Jirachi

An General Purpose Cross Platform Java Native Interface hook library Written in Pure C

Preview

Important

Android Runtime Limitations

This project does not use standard Android JVMTI. Android relies on a custom runtime implementation known as ART TI.

• ART TI support is limited to SDK 26 (Android 8.0) and above
• The native library must be loaded as an agent before the Application context is created
• This requires early initialization (e.g. via a ContentProvider)
• Agent loading depends on Android SDK internals (Debug.java)

Android compatibility is currently broken

• The project is not functional on Android at this time
• A proper Android binding has not yet been implemented
• Android support will be added in a future release

This behavior is undocumented, unsupported, and may break across Android versions, OEM ROMs, or security updates.

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Building the Project

This project uses CMake and supports Windows, Linux, and macOS. Android builds are not supported.

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Requirements

• CMake 3.12 or newer

• A C compiler

  • Windows: MSVC or MinGW
  • Linux/macOS: GCC or Clang

• Java Development Kit (JDK)

• JAVA_HOME environment variable pointing to a valid JDK installation

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Verify Prerequisites

cmake --version
javac -version

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Step 1: Configure JAVA_HOME

Windows (PowerShell)

$env:JAVA_HOME="C:\Program Files\Java\jdk-23"

Linux / macOS

export JAVA_HOME=/path/to/jdk

JAVA_HOME must reference a full JDK, not a JRE.

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Step 2: Configure the Build

From the project root directory, run:

cmake -S . -B build \
  -DCMAKE_BUILD_TYPE=Release \
  -DJNIHOOK_BUILD_SHARED=ON \
  -DJNIHOOK_BUILD_STATIC=ON \
  -DJNIHOOK_BUILD_TESTS=OFF

This step:

• Detects the host platform
• Locates JNI headers using JAVA_HOME
• Generates build files in the build directory

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Step 3: Build the Project

cmake --build build

For parallel builds:

cmake --build build -j

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Build Outputs

After a successful build, the following artifacts are produced:

Platform	Output Files
Windows	jnihook.dll, jnihook.lib, jnihook_static.lib
Linux	libjnihook.so, libjnihook.a
macOS	libjnihook.dylib, libjnihook.a

All outputs are located in the build directory.

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Optional: Build with Tests

cmake -S . -B build \
  -DJNIHOOK_BUILD_TESTS=ON \
  -DJNIHOOK_RUN_TESTS_AUTO=ON

cmake --build build

When enabled, tests are executed automatically after the build completes.

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Optional: Install

cmake --build build --target install

This installs:

• Header files to include/jnihook
• Libraries to lib
• CMake package configuration to lib/cmake/jnihook

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CLion Usage

1. Clone the repository:

   git clone https://github.com/Kitsuri-Studios/Jirachi

2. Open CLion

3. Select Open and choose the project root directory

4. CLion will automatically:

   • Detect the CMakeLists.txt
   • Configure the project
   • Generate build files

5. Use the Build or Run actions to compile the project

Ensure JAVA_HOME is set before launching CLion.

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Disclaimer

This library is created strictly for research purposes. Any harm caused by its use is not the responsibility of the authors. It is strongly recommended not to use this library for any illegal or pirated activities.

License

This project is licensed under BSD 3-Clause License.
Summary: You are free to use, modify, and distribute the code, but you cannot use the names of the authors for promotion, and there is no warranty.