- 1 year ago
Prevent recursive hooking when using detours
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To prevent recursive hooking when using the Detours library, you can apply a technique called "reentrancy check" or "recursive lock" to ensure that a hook is not re-applied when it is already in effect. Here's an approach you can follow:
Use a flag or a lock variable:
- Create a global or static flag variable to keep track of the hooking state. Initialize it to
false
initially. - When you apply the hook, check the flag value.
- If the flag is
false
, proceed with the hooking process and set the flag totrue
. - If the flag is already
true
, skip the hooking process to prevent recursive hooking.
- If the flag is
- Create a global or static flag variable to keep track of the hooking state. Initialize it to
Reset the flag after unhooking:
- When you unhook the function, reset the flag to
false
. This ensures that the hooking process can be applied again when needed.
- When you unhook the function, reset the flag to
Here's an example in C++ using Detours:
cpp#include <windows.h>
#include <detours.h>
BOOL g_IsHooked = FALSE;
// Function pointer to store the original function
typedef BOOL(WINAPI* PFNORIGINALFUNCTION)(DWORD dwFlags);
// Hooked function
BOOL WINAPI HookedFunction(DWORD dwFlags)
{
// Perform your custom logic here
// Call the original function
PFNORIGINALFUNCTION pfnOriginalFunction = (PFNORIGINALFUNCTION)DetourFunctionOriginal(GetProcAddress(GetModuleHandle(L"user32.dll"), "OriginalFunction"));
return pfnOriginalFunction(dwFlags);
}
// Hooking function
void ApplyHook()
{
if (!g_IsHooked)
{
DetourTransactionBegin();
DetourUpdateThread(GetCurrentThread());
DetourAttach(&(PVOID&)OriginalFunction, HookedFunction);
DetourTransactionCommit();
g_IsHooked = TRUE;
}
}
// Unhooking function
void RemoveHook()
{
if (g_IsHooked)
{
DetourTransactionBegin();
DetourUpdateThread(GetCurrentThread());
DetourDetach(&(PVOID&)OriginalFunction, HookedFunction);
DetourTransactionCommit();
g_IsHooked = FALSE;
}
}
In this example, HookedFunction
is the replacement function that will be called when the original function is hooked. ApplyHook
applies the hook if it is not already in effect, and RemoveHook
removes the hook and resets the flag.
By implementing this reentrancy check, you can prevent recursive hooking and ensure that the hook is applied only once.