/
socks5.go
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/
socks5.go
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package socks5
import (
"bytes"
"encoding/binary"
"errors"
"io"
"net"
"net/netip"
"strconv"
"github.com/0xObjc/clash/component/auth"
"github.com/Dreamacro/protobytes"
)
// 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
const Version = 5
// 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
// MaxAuthLen is the maximum size of user/password field in SOCKS5 Auth
const MaxAuthLen = 255
// Addr represents a SOCKS address as defined in RFC 1928 section 5.
type Addr []byte
func (a Addr) String() string {
var host, port string
switch a[0] {
case AtypDomainName:
hostLen := uint16(a[1])
host = string(a[2 : 2+hostLen])
port = strconv.Itoa((int(a[2+hostLen]) << 8) | int(a[2+hostLen+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)
}
// UDPAddr converts a socks5.Addr to *net.UDPAddr
func (a Addr) UDPAddr() *net.UDPAddr {
if len(a) == 0 {
return nil
}
switch a[0] {
case AtypIPv4:
var ip [net.IPv4len]byte
copy(ip[0:], a[1:1+net.IPv4len])
return &net.UDPAddr{IP: net.IP(ip[:]), Port: int(binary.BigEndian.Uint16(a[1+net.IPv4len : 1+net.IPv4len+2]))}
case AtypIPv6:
var ip [net.IPv6len]byte
copy(ip[0:], a[1:1+net.IPv6len])
return &net.UDPAddr{IP: net.IP(ip[:]), Port: int(binary.BigEndian.Uint16(a[1+net.IPv6len : 1+net.IPv6len+2]))}
}
// Other Atyp
return nil
}
// 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)
)
// Auth errors used to return a specific "Auth failed" error
var ErrAuth = errors.New("auth failed")
type User struct {
Username string
Password string
}
// ServerHandshake fast-tracks SOCKS initialization to get target address to connect on server side.
func ServerHandshake(rw net.Conn, authenticator auth.Authenticator) (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 authenticator != nil {
if _, err = rw.Write([]byte{5, 2}); err != nil {
return
}
// Get header
header := make([]byte, 2)
if _, err = io.ReadFull(rw, header); err != nil {
return
}
authBuf := make([]byte, MaxAuthLen)
// Get username
userLen := int(header[1])
if userLen <= 0 {
rw.Write([]byte{1, 1})
err = ErrAuth
return
}
if _, err = io.ReadFull(rw, authBuf[:userLen]); err != nil {
return
}
user := string(authBuf[:userLen])
// Get password
if _, err = rw.Read(header[:1]); err != nil {
return
}
passLen := int(header[0])
if passLen <= 0 {
rw.Write([]byte{1, 1})
err = ErrAuth
return
}
if _, err = io.ReadFull(rw, authBuf[:passLen]); err != nil {
return
}
pass := string(authBuf[:passLen])
// Verify
if ok := authenticator.Verify(user, pass); !ok {
rw.Write([]byte{1, 1})
err = ErrAuth
return
}
// Response auth state
if _, err = rw.Write([]byte{1, 0}); err != nil {
return
}
} else {
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
}
command = buf[1]
addr, err = ReadAddr(rw, buf)
if err != nil {
return
}
switch command {
case CmdConnect, CmdUDPAssociate:
// Acquire server listened address info
localAddr := ParseAddr(rw.LocalAddr().String())
if localAddr == nil {
err = ErrAddressNotSupported
} else {
// write VER REP RSV ATYP BND.ADDR BND.PORT
_, err = rw.Write(bytes.Join([][]byte{{5, 0, 0}, localAddr}, []byte{}))
}
case CmdBind:
fallthrough
default:
err = ErrCommandNotSupported
}
return
}
// ClientHandshake fast-tracks SOCKS initialization to get target address to connect on client side.
