Refactor socks

protocol/socks/socks4/protocol.go

@@ -0,0 +1,170 @@
+package socks4
+
+import (
+	"bytes"
+	"encoding/binary"
+	"io"
+	"net/netip"
+	"os"
+
+	E "github.com/sagernet/sing/common/exceptions"
+	M "github.com/sagernet/sing/common/metadata"
+	"github.com/sagernet/sing/common/rw"
+)
+
+const (
+	Version byte = 4
+
+	CommandConnect byte = 1
+	CommandBind    byte = 2
+
+	ReplyCodeGranted                     byte = 90
+	ReplyCodeRejectedOrFailed            byte = 91
+	ReplyCodeCannotConnectToIdentd       byte = 92
+	ReplyCodeIdentdReportDifferentUserID byte = 93
+)
+
+type Request struct {
+	Command     byte
+	Destination M.Socksaddr
+	Username    string
+}
+
+func ReadRequest(reader io.Reader) (request Request, err error) {
+	version, err := rw.ReadByte(reader)
+	if err != nil {
+		return
+	}
+	if version != 4 {
+		err = E.New("excepted socks version 4, got ", version)
+		return
+	}
+	return ReadRequest0(reader)
+}
+
+func ReadRequest0(reader io.Reader) (request Request, err error) {
+	request.Command, err = rw.ReadByte(reader)
+	if err != nil {
+		return
+	}
+	err = binary.Read(reader, binary.BigEndian, &request.Destination.Port)
+	if err != nil {
+		return
+	}
+	var dstIP [4]byte
+	_, err = io.ReadFull(reader, dstIP[:])
+	if err != nil {
+		return
+	}
+	var readHostName bool
+	if dstIP[0] == 0 && dstIP[1] == 0 && dstIP[2] == 0 {
+		readHostName = true
+	} else {
+		request.Destination.Addr = netip.AddrFrom4(dstIP)
+	}
+	request.Username, err = readString(reader)
+	if readHostName {
+		request.Destination.Fqdn, err = readString(reader)
+	}
+	return
+}
+
+func WriteRequest(writer io.Writer, request Request) error {
+	if request.Command != CommandConnect && request.Command != CommandBind {
+		return os.ErrInvalid
+	}
+	_, err := writer.Write([]byte{Version, request.Command})
+	if err != nil {
+		return err
+	}
+	err = binary.Write(writer, binary.BigEndian, request.Destination.Port)
+	if err != nil {
+		return err
+	}
+	if request.Destination.Family().IsIPv4() {
+		dstIP := request.Destination.Addr.As4()
+		_, err = writer.Write(dstIP[:])
+		if err != nil {
+			return err
+		}
+	} else {
+		err = rw.WriteZeroN(writer, 4)
+		if err != nil {
+			return err
+		}
+		_, err = writer.Write([]byte(request.Destination.AddrString()))
+		if err != nil {
+			return err
+		}
+		err = rw.WriteZero(writer)
+		if err != nil {
+			return err
+		}
+	}
+	if request.Username != "" {
+		_, err = writer.Write([]byte(request.Username))
+		if err != nil {
+			return err
+		}
+	}
+	return rw.WriteZero(writer)
+}
+
+type Response struct {
+	ReplyCode   byte
+	Destination M.Socksaddr
+}
+
+func ReadResponse(reader io.Reader) (response Response, err error) {
+	version, err := rw.ReadByte(reader)
+	if err != nil {
+		return
+	}
+	if version != 4 {
+		err = E.New("excepted socks version 4, got ", version)
+		return
+	}
+	response.ReplyCode, err = rw.ReadByte(reader)
+	if err != nil {
+		return
+	}
+	err = binary.Read(reader, binary.BigEndian, &response.Destination.Port)
+	if err != nil {
+		return
+	}
+	var dstIP [4]byte
+	_, err = io.ReadFull(reader, dstIP[:])
+	if err != nil {
+		return
+	}
+	response.Destination.Addr = netip.AddrFrom4(dstIP)
+	return
+}
+
+func WriteResponse(writer io.Writer, response Response) error {
+	_, err := writer.Write([]byte{Version, response.ReplyCode})
+	if err != nil {
+		return err
+	}
+	err = binary.Write(writer, binary.BigEndian, response.Destination.Port)
+	if err != nil {
+		return err
+	}
+	dstIP := response.Destination.Addr.As4()
+	return rw.WriteBytes(writer, dstIP[:])
+}
+
+func readString(reader io.Reader) (string, error) {
+	buffer := bytes.Buffer{}
+	for {
+		b, err := rw.ReadByte(reader)
+		if err != nil {
+			return "", err
+		}
+		if b == 0 {
+			break
+		}
+		buffer.WriteByte(b)
+	}
+	return buffer.String(), nil
+}