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Prevent withrawing Initialized stake account to rent-exempt reserve #17366

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May 21, 2021
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Prevent withrawing Initialized stake account to rent-exempt reserve #17366

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1 change: 1 addition & 0 deletions programs/stake/src/stake_instruction.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -610,6 +610,7 @@ pub fn process_instruction(
&from_keyed_account::<StakeHistory>(keyed_account_at_index(keyed_accounts, 3)?)?,
keyed_account_at_index(keyed_accounts, 4)?,
keyed_account_at_index(keyed_accounts, 5).ok(),
invoke_context.is_feature_active(&feature_set::stake_program_v4::id()),
)
}
StakeInstruction::Deactivate => me.deactivate(
Expand Down
126 changes: 125 additions & 1 deletion programs/stake/src/stake_state.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -881,6 +881,7 @@ pub trait StakeAccount {
stake_history: &StakeHistory,
withdraw_authority: &KeyedAccount,
custodian: Option<&KeyedAccount>,
prevent_withdraw_to_zero: bool,
) -> Result<(), InstructionError>;
}

Expand Down Expand Up @@ -1219,6 +1220,7 @@ impl<'a> StakeAccount for KeyedAccount<'a> {
stake_history: &StakeHistory,
withdraw_authority: &KeyedAccount,
custodian: Option<&KeyedAccount>,
prevent_withdraw_to_zero: bool,
) -> Result<(), InstructionError> {
let mut signers = HashSet::new();
let withdraw_authority_pubkey = withdraw_authority
Expand Down Expand Up @@ -1248,8 +1250,13 @@ impl<'a> StakeAccount for KeyedAccount<'a> {
StakeState::Initialized(meta) => {
meta.authorized
.check(&signers, StakeAuthorize::Withdrawer)?;
let reserve = if prevent_withdraw_to_zero {
checked_add(meta.rent_exempt_reserve, 1)? // stake accounts must have a balance > rent_exempt_reserve
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here

} else {
meta.rent_exempt_reserve
};

(meta.lockup, meta.rent_exempt_reserve, false)
(meta.lockup, reserve, false)
}
StakeState::Uninitialized => {
if !signers.contains(&self.unsigned_key()) {
Expand Down Expand Up @@ -3090,6 +3097,7 @@ mod tests {
&StakeHistory::default(),
&to_keyed_account, // unsigned account as withdraw authority
None,
true,
),
Err(InstructionError::MissingRequiredSignature)
);
Expand All @@ -3105,6 +3113,7 @@ mod tests {
&StakeHistory::default(),
&stake_keyed_account,
None,
true,
),
Ok(())
);
Expand Down Expand Up @@ -3140,6 +3149,7 @@ mod tests {
&StakeHistory::default(),
&stake_keyed_account,
None,
true,
),
Err(InstructionError::InsufficientFunds)
);
Expand Down Expand Up @@ -3181,6 +3191,7 @@ mod tests {
&StakeHistory::default(),
&stake_keyed_account,
None,
true,
),
Ok(())
);
Expand All @@ -3198,6 +3209,7 @@ mod tests {
&StakeHistory::default(),
&stake_keyed_account,
None,
true,
),
Err(InstructionError::InsufficientFunds)
);
Expand All @@ -3217,6 +3229,7 @@ mod tests {
&StakeHistory::default(),
&stake_keyed_account,
None,
true,
),
Err(InstructionError::InsufficientFunds)
);
Expand All @@ -3231,6 +3244,7 @@ mod tests {
&StakeHistory::default(),
&stake_keyed_account,
None,
true,
),
Ok(())
);
Expand Down Expand Up @@ -3287,6 +3301,7 @@ mod tests {
&StakeHistory::default(),
&authority_keyed_account,
None,
true,
),
Err(InstructionError::InsufficientFunds),
);
Expand Down Expand Up @@ -3358,6 +3373,7 @@ mod tests {
&stake_history,
&stake_keyed_account,
None,
true,
),
Err(InstructionError::InsufficientFunds)
);
Expand Down Expand Up @@ -3387,6 +3403,7 @@ mod tests {
&StakeHistory::default(),
&stake_keyed_account,
None,
true,
),
Err(InstructionError::InvalidAccountData)
);
Expand Down Expand Up @@ -3429,6 +3446,7 @@ mod tests {
&StakeHistory::default(),
&stake_keyed_account,
None,
true,
),
Err(StakeError::LockupInForce.into())
);
Expand All @@ -3444,6 +3462,7 @@ mod tests {
&StakeHistory::default(),
&stake_keyed_account,
Some(&custodian_keyed_account),
true,
),
Ok(())
);
Expand All @@ -3465,6 +3484,7 @@ mod tests {
&StakeHistory::default(),
&stake_keyed_account,
None,
true,
),
Ok(())
);
Expand Down Expand Up @@ -3508,6 +3528,7 @@ mod tests {
&StakeHistory::default(),
&stake_keyed_account,
None,
true,
),
Err(StakeError::LockupInForce.into())
);
Expand All @@ -3522,13 +3543,113 @@ mod tests {
&StakeHistory::default(),
&stake_keyed_account,
Some(&custodian_keyed_account),
true,
),
Ok(())
);
assert_eq!(stake_keyed_account.state(), Ok(StakeState::Uninitialized));
}
}

