lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:   Sat, 22 Apr 2017 02:12:29 +0200
From:   Djalal Harouni <>
To:     Andy Lutomirski <>
Cc:     Kees Cook <>,
        Linux Kernel Mailing List <>,
        Andrew Morton <>,
        "Serge E. Hallyn" <>,
        LSM List <>,
        Linux API <>,
        Dongsu Park <>,
        Casey Schaufler <>,
        James Morris <>,
        Paul Moore <>,
        Tetsuo Handa <>,
        Greg Kroah-Hartman <>,
        Jonathan Corbet <>, Jessica Yu <>,
        Rusty Russell <>,
        Arnaldo Carvalho de Melo <>,
        Mauro Carvalho Chehab <>,
        Ingo Molnar <>,
        belakhdar abdeldjalil <>,
        Peter Zijlstra <>
Subject: Re: [PATCH v3 2/2] modules:capabilities: add a per-task modules
 autoload restriction

On Sat, Apr 22, 2017 at 1:51 AM, Andy Lutomirski <> wrote:
>>> I personally like my implicit_rights idea, and it might be interesting
>>> to prototype it.
>> I don't like blocking a needed feature behind a large super-feature
>> that doesn't exist yet. We'd be able to refactor this code into using
>> such a thing in the future, so I'd prefer to move ahead with this
>> since it would stop actual exploits.
> I don't think the super-feature is so hard, and I think we should not
> add the per-task thing the way it's done in this patch.  Let's not add
> per-task things where the best argument for their security is "not
> sure how it would be exploited".

Actually the XFRM framework CVE-2017-7184 [1] is one real example, of
course there are others. The exploit was used on a generic distro
during a security contest that distro is Ubuntu. That distro will
never provide a module autoloading restriction by default to not harm
it's users. Consumers or containers/sandboxes then can run their
confined apps using such facilities.

These bugs will stay in embedded devices that use these generic
distros for ever.

> Anyway, I think the sysctl is really the important bit.  The per-task
> setting is icing on the cake IMO.  One upon a time autoload was more
> important, but these days modaliases are supposed to do most of the
> work.  I bet that modern distros don't need unprivileged autoload at
> all.

Actually I think they do and we can't just change that. Users may
depend on it, it is a well established facility.

Now the other problem is CAP_NET_ADMIN which does lot of things, it is
more like the CAP_SYS_ADMIN.

This is a quick list that I got from only the past months, I'm pretty
sure there are more:

* DCCP use after free CVE-2017-6074
* n_hldc CVE-2017-2636
* XFRM framework CVE-2017-7184
* L2TPv3 CVE-2016-10200

Most of these need CAP_NET_ADMIN to be autoloaded, however we also
need CAP_NET_ADMIN for other things... therefore it is better to have
an extra facility that could coexist with CAP_NET_ADMIN and other
sandbox features.



Powered by blists - more mailing lists