From 4d475ce9fb41307608dc9321942cc3187fd0ee74 Mon Sep 17 00:00:00 2001
From: tanyuan <1067598718@qq.com>
Date: Wed, 20 Jun 2018 15:25:58 +0800
Subject: [PATCH] add safe math calculate (#373)

---
 common/safeMath.go                   | 40 ++++++++++++++++++++++++++++
 core/store/ledgerstore/tx_handler.go | 26 ++++++++++++------
 2 files changed, 58 insertions(+), 8 deletions(-)
 create mode 100644 common/safeMath.go

diff --git a/common/safeMath.go b/common/safeMath.go
new file mode 100644
index 00000000..d5d71f46
--- /dev/null
+++ b/common/safeMath.go
@@ -0,0 +1,40 @@
+/*
+ * Copyright (C) 2018 The ontology Authors
+ * This file is part of The ontology library.
+ *
+ * The ontology is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * The ontology is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with The ontology.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package common
+
+import "math"
+
+const (
+	MAX_UINT64 = math.MaxUint64
+)
+
+func SafeSub(x, y uint64) (uint64, bool) {
+	return x - y, x < y
+}
+
+func SafeAdd(x, y uint64) (uint64, bool) {
+	return x + y, y > MAX_UINT64-x
+}
+
+func SafeMul(x, y uint64) (uint64, bool) {
+	if x == 0 || y == 0 {
+		return 0, false
+	}
+	return x * y, y > MAX_UINT64/x
+}
diff --git a/core/store/ledgerstore/tx_handler.go b/core/store/ledgerstore/tx_handler.go
index 2cc992ca..c9502bd3 100644
--- a/core/store/ledgerstore/tx_handler.go
+++ b/core/store/ledgerstore/tx_handler.go
@@ -54,7 +54,12 @@ func (self *StateStore) HandleDeployTransaction(store store.LedgerStore, stateBa
 	)
 
 	if tx.GasPrice != 0 {
-		if err := isBalanceSufficient(tx, stateBatch); err != nil {
+		gas, overflow := common.SafeMul(tx.GasLimit, tx.GasPrice)
+		if overflow {
+			return fmt.Errorf("gaslimit:%d*gasprice:%d overflow!", tx.GasLimit, tx.GasPrice)
+		}
+
+		if err := isBalanceSufficient(tx.Payer, stateBatch, gas); err != nil {
 			return err
 		}
 
@@ -67,7 +72,7 @@ func (self *StateStore) HandleDeployTransaction(store store.LedgerStore, stateBa
 			Tx:     tx,
 		}
 
-		notifies, err = costGas(tx.Payer, tx.GasLimit*tx.GasPrice, config, cache, store)
+		notifies, err = costGas(tx.Payer, gas, config, cache, store)
 		if err != nil {
 			return err
 		}
@@ -94,8 +99,13 @@ func (self *StateStore) HandleInvokeTransaction(store store.LedgerStore, stateBa
 	sysTransFlag := bytes.Compare(code, ninit.COMMIT_DPOS_BYTES) == 0 || block.Header.Height == 0
 
 	isCharge := !sysTransFlag && tx.GasPrice != 0
+
+	gas, overflow := common.SafeMul(tx.GasLimit, tx.GasPrice)
+	if overflow {
+		return fmt.Errorf("gaslimit:%d*gasprice:%d overflow!", tx.GasLimit, tx.GasPrice)
+	}
 	if isCharge {
-		if err := isBalanceSufficient(tx, stateBatch); err != nil {
+		if err := isBalanceSufficient(tx.Payer, stateBatch, gas); err != nil {
 			return err
 		}
 	}
@@ -133,7 +143,7 @@ func (self *StateStore) HandleInvokeTransaction(store store.LedgerStore, stateBa
 		if totalGas < neovm.TRANSACTION_GAS {
 			totalGas = neovm.TRANSACTION_GAS
 		}
-		notifies, err = costGas(tx.Payer, totalGas*tx.GasPrice, config, sc.CloneCache, store)
+		notifies, err = costGas(tx.Payer, gas, config, sc.CloneCache, store)
 		if err != nil {
 			return err
 		}
@@ -171,13 +181,13 @@ func genNativeTransferCode(from, to common.Address, value uint64) []byte {
 }
 
 // check whether payer ong balance sufficient
-func isBalanceSufficient(tx *types.Transaction, stateBatch *statestore.StateBatch) error {
-	balance, err := getBalance(stateBatch, tx.Payer, utils.OngContractAddress)
+func isBalanceSufficient(payer common.Address, stateBatch *statestore.StateBatch, gas uint64) error {
+	balance, err := getBalance(stateBatch, payer, utils.OngContractAddress)
 	if err != nil {
 		return err
 	}
-	if balance < tx.GasLimit*tx.GasPrice {
-		return fmt.Errorf("payer gas insufficient, need %d , only have %d", tx.GasLimit*tx.GasPrice, balance)
+	if balance < gas {
+		return fmt.Errorf("payer gas insufficient, need %d , only have %d", gas, balance)
 	}
 	return nil
 }