Comment by tptacek
11 hours ago
DNSSEC can't protect against an ECH downgrade. ECH attackers are all on-path, and selectively blocking lookups is damaging even if you can't forge them. DoH is the answer here, not record integrity.
11 hours ago
DNSSEC can't protect against an ECH downgrade. ECH attackers are all on-path, and selectively blocking lookups is damaging even if you can't forge them. DoH is the answer here, not record integrity.
DNSSEC alone is obviously useless because any attacker interested in SNI hostnames can just as easily monitor DNS traffic.
However, DoH/DoT without record integrity is about as useful as self-signed HTTPS certificates. You need both for the system to work right in every case.
To quote the spec:
> Clearly, DNSSEC (if the client validates and hard fails) is a defense against this form of attack, but encrypted DNS transport is also a defense against DNS attacks by attackers on the local network, which is a common case where ClientHello and SNI encryption are desired. Moreover, as noted in the introduction, SNI encryption is less useful without encryption of DNS queries in transit.
I don't think this is true; I think this misunderstands the ECH threat model. You don't need record integrity to make ECH a strong defense against on-path ISP attackers; you just need to trust the resolver you're DoH'ing to.
This actually reminds me of the "God of the gaps" problem. A gradual retreat in the face of inconvenient facts.
Many years ago when I was a student the argument was that integrity isn't a big deal so plaintext telnet is just fine. If you're paranoid you use an "enhanced" telnet where the authentication step is protected but not everything else [Yes I'm an old man]
By the turn of the century everybody agreed telnet is stupid, use SSH but integrity still wasn't a big deal when it comes to ordinary web sites. Only your bank needs SSL fool.
And I suppose that 8-10 years ago that changed too and it's now recognised that plaintext HTTP really isn't good enough, you need HTTPS. But still I see that you say integrity isn't important when it comes to DNS records.
Integrity is the hardest thing to get ordinary users to care about. Given how freely even young kids lie we should probably take it more seriously but it remains hard to get ordinary people to care, however ultimately this does matter.
1 reply →