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Re: [TLS] ESNI GREASE - answer needed?

Steven Valdez <svaldez@google.com> Mon, 29 July 2019 22:53 UTC

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From: Steven Valdez <svaldez@google.com>
Date: Mon, 29 Jul 2019 15:52:48 -0700
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To: Stephen Farrell <stephen.farrell@cs.tcd.ie>
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Subject: Re: [TLS] ESNI GREASE - answer needed?
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Without GREASE, a server who doesn't have keys can't respond with any of
the existing responses (esni_accept is wrong since it can't decode the
ESNI, esni_retry_request is wrong since it can't provide keys for the
client to use on the retry). The only valid response would be a new record
type that says it doesn't support ESNI, which becomes equivalent to just
not sending the ESNI extension back in the EncryptedExtensions.

With GREASE, I don't know if it's particularly useful to fake the response
in the EncryptedExtensions, since network adversaries won't be able to see
the contents, I suppose its presence might slightly change the size of the
encrypted payload, though record padding could prevent that.


On Mon, Jul 29, 2019 at 3:34 PM Stephen Farrell <stephen.farrell@cs.tcd.ie>
wrote:

>
>
> On 29/07/2019 23:32, Steven Valdez wrote:
> > A server that doesn't have ESNI keys configured shouldn't be responding
> to
> > ESNI and should instead just ignore the ESNI extensions (as if it didn't
> > know what it was).
>
> Why?
>
> Thanks,
> S.
>


-- 

Steven Valdez |  Chrome Networking |  svaldez@google.com |  210-692-4742

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