fix(evm): reject tx whenever a decimals conversion produces non-zero remainder

Author: dessaya

packages/evm/jsonrpc/evmchain.go

@@ -309,7 +309,9 @@ func (e *EVMChain) Balance(address common.Address, blockNumberOrHash *rpc.BlockN
 		isc.NewEthereumAddressAgentID(*e.backend.ISCChainID(), address),
 		*e.backend.ISCChainID(),
 	)
-	return util.BaseTokensDecimalsToEthereumDecimals(baseTokens, parameters.L1().BaseToken.Decimals), nil
+	ether, _ := util.BaseTokensDecimalsToEthereumDecimals(baseTokens, parameters.L1().BaseToken.Decimals)
+	// discard remainder
+	return ether, nil
 }
 
 func (e *EVMChain) Code(address common.Address, blockNumberOrHash *rpc.BlockNumberOrHash) ([]byte, error) {

packages/util/decimals_hack.go

@@ -1,30 +1,55 @@
 package util
 
-import "math/big"
+import (
+	"math/big"
+)
 
 const ethereumDecimals = uint32(18)
 
-func adaptDecimals(value *big.Int, fromDecimals, toDecimals uint32) *big.Int {
-	v := new(big.Int).Set(value) // clone value
+func adaptDecimals(value *big.Int, fromDecimals, toDecimals uint32) (result *big.Int, remainder *big.Int) {
+	result = new(big.Int)
+	remainder = new(big.Int)
 	exp := big.NewInt(10)
 	if toDecimals > fromDecimals {
 		exp.Exp(exp, big.NewInt(int64(toDecimals-fromDecimals)), nil)
-		return v.Mul(v, exp)
+		result.Mul(value, exp)
+	} else {
+		exp.Exp(exp, big.NewInt(int64(fromDecimals-toDecimals)), nil)
+		result.DivMod(value, exp, remainder)
 	}
-	exp.Exp(exp, big.NewInt(int64(fromDecimals-toDecimals)), nil)
-	return v.Div(v, exp)
+	return
 }
 
 // wei => base tokens
-func EthereumDecimalsToBaseTokenDecimals(value *big.Int, baseTokenDecimals uint32) uint64 {
-	v := adaptDecimals(value, ethereumDecimals, baseTokenDecimals)
-	if !v.IsUint64() {
+func EthereumDecimalsToBaseTokenDecimals(value *big.Int, baseTokenDecimals uint32) (result uint64, remainder *big.Int) {
+	r, m := adaptDecimals(value, ethereumDecimals, baseTokenDecimals)
+	if !r.IsUint64() {
 		panic("cannot convert ether value to base tokens: too large")
 	}
-	return v.Uint64()
+	return r.Uint64(), m
+}
+
+func MustEthereumDecimalsToBaseTokenDecimalsExact(value *big.Int, baseTokenDecimals uint32) (result uint64) {
+	r, m := EthereumDecimalsToBaseTokenDecimals(value, baseTokenDecimals)
+	if m.Sign() != 0 {
+		panic("cannot convert ether value to base tokens: non-exact conversion")
+	}
+	return r
 }
 
 // base tokens => wei
-func BaseTokensDecimalsToEthereumDecimals(value uint64, baseTokenDecimals uint32) *big.Int {
-	return adaptDecimals(new(big.Int).SetUint64(value), baseTokenDecimals, ethereumDecimals)
+func BaseTokensDecimalsToEthereumDecimals(value uint64, baseTokenDecimals uint32) (result *big.Int, remainder uint64) {
+	r, m := adaptDecimals(new(big.Int).SetUint64(value), baseTokenDecimals, ethereumDecimals)
+	if !m.IsUint64() {
+		panic("cannot convert ether value to base tokens: too large")
+	}
+	return r, m.Uint64()
+}
+
+func MustBaseTokensDecimalsToEthereumDecimalsExact(value uint64, baseTokenDecimals uint32) (result *big.Int) {
+	r, m := BaseTokensDecimalsToEthereumDecimals(value, baseTokenDecimals)
+	if m != 0 {
+		panic("cannot convert base tokens value to ether: non-exact conversion")
+	}
+	return r
 }

