2021-07-18 16:09:09 +08:00
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package socks4
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import (
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"bytes"
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"encoding/binary"
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"errors"
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"io"
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"net"
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2022-04-20 01:52:51 +08:00
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"net/netip"
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2021-07-18 16:09:09 +08:00
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"strconv"
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2023-11-03 21:01:45 +08:00
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"github.com/metacubex/mihomo/component/auth"
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2021-07-18 16:09:09 +08:00
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)
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const Version = 0x04
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type Command = uint8
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const (
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CmdConnect Command = 0x01
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CmdBind Command = 0x02
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)
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type Code = uint8
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const (
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RequestGranted Code = 90
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RequestRejected Code = 91
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RequestIdentdFailed Code = 92
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RequestIdentdMismatched Code = 93
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)
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var (
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errVersionMismatched = errors.New("version code mismatched")
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errCommandNotSupported = errors.New("command not supported")
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errIPv6NotSupported = errors.New("IPv6 not supported")
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ErrRequestRejected = errors.New("request rejected or failed")
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ErrRequestIdentdFailed = errors.New("request rejected because SOCKS server cannot connect to identd on the client")
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ErrRequestIdentdMismatched = errors.New("request rejected because the client program and identd report different user-ids")
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ErrRequestUnknownCode = errors.New("request failed with unknown code")
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)
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2022-04-20 01:52:51 +08:00
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var subnet = netip.PrefixFrom(netip.IPv4Unspecified(), 24)
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2021-07-18 16:09:09 +08:00
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func ServerHandshake(rw io.ReadWriter, authenticator auth.Authenticator) (addr string, command Command, err error) {
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var req [8]byte
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if _, err = io.ReadFull(rw, req[:]); err != nil {
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return
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}
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if req[0] != Version {
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err = errVersionMismatched
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return
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}
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if command = req[1]; command != CmdConnect {
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err = errCommandNotSupported
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return
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}
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var (
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2022-04-20 01:52:51 +08:00
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dstIP = netip.AddrFrom4(*(*[4]byte)(req[4:8])) // [4]byte
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dstPort = req[2:4] // [2]byte
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2021-07-18 16:09:09 +08:00
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)
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var (
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host string
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port string
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code uint8
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userID []byte
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)
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if userID, err = readUntilNull(rw); err != nil {
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return
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}
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if isReservedIP(dstIP) {
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var target []byte
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if target, err = readUntilNull(rw); err != nil {
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return
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}
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host = string(target)
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}
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port = strconv.Itoa(int(binary.BigEndian.Uint16(dstPort)))
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if host != "" {
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addr = net.JoinHostPort(host, port)
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} else {
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2022-04-20 01:52:51 +08:00
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addr = net.JoinHostPort(dstIP.String(), port)
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2021-07-18 16:09:09 +08:00
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}
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// SOCKS4 only support USERID auth.
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if authenticator == nil || authenticator.Verify(string(userID), "") {
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code = RequestGranted
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} else {
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code = RequestIdentdMismatched
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2021-09-15 16:45:57 +08:00
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err = ErrRequestIdentdMismatched
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2021-07-18 16:09:09 +08:00
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}
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var reply [8]byte
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reply[0] = 0x00 // reply code
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reply[1] = code // result code
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2022-04-20 01:52:51 +08:00
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copy(reply[4:8], dstIP.AsSlice())
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2021-07-18 16:09:09 +08:00
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copy(reply[2:4], dstPort)
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2021-09-15 16:45:57 +08:00
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_, wErr := rw.Write(reply[:])
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if err == nil {
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err = wErr
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}
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2021-07-18 16:09:09 +08:00
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return
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}
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func ClientHandshake(rw io.ReadWriter, addr string, command Command, userID string) (err error) {
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host, portStr, err := net.SplitHostPort(addr)
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if err != nil {
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return err
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}
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port, err := strconv.ParseUint(portStr, 10, 16)
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if err != nil {
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return err
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}
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2022-04-20 01:52:51 +08:00
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dstIP, err := netip.ParseAddr(host)
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if err != nil /* HOST */ {
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dstIP = netip.AddrFrom4([4]byte{0, 0, 0, 1})
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} else if dstIP.Is6() /* IPv6 */ {
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2021-07-18 16:09:09 +08:00
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return errIPv6NotSupported
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}
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req := &bytes.Buffer{}
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req.WriteByte(Version)
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req.WriteByte(command)
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2022-04-20 01:52:51 +08:00
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_ = binary.Write(req, binary.BigEndian, uint16(port))
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req.Write(dstIP.AsSlice())
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2021-07-18 16:09:09 +08:00
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req.WriteString(userID)
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req.WriteByte(0) /* NULL */
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if isReservedIP(dstIP) /* SOCKS4A */ {
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req.WriteString(host)
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req.WriteByte(0) /* NULL */
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}
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if _, err = rw.Write(req.Bytes()); err != nil {
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return err
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}
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var resp [8]byte
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if _, err = io.ReadFull(rw, resp[:]); err != nil {
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return err
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}
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if resp[0] != 0x00 {
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return errVersionMismatched
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}
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switch resp[1] {
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case RequestGranted:
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return nil
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case RequestRejected:
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return ErrRequestRejected
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case RequestIdentdFailed:
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return ErrRequestIdentdFailed
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case RequestIdentdMismatched:
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return ErrRequestIdentdMismatched
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default:
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return ErrRequestUnknownCode
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}
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}
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// For version 4A, if the client cannot resolve the destination host's
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// domain name to find its IP address, it should set the first three bytes
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// of DSTIP to NULL and the last byte to a non-zero value. (This corresponds
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// to IP address 0.0.0.x, with x nonzero. As decreed by IANA -- The
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// Internet Assigned Numbers Authority -- such an address is inadmissible
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// as a destination IP address and thus should never occur if the client
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// can resolve the domain name.)
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2022-04-20 01:52:51 +08:00
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func isReservedIP(ip netip.Addr) bool {
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2021-07-18 16:09:09 +08:00
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return !ip.IsUnspecified() && subnet.Contains(ip)
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}
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func readUntilNull(r io.Reader) ([]byte, error) {
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2021-10-10 23:44:09 +08:00
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buf := &bytes.Buffer{}
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2021-07-18 16:09:09 +08:00
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var data [1]byte
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for {
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if _, err := r.Read(data[:]); err != nil {
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return nil, err
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}
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if data[0] == 0 {
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return buf.Bytes(), nil
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}
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buf.WriteByte(data[0])
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}
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}
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