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      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_
    113