socks5 server implementation

net/socks/socks.go

@@ -1,7 +1,15 @@
 package socks
 
 import (
+	"errors"
 	"net"
+
+	socksio "github.com/v2ray/v2ray-core/io/socks"
+)
+
+var (
+	ErrorAuthenticationFailed = errors.New("None of the authentication methods is allowed.")
+	ErrorCommandNotSupported  = errors.New("Client requested an unsupported command.")
 )
 
 // SocksServer is a SOCKS 5 proxy server
@@ -31,5 +39,33 @@ func (server *SocksServer) AcceptConnections(listener net.Listener) error {
 }
 
 func (server *SocksServer) HandleConnection(connection net.Conn) error {
+	defer connection.Close()
+
+	auth, err := socksio.ReadAuthentication(connection)
+	if err != nil {
+		return err
+	}
+
+	if auth.HasAuthMethod(socksio.AuthNotRequired) {
+		return ErrorAuthenticationFailed
+	}
+
+	authResponse := socksio.NewAuthenticationResponse(socksio.AuthNotRequired)
+	socksio.WriteAuthentication(connection, authResponse)
+
+	request, err := socksio.ReadRequest(connection)
+	if err != nil {
+		return err
+	}
+
+	if request.Command == socksio.CmdBind || request.Command == socksio.CmdUdpAssociate {
+		response := socksio.NewSocks5Response()
+		response.Error = socksio.ErrorCommandNotSupported
+		socksio.WriteResponse(connection, response)
+		return ErrorCommandNotSupported
+	}
+
+	// TODO: establish connection with VNext
+
 	return nil
 }