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 1.7.

This gem was developed against JRuby 1.7.6, and is known to work with 1.7.8, but has not been tested against other versions, so proceed at your own risk. The Travis CI configuration specifies the jruby-19mode target, which floats between exact versions of JRuby. At the time of writing, this is currently JRuby 1.7.8. You can see a list of Travis CI's provided rubies here. As long as the build is green you should be good to go.

Installing JRuby is simple with RVM:

rvm install jruby-1.7.6

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

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") # we've defined x in the sandbox
=> 3
>> sand.eval("x")
=> 3
>> x # but it hasn't leaked out into the host interpreter
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 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.]

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