fix: distribution precompile 32-byte withdraw address inflates native…

precompiles/common/balance_handler.go

@@ -85,6 +85,10 @@ func (bh *BalanceHandler) AfterBalanceChange(ctx sdk.Context, stateDB *statedb.S
 				// Bypass blocked addresses
 				continue
 			}
+			if !isMirrorableEVMAddress(spenderAddr) {
+				// Non-20-byte accounts have no bijective EVM mapping; skip mirroring.
+				continue
+			}
 
 			amount, err := ParseAmount(event)
 			if err != nil {
@@ -102,6 +106,12 @@ func (bh *BalanceHandler) AfterBalanceChange(ctx sdk.Context, stateDB *statedb.S
 				// Bypass blocked addresses
 				continue
 			}
+			if !isMirrorableEVMAddress(receiverAddr) {
+				// Non-20-byte accounts have no bijective EVM mapping; skip mirroring.
+				// A 32-byte withdraw address would otherwise be truncated to its trailing
+				// 20 bytes here and minted a duplicate balance on StateDB commit.
+				continue
+			}
 
 			amount, err := ParseAmount(event)
 			if err != nil {
@@ -119,6 +129,10 @@ func (bh *BalanceHandler) AfterBalanceChange(ctx sdk.Context, stateDB *statedb.S
 				// Bypass blocked addresses
 				continue
 			}
+			if !isMirrorableEVMAddress(addr) {
+				// Non-20-byte accounts have no bijective EVM mapping; skip mirroring.
+				continue
+			}
 
 			delta, err := ParseFractionalAmount(event)
 			if err != nil {
@@ -144,3 +158,13 @@ func (bh *BalanceHandler) AfterBalanceChange(ctx sdk.Context, stateDB *statedb.S
 
 	return nil
 }
+
+// isMirrorableEVMAddress reports whether the SDK account address maps 1:1 to an
+// EVM address. Only exactly-20-byte accounts have a bijective mapping; longer
+// accounts (e.g. 32-byte module, CosmWasm contract, or bech32m accounts) would be
+// truncated by common.BytesToAddress to their trailing 20 bytes. Mirroring such a
+// balance change into the StateDB would mint or burn a duplicate balance on commit
+// and break the native bank supply invariant, so those events must be skipped.
+func isMirrorableEVMAddress(addr sdk.AccAddress) bool {
+	return len(addr) == common.AddressLength
+}

precompiles/common/balance_handler_test.go

@@ -1,6 +1,7 @@
 package common_test
 
 import (
+	"bytes"
 	"testing"
 
 	"github.com/ethereum/go-ethereum/common"
@@ -186,6 +187,45 @@ func TestAfterBalanceChange(t *testing.T) {
 	require.Equal(t, "3", stateDB.GetBalance(receiver).String())
 }
 
+// TestAfterBalanceChangeSkips32ByteAddress is a regression test for the distribution
+// precompile 32-byte withdraw address supply inflation. A 32-byte SDK account (e.g. a
+// bech32 withdraw address, module, or CosmWasm contract account) must NOT be mirrored
+// into the StateDB, because common.BytesToAddress would truncate it to its trailing 20
+// bytes and the StateDB commit would mint a duplicate balance to that EVM account,
+// inflating the native token supply.
+func TestAfterBalanceChangeSkips32ByteAddress(t *testing.T) {
+	setupBalanceHandlerTest(t)
+
+	storeKey := storetypes.NewKVStoreKey("test")
+	tKey := storetypes.NewTransientStoreKey("test_t")
+	ctx := sdktestutil.DefaultContext(storeKey, tKey)
+
+	stateDB := statedb.New(ctx, mocks.NewEVMKeeper(), statedb.NewEmptyTxConfig())
+
+	// 32-byte account; its trailing 20 bytes are what common.BytesToAddress would derive.
+	receiverAcc := sdk.AccAddress(bytes.Repeat([]byte{0xAB}, 32))
+	require.Len(t, receiverAcc, 32)
+	trailing20 := common.BytesToAddress(receiverAcc.Bytes())
+
+	bankKeeper := cmnmocks.NewBankKeeper(t)
+	precisebankModuleAccAddr := authtypes.NewModuleAddress(precisebanktypes.ModuleName)
+	bankKeeper.Mock.On("BlockedAddr", mock.AnythingOfType("types.AccAddress")).Return(func(addr sdk.AccAddress) bool {
+		return addr.Equals(precisebankModuleAccAddr)
+	})
+	bhf := cmn.NewBalanceHandlerFactory(bankKeeper)
+	bh := bhf.NewBalanceHandler()
+	bh.BeforeBalanceChange(ctx)
+
+	coins := sdk.NewCoins(sdk.NewInt64Coin(evmtypes.GetEVMCoinDenom(), 7))
+	ctx.EventManager().EmitEvent(banktypes.NewCoinReceivedEvent(receiverAcc, coins))
+
+	err := bh.AfterBalanceChange(ctx, stateDB)
+	require.NoError(t, err)
+
+	// The 32-byte receiver must not be mirrored to its trailing-20-byte EVM account.
+	require.Equal(t, "0", stateDB.GetBalance(trailing20).String())
+}
+
 func TestAfterBalanceChangeErrors(t *testing.T) {
 	setupBalanceHandlerTest(t)