session/staking/westend AH and RC: allow to set/purge session keys via AH

- Allow setting or purging keys via AH -> XCM -> RC.
-  Maintain the option to set or purge keys via RC for backward compatibility.
-  We do not yet enforce or handle deposits on AH; this will be addressed once
RC extrinsics are fully deprecated.
-  Updated Westend RC to set the deposit to 0, aligning it with the current
Polkadot/Kusama RC, and modified Westend AH to support setting or purging keys.

TODO:
-  Tests
-  Benchmarking

Author: sigurpol

Cargo.lock

@@ -77,8 +77,12 @@ pallet-vesting = { workspace = true }
 pallet-whitelist = { workspace = true }
 sp-api = { workspace = true }
 sp-arithmetic = { workspace = true }
+sp-authority-discovery = { workspace = true }
 sp-block-builder = { workspace = true }
 sp-consensus-aura = { workspace = true }
+sp-consensus-babe = { workspace = true }
+sp-consensus-beefy = { workspace = true }
+sp-consensus-grandpa = { workspace = true }
 sp-core = { workspace = true }
 sp-genesis-builder = { workspace = true }
 sp-inherents = { workspace = true }
@@ -102,6 +106,7 @@ pallet-xcm = { workspace = true }
 pallet-xcm-benchmarks = { optional = true, workspace = true }
 pallet-xcm-precompiles = { workspace = true }
 polkadot-parachain-primitives = { workspace = true }
+polkadot-primitives = { workspace = true }
 polkadot-runtime-common = { workspace = true }
 westend-runtime-constants = { workspace = true }
 xcm = { workspace = true }
@@ -209,6 +214,7 @@ runtime-benchmarks = [
 	"pallet-xcm/runtime-benchmarks",
 	"parachains-common/runtime-benchmarks",
 	"polkadot-parachain-primitives/runtime-benchmarks",
+	"polkadot-primitives/runtime-benchmarks",
 	"polkadot-runtime-common/runtime-benchmarks",
 	"snowbridge-pallet-system-frontend/runtime-benchmarks",
 	"snowbridge-runtime-common/runtime-benchmarks",
@@ -369,6 +375,7 @@ std = [
 	"parachain-info/std",
 	"parachains-common/std",
 	"polkadot-parachain-primitives/std",
+	"polkadot-primitives/std",
 	"polkadot-runtime-common/std",
 	"primitive-types/std",
 	"scale-info/std",
@@ -378,8 +385,12 @@ std = [
 	"snowbridge-runtime-common/std",
 	"sp-api/std",
 	"sp-arithmetic/std",
+	"sp-authority-discovery/std",
 	"sp-block-builder/std",
 	"sp-consensus-aura/std",
+	"sp-consensus-babe/std",
+	"sp-consensus-beefy/std",
+	"sp-consensus-grandpa/std",
 	"sp-core/std",
 	"sp-genesis-builder/std",
 	"sp-inherents/std",

cumulus/parachains/runtimes/assets/asset-hub-westend/Cargo.toml

@@ -139,6 +139,20 @@ impl_opaque_keys! {
 	}
 }
 
+// Relay chain validator session keys (forwarded to RC).
+// IMPORTANT: This MUST match the SessionKeys definition in the corresponding Relay Chain runtime
+// (polkadot/runtime/westend/src/lib.rs). If the RC keys change, this must be updated too.
+impl_opaque_keys! {
+	pub struct RCSessionKeys {
+		pub grandpa: sp_consensus_grandpa::AuthorityId,
+		pub babe: sp_consensus_babe::AuthorityId,
+		pub para_validator: polkadot_primitives::ValidatorId,
+		pub para_assignment: polkadot_primitives::AssignmentId,
+		pub authority_discovery: sp_authority_discovery::AuthorityId,
+		pub beefy: sp_consensus_beefy::ecdsa_crypto::AuthorityId,
+	}
+}
+
 #[sp_version::runtime_version]
 pub const VERSION: RuntimeVersion = RuntimeVersion {
 	// Note: "westmint" is the legacy name for this chain. It has been renamed to

