From 51ff5d48a9b3319cecff89f99782a765c2c09be6 Mon Sep 17 00:00:00 2001
From: Austin Abell <austinabell8@gmail.com>
Date: Tue, 29 Oct 2019 11:52:26 -0400
Subject: [PATCH] Fixes gas limit for simulated transaction (#130)

* Fixes call gas limit for stdTxs

* reword comment
---
 app/ante.go                     |  4 ++--
 x/evm/handler.go                |  4 ++--
 x/evm/types/state_transition.go | 21 ++++++++++++++++-----
 3 files changed, 20 insertions(+), 9 deletions(-)

diff --git a/app/ante.go b/app/ante.go
index fe4e00e8..8a110392 100644
--- a/app/ante.go
+++ b/app/ante.go
@@ -257,7 +257,7 @@ func ethAnteHandler(
 	// Set gas meter after ante handler to ignore gaskv costs
 	newCtx = auth.SetGasMeter(sim, ctx, ethTxMsg.Data.GasLimit)
 
-	gas, _ := ethcore.IntrinsicGas(ethTxMsg.Data.Payload, ethTxMsg.To() == nil, false)
+	gas, _ := ethcore.IntrinsicGas(ethTxMsg.Data.Payload, ethTxMsg.To() == nil, true)
 	newCtx.GasMeter().ConsumeGas(gas, "eth intrinsic gas")
 
 	return newCtx, sdk.Result{}, false
@@ -313,7 +313,7 @@ func validateSignature(ctx sdk.Context, ethTxMsg *evmtypes.EthereumTxMsg) (sdk.A
 // constant value of 21000 plus any cost inccured by additional bytes of data
 // supplied with the transaction.
 func validateIntrinsicGas(ethTxMsg *evmtypes.EthereumTxMsg) sdk.Result {
-	gas, err := ethcore.IntrinsicGas(ethTxMsg.Data.Payload, ethTxMsg.To() == nil, false)
+	gas, err := ethcore.IntrinsicGas(ethTxMsg.Data.Payload, ethTxMsg.To() == nil, true)
 	if err != nil {
 		return sdk.ErrInternal(fmt.Sprintf("failed to compute intrinsic gas cost: %s", err)).Result()
 	}
diff --git a/x/evm/handler.go b/x/evm/handler.go
index ebd641e4..4b121203 100644
--- a/x/evm/handler.go
+++ b/x/evm/handler.go
@@ -73,7 +73,7 @@ func handleETHTxMsg(ctx sdk.Context, keeper Keeper, msg types.EthereumTxMsg) sdk
 	keeper.csdb.Prepare(ethHash, common.Hash{}, keeper.txCount.get())
 	keeper.txCount.increment()
 
-	res, bloom := st.TransitionCSDB(ctx)
+	bloom, res := st.TransitionCSDB(ctx)
 	keeper.bloom.Or(keeper.bloom, bloom)
 	return res
 }
@@ -110,6 +110,6 @@ func handleEmintMsg(ctx sdk.Context, keeper Keeper, msg types.EmintMsg) sdk.Resu
 	keeper.csdb.Prepare(common.Hash{}, common.Hash{}, keeper.txCount.get()) // Cannot provide tx hash
 	keeper.txCount.increment()
 
-	res, _ := st.TransitionCSDB(ctx)
+	_, res := st.TransitionCSDB(ctx)
 	return res
 }
diff --git a/x/evm/types/state_transition.go b/x/evm/types/state_transition.go
index 9c35ef96..0e1eff0e 100644
--- a/x/evm/types/state_transition.go
+++ b/x/evm/types/state_transition.go
@@ -29,15 +29,26 @@ type StateTransition struct {
 }
 
 // TransitionCSDB performs an evm state transition from a transaction
-func (st StateTransition) TransitionCSDB(ctx sdk.Context) (sdk.Result, *big.Int) {
+func (st StateTransition) TransitionCSDB(ctx sdk.Context) (*big.Int, sdk.Result) {
 	contractCreation := st.Recipient == nil
 
 	if res := st.checkNonce(); !res.IsOK() {
-		return res, nil
+		return nil, res
+	}
+
+	cost, err := core.IntrinsicGas(st.Payload, st.Recipient == nil, true)
+	if err != nil {
+		return nil, sdk.ErrOutOfGas("invalid intrinsic gas for transaction").Result()
 	}
 
 	// This gas limit the the transaction gas limit with intrinsic gas subtracted
-	gasLimit := ctx.GasMeter().Limit()
+	gasLimit := st.GasLimit - ctx.GasMeter().GasConsumed()
+
+	if st.Simulate {
+		// gasLimit is set here because stdTxs incur gaskv charges in the ante handler, but for eth_call
+		// the cost needs to be the same as an Ethereum transaction sent through the web3 API
+		gasLimit = st.GasLimit - cost
+	}
 
 	// Create context for evm
 	context := vm.Context{
@@ -92,7 +103,7 @@ func (st StateTransition) TransitionCSDB(ctx sdk.Context) (sdk.Result, *big.Int)
 	if vmerr != nil {
 		res := emint.ErrVMExecution(vmerr.Error()).Result()
 		res.Data = returnData
-		return res, nil
+		return nil, res
 	}
 
 	// TODO: Refund unused gas here, if intended in future
@@ -103,7 +114,7 @@ func (st StateTransition) TransitionCSDB(ctx sdk.Context) (sdk.Result, *big.Int)
 	// Out of gas check does not need to be done here since it is done within the EVM execution
 	ctx.GasMeter().ConsumeGas(gasLimit-leftOverGas, "EVM execution consumption")
 
-	return sdk.Result{Data: returnData, GasUsed: st.GasLimit - leftOverGas}, bloomInt
+	return bloomInt, sdk.Result{Data: returnData, GasUsed: st.GasLimit - leftOverGas}
 }
 
 func (st *StateTransition) checkNonce() sdk.Result {