Re: [dane] Improving DANE S/MIME Privacy
Viktor Dukhovni <ietf-dane@dukhovni.org> Thu, 13 April 2017 04:21 UTC
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From: Viktor Dukhovni <ietf-dane@dukhovni.org>
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Date: Thu, 13 Apr 2017 00:21:46 -0400
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Subject: Re: [dane] Improving DANE S/MIME Privacy
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> On Apr 12, 2017, at 11:59 PM, Phil Pennock <ietf-dane-phil@spodhuis.org> wrote: > >> I should note that one can of course implement one's SMIMEA deployment >> in exactly this way, something along the lines of: >> >> *._smimecert.example.net. IN SMIMEA 2 1 1 e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855 >> >> would associate the same TA public key digest with every user, and would >> not enable user enumeration. > > FWIW, I did something similar to this. Of course, there's a chicken/egg > problem in _getting_ the CA cert for private CAs, unless you put the > whole cert into DNS. And wildcards for something that large would be > cache-unpleasant, but I did the same thing I do for TLSA records: define > one SMIMEA record and CNAME to it elsewhere. Much more cache friendly. > > I never thought I'd see the day that I willingly chose to deploy a > wildcard CNAME. :^D > > $ORIGIN spodhuis.org. > *._smimecert CNAME _globnix-smimea > _globnix-smimea SMIMEA ( ; GlobnixCA5 PKIX-less trust anchor > 02 00 00 > ; SKIP: binary blob for an ECDSA CA > ; SMIMEA DANE-TA CERT FULL > ) > > I can't attest that this _works_. As far as I know, it's entirely > draft-spec compliant. Note, that provided your MUA includes the issuing certificate in the signature block (you can always make it an intermediate CA issued by a throw-away root whose private key has been destroyed, and then the MUA should include at least all the intermediates), there's no need to use "SMIMEA 2 0 0" with the "large" DNS payloads that this entails. You get the same mileage from "SMIMEA 2 1 1". That said, ECDSA certificates are often considerably smaller than is the case with RSA, so "2 0 0" may be sufficient small to avoid issues with UDP MTUs. Still, I'd just go with "SMIMEA 2 1 1". -- Viktor.
- [dane] Improving DANE S/MIME Privacy Alice Wonder
- Re: [dane] Improving DANE S/MIME Privacy Viktor Dukhovni
- