Hi, I am happy to see us having discussions on how to protected SNI. I am also happy to see that draft-huitema-tls-sni-encryption [1] proposes actual methods that we might want to use, and that the I-D discusses about various attack vectors that we need to be aware of.
On the other hand, as stated on the mailing list an on the mic, I am not super happy with the fact that the proposed methods have a negative impact on connection establishment time. So here goes my straw-man proposal, as an Internet Draft: https://datatracker.ietf.org/doc/draft-kazuho-protected-sni/. In essence, the draft proposes of sending information (e.g., semi-static (EC)DH key) to bootstrap encryption in ClientHello as a DNS record. Clients will use the obtained (EC)DH key to encrypt SNI. Since DNS queries can run in parallel, there would be no negative performance impact, as long as DNS responses can be obtained in a single RTT. The draft mainly discusses about sending a signed bootstrap information together with the certificate chain, since doing so is not only more secure but opens up other possibilities in the future (such as 0-RTT full handshake). However, since transmitting a bootstrap record with digital signature and identity is unlikely to fit in a single packet (and therefore will have negative performance impact until DNS over TLS or QUIC becomes popular), the draft also discusses the possibility of sending the EC(DH) key unsigned in the "Things to Consider" section. I would appreciate it if you could give me comments / suggestions on the proposed approach. Thank you in advance. [1] https://datatracker.ietf.org/doc/draft-huitema-tls-sni-encryption/ ---------- Forwarded message ---------- From: <internet-dra...@ietf.org> Date: 2017-07-19 5:38 GMT+02:00 Subject: New Version Notification for draft-kazuho-protected-sni-00.txt To: Kazuho Oku <kazuho...@gmail.com> A new version of I-D, draft-kazuho-protected-sni-00.txt has been successfully submitted by Kazuho Oku and posted to the IETF repository. Name: draft-kazuho-protected-sni Revision: 00 Title: TLS Extensions for Protecting SNI Document date: 2017-07-19 Group: Individual Submission Pages: 9 URL: https://www.ietf.org/internet-drafts/draft-kazuho-protected-sni-00.txt Status: https://datatracker.ietf.org/doc/draft-kazuho-protected-sni/ Htmlized: https://tools.ietf.org/html/draft-kazuho-protected-sni-00 Htmlized: https://datatracker.ietf.org/doc/html/draft-kazuho-protected-sni-00 Abstract: This memo introduces TLS extensions and a DNS Resource Record Type that can be used to protect attackers from obtaining the value of the Server Name Indication extension being transmitted over a Transport Layer Security (TLS) version 1.3 handshake. Please note that it may take a couple of minutes from the time of submission until the htmlized version and diff are available at tools.ietf.org. The IETF Secretariat -- Kazuho Oku _______________________________________________ TLS mailing list TLS@ietf.org https://www.ietf.org/mailman/listinfo/tls