#[test]
fn test_withdraw_rent_exempt() {
let stake_pubkey = solana_sdk::pubkey::new_rand();
let clock = Clock::default();
let rent = Rent::default();
let rent_exempt_reserve = rent.minimum_balance(std::mem::size_of::<StakeState>());
let stake = 42;
let stake_account = AccountSharedData::new_ref_data_with_space(
stake + rent_exempt_reserve,
&StakeState::Initialized(Meta {
rent_exempt_reserve,
..Meta::auto(&stake_pubkey)
}),
std::mem::size_of::<StakeState>(),
&id(),
)
.expect("stake_account");

let to = solana_sdk::pubkey::new_rand();
let to_account = AccountSharedData::new_ref(1, 0, &system_program::id());
let to_keyed_account = KeyedAccount::new(&to, false, &to_account);

// Withdrawing account down to only rent-exempt reserve should succeed before feature, and
// fail after
let stake_keyed_account = KeyedAccount::new(&stake_pubkey, true, &stake_account);
assert_eq!(
stake_keyed_account.withdraw(
stake,
&to_keyed_account,
&clock,
&StakeHistory::default(),
&stake_keyed_account,
None,
false,
),
Ok(())
);
stake_account
.borrow_mut()
.checked_add_lamports(stake)
.unwrap(); // top up account
let stake_keyed_account = KeyedAccount::new(&stake_pubkey, true, &stake_account);
assert_eq!(
stake_keyed_account.withdraw(
stake,
&to_keyed_account,
&clock,
&StakeHistory::default(),
&stake_keyed_account,
None,
true,
),
Err(InstructionError::InsufficientFunds)
);

// Withdrawal that would leave less than rent-exempt reserve should fail
let stake_keyed_account = KeyedAccount::new(&stake_pubkey, true, &stake_account);
assert_eq!(
stake_keyed_account.withdraw(
stake + 1,
&to_keyed_account,
&clock,
&StakeHistory::default(),
&stake_keyed_account,
None,
false,
),
Err(InstructionError::InsufficientFunds)
);
let stake_keyed_account = KeyedAccount::new(&stake_pubkey, true, &stake_account);
assert_eq!(
stake_keyed_account.withdraw(
stake + 1,
&to_keyed_account,
&clock,
&StakeHistory::default(),
&stake_keyed_account,
None,
true,
),
Err(InstructionError::InsufficientFunds)
);

// Withdrawal of complete account should succeed
let stake_keyed_account = KeyedAccount::new(&stake_pubkey, true, &stake_account);
assert_eq!(
stake_keyed_account.withdraw(
stake + rent_exempt_reserve,
&to_keyed_account,
&clock,
&StakeHistory::default(),
&stake_keyed_account,
None,
true,
),
Ok(())
);
}

#[test]
fn test_stake_state_redeem_rewards() {
let mut vote_state = VoteState::default();
Expand Down Expand Up @@ -3965,6 +4086,7 @@ mod tests {
&StakeHistory::default(),
&stake_keyed_account, // old signer
None,
true,
),
Err(InstructionError::MissingRequiredSignature)
);
Expand All @@ -3981,6 +4103,7 @@ mod tests {
&StakeHistory::default(),
&stake_keyed_account2,
None,
true,
),
Ok(())
);
Expand Down Expand Up @@ -5934,6 +6057,7 @@ mod tests {
&stake_history,
&stake_keyed_account,
None,
true,
)
.unwrap();
let expected_balance = rent_exempt_reserve + initial_lamports - withdraw_lamports;
Expand Down