## Piston Piston is the underlying engine for running untrusted and possibly malicious code that originates from EMKC contests and challenges. It's also used in the Engineer Man Discord server via [felix bot](https://github.com/engineer-man/felix). #### Installation ``` # clone and enter repo git clone https://github.com/engineer-man/piston cd piston/lxc # install dependencies # centos: yum install -y epel-release yum install -y lxc lxc-templates debootstrap libvirt systemctl start libvirtd # ubuntu server 18.04: apt install lxc lxc-templates debootstrap libvirt0 # everything else: # not documented, please open pull requests with commands for debian/arch/macos # create and start container lxc-create -t download -n piston -- --dist ubuntu --release bionic --arch amd64 ./start # open a shell to the container ./shell # install all necessary piston dependencies echo 'source /opt/.profile' >> /opt/.bashrc echo 'export HOME=/opt' >> /opt/.profile echo 'export TERM=linux' >> /opt/.profile export HOME=/opt export TERM=linux sed -i 's/\/root/\/opt/' /etc/passwd sed -i \ 's/http:\/\/archive.ubuntu.com\/ubuntu/http:\/\/mirror.math.princeton.edu\/pub\/ubuntu/' \ /etc/apt/sources.list apt-get update apt-get install -y \ nano wget build-essential pkg-config libxml2-dev \ libsqlite3-dev mono-complete curl cmake libpython2.7-dev \ ruby # install python2 # final binary: /opt/python2/Python-2.7.17/python -V cd /opt && mkdir python2 && cd python2 wget https://www.python.org/ftp/python/2.7.17/Python-2.7.17.tar.xz unxz Python-2.7.17.tar.xz tar -xf Python-2.7.17.tar cd Python-2.7.17 ./configure # open Modules/Setup and uncomment zlib line make echo 'export PATH=$PATH:/opt/python2/Python-2.7.17' >> /opt/.profile source /opt/.profile # install python3 # final binary: /opt/python3/Python-3.8.2/python -V cd /opt && mkdir python3 && cd python3 wget https://www.python.org/ftp/python/3.8.2/Python-3.8.2.tar.xz unxz Python-3.8.2.tar.xz tar -xf Python-3.8.2.tar cd Python-3.8.2 ./configure make ln -s python python3.8 echo 'export PATH=$PATH:/opt/python3/Python-3.8.2' >> /opt/.profile source /opt/.profile # install node.js # final binary: /opt/nodejs/node-v12.16.1-linux-x64/bin/node -v cd /opt && mkdir nodejs && cd nodejs wget https://nodejs.org/dist/v12.16.1/node-v12.16.1-linux-x64.tar.xz unxz node-v12.16.1-linux-x64.tar.xz tar -xf node-v12.16.1-linux-x64.tar echo 'export PATH=$PATH:/opt/nodejs/node-v12.16.1-linux-x64/bin' >> /opt/.profile source /opt/.profile # install typescript # final binary: /opt/nodejs/node-v12.16.1-linux-x64/bin/tsc -v /opt/nodejs/node-v12.16.1-linux-x64/bin/npm i -g typescript # install golang # final binary: /opt/go/go/bin/go version cd /opt && mkdir go && cd go wget https://dl.google.com/go/go1.14.1.linux-amd64.tar.gz tar -xzf go1.14.1.linux-amd64.tar.gz echo 'export PATH=$PATH:/opt/go/go/bin' >> /opt/.profile echo 'export GOROOT=/opt/go/go' >> /opt/.profile echo 'export GOCACHE=/tmp' >> /opt/.profile source /opt/.profile # install php # final binary: /usr/local/bin/php -v cd /opt && mkdir php && cd php wget https://www.php.net/distributions/php-7.4.4.tar.gz tar -xzf php-7.4.4.tar.gz cd php-7.4.4 ./configure make make install # install rust # final binary: /opt/.cargo/bin/rustc --version curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh echo 'export PATH=$PATH:/opt/.cargo/bin' >> /opt/.profile source /opt/.profile # install swift # final binary: /opt/swift/swift-5.1.5-RELEASE-ubuntu18.04/usr/bin/swift --version cd /opt && mkdir swift && cd swift wget https://swift.org/builds/swift-5.1.5-release/ubuntu1804/swift-5.1.5-RELEASE/swift-5.1.5-RELEASE-ubuntu18.04.tar.gz