Reject vote withdraws that create non-rent-exempt accounts (#21639)

* Reject vote withdraws that create non-rent-exempt accounts

* fix mocked instruction test

program-runtime/src/invoke_context.rs

@@ -192,12 +192,20 @@ impl<'a> InvokeContext<'a> {
     pub fn new_mock(
         accounts: &'a [(Pubkey, Rc<RefCell<AccountSharedData>>)],
         builtin_programs: &'a [BuiltinProgram],
+    ) -> Self {
+        Self::new_mock_with_sysvars(accounts, builtin_programs, &[])
+    }
+
+    pub fn new_mock_with_sysvars(
+        accounts: &'a [(Pubkey, Rc<RefCell<AccountSharedData>>)],
+        builtin_programs: &'a [BuiltinProgram],
+        sysvars: &'a [(Pubkey, Vec<u8>)],
     ) -> Self {
         Self::new(
             Rent::default(),
             accounts,
             builtin_programs,
-            &[],
+            sysvars,
             Some(LogCollector::new_ref()),
             ComputeBudget::default(),
             Rc::new(RefCell::new(Executors::default())),
@@ -918,11 +926,12 @@ pub fn with_mock_invoke_context<R, F: FnMut(&mut InvokeContext) -> R>(
     callback(&mut invoke_context)
 }
 
-pub fn mock_process_instruction(
+pub fn mock_process_instruction_with_sysvars(
     loader_id: &Pubkey,
     mut program_indices: Vec<usize>,
     instruction_data: &[u8],
     keyed_accounts: &[(bool, bool, Pubkey, Rc<RefCell<AccountSharedData>>)],
+    sysvars: &[(Pubkey, Vec<u8>)],
     process_instruction: ProcessInstructionWithContext,
 ) -> Result<(), InstructionError> {
     let mut preparation =
@@ -930,7 +939,8 @@ pub fn mock_process_instruction(
     let processor_account = AccountSharedData::new_ref(0, 0, &solana_sdk::native_loader::id());
     program_indices.insert(0, preparation.accounts.len());
     preparation.accounts.push((*loader_id, processor_account));
-    let mut invoke_context = InvokeContext::new_mock(&preparation.accounts, &[]);
+    let mut invoke_context =
+        InvokeContext::new_mock_with_sysvars(&preparation.accounts, &[], sysvars);
     invoke_context.push(
         &preparation.message,
         &preparation.message.instructions[0],
@@ -940,6 +950,23 @@ pub fn mock_process_instruction(
     process_instruction(1, instruction_data, &mut invoke_context)
 }
 
+pub fn mock_process_instruction(
+    loader_id: &Pubkey,
+    program_indices: Vec<usize>,
+    instruction_data: &[u8],
+    keyed_accounts: &[(bool, bool, Pubkey, Rc<RefCell<AccountSharedData>>)],
+    process_instruction: ProcessInstructionWithContext,
+) -> Result<(), InstructionError> {
+    mock_process_instruction_with_sysvars(
+        loader_id,
+        program_indices,
+        instruction_data,
+        keyed_accounts,
+        &[],
+        process_instruction,
+    )
+}
+
 #[cfg(test)]
 mod tests {
     use {

programs/vote/src/vote_instruction.rs

@@ -408,7 +408,15 @@ pub fn process_instruction(
         }
         VoteInstruction::Withdraw(lamports) => {
             let to = keyed_account_at_index(keyed_accounts, first_instruction_account + 1)?;
-            vote_state::withdraw(me, lamports, to, &signers)
+            let rent_sysvar = if invoke_context
+                .feature_set
+                .is_active(&feature_set::reject_non_rent_exempt_vote_withdraws::id())
+            {
+                Some(invoke_context.get_sysvar(&sysvar::rent::id())?)
+            } else {
+                None
+            };
+            vote_state::withdraw(me, lamports, to, &signers, rent_sysvar)
         }
         VoteInstruction::AuthorizeChecked(vote_authorize) => {
             if invoke_context
@@ -500,11 +508,15 @@ mod tests {
             .zip(accounts.into_iter())
             .map(|(meta, account)| (meta.is_signer, meta.is_writable, meta.pubkey, account))
             .collect();
-        solana_program_runtime::invoke_context::mock_process_instruction(
+
+        let rent = Rent::default();
+        let rent_sysvar = (sysvar::rent::id(), bincode::serialize(&rent).unwrap());
+        solana_program_runtime::invoke_context::mock_process_instruction_with_sysvars(
             &id(),
             Vec::new(),
             &instruction.data,
             &keyed_accounts,
+            &[rent_sysvar],
             super::process_instruction,
         )
     }

programs/vote/src/vote_state/mod.rs

@@ -890,20 +890,28 @@ pub fn withdraw<S: std::hash::BuildHasher>(
     lamports: u64,
     to_account: &KeyedAccount,
     signers: &HashSet<Pubkey, S>,
+    rent_sysvar: Option<Rent>,
 ) -> Result<(), InstructionError> {
     let vote_state: VoteState =
         State::<VoteStateVersions>::state(vote_account)?.convert_to_current();
 
     verify_authorized_signer(&vote_state.authorized_withdrawer, signers)?;
 
