Question

I realize this sounds a little crazy, but I’m working on a project for which I need a server to run user-provided Ruby code and return the result.

I’m looking to prevent something like this:

system("rm -rf /")
eval("something_evil")
# etc...

I’m sure there must be some reasonably safe way to do this, as it already exists at places like tryruby.org. Any help is greatly appreciated, thanks!

Answer 1

Three suggestions:

1) Take a look at Ruby taint levels. This provides some degree of protection against, eval('evil_code') type things, etc.

2) Unless user’s actually need access to the local file system, use something like fakefs

3) No matter what else you do follow Tronic’s suggestion (can be a pain to setup, but limited chroot jails are about the only way to make absolutely sure that user’s cannot access resources you don’t explicitly want them to).