Feature: support outbound socks5 udp

component/socks5/socks5.go

@@ -0,0 +1,246 @@
+package socks5
+
+import (
+	"bytes"
+	"errors"
+	"io"
+	"net"
+	"strconv"
+)
+
+// Error represents a SOCKS error
+type Error byte
+
+func (err Error) Error() string {
+	return "SOCKS error: " + strconv.Itoa(int(err))
+}
+
+// Command is request commands as defined in RFC 1928 section 4.
+type Command = uint8
+
+// SOCKS request commands as defined in RFC 1928 section 4.
+const (
+	CmdConnect      Command = 1
+	CmdBind         Command = 2
+	CmdUDPAssociate Command = 3
+)
+
+// SOCKS address types as defined in RFC 1928 section 5.
+const (
+	AtypIPv4       = 1
+	AtypDomainName = 3
+	AtypIPv6       = 4
+)
+
+// MaxAddrLen is the maximum size of SOCKS address in bytes.
+const MaxAddrLen = 1 + 1 + 255 + 2
+
+// Addr represents a SOCKS address as defined in RFC 1928 section 5.
+type Addr = []byte
+
+// SOCKS errors as defined in RFC 1928 section 6.
+const (
+	ErrGeneralFailure       = Error(1)
+	ErrConnectionNotAllowed = Error(2)
+	ErrNetworkUnreachable   = Error(3)
+	ErrHostUnreachable      = Error(4)
+	ErrConnectionRefused    = Error(5)
+	ErrTTLExpired           = Error(6)
+	ErrCommandNotSupported  = Error(7)
+	ErrAddressNotSupported  = Error(8)
+)
+
+type User struct {
+	Username string
+	Password string
+}
+
+// ServerHandshake fast-tracks SOCKS initialization to get target address to connect on server side.
+func ServerHandshake(rw io.ReadWriter) (addr Addr, command Command, err error) {
+	// Read RFC 1928 for request and reply structure and sizes.
+	buf := make([]byte, MaxAddrLen)
+	// read VER, NMETHODS, METHODS
+	if _, err = io.ReadFull(rw, buf[:2]); err != nil {
+		return
+	}
+	nmethods := buf[1]
+	if _, err = io.ReadFull(rw, buf[:nmethods]); err != nil {
+		return
+	}
+	// write VER METHOD
+	if _, err = rw.Write([]byte{5, 0}); err != nil {
+		return
+	}
+	// read VER CMD RSV ATYP DST.ADDR DST.PORT
+	if _, err = io.ReadFull(rw, buf[:3]); err != nil {
+		return
+	}
+
+	if buf[1] != CmdConnect && buf[1] != CmdUDPAssociate {
+		err = ErrCommandNotSupported
+		return
+	}
+
+	command = buf[1]
+	addr, err = readAddr(rw, buf)
+	if err != nil {
+		return
+	}
+	// write VER REP RSV ATYP BND.ADDR BND.PORT
+	_, err = rw.Write([]byte{5, 0, 0, 1, 0, 0, 0, 0, 0, 0})
+	return
+}
+
+// ClientHandshake fast-tracks SOCKS initialization to get target address to connect on client side.
