loop-uh
d5a4715771
Some checks failed
Windows project source guards / test (push) Has been cancelled
341 lines
9 KiB
Go
341 lines
9 KiB
Go
package main
|
|
|
|
import (
|
|
"context"
|
|
"crypto/subtle"
|
|
"encoding/binary"
|
|
"errors"
|
|
"fmt"
|
|
"io"
|
|
"net"
|
|
"net/netip"
|
|
"sync"
|
|
"time"
|
|
)
|
|
|
|
type relay struct {
|
|
username, password string
|
|
journal *journal
|
|
dialTCP func(context.Context, netip.AddrPort) (net.Conn, error)
|
|
dialUDP func(netip.AddrPort) (net.Conn, error)
|
|
lookup func(context.Context, string) ([]netip.Addr, error)
|
|
}
|
|
|
|
func (s *relay) serve(ctx context.Context, listener net.Listener) error {
|
|
ctx, cancel := context.WithCancel(ctx)
|
|
defer listener.Close()
|
|
var wg sync.WaitGroup
|
|
defer wg.Wait()
|
|
// Cancel clients before waiting, including on an unexpected Accept error.
|
|
defer cancel()
|
|
stop := context.AfterFunc(ctx, func() { listener.Close() })
|
|
defer stop()
|
|
limit := make(chan struct{}, 256)
|
|
for {
|
|
client, err := listener.Accept()
|
|
if err != nil {
|
|
if ctx.Err() != nil {
|
|
return nil
|
|
}
|
|
return err
|
|
}
|
|
select {
|
|
case limit <- struct{}{}:
|
|
wg.Add(1)
|
|
go func() {
|
|
defer wg.Done()
|
|
defer func() { <-limit }()
|
|
defer client.Close()
|
|
stop := context.AfterFunc(ctx, func() { client.Close() })
|
|
defer stop()
|
|
if err := s.handle(ctx, client); err != nil && ctx.Err() == nil && !errors.Is(err, io.EOF) && !errors.Is(err, net.ErrClosed) {
|
|
s.journal.emit("relay_connection", err.Error(), nil)
|
|
}
|
|
}()
|
|
default:
|
|
client.Close()
|
|
}
|
|
}
|
|
}
|
|
|
|
func (s *relay) authenticate(c net.Conn) error {
|
|
var header [2]byte
|
|
if _, err := io.ReadFull(c, header[:]); err != nil {
|
|
return err
|
|
}
|
|
if header[0] != 5 || header[1] == 0 {
|
|
return fmt.Errorf("invalid SOCKS greeting")
|
|
}
|
|
methods := make([]byte, int(header[1]))
|
|
if _, err := io.ReadFull(c, methods); err != nil {
|
|
return err
|
|
}
|
|
found := false
|
|
for _, method := range methods {
|
|
found = found || method == 2
|
|
}
|
|
if !found {
|
|
_, _ = c.Write([]byte{5, 255})
|
|
return fmt.Errorf("SOCKS username/password authentication required")
|
|
}
|
|
if _, err := c.Write([]byte{5, 2}); err != nil {
|
|
return err
|
|
}
|
|
if _, err := io.ReadFull(c, header[:]); err != nil {
|
|
return err
|
|
}
|
|
if header[0] != 1 || header[1] == 0 {
|
|
return fmt.Errorf("invalid SOCKS authentication")
|
|
}
|
|
username := make([]byte, int(header[1]))
|
|
if _, err := io.ReadFull(c, username); err != nil {
|
|
return err
|
|
}
|
|
var length [1]byte
|
|
if _, err := io.ReadFull(c, length[:]); err != nil {
|
|
return err
|
|
}
|
|
password := make([]byte, int(length[0]))
|
|
if _, err := io.ReadFull(c, password); err != nil {
|
|
return err
|
|
}
|
|
ok := subtle.ConstantTimeCompare(username, []byte(s.username)) & subtle.ConstantTimeCompare(password, []byte(s.password))
|
|
status := byte(1)
|
|
if ok == 1 {
|
|
status = 0
|
|
}
|
|
if _, err := c.Write([]byte{1, status}); err != nil {
|
|
return err
|
|
}
|
|
if status != 0 {
|
|
return fmt.Errorf("SOCKS authentication rejected")
|
|
}
|
|
return nil
|
|
}
|
|
|
|
// Domain names are deliberately rejected: the front owns DNS. This avoids a
|
|
// second resolver and a hidden direct lookup path inside the protocol backend.
