Re: how an hacker can bypass a chrooted environement ?

[Rob <capveg () cs umd edu>]

On Fri, May 12, 2006 at 12:37:43PM +0200, Norbert Franois wrote:
> Hi...
>
> I was wondering how an attacker can bypass a chrooted environement. A
> (common) technique consist in finding a vulnerable program (in the
> chrooted environnement) and injecting it a shellcode (i.e
> ../../../../../../../bin/bash for ex.)  by BoF.  But normally, in the
> chrooted environement, you volontarily add only necessary tools (like
> ls, cat, less...), and vulnerable softwares are uncommon...
>
> So... how do they this "exploit" of bypassing the chroot ?

from man 2 chroot():

--
Note  that  this call does not change the current working directory, so
that '.' can be outside the tree rooted at  '/'.   In  particular,  the
super-user  can escape from a 'chroot jail' by doing 'mkdir foo; chroot
foo; cd ..'.
--

Also, mknod() some device files like /dev/kmem or /dev/hda1, then use
root priviledges to muck with kernel, or raw write data to disk.


- Rob
.

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