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SubjectRe: [PATCH v8 3/8] security/brute: Detect a brute force attack
On Sat, Jul 03, 2021 at 12:59:28PM +0200, John Wood wrote:
> Hi,
>
> On Fri, Jul 02, 2021 at 05:08:09PM +0000, Alexander Lobakin wrote:
> >
> > On the other hand, it leaves a potentional window for attackers to
> > perform brute force from xattr-incapable filesystems. So at the end
> > of the day I think that the current implementation (a strong
> > rejection of such filesystems) is way more secure than having
> > a fallback I proposed.
>
> I've been thinking more about this: that the Brute LSM depends on xattr
> support and I don't like this part. I want that brute force attacks can
> be detected and mitigated on every system (with minimal dependencies).
> So, now I am working in a solution without this drawback. I have some
> ideas but I need to work on it.

I have been coding and testing a bit my ideas but:

Trying to track the applications faults info using kernel memory ends up
in an easy to abuse system (denied of service due to large amount of memory
in use) :(

So, I continue with the v8 idea: xattr to track application crashes info.

> > I'm planning to make a patch which will eliminate such weird rootfs
> > type selection and just always use more feature-rich tmpfs if it's
> > compiled in. So, as an alternative, you could add it to your series
> > as a preparatory change and just add a Kconfig dependency on
> > CONFIG_TMPFS && CONFIG_TMPFS_XATTR to CONFIG_SECURITY_FORK_BRUTE
> > without messing with any fallbacks at all.
> > What do you think?
>
> Great. But I hope this patch will not be necessary for Brute LSM :)

My words are no longer valid ;)

Thanks,
John Wood

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