Re: [Uta] "webby" STS and DANE/DNSSEC co-existence

[Daniel Margolis <[e-mail]>]

On Thu, Apr 14, 2016 at 8:38 AM, Viktor Dukhovni <[e-mail]>
wrote:

>
> If the STS spec is just for email between Yahoo and Gmail, sure,
> go for it.  Less work for me, I won't need to implement yet another
> transport security mechanism.
>
> A more reasonably modest STS would stay well clear of prescribing
> such fine details.  Once the policy lookup requires WebPKI support,
> pinning MX host certs is fragile over-engineering.
>

To be clear, HPKP allows pinning a root or intermediate cert, not just the
host cert. I think pinning someone in the cert chain and not the host cert
is generally preferable (in terms of safety and ease of certificate
rollover).

But in terms of broader feedback, I think you're making a really important
point here (and up-thread) about (config) usability and security tradeoffs.
For now, simply getting CA *or* DNSSEC based signing of security policies
is a huge benefit for MTA-to-MTA SMTP. In a future where CA or registrar
malfeasance is the weakest link, we know the next steps--key pinning, cert
transparency, and similar. But that would be a future where we've already
vastly improved the state of the art from most deployments today. ;)

Dan