Re: [TLS] TLS ECH, how much can the hint stick out?

Martin Thomson <mt@lowentropy.net> Fri, 11 September 2020 01:46 UTC

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Date: Fri, 11 Sep 2020 11:46:28 +1000
From: "Martin Thomson" <mt@lowentropy.net>
To: tls@ietf.org
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Archived-At: <https://mailarchive.ietf.org/arch/msg/tls/XlsQXX4xxH3f8oFyb1JnoUwIOW8>
Subject: Re: [TLS] TLS ECH, how much can the hint stick out?
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On Fri, Sep 11, 2020, at 08:11, Eric Rescorla wrote:
> OK, this can't happen in DTLS because the CID management works differently.

Right.

> While it's not clear to me that QUIC explicitly prohibits this (it 
> would be prohibited if CRYPTO frames were STREAM frames because of 
> draft-ietf-tls-quic-transport S 2.2, it seems like it's  quite bad 
> practice because the result will be that the losing server has a 
> pending handshake which it continues to retransmit on until the client 
> times out.

QUIC does prohibit this.  This looks like another case of a client that sent an Initial and went away: a situation that servers have to deal with.  In any case, the server cannot retransmit indefinitely because it is bound by the anti-amplification limit.  I believe that QUIC works if the server doesn't arm a timer at this point, if it comes to that.