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// 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.
#ifndef BASE_WIN_IAT_PATCH_FUNCTION_H_
#define BASE_WIN_IAT_PATCH_FUNCTION_H_
#include <windows.h>
#include "base/base_export.h"
#include "base/basictypes.h"
namespace base {
namespace win {
// A class that encapsulates Import Address Table patching helpers and restores
// the original function in the destructor.
//
// It will intercept functions for a specific DLL imported from another DLL.
// This is the case when, for example, we want to intercept
// CertDuplicateCertificateContext function (exported from crypt32.dll) called
// by wininet.dll.
class BASE_EXPORT IATPatchFunction {
public:
IATPatchFunction();
~IATPatchFunction();
// Intercept a function in an import table of a specific
// module. Save the original function and the import
// table address. These values will be used later
// during Unpatch
//
// Arguments:
// module Module to be intercepted
// imported_from_module Module that exports the 'function_name'
// function_name Name of the API to be intercepted
//
// Returns: Windows error code (winerror.h). NO_ERROR if successful
//
// Note: Patching a function will make the IAT patch take some "ownership" on
// |module|. It will LoadLibrary(module) to keep the DLL alive until a call
// to Unpatch(), which will call FreeLibrary() and allow the module to be
// unloaded. The idea is to help prevent the DLL from going away while a
// patch is still active.
DWORD Patch(const wchar_t* module,
const char* imported_from_module,
const char* function_name,
void* new_function);
// Unpatch the IAT entry using internally saved original
// function.
//
// Returns: Windows error code (winerror.h). NO_ERROR if successful
DWORD Unpatch();
bool is_patched() const {
return (NULL != intercept_function_);
}
void* original_function() const;
private:
HMODULE module_handle_;
void* intercept_function_;
void* original_function_;
IMAGE_THUNK_DATA* iat_thunk_;
DISALLOW_COPY_AND_ASSIGN(IATPatchFunction);
};
} // namespace win
} // namespace base
#endif // BASE_WIN_IAT_PATCH_FUNCTION_H_
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