AUTH-2056: Writes stderr to its own stream for non-pty connections

.gitignore

@@ -9,5 +9,7 @@ guide/public
 \#*\#
 cscope.*
 cloudflared
+cloudflared.exe
 !cmd/cloudflared/
 .DS_Store
+*-session.log

cmd/cloudflared/tunnel/cmd.go

@@ -366,8 +366,9 @@ func StartServer(c *cli.Context, version string, shutdownC, graceShutdownC chan
 
 	if c.IsSet("ssh-server") {
 		if runtime.GOOS != "darwin" && runtime.GOOS != "linux" {
-			logger.Errorf("--ssh-server is not supported on %s", runtime.GOOS)
+			msg := fmt.Sprintf("--ssh-server is not supported on %s", runtime.GOOS)
-			return errors.New(fmt.Sprintf("--ssh-server is not supported on %s", runtime.GOOS))
+			logger.Error(msg)
+			return errors.New(msg)
 
 		}
 
@@ -378,11 +379,17 @@ func StartServer(c *cli.Context, version string, shutdownC, graceShutdownC chan
 			uploader, err := awsuploader.NewFileUploader(c.String(bucketNameFlag), c.String(regionNameFlag),
 				c.String(accessKeyIDFlag), c.String(secretIDFlag), c.String(sessionTokenIDFlag), c.String(s3URLFlag))
 			if err != nil {
-				logger.WithError(err).Error("Cannot create uploader for SSH Server")
+				msg := "Cannot create uploader for SSH Server"
-				return errors.Wrap(err, "Cannot create uploader for SSH Server")
+				logger.WithError(err).Error(msg)
+				return errors.Wrap(err, msg)
+			}
+
+			if err := os.Mkdir(sshLogFileDirectory, 0600); err != nil {
+				msg := fmt.Sprintf("Cannot create SSH log file directory %s", sshLogFileDirectory)
+				logger.WithError(err).Errorf(msg)
+				return errors.Wrap(err, msg)
 			}
 
-			os.Mkdir(sshLogFileDirectory, 0600)
 			logManager = sshlog.New(sshLogFileDirectory)
 
 			uploadManager := awsuploader.NewDirectoryUploadManager(logger, uploader, sshLogFileDirectory, 30*time.Minute, shutdownC)
@@ -392,8 +399,9 @@ func StartServer(c *cli.Context, version string, shutdownC, graceShutdownC chan
 		sshServerAddress := "127.0.0.1:" + c.String(sshPortFlag)
 		server, err := sshserver.New(logManager, logger, version, sshServerAddress, shutdownC, c.Duration(sshIdleTimeoutFlag), c.Duration(sshMaxTimeoutFlag), c.Bool(enablePortForwardingFlag))
 		if err != nil {
-			logger.WithError(err).Error("Cannot create new SSH Server")
+			msg := "Cannot create new SSH Server"
-			return errors.Wrap(err, "Cannot create new SSH Server")
+			logger.WithError(err).Error(msg)
+			return errors.Wrap(err, msg)
 		}
 		wg.Add(1)
 		go func() {

sshlog/empty_manager.go

@@ -29,7 +29,7 @@ func (m *emptyManager) NewSessionLogger(name string, logger *logrus.Logger) (io.
 // emptyWriteCloser
 
 func (w *emptyWriteCloser) Write(p []byte) (n int, err error) {
-	return 0, nil
+	return len(p), nil
 }
 
 func (w *emptyWriteCloser) Close() error {

sshserver/sshserver_unix.go

@@ -33,7 +33,6 @@ const (
 	auditEventExec   = "exec"
 	auditEventScp    = "scp"
 	auditEventResize = "resize"
-	auditEventTamper = "tamper"
 )
 
 type auditEvent struct {
@@ -156,14 +155,18 @@ func (s *SSHServer) connectionHandler(session ssh.Session) {
 
 	var shellInput io.WriteCloser
 	var shellOutput io.ReadCloser
+	pr, pw := io.Pipe()
+	defer pw.Close()
 
 	ptyReq, winCh, isPty := session.Pty()
 
 	if isPty {
 		cmd.Env = append(cmd.Env, fmt.Sprintf("TERM=%s", ptyReq.Term))
-		shellInput, shellOutput, err = s.startPtySession(cmd, winCh, func() {
+		tty, err := s.startPtySession(cmd, winCh, func() {
 			s.logAuditEvent(eventLogger, session, sessionID, auditEventResize)
 		})
+		shellInput = tty
+		shellOutput = tty
 		if err != nil {
 			s.logger.WithError(err).Error("Failed to start pty session")
 			close(s.shutdownC)
@@ -172,7 +175,8 @@ func (s *SSHServer) connectionHandler(session ssh.Session) {
 		s.logAuditEvent(eventLogger, session, sessionID, auditEventStart)
 		defer s.logAuditEvent(eventLogger, session, sessionID, auditEventStop)
 	} else {
-		shellInput, shellOutput, err = s.startNonPtySession(cmd)
+		var shellError io.ReadCloser
+		shellInput, shellOutput, shellError, err = s.startNonPtySession(cmd)
 		if err != nil {
 			s.logger.WithError(err).Error("Failed to start non-pty session")
 			close(s.shutdownC)
@@ -183,18 +187,15 @@ func (s *SSHServer) connectionHandler(session ssh.Session) {
 			event = auditEventScp
 		}
 		s.logAuditEvent(eventLogger, session, sessionID, event)
-	}
 
