Date: Tue, 24 Mar 2015 16:53:30 +0300 From: Alexander Cherepanov <ch3root@...nwall.com> To: oss-security@...ts.openwall.com Subject: Re: CVE for Kali Linux 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  too? >>> >>>  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
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