ba0f3 / subhook.nim

subhook wrapper for Nim https://github.com/Zeex/subhook

subhook.nim

subhook wrapper for Nim https://github.com/Zeex/subhook

Usage

import subhook, subhook/helpers


proc recv(s: SOCKET, buf: cstring, len: int32, flags: int32): int32 {.fptr.} = 0x123456

proc MY_recv(s: SOCKET, buf: cstring, len: int32, flags: int32): int32 {.stdcall.} =
  discard

let hook = initHook(recv, MY_recv)
if hook.install() != 0:
  quit "Unable to install revc hook"

Trampoline example:

import subhook

proc add2(a, b: int): int =
  result = a + b
  echo "add2 result = ", result

var addHook: Hook
proc double_add2(a, b: int): int =
  echo "add called"
  result = cast[typeof(add2)](addHook.getTrampoline())(a, b) * 2


addHook = initHook(add2, double_add2, true)

assert add2(1, 3) == 8

subhook.nim's Issues

Trampoline Example doesn't works

The current example looks like:

import subhook

proc add2(a, b: int): int =
  result = a + b
  echo "add2 result = ", result

var addHook: Hook
proc double_add2(a, b: int): int =
  echo "add called"
  result = cast[typeof(add2)](addHook.getTrampoline())(a, b) * 2


addHook = initHook(add2, double_add2, true)

assert add2(1, 3) == 8

Which seem to have following issues:

• true doesn't seems to be a valid flag
• addHook doesn't gets installed

This example would make it compileable:

import subhook

proc add2(a, b: int): int =
  result = a + b
  echo "add2 result = ", result

var addHook: Hook

proc double_add2(a, b: int): int =
  echo "add called"
  result = cast[typeof(add2)](addHook.getTrampoline())(a, b) * 2


addHook = initHook(add2, double_add2, SUBHOOK_64BIT_OFFSET)
addHook.install()

echo add2(1, 3)

However this doesn't returns the expected values:
-d: debug:

add called
add2 result = 72057594053006481
144115188106012962

-d:release:

add2 result = 4
4

Crashing process

Hello, I am having this issue when trying to hook keyboard input in the game (using dll injection).

Here is my code:

import winim
import subhook

type KeymapHook = proc(key: UINT_PTR, held: bool) {.thiscall.}

var keymapHook*: Hook

proc keymapDetour(key: UINT_PTR, held: bool) = 
    cast[KeymapHook](keymapHook.getTrampoline())(key, held)

proc initKeyboardHook() = 
    var baseAddr = GetModuleHandleA("Minecraft.Windows.exe")
    keymapHook = initHook(
        cast[pointer](baseAddr + 0x1BE780),
        cast[pointer](cast[ByteAddress](keymapDetour)),
        true,
        SUBHOOK_64BIT_OFFSET
    )

When the dll injected, everything is working fine, which means that dll initialization was successful.
Game is crashing when the key on the keyboard is pressed. And btw, when detour function is empty, keyboard is not working, which means the hook address is right.
There is something wrong when calling the original function to unlock the keyboard.

Example of using getTrampoline?

Hey,

thank you for that bindings. I was pretty surprised that a hooking library is done in nim. =)

So using it with the usual detour works fine:

UserCode
hook.remove()
originalProc()
hook.install()

But once I try to use the trampoline it crashes for me. Im injecting a library into another process. My attempt was:

UserCode
cast[typeof(originalProc)](hook.getTrampoline())(args)