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

@@ -309,6 +309,7 @@ impl pallet_staking_async_rc_client::Config for Runtime {
 	type MaxValidatorSetRetries = ConstU32<64>;
 	// export validator session at end of session 4 within an era.
 	type ValidatorSetExportSession = ConstU32<4>;
+	type Keys = RCSessionKeys;
 }
 
 #[derive(Encode, Decode)]
@@ -321,9 +322,15 @@ pub enum RelayChainRuntimePallets {
 
 #[derive(Encode, Decode)]
 pub enum AhClientCalls {
-	// index of `fn validator_set` in `staking-async-ah-client`. It has only one call.
+	// index of `fn validator_set` in `staking-async-ah-client`.
 	#[codec(index = 0)]
 	ValidatorSet(rc_client::ValidatorSetReport<AccountId>),
+	// index of `fn set_keys_from_ah` in `staking-async-ah-client`.
+	#[codec(index = 3)]
+	SetKeys { stash: AccountId, keys: Vec<u8>, proof: Vec<u8> },
+	// index of `fn purge_keys_from_ah` in `staking-async-ah-client`.
+	#[codec(index = 4)]
+	PurgeKeys { stash: AccountId },
 }
 
 pub struct ValidatorSetToXcm;
@@ -347,6 +354,64 @@ impl sp_runtime::traits::Convert<rc_client::ValidatorSetReport<AccountId>, Xcm<(
 	}
 }
 
+/// Message to set session keys on the Relay Chain.
+#[derive(Encode, Decode, Clone)]
+pub struct SetKeysMessage {
+	pub stash: AccountId,
+	pub keys: Vec<u8>,
+	pub proof: Vec<u8>,
+}
+
+pub struct SetKeysToXcm;
+impl sp_runtime::traits::Convert<SetKeysMessage, Xcm<()>> for SetKeysToXcm {
+	fn convert(msg: SetKeysMessage) -> Xcm<()> {
+		Xcm(vec![
+			Instruction::UnpaidExecution {
+				weight_limit: WeightLimit::Unlimited,
+				check_origin: None,
+			},
+			Instruction::Transact {
+				origin_kind: OriginKind::Native,
+				fallback_max_weight: None,
+				call: RelayChainRuntimePallets::AhClient(AhClientCalls::SetKeys {
+					stash: msg.stash,
+					keys: msg.keys,
+					proof: msg.proof,
+				})
+				.encode()
+				.into(),
+			},
+		])
+	}
+}
+
+/// Message to purge session keys on the Relay Chain.
+#[derive(Encode, Decode, Clone)]
+pub struct PurgeKeysMessage {
+	pub stash: AccountId,
+}
+
+pub struct PurgeKeysToXcm;
+impl sp_runtime::traits::Convert<PurgeKeysMessage, Xcm<()>> for PurgeKeysToXcm {
+	fn convert(msg: PurgeKeysMessage) -> Xcm<()> {
+		Xcm(vec![
+			Instruction::UnpaidExecution {
+				weight_limit: WeightLimit::Unlimited,
+				check_origin: None,
+			},
+			Instruction::Transact {
+				origin_kind: OriginKind::Native,
+				fallback_max_weight: None,
+				call: RelayChainRuntimePallets::AhClient(AhClientCalls::PurgeKeys {
+					stash: msg.stash,
+				})
+				.encode()
+				.into(),
+			},
+		])
+	}
+}
+
 parameter_types! {
 	pub RelayLocation: Location = Location::parent();
 }
@@ -363,6 +428,24 @@ impl rc_client::SendToRelayChain for StakingXcmToRelayChain {
 			ValidatorSetToXcm,
 		>::send(report)
 	}
+
+	fn set_keys(stash: Self::AccountId, keys: Vec<u8>, proof: Vec<u8>) -> Result<(), ()> {
+		rc_client::XCMSender::<
+			xcm_config::XcmRouter,
+			RelayLocation,
+			SetKeysMessage,
+			SetKeysToXcm,
+		>::send(SetKeysMessage { stash, keys, proof })
+	}
+
+	fn purge_keys(stash: Self::AccountId) -> Result<(), ()> {
+		rc_client::XCMSender::<
+			xcm_config::XcmRouter,
+			RelayLocation,
+			PurgeKeysMessage,
+			PurgeKeysToXcm,
+		>::send(PurgeKeysMessage { stash })
+	}
 }
 
