From edf456985b10fa6f04013db24d73f30422b50a97 Mon Sep 17 00:00:00 2001
From: yihuang <huang@crypto.com>
Date: Wed, 16 Mar 2022 19:01:19 +0800
Subject: [PATCH] fix: set an upper bound to gasWanted to prevent DoS attack
 (#991)
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Closes: #989

Co-authored-by: Federico Kunze Küllmer <31522760+fedekunze@users.noreply.github.com>
---
 CHANGELOG.md         |  1 +
 app/ante/eth.go      | 15 +++++++++++++--
 app/ante/eth_test.go |  2 +-
 3 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7b042874..9f6f4f37 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -41,6 +41,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 ### Bug Fixes
 
 * (rpc) [tharsis#990](https://github.com/tharsis/ethermint/pull/990) Calculate reward values from all `MsgEthereumTx` from a block in `eth_feeHistory`.
+* (ante) [tharsis#991](https://github.com/tharsis/ethermint/pull/991) Set an upper bound to gasWanted to prevent DoS attack.
 
 ## [v0.11.0] - 2022-03-06
 
diff --git a/app/ante/eth.go b/app/ante/eth.go
index 0908377c..8ac9a6d6 100644
--- a/app/ante/eth.go
+++ b/app/ante/eth.go
@@ -17,6 +17,8 @@ import (
 	ethtypes "github.com/ethereum/go-ethereum/core/types"
 )
 
+const MaxTxGasWanted uint64 = 500000
+
 // EthSigVerificationDecorator validates an ethereum signatures
 type EthSigVerificationDecorator struct {
 	evmKeeper EVMKeeper
@@ -171,7 +173,6 @@ func (egcd EthGasConsumeDecorator) AnteHandle(ctx sdk.Context, tx sdk.Tx, simula
 	london := ethCfg.IsLondon(blockHeight)
 	evmDenom := params.EvmDenom
 	gasWanted := uint64(0)
-
 	var events sdk.Events
 
 	for _, msg := range tx.GetMsgs() {
@@ -184,7 +185,17 @@ func (egcd EthGasConsumeDecorator) AnteHandle(ctx sdk.Context, tx sdk.Tx, simula
 		if err != nil {
 			return ctx, sdkerrors.Wrap(err, "failed to unpack tx data")
 		}
-		gasWanted += txData.GetGas()
+
+		if ctx.IsCheckTx() {
+			// We can't trust the tx gas limit, because we'll refund the unused gas.
+			if txData.GetGas() > MaxTxGasWanted {
+				gasWanted += MaxTxGasWanted
+			} else {
+				gasWanted += txData.GetGas()
+			}
+		} else {
+			gasWanted += txData.GetGas()
+		}
 
 		fees, err := egcd.evmKeeper.DeductTxCostsFromUserBalance(
 			ctx,
diff --git a/app/ante/eth_test.go b/app/ante/eth_test.go
index 3490ba69..01a55734 100644
--- a/app/ante/eth_test.go
+++ b/app/ante/eth_test.go
@@ -268,7 +268,7 @@ func (suite AnteTestSuite) TestEthGasConsumeDecorator() {
 		{
 			"success",
 			tx2,
-			tx2GasLimit,
+			ante.MaxTxGasWanted, // it's capped
 			func() {
 				vmdb.AddBalance(addr, big.NewInt(1000000))