Add BondingRestriction config trait for staking pallet

bin/node/runtime/src/lib.rs

@@ -566,6 +566,7 @@ impl pallet_staking::Config for Runtime {
 	type OnStakerSlash = NominationPools;
 	type WeightInfo = pallet_staking::weights::SubstrateWeight<Runtime>;
 	type BenchmarkingConfig = StakingBenchmarkingConfig;
+	type BondingRestriction = ();
 }
 
 parameter_types! {

frame/babe/src/mock.rs

@@ -206,6 +206,7 @@ impl pallet_staking::Config for Test {
 	type OnStakerSlash = ();
 	type BenchmarkingConfig = pallet_staking::TestBenchmarkingConfig;
 	type WeightInfo = ();
+	type BondingRestriction = ();
 }
 
 impl pallet_offences::Config for Test {

frame/grandpa/src/mock.rs

@@ -210,6 +210,7 @@ impl pallet_staking::Config for Test {
 	type OnStakerSlash = ();
 	type BenchmarkingConfig = pallet_staking::TestBenchmarkingConfig;
 	type WeightInfo = ();
+	type BondingRestriction = ();
 }
 
 impl pallet_offences::Config for Test {

frame/nomination-pools/benchmarking/src/mock.rs

@@ -113,6 +113,7 @@ impl pallet_staking::Config for Runtime {
 	type OnStakerSlash = Pools;
 	type BenchmarkingConfig = pallet_staking::TestBenchmarkingConfig;
 	type WeightInfo = ();
+	type BondingRestriction = ();
 }
 
 parameter_types! {

frame/offences/benchmarking/src/mock.rs

@@ -182,6 +182,7 @@ impl pallet_staking::Config for Test {
 	type OnStakerSlash = ();
 	type BenchmarkingConfig = pallet_staking::TestBenchmarkingConfig;
 	type WeightInfo = ();
+	type BondingRestriction = ();
 }
 
 impl pallet_im_online::Config for Test {

frame/session/benchmarking/src/mock.rs

@@ -188,6 +188,7 @@ impl pallet_staking::Config for Test {
 	type OnStakerSlash = ();
 	type BenchmarkingConfig = pallet_staking::TestBenchmarkingConfig;
 	type WeightInfo = ();
+	type BondingRestriction = ();
 }
 
 impl crate::Config for Test {}

frame/staking/src/lib.rs

@@ -917,3 +917,19 @@ impl BenchmarkingConfig for TestBenchmarkingConfig {
 	type MaxValidators = frame_support::traits::ConstU32<100>;
 	type MaxNominators = frame_support::traits::ConstU32<100>;
 }
+
+/// Means for checking if there is any external restriction on bonding with a specific account
+///
+/// Allows for parts of the runtime that might implement other forms of fund locking to prevent
+/// incompatible locking on a stash account which could lead to unsafe state.
+pub trait BondingRestriction<AccountId> {
+	/// Determine if bonding is allowed with stash and controller combination
+	fn can_bond(stash: &AccountId) -> bool;
+}
+
+// No restrictions
+impl<AccountId> BondingRestriction<AccountId> for () {
+	fn can_bond(_stash: &AccountId) -> bool {
+		true
+	}
+}

frame/staking/src/mock.rs

@@ -41,6 +41,7 @@ use std::cell::RefCell;
 
 pub const INIT_TIMESTAMP: u64 = 30_000;
 pub const BLOCK_TIME: u64 = 1000;
+pub const RESTRICTED_ACCOUNT: AccountId = 55500;
 
 /// The AccountId alias in this test module.
 pub(crate) type AccountId = u64;
@@ -302,6 +303,7 @@ impl crate::pallet::pallet::Config for Test {
 	type OnStakerSlash = OnStakerSlashMock<Test>;
 	type BenchmarkingConfig = TestBenchmarkingConfig;
 	type WeightInfo = ();
+	type BondingRestriction = AccountRestricted555;
 }
 
