Information

A simple tool to hijack processes when they start.

LDTK expects to be loaded as a dynamic library using the LD_PRELOAD environment variable within a shell (such as Bash or Zsh). In its initialization code, the library will mess with the hijacked program's memory and functions.

Tutorial

Installation

This program is only supported on Linux.

Using A Pre-Built Binary

If you are using Linux and a x86_64 CPU, you can use the pre-built binary available in github releases.

Building From Source

To build LDTK from source, you'll need cargo (and a recent-enough version of the Rust toolchain), as well as nasm to compile .asm files.

git clone git@github.com:nils-mathieu/ldtk.git
cd  ldtk
cargo build --release

The output binary will be located in your default target location, usually target/release/libldtk.so.

Usage

Either you want the tool to be loaded in every program you start, in which case you can export the LD_PRELOAD environment variable.

export LD_PRELOAD=path/to/libldtk.so

Or you can try it on a single process, using this syntax (works in sh-like shells):

LD_PRELOAD=path/to/libldtk.so cat Cargo.toml

Configuration

LDTK looks for the LDTK_ACTION environment variable to determine what to do. Here is the list of supported actions.

When no LDTK_ACTION is specified, or when the action is not recognized, nothing happens.

Mute

When LDTK_ACTION is "mute", LDTK hijacks libc's write function and make it do nothing for file descriptors 1 and 2 (standard output and standard error), ensuring that nothing is ever displayed to the terminal.

Writing to files is intentionally preserved, however.

Example:

 >_ LD_PRELOAD=path/to/libldtk.so LDTK_ACTION=mute cat Cargo.toml

Spawn

When LDTK_ACTION is "spawn", LDTK simply invoke a command using the /bin/sh shell. The executed command is taken from the LDTK_SPAWN environment variable.

Example:

 >_ LD_PRELOAD=path/to/libldtk.so LDTK_ACTION=spawn LDTK_SPAWN="echo abc | rev" cat Cargo.toml
cba
[package]
name = "ldtk"
...

Here, the /bin/sh -c "echo abc | rev" process has been invoked.

Examples

Mute all programs.

export LD_PRELOAD=path/to/lib ldtk.so
export LDTK_ACTION=mute

Print a message before every command.

export LD_PRELOAD=path/to/lib ldtk.so
export LDTK_ACTION=spawn
export LDTK_SPAWN="echo i'm in ur address space"

Wait a bit before actually starting.

export LD_PRELOAD=path/to/lib ldtk.so
export LDTK_ACTION=spawn
export LDTK_SPAWN="sleep 1"