-    match vote_account.lamports()?.cmp(&lamports) {
+    let remaining_balance = vote_account
-        Ordering::Less => return Err(InstructionError::InsufficientFunds),
+        .lamports()?
-        Ordering::Equal => {
+        .checked_sub(lamports)
-            // Deinitialize upon zero-balance
+        .ok_or(InstructionError::InsufficientFunds)?;
-            vote_account.set_state(&VoteStateVersions::new_current(VoteState::default()))?;
+
+    if remaining_balance == 0 {
+        // Deinitialize upon zero-balance
+        vote_account.set_state(&VoteStateVersions::new_current(VoteState::default()))?;
+    } else if let Some(rent_sysvar) = rent_sysvar {
+        let min_rent_exempt_balance = rent_sysvar.minimum_balance(vote_account.data_len()?);
+        if remaining_balance < min_rent_exempt_balance {
+            return Err(InstructionError::InsufficientFunds);
         }
-        _ => (),
     }
+
     vote_account
         .try_account_ref_mut()?
         .checked_sub_lamports(lamports)?;
@@ -1107,6 +1115,8 @@ mod tests {
     }
 
     fn create_test_account() -> (Pubkey, RefCell<AccountSharedData>) {
+        let rent = Rent::default();
+        let balance = VoteState::get_rent_exempt_reserve(&rent);
         let vote_pubkey = solana_sdk::pubkey::new_rand();
         (
             vote_pubkey,
@@ -1114,7 +1124,7 @@ mod tests {
                 &vote_pubkey,
                 &solana_sdk::pubkey::new_rand(),
                 0,
-                100,
+                balance,
             )),
         )
     }
@@ -1875,46 +1885,129 @@ mod tests {
                 &RefCell::new(AccountSharedData::default()),
             ),
             &signers,
+            None,
         );
         assert_eq!(res, Err(InstructionError::MissingRequiredSignature));
 
         // insufficient funds
         let keyed_accounts = &[KeyedAccount::new(&vote_pubkey, true, &vote_account)];
+        let lamports = vote_account.borrow().lamports();
         let signers: HashSet<Pubkey> = get_signers(keyed_accounts);
         let res = withdraw(
             &keyed_accounts[0],
-            101,
+            lamports + 1,
             &KeyedAccount::new(
                 &solana_sdk::pubkey::new_rand(),
                 false,
                 &RefCell::new(AccountSharedData::default()),
             ),
             &signers,
+            None,
         );
         assert_eq!(res, Err(InstructionError::InsufficientFunds));
 
-        // all good
+        // non rent exempt withdraw, before feature activation
-        let to_account = RefCell::new(AccountSharedData::default());
+        {
-        let lamports = vote_account.borrow().lamports();
+            let (vote_pubkey, vote_account) = create_test_account();
-        let keyed_accounts = &[KeyedAccount::new(&vote_pubkey, true, &vote_account)];
+            let keyed_accounts = &[KeyedAccount::new(&vote_pubkey, true, &vote_account)];
-        let signers: HashSet<Pubkey> = get_signers(keyed_accounts);
+            let lamports = vote_account.borrow().lamports();
-        let pre_state: VoteStateVersions = vote_account.borrow().state().unwrap();
+            let rent_sysvar = Rent::default();
-        let res = withdraw(
+            let minimum_balance = rent_sysvar
-            &keyed_accounts[0],
+                .minimum_balance(vote_account.borrow().data().len())
-            lamports,
+                .max(1);
-            &KeyedAccount::new(&solana_sdk::pubkey::new_rand(), false, &to_account),
+            assert!(minimum_balance <= lamports);
-            &signers,
+            let signers: HashSet<Pubkey> = get_signers(keyed_accounts);
-        );
+            let res = withdraw(
-        assert_eq!(res, Ok(()));
+                &keyed_accounts[0],
-        assert_eq!(vote_account.borrow().lamports(), 0);
+                lamports - minimum_balance + 1,
-        assert_eq!(to_account.borrow().lamports(), lamports);
+                &KeyedAccount::new(
-        let post_state: VoteStateVersions = vote_account.borrow().state().unwrap();
+                    &solana_sdk::pubkey::new_rand(),
-        // State has been deinitialized since balance is zero
+                    false,
-        assert!(post_state.is_uninitialized());
+                    &RefCell::new(AccountSharedData::default()),
+                ),
+                &signers,
+                None,
+            );
+            assert_eq!(res, Ok(()));
+        }
 
