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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.

screenshot

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.