Re: [TLS] Sending Custom DHE Parameters in TLS 1.3

Peter Gutmann <pgut001@cs.auckland.ac.nz> Thu, 15 October 2020 02:18 UTC

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From: Peter Gutmann <pgut001@cs.auckland.ac.nz>
To: =?iso-8859-1?Q?Hanno_B=F6ck?= <hanno@hboeck.de>, "tls@ietf.org" <tls@ietf.org>
Thread-Topic: [TLS] Sending Custom DHE Parameters in TLS 1.3
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Date: Thu, 15 Oct 2020 02:18:12 +0000
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Subject: Re: [TLS] Sending Custom DHE Parameters in TLS 1.3
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Hanno Böck <hanno@hboeck.de> writes:

>I suggest reading:
>https://blog.hboeck.de/archives/841-Diffie-Hellman-and-TLS-with-nonsense-parameters.html
>https://eprint.iacr.org/2016/644
>https://www.openssl.org/news/secadv/20160128.txt

This just confirms what I said previously, this is an overreaction to a
completely artificial situation.  The first link is to a problem with a badly
broken implementation, the second and third are to the use of maliciously-
generated parameters.  If your server is deliberately serving up malicious
parameters then you have bigger things to worry about than the crypto.

To put this another way, if I show that a malicious server can break TLS 1.3,
does that mean we have to throw it out and start bikeshedding TLS 1.4?

Peter.