Check enough funds on sender on TxProc &TxSel

- TxSelector
	- Add check enough funds on sender at TxSelector and don't
include the tx in the selection
- TxProcessor
	- Add checks that the balance when substracted the
amount/amount+fee never goes below 0

fix #502

synchronizer/synchronizer_test.go

@@ -408,9 +408,9 @@ func TestSyncGeneral(t *testing.T) {
 		ForceExit(1) B: 80
 		ForceTransfer(1) A-D: 100
 
-		Transfer(1) C-A: 100 (200)
-		Exit(1) C: 50 (200)
-		Exit(1) D: 30 (200)
+		Transfer(1) C-A: 100 (126)
+		Exit(1) C: 50 (100)
+		Exit(1) D: 30 (100)
 
 		> batchL1 // forge L1UserTxs{nil}, freeze defined L1UserTxs{3}
 		> batchL1 // forge L1UserTxs{3}, freeze defined L1UserTxs{nil}

txprocessor/txprocessor.go

@@ -55,6 +55,18 @@ type ProcessTxOutput struct {
 	CollectedFees      map[common.TokenID]*big.Int
 }
 
+func newErrorNotEnoughBalance(tx common.Tx) error {
+	var msg error
+	if tx.IsL1 {
+		msg = fmt.Errorf("Invalid transaction, not enough balance on sender account. TxID: %s, TxType: %s, FromIdx: %d, ToIdx: %d, Amount: %d",
+			tx.TxID, tx.Type, tx.FromIdx, tx.ToIdx, tx.Amount)
+	} else {
+		msg = fmt.Errorf("Invalid transaction, not enough balance on sender account. TxID: %s, TxType: %s, FromIdx: %d, ToIdx: %d, Amount: %d, Fee: %d",
+			tx.TxID, tx.Type, tx.FromIdx, tx.ToIdx, tx.Amount, tx.Fee)
+	}
+	return tracerr.Wrap(msg)
+}
+
 // NewTxProcessor returns a new TxProcessor with the given *StateDB & Config
 func NewTxProcessor(sdb *statedb.StateDB, config Config) *TxProcessor {
 	return &TxProcessor{
@@ -769,6 +781,9 @@ func (tp *TxProcessor) applyDeposit(tx *common.L1Tx, transfer bool) error {
 	accSender.Balance = new(big.Int).Add(accSender.Balance, tx.EffectiveDepositAmount)
 	// subtract amount to the sender
 	accSender.Balance = new(big.Int).Sub(accSender.Balance, tx.EffectiveAmount)
+	if accSender.Balance.Cmp(big.NewInt(0)) == -1 { // balance<0
+		return newErrorNotEnoughBalance(tx.Tx())
+	}
 
 	// update sender account in localStateDB
 	p, err := tp.s.UpdateAccount(tx.FromIdx, accSender)
@@ -862,6 +877,9 @@ func (tp *TxProcessor) applyTransfer(coordIdxsMap map[common.TokenID]common.Idx,
 		}
 		feeAndAmount := new(big.Int).Add(tx.Amount, fee)
 		accSender.Balance = new(big.Int).Sub(accSender.Balance, feeAndAmount)
+		if accSender.Balance.Cmp(big.NewInt(0)) == -1 { // balance<0
+			return newErrorNotEnoughBalance(tx)
+		}
 
 		if _, ok := coordIdxsMap[accSender.TokenID]; ok {
 			accCoord, err := tp.s.GetAccount(coordIdxsMap[accSender.TokenID])
@@ -882,6 +900,9 @@ func (tp *TxProcessor) applyTransfer(coordIdxsMap map[common.TokenID]common.Idx,
 		}
 	} else {
 		accSender.Balance = new(big.Int).Sub(accSender.Balance, tx.Amount)
+		if accSender.Balance.Cmp(big.NewInt(0)) == -1 { // balance<0
+			return newErrorNotEnoughBalance(tx)
+		}
 	}
 
 	// update sender account in localStateDB
@@ -962,6 +983,9 @@ func (tp *TxProcessor) applyCreateAccountDepositTransfer(tx *common.L1Tx) error
 
 	// subtract amount to the sender
 	accSender.Balance = new(big.Int).Sub(accSender.Balance, tx.EffectiveAmount)
+	if accSender.Balance.Cmp(big.NewInt(0)) == -1 { // balance<0
+		return newErrorNotEnoughBalance(tx.Tx())
+	}
 
