Awesome

emcc-obf

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This repository contains a modified version of the Emscripten compiler that includes an LLVM-based obfuscator. Specifically, it uses the Hikari obfuscator which is based on the obfuscator-llvm project.

Disclaimer: Some of the documentation is translated from 中文 to the best of my ability, sorry!

Table of Contents

• Usage
  • Flags
  • Environment Variables
• Building
  • Building with Docker
  • Building from Source
    • Dependencies
    • Building LLVM
    • Building Binaryen
    • Configure Emscripten
• License

Usage

The flags operate at the LLVM-level and have to be passed to Emscripten through the -mllvm flag. For instance, if you want to add bogus control flow and set the probability to 100% for each basic block, you would have to do:

emcc -mllvm -enable-bcfobf -mllvm -bcf_prob 100 <file>.c

To only obfuscate certain functions, see Function Annotations.

Note: You may need to turn off optimization so that the obfuscation is not optimized away by the compiler.

Flags

Environment variables

Building

Building with Docker

docker build -t emcc-obf .
docker run -it emcc-obf

Building from source

Emscripten does not require compilation as it uses Python. However, the LLVM (which provides Clang and wasm-ld) and Binaryen components need to be compiled. Once compiled, you can simply modify the .emscripten file to specify the correct paths for these tools using the LLVM_ROOT and BINARYEN_ROOT variables. These variables may already be correct depending on the output of emcc --generate-config. Also, for convenience the Emscripten folder should be added to your path.

Note that ninja install installs the compiled binaries in the appropriate directories (usually /usr/local/bin), which may conflict with existing installations. If you've already installed LLVM and Binaryen, omit the ninja install command and edit the .emscripten file accordingly.

Dependencies

Building locally requires the following dependencies:

• gcc
• cmake
• ninja
• nodejs
• python3

Building LLVM

git clone --recursive -b llvm-16.0.0rel https://github.com/61bcdefg/Hikari-LLVM15.git hikari
cd hikari
git submodule update --remote --recursive
mkdir build && cd build
cmake -G "Ninja" -DCMAKE_BUILD_TYPE=MinSizeRel -DLLVM_APPEND_VC_REV=on -DLLVM_ENABLE_PROJECTS='lld;clang' -DLLVM_TARGETS_TO_BUILD="host;WebAssembly" -DLLVM_INCLUDE_EXAMPLES=OFF -DLLVM_INCLUDE_TESTS=OFF -DENABLE_LLVM_SHARED=1 ../llvm
ninja && ninja install

Building Binaryen

git clone https://github.com/WebAssembly/binaryen.git binaryen
cd binaryen
git checkout ecbebfbee12f2f25af648119604915fc37427f6f
git submodule init
git submodule update
mkdir build && cd build
cmake -G "Ninja" ..
ninja && ninja install

Configure emscripten

git clone https://github.com/emscripten-core/emscripten.git emscripten
git checkout fab93a2bff6273c882b0c7fb7b54eccc37276e03
emcc --generate-config
npm i

License

See Hikari/License.