rpc: add CORS workaround for RPC

This one enables our RPC to be called from the browser if there is a
need. It's insecure and not standards-compliant, thus this behaviour is
configurable is not enabled by default. It makes our node with this workaround
enabled compatible with neo-mon monitoring.

Originally debugged by @anatoly-bogatyrev in #464.

cli/server/server.go

@@ -247,7 +247,7 @@ func startServer(ctx *cli.Context) error {
 	}
 
 	server := network.NewServer(serverConfig, chain)
-	rpcServer := rpc.NewServer(chain, cfg.ApplicationConfiguration.RPCPort, server)
+	rpcServer := rpc.NewServer(chain, cfg.ApplicationConfiguration.RPC, server)
 	errChan := make(chan error)
 	monitoring := metrics.NewMetricsService(cfg.ApplicationConfiguration.Monitoring)
 

config/config.go

@@ -67,7 +67,6 @@ type (
 	// ApplicationConfiguration config specific to the node.
 	ApplicationConfiguration struct {
 		DBConfiguration   storage.DBConfiguration  `yaml:"DBConfiguration"`
-		RPCPort           uint16                   `yaml:"RPCPort"`
 		NodePort          uint16                   `yaml:"NodePort"`
 		Relay             bool                     `yaml:"Relay"`
 		DialTimeout       time.Duration            `yaml:"DialTimeout"`
@@ -75,6 +74,15 @@ type (
 		MaxPeers          int                      `yaml:"MaxPeers"`
 		MinPeers          int                      `yaml:"MinPeers"`
 		Monitoring        metrics.PrometheusConfig `yaml:"Monitoring"`
+		RPC               RPCConfig                `yaml:"RPC"`
+	}
+
+	// RPCConfig is an RPC service configuration information (to be moved to the rpc package, see #423).
+	RPCConfig struct {
+		Enabled              bool   `yaml:"Enabled"`
+		EnableCORSWorkaround bool   `yaml:"EnableCORSWorkaround"`
+		Address              string `yaml:"Address"`
+		Port                 uint16 `yaml:"Port"`
 	}
 
 	// NetMode describes the mode the blockchain will operate on.

config/protocol.mainnet.yml

@@ -42,13 +42,16 @@ ApplicationConfiguration:
   #      DB: 0
   #    BoltDBOptions:
   #      FilePath: "./chains/mainnet.bolt"
-  RPCPort: 20332
   NodePort: 20333
   Relay: true
   DialTimeout: 3
   ProtoTickInterval: 2
   MaxPeers: 50
   MinPeers: 5
+  RPC:
+    Enabled: true
+    EnableCORSWorkaround: false
+    Port: 20332
   Monitoring:
     Enabled: true
     Port: 2112

config/protocol.privnet.docker.four.yml

@@ -30,13 +30,16 @@ ApplicationConfiguration:
   #      DB: 0
   #    BoltDBOptions:
   #      FilePath: "./chains/privnet.bolt"
-  RPCPort: 20336
   NodePort: 20337
   Relay: true
   DialTimeout: 3
   ProtoTickInterval: 2
   MaxPeers: 50
   MinPeers: 3
+  RPC:
+    Enabled: true
+    EnableCORSWorkaround: false
+    Port: 20336
   Monitoring:
     Enabled: true
     Port: 2112

config/protocol.privnet.docker.one.yml

@@ -27,13 +27,16 @@ ApplicationConfiguration:
   #      DB: 0
   #    BoltDBOptions:
   #      FilePath: "./chains/privnet.bolt"
-  RPCPort: 20333
   NodePort: 20334
   Relay: true
   DialTimeout: 3
   ProtoTickInterval: 2
   MaxPeers: 50
   MinPeers: 3
+  RPC:
+    Enabled: true
+    EnableCORSWorkaround: false
+    Port: 20333
   Monitoring:
     Enabled: true
     Port: 2112

config/protocol.privnet.docker.three.yml

@@ -27,13 +27,16 @@ ApplicationConfiguration:
   #      DB: 0
   #    BoltDBOptions:
   #      FilePath: "./chains/privnet.bolt"
-  RPCPort: 20335
   NodePort: 20336
   Relay: true
   DialTimeout: 3
   ProtoTickInterval: 2
   MaxPeers: 50
   MinPeers: 3
+  RPC:
+    Enabled: true
+    EnableCORSWorkaround: false
+    Port: 20335
   Monitoring:
     Enabled: true
     Port: 2112

config/protocol.privnet.docker.two.yml

@@ -27,13 +27,16 @@ ApplicationConfiguration:
   #      DB: 0
   #    BoltDBOptions:
   #      FilePath: "./chains/privnet.bolt"
-  RPCPort: 20334
   NodePort: 20335
   Relay: true
   DialTimeout: 3
   ProtoTickInterval: 2
   MaxPeers: 50
   MinPeers: 3
+  RPC:
+    Enabled: true
+    EnableCORSWorkaround: false
+    Port: 20334
   Monitoring:
     Enabled: true
     Port: 2112

config/protocol.privnet.yml

@@ -33,13 +33,16 @@ ApplicationConfiguration:
   #      DB: 0
   #    BoltDBOptions:
   #      FilePath: "./chains/privnet.bolt"
-  RPCPort: 20331
   NodePort: 20332
   Relay: true
   DialTimeout: 3
   ProtoTickInterval: 2
   MaxPeers: 50
   MinPeers: 3
+  RPC:
+    Enabled: true
+    EnableCORSWorkaround: false
+    Port: 20331
   Monitoring:
     Enabled: true
     Port: 2112

