mardi 29 juin 2021

VEH hook acceleration

I am trying to accelerate the speed of VEH hook. Veh hook class that I found from https://github.com/hoangprod/LeoSpecial-VEH-Hook/blob/master/LeoSpecial.h

#pragma once
#include <Windows.h>
#include <stdio.h>
#include <iostream>

#ifdef _WIN64
#define XIP Rip
#else
#define XIP Eip
#endif



class LeoHook {
public:
    static bool Hook(uintptr_t og_fun, uintptr_t hk_fun);
    static bool Unhook();

private:
    static uintptr_t og_fun;
    static uintptr_t hk_fun;
    static PVOID VEH_Handle;
    static DWORD oldProtection;

    static bool AreInSamePage(const uint8_t* Addr1, const uint8_t* Addr2);
    static LONG WINAPI LeoHandler(EXCEPTION_POINTERS *pExceptionInfo);
};

uintptr_t LeoHook::og_fun = 0;
uintptr_t LeoHook::hk_fun = 0;
PVOID LeoHook::VEH_Handle = nullptr;
DWORD LeoHook::oldProtection = 0;

bool LeoHook::Hook(uintptr_t original_fun, uintptr_t hooked_fun)
{
    LeoHook::og_fun = original_fun;
    LeoHook::hk_fun = hooked_fun;

    //We cannot hook two functions in the same page, because we will cause an infinite callback
    if (AreInSamePage((const uint8_t*)og_fun, (const uint8_t*)hk_fun))
        return false;

    //Register the Custom Exception Handler
    VEH_Handle = AddVectoredExceptionHandler(true, (PVECTORED_EXCEPTION_HANDLER)LeoHandler);

    //Toggle PAGE_GUARD flag on the page
    if(VEH_Handle && VirtualProtect((LPVOID)og_fun, 1, PAGE_EXECUTE_READ | PAGE_GUARD, &oldProtection))
        return true;
    
    return false;
}

bool LeoHook::Unhook()
{
    DWORD old;
    if (VEH_Handle && //Make sure we have a valid Handle to the registered VEH
        VirtualProtect((LPVOID)og_fun, 1, oldProtection, &old) && //Restore old Flags
        RemoveVectoredExceptionHandler(VEH_Handle)) //Remove the VEH
        return true;

    return false;
}

LONG WINAPI LeoHook::LeoHandler(EXCEPTION_POINTERS *pExceptionInfo)
{
    if (pExceptionInfo->ExceptionRecord->ExceptionCode == STATUS_GUARD_PAGE_VIOLATION) //We will catch PAGE_GUARD Violation
    {
        if (pExceptionInfo->ContextRecord->XIP == (uintptr_t)og_fun) //Make sure we are at the address we want within the page
        {
            pExceptionInfo->ContextRecord->XIP = (uintptr_t)hk_fun; //Modify EIP/RIP to where we want to jump to instead of the original function
        }

        pExceptionInfo->ContextRecord->EFlags |= 0x100; //Will trigger an STATUS_SINGLE_STEP exception right after the next instruction get executed. In short, we come right back into this exception handler 1 instruction later
        return EXCEPTION_CONTINUE_EXECUTION; //Continue to next instruction
    }

    if (pExceptionInfo->ExceptionRecord->ExceptionCode == STATUS_SINGLE_STEP) //We will also catch STATUS_SINGLE_STEP, meaning we just had a PAGE_GUARD violation
    {
        DWORD dwOld;
        VirtualProtect((LPVOID)og_fun, 1, PAGE_EXECUTE_READ | PAGE_GUARD, &dwOld); //Reapply the PAGE_GUARD flag because everytime it is triggered, it get removes

        return EXCEPTION_CONTINUE_EXECUTION; //Continue the next instruction
    }

    return EXCEPTION_CONTINUE_SEARCH; //Keep going down the exception handling list to find the right handler IF it is not PAGE_GUARD nor SINGLE_STEP
}

bool LeoHook::AreInSamePage(const uint8_t* Addr1, const uint8_t* Addr2)
{
    MEMORY_BASIC_INFORMATION mbi1;
    if (!VirtualQuery(Addr1, &mbi1, sizeof(mbi1))) //Get Page information for Addr1
        return true;

    MEMORY_BASIC_INFORMATION mbi2;
    if (!VirtualQuery(Addr2, &mbi2, sizeof(mbi2))) //Get Page information for Addr1
        return true;

    if (mbi1.BaseAddress == mbi2.BaseAddress) //See if the two pages start at the same Base Address
        return true; //Both addresses are in the same page, abort hooking!

    return false; 
}

The hook is working fine without any problem. But it cost me a lot of FPS drop from a process that I injected. As I googled the most answer is saying reduce the amount of logic that have been use in hook. My hook method

__declspec(naked) void HookSend()
{
    __asm 
    {
        jmp dwAddress
    }
}

As you see it doesn't have much logic that include in a function. But it still cost me a lot of fps. The research number two is saying to copied all page function then modify the ASM of page function. But I have no idea how to copy a page function. So I need some guide how to copy a page function or another method to accelerate the VEH hook.

Thank you.

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