packages/util/decimals_hack_test.go

@@ -10,39 +10,42 @@ import (
 func TestBaseTokensDecimalsToEthereumDecimals(t *testing.T) {
 	value := uint64(12345678)
 	tests := []struct {
-		decimals uint32
-		expected string
+		decimals          uint32
+		expected          uint64
+		expectedRemainder uint64
 	}{
 		{
 			decimals: 6,
-			expected: "12345678000000000000",
+			expected: 12345678000000000000,
 		},
 		{
 			decimals: 18,
-			expected: "12345678",
+			expected: 12345678,
 		},
 		{
-			decimals: 20,
-			expected: "123456",
+			decimals:          20,
+			expected:          123456,
+			expectedRemainder: 78,
 		},
 	}
 	for _, test := range tests {
-		require.EqualValues(t,
-			test.expected,
-			BaseTokensDecimalsToEthereumDecimals(value, test.decimals).String(),
-		)
+		wei, rem := BaseTokensDecimalsToEthereumDecimals(value, test.decimals)
+		require.EqualValues(t, test.expected, wei.Uint64())
+		require.EqualValues(t, test.expectedRemainder, rem)
 	}
 }
 
 func TestEthereumDecimalsToBaseTokenDecimals(t *testing.T) {
 	value := uint64(123456789123456789)
 	tests := []struct {
-		decimals uint32
-		expected uint64
+		decimals          uint32
+		expected          uint64
+		expectedRemainder uint64
 	}{
 		{
-			decimals: 6,
-			expected: 123456, // extra decimal cases will be ignored
+			decimals:          6,
+			expected:          123456,
+			expectedRemainder: 789123456789,
 		},
 		{
 			decimals: 18,
@@ -54,9 +57,8 @@ func TestEthereumDecimalsToBaseTokenDecimals(t *testing.T) {
 		},
 	}
 	for _, test := range tests {
-		require.EqualValues(t,
-			test.expected,
-			EthereumDecimalsToBaseTokenDecimals(new(big.Int).SetUint64(value), test.decimals),
-		)
+		bt, rem := EthereumDecimalsToBaseTokenDecimals(new(big.Int).SetUint64(value), test.decimals)
+		require.EqualValues(t, test.expected, bt)
+		require.EqualValues(t, test.expectedRemainder, rem.Uint64())
 	}
 }

packages/vm/core/evm/emulator/statedb.go

@@ -17,6 +17,7 @@ import (
 	"github.com/iotaledger/wasp/packages/kv"
 	"github.com/iotaledger/wasp/packages/kv/codec"
 	"github.com/iotaledger/wasp/packages/util"
+	"github.com/iotaledger/wasp/packages/vm/core/errors/coreerrors"
 )
 
 const (
@@ -74,14 +75,20 @@ func (s *StateDB) CreateAccount(addr common.Address) {
 	CreateAccount(s.kv, addr)
 }
 
+var ErrNonZeroWeiRemainder = coreerrors.Register("cannot convert %d to base tokens decimals: non-zero remainder (%d)")
+
 func (s *StateDB) SubBalance(addr common.Address, amount *big.Int) {
 	if amount.Sign() == 0 {
 		return
 	}
 	if amount.Sign() == -1 {
 		panic("unexpected negative amount")
 	}
-	s.ctx.SubBaseTokensBalance(addr, util.EthereumDecimalsToBaseTokenDecimals(amount, s.ctx.BaseTokensDecimals()))
+	baseTokens, remainder := util.EthereumDecimalsToBaseTokenDecimals(amount, s.ctx.BaseTokensDecimals())
+	if remainder.Sign() != 0 {
+		panic(ErrNonZeroWeiRemainder.Create(amount.Uint64(), remainder.Uint64()))
+	}
+	s.ctx.SubBaseTokensBalance(addr, baseTokens)
 }
 
 func (s *StateDB) AddBalance(addr common.Address, amount *big.Int) {
@@ -91,11 +98,18 @@ func (s *StateDB) AddBalance(addr common.Address, amount *big.Int) {
 	if amount.Sign() == -1 {
 		panic("unexpected negative amount")
 	}
-	s.ctx.AddBaseTokensBalance(addr, util.EthereumDecimalsToBaseTokenDecimals(amount, s.ctx.BaseTokensDecimals()))
+	baseTokens, remainder := util.EthereumDecimalsToBaseTokenDecimals(amount, s.ctx.BaseTokensDecimals())
+	if remainder.Sign() != 0 {
+		panic(ErrNonZeroWeiRemainder.Create(amount.Uint64(), remainder.Uint64()))
+	}
+	s.ctx.AddBaseTokensBalance(addr, baseTokens)
 }
 