tar -xzf swift-5.1.5-RELEASE-ubuntu18.04.tar.gz echo 'export PATH=$PATH:/opt/swift/swift-5.1.5-RELEASE-ubuntu18.04/usr/bin' >> /opt/.profile source /opt/.profile # install nasm # final binary: /opt/nasm/nasm-2.14.02/nasm -v cd /opt && mkdir nasm && cd nasm wget https://www.nasm.us/pub/nasm/releasebuilds/2.14.02/nasm-2.14.02.tar.gz tar -xzf nasm-2.14.02.tar.gz cd nasm-2.14.02 ./configure make echo 'export PATH=$PATH:/opt/nasm/nasm-2.14.02' >> /opt/.profile source /opt/.profile # install java # final binary: /opt/java/jdk-14/bin/java -version cd /opt && mkdir java && cd java wget https://download.java.net/java/GA/jdk14/076bab302c7b4508975440c56f6cc26a/36/GPL/openjdk-14_linux-x64_bin.tar.gz tar -xzf openjdk-14_linux-x64_bin.tar.gz echo 'export PATH=$PATH:/opt/java/jdk-14/bin' >> /opt/.profile source /opt/.profile # create runnable users and apply limits for i in {1..150}; do useradd -M runner$i usermod -d /tmp runner$i echo "runner$i soft nproc 64" >> /etc/security/limits.conf echo "runner$i hard nproc 64" >> /etc/security/limits.conf echo "runner$i soft nofile 2048" >> /etc/security/limits.conf echo "runner$i hard nofile 2048" >> /etc/security/limits.conf done # cleanup rm -rf /home/ubuntu chmod 777 /tmp # leave container exit # optionally run tests cd ../tests ./test_all_lxc ``` #### CLI Usage - `lxc/execute [language] [file path] [arg]...` #### API Usage To use the API, it must first be started. To start the API, run the following: ``` cd api ./start ``` The Piston API exposes one endpoint at `http://127.0.0.1:2000/execute`. This endpoint takes the following JSON payload and expects at least the language and source. If source is not provided, a blank file is passed as the source. ```json { "language": "js", "source": "console.log(process.argv)", "args": [ "1", "2", "3" ] } ``` A typical response when everything succeeds will be similar to the following: ```json { "ran": true, "language": "js", "version": "12.13.0", "output": "[ '/usr/bin/node',\n '/tmp/code.code',\n '1',\n '2',\n '3' ]" } ``` If an invalid language is supplied, a typical response will look like the following: ```json { "code": "unsupported_language", "message": "whatever is not supported by Piston" } ``` #### Supported Languages Currently python2, python3, c, c++, go, node, ruby, r, c#, nasm, php, java, swift, brainfuck, rust, bash, awk, and typescript is supported. #### Principle of Operation Piston utilizes LXC as the primary mechanism for sandboxing. There is a small API written in Go which takes in execution requests and executes them in the container. High level, the API writes a temporary source and args file to `/tmp` and that gets mounted read-only along with the execution scripts into the container. The source file is either ran or compiled and ran (in the case of languages like c, c++, c#, go, etc.). #### Security LXC provides a great deal of security out of the box in that it's separate from the system. Piston takes additional steps to make it resistant to various privilege escalation, denial-of-service, and resource saturation threats. These steps include: - Disabling outgoing network interaction - Capping max processes at 64 (resists `:(){ :|: &}:;`, `while True: os.fork()`, etc.) - Capping max files at 2048 (resists various file based attacks) - Mounting all resources read-only (resists `sudo rm -rf --no-preserve-root /`) - Running as a variety of unprivileged users - Capping runtime execution at 3 seconds - Capping stdout to 65536 characters (resists yes/no bombs and runaway output) - SIGKILLing misbehaving code #### License Piston is licensed under the MIT license.