Support Encrypted Client Hello (formerly known as ESNI)

[candrews]

Encrypted Client Hello is on the standards track and is already being deployed by big players.

Draft RFC: https://tools.ietf.org/html/draft-ietf-tls-esni

Championed by the EFF: https://www.eff.org/deeplinks/2018/09/esni-privacy-protecting-upgrade-https
Deployed by Cloudflare: https://blog.cloudflare.com/esni/
Cloudflare's technical details post: https://blog.cloudflare.com/encrypted-sni/
Supported by Firefox: https://blog.mozilla.org/security/2018/10/18/encrypted-sni-comes-to-firefox-nightly/
Supported by NSS: https://bugzilla.mozilla.org/show_bug.cgi?id=1495120
Work in Progress in picotls: h2o/picotls#155

🤞 this can be in OpenSSL 1.1.2 😄

[richsalz]

Your wording implies that it's done, and will soon be a standard. It's not done, it's going to be changing, and yes OpenSSL should support it once it gets finalized.

[kaduk]

Indeed; note that the intended status of the linked internet-draft is only Experimental; it is not intended to be on the standards track.
It will likely be changing more, and the risks and benefits are not terribly well understood yet.

[vcunat]

Nitpick: the link you provided wasn't the last version; that's probably here: https://tools.ietf.org/html/draft-ietf-tls-esni (just clicked a few times, no deep knowledge; EDITed as suggested, and it's in OP now anyway)

[richsalz]

Leave off the trailing -XX part and you always get the latest version.

[sftcd]

Hiya, I've coded up a proof-of-concept version of the client-side of ESNI for openssl. It works with the CloudFlare deployment and doesn't seem to fall over (but no guarantees:-). The code is here. I also tried to document the design. I hope to work with a student to do the server side and track changes in the Internet-draft as that progresses. Comments are v. welcome esp if there's stuff to do to make this more likely to end up useful for the project when the standard settles down.

[cayolblake]

@sftcd Is you code portable to BoringSSL ?

[sftcd]

Dunno, sorry, haven't ever looked inside BoringSSL. Happy to play about and see if that's useful at some point and someone tells me how:-)

[J0WI]

State in Go golang/go#9671 (comment)

[J0WI]

https://github.com/sftcd/openssl/tree/master/esnistuff

[sftcd]

Hiya, we've done some more work on our openssl fork that has ESNI support and on a curl fork that uses that. It's early days, but if anyone wants to try play with the build and give us feedback that'd be great. Here's HOWTO. If you find any issues with that you'd like to raise then please raise an issue in our openssl fork or curl fork, or send us mail at the addresses in the HOWTO. Thanks.

[sftcd]

We've integrated our ESNI supporting fork with the lighttpd web server. Details here. Be interested if anyone has feedback on that.