hooklib's Introduction

HookLib

The Win32 lightweight functions interception library

✔ Advantages:

Written on pure C
Extremely lightweight
Based on the fastest and lightweight Zydis disassembler
Uses only NativeAPI functions
Has no other dependencies
Kernelmode support
Supports instructions relocation and thread's contexts fixup

⚙️ How it works:

TargetFunction():                                 ^ ; return
-> jmp Interceptor ------> Interceptor():         |
   ??? ; Broken bytes        ... Handler code ... |
   ... ; Continuation <--+   CallOriginal() ------|--> OriginalBeginning():
   ...         +---------|-> ...                  |      ... Original beginning ...
   ret --------+         |   ret -----------------+      ... of TargetFunction ...
                         +------------------------------ jmp Continuation

🧱 Trampolines:

Types:

E9 44 33 22 11 | jmp 0x11223344 - Relative jump to the +-2Gb
FF 25 00 00 00 00 88 77 66 55 44 33 22 11 | jmp [rip+00h] - Absolute jump to the address stored after the jmp as raw bytes (4 bytes in x32 and 8 bytes in x64)

x32:

jmp rel Interceptor only one

x64:

jmp rel Interceptor if Abs(Interceptor - Target) <= 2Gb
jmp rel Intermediate -> jmp abs Interceptor if Abs(Interceptor - Target) > 2Gb and we have free space for the intermediate trampoline buffer
jmp abs Interceptor if we have no free space for the intermediate buffer in +- 2Gb interval

🧵 Using:

Open the HookLib.sln and build it.
Add Zydis.lib, HookLib.lib and HookLib.h to your project.

#include <cstdio>

#include <Windows.h>

#include <HookLib.h>
#pragma comment(lib, "Zydis.lib")
#pragma comment(lib, "HookLib.lib")

using _ExitProcess = VOID(WINAPI*)(ULONG ExitCode);
_ExitProcess OriginalExitProcess = NULL;
VOID WINAPI ExitProcessHook(ULONG ExitCode)
{
    printf("ExitCode: %ul\r\n", ExitCode);
    RemoveHook(OriginalExitProcess);
    ExitProcess(0);
}

int main()
{
    PVOID Target = GetProcAddress(GetModuleHandle(L"kernel32.dll"), "ExitProcess");
    SetHook(Target, ExitProcessHook, reinterpret_cast<PVOID*>(&OriginalExitProcess));
    ExitProcess(0);
    return 0;
}

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