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JRuby Sandbox

The JRuby sandbox is a reimplementation of _why's freaky freaky sandbox in JRuby, and is heavily based on javasand by Ola Bini, but updated for JRuby 1.6.

Prerequisites

This gem requires JRuby 1.6. As of the time of this writing, it is known to work with the latest stable version of JRuby, 1.6.3. You can install it via RVM with the following command:

rvm install jruby-1.6.3

Building

To build the JRuby extension, run rake compile. This will build the lib/sandbox/sandbox.jar file, which lib/sandbox.rb loads.

Basic Usage

Sandbox gives you a self-contained JRuby interpreter in which to eval code without polluting the host environment.

>> require "sandbox"
=> true
>> sand = Sandbox::Full.new
=> #<Sandbox::Full:0x46377e2a>
>> sand.eval("x = 1 + 2")
=> 3
>> sand.eval("x")
=> 3
>> x
NameError: undefined local variable or method `x' for #<Object:0x11cdc190>

There's also Sandbox::Full#require, which lets you invoke Kernel#require directly for the sandbox, so you can load any trusted core libraries. Note that this is a direct binding to Kernel#require, so it will only load ruby stdlib libraries (i.e. no rubygems support yet).

Sandbox::Safe usage

Sandbox::Safe exposes an #activate! method which will lock down the sandbox, removing unsafe methods. Before calling #activate!, Sandbox::Safe is the same as Sandbox::Full.

>> require 'sandbox'
=> true 
>> sand = Sandbox.safe
=> #<Sandbox::Safe:0x17072b90> 
>> sand.eval %{`echo HELLO`}
=> "HELLO\n" 
>> sand.activate! 
>> sand.eval %{`echo HELLO`}
Sandbox::SandboxException: NoMethodError: undefined method ``' for main:Object

Sandbox::Safe works by whitelisting methods to keep, and removing the rest. Checkout sandbox.rb for which methods are kept.

Sandbox::Safe.activate! will also isolate the sandbox environment from the filesystem using FakeFS.

 >> require 'sandbox'
 => true 
 >> s = Sandbox.safe
 => #<Sandbox::Safe:0x3fdb8a73> 
 >> s.eval('Dir["/"]')
 => ["/"] 
 >> s.eval('Dir["/*"]')
 => ["/Applications", "/bin", "/cores", "/dev", etc.] 
 > s.activate!
 >> s.eval('Dir["/*"]')
 => [] 
 > Dir['/*']
 => ["/Applications", "/bin", "/cores", "/dev", etc.]

Known Issues / TODOs

  • There is currently no timeout support, so it's possible for a sandbox to loop indefinitely and block the host interpreter.