Re: [dns-privacy] Stephen Farrell's Discuss on draft-ietf-dprive-dnsodtls-13: (with DISCUSS and COMMENT)

"Tirumaleswar Reddy (tireddy)" <tireddy@cisco.com> Thu, 15 December 2016 01:38 UTC

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From: "Tirumaleswar Reddy (tireddy)" <tireddy@cisco.com>
To: Stephen Farrell <stephen.farrell@cs.tcd.ie>, Stephane Bortzmeyer <bortzmeyer@nic.fr>
Thread-Topic: [dns-privacy] Stephen Farrell's Discuss on draft-ietf-dprive-dnsodtls-13: (with DISCUSS and COMMENT)
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Date: Thu, 15 Dec 2016 01:37:59 +0000
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Subject: Re: [dns-privacy] Stephen Farrell's Discuss on draft-ietf-dprive-dnsodtls-13: (with DISCUSS and COMMENT)
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> -----Original Message-----
> From: dns-privacy [mailto:dns-privacy-bounces@ietf.org] On Behalf Of
> Stephen Farrell
> Sent: Wednesday, December 14, 2016 7:36 PM
> To: Stephane Bortzmeyer <bortzmeyer@nic.fr>; Tirumaleswar Reddy (tireddy)
> <tireddy@cisco.com>
> Cc: tjw.ietf@gmail.com; dns-privacy@ietf.org; The IESG <iesg@ietf.org>; draft-
> ietf-dprive-dnsodtls@ietf.org; dprive-chairs@ietf.org
> Subject: Re: [dns-privacy] Stephen Farrell's Discuss on draft-ietf-dprive-
> dnsodtls-13: (with DISCUSS and COMMENT)
> 
> 
> Our mails overlapped and contradicted one another:-)
> 
> Might be better to let chair/shepherd figure out next step?
> 
> In the meantime though one thing below.
> 
> On 14/12/16 14:00, Stephane Bortzmeyer wrote:
> > On Wed, Dec 14, 2016 at 01:50:58PM +0000,  Tirumaleswar Reddy
> > (tireddy) <tireddy@cisco.com> wrote  a message of 238 lines which
> > said:
> >
> >> Agreed. I can add the following lines to Security considerations section:
> >>
> >> The DNS client MUST use the TLS Certificate Status Request extension
> >> (Section 8 of [RFC6066]), commonly called "OCSP stapling" to check
> >> the revocation status of public key certificate of the DNS server.
> >> OCSP stapling, unlike OSCP, does not suffer from scale and privacy
> >> issues.
> >
> > I'm not happy.
> >
> > 1) This is not specific to DTLS and it should not be in a
> > DTLS-specific document.
> 
> True that this isn't specific to DTLS. I don't agree that means this mustn't be in
> this document, necessarily, but there're a few ways that can be handled.
> 
> >
> > 2) We use TLS/DTLS for encrypting DNS precisely to save us reinventing
> > a security protocol. If we start to override TLS rules, we get into
> > dangerous waters.
> 
> I don't see this as overriding TLS or BCP195. I think there just is a special case
> here when a stub wants to check revocation status for a port 853 (D)TLS
> session.
> In all other cases, we assume the TLS client can just resolve an A/AAAA for an
> OCSP responder but that's not quite enough here.
> 
> > Mentioning the scale/privacy issues of OCSP is OK, but a MUST???
> 
> I think the MUST that Tiru suggested could work, but is not the only possible
> option.

How about downgrade to SHOULD from MUST ?
(If DANE TLSA resource record is used then both OCSP and OCSP stapling is not required).

-Tiru

> 
> Cheers,
> S.
> 
> 
> >
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> >