• Introduction
• How to use
• License
• Version history
• Acknowledgements

This library was created as a free alternative to Microsoft Detours. It is originally developed by Marton Anka and currently is supported and developed by Apriorit.

// Include a header
#include <mhook-lib/mhook.h>

// Save the original function
typedef ULONG (WINAPI* _NtClose)(IN HANDLE Handle);
_NtClose TrueNtClose = (_NtClose)GetProcAddress(GetModuleHandle(L"ntdll"), "NtClose");

// Declare your function that will be handle a hook:
ULONG WINAPI HookNtClose(HANDLE hHandle) 
{
    printf("***** Call to NtClose(0x%p)\n", hHandle);
    return TrueNtClose(hHandle);
}

//...

// Set the hook 
BOOL isHookSet = Mhook_SetHook((PVOID*)&TrueNtClose, HookNtClose);

//...

// After finishing using the hook – remove it
Mhook_Unhook((PVOID*)&TrueNtClose);

You can also set a bunch of hooks in one call:

HOOK_INFO hooks[] =
{
    { (PVOID*)&TrueNtOpenProcess, HookNtOpenProcess },
    { (PVOID*)&TrueSelectObject, HookSelectobject },
    { (PVOID*)&Truegetaddrinfo, Hookgetaddrinfo },
    { (PVOID*)&TrueHeapAlloc, HookHeapAlloc },
    { (PVOID*)&TrueNtClose, HookNtClose }
};

int numberOfSetHooks = Mhook_SetHookEx(hooks, 5);
    
//...

// Removing hooks
int numberOfRemovedHooks = Mhook_UnhookEx(hooks, 5);

That way of setting multiple hooks is also much better in performance.

Mhook is freely distributed under an MIT license.

• Fix #1: VirtualAlloc hooking reports anomaly
• New #2: Add integration to vcpkg package
• New #3: Add AppVeyor CI
• Fix #4: Add ability to hook functions with call in first 5 bytes

• 10x performance boost
• CMake build system
• Change tabs to spaces
• Ability to hook functions with je/jne in the first 5 bytes
• Fix hook recursion
• Other fixes

• A number of improvements: hot patch location (mov edi, edi) handling, support for REX-prefixed EIP-relative jumps on x64, removal of compile-time limit on the number of hooks

• A bugfix that allows hooking more API functions

• Support for instructions using IP-relative addressing

• Fixes

• Built-in disassembler

• Original release

Mhook contains a disassembler that is a stripped-down version of the excellent tDisasm package by Matt Conover. Thank you Matt! tDisasm comes with a BSD-style license and re-releasig a derivative of it under the MIT license has been confirmed to be OK by its author.

Alexandr Filenkov submitted bugfixes in Sept-2007. Michael Syrovatsky submitted fixes for IP-relative addressing in Jun-2008. Andrey Kubyshev submitted a bugfix in Jul-2011 and Jan-2013. John McDonald enabled unlimited hooks. Kasper Brandt provided a fix for hot patch function prologues.