Re: Chroot bug

[Miloslav Semler]

Jan Engelhardt napsal(a):
> On Sep 25 2007 19:00, Miloslav Semler wrote:
>   
> > > > This  does not help.  Let's try:
> > > > chroot somewhere
> > > > mkdir foo
> > > > fd = open /
> > > > chroot foo
> > > >     
> > > >         
> > > ('fd' implicitly closed and chdir to /foo)
> > >   
> > >       
> > Really? Try it. I am sure, that this works. You can create directory in chroot
> > and break chroot by this. fd is not closed, because linux doesn't close
> > descriptors by chroot syscall. this can be done every time if you have
> > CAP_SYS_CHROOT.
> >     
>
> In case you have not followed my earlier email, I'll repost:
>
> |>> So what? Just do this: chdir into the root after chroot.
> |>
> |> I don't think so.  His exploit just got me all the way out of a 
> |> chroot within a chroot within a chroot, inclusive of lots of 
> |> chdirs.
> |>
> |
> |Close all fds that point to directories outside the root ;-)
>
> Perhaps that was formulated a bit sloppy. It of course means
> "On chroot(2), implicitly close all FDs that point outside."
>   
yes, but I can use fds from chroot ;-) ....
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