[Ach] filippo on SSL SMTP encryption

Hanno Böck hanno at hboeck.de
Wed Apr 1 12:17:43 CEST 2015

On Wed, 01 Apr 2015 09:31:44 +0200
Manuel Kraus <ach at lsd.is> wrote:

> If you talk about clients, you mean users desktop software, right?
> Things like already mentioned webbrowsers, email applications etc.
> Well, there are validator add-ons for webbrowsers available, so a
> small fraction of users is already able to practically add -some-
> plausibility to their connections. That's way to far from general
> deployment in common software and is more like a PoC, I agree.  

Yes, I mean software deployment on desktops (and phones and whatever).
Depends on what we're talking, but there are people out there promoting
DANE for https and things like pgp keys via dnssec.

> But: Do we forget server-server operations here? Doesn't  DNSSEC at
> least helps to add some reliability to such connections? My resolvers
> for all my servers do speak DNSSEC and should have those advantages
> DNSSEC people are trying to sell. CA is far from perfect. DNSSEC is
> not perfect either. But it seems to be all we have right now not to
> fall in the abyss almost instantly (yes, I know certificate pinning
> and other, but sadly not instantly deployable, approaches). Every
> additional layer of authentication -in combination- helps to make it
> harder for adversaries to manipulate things, imho.  

I agree that servers are a different thing. Maybe DNSSEC will have its
place to protect s2s crypto. But I still see a lot of issues there.
Like "Oh you live in a country where your TLD operator doesn't support
DNSSEC yet? There's nothing you can do..."
That's what I meant with the too many pieces.

I'd feel a pinning solution for smtp/starttls would bring us more than
dnssec. tack is in limbo right now (and I'm not sure if it'd solve
everything needed for smtp).

> It's easy to criticize current approaches like DNSSEC and talk about
> the flaws they obviously have, but what are the options -right now- ?
> Which techniques are available -right now- ?  

HPKP and Certificate Transparency.
And I feel there's really a big difference between DANE on one side and
HPKP/CT on the other. HPKP needs two pieces to work (a server config
and a client software change). CT needs more pieces, but it was
explicitly designed in a way that even partly deployment already gains
you something. (you can check the CT logs if there are bad certs
popping up for your domain - there was a service to do that for you,
but it seems it's gone...)

Hanno Böck

mail/jabber: hanno at hboeck.de
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