-	// Write incoming commands to shell
+		// Write stderr to both the command recorder, and remote user
 		go func() {
-		if _, err := io.Copy(shellInput, session); err != nil {
+			mw := io.MultiWriter(pw, session.Stderr())
-			s.logger.WithError(err).Error("Failed to write incoming command to pty")
+			if _, err := io.Copy(mw, shellError); err != nil {
+				s.logger.WithError(err).Error("Failed to write stderr to user")
 			}
 		}()
-
+	}
-	pr, pw := io.Pipe()
-	defer pr.Close()
-	defer pw.Close()
 
 	sessionLogger, err := s.logManager.NewSessionLogger(fmt.Sprintf("%s-session.log", sessionID), s.logger)
 	if err != nil {
@@ -206,13 +207,25 @@ func (s *SSHServer) connectionHandler(session ssh.Session) {
 	}
 	defer sessionLogger.Close()
 	go func() {
-		io.Copy(sessionLogger, pr)
+		defer pr.Close()
+		_, err := io.Copy(sessionLogger, pr)
+		if err != nil {
+			s.logger.WithError(err).Error("Failed to write session log")
+		}
 	}()
 
-	// Write outgoing command output to both the command recorder, and remote user
+	// Write stdin to shell
+	go func() {
+		defer shellInput.Close()
+		if _, err := io.Copy(shellInput, session); err != nil {
+			s.logger.WithError(err).Error("Failed to write incoming command to pty")
+		}
+	}()
+
+	// Write stdout to both the command recorder, and remote user
 	mw := io.MultiWriter(pw, session)
 	if _, err := io.Copy(mw, shellOutput); err != nil {
-		s.logger.WithError(err).Error("Failed to write command output to user")
+		s.logger.WithError(err).Error("Failed to write stdout to user")
 	}
 
 	// Wait for all resources associated with cmd to be released
@@ -264,8 +277,8 @@ func (s *SSHServer) getSSHUser(session ssh.Session, sessionID string, eventLogge
 
 // errorAndExit reports an error with the session and exits
 func (s *SSHServer) errorAndExit(session ssh.Session, errText string, err error) {
-	if err := session.Exit(1); err != nil {
+	if exitError := session.Exit(1); exitError != nil {
-		s.logger.WithError(err).Error("Failed to close SSH session")
+		s.logger.WithError(exitError).Error("Failed to close SSH session")
 	} else if err != nil {
 		s.logger.WithError(err).Error(errText)
 	} else if errText != "" {
@@ -273,26 +286,31 @@ func (s *SSHServer) errorAndExit(session ssh.Session, errText string, err error)
 	}
 }
 
-func (s *SSHServer) startNonPtySession(cmd *exec.Cmd) (io.WriteCloser, io.ReadCloser, error) {
+func (s *SSHServer) startNonPtySession(cmd *exec.Cmd) (stdin io.WriteCloser, stdout io.ReadCloser, stderr io.ReadCloser, err error) {
-	in, err := cmd.StdinPipe()
+	stdin, err = cmd.StdinPipe()
 	if err != nil {
-		return nil, nil, err
+		return
 	}
-	out, err := cmd.StdoutPipe()
+	stdout, err = cmd.StdoutPipe()
 	if err != nil {
-		return nil, nil, err
+		return
-	}
-	cmd.Stderr = cmd.Stdout
-	if err = cmd.Start(); err != nil {
-		return nil, nil, err
-	}
-	return in, out, nil
 	}
 
-func (s *SSHServer) startPtySession(cmd *exec.Cmd, winCh <-chan ssh.Window, logCallback func()) (io.WriteCloser, io.ReadCloser, error) {
+	stderr, err = cmd.StderrPipe()
+	if err != nil {
+		return
+	}
+
+	if err = cmd.Start(); err != nil {
+		return
+	}
+	return
+}
+
+func (s *SSHServer) startPtySession(cmd *exec.Cmd, winCh <-chan ssh.Window, logCallback func()) (io.ReadWriteCloser, error) {
 	tty, err := pty.Start(cmd)
 	if err != nil {
-		return nil, nil, err
+		return nil, err
 	}
 
 	// Handle terminal window size changes
@@ -307,7 +325,7 @@ func (s *SSHServer) startPtySession(cmd *exec.Cmd, winCh <-chan ssh.Window, logC
 		}
 	}()
 
-	return tty, tty, nil
+	return tty, nil
 }
 
 func (s *SSHServer) logAuditEvent(writer io.WriteCloser, session ssh.Session, sessionID string, eventType string) {
@@ -328,11 +346,14 @@ func (s *SSHServer) logAuditEvent(writer io.WriteCloser, session ssh.Session, se
 	}
 	data, err := json.Marshal(&event)
 	if err != nil {
-		s.logger.WithError(err).Error("Failed to log audit event. malformed audit object")
+		s.logger.WithError(err).Error("Failed to marshal audit event. malformed audit object")
 		return
 	}
 	line := string(data) + "\n"
-	writer.Write([]byte(line))
+	if _, err := writer.Write([]byte(line)); err != nil {
+		s.logger.WithError(err).Error("Failed to write audit event.")
+	}
+
 }
 
 // Sets PTY window size for terminal