Implement reverse connection handling in SOCKS5 server

exit/exit.go

@@ -183,6 +183,8 @@ func (e *Exit) processMessage(ctx context.Context, msg nostr.IncomingEvent) {
 	switch protocolMessage.Type {
 	case protocol.MessageConnect:
 		e.handleConnect(ctx, msg, protocolMessage, false)
+	case protocol.MessageConnectReverse:
+		e.handleConnectReverse(ctx, protocolMessage, false)
 	case protocol.MessageTypeSocks5:
 		e.handleSocks5ProxyMessage(msg, protocolMessage)
 	}
@@ -226,6 +228,33 @@ func (e *Exit) handleConnect(ctx context.Context, msg nostr.IncomingEvent, proto
 	go socks5.Proxy(connection, dst, nil)
 }
 
+func (e *Exit) handleConnectReverse(ctx context.Context, protocolMessage *protocol.Message, isTLS bool) {
+	e.mutexMap.Lock(protocolMessage.Key.String())
+	defer e.mutexMap.Unlock(protocolMessage.Key.String())
+	connection, err := net.Dial("tcp", ":1234")
+	if err != nil {
+		return
+	}
+	var dst net.Conn
+	if isTLS {
+		conf := tls.Config{InsecureSkipVerify: true}
+		dst, err = tls.Dial("tcp", e.config.BackendHost, &conf)
+	} else {
+		dst, err = net.Dial("tcp", e.config.BackendHost)
+	}
+	if err != nil {
+		slog.Error("could not connect to backend", "error", err)
+		return
+	}
+
+	_, err = connection.Write([]byte(protocolMessage.Key.String()))
+	if err != nil {
+		return
+	}
+	go socks5.Proxy(dst, connection, nil)
+	go socks5.Proxy(connection, dst, nil)
+}
+
 // handleSocks5ProxyMessage handles the SOCKS5 proxy message by writing it to the destination connection.
 // If the destination connection does not exist, the function returns without doing anything.
 //

netstr/dial.go

@@ -17,10 +17,9 @@ import (
 // It creates a signed event using the private key, public key, and destination address.
 // It ensures that the relays are available in the pool and publishes the signed event to each relay.
 // Finally, it returns the Connection and nil error. If there are any errors, nil connection and the error are returned.
-func DialSocks(pool *nostr.SimplePool) func(ctx context.Context, net_, addr string) (net.Conn, error) {
+func DialSocks(pool *nostr.SimplePool, connectionID uuid.UUID) func(ctx context.Context, net_, addr string) (net.Conn, error) {
 	return func(ctx context.Context, net_, addr string) (net.Conn, error) {
 		addr = strings.ReplaceAll(addr, ".", "")
-		connectionID := uuid.New()
 		key := nostr.GeneratePrivateKey()
 		connection := NewConnection(ctx,
 			WithPrivateKey(key),
@@ -39,7 +38,7 @@ func DialSocks(pool *nostr.SimplePool) func(ctx context.Context, net_, addr stri
 			return nil, err
 		}
 		opts := []protocol.MessageOption{
-			protocol.WithType(protocol.MessageConnect),
+			protocol.WithType(protocol.MessageConnectReverse),
 			protocol.WithUUID(connectionID),
 			protocol.WithDestination(addr),
 		}

protocol/message.go

@@ -8,8 +8,9 @@ import (
 type MessageType string
 
 var (
-	MessageTypeSocks5 = MessageType("SOCKS5")
-	MessageConnect    = MessageType("CONNECT")
+	MessageTypeSocks5     = MessageType("SOCKS5")
+	MessageConnect        = MessageType("CONNECT")
+	MessageConnectReverse = MessageType("CONNECTR")
 )
 
 type Message struct {

socks5/request.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"fmt"
 	"github.com/asmogo/nws/netstr"
+	"github.com/google/uuid"
 	"io"
 	"net"
 	"strconv"
@@ -167,8 +168,11 @@ func (s *Server) handleConnect(ctx context.Context, conn net.Conn, req *Request)
 
