HookLib²
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
📰 What's new in the 2nd Gen:
- The HookLib was completely rewritten
- Extremely reduced allocations, processes/threads enumerations and handles manipulations count
- Multihook/multiunhook support that hooks/unhooks multiple functions in one session
- Extremely reduced memory consumption for usermode hooks: one hook page (4Kb) can hold 39 cells for nearest hooks that removes the need to allocate one page per each hook
- Support of KM->UM hooks (even with support of contexts fixup directly from kernelmode):
- KM:Amd64 -> UM:Amd64
- KM:Amd64 -> UM:Wow64
- KM:i386 -> UM:i386
🔬 How it works:
TargetFunction(): ^ ; return
-> jmp Interceptor ------> Interceptor(): |
??? ; Broken bytes ... Handler code ... |
... ; Continuation <--+ CallOriginal() ------|--> OriginalBeginning():
... +---------|-> ... | ... Original beginning ...
ret --------+ | ret -----------------+ ... of TargetFunction ...
+------------------------------ jmp Continuation
🧵 Trampolines:
Supported trampolines:
Jump to a relative offset:
E9 44 33 22 11 | jmp rip+0x11223344 ; Relative jump to ±2Gb only
Jump to an absolute address (x32):
FF 25 00 00 00 00 | jmp [eip+00h]
44 33 22 11 | <- EIP is points to
Jump to an absolute address (x64):
FF 25 00 00 00 00 | jmp [rip+00h]
88 77 66 55 44 33 22 11 | <- RIP is points to
Trampolines selection logic:
if (relative_jumpable(fn, handler))
{
set_relative_jump(fn, handler);
}
else
{
/*
'Intermediate' is an intermediate buffer that allocates
in the same block with the function beginning:
*/
if (relative_jumpable(fn, intermediate))
{
set_relative_jump(fn, intermediate);
set_absolute_jump(intermediate, handler);
}
else
{
set_absolute_jump(fn, handler);
}
}
🪡 Usage:
Add the HookLib.vcxproj to your .sln and add the reference to the HookLib project into your project references list as described here: select project, open the project menu, click Add -> Reference and select the HookLib.
Then add ./HookLib/HookLib/ folder to your header folders list and you're good to go.
#include <HookLib.h>
int func(int a, int b)
{
return a + b;
}
int handler(int a, int b)
{
return a * b;
}
template <typename Fn>
Fn hookFunc(Fn fn, Fn handler)
{
return static_cast<Fn>(hook(fn, handler));
}
void testSimpleHook()
{
const auto orig = hookFunc(func, handler);
assert(func(2, 3) == 6); // Hooked, the 'handler' will be called instead
assert(orig(2, 3) == 5);
unhook(orig);
assert(func(2, 3) == 5);
}
void testCppHelpers()
{
const auto holder = HookFactory::install(func, handler);
assert(func(2, 3) == 6);
assert(holder.call(2, 3) == 5);
}
int main()
{
testSimpleHook();
testCppHelpers();
return 0;
}