|
|
func readAddress(r io.Reader) (netip.AddrPort, error) {
|
|
var kind [1]byte
|
|
if _, err := io.ReadFull(r, kind[:]); err != nil {
|
|
return netip.AddrPort{}, err
|
|
}
|
|
n := 0
|
|
switch kind[0] {
|
|
case 1:
|
|
n = 4
|
|
case 4:
|
|
n = 16
|
|
default:
|
|
return netip.AddrPort{}, fmt.Errorf("SOCKS destination must be a resolved IP")
|
|
}
|
|
data := make([]byte, n+2)
|
|
if _, err := io.ReadFull(r, data); err != nil {
|
|
return netip.AddrPort{}, err
|
|
}
|
|
ip, _ := netip.AddrFromSlice(data[:n])
|
|
return netip.AddrPortFrom(ip.Unmap(), binary.BigEndian.Uint16(data[n:])), nil
|
|
}
|
|
|
|
func addressBytes(address netip.AddrPort) []byte {
|
|
kind := byte(4)
|
|
if address.Addr().Is4() {
|
|
kind = 1
|
|
}
|
|
data := append([]byte{kind}, address.Addr().AsSlice()...)
|
|
return binary.BigEndian.AppendUint16(data, address.Port())
|
|
}
|
|
|
|
func reply(c net.Conn, status byte, address netip.AddrPort) error {
|
|
_, err := c.Write(append([]byte{5, status, 0}, addressBytes(address)...))
|
|
return err
|
|
}
|
|
|
|
var emptyAddress = netip.MustParseAddrPort("0.0.0.0:0")
|
|
|
|
func (s *relay) handle(ctx context.Context, client net.Conn) error {
|
|
_ = client.SetDeadline(time.Now().Add(10 * time.Second))
|
|
if err := s.authenticate(client); err != nil {
|
|
return err
|
|
}
|
|
var request [3]byte
|
|
if _, err := io.ReadFull(client, request[:]); err != nil {
|
|
return err
|
|
}
|
|
if request[0] != 5 || request[2] != 0 {
|
|
return fmt.Errorf("invalid SOCKS request")
|
|
}
|
|
target, err := readDestination(client)
|
|
if err != nil {
|
|
_ = reply(client, 8, emptyAddress)
|
|
return err
|
|
}
|
|
switch request[1] {
|
|
case 1:
|
|
addresses, err := s.resolveDestination(ctx, target)
|
|
if err != nil {
|
|
_ = reply(client, 4, emptyAddress)
|
|
return err
|
|
}
|
|
dst := addresses[0]
|
|
if dst.Port() == 0 || dst.Addr().IsUnspecified() || dst.Addr().IsMulticast() {
|
|
_ = reply(client, 8, emptyAddress)
|
|
return fmt.Errorf("invalid TCP destination")
|
|
}
|
|
dialCtx, cancel := context.WithTimeout(ctx, 15*time.Second)
|
|
defer cancel()
|
|
var remote net.Conn
|
|
for _, address := range addresses {
|
|
remote, err = s.dialTCP(dialCtx, address)
|
|
if err == nil {
|
|
break
|
|
}
|
|
}
|
|
if err != nil {
|
|
_ = reply(client, 5, emptyAddress)
|
|
return fmt.Errorf("TCP %s: %w", dst, err)
|
|
}
|
|
defer remote.Close()
|
|
if err := reply(client, 0, emptyAddress); err != nil {
|
|
return err
|
|
}
|
|
_ = client.SetDeadline(time.Time{})
|
|
done := make(chan struct{})
|
|
go func() { _, _ = io.Copy(remote, client); remote.Close(); close(done) }()
|
|
_, err = io.Copy(client, remote)
|
|
client.Close()
|
|
remote.Close()
|
|
<-done
|
|
return err
|
|
case 3:
|
|
_ = client.SetDeadline(time.Time{})
|
|
return s.associate(ctx, client)
|
|
default:
|
|
_ = reply(client, 7, emptyAddress)
|
|
return fmt.Errorf("unsupported SOCKS command %d", request[1])
|
|
}
|
|
}
|
|
|
|
func (s *relay) associate(ctx context.Context, control net.Conn) error {
|
|
peer := control.RemoteAddr().(*net.TCPAddr).AddrPort()
|
|
if !peer.Addr().IsLoopback() {
|
|
_ = reply(control, 2, emptyAddress)
|
|
return fmt.Errorf("UDP association source must match authenticated loopback client")
|
|
}
|
|
local := control.LocalAddr().(*net.TCPAddr).AddrPort().Addr()
|
|
udp, err := net.ListenUDP("udp", net.UDPAddrFromAddrPort(netip.AddrPortFrom(local, 0)))
|
|
if err != nil {
|
|
return err
|
|
}
|
|
defer udp.Close()
|
|
if err := reply(control, 0, udp.LocalAddr().(*net.UDPAddr).AddrPort()); err != nil {
|
|
return err
|
|
}
|
|
// An association cannot outlive the authenticated TCP connection.