 func (s *StateDB) GetBalance(addr common.Address) *big.Int {
-	return util.BaseTokensDecimalsToEthereumDecimals(s.ctx.GetBaseTokensBalance(addr), s.ctx.BaseTokensDecimals())
+	baseTokens := s.ctx.GetBaseTokensBalance(addr)
+	wei, _ := util.BaseTokensDecimalsToEthereumDecimals(baseTokens, s.ctx.BaseTokensDecimals())
+	// discard remainder
+	return wei
 }
 
 func GetNonce(s kv.KVStoreReader, addr common.Address) uint64 {

packages/vm/core/evm/evmimpl/impl.go

@@ -449,15 +449,16 @@ func newL1Deposit(ctx isc.Sandbox) dict.Dict {
 	ctx.RequireNoError(err, "unable to parse assets from params")
 
 	// create a fake tx so that the deposit is visible by the EVM
-	value := util.BaseTokensDecimalsToEthereumDecimals(assets.BaseTokens, newEmulatorContext(ctx).BaseTokensDecimals())
+	// discard remainder in decimals conversion
+	wei, _ := util.BaseTokensDecimalsToEthereumDecimals(assets.BaseTokens, newEmulatorContext(ctx).BaseTokensDecimals())
 	nonce := uint64(0)
 	// encode the txdata as <AgentID sender>+<Assets>
 	txData := []byte{}
 	txData = append(txData, agentIDBytes...)
 	txData = append(txData, assets.Bytes()...)
 	chainInfo := ctx.ChainInfo()
 	gasPrice := chainInfo.GasFeePolicy.GasPriceWei(parameters.L1().BaseToken.Decimals)
-	tx := types.NewTransaction(nonce, addr, value, 0, gasPrice, txData)
+	tx := types.NewTransaction(nonce, addr, wei, 0, gasPrice, txData)
 
 	// create a fake receipt
 	receipt := &types.Receipt{

packages/vm/core/evm/evmtest/evm_test.go

@@ -1539,22 +1539,12 @@ func TestEVMTransferBaseTokens(t *testing.T) {
 
 	// issue a tx with non-0 amount (try to send ETH/basetoken)
 	// try sending 1 million base tokens (expressed in ethereum decimals)
-	value := util.BaseTokensDecimalsToEthereumDecimals(
+	value := util.MustBaseTokensDecimalsToEthereumDecimalsExact(
 		1*isc.Million,
 		testparameters.GetL1ParamsForTesting().BaseToken.Decimals,
 	)
 	sendTx(value)
 	env.Chain.AssertL2BaseTokens(someAgentID, 1*isc.Million)
-
-	// by default iota/shimmer base token has 6 decimal cases, so anything past the 6th decimal case should be ignored
-	valueWithExtraDecimals := big.NewInt(1_000_000_999_999_999_999) // all these 9's will be ignored and only 1 million tokens should be transferred
-	sendTx(valueWithExtraDecimals)
-	env.Chain.AssertL2BaseTokens(someAgentID, 2*isc.Million)
-
-	// issue a tx with a too low amount
-	lowValue := big.NewInt(999_999_999_999) // all these 9's will be ignored and nothing should be transferred
-	sendTx(lowValue)
-	env.Chain.AssertL2BaseTokens(someAgentID, 2*isc.Million)
 }
 
 func TestSolidityTransferBaseTokens(t *testing.T) {
@@ -1566,7 +1556,7 @@ func TestSolidityTransferBaseTokens(t *testing.T) {
 	iscTest := env.deployISCTestContract(ethKey)
 
 	// try sending funds to `someEthereumAddr` by sending a "value tx" to the isc test contract
-	oneMillionInEthDecimals := util.BaseTokensDecimalsToEthereumDecimals(
+	oneMillionInEthDecimals := util.MustBaseTokensDecimalsToEthereumDecimalsExact(
 		1*isc.Million,
 		testparameters.GetL1ParamsForTesting().BaseToken.Decimals,
 	)
@@ -1579,7 +1569,7 @@ func TestSolidityTransferBaseTokens(t *testing.T) {
 	env.Chain.AssertL2BaseTokens(someEthereumAgentID, 1*isc.Million)
 
