JRuby VM sandboxes
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JRuby Safe

The JRuby safe is a clone of jruby-sandbox


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


$ bundle install --path vendor/bundle
$ bundle exec rake spec

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") # 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 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.]