])],
+		Location::parent(),
+		Err(ProcessMessageError::BadFormat),
+	);
+	// invalid XCM (unexpected instruction)
+	assert_should_execute(
+		vec![SetAppendix(Xcm(vec![]))],
+		Location::parent(),
+		Err(ProcessMessageError::BadFormat),
+	);
+
+	// ok
+	assert_should_execute(
+		vec![HrmpChannelAccepted { recipient: Default::default() }],
+		Location::parent(),
+		Ok(()),
+	);
+	assert_should_execute(
+		vec![HrmpNewChannelOpenRequest {
+			max_capacity: Default::default(),
+			sender: Default::default(),
+			max_message_size: Default::default(),
+		}],
+		Location::parent(),
+		Ok(()),
+	);
+	assert_should_execute(
+		vec![HrmpChannelClosing {
+			recipient: Default::default(),
+			sender: Default::default(),
+			initiator: Default::default(),
+		}],
+		Location::parent(),
+		Ok(()),
+	);
 }

prdoc/pr_4156.prdoc

@@ -0,0 +1,13 @@
+title: "`AllowHrmpNotificationsFromRelayChain` barrier for HRMP notifications from the relaychain"
+
+doc:
+  - audience: Runtime Dev
+    description: |
+      A new barrier, `AllowHrmpNotificationsFromRelayChain`, has been added.
+      This barrier can be utilized to ensure that HRMP notifications originate solely from the Relay Chain.
+      If your runtime relies on these notifications,
+      you can include it in the runtime's barrier type for `xcm_executor::Config`.
+
+crates:
+- name: staging-xcm-builder
+  bump: minor