 	// attempt to send more than the contract will have available
-	twoMillionInEthDecimals := util.BaseTokensDecimalsToEthereumDecimals(
+	twoMillionInEthDecimals := util.MustBaseTokensDecimalsToEthereumDecimalsExact(
 		2*isc.Million,
 		testparameters.GetL1ParamsForTesting().BaseToken.Decimals,
 	)
@@ -1591,26 +1581,6 @@ func TestSolidityTransferBaseTokens(t *testing.T) {
 	require.Error(t, err)
 	env.Chain.AssertL2BaseTokens(someEthereumAgentID, 1*isc.Million)
 
-	{
-		// try sending a value to too high precision (anything over the 6 decimals will be ignored)
-		_, err = iscTest.CallFn([]ethCallOptions{{
-			sender: ethKey,
-			value:  oneMillionInEthDecimals,
-			// wei is expressed with 18 decimal precision, iota/smr is 6, so anything in the 12 last decimal cases will be ignored
-		}}, "sendTo", someEthereumAddr, big.NewInt(1_000_000_999_999_999_999))
-		require.Error(t, err)
-		env.Chain.AssertL2BaseTokens(someEthereumAgentID, 1*isc.Million)
-		// this will fail if the (ignored) decimals are above the contract balance,
-		// but if we provide enough funds, the call should succeed and the extra decimals should be correctly ignored
-		_, err = iscTest.CallFn([]ethCallOptions{{
-			sender: ethKey,
-			value:  twoMillionInEthDecimals,
-			// wei is expressed with 18 decimal precision, iota/smr is 6, so anything in the 12 last decimal cases will be ignored
-		}}, "sendTo", someEthereumAddr, big.NewInt(1_000_000_999_999_999_999))
-		require.NoError(t, err)
-		env.Chain.AssertL2BaseTokens(someEthereumAgentID, 2*isc.Million)
-	}
-
 	// fund the contract via a L1 wallet ISC transfer, then call `sendTo` to use those funds
 	l1Wallet, _ := env.Chain.Env.NewKeyPairWithFunds()
 	env.Chain.TransferAllowanceTo(
@@ -1619,7 +1589,7 @@ func TestSolidityTransferBaseTokens(t *testing.T) {
 		l1Wallet,
 	)
 
-	tenMillionInEthDecimals := util.BaseTokensDecimalsToEthereumDecimals(
+	tenMillionInEthDecimals := util.MustBaseTokensDecimalsToEthereumDecimalsExact(
 		10*isc.Million,
 		testparameters.GetL1ParamsForTesting().BaseToken.Decimals,
 	)
@@ -1628,7 +1598,7 @@ func TestSolidityTransferBaseTokens(t *testing.T) {
 		sender: ethKey,
 	}}, "sendTo", someEthereumAddr, tenMillionInEthDecimals)
 	require.NoError(t, err)
-	env.Chain.AssertL2BaseTokens(someEthereumAgentID, 12*isc.Million)
+	env.Chain.AssertL2BaseTokens(someEthereumAgentID, 11*isc.Million)
 
 	// send more than the balance
 	_, err = iscTest.CallFn([]ethCallOptions{{
@@ -1637,7 +1607,7 @@ func TestSolidityTransferBaseTokens(t *testing.T) {
 		gasLimit: 100_000, // provide a gas limit value as the estimation will fail
 	}}, "sendTo", someEthereumAddr, big.NewInt(0))
 	require.Error(t, err)
-	env.Chain.AssertL2BaseTokens(someEthereumAgentID, 12*isc.Million)
+	env.Chain.AssertL2BaseTokens(someEthereumAgentID, 11*isc.Million)
 }
 
 func TestSendEntireBalance(t *testing.T) {
@@ -1649,7 +1619,7 @@ func TestSendEntireBalance(t *testing.T) {
 	// send all initial
 	initial := env.Chain.L2BaseTokens(isc.NewEthereumAddressAgentID(env.Chain.ChainID, ethAddr))
 	// try sending funds to `someEthereumAddr` by sending a "value tx"
-	initialBalanceInEthDecimals := util.BaseTokensDecimalsToEthereumDecimals(
+	initialBalanceInEthDecimals := util.MustBaseTokensDecimalsToEthereumDecimalsExact(
 		initial,
 		testparameters.GetL1ParamsForTesting().BaseToken.Decimals,
 	)
@@ -1669,7 +1639,7 @@ func TestSendEntireBalance(t *testing.T) {
 	// now try sending all balance, minus the funds needed for gas
 	currentBalance := env.Chain.L2BaseTokens(isc.NewEthereumAddressAgentID(env.Chain.ChainID, ethAddr))
 
