Hacker News Reader

Comment by phicoh | Hacker News Reader

If DNSSEC is part of your security model, you want local validation. Not relying on third party resolver that you don't have a contract with.

Beyond that, DNS has the AD bit. If you need DNSSEC secure data (for example for the TLSA record), then when Cloudflare turns off DNSSEC validation, the AD bit will be clear and things will stop working.

View on HN

Am I the only one who thinks that the AD bit is about as useful as the RFC 3514 evil bit?

We have this elaborate, complex, and extremely fragile cryptographic system behind DNSSEC and we distill it down to one single bit that we carry over unauthenticated links. Why?

At least WebPKI answers the right question: should I trust a particular claim to represent host.domain at the time in the following range? (Of course it defers determining the current time to some unspecified other mechanism.) DNSSEC tries to do everything and cannot survive an upstream error even within the downstream validity window. And yet, despite the fact that most of the spec leans heavily toward failing secure, the actual communication of validation status is entirely unprotected.

I can answer that! Because when DNSSEC was designed, it was believed that serverside compute could not keep up with per-request cryptography. DNSSEC contorts itself in several ways to maintain affordances for offline cryptography, which has been retconned into a security mechanism but was in reality just a bunch of non-cryptography-engineers making a terrible prediction about the feasability of cryptography.

(Source: I'm one of the few weirdos on Earth who has read the mailing lists all the way back to when DNSSEC was a TIS project).

The intention is clearly that the client is a minimal implementation that will only forward a request to a resolver it trusts. The fact that Cloudflare and Google have convinced us all to use Cloudflare's and Google's resolvers is the problem.

DNSSEC and WebPKI both rely on chains of trust. If the problem was that .de's keys expired, you'd have the same problem when Let's Encrypt's keys expired.

> If the problem was that .de's keys expired, you'd have the same problem when Let's Encrypt's keys expired.

Even this incident proves that’s not the case.

If LetsEncrypt has a temporary availability issue, my users don’t notice unless it spans longer than my need to renew a cert.

If LetsEncrypt has a CA cert expire, I can get a cert from another provider.

If DENIC’s DNSSEC records break, either due to an operational error or an expiry issue, my .de site becomes inaccessible and my users see a DNS lookup failure. My only option is to hope resolvers do what Cloudflare did, or move my site to a new TLD and just pray that TLD never has the same problem.

The WebPKI works end-to-end all the way to use devices; DNSSEC build an explicit client/server trust model into that. The former is obviously superior to the latter.

Yes, it's also quite damaging to DNSSEC's trust model that the world has transitioned to centralized resolver caches. But the fundamental problem we're talking about with the AD bit wouldn't vanish if 8.8.8.8 and 1.1.1.1 did too; instead, users would be even more reliant on ISP nameservers, which are literally the least trustworthy pieces of infrastructure on the entire Internet.

Reply on news.ycombinator.com