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Date: Sat, 24 Jan 2015 18:43:13 +0100
From: Mathias Krause <>
Subject: Re: Re: CVE Request: Linux kernel crypto api
 unprivileged arbitrary module load

On 24 January 2015 at 15:53,  <> wrote:
>> The Crypto API in the Linux kernel before 3.19 allowed unprivileged users to
>> load arbitrary kernel modules.
> Use CVE-2013-7421 for the original 2013 discovery by Mathias Krause,
> with a "Try the code snippet below on a system with
> [...]

> Use CVE-2014-9644 for this second discovery in 2014, mentioned in
> PqFCo4bfrWu as 'stumbled over the first flaw -- not handling crypto
> templates correctly. This means, the patch would prevent loading the
> vfat.ko module when requesting a cipher named "vfat" but would fail to
> do so if one would request "vfat(aes)" instead.' As far as we can
> tell, this is a discovery of a separate attack vector that wasn't
> implied by the 2013 post.

Even though this was a new discovery, not explicitly mentioned in the
initial report, it's the same bug, essentially -- using the AF_ALG
interface to load arbitrary modules. In fact, commits 5d26a105b5a7 and
4943ba16bbc2 should have been a single one in the first place. But for
whatever reasons commit 5d26a105b5a7 was applied, so the template
issue had to be fixed in the follow-up commit 4943ba16bbc2. However,
both commits were merged together into Linus' tree that ended up in
v3.19-rc1. See the merge commit at [1] and the discussion at [2] for
further reference.


So I think CVE-2014-9644 should be marked as a duplicate of
CVE-2013-7421. It's the same issue, really.

> This isn't within the scope of either CVE-2013-7421 or CVE-2014-9644.
> As far as we can tell, it is largely a usability fix. The example
> mentioned is "This fixes, e.g., requesting 'ecb(blowfish-generic)',
> which used to work with kernels v3.18 and below." Is there also a
> security impact if 3e14dcf7cb80b34a1f38b55bc96f02d23fdaaaaf is
> missing? For example, is it likely that code exists that requests
> ecb(blowfish-generic) in an environment without
> 3e14dcf7cb80b34a1f38b55bc96f02d23fdaaaaf, and is able to continue
> working afterward, but falls back to weak encryption?

It's just an API compliance fix to not regress the user interface for
the Crypt User API. No security fix, AFAICS.


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