 	// create Account of the Sender
 	p, err := tp.s.CreateAccount(common.Idx(tp.s.CurrentIdx()+1), accSender)
@@ -1057,6 +1081,9 @@ func (tp *TxProcessor) applyExit(coordIdxsMap map[common.TokenID]common.Idx,
 		}
 		feeAndAmount := new(big.Int).Add(tx.Amount, fee)
 		acc.Balance = new(big.Int).Sub(acc.Balance, feeAndAmount)
+		if acc.Balance.Cmp(big.NewInt(0)) == -1 { // balance<0
+			return nil, false, newErrorNotEnoughBalance(tx)
+		}
 
 		if _, ok := coordIdxsMap[acc.TokenID]; ok {
 			accCoord, err := tp.s.GetAccount(coordIdxsMap[acc.TokenID])
@@ -1078,6 +1105,9 @@ func (tp *TxProcessor) applyExit(coordIdxsMap map[common.TokenID]common.Idx,
 		}
 	} else {
 		acc.Balance = new(big.Int).Sub(acc.Balance, tx.Amount)
+		if acc.Balance.Cmp(big.NewInt(0)) == -1 { // balance<0
+			return nil, false, newErrorNotEnoughBalance(tx)
+		}
 	}
 
 	p, err := tp.s.UpdateAccount(tx.FromIdx, acc)
@@ -1268,3 +1298,18 @@ func (tp *TxProcessor) computeEffectiveAmounts(tx *common.L1Tx) {
 		return
 	}
 }
+
+// CheckEnoughBalance returns true if the sender of the transaction has enough
+// balance in the account to send the Amount+Fee
+func (tp *TxProcessor) CheckEnoughBalance(tx common.PoolL2Tx) bool {
+	acc, err := tp.s.GetAccount(tx.FromIdx)
+	if err != nil {
+		return false
+	}
+	fee, err := common.CalcFeeAmount(tx.Amount, tx.Fee)
+	if err != nil {
+		return false
+	}
+	feeAndAmount := new(big.Int).Add(tx.Amount, fee)
+	return acc.Balance.Cmp(feeAndAmount) != -1 // !=-1 balance<amount
+}

txselector/txselector.go

@@ -239,10 +239,15 @@ func (txsel *TxSelector) GetL1L2TxSelection(selectionConfig *SelectionConfig,
 	var validTxs []common.PoolL2Tx
 	// iterate over l2TxsRaw
 	// - check Nonces
+	// - check enough Balance for the Amount+Fee
 	// - if needed, create new L1CoordinatorTxs for unexisting ToIdx
 	// 	- keep used accAuths
 	// - put the valid txs into validTxs array
 	for i := 0; i < len(l2Txs); i++ {
+		if !tp.CheckEnoughBalance(l2Txs[i]) {
+			// not valid Amount with current Balance
+			continue
+		}
 		// check if Nonce is correct
 		nonce := noncesMap[l2Txs[i].FromIdx]
 		if l2Txs[i].Nonce == nonce {
@@ -319,9 +324,9 @@ func (txsel *TxSelector) GetL1L2TxSelection(selectionConfig *SelectionConfig,
 
 	// get CoordIdxsMap for the TokenIDs
 	coordIdxsMap := make(map[common.TokenID]common.Idx)
-	for i := 0; i < len(l2Txs); i++ {
+	for i := 0; i < len(validTxs); i++ {
 		// get TokenID from tx.Sender
-		accSender, err := tp.StateDB().GetAccount(l2Txs[i].FromIdx)
+		accSender, err := tp.StateDB().GetAccount(validTxs[i].FromIdx)
 		if err != nil {
 			return nil, nil, nil, nil, nil, tracerr.Wrap(err)
 		}
@@ -330,7 +335,7 @@ func (txsel *TxSelector) GetL1L2TxSelection(selectionConfig *SelectionConfig,
 		coordIdx, err := txsel.getCoordIdx(tokenID)
 		if err != nil {
 			// if err is db.ErrNotFound, should not happen, as all
-			// the l2Txs.TokenID should have a CoordinatorIdx
+			// the validTxs.TokenID should have a CoordinatorIdx
 			// created in the DB at this point
 			return nil, nil, nil, nil, nil, tracerr.Wrap(err)
 		}
@@ -352,8 +357,8 @@ func (txsel *TxSelector) GetL1L2TxSelection(selectionConfig *SelectionConfig,
 	maxL2Txs := int(selectionConfig.TxProcessorConfig.MaxTx) -
 		len(l1UserTxs) - len(l1CoordinatorTxs)
 
-	selectedL2Txs := l2Txs
-	if len(l2Txs) > maxL2Txs {
+	selectedL2Txs := validTxs
+	if len(validTxs) > maxL2Txs {
 		selectedL2Txs = selectedL2Txs[:maxL2Txs]
 	}
 	var finalL2Txs []common.PoolL2Tx

