[pallet-revive] evm remove contract storage slot when writing all zero bytes

prdoc/pr_10309.prdoc

@@ -0,0 +1,10 @@
+title: '[pallet-revive] evm remove contract storage slot when writing all zero bytes'
+doc:
+- audience: Runtime Dev
+  description: |-
+    fixes https://github.com/paritytech/contract-issues/issues/216
+
+    When writing all zero bytes to a storage item, the item shall be deleted and deposit refunded.
+crates:
+- name: pallet-revive
+  bump: patch

substrate/frame/revive/src/tests/pvm.rs

@@ -5159,7 +5159,7 @@ fn consume_all_gas_works() {
 }
 
 #[test]
-fn existential_deposit_shall_not_charged_twice() {
+fn existential_deposit_shall_not_be_charged_twice() {
 	let (code, _) = compile_module("dummy").unwrap();
 
 	let salt = [0u8; 32];

substrate/frame/revive/src/tests/sol/host.rs

@@ -19,14 +19,14 @@
 use crate::{
 	address::AddressMapper,
 	test_utils::{builder::Contract, ALICE, BOB, BOB_ADDR},
-	tests::{builder, test_utils, ExtBuilder, RuntimeEvent, Test},
+	tests::{builder, test_utils, test_utils::get_contract, ExtBuilder, RuntimeEvent, Test},
 	Code, Config, Error, Key, System, H256, U256,
 };
 use frame_support::assert_err_ignore_postinfo;
 
 use alloy_core::sol_types::{SolCall, SolInterface};
 use frame_support::traits::{fungible::Mutate, Get};
-use pallet_revive_fixtures::{compile_module_with_type, FixtureType, Host};
+use pallet_revive_fixtures::{compile_module_with_type, Caller, FixtureType, Host};
 use pretty_assertions::assert_eq;
 use test_case::test_case;
 
