package socks import ( "encoding/binary" "io" "github.com/xtls/xray-core/common" "github.com/xtls/xray-core/common/buf" "github.com/xtls/xray-core/common/net" "github.com/xtls/xray-core/common/protocol" ) const ( socks5Version = 0x05 socks4Version = 0x04 cmdTCPConnect = 0x01 cmdTCPBind = 0x02 cmdUDPAssociate = 0x03 cmdTorResolve = 0xF0 cmdTorResolvePTR = 0xF1 socks4RequestGranted = 90 socks4RequestRejected = 91 authNotRequired = 0x00 // authGssAPI = 0x01 authPassword = 0x02 authNoMatchingMethod = 0xFF statusSuccess = 0x00 statusCmdNotSupport = 0x07 ) var addrParser = protocol.NewAddressParser( protocol.AddressFamilyByte(0x01, net.AddressFamilyIPv4), protocol.AddressFamilyByte(0x04, net.AddressFamilyIPv6), protocol.AddressFamilyByte(0x03, net.AddressFamilyDomain), ) type ServerSession struct { config *ServerConfig address net.Address port net.Port localAddress net.Address } func (s *ServerSession) handshake4(cmd byte, reader io.Reader, writer io.Writer) (*protocol.RequestHeader, error) { if s.config.AuthType == AuthType_PASSWORD { writeSocks4Response(writer, socks4RequestRejected, net.AnyIP, net.Port(0)) return nil, newError("socks 4 is not allowed when auth is required.") } var port net.Port var address net.Address { buffer := buf.StackNew() if _, err := buffer.ReadFullFrom(reader, 6); err != nil { buffer.Release() return nil, newError("insufficient header").Base(err) } port = net.PortFromBytes(buffer.BytesRange(0, 2)) address = net.IPAddress(buffer.BytesRange(2, 6)) buffer.Release() } if _, err := ReadUntilNull(reader); /* user id */ err != nil { return nil, err } if address.IP()[0] == 0x00 { domain, err := ReadUntilNull(reader) if err != nil { return nil, newError("failed to read domain for socks 4a").Base(err) } address = net.DomainAddress(domain) } switch cmd { case cmdTCPConnect: request := &protocol.RequestHeader{ Command: protocol.RequestCommandTCP, Address: address, Port: port, Version: socks4Version, } if err := writeSocks4Response(writer, socks4RequestGranted, net.AnyIP, net.Port(0)); err != nil { return nil, err } return request, nil default: writeSocks4Response(writer, socks4RequestRejected, net.AnyIP, net.Port(0)) return nil, newError("unsupported command: ", cmd) } } func (s *ServerSession) auth5(nMethod byte, reader io.Reader, writer io.Writer) (username string, err error) { buffer := buf.StackNew() defer buffer.Release() if _, err = buffer.ReadFullFrom(reader, int32(nMethod)); err != nil { return "", newError("failed to read auth methods").Base(err) } var expectedAuth byte = authNotRequired if s.config.AuthType == AuthType_PASSWORD { expectedAuth = authPassword } if !hasAuthMethod(expectedAuth, buffer.BytesRange(0, int32(nMethod))) { writeSocks5AuthenticationResponse(writer, socks5Version, authNoMatchingMethod) return "", newError("no matching auth method") } if err := writeSocks5AuthenticationResponse(writer, socks5Version, expectedAuth); err != nil { return "", newError("failed to write auth response").Base(err) } if expectedAuth == authPassword { username, password, err := ReadUsernamePassword(reader) if err != nil { return "", newError("failed to read username and password for authentication").Base(err) } if !s.config.HasAccount(username, password) { writeSocks5AuthenticationResponse(writer, 0x01, 0xFF) return "", newError("invalid username or password") } if err := writeSocks5AuthenticationResponse(writer, 0x01, 0x00); err != nil { return "", newError("failed to write auth response").Base(err) } return username, nil } return "", nil } func (s *ServerSession) handshake5(nMethod byte, reader io.Reader, writer io.Writer) (*protocol.RequestHeader, error) { var ( username string err error ) if username, err = s.auth5(nMethod, reader, writer); err != nil { return nil, err } var cmd byte { buffer := buf.StackNew() if _, err := buffer.ReadFullFrom(reader, 3); err != nil { buffer.Release() return nil, newError("failed to read request").Base(err) } cmd = buffer.Byte(1) buffer.Release() } request := new(protocol.RequestHeader) if username != "" { request.User = &protocol.MemoryUser{Email: username} } switch cmd { case cmdTCPConnect, cmdTorResolve, cmdTorResolvePTR: // We don't have a solution for Tor case now. Simply treat it as connect command. request.Command = protocol.RequestCommandTCP case cmdUDPAssociate: if !s.config.UdpEnabled { writeSocks5Response(writer, statusCmdNotSupport, net.AnyIP, net.Port(0)) return nil, newError("UDP is not enabled.") } request.Command = protocol.RequestCommandUDP case cmdTCPBind: writeSocks5Response(writer, statusCmdNotSupport, net.AnyIP, net.Port(0)) return nil, newError("TCP bind is not supported.") default: writeSocks5Response(writer, statusCmdNotSupport, net.AnyIP, net.Port(0)) return nil, newError("unknown command ", cmd) } request.Version = socks5Version addr, port, err := addrParser.ReadAddressPort(nil, reader) if err != nil { return nil, newError("failed to read address").Base(err) } request.Address = addr request.Port = port responseAddress := s.address responsePort := s.port //nolint:gocritic // Use if else chain for clarity if request.Command == protocol.RequestCommandUDP { if s.config.Address != nil { // Use configured IP as remote address in the response to UDP Associate responseAddress = s.config.Address.AsAddress() } else { // Use conn.LocalAddr() IP as remote address in the response by default responseAddress = s.localAddress } } if err := writeSocks5Response(writer, statusSuccess, responseAddress, responsePort); err != nil { return nil, err } return request, nil } // Handshake performs a Socks4/4a/5 handshake. func (s *ServerSession) Handshake(reader io.Reader, writer io.Writer) (*protocol.RequestHeader, error) { buffer := buf.StackNew() if _, err := buffer.ReadFullFrom(reader, 2); err != nil { buffer.Release() return nil, newError("insufficient header").Base(err) } version := buffer.Byte(0) cmd := buffer.Byte(1) buffer.Release() switch version { case socks4Version: return s.handshake4(cmd, reader, writer) case socks5Version: return s.handshake5(cmd, reader, writer) default: return nil, newError("unknown Socks version: ", version) } } // ReadUsernamePassword reads Socks 5 username/password message from the given reader. // +----+------+----------+------+----------+ // |VER | ULEN | UNAME | PLEN | PASSWD | // +----+------+----------+------+----------+ // | 1 | 1 | 1 to 255 | 1 | 1 to 255 | // +----+------+----------+------+----------+ func ReadUsernamePassword(reader io.Reader) (string, string, error) { buffer := buf.StackNew() defer buffer.Release() if _, err := buffer.ReadFullFrom(reader, 2); err != nil { return "", "", err } nUsername := int32(buffer.Byte(1)) buffer.Clear() if _, err := buffer.ReadFullFrom(reader, nUsername); err != nil { return "", "", err } username := buffer.String() buffer.Clear() if _, err := buffer.ReadFullFrom(reader, 1); err != nil { return "", "", err } nPassword := int32(buffer.Byte(0)) buffer.Clear() if _, err := buffer.ReadFullFrom(reader, nPassword); err != nil { return "", "", err } password := buffer.String() return username, password, nil } // ReadUntilNull reads content from given reader, until a null (0x00) byte. func ReadUntilNull(reader io.Reader) (string, error) { b := buf.StackNew() defer b.Release() for { _, err := b.ReadFullFrom(reader, 1) if err != nil { return "", err } if b.Byte(b.Len()-1) == 0x00 { b.Resize(0, b.Len()-1) return b.String(), nil } if b.IsFull() { return "", newError("buffer overrun") } } } func hasAuthMethod(expectedAuth byte, authCandidates []byte) bool { for _, a := range authCandidates { if a == expectedAuth { return true } } return false } func writeSocks5AuthenticationResponse(writer io.Writer, version byte, auth byte) error { return buf.WriteAllBytes(writer, []byte{version, auth}) } func writeSocks5Response(writer io.Writer, errCode byte, address net.Address, port net.Port) error { buffer := buf.New() defer buffer.Release() common.Must2(buffer.Write([]byte{socks5Version, errCode, 0x00 /* reserved */})) if err := addrParser.WriteAddressPort(buffer, address, port); err != nil { return err } return buf.WriteAllBytes(writer, buffer.Bytes()) } func writeSocks4Response(writer io.Writer, errCode byte, address net.Address, port net.Port) error { buffer := buf.StackNew() defer