func ClientHandshake(rw io.ReadWriter, addr Addr, command Command, user *User) (Addr, 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 nil, err
}
// VER, METHOD
if _, err := io.ReadFull(rw, buf[:2]); err != nil {
return nil, err
}
if buf[0] != 5 {
return nil, errors.New("SOCKS version error")
}
if buf[1] == 2 {
if user == nil {
return nil, ErrAuth
}
// password protocol version
authMsg := protobytes.BytesWriter{}
authMsg.PutUint8(1)
authMsg.PutUint8(uint8(len(user.Username)))
authMsg.PutString(user.Username)
authMsg.PutUint8(uint8(len(user.Password)))
authMsg.PutString(user.Password)
if _, err := rw.Write(authMsg.Bytes()); err != nil {
return nil, err
}
if _, err := io.ReadFull(rw, buf[:2]); err != nil {
return nil, err
}
if buf[1] != 0 {
return nil, errors.New("rejected username/password")
}
} else if buf[1] != 0 {
return nil, errors.New("SOCKS need auth")
}
// VER, CMD, RSV, ADDR
if _, err := rw.Write(bytes.Join([][]byte{{5, command, 0}, addr}, []byte{})); err != nil {
return nil, err
}
// VER, REP, RSV
if _, err := io.ReadFull(rw, buf[:3]); err != nil {
return nil, err
}
return ReadAddr(rw, buf)
}
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
}
domainLength := uint16(b[1])
_, err = io.ReadFull(r, b[2:2+domainLength+2])
return b[:1+1+domainLength+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 {
buf := protobytes.BytesWriter{}
host, port, err := net.SplitHostPort(s)
if err != nil {
return nil
}
if ip := net.ParseIP(host); ip != nil {
if ip4 := ip.To4(); ip4 != nil {
buf.PutUint8(AtypIPv4)
buf.PutSlice(ip4)
} else {
buf.PutUint8(AtypIPv6)
buf.PutSlice(ip)
}
} else {
if len(host) > 255 {
return nil
}
buf.PutUint8(AtypDomainName)
buf.PutUint8(byte(len(host)))
buf.PutString(host)
}
portnum, err := strconv.ParseUint(port, 10, 16)
if err != nil {
return nil
}
buf.PutUint16be(uint16(portnum))
return Addr(buf.Bytes())
}
// ParseAddrToSocksAddr parse a socks addr from net.addr
// This is a fast path of ParseAddr(addr.String())
func ParseAddrToSocksAddr(addr net.Addr) Addr {
var hostip net.IP
var port int
if udpaddr, ok := addr.(*net.UDPAddr); ok {
hostip = udpaddr.IP
port = udpaddr.Port
} else if tcpaddr, ok := addr.(*net.TCPAddr); ok {
hostip = tcpaddr.IP
port = tcpaddr.Port
}
// fallback parse
if hostip == nil {
return ParseAddr(addr.String())
}
var parsed protobytes.BytesWriter
if ip4 := hostip.To4(); ip4.DefaultMask() != nil {
parsed = make([]byte, 0, 1+net.IPv4len+2)
parsed.PutUint8(AtypIPv4)
parsed.PutSlice(ip4)
parsed.PutUint16be(uint16(port))
} else {
parsed = make([]byte, 0, 1+net.IPv6len+2)
parsed.PutUint8(AtypIPv6)
parsed.PutSlice(hostip)
parsed.PutUint16be(uint16(port))
}
return Addr(parsed)
}
func AddrFromStdAddrPort(addrPort netip.AddrPort) Addr {
addr := addrPort.Addr()
if addr.Is4() {
ip4 := addr.As4()
return []byte{AtypIPv4, ip4[0], ip4[1], ip4[2], ip4[3], byte(addrPort.Port() >> 8), byte(addrPort.Port())}
}
buf := make([]byte, 1+net.IPv6len+2)
buf[0] = AtypIPv6
copy(buf[1:], addr.AsSlice())
buf[1+net.IPv6len] = byte(addrPort.Port() >> 8)
buf[1+net.IPv6len+1] = byte(addrPort.Port())
return buf
}
// DecodeUDPPacket split `packet` to addr payload, and this function is mutable with `packet`
func DecodeUDPPacket(packet []byte) (addr Addr, payload []byte, err error) {
r := protobytes.BytesReader(packet)
if r.Len() < 5 {
err = errors.New("insufficient length of packet")
return
}
// packet[0] and packet[1] are reserved
reserved, r := r.SplitAt(2)
if !bytes.Equal(reserved, []byte{0, 0}) {
err = errors.New("reserved fields should be zero")
return
}
if r.ReadUint8() != 0 /* fragments */ {
err = errors.New("discarding fragmented payload")
return
}
addr = SplitAddr(r)
if addr == nil {
err = errors.New("failed to read UDP header")
}
_, payload = r.SplitAt(len(addr))
return
}
func EncodeUDPPacket(addr Addr, payload []byte) (packet []byte, err error) {
if addr == nil {
err = errors.New("address is invalid")
return
}
w := protobytes.BytesWriter{}
w.PutSlice([]byte{0, 0, 0})
w.PutSlice(addr)
w.PutSlice(payload)
packet = w.Bytes()
return
}