|
|
done := make(chan struct{})
|
|
go func() { _, _ = io.Copy(io.Discard, control); udp.Close(); close(done) }()
|
|
defer func() { control.Close(); <-done }()
|
|
var mu sync.Mutex
|
|
flows := map[netip.AddrPort]net.Conn{}
|
|
var readers sync.WaitGroup
|
|
defer func() {
|
|
mu.Lock()
|
|
for _, flow := range flows {
|
|
flow.Close()
|
|
}
|
|
mu.Unlock()
|
|
readers.Wait()
|
|
}()
|
|
// sing-box sends the destination (possibly a domain), not the client's
|
|
// source, in UDP ASSOCIATE. Ownership comes from the authenticated TCP
|
|
// peer and the first valid UDP datagram; never trust request DST as source.
|
|
var sourcePort uint16
|
|
buffer := make([]byte, 65535)
|
|
for {
|
|
_ = udp.SetReadDeadline(time.Now().Add(2 * time.Minute))
|
|
n, source, err := udp.ReadFromUDPAddrPort(buffer)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
if source.Addr().Unmap() != peer.Addr().Unmap() || (sourcePort != 0 && source.Port() != sourcePort) {
|
|
continue
|
|
}
|
|
if n < 4 || buffer[0] != 0 || buffer[1] != 0 || buffer[2] != 0 {
|
|
continue
|
|
} // No SOCKS fragmentation.
|
|
r := &sliceReader{data: buffer[3:n]}
|
|
target, err := readDestination(r)
|
|
if err != nil {
|
|
continue
|
|
}
|
|
addresses, err := s.resolveDestination(ctx, target)
|
|
if err != nil {
|
|
s.journal.emit("destination_dns", err.Error(), nil)
|
|
continue
|
|
}
|
|
destination := addresses[0]
|
|
if err != nil || destination.Port() == 0 || destination.Addr().IsUnspecified() || destination.Addr().IsMulticast() {
|
|
continue
|
|
}
|
|
if sourcePort == 0 {
|
|
sourcePort = source.Port()
|
|
}
|
|
mu.Lock()
|
|
flow := flows[destination]
|
|
if flow == nil && len(flows) < 64 {
|
|
flow, err = s.dialUDP(destination)
|
|
if err == nil {
|
|
flows[destination] = flow
|
|
readers.Add(1)
|
|
go func(flow net.Conn, destination, client netip.AddrPort) {
|
|
defer readers.Done()
|
|
defer flow.Close()
|
|
defer func() {
|
|
mu.Lock()
|
|
if flows[destination] == flow {
|
|
delete(flows, destination)
|
|
}
|
|
mu.Unlock()
|
|
}()
|
|
packet := make([]byte, 65535)
|
|
for {
|
|
_ = flow.SetReadDeadline(time.Now().Add(time.Minute))
|
|
n, err := flow.Read(packet)
|
|
if err != nil {
|
|
return
|
|
}
|
|
response := append([]byte{0, 0, 0}, addressBytes(destination)...)
|
|
response = append(response, packet[:n]...)
|
|
if _, err := udp.WriteToUDPAddrPort(response, client); err != nil {
|
|
return
|
|
}
|
|
}
|
|
}(flow, destination, source)
|
|
}
|
|
}
|
|
mu.Unlock()
|
|
if err != nil {
|
|
s.journal.emit("udp", fmt.Sprintf("UDP %s: %v", destination, err), nil)
|
|
continue
|
|
}
|
|
if flow == nil {
|
|
continue
|
|
}
|
|
_ = flow.SetWriteDeadline(time.Now().Add(10 * time.Second))
|
|
if _, err := flow.Write(r.data); err != nil {
|
|
s.journal.emit("udp", fmt.Sprintf("UDP %s: %v", destination, err), nil)
|
|
flow.Close()
|
|
}
|
|
}
|
|
}
|
|
|
|
type sliceReader struct{ data []byte }
|
|
|
|
func (r *sliceReader) Read(p []byte) (int, error) {
|
|
if len(r.data) == 0 {
|
|
return 0, io.EOF
|
|
}
|
|
n := copy(p, r.data)
|
|
r.data = r.data[n:]
|
|
return n, nil
|
|
}
|