 	// Attempt to connect
 	dial := s.config.Dial
+	ch := make(chan net.Conn)
 	if dial == nil {
-		dial = netstr.DialSocks(s.pool)
+		connectionID := uuid.New()
+		s.tcpListener.AddConnectChannel(connectionID, ch)
+		dial = netstr.DialSocks(s.pool, connectionID)
 	}
 	target, err := dial(ctx, "tcp", req.realDestAddr.FQDN)
 	if err != nil {
@@ -192,11 +196,16 @@ func (s *Server) handleConnect(ctx context.Context, conn net.Conn, req *Request)
 	if err := SendReply(conn, successReply, &bind); err != nil {
 		return fmt.Errorf("failed to send reply: %v", err)
 	}
+	// read
+
+	// wait for the connection
+	connR := <-ch
+	defer connR.Close()
 
 	// Start proxying
 	errCh := make(chan error, 2)
-	go Proxy(target, conn, errCh)
-	go Proxy(conn, target, errCh)
+	go Proxy(connR, conn, errCh)
+	go Proxy(conn, connR, errCh)
 
 	// Wait
 	for i := 0; i < 2; i++ {

socks5/socks5.go

@@ -59,6 +59,7 @@ type Server struct {
 	config      *Config
 	authMethods map[uint8]Authenticator
 	pool        *nostr.SimplePool
+	tcpListener *TCPListener
 }
 
 // New creates a new Server and potentially returns an error
@@ -86,12 +87,16 @@ func New(conf *Config, pool *nostr.SimplePool) (*Server, error) {
 	if conf.Logger == nil {
 		conf.Logger = log.New(os.Stdout, "", log.LstdFlags)
 	}
-
-	server := &Server{
-		config: conf,
-		pool:   pool,
+	listener, err := NewTCPListener()
+	if err != nil {
+		return nil, err
+	}
+	go listener.Start()
+	server := &Server{
+		config:      conf,
+		pool:        pool,
+		tcpListener: listener,
 	}
-
 	server.authMethods = make(map[uint8]Authenticator)
 
 	for _, a := range conf.AuthMethods {

socks5/tcp.go

@@ -0,0 +1,63 @@
+package socks5
+
+import (
+	"github.com/google/uuid"
+	"github.com/puzpuzpuz/xsync/v3"
+	"log/slog"
+	"net"
+)
+
+type TCPListener struct {
+	listener        net.Listener
+	connectChannels *xsync.MapOf[string, chan net.Conn] // todo -- use [16]byte for uuid instead of string
+}
+
+func NewTCPListener() (*TCPListener, error) {
+	l, err := net.Listen("tcp", ":1234")
+	if err != nil {
+		return nil, err
+	}
+	return &TCPListener{
+		listener:        l,
+		connectChannels: xsync.NewMapOf[string, chan net.Conn](),
+	}, nil
+}
+
+func (l *TCPListener) AddConnectChannel(uuid uuid.UUID, ch chan net.Conn) {
+	l.connectChannels.Store(uuid.String(), ch)
+}
+
+// Start starts the listener
+func (l *TCPListener) Start() {
+	for {
+		conn, err := l.listener.Accept()
+		if err != nil {
+			return
+		}
+		go l.handleConnection(conn)
+	}
+}
+
+// handleConnection handles the connection
+func (l *TCPListener) handleConnection(conn net.Conn) {
+	//defer conn.Close()
+	for {
+		// read uuid from the connection
+		readbuffer := make([]byte, 36)
+
+		_, err := conn.Read(readbuffer)
+		if err != nil {
+			return
+		}
+
+		// check if uuid is in the map
+		ch, ok := l.connectChannels.Load(string(readbuffer))
+		if !ok {
+			slog.Error("uuid not found in map")
+			return
+		}
+		// send the connection to the channel
+		ch <- conn
+		return
+	}
+}