rpc: configure gas cap (#457)

* rpc: configure gas cap

* c++

* rm old const

* docs

server/config/config.go

@@ -1,6 +1,7 @@
 package config
 
 import (
+	"errors"
 	"fmt"
 
 	"github.com/spf13/viper"
@@ -24,6 +25,8 @@ const (
 
 	// DefaultEVMTracer is the default vm.Tracer type
 	DefaultEVMTracer = "json"
+
+	DefaultGasCap uint64 = 25000000
 )
 
 var (
@@ -113,6 +116,27 @@ type JSONRPCConfig struct {
 	Enable bool `mapstructure:"enable"`
 	// EnableUnsafeCORS defines if CORS should be enabled (unsafe - use it at your own risk)
 	EnableUnsafeCORS bool `mapstructure:"enable-unsafe-cors"`
+	// GasCap is the global gas cap for eth-call variants.
+	GasCap uint64 `mapstructure:"gas-cap"`
+}
+
+// Validate returns an error if the JSON-RPC configuration fields are invalid.
+func (c JSONRPCConfig) Validate() error {
+	if c.Enable && len(c.API) == 0 {
+		return errors.New("cannot enable JSON-RPC without defining any API namespace")
+	}
+
+	// TODO: validate APIs
+	seenAPIs := make(map[string]bool)
+	for _, api := range c.API {
+		if seenAPIs[api] {
+			return fmt.Errorf("repeated API namespace '%s'", api)
+		}
+
+		seenAPIs[api] = true
+	}
+
+	return nil
 }
 
 // DefaultJSONRPCConfig returns an EVM config with the JSON-RPC API enabled by default
@@ -123,6 +147,7 @@ func DefaultJSONRPCConfig() *JSONRPCConfig {
 		Address:          DefaultJSONRPCAddress,
 		WsAddress:        DefaultJSONRPCWsAddress,
 		EnableUnsafeCORS: false,
+		GasCap:           DefaultGasCap,
 	}
 }
 
@@ -150,17 +175,29 @@ func GetConfig(v *viper.Viper) Config {
 			Address:          v.GetString("json-rpc.address"),
 			WsAddress:        v.GetString("json-rpc.ws-address"),
 			EnableUnsafeCORS: v.GetBool("json-rpc.enable-unsafe-cors"),
+			GasCap:           v.GetUint64("json-rpc.gas-cap"),
 		},
 	}
 }
 
+// ParseConfig retrieves the default environment configuration for the
+// application.
+func ParseConfig(v *viper.Viper) (*Config, error) {
+	conf := DefaultConfig()
+	err := v.Unmarshal(conf)
+
+	return conf, err
+}
+
 // ValidateBasic returns an error any of the application configuration fields are invalid
 func (c Config) ValidateBasic() error {
 	if err := c.EVM.Validate(); err != nil {
 		return sdkerrors.Wrapf(sdkerrors.ErrAppConfig, "invalid evm config value: %s", err.Error())
 	}
 
-	// TODO: validate JSON-RPC APIs
+	if err := c.JSONRPC.Validate(); err != nil {
+		return sdkerrors.Wrapf(sdkerrors.ErrAppConfig, "invalid json-rpc config value: %s", err.Error())
+	}
 
 	return c.Config.ValidateBasic()
 }

server/config/toml.go

@@ -34,4 +34,7 @@ api = "{{range $index, $elmt := .JSONRPC.API}}{{if $index}},{{$elmt}}{{else}}{{$
 
 # EnableUnsafeCORS defines if CORS should be enabled (unsafe - use it at your own risk)
 enable-unsafe-cors = "{{ .JSONRPC.EnableUnsafeCORS }}"
+
+# GasCap sets a cap on gas that can be used in eth_call/estimateGas (0=infinite). Default: 25,000,000.
+gas-cap = {{ .JSONRPC.GasCap }}
 `

server/flags/flags.go

@@ -31,6 +31,7 @@ const (
 	JSONRPCAddress       = "json-rpc.address"
 	JSONWsAddress        = "json-rpc.ws-address"
 	JSONEnableUnsafeCORS = "json-rpc.enable-unsafe-cors"
+	JSONRPCGasCap        = "json-rpc.gas-cap"
 )
 
 // EVM flags

server/start.go

@@ -143,6 +143,7 @@ which accepts a path for the resulting pprof file.
 	cmd.Flags().String(srvflags.JSONRPCAddress, config.DefaultJSONRPCAddress, "the JSON-RPC server address to listen on")
 	cmd.Flags().String(srvflags.JSONWsAddress, config.DefaultJSONRPCWsAddress, "the JSON-RPC WS server address to listen on")
 	cmd.Flags().Bool(srvflags.JSONEnableUnsafeCORS, false, "Define if the JSON-RPC server should enabled CORS (unsafe - use it at your own risk)")
+	cmd.Flags().Uint64(srvflags.JSONRPCGasCap, config.DefaultGasCap, "Sets a cap on gas that can be used in eth_call/estimateGas (0=infinite)")
 
 	cmd.Flags().String(srvflags.EVMTracer, config.DefaultEVMTracer, "the EVM tracer type to collect execution traces from the EVM transaction execution (json|struct|access_list|markdown)")