Full implementation of Socks5 protocol, proxying is on the way

io/socks/socks.go

@@ -68,12 +68,15 @@ func (r *Socks5AuthenticationResponse) ToBytes() []byte {
 
 func WriteAuthentication(writer io.Writer, response Socks5AuthenticationResponse) error {
 	_, err := writer.Write(response.ToBytes())
-	if err != nil {
-		return err
-	}
-	return nil
+	return err
 }
 
+const (
+	AddrTypeIPv4   = byte(0x01)
+	AddrTypeIPv6   = byte(0x04)
+	AddrTypeDomain = byte(0x03)
+)
+
 type Socks5Request struct {
 	version  byte
 	command  byte
@@ -149,3 +152,51 @@ func ReadRequest(reader io.Reader) (request *Socks5Request, err error) {
 	request.port = binary.BigEndian.Uint16(buffer)
 	return
 }
+
+const (
+	ErrorSuccess                 = byte(0x00)
+	ErrorGeneralFailure          = byte(0x01)
+	ErrorConnectionNotAllowed    = byte(0x02)
+	ErrorNetworkUnreachable      = byte(0x03)
+	ErrorHostUnUnreachable       = byte(0x04)
+	ErrorConnectionRefused       = byte(0x05)
+	ErrorTTLExpired              = byte(0x06)
+	ErrorCommandNotSupported     = byte(0x07)
+	ErrorAddressTypeNotSupported = byte(0x08)
+)
+
+type Socks5Response struct {
+	Version  byte
+	Error    byte
+	AddrType byte
+	IPv4     [4]byte
+	Domain   string
+	IPv6     [16]byte
+	Port     uint16
+}
+
+func (r Socks5Response) toBytes() []byte {
+	buffer := make([]byte, 0, 300)
+	buffer = append(buffer, r.Version)
+	buffer = append(buffer, r.Error)
+	buffer = append(buffer, 0x00) // reserved
+	buffer = append(buffer, r.AddrType)
+	switch r.AddrType {
+	case 0x01:
+		buffer = append(buffer, r.IPv4[:]...)
+	case 0x03:
+		buffer = append(buffer, byte(len(r.Domain)))
+		buffer = append(buffer, []byte(r.Domain)...)
+	case 0x04:
+		buffer = append(buffer, r.IPv6[:]...)
+	}
+	portBuffer := make([]byte, 2)
+	binary.BigEndian.PutUint16(portBuffer, r.Port)
+	buffer = append(buffer, portBuffer...)
+	return buffer
+}
+
+func WriteResponse(writer io.Writer, response Socks5Response) error {
+	_, err := writer.Write(response.toBytes())
+	return err
+}

io/socks/socks_test.go

@@ -68,3 +68,27 @@ func TestRequestRead(t *testing.T) {
 		t.Errorf("Expected port 53, but got %d", request.port)
 	}
 }
+
+func TestResponseToBytes(t *testing.T) {
+	response := Socks5Response{
+		socksVersion,
+		ErrorSuccess,
+		AddrTypeIPv4,
+		[4]byte{0x72, 0x72, 0x72, 0x72},
+		"",
+		[16]byte{},
+		uint16(53),
+	}
+	rawResponse := response.toBytes()
+	expectedBytes := []byte{
+		socksVersion,
+		ErrorSuccess,
+		byte(0x00),
+		AddrTypeIPv4,
+		0x72, 0x72, 0x72, 0x72,
+		byte(0x00), byte(0x035),
+	}
+	if !bytes.Equal(rawResponse, expectedBytes) {
+		t.Errorf("Expected response %v, but got %v", expectedBytes, rawResponse)
+	}
+}