Further restrict access on the alternate winstation and desktop

sandbox/win/src/window.cc

 // Copyright (c) 2011 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.
 
 #include "sandbox/win/src/window.h"
 
 #include <aclapi.h>
 
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 26 matching lines @@
 ResultCode CreateAltWindowStation(HWINSTA* winsta) {
   // Get the security attributes from the current window station; we will
   // use this as the base security attributes for the new window station.
   SECURITY_ATTRIBUTES attributes = {0};
   if (!GetSecurityAttributes(::GetProcessWindowStation(), &attributes)) {
     return SBOX_ERROR_CANNOT_CREATE_WINSTATION;
   }
 
   // Create the window station using NULL for the name to ask the os to
   // generate it.
-  // TODO(nsylvain): don't ask for WINSTA_ALL_ACCESS if we don't need to.
-  *winsta = ::CreateWindowStationW(NULL, 0, WINSTA_ALL_ACCESS, &attributes);
+  *winsta = ::CreateWindowStationW(
+      NULL, 0, GENERIC_READ | WINSTA_CREATEDESKTOP, &attributes);
   LocalFree(attributes.lpSecurityDescriptor);
 
   if (*winsta)
     return SBOX_ALL_OK;
 
   return SBOX_ERROR_CANNOT_CREATE_WINSTATION;
 }
 
 ResultCode CreateAltDesktop(HWINSTA winsta, HDESK* desktop) {
   base::string16 desktop_name = L"sbox_alternate_desktop_";
@@ skipping 18 matching lines @@
   if (winsta) {
     // We need to switch to the alternate window station before creating the
     // desktop.
     if (!::SetProcessWindowStation(winsta)) {
       ::LocalFree(attributes.lpSecurityDescriptor);
       return SBOX_ERROR_CANNOT_CREATE_DESKTOP;
     }
   }
 
   // Create the destkop.
-  // TODO(nsylvain): don't ask for GENERIC_ALL if we don't need to.
-  *desktop = ::CreateDesktop(desktop_name.c_str(), NULL, NULL, 0, GENERIC_ALL,
+  *desktop = ::CreateDesktop(desktop_name.c_str(),
+                             NULL,
+                             NULL,
+                             0,
+                             DESKTOP_CREATEWINDOW | DESKTOP_READOBJECTS |
+                                 READ_CONTROL | WRITE_DAC | WRITE_OWNER,
                              &attributes);
   ::LocalFree(attributes.lpSecurityDescriptor);
 
   if (winsta) {
     // Revert to the right window station.
     if (!::SetProcessWindowStation(current_winsta)) {
       return SBOX_ERROR_FAILED_TO_SWITCH_BACK_WINSTATION;
     }
   }
 
@@ skipping 49 matching lines @@
   if (winsta) {
     name = GetWindowObjectName(winsta);
     name += L'\\';
   }
 
   name += GetWindowObjectName(desktop);
   return name;
 }
 
 }  // namespace sandbox