Candidate whitelist

Author: olegnn

Cargo.lock

@@ -1,6 +1,6 @@
 [package]
 name = "pallet-staking"
-version = "4.0.0-dev"
+version = "4.1.0-dev"
 authors = ["Dock.io", "Parity Technologies <admin@parity.io>"]
 edition = "2021"
 license = "Apache-2.0"
@@ -39,6 +39,7 @@ rand_chacha = { version = "0.2", default-features = false, optional = true }
 [dev-dependencies]
 sp-tracing = { version = "5.0.0", git = "https://github.com/paritytech/substrate.git", branch = "polkadot-v0.9.29" }
 sp-core = { version = "6.0.0", git = "https://github.com/paritytech/substrate.git", branch = "polkadot-v0.9.29" }
+sp-state-machine = { git = "https://github.com/paritytech/substrate.git", branch = "polkadot-v0.9.29" }
 sp-npos-elections = { version = "4.0.0-dev", git = "https://github.com/paritytech/substrate.git", branch = "polkadot-v0.9.29" }
 pallet-balances = { version = "4.0.0-dev", git = "https://github.com/paritytech/substrate.git", branch = "polkadot-v0.9.29" }
 pallet-timestamp = { version = "4.0.0-dev", git = "https://github.com/paritytech/substrate.git", branch = "polkadot-v0.9.29" }

substrate/frame/staking/Cargo.toml

@@ -422,6 +422,10 @@ impl ExtBuilder {
             .build_storage::<Test>()
             .unwrap();
 
+        sp_state_machine::BasicExternalities::execute_with_storage(&mut storage, || {
+            Staking::set_whitelist(Origin::root(), (0..100).collect()).unwrap();
+        });
+
         let _ = pallet_balances::GenesisConfig::<Test> {
             balances: vec![
                 (1, 10 * self.balance_factor),

substrate/frame/staking/src/mock.rs

@@ -442,6 +442,14 @@ impl<T: Config> Pallet<T> {
             Self::clear_era_information(old_era);
         }
 
+        let whitelist = Self::candidate_whitelist();
+        let to_remove: Vec<_> = Validators::<T>::iter_keys()
+            .filter(|validator| !whitelist.contains(&validator))
+            .collect();
+        for validator in to_remove {
+            Self::do_remove_validator(&validator);
+        }
+
         // Set staking information for the new era.
         Self::store_stakers_info(exposures, new_planned_era)
     }

substrate/frame/staking/src/pallet/impls.rs

@@ -50,6 +50,8 @@ const STAKING_ID: LockIdentifier = *b"staking ";
 
 #[frame_support::pallet]
 pub mod pallet {
+    use std::collections::BTreeSet;
+
     use frame_election_provider_support::ElectionDataProvider;
 
     use crate::BenchmarkingConfig;
@@ -516,6 +518,10 @@ pub mod pallet {
     #[pallet::storage]
     pub(crate) type ChillThreshold<T: Config> = StorageValue<_, Percent, OptionQuery>;
 
+    #[pallet::storage]
+    #[pallet::getter(fn candidate_whitelist)]
+    pub type CandidateWhitelist<T: Config> = StorageValue<_, BTreeSet<T::AccountId>, ValueQuery>;
+
     #[pallet::genesis_config]
     pub struct GenesisConfig<T: Config> {
         pub history_depth: u32,
@@ -716,6 +722,8 @@ pub mod pallet {
         CommissionTooLow,
         /// Can't kill the stash while it has some unclaimed era rewards. It will be possible after claiming.
         CantKillStashWithUnclaimedRewards,
+        /// Can only submit as candidates accounts that were whitelisted.
+        NotInAWhitelist,
     }
 
     #[pallet::hooks]
@@ -1048,6 +1056,11 @@ pub mod pallet {
                 Error::<T>::CommissionTooLow
             );
 
+            ensure!(
+                Self::candidate_whitelist().contains(&stash),
+                Error::<T>::NotInAWhitelist
+            );
+
             // Only check limits if they are not already a validator.
             if !Validators::<T>::contains_key(stash) {
                 // If this error is reached, we need to adjust the `MinValidatorBond` and start
@@ -1753,6 +1766,18 @@ pub mod pallet {
             })?;
             Ok(())
         }
+
+        #[pallet::weight(T::DbWeight::get().writes(1))]
+        pub fn set_whitelist(
+            origin: OriginFor<T>,
+            whitelist: BTreeSet<T::AccountId>,
+        ) -> DispatchResult {
+            ensure_root(origin)?;
+
+            CandidateWhitelist::<T>::put(whitelist);
+
+            Ok(())
+        }
     }
 }
 

substrate/frame/staking/src/pallet/mod.rs

@@ -88,6 +88,10 @@ pub fn create_stash_controller<T: Config>(
         amount,
         destination,
     )?;
+    let mut whitelist = Staking::<T>::candidate_whitelist();
+    whitelist.insert(stash.clone());
+    Staking::<T>::set_whitelist(RawOrigin::Root.into(), whitelist).unwrap();
+
     Ok((stash, controller))
 }
 

substrate/frame/staking/src/testing_utils.rs

@@ -17,6 +17,8 @@
 
 //! Tests for the module.
 
+use core::iter::empty;
+
 use super::{ConfigOp, Event, MaxUnlockingChunks, *};
 use frame_election_provider_support::{ElectionProvider, SortedListProvider, Support};
 use frame_support::{
@@ -424,6 +426,23 @@ fn change_controller_works() {
     })
 }
 
+#[test]
+fn whitelist_works() {
+    ExtBuilder::default().build_and_execute(|| {
+        super::Pallet::<Test>::set_whitelist(Origin::root(), empty().collect()).unwrap();
+        // 10 and 11 are bonded as stash controller.
+        assert_eq!(Staking::bonded(&11), Some(10));
+
+        // 10 can control 11 who is initially a validator.
+        assert_ok!(Staking::chill(Origin::signed(10)));
+
+        assert_noop!(
+            Staking::validate(Origin::signed(10), ValidatorPrefs::default()),
+            Error::<Test>::NotInAWhitelist
+        );
+    })
+}
+
 #[test]
 fn rewards_should_work() {
     ExtBuilder::default()