txselector/txselector_test.go

@@ -378,3 +378,107 @@ func TestGetL2TxSelectionMinimumFlow0(t *testing.T) {
 	err = txsel.l2db.StartForging(common.TxIDsFromPoolL2Txs(poolL2Txs), txsel.localAccountsDB.CurrentBatch())
 	require.NoError(t, err)
 }
+
+func TestPoolL2TxsWithoutEnoughBalance(t *testing.T) {
+	set := `
+		Type: Blockchain
+
+		CreateAccountDeposit(0) Coord: 0
+		CreateAccountDeposit(0) A: 100
+		CreateAccountDeposit(0) B: 100
+
+		> batchL1 // freeze L1User{1}
+		> batchL1 // forge L1User{1}
+		> block
+	`
+
+	chainID := uint16(0)
+	tc := til.NewContext(chainID, common.RollupConstMaxL1UserTx)
+	// generate test transactions, the L1CoordinatorTxs generated by Til
+	// will be ignored at this test, as will be the TxSelector who
+	// generates them when needed
+	blocks, err := tc.GenerateBlocks(set)
+	assert.NoError(t, err)
+
+	hermezContractAddr := ethCommon.HexToAddress("0xc344E203a046Da13b0B4467EB7B3629D0C99F6E6")
+	txsel := initTest(t, chainID, hermezContractAddr, tc.Users["Coord"])
+
+	// restart nonces of TilContext, as will be set by generating directly
+	// the PoolL2Txs for each specific batch with tc.GeneratePoolL2Txs
+	tc.RestartNonces()
+
+	tpc := txprocessor.Config{
+		NLevels:  16,
+		MaxFeeTx: 10,
+		MaxTx:    20,
+		MaxL1Tx:  10,
+		ChainID:  chainID,
+	}
+	selectionConfig := &SelectionConfig{
+		MaxL1UserTxs:      5,
+		TxProcessorConfig: tpc,
+	}
+	// batch1
+	l1UserTxs := []common.L1Tx{}
+	_, _, _, _, _, err = txsel.GetL1L2TxSelection(selectionConfig, l1UserTxs)
+	require.NoError(t, err)
+
+	// batch2
+	// prepare the PoolL2Txs
+	batchPoolL2 := `
+	Type: PoolL2
+	PoolTransferToEthAddr(0) A-B: 100 (126)
+	PoolExit(0) B: 100 (126)`
+	poolL2Txs, err := tc.GeneratePoolL2Txs(batchPoolL2)
+	require.NoError(t, err)
+	// add the PoolL2Txs to the l2DB
+	addL2Txs(t, txsel, poolL2Txs)
+
+	l1UserTxs = til.L1TxsToCommonL1Txs(tc.Queues[*blocks[0].Rollup.Batches[1].Batch.ForgeL1TxsNum])
+	_, _, oL1UserTxs, oL1CoordTxs, oL2Txs, err := txsel.GetL1L2TxSelection(selectionConfig, l1UserTxs)
+	require.NoError(t, err)
+	assert.Equal(t, 3, len(oL1UserTxs))
+	assert.Equal(t, 0, len(oL1CoordTxs))
+	assert.Equal(t, 0, len(oL2Txs)) // should be 0 as the 2 PoolL2Txs does not have enough funds
+	err = txsel.l2db.StartForging(common.TxIDsFromPoolL2Txs(oL2Txs), txsel.localAccountsDB.CurrentBatch())
+	require.NoError(t, err)
+
+	// as the PoolL2Txs have not been really processed, restart nonces
+	tc.RestartNonces()
+
+	// batch3
+	// NOTE: this batch will result with 1 L2Tx, as the PoolExit tx is not
+	// possible, as the PoolTransferToEthAddr is not processed yet when
+	// checking availability of PoolExit.  This, in a near-future iteration
+	// of the TxSelector will return the 2 transactions as valid and
+	// selected, as the TxSelector will handle this kind of combinations.
+	batchPoolL2 = `
+	Type: PoolL2
+	PoolTransferToEthAddr(0) A-B: 50 (126)`
+	poolL2Txs, err = tc.GeneratePoolL2Txs(batchPoolL2)
+	require.NoError(t, err)
+	addL2Txs(t, txsel, poolL2Txs)
+
+	l1UserTxs = []common.L1Tx{}
+	_, _, oL1UserTxs, oL1CoordTxs, oL2Txs, err = txsel.GetL1L2TxSelection(selectionConfig, l1UserTxs)
+	require.NoError(t, err)
+	assert.Equal(t, 0, len(oL1UserTxs))
+	assert.Equal(t, 0, len(oL1CoordTxs))
+	assert.Equal(t, 1, len(oL2Txs)) // see 'NOTE' at the beginning of 'batch3' of this test
+	assert.Equal(t, common.TxTypeTransferToEthAddr, oL2Txs[0].Type)
+	err = txsel.l2db.StartForging(common.TxIDsFromPoolL2Txs(oL2Txs), txsel.localAccountsDB.CurrentBatch())
+	require.NoError(t, err)
+
+	// batch4
+	// make the selection of another batch, which should include the
+	// initial PoolExit, which now is valid as B has enough Balance
+	l1UserTxs = []common.L1Tx{}
+	_, _, oL1UserTxs, oL1CoordTxs, oL2Txs, err = txsel.GetL1L2TxSelection(selectionConfig, l1UserTxs)
+	require.NoError(t, err)
+	assert.Equal(t, 0, len(oL1UserTxs))
+	assert.Equal(t, 0, len(oL1CoordTxs))
+	assert.Equal(t, 1, len(oL2Txs))
+	assert.Equal(t, common.TxTypeExit, oL2Txs[0].Type)
+	err = txsel.l2db.StartForging(common.TxIDsFromPoolL2Txs(oL2Txs), txsel.localAccountsDB.CurrentBatch())
+	require.NoError(t, err)
+}