Piston

A high performance general purpose code execution engine.

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About • Public API • Getting Started • Usage • Supported Languages • Principles • Security • License

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About

Piston is a high performance general purpose code execution engine. It excels at running untrusted and possibly malicious code without fear from any harmful effects.

It's used in numerous places including:

• EMKC Challenges,
• EMKC Weekly Contests,
• Engineer Man Discord Server,
• I Run Code (Discord Bot) bot as well as 1300+ other servers and 100+ direct integrations.

To get it in your own server, go here: https://emkc.org/run.

Public API

• Requires no installation and you can use it immediately.
• Reference the Versions/Execute sections below to learn about the request and response formats.

When using the public Piston API, use the base URL:

https://emkc.org/api/v1/piston

GET

https://emkc.org/api/v1/piston/versions

POST

https://emkc.org/api/v1/piston/execute

Important Note: The Piston API is rate limited to 5 requests per second. If you have a need for more requests than that and it's for a good cause, please reach out to me (EngineerMan#0001) on Discord so we can discuss potentially getting you an unlimited key.

Getting Started

Host System Package Dependencies

• NodeJS
• lxc
• libvirt

If your OS is not documented below, please open pull requests with the correct commands for your OS.

CentOS / RHEL

curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.37.2/install.sh | bash
nvm install --lts
nvm use --lts

yum install -y epel-release
yum install -y lxc lxc-templates debootstrap libvirt
systemctl start libvirtd

Ubuntu (18.04)

curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.37.2/install.sh | bash
nvm install --lts
nvm use --lts

apt install -y lxc lxc-templates debootstrap libvirt0

Arch Linux

curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.37.2/install.sh | bash
nvm install --lts
nvm use --lts

sudo pacman -S lxc libvirt unzip

After system dependencies are installed, clone this repository:

# clone and enter repo
git clone https://github.com/engineer-man/piston
cd piston/lxc

Installation (simple)

• Coming soon.

Installation (advanced)

• See var/install.txt for how to create a new LXC container and install all of the required software.

Usage

CLI

lxc/execute [language] [file path] [args]

API

To use the API, it must first be started. Please note that if root is required to access LXC then the API must also be running as root. To start the API, run the following:

cd api
./start

For your own local installation, the API is available at

http://127.0.0.1:2000

Versions Endpoint

GET /versions This endpoint takes no input and returns a JSON array of the currently installed languages.

Truncated response sample:

HTTP/1.1 200 OK
Content-Type: application/json

[
    {
        "name": "awk",
        "version": "1.3.3"
    },
    {
        "name": "bash",
        "version": "4.4.20"
    },
    {
        "name": "c",
        "version": "7.5.0"
    }
]

Execute Endpoint

POST /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. If no args are desired, it can either be an empty array or left out entirely.

{
    "language": "js",
    "source": "console.log(process.argv)",
    "args": [
        "1",
        "2",
        "3"
    ]
}

A typical response upon successful execution will contain the language, version, output which is a combination of both stdout and stderr but in chronological order according to program output, as well as separate stdout and stderr.

HTTP/1.1 200 OK
Content-Type: application/json

{
    "ran": true,
    "language": "js",
    "version": "12.13.0",
    "output": "[ '/usr/bin/node',\n  '/tmp/code.code',\n  '1',\n  '2',\n  '3' ]",
    "stdout": "[ '/usr/bin/node',\n  '/tmp/code.code',\n  '1',\n  '2',\n  '3' ]",
    "stderr": ""
}

If an invalid language is supplied, a typical response will look like the following:

HTTP/1.1 400 Bad Request
Content-Type: application/json

{
    "code": "unsupported_language",
    "message": "whatever is not supported by Piston"
}

Supported Languages

awk	julia
bash	kotlin
brainfuck	lua
c	nasm
cpp	node
csharp	paradoc
deno	perl
erlang	php
elixir	python2
emacs	python3
elisp	ruby
go	rust
haskell	swift
java	typescript
jelly

Principle of Operation

Piston utilizes LXC as the primary mechanism for sandboxing. There is a small API written in Node 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 /)
• Cleaning up all temp space after each execution (resists out of drive space attacks)
• 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.