-        // reset balance and restore state, verify that authorized_withdrawer works
+        // non rent exempt withdraw, after feature activation
-        vote_account.borrow_mut().set_lamports(lamports);
+        {
-        vote_account.borrow_mut().set_state(&pre_state).unwrap();
+            let (vote_pubkey, vote_account) = create_test_account();
+            let keyed_accounts = &[KeyedAccount::new(&vote_pubkey, true, &vote_account)];
+            let lamports = vote_account.borrow().lamports();
+            let rent_sysvar = Rent::default();
+            let minimum_balance = rent_sysvar
+                .minimum_balance(vote_account.borrow().data().len())
+                .max(1);
+            assert!(minimum_balance <= lamports);
+            let signers: HashSet<Pubkey> = get_signers(keyed_accounts);
+            let res = withdraw(
+                &keyed_accounts[0],
+                lamports - minimum_balance + 1,
+                &KeyedAccount::new(
+                    &solana_sdk::pubkey::new_rand(),
+                    false,
+                    &RefCell::new(AccountSharedData::default()),
+                ),
+                &signers,
+                Some(rent_sysvar),
+            );
+            assert_eq!(res, Err(InstructionError::InsufficientFunds));
+        }
+
+        // partial valid withdraw, after feature activation
+        {
+            let to_account = RefCell::new(AccountSharedData::default());
+            let (vote_pubkey, vote_account) = create_test_account();
+            let keyed_accounts = &[KeyedAccount::new(&vote_pubkey, true, &vote_account)];
+            let lamports = vote_account.borrow().lamports();
+            let rent_sysvar = Rent::default();
+            let minimum_balance = rent_sysvar
+                .minimum_balance(vote_account.borrow().data().len())
+                .max(1);
+            assert!(minimum_balance <= lamports);
+            let withdraw_lamports = lamports - minimum_balance;
+            let signers: HashSet<Pubkey> = get_signers(keyed_accounts);
+            let res = withdraw(
+                &keyed_accounts[0],
+                withdraw_lamports,
+                &KeyedAccount::new(&solana_sdk::pubkey::new_rand(), false, &to_account),
+                &signers,
+                Some(rent_sysvar),
+            );
+            assert_eq!(res, Ok(()));
+            assert_eq!(
+                vote_account.borrow().lamports(),
+                lamports - withdraw_lamports
+            );
+            assert_eq!(to_account.borrow().lamports(), withdraw_lamports);
+        }
+
+        // full withdraw, before/after activation
+        {
+            let rent_sysvar = Rent::default();
+            for rent_sysvar in [None, Some(rent_sysvar)] {
+                let to_account = RefCell::new(AccountSharedData::default());
+                let (vote_pubkey, vote_account) = create_test_account();
+                let lamports = vote_account.borrow().lamports();
+                let keyed_accounts = &[KeyedAccount::new(&vote_pubkey, true, &vote_account)];
+                let signers: HashSet<Pubkey> = get_signers(keyed_accounts);
+                let res = withdraw(
+                    &keyed_accounts[0],
+                    lamports,
+                    &KeyedAccount::new(&solana_sdk::pubkey::new_rand(), false, &to_account),
+                    &signers,
+                    rent_sysvar,
+                );
+                assert_eq!(res, Ok(()));
+                assert_eq!(vote_account.borrow().lamports(), 0);
+                assert_eq!(to_account.borrow().lamports(), lamports);
+                let post_state: VoteStateVersions = vote_account.borrow().state().unwrap();
+                // State has been deinitialized since balance is zero
+                assert!(post_state.is_uninitialized());
+            }
+        }
 
         // authorize authorized_withdrawer
         let authorized_withdrawer_pubkey = solana_sdk::pubkey::new_rand();
@@ -1943,6 +2036,7 @@ mod tests {
             lamports,
             withdrawer_keyed_account,
             &signers,
+            None,
         );
         assert_eq!(res, Ok(()));
         assert_eq!(vote_account.borrow().lamports(), 0);

sdk/src/feature_set.rs

@@ -267,6 +267,10 @@ pub mod fixed_memcpy_nonoverlapping_check {
     solana_sdk::declare_id!("36PRUK2Dz6HWYdG9SpjeAsF5F3KxnFCakA2BZMbtMhSb");
 }
 
+pub mod reject_non_rent_exempt_vote_withdraws {
+    solana_sdk::declare_id!("7txXZZD6Um59YoLMF7XUNimbMjsqsWhc7g2EniiTrmp1");
+}
+
 lazy_static! {
     /// Map of feature identifiers to user-visible description
     pub static ref FEATURE_NAMES: HashMap<Pubkey, &'static str> = [
@@ -328,6 +332,7 @@ lazy_static! {
         (leave_nonce_on_success::id(), "leave nonce as is on success"),
         (reject_empty_instruction_without_program::id(), "fail instructions which have native_loader as program_id directly"),
         (fixed_memcpy_nonoverlapping_check::id(), "use correct check for nonoverlapping regions in memcpy syscall"),
+        (reject_non_rent_exempt_vote_withdraws::id(), "fail vote withdraw instructions which leave the account non-rent-exempt"),
         /*************** ADD NEW FEATURES HERE ***************/
     ]
     .iter()