Improve xsession execution

remoting/tools/me2me_virtual_host.py

 #!/usr/bin/python
 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # Virtual Me2Me implementation.  This script runs and manages the processes
 # required for a Virtual Me2Me desktop, which are: X server, X desktop
 # session, and Host process.
 # This script is intended to run continuously as a background daemon
 # process, running under an ordinary (non-root) user account.
 
 import atexit
 import errno
 import getpass
 import hashlib
 import json
 import logging
 import optparse
 import os
+import pipes
 import signal
 import socket
 import subprocess
 import sys
 import tempfile
 import time
 import uuid
 
 # By default this script will try to determine the most appropriate X session
 # command for the system.  To use a specific session instead, set this variable
@@ skipping 312 matching lines @@
     # list.
     label = "%dx%d" % self.sizes[0]
     args = ["xrandr", "-s", label]
     proc = subprocess.Popen(args, env=self.child_env, stdout=devnull,
                             stderr=devnull)
     proc.wait()
 
     devnull.close()
 
   def _launch_x_session(self):
-    # Start desktop session
+    # Start desktop session.
     # The /dev/null input redirection is necessary to prevent the X session
     # reading from stdin.  If this code runs as a shell background job in a
     # terminal, any reading from stdin causes the job to be suspended.
     # Daemonization would solve this problem by separating the process from the
     # controlling terminal.
     logging.info("Launching X session: %s" % XSESSION_COMMAND)
     self.session_proc = subprocess.Popen(XSESSION_COMMAND,
                                          stdin=open(os.devnull, "r"),
                                          cwd=HOME_DIR,
                                          env=self.child_env)
@@ skipping 128 matching lines @@
     "~/.chrome-remote-desktop-session",
     "~/.xsession",
     "~/.Xsession" ]
   for startup_file in XSESSION_FILES:
     startup_file = os.path.expanduser(startup_file)
     if os.path.exists(startup_file):
       # Use the same logic that a Debian system typically uses with ~/.xsession
       # (see /etc/X11/Xsession.d/50x11-common_determine-startup), to determine
       # exactly how to run this file.
       if os.access(startup_file, os.X_OK):
-        return startup_file
+        # "/bin/sh -c" is smart about how to execute the session script and
+        # works in cases where plain exec() fails (for example, if the file is
+        # marked executable, but is a plain script with no shebang line).
+        return ["/bin/sh", "-c", pipes.quote(startup_file)]
       else:
         shell = os.environ.get("SHELL", "sh")
         return [shell, startup_file]
 
   # Choose a session wrapper script to run the session. On some systems,
   # /etc/X11/Xsession fails to load the user's .profile, so look for an
   # alternative wrapper that is more likely to match the script that the
   # system actually uses for console desktop sessions.
   SESSION_WRAPPERS = [
     "/usr/sbin/lightdm-session",
@@ skipping 538 matching lines @@
         host_config.clear_auth()
         host_config.clear_host_info()
         host_config.save()
         return 0
 
 
 if __name__ == "__main__":
   logging.basicConfig(level=logging.DEBUG,
                       format="%(asctime)s:%(levelname)s:%(message)s")
   sys.exit(main())