Re: CVE for Kali Linux

[Alexander Cherepanov <ch3root () openwall com>]

On 2015-03-24 13:51, Marcus Meissner wrote:
> On Mon, Mar 23, 2015 at 10:41:01PM +0100, Marcus Meissner wrote:
> > On Tue, Mar 24, 2015 at 12:13:06AM +0300, Alexander Cherepanov wrote:
> > > On 2015-03-23 13:38, Marcus Meissner wrote:
> > > > > There are some attacks even if you verify signatures, e.g. serving
> > > > > old, known-vulnerable versions. HTTPS can help here (until
> > > > > signatures start to be widely accompanied by expiring timestamps or
> > > > > something).
> > > >
> > > > SUSE has added an expiry tag in the YUM metadata for such cases.
> > >
> > > It's nice to see progress in this area. Does SUSE guard against
> > > other attacks from [1] too?
> > >
> > > [1] https://isis.poly.edu/~jcappos/papers/cappos_pmsec_tr08-02.pdf
> >
> > Our statements from 2008 (7 years ago) still stand and our package
> > manager does the full repository signing since 2006 already.
> >
> > https://lizards.opensuse.org/2008/07/16/package-management-security-on-opensuse/

Judging only from this text, it seems that one of the crucial points of 
your system is "[t]he openSUSE download redirector [that] serves the 
metadata from a known and trusted source". And it lives at... 
http://download.opensuse.org and is not available over HTTPS at all?

> > "Endless Data Attack" is open, as it is hard to solve for openSUSE with
> > its public mirror system.

If you have signed metadata it should be easy to counter this attack for 
packages, right? If you serve you metadata from a trusted source then 
it's also solved for metadata. Even if you serve metadata over 
non-trusted channel it should be easy to bound the size of "root" 
metadata file and record sizes of the next level files in it, etc. Am I 
missing any complications?

> > The expiry was something added a bit later after the paper to address
> > the downgrade and replay attacks.
>
> Some more notes.
>
> While the "Update Scenario" is well covered, we are of course facing issues of "bringing up a system".
>
> Like discussed in the thread, how does the customer find a known good ISO image
> for download.
>
> While our installer is protecting itself with GPG signatures, but there is need for
> the root of trust of the CD medium itself.
>
> So for SUSE we publish SHA256 checksums on the https://download.suse.com/ website at least.
> For openSUSE the GPG/SHA and MD5 are on http://software.opensuse.org/132/de .

Hm, it's HTTP and a big part of this thread is about dangers of exactly 
this situation.

--
Alexander Cherepanov