Rhook

Hook libc functions with an easy API

Usage

1- Import the trait [RunHook]

2- Create an Command with Command::new and add hooks to it via add_hook and add_hooks methods

3- Confirm the hooks with set_hooks method this step is necessary

4- Now you can carry on with the usual Command methods (output, spawn,status,..)

Example

Say you want to limit the bandwidth of a program

Usually downloading calls libc::recv function

So our goal is to throttle it with a simple sleep

To do that with this crate: (taking speedtest program as an example)

1- Check its manpage https://man7.org/linux/man-pages/man2/recv.2.html to see what is the function's input/output

2- use this crate

use rhook::{RunHook, Hook};

std::process::Command::new("speedtest").add_hook(Hook::Recv(stringify!(|sockfd, buf, len, flags|{
 std::thread::sleep_ms(10);
 original_recv(sockfd, buf, len, flags)
}))).set_hooks().unwrap().spawn();

Thats it! Note that you have acess inside the closure to the original function denoted by the prefix original_ + the function name

Couple of points:

• If you take ownership of an input value inside of the closure, be sure to use ManuallyDrop so you don't free it

• To check if a program dynamicly loads libc use ldd $path_to_program

• To check what libc functions a program calls use nm -D $path_to_program

Check out the tests for more examples

License: MIT