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SubjectRe: Chroot bug
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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