 impl<LocalCall> frame_system::offchain::SendTransactionTypes<LocalCall> for Test
@@ -887,3 +889,12 @@ pub(crate) fn staking_events() -> Vec<crate::Event<Test>> {
 pub(crate) fn balances(who: &AccountId) -> (Balance, Balance) {
 	(Balances::free_balance(who), Balances::reserved_balance(who))
 }
+
+pub struct AccountRestricted555;
+
+// Restrict stash account
+impl BondingRestriction<AccountId> for AccountRestricted555 {
+	fn can_bond(stash: &AccountId) -> bool {
+		*stash != RESTRICTED_ACCOUNT
+	}
+}

frame/staking/src/pallet/mod.rs

@@ -40,10 +40,10 @@ mod impls;
 pub use impls::*;
 
 use crate::{
-	slashing, weights::WeightInfo, ActiveEraInfo, BalanceOf, EraPayout, EraRewardPoints, Exposure,
-	Forcing, MaxUnlockingChunks, NegativeImbalanceOf, Nominations, PositiveImbalanceOf, Releases,
-	RewardDestination, SessionInterface, StakingLedger, UnappliedSlash, UnlockChunk,
-	ValidatorPrefs,
+	slashing, weights::WeightInfo, ActiveEraInfo, BalanceOf, BondingRestriction, EraPayout,
+	EraRewardPoints, Exposure, Forcing, MaxUnlockingChunks, NegativeImbalanceOf, Nominations,
+	PositiveImbalanceOf, Releases, RewardDestination, SessionInterface, StakingLedger,
+	UnappliedSlash, UnlockChunk, ValidatorPrefs,
 };
 
 const STAKING_ID: LockIdentifier = *b"staking ";
@@ -200,6 +200,9 @@ pub mod pallet {
 
 		/// Weight information for extrinsics in this pallet.
 		type WeightInfo: WeightInfo;
+
+		/// Interface for doing bonding restriction check
+		type BondingRestriction: BondingRestriction<Self::AccountId>;
 	}
 
 	#[pallet::type_value]
@@ -705,6 +708,8 @@ pub mod pallet {
 		TooManyValidators,
 		/// Commission is too low. Must be at least `MinCommission`.
 		CommissionTooLow,
+		/// External restriction prevents bonding with given account
+		BondingRestricted,
 	}
 
 	#[pallet::hooks]
@@ -788,6 +793,10 @@ pub mod pallet {
 				return Err(Error::<T>::AlreadyPaired.into())
 			}
 
+			if !T::BondingRestriction::can_bond(&stash) {
+				return Err(Error::<T>::BondingRestricted.into())
+			}
+
 			// Reject a bond which is considered to be _dust_.
 			if value < T::Currency::minimum_balance() {
 				return Err(Error::<T>::InsufficientBond.into())

frame/staking/src/tests.rs

@@ -20,7 +20,7 @@
 use super::{ConfigOp, Event, MaxUnlockingChunks, *};
 use frame_election_provider_support::{ElectionProvider, SortedListProvider, Support};
 use frame_support::{
-	assert_noop, assert_ok, assert_storage_noop, bounded_vec,
+	assert_err, assert_noop, assert_ok, assert_storage_noop, bounded_vec,
 	dispatch::WithPostDispatchInfo,
 	pallet_prelude::*,
 	traits::{Currency, Get, ReservableCurrency},
@@ -5141,3 +5141,30 @@ fn proportional_ledger_slash_works() {
 		BTreeMap::from([(4, 0), (5, value_slashed), (6, 0), (7, 0)])
 	);
 }
+
+#[test]
+fn bond_restriction_works() {
+	ExtBuilder::default().build_and_execute(|| {
+		start_session(2);
+		assert_err!(
+			Staking::bond(
+				Origin::signed(RESTRICTED_ACCOUNT),
+				1,
+				1000,
+				RewardDestination::Controller
+			),
+			Error::<Test>::BondingRestricted
+		);
+
+		// put some money in account that we'll use.
+		let _ = Balances::make_free_balance_be(&(RESTRICTED_ACCOUNT + 1), 2000);
+
+		// Using unrestricted account should not fail
+		assert_ok!(Staking::bond(
+			Origin::signed(RESTRICTED_ACCOUNT + 1),
+			1,
+			1000,
+			RewardDestination::Controller
+		));
+	});
+}