[Ach] Fedora will implement "crypto policies"

Aaron Zauner azet at azet.org
Thu Mar 20 18:30:09 CET 2014

Hi Nikos,

Nikos Mavrogiannopoulos wrote:
> Hello Aaron,
>  I have seen your project before, and this is a very nice first step.
> However, despite that is the current best practice, hardening each and
> every service is something risky; some services may be forgotten or some
> different copy/paste settings may be present in some of them, or some
> clients that run periodically and use SSL via a dependency may not even
> be known to the administrator. That is why we will attempt to use
> system-wide crypto settings shared by all available services.
I do understand your attempt and it is probably the best way to
implement such a policy distribution-wide. But since none of us do
directly represent any of the GNU/Linux distributions that are out there
(though some do commit) - we cannot easily implement that and force it
upstream. We do talk to distribution vendors and projects though. This
is why I've included you in this thread.

We're all facing a difficult task: get admins to deploy secure
configurations ASAP. The obvious and easiest way for us was to outline
common services that use TLS and how to properly configure those. I'm
now pretty sure that our project will expand it's scope over time. As it
has already (we wanted a 30 page document, we're right now at 94 pages
and it's growing due to valuable contributions such as the kerberos

> One thing that I realized after implementing that is that setting the
> ciphersuites isn't sufficient to ensure a global policy. For example
> connecting to a server using the TLS ciphersuite DHE-RSA with AES will
> fulfill that policy, but that does not take into account the actual
> group used for DHE (and there exist misconfigured servers that send
> 512-bit groups).
That is correct. We've also noticed that and included recommendations in
our paper. Most services do not even seem to know that DH parameter
choices that they're shipping right now are in fact a security desaster.

> On this and some other issues (e.g., restricting available curves, or
> setting a policy for acceptable parameters in certificates) we work on.
> Currently we modify gnutls and nss, and upstream openssl said is already
> working on it [0].

> We are certainly interested for collaboration, and you are more than
> welcome to contribute to that effort (let me know in that case). It is
> not really fedora/redhat-specific as we work with the upstream projects.
> The Fedora-specific part are the scripts that convert the system policy
> to individual library policies.
I'd personally be willing to help and to exchange information within
both of our projects, I guess that makes sense. Although I'm not
available all the time due to contract work. I'm not a Fedora developer
(nor user) but I work almost daily with RHEL as well as CentOS6 at
customer sites, so I do really appreciate your effort there.


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