@@ -606,3 +606,104 @@ fn logs_denied_for_static_call(caller_type: FixtureType, callee_type: FixtureTyp
 		assert_eq!(decoded_result.success, false);
 	});
 }
+
+#[test_case(FixtureType::Solc,   FixtureType::Solc;   "solc->solc")]
+#[test_case(FixtureType::Solc,   FixtureType::Resolc; "solc->resolc")]
+#[test_case(FixtureType::Resolc, FixtureType::Solc;   "resolc->solc")]
+#[test_case(FixtureType::Resolc, FixtureType::Resolc; "resolc->resolc")]
+fn empty_storage_item_is_zero(caller_type: FixtureType, callee_type: FixtureType) {
+	let (caller_code, _) = compile_module_with_type("Caller", caller_type).unwrap();
+	let (host_code, _) = compile_module_with_type("Host", callee_type).unwrap();
+
+	ExtBuilder::default().build().execute_with(|| {
+		<Test as Config>::Currency::set_balance(&ALICE, 100_000_000_000);
+
+		let Contract { addr: host_addr, .. } =
+			builder::bare_instantiate(Code::Upload(host_code)).build_and_unwrap_contract();
+
+		let Contract { addr: caller_addr, .. } =
+			builder::bare_instantiate(Code::Upload(caller_code)).build_and_unwrap_contract();
+
+		let index = 13u64;
+
+		// read non-existent storage item
+		let result = builder::bare_call(caller_addr)
+			.data(
+				Caller::delegateCall {
+					_callee: host_addr.0.into(),
+					_data: Host::sloadOpCall { slot: index }.abi_encode().into(),
+					_gas: u64::MAX,
+				}
+				.abi_encode(),
+			)
+			.build_and_unwrap_result();
+
+		let result = Caller::delegateCall::abi_decode_returns(&result.data).unwrap();
+		assert!(result.success, "delegateCall did not succeed");
+		let decoded = Host::sloadOpCall::abi_decode_returns(&result.output).unwrap();
+		assert_eq!(decoded, 0u64, "sloadOpCall should return zero for empty storage item");
+	})
+}
+
+#[test_case(FixtureType::Solc,   FixtureType::Solc;   "solc->solc")]
+#[test_case(FixtureType::Solc,   FixtureType::Resolc; "solc->resolc")]
+#[test_case(FixtureType::Resolc, FixtureType::Solc;   "resolc->solc")]
+#[test_case(FixtureType::Resolc, FixtureType::Resolc; "resolc->resolc")]
+fn storage_item_zero_shall_refund_deposit(caller_type: FixtureType, callee_type: FixtureType) {
+	let (caller_code, _) = compile_module_with_type("Caller", caller_type).unwrap();
+	let (host_code, _) = compile_module_with_type("Host", callee_type).unwrap();
+
+	ExtBuilder::default().build().execute_with(|| {
+		<Test as Config>::Currency::set_balance(&ALICE, 100_000_000_000);
+
+		let Contract { addr: host_addr, .. } =
+			builder::bare_instantiate(Code::Upload(host_code)).build_and_unwrap_contract();
+
+		let Contract { addr: caller_addr, .. } =
+			builder::bare_instantiate(Code::Upload(caller_code)).build_and_unwrap_contract();
+
+		let index = 13u64;
+
+		let base_deposit = get_contract(&caller_addr).total_deposit();
+
+		// write storage item
+		let result = builder::bare_call(caller_addr)
+			.data(
+				Caller::delegateCall {
+					_callee: host_addr.0.into(),
+					_data: Host::sstoreOpCall { slot: index, value: 17u64 }.abi_encode().into(),
+					_gas: u64::MAX,
+				}
+				.abi_encode(),
+			)
+			.build_and_unwrap_result();
+		let result = Caller::delegateCall::abi_decode_returns(&result.data).unwrap();
+		assert!(result.success, "delegateCall did not succeed");
+
+		// 32 for key, 32 for value, 2 for item
+		assert_eq!(get_contract(&caller_addr).total_deposit(), base_deposit + 32 + 32 + 2);
+
+		// write storage item to all zeros
+		let result = builder::bare_call(caller_addr)
+			.data(
+				Caller::delegateCall {
+					_callee: host_addr.0.into(),
+					_data: Host::sstoreOpCall { slot: index, value: 0u64 }.abi_encode().into(),
+					_gas: u64::MAX,
+				}
+				.abi_encode(),
+			)
+			.build_and_unwrap_result();
+
+		let result = Caller::delegateCall::abi_decode_returns(&result.data).unwrap();
+		assert!(result.success, "delegateCall did not succeed");
+
+		if callee_type == FixtureType::Resolc {
+			// Resolc will not refund
+			assert_eq!(get_contract(&caller_addr).total_deposit(), base_deposit + 32 + 32 + 2);
+		} else {
+			// solc will refund
+			assert_eq!(get_contract(&caller_addr).total_deposit(), base_deposit);
+		}
+	});
+}

substrate/frame/revive/src/vm/evm/instructions/host.rs

@@ -146,16 +146,16 @@ fn store_helper<'ext, E: Ext>(
 	let charged_amount = interpreter.ext.charge_or_halt(cost_before)?;
 	let key = Key::Fix(index.to_big_endian());
 	let take_old = false;
-	let Ok(write_outcome) =
-		set_function(interpreter.ext, &key, Some(value.to_big_endian().to_vec()), take_old)
+	let value_to_store = if value.is_zero() { None } else { Some(value.to_big_endian().to_vec()) };
+	let Ok(write_outcome) = set_function(interpreter.ext, &key, value_to_store.clone(), take_old)
 	else {
 		return ControlFlow::Break(Error::<E::T>::ContractTrapped.into());
 	};
 
-	interpreter
-		.ext
-		.gas_meter_mut()
-		.adjust_gas(charged_amount, adjust_cost(32, write_outcome.old_len()));
+	interpreter.ext.gas_meter_mut().adjust_gas(
+		charged_amount,
+		adjust_cost(if value_to_store.is_some() { 32 } else { 0 }, write_outcome.old_len()),
+	);
 
 	ControlFlow::Continue(())
 }