chrome_frame/dll_redirector.h

   1 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef CHROME_FRAME_DLL_REDIRECTOR_H_
   6 #define CHROME_FRAME_DLL_REDIRECTOR_H_
   7
   8 #include <ObjBase.h>
   9 #include <windows.h>
  10 #include <string>
  11
  12 #include "base/basictypes.h"
  13 #include "base/memory/scoped_ptr.h"
  14 #include "base/memory/singleton.h"
  15 #include "base/shared_memory.h"
  16
  17 // Forward
  18 namespace ATL {
  19 class CSecurityAttributes;
  20 }
  21 class Version;
  22
  23 // A singleton class that provides a facility to register the version of the
  24 // current module as the only version that should be loaded system-wide. If
  25 // this module is not the first instance loaded in the system, then the version
  26 // that loaded first will be delegated to. This makes a few assumptions:
  27 //  1) That different versions of the module this code is in reside in
  28 //     neighbouring versioned directories, e.g.
  29 //       C:\foo\bar\1.2.3.4\my_module.dll
  30 //       C:\foo\bar\1.2.3.5\my_module.dll
  31 //  2) That the instance of this class will outlive the module that may be
  32 //     delegated to. That is to say, that this class only guarantees that the
  33 //     module is loaded as long as this instance is active.
  34 //  3) The module this is compiled into is built with version info.
  35 class DllRedirector {
  36  public:
  37   // Returns the singleton instance.
  38   static DllRedirector* GetInstance();
  39
  40   virtual ~DllRedirector();
  41
  42   // Attempts to register this Chrome Frame version as the first loaded version
  43   // on the system. If this succeeds, return true. If it fails, it returns
  44   // false meaning that there is another version already loaded somewhere and
  45   // the caller should delegate to that version instead.
  46   bool DllRedirector::RegisterAsFirstCFModule();
  47
  48   // Unregisters the well known window class if we registered it earlier.
  49   // This is intended to be called from DllMain under PROCESS_DETACH.
  50   void DllRedirector::UnregisterAsFirstCFModule();
  51
  52   // Helper function to return the DllGetClassObject function pointer from
  53   // the given module. This function will return NULL unless
  54   // RegisterAsFirstCFModule has been called first and returned false
  55   // indicating that another module was first in.
  56   //
  57   // On success, the return value is non-null and the first-in module will have
  58   // had its reference count incremented.
  59   LPFNGETCLASSOBJECT GetDllGetClassObjectPtr();
  60
  61  protected:
  62   DllRedirector();
  63   friend struct DefaultSingletonTraits<DllRedirector>;
  64
  65   // Constructor used for tests.
  66   explicit DllRedirector(const char* shared_memory_name);
  67
  68   // Returns an HMODULE to the version of the module that should be loaded.
  69   virtual HMODULE GetFirstModule();
  70
  71   // Returns the version of the current module or NULL if none can be found.
  72   // The caller must free the Version.
  73   virtual Version* GetCurrentModuleVersion();
  74
  75   // Attempt to load the specified version dll. Finds it by walking up one
  76   // directory from our current module's location, then appending the newly
  77   // found version number. The Version class in base will have ensured that we
  78   // actually have a valid version and not e.g. ..\..\..\..\MyEvilFolder\.
  79   virtual HMODULE LoadVersionedModule(Version* version);
  80
  81   // Builds the necessary SECURITY_ATTRIBUTES to allow low integrity access
  82   // to an object. Returns true on success, false otherwise.
  83   virtual bool BuildSecurityAttributesForLock(
  84       ATL::CSecurityAttributes* sec_attr);
  85
  86   // Attempts to change the permissions on the given file mapping to read only.
  87   // Returns true on success, false otherwise.
  88   virtual bool SetFileMappingToReadOnly(base::SharedMemoryHandle mapping);
  89
  90   // Shared memory segment that contains the version beacon.
  91   scoped_ptr<base::SharedMemory> shared_memory_;
  92
  93   // The current version of the DLL to be loaded.
  94   scoped_ptr<Version> dll_version_;
  95
  96   // The handle to the first version of this module that was loaded. This
  97   // may refer to the current module, or another version of the same module
  98   // that we go and load.
  99   HMODULE first_module_handle_;
 100
 101   // Used for tests to override the name of the shared memory segment.
 102   std::string shared_memory_name_;
 103
 104   friend class ModuleUtilsTest;
 105
 106   DISALLOW_COPY_AND_ASSIGN(DllRedirector);
 107 };
 108
 109 #endif  // CHROME_FRAME_DLL_REDIRECTOR_H_