fix: reject non tunnel request & reject duplicated port

main.go

@@ -9,12 +9,16 @@ import (
 
 func main() {
 	sshConfig := &ssh.ServerConfig{
-		NoClientAuth: true,
+		NoClientAuth:  true,
+		ServerVersion: "SSH-2.0-TunnlPls-1.0",
 		PasswordCallback: func(conn ssh.ConnMetadata, password []byte) (*ssh.Permissions, error) {
 			return nil, nil
 		},
 	}
 
+	log.SetOutput(os.Stdout)
+	log.SetFlags(log.LstdFlags | log.Lshortfile)
+
 	privateBytes, err := os.ReadFile("id_rsa")
 	if err != nil {
 		log.Fatal("Failed to load private key (./id_rsa)")

server/handler.go

@@ -1,7 +1,6 @@
 package server
 
 import (
-	"fmt"
 	"golang.org/x/crypto/ssh"
 	"log"
 	"net"
@@ -16,7 +15,7 @@ func (s *Server) handleConnection(conn net.Conn) {
 		return
 	}
 
-	fmt.Println("SSH connection established:", sshConn.User())
+	log.Println("SSH connection established:", sshConn.User())
 
 	session.New(sshConn, chans, reqs)
 }

server/http.go

@@ -46,14 +46,14 @@ func Handler(conn net.Conn) {
 	reader := bufio.NewReader(conn)
 	headers, err := peekUntilHeaders(reader, 8192)
 	if err != nil {
-		fmt.Println("Failed to peek headers:", err)
+		log.Println("Failed to peek headers:", err)
 		return
 	}
 
 	host := strings.Split(parseHostFromHeader(headers), ".")
 	if len(host) < 1 {
 		conn.Write([]byte("HTTP/1.1 400 Bad Request\r\n\r\n"))
-		fmt.Println("Bad Request")
+		log.Println("Bad Request")
 		conn.Close()
 		return
 	}

server/https.go

@@ -4,7 +4,6 @@ import (
 	"bufio"
 	"crypto/tls"
 	"errors"
-	"fmt"
 	"golang.org/x/net/context"
 	"log"
 	"net"
@@ -46,7 +45,7 @@ func HandlerTLS(conn net.Conn) {
 	reader := bufio.NewReader(conn)
 	headers, err := peekUntilHeaders(reader, 8192)
 	if err != nil {
-		fmt.Println("Failed to peek headers:", err)
+		log.Println("Failed to peek headers:", err)
 		return
 	}
 

server/server.go

@@ -16,7 +16,7 @@ type Server struct {
 }
 
 func NewServer(config ssh.ServerConfig) *Server {
-	listener, err := net.Listen("tcp", ":2200")
+	listener, err := net.Listen("tcp", fmt.Sprintf(":%s", utils.Getenv("port")))
 	if err != nil {
 		log.Fatalf("failed to listen on port 2200: %v", err)
 		return nil
@@ -45,7 +45,7 @@ func NewServer(config ssh.ServerConfig) *Server {
 }
 
 func (s *Server) Start() {
-	fmt.Println("SSH server is starting on port 2200...")
+	log.Println("SSH server is starting on port 2200...")
 	for {
 		conn, err := (*s.Conn).Accept()
 		if err != nil {

session/handler.go

@@ -111,9 +111,11 @@ func (s *Session) Close() {
 }
 
 func (s *Session) handleGlobalRequest() {
+	ticker := time.NewTicker(1 * time.Second)
 	for {
 		select {
 		case req := <-s.GlobalRequest:
+			ticker.Stop()
 			if req == nil {
 				return
 			}
@@ -124,6 +126,9 @@ func (s *Session) handleGlobalRequest() {
 			}
 		case <-s.Done:
 			return
+		case <-ticker.C:
+			s.sendMessage(fmt.Sprintf("Please specify the forwarding tunnel. For example: 'ssh %s -p %s -R 443:localhost:8080' \r\n\n\n", utils.Getenv("domain"), utils.Getenv("port")))
+			s.Close()
 		}
 	}
 }
@@ -137,16 +142,30 @@ func (s *Session) handleTCPIPForward(req *ssh.Request) {
 	if err != nil {
 		log.Println("Failed to read address from payload:", err)
 		req.Reply(false, nil)
+		s.Close()
 		return
 	}
 
 	var portToBind uint32
 	if err := binary.Read(reader, binary.BigEndian, &portToBind); err != nil {
 		log.Println("Failed to read port from payload:", err)
+		s.sendMessage(fmt.Sprintf("Port %d is already in use or restricted. Please choose a different port.\r\n", portToBind))
 		req.Reply(false, nil)
+		s.Close()
 		return
 	}
 