 parameter_types! {

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

@@ -509,7 +509,6 @@ impl pallet_authorship::Config for Runtime {
 parameter_types! {
 	pub const Period: BlockNumber = 10 * MINUTES;
 	pub const Offset: BlockNumber = 0;
-	pub const KeyDeposit: Balance = deposit(1, 5 * 32 + 33);
 }
 
 impl_opaque_keys! {
@@ -535,7 +534,7 @@ impl pallet_session::Config for Runtime {
 	type DisablingStrategy = pallet_session::disabling::UpToLimitWithReEnablingDisablingStrategy;
 	type WeightInfo = weights::pallet_session::WeightInfo<Runtime>;
 	type Currency = Balances;
-	type KeyDeposit = KeyDeposit;
+	type KeyDeposit = ();
 }
 
 impl pallet_session::historical::Config for Runtime {

polkadot/runtime/westend/src/lib.rs

@@ -0,0 +1,18 @@
+title: 'staking-async: allow  session keys handling on AssetHub'
+doc:
+- audience: Runtime Dev
+  description: |-
+    - Added  session keys handling on AssetHub for staking-async: validators can now call set_keys and purge_keys on AssetHub, which forwards the request to the RelayChain via XCM.
+    - Validators are still allowed to call `set_keys` and `purge_keys` via relay-chain pallet-session's related extrinsics. This option will be deprecated in the future.
+      - Until then, no key deposit is set on AssetHub yet
+crates:
+- name: asset-hub-westend-runtime
+  bump: major
+- name: westend-runtime
+  bump: major
+- name: pallet-session
+  bump: major
+- name: pallet-staking-async-ah-client
+  bump: major
+- name: pallet-staking-async-rc-client
+  bump: major

prdoc/pr_10666.prdoc

@@ -860,7 +860,10 @@ impl<T: Config> Pallet<T> {
 	///
 	/// This ensures that the reference counter in system is incremented appropriately and as such
 	/// must accept an account ID, rather than a validator ID.
-	fn do_set_keys(account: &T::AccountId, keys: T::Keys) -> DispatchResult {
+	///
+	/// This function is public to allow cross-chain session key management (e.g., from AssetHub
+	/// via `pallet-staking-async-ah-client`).
+	pub fn do_set_keys(account: &T::AccountId, keys: T::Keys) -> DispatchResult {
 		let who = T::ValidatorIdOf::convert(account.clone())
 			.ok_or(Error::<T>::NoAssociatedValidatorId)?;
 
@@ -923,7 +926,11 @@ impl<T: Config> Pallet<T> {
 		Ok(old_keys)
 	}
 
-	fn do_purge_keys(account: &T::AccountId) -> DispatchResult {
+	/// Purge session keys for an account.
+	///
+	/// This function is public to allow cross-chain session key management (e.g., from AssetHub
+	/// via `pallet-staking-async-ah-client`).
+	pub fn do_purge_keys(account: &T::AccountId) -> DispatchResult {
 		let who = T::ValidatorIdOf::convert(account.clone())
 			// `purge_keys` may not have a controller-stash pair any more. If so then we expect the
 			// stash account to be passed in directly and convert that to a `ValidatorId` using the