evm: state transitions enabled params (#603)

* changelog

* evm: state transitions enabled params

* changelog entry

* changelog

x/evm/types/errors.go

@@ -15,4 +15,10 @@ var (
 
 	// ErrInvalidChainConfig returns an error resulting from an invalid ChainConfig.
 	ErrInvalidChainConfig = sdkerrors.Register(ModuleName, 4, "invalid chain configuration")
+
+	// ErrCreateDisabled returns an error if the EnableCreate parameter is false.
+	ErrCreateDisabled = sdkerrors.Register(ModuleName, 5, "EVM Create operation is disabled")
+
+	// ErrCallDisabled returns an error if the EnableCall parameter is false.
+	ErrCallDisabled = sdkerrors.Register(ModuleName, 6, "EVM Call operation is disabled")
 )

x/evm/types/params.go

@@ -18,7 +18,9 @@ const (
 
 // Parameter keys
 var (
-	ParamStoreKeyEVMDenom = []byte("EVMDenom")
+	ParamStoreKeyEVMDenom     = []byte("EVMDenom")
+	ParamStoreKeyEnableCreate = []byte("EnableCreate")
+	ParamStoreKeyEnableCall   = []byte("EnableCall")
 )
 
 // ParamKeyTable returns the parameter key table.
@@ -28,20 +30,30 @@ func ParamKeyTable() params.KeyTable {
 
 // Params defines the EVM module parameters
 type Params struct {
+	// EVMDenom defines the token denomination used for state transitions on the
+	// EVM module.
 	EvmDenom string `json:"evm_denom" yaml:"evm_denom"`
+	// EnableCreate toggles state transitions that use the vm.Create function
+	EnableCreate bool `json:"enable_create" yaml:"enable_create"`
+	// EnableCall toggles state transitions that use the vm.Call function
+	EnableCall bool `json:"enable_call" yaml:"enable_call"`
 }
 
 // NewParams creates a new Params instance
-func NewParams(evmDenom string) Params {
+func NewParams(evmDenom string, enableCreate, enableCall bool) Params {
 	return Params{
-		EvmDenom: evmDenom,
+		EvmDenom:     evmDenom,
+		EnableCreate: enableCreate,
+		EnableCall:   enableCall,
 	}
 }
 
 // DefaultParams returns default evm parameters
 func DefaultParams() Params {
 	return Params{
-		EvmDenom: ethermint.AttoPhoton,
+		EvmDenom:     ethermint.AttoPhoton,
+		EnableCreate: true,
+		EnableCall:   true,
 	}
 }
 
@@ -55,6 +67,8 @@ func (p Params) String() string {
 func (p *Params) ParamSetPairs() params.ParamSetPairs {
 	return params.ParamSetPairs{
 		params.NewParamSetPair(ParamStoreKeyEVMDenom, &p.EvmDenom, validateEVMDenom),
+		params.NewParamSetPair(ParamStoreKeyEnableCreate, &p.EnableCreate, validateBool),
+		params.NewParamSetPair(ParamStoreKeyEnableCall, &p.EnableCall, validateBool),
 	}
 }
 
@@ -66,8 +80,16 @@ func (p Params) Validate() error {
 func validateEVMDenom(i interface{}) error {
 	denom, ok := i.(string)
 	if !ok {
-		return fmt.Errorf("invalid parameter type: %T", i)
+		return fmt.Errorf("invalid parameter EVM denom type: %T", i)
 	}
 
 	return sdk.ValidateDenom(denom)
 }
+
+func validateBool(i interface{}) error {
+	_, ok := i.(bool)
+	if !ok {
+		return fmt.Errorf("invalid parameter type: %T", i)
+	}
+	return nil
+}

x/evm/types/params_test.go

@@ -15,7 +15,7 @@ func TestParamsValidate(t *testing.T) {
 		{"default", DefaultParams(), false},
 		{
 			"valid",
-			NewParams("ara"),
+			NewParams("ara", true, true),
 			false,
 		},
 		{
@@ -45,8 +45,11 @@ func TestParamsValidate(t *testing.T) {
 
 func TestParamsValidatePriv(t *testing.T) {
 	require.Error(t, validateEVMDenom(false))
+	require.NoError(t, validateEVMDenom("aphoton"))
+	require.Error(t, validateBool(""))
+	require.NoError(t, validateBool(true))
 }
 
 func TestParams_String(t *testing.T) {
-	require.Equal(t, "evm_denom: aphoton\n", DefaultParams().String())
+	require.Equal(t, "evm_denom: aphoton\nenable_create: true\nenable_call: true\n", DefaultParams().String())
 }

x/evm/types/state_transition.go

@@ -101,8 +101,9 @@ func (st StateTransition) TransitionDb(ctx sdk.Context, config ChainConfig) (*Ex
 	// Clear cache of accounts to handle changes outside of the EVM
 	csdb.UpdateAccounts()
 
-	evmDenom := csdb.GetParams().EvmDenom
-	gasPrice := ctx.MinGasPrices().AmountOf(evmDenom)
+	params := csdb.GetParams()
+
+	gasPrice := ctx.MinGasPrices().AmountOf(params.EvmDenom)
 	if gasPrice.IsNil() {
 		return nil, errors.New("gas price cannot be nil")
 	}
@@ -125,9 +126,17 @@ func (st StateTransition) TransitionDb(ctx sdk.Context, config ChainConfig) (*Ex
 	// create contract or execute call
 	switch contractCreation {
 	case true:
+		if !params.EnableCreate {
+			return nil, ErrCreateDisabled
+		}
+
 		ret, contractAddress, leftOverGas, err = evm.Create(senderRef, st.Payload, gasLimit, st.Amount)
 		recipientLog = fmt.Sprintf("contract address %s", contractAddress.String())
 	default:
+		if !params.EnableCall {
+			return nil, ErrCreateDisabled
+		}
+
 		// Increment the nonce for the next transaction	(just for evm state transition)
 		csdb.SetNonce(st.Sender, csdb.GetNonce(st.Sender)+1)
 		ret, leftOverGas, err = evm.Call(senderRef, *st.Recipient, st.Payload, gasLimit, st.Amount)