Local Go Playground

Introduction

Playground is a web application that executes arbitrary Go code locally. This tool provides the ability to save and load various code snippets, the ability to run Go code using arbitrary third-party packages, and the ability to run tests and benchmarks.

Since the Playground executes arbitrary Go code on the server it is running from, there are obvious security implications. As a baseline, the Playground requires a password in order use the service. However, anyone using this is responsible for adding extra layers of security themselves:

• Consider running playground from a Linux Container or from a dedicated VM to sandbox the process.
• Consider using a web server (like Caddy) to provide automatic HTTPS and another layer of authentication.

Running the server is only supported on Linux and OSX.

Basic Usage

Build the server:

go get -u github.com/dsnet/playground

Start the server (assuming $GOPATH/bin is in your $PATH):

$ playground
Enter a new Playground login password: ...
2017/05/11 18:07:07 main.go:184: loaded config:
{
	"ServeAddress": "localhost:8080",
	"PasswordSalt": "c9c8959441f5a49e0fed99a9a0704ef0725786b318304088fee0b9b1299a68f3",
	"PasswordHash": "ec3c17aba3fa603bc443e82b748db059bf294d9d3d9f975e15e9598241671af7",
	"DataPath": "/home/rawr/.playground",
	"GoBinary": "go",
	"FmtBinary": "goimports",
	"BinaryVersion": "Git+7ed13d2, Fri May 12 00:35:19 2017",
	"BinarySHA256": "c026207e6ff152e4f5b7be4a098577f164fed983650389a971a205384f5829aa"
}
2017/05/11 18:07:07 main.go:254: playground starting on localhost:8080
...

When running playground without a configuration file, it requires a password to be supplied. The Playground can be interacted with by visiting http://localhost:8080 in a browser.

The Playground executes arbitrary snippets of Go code. Each code snippet is an individual Go program and will be executed as either an executable or a test suite. The presence of a main function or any Test or Benchmark functions determine what type of program it is. These functions cannot be mixed; that is, only one type or the other may exist within the snippet. Lastly, all snippets must be within the main package.

Advanced Usage

Typically, playground is started as a background service; in which case, a configuration file should be provided. An example configuration file is:

{
	"ServeAddress": "localhost:8080",
	"LogFile": "daemon.log",
	"PasswordSalt": "ed1b3112286780279e740612b0a03f2c0d1550d5e7d2197c636b5d3eb6ee51b2",
	"PasswordHash": "4ef6b693629568e78ad0846ee189c8e9fdf719fbe631650ad547192d9c3490ba",
	"DataPath": "/usr/local/playground",
	"GoBinary": "go",
	"FmtBinary": "goimports",
	"Environment": {
		"PATH": "/usr/local/bin:/usr/bin:/bin",
		"GOPATH": "/path/to/gopath",
	},
}

The password fields consists of a randomly generated salt and a hashed version of the actual password. This pair of values can be generated with the following shell script:

#!/bin/bash
read -s -p "Password: " PASSWORD && echo
PASSWORD_SALT=$(head -c 1024 /dev/urandom | sha256sum | head -c 64)
PASSWORD_HASH=$(echo -n "$(echo $PASSWORD_SALT | xxd -r -p)${PASSWORD}" | sha256sum | head -c 64)
echo -en "PasswordSalt: $PASSWORD_SALT\nPasswordHash: $PASSWORD_HASH\n"
unset PASSWORD PASSWORD_SALT PASSWORD_HASH

See the Help in main.go for more details about configuration options.

See the Help in web interface for more details about using the Playground.