-	currentBalanceInEthDecimals := util.BaseTokensDecimalsToEthereumDecimals(
+	currentBalanceInEthDecimals := util.MustBaseTokensDecimalsToEthereumDecimalsExact(
 		currentBalance,
 		testparameters.GetL1ParamsForTesting().BaseToken.Decimals,
 	)
@@ -1687,7 +1657,7 @@ func TestSendEntireBalance(t *testing.T) {
 
 	gasLimit := feePolicy.GasBudgetFromTokens(tokensForGasBudget)
 
-	valueToSendInEthDecimals := util.BaseTokensDecimalsToEthereumDecimals(
+	valueToSendInEthDecimals := util.MustBaseTokensDecimalsToEthereumDecimalsExact(
 		currentBalance-tokensForGasBudget,
 		testparameters.GetL1ParamsForTesting().BaseToken.Decimals,
 	)
@@ -2082,7 +2052,7 @@ func TestL1DepositEVM(t *testing.T) {
 	require.ErrorIs(t, err, io.EOF)
 
 	require.EqualValues(t,
-		util.EthereumDecimalsToBaseTokenDecimals(bal, parameters.L1().BaseToken.Decimals),
+		util.MustEthereumDecimalsToBaseTokenDecimalsExact(bal, parameters.L1().BaseToken.Decimals),
 		assets.BaseTokens)
 
 	evmRec := env.Chain.EVM().TransactionReceipt(tx.Hash())
@@ -2093,3 +2063,28 @@ func TestL1DepositEVM(t *testing.T) {
 	expectedGas := gas.ISCGasBudgetToEVM(iscRec.GasBurned, &feePolicy.EVMGasRatio)
 	require.EqualValues(t, expectedGas, evmRec.GasUsed)
 }
+
+func TestDecimalsConversion(t *testing.T) {
+	parameters.InitL1(parameters.L1ForTesting)
+	env := InitEVM(t)
+	ethKey, _ := env.Chain.NewEthereumAccountWithL2Funds()
+	iscTest := env.deployISCTestContract(ethKey)
+
+	// call any function including 999999999999 wei as value (which is just 1 wei short of 1 base token)
+	lessThanOneSMR := new(big.Int).SetUint64(999999999999)
+	valueInBaseTokens, remainder := util.EthereumDecimalsToBaseTokenDecimals(
+		lessThanOneSMR,
+		parameters.L1().BaseToken.Decimals,
+	)
+	t.Log(valueInBaseTokens)
+	require.Zero(t, valueInBaseTokens)
+	require.EqualValues(t, lessThanOneSMR.Uint64(), remainder.Uint64())
+
+	_, err := iscTest.CallFn(
+		[]ethCallOptions{{sender: ethKey, value: lessThanOneSMR, gasLimit: 100000}},
+		"sendTo",
+		iscTest.address,
+		big.NewInt(0),
+	)
+	require.ErrorContains(t, err, "non-zero remainder")
+}

packages/vm/vmimpl/runreq.go

@@ -2,6 +2,7 @@ package vmimpl
 
 import (
 	"math"
+	"os"
 	"runtime/debug"
 	"time"
 
@@ -207,7 +208,7 @@ func (reqctx *requestContext) callTheContract() (*vm.RequestResult, error) {
 			skipRequestErr = vmexceptions.IsSkipRequestException(r)
 			executionErr = recoverFromExecutionError(r)
 			reqctx.Debugf("recovered panic from contract call: %v", executionErr)
-			if reqctx.vm.task.WillProduceBlock() {
+			if os.Getenv("DEBUG") != "" || reqctx.vm.task.WillProduceBlock() {
 				reqctx.Debugf(string(debug.Stack()))
 			}
 		}()