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Re: [TLS] Eric Rescorla's Discuss on draft-ietf-tls-dnssec-chain-extension-06: (with DISCUSS and COMMENT)

Viktor Dukhovni <ietf-dane@dukhovni.org> Mon, 05 March 2018 14:00 UTC

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From: Viktor Dukhovni <ietf-dane@dukhovni.org>
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Date: Mon, 05 Mar 2018 09:00:15 -0500
Cc: tls-chairs <tls-chairs@ietf.org>, draft-ietf-tls-dnssec-chain-extension@ietf.org, The IESG <iesg@ietf.org>
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Subject: Re: [TLS] Eric Rescorla's Discuss on draft-ietf-tls-dnssec-chain-extension-06: (with DISCUSS and COMMENT)
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> On Mar 5, 2018, at 4:32 AM, Willem Toorop <willem@nlnetlabs.nl> wrote:
> 
>> Therefore, any long-term caching of a destination's support for the extension
>> should require server opt-in, and must have a maximum duration.
> 
> How do you (all) feel about using the expiry date on the RRSIG for the
> TLSA to be used for this purpose?

I don't think the expiry date is adequate for this purpose.  To reduce
the scope for replay attacks, my domain has 14 day RRSIG lifetimes, and
automated re-signing happens as records age, so they are often as close
as ~4 days away from expiration when re-signed.  And yet, if were to
deploy a web server that implements this extension, I'd want to commit
to DANE for a considerably longer time.

-- 
	Viktor.

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