buffer.Release() common.Must(buffer.WriteByte(0x00)) common.Must(buffer.WriteByte(errCode)) portBytes := buffer.Extend(2) binary.BigEndian.PutUint16(portBytes, port.Value()) common.Must2(buffer.Write(address.IP())) return buf.WriteAllBytes(writer, buffer.Bytes()) } func DecodeUDPPacket(packet *buf.Buffer) (*protocol.RequestHeader, error) { if packet.Len() < 5 { return nil, newError("insufficient length of packet.") } request := &protocol.RequestHeader{ Version: socks5Version, Command: protocol.RequestCommandUDP, } // packet[0] and packet[1] are reserved if packet.Byte(2) != 0 /* fragments */ { return nil, newError("discarding fragmented payload.") } packet.Advance(3) addr, port, err := addrParser.ReadAddressPort(nil, packet) if err != nil { return nil, newError("failed to read UDP header").Base(err) } request.Address = addr request.Port = port return request, nil } func EncodeUDPPacket(request *protocol.RequestHeader, data []byte) (*buf.Buffer, error) { b := buf.New() common.Must2(b.Write([]byte{0, 0, 0 /* Fragment */})) if err := addrParser.WriteAddressPort(b, request.Address, request.Port); err != nil { b.Release() return nil, err } common.Must2(b.Write(data)) return b, nil } type UDPReader struct { Reader io.Reader } func (r *UDPReader) ReadMultiBuffer() (buf.MultiBuffer, error) { buffer := buf.New() _, err := buffer.ReadFrom(r.Reader) if err != nil { buffer.Release() return nil, err } u, err := DecodeUDPPacket(buffer) if err != nil { buffer.Release() return nil, err } dest := u.Destination() buffer.UDP = &dest return buf.MultiBuffer{buffer}, nil } type UDPWriter struct { Writer io.Writer Request *protocol.RequestHeader } func (w *UDPWriter) WriteMultiBuffer(mb buf.MultiBuffer) error { for { mb2, b := buf.SplitFirst(mb) mb = mb2 if b == nil { break } request := w.Request if b.UDP != nil { request = &protocol.RequestHeader{ Address: b.UDP.Address, Port: b.UDP.Port, } } packet, err := EncodeUDPPacket(request, b.Bytes()) b.Release() if err != nil { buf.ReleaseMulti(mb) return err } _, err = w.Writer.Write(packet.Bytes()) packet.Release() if err != nil { buf.ReleaseMulti(mb) return err } } return nil } func ClientHandshake(request *protocol.RequestHeader, reader io.Reader, writer io.Writer) (*protocol.RequestHeader, error) { authByte := byte(authNotRequired) if request.User != nil { authByte = byte(authPassword) } b := buf.New() defer b.Release() common.Must2(b.Write([]byte{socks5Version, 0x01, authByte})) if authByte == authPassword { account := request.User.Account.(*Account) common.Must(b.WriteByte(0x01)) common.Must(b.WriteByte(byte(len(account.Username)))) common.Must2(b.WriteString(account.Username)) common.Must(b.WriteByte(byte(len(account.Password)))) common.Must2(b.WriteString(account.Password)) } if err := buf.WriteAllBytes(writer, b.Bytes()); err != nil { return nil, err } b.Clear() if _, err := b.ReadFullFrom(reader, 2); err != nil { return nil, err } if b.Byte(0) != socks5Version { return nil, newError("unexpected server version: ", b.Byte(0)).AtWarning() } if b.Byte(1) != authByte { return nil, newError("auth method not supported.").AtWarning() } if authByte == authPassword { b.Clear() if _, err := b.ReadFullFrom(reader, 2); err != nil { return nil, err } if b.Byte(1) != 0x00 { return nil, newError("server rejects account: ", b.Byte(1)) } } b.Clear() command := byte(cmdTCPConnect) if request.Command == protocol.RequestCommandUDP { command = byte(cmdUDPAssociate) } common.Must2(b.Write([]byte{socks5Version, command, 0x00 /* reserved */})) if err := addrParser.WriteAddressPort(b, request.Address, request.Port); err != nil { return nil, err } if err := buf.WriteAllBytes(writer, b.Bytes()); err != nil { return nil, err } b.Clear() if _, err := b.ReadFullFrom(reader, 3); err != nil { return nil, err } resp := b.Byte(1) if resp != 0x00 { return nil, newError("server rejects request: ", resp) } b.Clear() address, port, err := addrParser.ReadAddressPort(b, reader) if err != nil { return nil, err } if request.Command == protocol.RequestCommandUDP { udpRequest := &protocol.RequestHeader{ Version: socks5Version, Command: protocol.RequestCommandUDP, Address: address, Port: port, } return udpRequest, nil } return nil, nil }