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From: Simon Mcbryan on 21 May 2010 14:17
Hello Ruby Forum.

I am working on a personal project that will need people to be able to
submit bits of Ruby code so that my project can run it (eval). I know
there is a lot of danger in this and wonder if there are any solid ways
to avoid malicious attacks.

From what I have read and seen on Google, there is the $SAFE (=4)
variable which is supposed to prevent many vulnerabilities, but at the
same time, there are many sources saying this is not reliable. Also, I
have seen that a year or 2 ago, there was a popular Ruby project called
Sandbox, created by a whytheluckystiff, who has apparently disappeared
off the face of the planet, and thus killing the project.

So I am wondering if I should attempt to work off Sandbox, although I
don't think it is maintained or updated to the newer Ruby versions
(1.8.7+). I am pretty new to the whole metaprogramming world, so I am
not sure if I could handle this either. Or should I try to create my
own system, using $SAFE, disallowing known loopholes, running in a
thread with a kill time and timeout limit, etc. Or is there an
alternative to Sandbox that I should be looking at that my research has
not turned up? Thanks for your time.

- simon
--
Posted via http://www.ruby-forum.com/.

From: Simon McBryan on 22 May 2010 12:27
Andrew Mcelroy wrote:
> Look at Try Ruby.
> $SAFE > 3 won't work in a repl, btw
>
> Andrew McElroy
> http://TryRuby.org

Cool, thanks, looks like this should do the trick.
--
Posted via http://www.ruby-forum.com/.

From: Josh Cheek on 23 May 2010 02:23
[Note: parts of this message were removed to make it a legal post.]

On Sat, May 22, 2010 at 11:27 AM, Simon McBryan <smcbryan(a)gmail.com> wrote:

> Andrew Mcelroy wrote:
> > Look at Try Ruby.
> > $SAFE > 3 won't work in a repl, btw
> >
> > Andrew McElroy
> > http://TryRuby.org
>
> Cool, thanks, looks like this should do the trick.
> --
> Posted via http://www.ruby-forum.com/.
>
>
If you're on a Mac, you might try Dia. http://github.com/robgleeson/Dia

From: Caleb Clausen on 23 May 2010 08:43
On 5/21/10, Simon Mcbryan <smcbryan(a)gmail.com> wrote:
> Hello Ruby Forum.
>
> I am working on a personal project that will need people to be able to
> submit bits of Ruby code so that my project can run it (eval). I know
> there is a lot of danger in this and wonder if there are any solid ways
> to avoid malicious attacks.
>
> From what I have read and seen on Google, there is the $SAFE (=4)
> variable which is supposed to prevent many vulnerabilities, but at the
> same time, there are many sources saying this is not reliable. Also, I
> have seen that a year or 2 ago, there was a popular Ruby project called
> Sandbox, created by a whytheluckystiff, who has apparently disappeared
> off the face of the planet, and thus killing the project.
>
> So I am wondering if I should attempt to work off Sandbox, although I
> don't think it is maintained or updated to the newer Ruby versions
> (1.8.7+). I am pretty new to the whole metaprogramming world, so I am
> not sure if I could handle this either. Or should I try to create my
> own system, using $SAFE, disallowing known loopholes, running in a
> thread with a kill time and timeout limit, etc. Or is there an
> alternative to Sandbox that I should be looking at that my research has
> not turned up? Thanks for your time.

$SAFE is unlikely to be good enough. Even why's sandbox probably has
some vulnerabilities.

Depending on what you're doing, you could try running inside a virtual
machine or freebsd jail. These are general-purpose sandbox facilities,
not ruby specific. That's somewhat difficult to set up, but they
should be very solid choices.

All these ideas could be combined. That is, you run with $SAFE=4, in
why's sandbox, inside a jail in a freebsd installation running in a
virtual machine. That way, you have multiple layers of protection, and
the best of all worlds.

Another idea; if you want to use jruby, you could take advantage of
the jvm's sandboxing capabilities. I believe this would require some
custom java security manager programming.

From: Charles Oliver Nutter on 25 May 2010 15:39
On Sun, May 23, 2010 at 7:43 AM, Caleb Clausen <vikkous(a)gmail.com> wrote:
> $SAFE is unlikely to be good enough. Even why's sandbox probably has
> some vulnerabilities.

To be honest, I'm not sure I trust $SAFE because it takes such a
scattered approach to performance. Basically every operation that
mutates needs to check for tainting (and now "untrust" in 1.9) or
there's a hole. That's a lot of code to ensure is always doing the
right thing.

Plus C extensions either need to be disabled or audited as well.

Granted...$SAFE is what's available on MRI, so I don't have another
solution for non-JRuby users.

> Another idea; if you want to use jruby, you could take advantage of
> the jvm's sandboxing capabilities. I believe this would require some
> custom java security manager programming.

Actually it can often just come down to configuration. "Programming" a
security manager isn't generally needed to secure a server or sandbox
an application.

- Charlie

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