Re: [vox] Who opened the floodgates?

["Mark K. Kim" <markslist@cbreak.orMAPSg>]

On Wed, 12 Jun 2002, Micah Cowan wrote:

>  > It should be noted that the root user can break out of any chroot
>  > environment, pretty trivially.
>
> Boy, that kinda defeats the purpose of chroot(), doesn't it?
>
> I didn't know that - can you provide a brief explanation on how this
> may be done, or pointers to more information?

Use mknod to create a hard drive node to (re)mount the real system.  If
you don't got mknod, upload it.  If you don't got upload program (no ftp,
rz, etc.), write a script.  If you got no text editor, use echo with
redirection.  Etc.  You get the idea.

So to make a secure chroot system, you sorta need to strip it down quite a
bit to make sure people can't break out of chroot.  This is one reason why
it's hard to make a system look like it's the real root under a chrooted
environment (there are lots of programs and /dev/* stuff missing.)

Anyway, chroot does have its uses nonetheless, like in an FTP server where
there's no need to fake any root (ie - try to make it look like a real
root to fool the user) but just need to restrict the user's navigation to
a limited section of the file system.

-Mark

--
Mark K. Kim
http://www.cbreak.org/
PGP key available upon request.


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