I wrote about ECH a couple of months ago, when the specs were still in draft but already approved for publication. It's a short read, if you're not already familiar with ECH and its history: https://www.feistyduck.com/newsletter/issue_127_encrypted_cl...
In addition to the main RFC 9849, there is also RFC 9848 - "Bootstrapping TLS Encrypted ClientHello with DNS Service Bindings": https://datatracker.ietf.org/doc/rfc9848/
There's an example of how it's used in the article.
Thanks for the writeup, Ivan, I am a great fan of your work!
Now we need to get Qualys to cap SSL Labs ratings at B for servers that don't support ECH. Also those that don't have HSTS and HSTS Preload while we're at it.
Thanks! Sadly, SSL Labs doesn't appear to be actively maintained. I've noticed increasing gaps in its coverage and inspection quality. I left quite a while ago (2016) and can't influence its grading any more, sadly.
Is there a well-maintained alternative to SSL Labs you can recommend?
Yes, there is! After I left SSL Labs, I built Hardenize, which was an attempt to go wider and handle more of network configuration, not just TLS and PKI. It covers a range of standards, from DNS, over email, TLS and PKI, and application security.
Although Hardenize was a commercial product (it was acquired in 2022 by another company, Red Sift), it has a public report that's always been free. For example:
https://www.hardenize.com/report/feistyduck.com
The CSP inspection in Hardenize could use a refresh, but the TLS and PKI aspects are well maintained [at the time of writing].
I use testssl.sh [1] mostly because I can test things not publicly accessible.
[1] - https://github.com/testssl/testssl.sh
> There's an example of how it's used in the article
A bit tricky in Go, but nothing too complicated. We implemented ECH in Aug 2024 for our DNS Android app and it has worked nicely since: https://github.com/celzero/firestack/blob/09b26631a2eac2cf9c...