Prevent creation of rent-paying accounts with non-empty data

runtime/Cargo.toml

@@ -19,6 +19,7 @@ bzip2 = "0.4.3"
 dashmap = { version = "4.0.2", features = ["rayon", "raw-api"] }
 crossbeam-channel = "0.5"
 dir-diff = "0.3.2"
+enum-iterator = "0.7.0"
 flate2 = "1.0.22"
 fnv = "1.0.7"
 itertools = "0.10.1"

runtime/src/account_rent_state.rs

@@ -0,0 +1,165 @@
+use {
+    crate::bank::TransactionAccountRefCell,
+    enum_iterator::IntoEnumIterator,
+    solana_sdk::{account::ReadableAccount, native_loader, rent::Rent, sysvar},
+};
+
+#[derive(Debug, PartialEq, IntoEnumIterator)]
+pub(crate) enum RentState {
+    Uninitialized, // account.lamports == 0
+    NativeOrSysvar,
+    EmptyData,  // account.data.len == 0
+    RentPaying, // 0 < account.lamports < rent-exempt-minimum for non-zero data size
+    RentExempt, // account.lamports >= rent-exempt-minimum for non-zero data size
+}
+
+impl RentState {
+    pub(crate) fn from_account(account: &TransactionAccountRefCell, rent: &Rent) -> Self {
+        let account = account.1.borrow();
+        if account.lamports() == 0 {
+            Self::Uninitialized
+        } else if native_loader::check_id(account.owner()) || sysvar::is_sysvar_id(account.owner())
+        {
+            Self::NativeOrSysvar
+        } else if account.data().is_empty() {
+            Self::EmptyData
+        } else if !rent.is_exempt(account.lamports(), account.data().len()) {
+            Self::RentPaying
+        } else {
+            Self::RentExempt
+        }
+    }
+
+    pub(crate) fn transition_allowed_from(&self, pre_rent_state: &RentState) -> bool {
+        // Only a legacy RentPaying account may end in the RentPaying state after message processing
+        !(self == &Self::RentPaying && pre_rent_state != &Self::RentPaying)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use {
+        super::*,
+        solana_sdk::{account::AccountSharedData, pubkey::Pubkey, system_program},
+        std::{cell::RefCell, rc::Rc},
+    };
+
+    #[test]
+    fn test_from_account() {
+        let account_address = Pubkey::new_unique();
+        let program_id = Pubkey::new_unique();
+        let uninitialized_account = Rc::new(RefCell::new(AccountSharedData::new(
+            0,
+            0,
+            &Pubkey::default(),
+        )));
+        let native_program_account = Rc::new(RefCell::new(AccountSharedData::new(
+            1,
+            42,
+            &native_loader::id(),
+        )));
+        let sysvar_account = Rc::new(RefCell::new(AccountSharedData::new(
+            1,
+            42,
+            &sysvar::clock::id(),
+        )));
+        let empty_data_system_account = Rc::new(RefCell::new(AccountSharedData::new(
+            10,
+            0,
+            &system_program::id(),
+        )));
+        let empty_data_other_account =
+            Rc::new(RefCell::new(AccountSharedData::new(10, 0, &program_id)));
+
+        let account_data_size = 100;
+
+        let rent = Rent::free();
+        let rent_exempt_account = Rc::new(RefCell::new(AccountSharedData::new(
+            1,
+            account_data_size,
+            &program_id,
+        ))); // if rent is free, all accounts with non-zero lamports and non-empty data are rent-exempt
+
+        assert_eq!(
+            RentState::from_account(&(account_address, uninitialized_account.clone()), &rent),
+            RentState::Uninitialized
+        );
+        assert_eq!(
+            RentState::from_account(&(account_address, native_program_account.clone()), &rent),
+            RentState::NativeOrSysvar
+        );
+        assert_eq!(
+            RentState::from_account(&(account_address, sysvar_account.clone()), &rent),
+            RentState::NativeOrSysvar
+        );
+        assert_eq!(
+            RentState::from_account(&(account_address, empty_data_system_account.clone()), &rent),
+            RentState::EmptyData
+        );
+        assert_eq!(
+            RentState::from_account(&(account_address, empty_data_other_account.clone()), &rent),
+            RentState::EmptyData
+        );
+        assert_eq!(
+            RentState::from_account(&(account_address, rent_exempt_account), &rent),
+            RentState::RentExempt
+        );
+
+        let rent = Rent::default();
+        let rent_minimum_balance = rent.minimum_balance(account_data_size);
+        let rent_paying_account = Rc::new(RefCell::new(AccountSharedData::new(
+            rent_minimum_balance.saturating_sub(1),
+            account_data_size,
+            &program_id,
+        )));
+        let rent_exempt_account = Rc::new(RefCell::new(AccountSharedData::new(
+            rent.minimum_balance(account_data_size),
+            account_data_size,
+            &program_id,
+        )));
+
+        assert_eq!(
+            RentState::from_account(&(account_address, uninitialized_account), &rent),
+            RentState::Uninitialized
+        );
+        assert_eq!(
+            RentState::from_account(&(account_address, native_program_account), &rent),
+            RentState::NativeOrSysvar
+        );
+        assert_eq!(
+            RentState::from_account(&(account_address, sysvar_account), &rent),
+            RentState::NativeOrSysvar
+        );
+        assert_eq!(
+            RentState::from_account(&(account_address, empty_data_system_account), &rent),
+            RentState::EmptyData
+        );
+        assert_eq!(
+            RentState::from_account(&(account_address, empty_data_other_account), &rent),
+            RentState::EmptyData
+        );
+        assert_eq!(
+            RentState::from_account(&(account_address, rent_paying_account), &rent),
+            RentState::RentPaying
+        );
+        assert_eq!(
+            RentState::from_account(&(account_address, rent_exempt_account), &rent),
+            RentState::RentExempt
+        );
+    }
+
+    #[test]
+    fn test_transition_allowed_from() {
+        for post_rent_state in RentState::into_enum_iter() {
+            for pre_rent_state in RentState::into_enum_iter() {
+                if post_rent_state == RentState::RentPaying
+                    && pre_rent_state != RentState::RentPaying
+                {
+                    assert!(!post_rent_state.transition_allowed_from(&pre_rent_state));
+                } else {
+                    assert!(post_rent_state.transition_allowed_from(&pre_rent_state));
+                }
+            }
+        }
+    }
+}