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/shared_memory.h"
  15 #include "base/memory/singleton.h"
  16
  17 // Forward
  18 namespace ATL {
  19 class CSecurityAttributes;
  20 }
  21
  22 namespace base {
  23 class Version;
  24 }
  25
  26 // A singleton class that provides a facility to register the version of the
  27 // current module as the only version that should be loaded system-wide. If
  28 // this module is not the first instance loaded in the system, then the version
  29 // that loaded first will be delegated to. This makes a few assumptions:
  30 //  1) That different versions of the module this code is in reside in
  31 //     neighbouring versioned directories, e.g.
  32 //       C:\foo\bar\1.2.3.4\my_module.dll
  33 //       C:\foo\bar\1.2.3.5\my_module.dll
  34 //  2) That the instance of this class will outlive the module that may be
  35 //     delegated to. That is to say, that this class only guarantees that the
  36 //     module is loaded as long as this instance is active.
  37 //  3) The module this is compiled into is built with version info.
  38 class DllRedirector {
  39  public:
  40   // Returns the singleton instance.
  41   static DllRedirector* GetInstance();
  42
  43   virtual ~DllRedirector();
  44
  45   // Attempts to register this Chrome Frame version as the first loaded version
  46   // on the system. If this succeeds, return true. If it fails, it returns
  47   // false meaning that there is another version already loaded somewhere and
  48   // the caller should delegate to that version instead.
  49   bool DllRedirector::RegisterAsFirstCFModule();
  50
  51   // Unregisters the well known window class if we registered it earlier.
  52   // This is intended to be called from DllMain under PROCESS_DETACH.
  53   void DllRedirector::UnregisterAsFirstCFModule();
  54
  55   // Helper function to return the DllGetClassObject function pointer from
  56   // the given module. This function will return NULL unless
  57   // RegisterAsFirstCFModule has been called first and returned false
  58   // indicating that another module was first in.
  59   //
  60   // On success, the return value is non-null and the first-in module will have
  61   // had its reference count incremented.
  62   LPFNGETCLASSOBJECT GetDllGetClassObjectPtr();
  63
  64  protected:
  65   DllRedirector();
  66   friend struct DefaultSingletonTraits<DllRedirector>;
  67
  68   // Constructor used for tests.
  69   explicit DllRedirector(const char* shared_memory_name);
  70
  71   // Returns an HMODULE to the version of the module that should be loaded.
  72   virtual HMODULE GetFirstModule();
  73
  74   // Returns the version of the current module or NULL if none can be found.
  75   // The caller must free the returned version.
  76   virtual base::Version* GetCurrentModuleVersion();
  77
  78   // Attempt to load the specified version dll. Finds it by walking up one
  79   // directory from our current module's location, then appending the newly
  80   // found version number. The Version class in base will have ensured that we
  81   // actually have a valid version and not e.g. ..\..\..\..\MyEvilFolder\.
  82   virtual HMODULE LoadVersionedModule(base::Version* version);
  83
  84   // Builds the necessary SECURITY_ATTRIBUTES to allow low integrity access
  85   // to an object. Returns true on success, false otherwise.
  86   virtual bool BuildSecurityAttributesForLock(
  87       ATL::CSecurityAttributes* sec_attr);
  88
  89   // Attempts to change the permissions on the given file mapping to read only.
  90   // Returns true on success, false otherwise.
  91   virtual bool SetFileMappingToReadOnly(base::SharedMemoryHandle mapping);
  92
  93   // Shared memory segment that contains the version beacon.
  94   scoped_ptr<base::SharedMemory> shared_memory_;
  95
  96   // The current version of the DLL to be loaded.
  97   scoped_ptr<base::Version> dll_version_;
  98
  99   // The handle to the first version of this module that was loaded. This
 100   // may refer to the current module, or another version of the same module
 101   // that we go and load.
 102   HMODULE first_module_handle_;
 103
 104   // Used for tests to override the name of the shared memory segment.
 105   std::string shared_memory_name_;
 106
 107   friend class ModuleUtilsTest;
 108
 109   DISALLOW_COPY_AND_ASSIGN(DllRedirector);
 110 };
 111
 112 #endif  // CHROME_FRAME_DLL_REDIRECTOR_H_