+	if isBlockedPort(portToBind) {
+		s.sendMessage(fmt.Sprintf("Port %d is already in use or restricted. Please choose a different port.\r\n", portToBind))
+		req.Reply(false, nil)
+		s.Close()
+		return
+	}
+
+	s.sendMessage("\033[H\033[2J")
+	showWelcomeMessage(s.ConnChannels[0])
+	s.Status = RUNNING
+
 	if portToBind == 80 || portToBind == 443 {
 		s.handleHTTPForward(req, portToBind)
 		return
@@ -155,6 +174,23 @@ func (s *Session) handleTCPIPForward(req *ssh.Request) {
 	s.handleTCPForward(req, addr, portToBind)
 }
 
+var blockedReservedPorts = []uint32{1080, 1433, 1521, 1900, 2049, 3306, 3389, 5432, 5900, 6379, 8080, 8443, 9000, 9200, 27017}
+
+func isBlockedPort(port uint32) bool {
+	if port == 80 || port == 443 {
+		return false
+	}
+	if port < 1024 {
+		return true
+	}
+	for _, p := range blockedReservedPorts {
+		if p == port {
+			return true
+		}
+	}
+	return false
+}
+
 func (s *Session) handleHTTPForward(req *ssh.Request, portToBind uint32) {
 	s.TunnelType = HTTP
 	s.ForwardedPort = uint16(portToBind)
@@ -190,13 +226,14 @@ func (s *Session) handleTCPForward(req *ssh.Request, addr string, portToBind uin
 
 	listener, err := net.Listen("tcp", fmt.Sprintf("0.0.0.0:%d", portToBind))
 	if err != nil {
-		log.Printf("Failed to bind to port %d: %v", portToBind, err)
+		s.sendMessage(fmt.Sprintf("Port %d is already in use or restricted. Please choose a different port.\r\n", portToBind))
 		req.Reply(false, nil)
+		s.Close()
 		return
 	}
 	s.Listener = listener
 	s.ForwardedPort = uint16(portToBind)
-	s.sendMessage(fmt.Sprintf("Forwarding your traffic to %s://%s:%s \r\n", s.TunnelType, utils.Getenv("domain"), s.ForwardedPort))
+	s.sendMessage(fmt.Sprintf("Forwarding your traffic to %s://%s:%d \r\n", s.TunnelType, utils.Getenv("domain"), s.ForwardedPort))
 
 	go s.acceptTCPConnections()
 
@@ -466,7 +503,7 @@ func (s *Session) handleCommand(connection ssh.Channel, command string, inSlugEd
 			}
 			s.sendMessage(fmt.Sprintf("Forwarding your traffic to %s://%s.%s \r\n", protocol, s.Slug, domain))
 		} else {
-			s.sendMessage(fmt.Sprintf("Forwarding your traffic to %s://%s:%s \r\n", s.TunnelType, domain, s.ForwardedPort))
+			s.sendMessage(fmt.Sprintf("Forwarding your traffic to %s://%s:%d \r\n", s.TunnelType, domain, s.ForwardedPort))
 		}
 
 	case "/slug":
@@ -487,10 +524,6 @@ func (s *Session) handleCommand(connection ssh.Channel, command string, inSlugEd
 }
 
 func (s *Session) handleChannelRequests(connection ssh.Channel, requests <-chan *ssh.Request) {
-	connection.Write([]byte("\033[H\033[2J"))
-	showWelcomeMessage(connection)
-	s.Status = RUNNING
-
 	go s.handleGlobalRequest()
 
 	for req := range requests {