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// Copyright (c) 2006-2008 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.
// This file declares a helpers to intercept functions from a DLL.
//
// This set of functions are designed to 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.
#ifndef BASE_IAT_PATCH_H__
#define BASE_IAT_PATCH_H__
#include <windows.h>
#include "base/basictypes.h"
#include "base/pe_image.h"
namespace iat_patch {
// Helper to intercept a function in an import table of a specific
// module.
//
// Arguments:
// module_handle Module to be intercepted
// imported_from_module Module that exports the symbol
// function_name Name of the API to be intercepted
// new_function Interceptor function
// old_function Receives the original function pointer
// iat_thunk Receives pointer to IAT_THUNK_DATA
// for the API from the import table.
//
// Returns: Returns NO_ERROR on success or Windows error code
// as defined in winerror.h
//
DWORD InterceptImportedFunction(HMODULE module_handle,
const char* imported_from_module,
const char* function_name,
void* new_function,
void** old_function,
IMAGE_THUNK_DATA** iat_thunk);
// Restore intercepted IAT entry with the original function.
//
// Arguments:
// intercept_function Interceptor function
// original_function Receives the original function pointer
//
// Returns: Returns NO_ERROR on success or Windows error code
// as defined in winerror.h
//
DWORD RestoreImportedFunction(void* intercept_function,
void* original_function,
IMAGE_THUNK_DATA* iat_thunk);
// Change the page protection (of code pages) to writable and copy
// the data at the specified location
//
// Arguments:
// old_code Target location to copy
// new_code Source
// length Number of bytes to copy
//
// Returns: Windows error code (winerror.h). NO_ERROR if successful
//
DWORD ModifyCode(void* old_code,
void* new_code,
int length);
// A class that encapsulates IAT patching helpers and restores
// the original function in the destructor.
class 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_);
}
private:
HMODULE module_handle_;
void* intercept_function_;
void* original_function_;
IMAGE_THUNK_DATA* iat_thunk_;
DISALLOW_EVIL_CONSTRUCTORS(IATPatchFunction);
};
} // namespace iat_patch
#endif // BASE_IAT_PATCH_H__
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