[android] invalidate stale SSH operations across reconnects

client/android/ssh_client.go

@@ -44,7 +44,10 @@ const PasswordRequiredMarker = "netbird-ssh-password-required"
 // reach this: NetBird peers verify against the registry.
 const HostKeyUnknownMarker = "netbird-ssh-hostkey-unknown"
 
-var errPasswordRequired = errors.New(PasswordRequiredMarker)
+var (
+	errPasswordRequired = errors.New(PasswordRequiredMarker)
+	errClientClosed     = errors.New("ssh client closed")
+)
 
 // errHostKeyUnknown carries the presented fingerprint so Connect can build the
 // marker message the Java side parses.
@@ -96,6 +99,13 @@ type SSHClient struct {
 	stdin     io.WriteCloser
 	closed    bool
 
+	// gen identifies the current connection attempt. Connect and Close bump it,
+	// so an in-flight dial or a reader left over from a previous connection
+	// finds itself stale and stays silent instead of publishing OnConnected or
+	// OnClose for a connection the caller already abandoned.
+	gen        uint64
+	dialCancel context.CancelFunc
+
 	// knownHostsPath is the TOFU store for regular SSH servers. Java supplies a
 	// per-profile path, since an overlay IP is a different host under a
 	// different profile. Empty until set: without it a regular server cannot be
@@ -180,6 +190,11 @@ func (s *SSHClient) Connect(host string, port int, user, password string) error
 		return errors.New("netbird engine not available")
 	}
 
+	s.mu.Lock()
+	s.gen++
+	gen := s.gen
+	s.mu.Unlock()
+
 	serverType := detectServerType(host, port)
 	log.Debugf("SSH server type: %s", serverType)
 
@@ -194,7 +209,7 @@ func (s *SSHClient) Connect(host string, port int, user, password string) error
 		HostKeyCallback: hostKeyCallback,
 		Timeout:         sshDialTimeout,
 	}
-	err = s.dialAndHandshake(host, port, clientConfig)
+	err = s.dialAndHandshake(gen, host, port, clientConfig)
 
 	// An unknown host key is a prompt, not a failure: return the marker intact
 	// (rootCause would unwrap it) so Java can show the fingerprint and retry.
@@ -257,6 +272,7 @@ func (s *SSHClient) startSession(cols, rows int) error {
 	log.Debugf("SSH: starting session %dx%d", cols, rows)
 	s.mu.Lock()
 	sshClient := s.sshClient
+	gen := s.gen
 	s.mu.Unlock()
 
 	if sshClient == nil {
@@ -303,6 +319,11 @@ func (s *SSHClient) startSession(cols, rows int) error {
 	}
 
 	s.mu.Lock()
+	if gen != s.gen {
+		s.mu.Unlock()
+		closeQuiet(session, "stale session")
+		return errClientClosed
+	}
 	s.session = session
 	s.stdin = stdin
 	s.mu.Unlock()
@@ -315,7 +336,7 @@ func (s *SSHClient) startSession(cols, rows int) error {
 		if second := <-readerDone; reason == "" {
 			reason = second
 		}
-		s.notifyClose(reason)
+		s.notifyClose(gen, reason)
 	}()
 	log.Debug("SSH: session started, shell running")
 	return nil
@@ -358,12 +379,20 @@ func (s *SSHClient) Reset() {
 // multiple times.
 func (s *SSHClient) Close() error {
 	s.mu.Lock()
+	s.gen++
+	if s.dialCancel != nil {
+		s.dialCancel()
+		s.dialCancel = nil
+	}
 	sshClient := s.sshClient
 	session := s.session
 	stdin := s.stdin
 	s.sshClient = nil
 	s.session = nil
 	s.stdin = nil
+	notify := !s.closed
+	s.closed = true
+	listener := s.listener
 	s.mu.Unlock()
 
 	if stdin != nil {
@@ -382,7 +411,9 @@ func (s *SSHClient) Close() error {
 			firstErr = err
 		}
 	}
-	s.notifyClose("closed by client")
+	if notify && listener != nil {
+		listener.OnClose("closed by client")
+	}
 	return firstErr
 }
 
@@ -556,11 +587,19 @@ func (s *SSHClient) requestJWTToken(cfg *profilemanager.Config) (string, error)
 	return token, nil
 }
 
-func (s *SSHClient) dialAndHandshake(host string, port int, clientConfig *gossh.ClientConfig) error {
+func (s *SSHClient) dialAndHandshake(gen uint64, host string, port int, clientConfig *gossh.ClientConfig) error {
 	addr := net.JoinHostPort(host, strconv.Itoa(port))
 	ctx, cancel := context.WithTimeout(context.Background(), sshDialTimeout)
 	defer cancel()
 
+	s.mu.Lock()
+	if gen != s.gen {
+		s.mu.Unlock()
+		return errClientClosed
+	}
+	s.dialCancel = cancel
+	s.mu.Unlock()
+
 	var dialer net.Dialer
 	conn, err := dialer.DialContext(ctx, "tcp", addr)
 	if err != nil {
@@ -590,8 +629,14 @@ func (s *SSHClient) dialAndHandshake(host string, port int, clientConfig *gossh.
 		return fmt.Errorf("clear handshake deadline: %w", err)
 	}
 
+	client := gossh.NewClient(sshConn, chans, reqs)
 	s.mu.Lock()
-	s.sshClient = gossh.NewClient(sshConn, chans, reqs)
+	if gen != s.gen {
+		s.mu.Unlock()
+		closeQuiet(client, "stale ssh client")
+		return errClientClosed
+	}
+	s.sshClient = client
 	listener := s.listener
 	s.mu.Unlock()
 
@@ -637,9 +682,9 @@ func (s *SSHClient) notifyStatus(text string) {
 	}
 }
 
-func (s *SSHClient) notifyClose(reason string) {
+func (s *SSHClient) notifyClose(gen uint64, reason string) {
 	s.mu.Lock()
-	if s.closed {
+	if gen != s.gen || s.closed {
 		s.mu.Unlock()
 		return
 	}