+func ClientHandshake(rw io.ReadWriter, addr Addr, cammand Command, user *User) error {
+	buf := make([]byte, MaxAddrLen)
+	var err error
+
+	// VER, NMETHODS, METHODS
+	if user != nil {
+		_, err = rw.Write([]byte{5, 1, 2})
+	} else {
+		_, err = rw.Write([]byte{5, 1, 0})
+	}
+	if err != nil {
+		return err
+	}
+
+	// VER, METHOD
+	if _, err := io.ReadFull(rw, buf[:2]); err != nil {
+		return err
+	}
+
+	if buf[0] != 5 {
+		return errors.New("SOCKS version error")
+	}
+
+	if buf[1] == 2 {
+		// password protocol version
+		authMsg := &bytes.Buffer{}
+		authMsg.WriteByte(1)
+		authMsg.WriteByte(uint8(len(user.Username)))
+		authMsg.WriteString(user.Username)
+		authMsg.WriteByte(uint8(len(user.Password)))
+		authMsg.WriteString(user.Password)
+
+		if _, err := rw.Write(authMsg.Bytes()); err != nil {
+			return err
+		}
+
+		if _, err := io.ReadFull(rw, buf[:2]); err != nil {
+			return err
+		}
+
+		if buf[1] != 0 {
+			return errors.New("rejected username/password")
+		}
+	} else if buf[1] != 0 {
+		return errors.New("SOCKS need auth")
+	}
+
+	// VER, CMD, RSV, ADDR
+	if _, err := rw.Write(bytes.Join([][]byte{{5, cammand, 0}, addr}, []byte(""))); err != nil {
+		return err
+	}
+
+	if _, err := io.ReadFull(rw, buf[:10]); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func readAddr(r io.Reader, b []byte) (Addr, error) {
+	if len(b) < MaxAddrLen {
+		return nil, io.ErrShortBuffer
+	}
+	_, err := io.ReadFull(r, b[:1]) // read 1st byte for address type
+	if err != nil {
+		return nil, err
+	}
+
+	switch b[0] {
+	case AtypDomainName:
+		_, err = io.ReadFull(r, b[1:2]) // read 2nd byte for domain length
+		if err != nil {
+			return nil, err
+		}
+		_, err = io.ReadFull(r, b[2:2+b[1]+2])
+		return b[:1+1+b[1]+2], err
+	case AtypIPv4:
+		_, err = io.ReadFull(r, b[1:1+net.IPv4len+2])
+		return b[:1+net.IPv4len+2], err
+	case AtypIPv6:
+		_, err = io.ReadFull(r, b[1:1+net.IPv6len+2])
+		return b[:1+net.IPv6len+2], err
+	}
+
+	return nil, ErrAddressNotSupported
+}
+
+// SplitAddr slices a SOCKS address from beginning of b. Returns nil if failed.
+func SplitAddr(b []byte) Addr {
+	addrLen := 1
+	if len(b) < addrLen {
+		return nil
+	}
+
+	switch b[0] {
+	case AtypDomainName:
+		if len(b) < 2 {
+			return nil
+		}
+		addrLen = 1 + 1 + int(b[1]) + 2
+	case AtypIPv4:
+		addrLen = 1 + net.IPv4len + 2
+	case AtypIPv6:
+		addrLen = 1 + net.IPv6len + 2
+	default:
+		return nil
+
+	}
+
+	if len(b) < addrLen {
+		return nil
+	}
+
+	return b[:addrLen]
+}
+
+// ParseAddr parses the address in string s. Returns nil if failed.
+func ParseAddr(s string) Addr {
+	var addr Addr
+	host, port, err := net.SplitHostPort(s)
+	if err != nil {
+		return nil
+	}
+	if ip := net.ParseIP(host); ip != nil {
+		if ip4 := ip.To4(); ip4 != nil {
+			addr = make([]byte, 1+net.IPv4len+2)
+			addr[0] = AtypIPv4
+			copy(addr[1:], ip4)
+		} else {
+			addr = make([]byte, 1+net.IPv6len+2)
+			addr[0] = AtypIPv6
+			copy(addr[1:], ip)
+		}
+	} else {
+		if len(host) > 255 {
+			return nil
+		}
+		addr = make([]byte, 1+1+len(host)+2)
+		addr[0] = AtypDomainName
+		addr[1] = byte(len(host))
+		copy(addr[2:], host)
+	}
+
+	portnum, err := strconv.ParseUint(port, 10, 16)
+	if err != nil {
+		return nil
+	}
+
+	addr[len(addr)-2], addr[len(addr)-1] = byte(portnum>>8), byte(portnum)
+
+	return addr
+}