2015-01-16 13:23:52 +00:00
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[![Build Status][build_status]][build]
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2015-02-16 16:04:57 +00:00
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[![Build Status - Windows][build_status_win]][build_win]
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2015-01-15 17:45:26 +00:00
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2018-08-31 18:29:09 +00:00
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SubHook is a super-simple hooking library for C and C++ that works on Windows,
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Linux and macOS. It supports x86 only (32-bit and 64-bit).
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2013-06-26 07:15:37 +00:00
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2018-09-01 11:19:53 +00:00
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Installation
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------------
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Simply copy the files to your project and include subhook.c in your build.
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The other source files wil be `#included` by the main C file automatically
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depending on the OS and achitecture.
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Use of CMake is not mandatory, the library can be built wihtout it (no extra
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build configuration required).
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2013-01-13 17:02:16 +00:00
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Examples
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--------
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2013-09-26 20:44:02 +00:00
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In the following examples `foo` is some function or a function pointer that
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takes a single argument of type `int` and uses the same calling convention
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as `my_foo` (depends on compiler).
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2013-01-14 21:40:12 +00:00
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2014-11-26 18:07:51 +00:00
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### Basic usage
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2013-01-13 17:02:16 +00:00
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2013-01-16 09:15:57 +00:00
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```c
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2013-01-14 21:40:12 +00:00
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#include <stdio.h>
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2013-01-13 17:02:16 +00:00
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#include <subhook.h>
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2013-12-05 17:00:59 +00:00
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subhook_t foo_hook;
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2013-01-13 17:02:16 +00:00
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2013-01-14 21:40:12 +00:00
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void my_foo(int x) {
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2014-11-26 18:07:51 +00:00
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/* Remove the hook so that you can call the original function. */
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2013-01-13 17:02:16 +00:00
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subhook_remove(foo_hook);
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2013-01-14 21:40:12 +00:00
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printf("foo(%d) called\n", x);
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foo(x);
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2013-01-13 17:02:16 +00:00
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2014-11-26 18:07:51 +00:00
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/* Install the hook back to intercept further calls. */
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subhook_install(foo_hook);
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}
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int main() {
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2014-11-26 18:07:51 +00:00
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/* Create a hook that will redirect all foo() calls to to my_foo(). */
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2016-08-15 14:05:37 +00:00
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foo_hook = subhook_new((void *)foo, (void *)my_foo, 0);
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2013-01-13 17:02:16 +00:00
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2014-11-26 18:07:51 +00:00
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/* Install it. */
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subhook_install(foo_hook);
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2013-12-04 19:04:59 +00:00
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2014-11-26 18:07:51 +00:00
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foo(123);
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/* Remove the hook and free memory when you're done. */
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subhook_remove(foo_hook);
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2013-01-13 17:06:51 +00:00
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subhook_free(foo_hook);
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2013-01-13 17:02:16 +00:00
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}
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```
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2014-11-26 18:07:51 +00:00
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### Trampolines
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Using trampolines allows you to jump to the original code without removing
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and re-installing hooks every time your function gets called.
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```c
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typedef void (*foo_func)(int x);
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void my_foo(int x) {
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printf("foo(%d) called\n", x);
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/* Call foo() via trampoline. */
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((foo_func)subhook_get_trampoline(foo_hook))(x);
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}
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int main() {
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/* Same code as in previous example. */
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}
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```
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2016-08-15 14:05:37 +00:00
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Please note that subhook has a very simple length disassmebler engine (LDE)
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that works only with most common prologue instructions like push, mov, call,
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etc. When it encounters an unknown instruction subhook_get_trampoline() will
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return NULL.
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2014-11-26 18:07:51 +00:00
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2013-01-13 17:02:16 +00:00
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### C++
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2013-01-16 09:15:57 +00:00
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```c++
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#include <iostream>
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#include <subhook.h>
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2016-08-15 14:05:37 +00:00
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subhook::Hook foo_hook;
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subhook::Hook foo_hook_tr;
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2014-11-26 18:07:51 +00:00
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typedef void (*foo_func)(int x);
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2013-01-14 21:40:12 +00:00
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void my_foo(int x) {
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2016-08-15 14:05:37 +00:00
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// ScopedHookRemove removes the specified hook and automatically re-installs
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// it when the objectt goes out of scope (thanks to C++ destructors).
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subhook::ScopedHookRemove remove(&foo_hook);
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2013-01-13 17:02:16 +00:00
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2017-06-19 03:49:40 +00:00
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std::cout << "foo(" << x << ") called" << std::endl;
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2014-11-26 18:07:51 +00:00
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foo(x + 1);
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2013-01-13 17:02:16 +00:00
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}
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2014-11-26 18:07:51 +00:00
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void my_foo_tr(int x) {
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2017-06-19 03:49:40 +00:00
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std::cout << "foo(" << x << ") called" << std::endl;
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2014-11-26 18:07:51 +00:00
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// Call the original function via trampoline.
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((foo_func)foo_hook_tr.GetTrampoline())(x + 1);
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2013-01-13 17:02:16 +00:00
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}
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2014-11-26 18:07:51 +00:00
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int main() {
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foo_hook.Install((void *)foo, (void *)my_foo);
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foo_hook_tr.Install((void *)foo, (void *)my_foo_tr);
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2014-11-26 18:07:51 +00:00
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}
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2013-01-13 17:02:16 +00:00
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```
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2013-01-14 21:40:12 +00:00
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2018-08-31 18:51:43 +00:00
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Known issues
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------------
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* If a target function (the function you are hooking) is less than N bytes
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in length, for example if it's a short 2-byte jump to a nearby location
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(sometimes compilers generate code like this), then you will not be able
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to hook it.
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N is 5 by default (1-byte jmp opcode + 32-bit offset), but it you enable
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the use of 64-bit offsets in 64-bit mode N becomes 14 (see the definition
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of `subhook_jmp64`).
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* Some systems protect executable code form being modified at runtime, which
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will not allow you to install hooks, or don't allow to mark heap-allocated
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memory as executable, which prevents the use of trampolines.
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For example, on Fedora you can have such problems because of SELinux (though
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you can disable it or exclude your files).
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2015-03-22 10:49:31 +00:00
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License
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-------
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Licensed under the 2-clause BSD license.
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2015-01-16 13:23:52 +00:00
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[build]: https://travis-ci.org/Zeex/subhook
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[build_status]: https://travis-ci.org/Zeex/subhook.svg?branch=master
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2015-02-16 16:04:57 +00:00
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[build_win]: https://ci.appveyor.com/project/Zeex/subhook/branch/master
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[build_status_win]: https://ci.appveyor.com/api/projects/status/q5sp0p8ahuqfh8e4/branch/master?svg=true
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