clone from danieldin95

vendor/github.com/shadowsocks/go-shadowsocks2/socks/socks.go

@@ -0,0 +1,214 @@
+// Package socks implements essential parts of SOCKS protocol.
+package socks
+
+import (
+	"io"
+	"net"
+	"strconv"
+)
+
+// UDPEnabled is the toggle for UDP support
+var UDPEnabled = false
+
+// SOCKS request commands as defined in RFC 1928 section 4.
+const (
+	CmdConnect      = 1
+	CmdBind         = 2
+	CmdUDPAssociate = 3
+)
+
+// SOCKS address types as defined in RFC 1928 section 5.
+const (
+	AtypIPv4       = 1
+	AtypDomainName = 3
+	AtypIPv6       = 4
+)
+
+// Error represents a SOCKS error
+type Error byte
+
+func (err Error) Error() string {
+	return "SOCKS error: " + strconv.Itoa(int(err))
+}
+
+// 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)
+	InfoUDPAssociate        = Error(9)
+)
+
+// 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
+
+// String serializes SOCKS address a to string form.
+func (a Addr) String() string {
+	var host, port string
+
+	switch a[0] { // address type
+	case AtypDomainName:
+		host = string(a[2 : 2+int(a[1])])
+		port = strconv.Itoa((int(a[2+int(a[1])]) << 8) | int(a[2+int(a[1])+1]))
+	case AtypIPv4:
+		host = net.IP(a[1 : 1+net.IPv4len]).String()
+		port = strconv.Itoa((int(a[1+net.IPv4len]) << 8) | int(a[1+net.IPv4len+1]))
+	case AtypIPv6:
+		host = net.IP(a[1 : 1+net.IPv6len]).String()
+		port = strconv.Itoa((int(a[1+net.IPv6len]) << 8) | int(a[1+net.IPv6len+1]))
+	}
+
+	return net.JoinHostPort(host, port)
+}
+
+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+int(b[1])+2])
+		return b[:1+1+int(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
+}
+
+// ReadAddr reads just enough bytes from r to get a valid Addr.
+func ReadAddr(r io.Reader) (Addr, error) {
+	return readAddr(r, make([]byte, MaxAddrLen))
+}
+
+// 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
+}
+
+// Handshake fast-tracks SOCKS initialization to get target address to connect.
+func Handshake(rw io.ReadWriter) (Addr, 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 nil, err
+	}
+	nmethods := buf[1]
+	if _, err := io.ReadFull(rw, buf[:nmethods]); err != nil {
+		return nil, err
+	}
+	// write VER METHOD
+	if _, err := rw.Write([]byte{5, 0}); err != nil {
+		return nil, err
+	}
+	// read VER CMD RSV ATYP DST.ADDR DST.PORT
+	if _, err := io.ReadFull(rw, buf[:3]); err != nil {
+		return nil, err
+	}
+	cmd := buf[1]
+	addr, err := readAddr(rw, buf)
+	if err != nil {
+		return nil, err
+	}
+	switch cmd {
+	case CmdConnect:
+		_, err = rw.Write([]byte{5, 0, 0, 1, 0, 0, 0, 0, 0, 0}) // SOCKS v5, reply succeeded
+	case CmdUDPAssociate:
+		if !UDPEnabled {
+			return nil, ErrCommandNotSupported
+		}
+		listenAddr := ParseAddr(rw.(net.Conn).LocalAddr().String())
+		_, err = rw.Write(append([]byte{5, 0, 0}, listenAddr...)) // SOCKS v5, reply succeeded
+		if err != nil {
+			return nil, ErrCommandNotSupported
+		}
+		err = InfoUDPAssociate
+	default:
+		return nil, ErrCommandNotSupported
+	}
+
+	return addr, err // skip VER, CMD, RSV fields
+}