From f14c4c7797e6dfe275701645911298d740568e00 Mon Sep 17 00:00:00 2001
From: "mr.The" <mrThe@users.noreply.github.com>
Date: Mon, 13 Apr 2020 07:22:03 +0300
Subject: [PATCH] socks4: add support for socks4 proxy (#114)

---
 main.go                |   1 +
 proxy/socks4/socks4.go | 168 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 169 insertions(+)
 create mode 100644 proxy/socks4/socks4.go

diff --git a/main.go b/main.go
index f920ca5..872f805 100644
--- a/main.go
+++ b/main.go
@@ -19,6 +19,7 @@ import (
 	_ "github.com/nadoo/glider/proxy/mixed"
 	_ "github.com/nadoo/glider/proxy/obfs"
 	_ "github.com/nadoo/glider/proxy/reject"
+	_ "github.com/nadoo/glider/proxy/socks4"
 	_ "github.com/nadoo/glider/proxy/socks5"
 	_ "github.com/nadoo/glider/proxy/ss"
 	_ "github.com/nadoo/glider/proxy/ssr"
diff --git a/proxy/socks4/socks4.go b/proxy/socks4/socks4.go
new file mode 100644
index 0000000..61c5471
--- /dev/null
+++ b/proxy/socks4/socks4.go
@@ -0,0 +1,168 @@
+// https://www.openssh.com/txt/socks4.protocol
+
+// socks4 client
+
+package socks4
+
+import (
+	"errors"
+	"io"
+	"net"
+	"net/url"
+	"strconv"
+
+	"github.com/nadoo/glider/common/log"
+	"github.com/nadoo/glider/proxy"
+)
+
+const (
+	// Version is socks4 version number.
+	Version = 4
+	// ConnectCommand connect command byte
+	ConnectCommand = 1
+)
+
+// SOCKS4 is a base socks4 struct.
+type SOCKS4 struct {
+	dialer proxy.Dialer
+	addr   string
+}
+
+func init() {
+	proxy.RegisterDialer("socks4", NewSocks4Dialer)
+}
+
+// NewSOCKS4 returns a Proxy that makes SOCKS v5 connections to the given address
+// with an optional username and password. (RFC 1928)
+func NewSOCKS4(s string, dialer proxy.Dialer) (*SOCKS4, error) {
+	u, err := url.Parse(s)
+	if err != nil {
+		log.F("parse err: %s", err)
+		return nil, err
+	}
+
+	h := &SOCKS4{
+		dialer: dialer,
+		addr:   u.Host,
+	}
+
+	return h, nil
+}
+
+// NewSocks4Dialer returns a socks4 proxy dialer.
+func NewSocks4Dialer(s string, dialer proxy.Dialer) (proxy.Dialer, error) {
+	return NewSOCKS4(s, dialer)
+}
+
+// Addr returns forwarder's address.
+func (s *SOCKS4) Addr() string {
+	if s.addr == "" {
+		return s.dialer.Addr()
+	}
+	return s.addr
+}
+
+// NextDialer returns the next dialer.
+func (s *SOCKS4) NextDialer(dstAddr string) proxy.Dialer { return s.dialer.NextDialer(dstAddr) }
+
+// Dial connects to the address addr on the network net via the SOCKS4 proxy.
+func (s *SOCKS4) Dial(network, addr string) (net.Conn, error) {
+	switch network {
+	case "tcp", "tcp4":
+	default:
+		return nil, errors.New("[socks4]: no support for connection type " + network)
+	}
+
+	c, err := s.dialer.Dial(network, s.addr)
+	if err != nil {
+		log.F("[socks4]: dial to %s error: %s", s.addr, err)
+		return nil, err
+	}
+
+	if err := s.connect(c, addr); err != nil {
+		c.Close()
+		return nil, err
+	}
+
+	return c, nil
+}
+
+// DialUDP connects to the given address via the proxy.
+func (s *SOCKS4) DialUDP(network, addr string) (pc net.PacketConn, writeTo net.Addr, err error) {
+	return nil, nil, errors.New("DialUDP are not supported by Socks4")
+}
+
+func (s *SOCKS4) lookupIP(host string) (ip net.IP, err error) {
+	ips, err := net.LookupIP(host)
+	if err != nil {
+		return
+	}
+	if len(ips) == 0 {
+		err = errors.New("Cannot resolve host: " + host)
+		return
+	}
+	ip = ips[0].To4()
+	if len(ip) != net.IPv4len {
+		err = errors.New("IPv6 is not supported by socks4")
+		return
+	}
+	return
+}
+
+// connect takes an existing connection to a socks4 proxy server,
+// and commands the server to extend that connection to target,
+// which must be a canonical address with a host and port.
+func (s *SOCKS4) connect(conn net.Conn, target string) error {
+	host, portStr, err := net.SplitHostPort(target)
+	if err != nil {
+		return err
+	}
+
+	port, err := strconv.Atoi(portStr)
+	if err != nil {
+		return errors.New("proxy: failed to parse port number: " + portStr)
+	}
+	if port < 1 || port > 0xffff {
+		return errors.New("proxy: port number out of range: " + portStr)
+	}
+
+	ip, err := s.lookupIP(host)
+	if err != nil {
+		return err
+	}
+
+	// taken from https://github.com/h12w/socks/blob/master/socks.go
+	buf := []byte{
+		Version,
+		ConnectCommand,
+		byte(port >> 8), // higher byte of destination port
+		byte(port),      // lower byte of destination port (big endian)
+		ip[0], ip[1], ip[2], ip[3],
+		0, // user id
+	}
+
+	resp := make([]byte, 8)
+
+	if _, err := conn.Write(buf); err != nil {
+		return errors.New("proxy: failed to write greeting to socks4 proxy at " + s.addr + ": " + err.Error())
+	}
+
+	if _, err := io.ReadFull(conn, resp); err != nil {
+		return errors.New("proxy: failed to read greeting from socks4 proxy at " + s.addr + ": " + err.Error())
+	}
+
+	switch resp[1] {
+	case 0x5a:
+		// request granted
+	case 0x5b:
+		err = errors.New("Socks connection request rejected or failed")
+	case 0x5c:
+		err = errors.New("Socks connection request request failed because client is not running identd (or not reachable from the server)")
+	case 0x5d:
+		err = errors.New("Socks connection request request failed because client's identd could not confirm the user ID in the request")
+	default:
+		err = errors.New("Socks connection request failed, unknown error")
+	}
+
+	return nil
+}