config/protocol.testnet.yml

@@ -42,13 +42,16 @@ ApplicationConfiguration:
   #      DB: 0
   #    BoltDBOptions:
   #      FilePath: "./chains/testnet.bolt"
-  RPCPort: 20332
   NodePort: 20333
   Relay: true
   DialTimeout: 3
   ProtoTickInterval: 2
   MaxPeers: 50
   MinPeers: 5
+  RPC:
+    Enabled: true
+    EnableCORSWorkaround: false
+    Port: 20332
   Monitoring:
     Enabled: true
     Port: 2112

config/protocol.unit_testnet.yml

@@ -32,13 +32,16 @@ ApplicationConfiguration:
   #      DB: 0
   #    BoltDBOptions:
   #      FilePath: "./chains/unit_testnet.bolt"
-  RPCPort: 20332
   NodePort: 20333
   Relay: true
   DialTimeout: 3
   ProtoTickInterval: 2
   MaxPeers: 50
   MinPeers: 1
+  RPC:
+    Enabled: true
+    EnableCORSWorkaround: false
+    Port: 20332
   Monitoring:
     Enabled: false #since it's not useful for unit tests.
     Port: 2112

go.mod

@@ -15,6 +15,8 @@ require (
 	github.com/gomodule/redigo v2.0.0+incompatible // indirect
 	github.com/mattn/go-colorable v0.1.2 // indirect
 	github.com/mattn/go-isatty v0.0.9 // indirect
+	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
+	github.com/modern-go/reflect2 v1.0.1 // indirect
 	github.com/mr-tron/base58 v1.1.2
 	github.com/nspcc-dev/rfc6979 v0.1.0
 	github.com/onsi/gomega v1.4.2 // indirect

pkg/rpc/request.go

@@ -21,6 +21,7 @@ type (
 		Method               string          `json:"method"`
 		RawParams            json.RawMessage `json:"params,omitempty"`
 		RawID                json.RawMessage `json:"id,omitempty"`
+		enableCORSWorkaround bool
 	}
 
 	// Response represents a standard JSON-RPC 2.0
@@ -34,9 +35,10 @@ type (
 )
 
 // NewRequest creates a new Request struct.
-func NewRequest() *Request {
+func NewRequest(corsWorkaround bool) *Request {
 	return &Request{
 		JSONRPC:              jsonRPCVersion,
+		enableCORSWorkaround: corsWorkaround,
 	}
 }
 
@@ -110,6 +112,11 @@ func (r Request) WriteResponse(w http.ResponseWriter, result interface{}) {
 
 func (r Request) writeServerResponse(w http.ResponseWriter, response Response) {
 	w.Header().Set("Content-Type", "application/json; charset=utf-8")
+	if r.enableCORSWorkaround {
+		w.Header().Set("Access-Control-Allow-Origin", "*")
+		w.Header().Set("Access-Control-Allow-Headers", "Content-Type, Access-Control-Allow-Headers, Authorization, X-Requested-With")
+	}
+
 	encoder := json.NewEncoder(w)
 	err := encoder.Encode(response)
 

pkg/rpc/server.go

@@ -7,6 +7,7 @@ import (
 	"net/http"
 	"strconv"
 
+	"github.com/CityOfZion/neo-go/config"
 	"github.com/CityOfZion/neo-go/pkg/core"
 	"github.com/CityOfZion/neo-go/pkg/core/transaction"
 	"github.com/CityOfZion/neo-go/pkg/crypto"
@@ -24,6 +25,7 @@ type (
 	Server struct {
 		*http.Server
 		chain      core.Blockchainer
+		config     config.RPCConfig
 		coreServer *network.Server
 	}
 )
@@ -35,12 +37,15 @@ var (
 )
 
 // NewServer creates a new Server struct.
-func NewServer(chain core.Blockchainer, port uint16, coreServer *network.Server) Server {
+func NewServer(chain core.Blockchainer, conf config.RPCConfig, coreServer *network.Server) Server {
+	httpServer := &http.Server{
+		Addr: conf.Address + ":" + strconv.FormatUint(uint64(conf.Port), 10),
+	}
+
 	return Server{
-		Server: &http.Server{
+		Server:     httpServer,
-			Addr: ":" + strconv.FormatUint(uint64(port), 10),
-		},
 		chain:      chain,
+		config:     conf,
 		coreServer: coreServer,
 	}
 }
@@ -48,6 +53,10 @@ func NewServer(chain core.Blockchainer, port uint16, coreServer *network.Server)
 // Start creates a new JSON-RPC server
 // listening on the configured port.
 func (s *Server) Start(errChan chan error) {
+	if !s.config.Enabled {
+		log.Info("RPC server is not enabled")
+		return
+	}
 	s.Handler = http.HandlerFunc(s.requestHandler)
 	log.WithFields(log.Fields{
 		"endpoint": s.Addr,
@@ -66,7 +75,7 @@ func (s *Server) Shutdown() error {
 }
 
 func (s *Server) requestHandler(w http.ResponseWriter, httpRequest *http.Request) {
-	req := NewRequest()
+	req := NewRequest(s.config.EnableCORSWorkaround)
 
 	if httpRequest.Method != "POST" {
 		req.WriteErrorResponse(

pkg/rpc/server_helper_test.go

@@ -167,7 +167,7 @@ func initServerWithInMemoryChain(ctx context.Context, t *testing.T) (*core.Block
 
 	serverConfig := network.NewServerConfig(cfg)
 	server := network.NewServer(serverConfig, chain)
-	rpcServer := NewServer(chain, cfg.ApplicationConfiguration.RPCPort, server)
+	rpcServer := NewServer(chain, cfg.ApplicationConfiguration.RPC, server)
 	handler := http.HandlerFunc(rpcServer.requestHandler)
 
 	return chain, handler