Method startNonPTYSession

agent/agentssh/agentssh.go:654–711

(logger slog.Logger, session ssh.Session, magicTypeLabel string, cmd *exec.Cmd)

}

func (s *Server) startNonPTYSession(logger slog.Logger, session ssh.Session, magicTypeLabel string, cmd *exec.Cmd) error {
	s.metrics.sessionsTotal.WithLabelValues(magicTypeLabel, "no").Add(1)

	// Create a process group and send SIGHUP to child processes,
	// otherwise context cancellation will not propagate properly
	// and SSH server close may be delayed.
	cmd.SysProcAttr = cmdSysProcAttr()

	// to match OpenSSH, we don't actually tear a non-TTY command down, even if the session ends. OpenSSH closes the
	// pipes to the process when the session ends; which is what happens here since we wire the command up to the
	// session for I/O.
	// c.f. https://github.com/coder/coder/issues/18519#issuecomment-3019118271
	cmd.Cancel = nil

	cmd.Stdout = session
	cmd.Stderr = session.Stderr()
	// This blocks forever until stdin is received if we don't
	// use StdinPipe. It's unknown what causes this.
	stdinPipe, err := cmd.StdinPipe()
	if err != nil {
		s.metrics.sessionErrors.WithLabelValues(magicTypeLabel, "no", "stdin_pipe").Add(1)
		return xerrors.Errorf("create stdin pipe: %w", err)
	}
	go func() {
		_, err := io.Copy(stdinPipe, session)
		if err != nil {
			s.metrics.sessionErrors.WithLabelValues(magicTypeLabel, "no", "stdin_io_copy").Add(1)
		}
		_ = stdinPipe.Close()
	}()
	err = cmd.Start()
	if err != nil {
		s.metrics.sessionErrors.WithLabelValues(magicTypeLabel, "no", "start_command").Add(1)
		return xerrors.Errorf("start: %w", err)
	}

	// Since we don't cancel the process when the session stops, we still need to tear it down if we are closing. So
	// track it here.
	if !s.trackProcess(cmd.Process, true) {
		// must be closing
		err = cmdCancel(logger, cmd.Process)
		return xerrors.Errorf("failed to track process: %w", err)
	}
	defer s.trackProcess(cmd.Process, false)

	sigs := make(chan ssh.Signal, 1)
	session.Signals(sigs)
	defer func() {
		session.Signals(nil)
		close(sigs)
	}()
	go func() {
		for sig := range sigs {
			handleSignal(logger, sig, cmd.Process, s.metrics, magicTypeLabel)
		}
	}()
	return cmd.Wait()
}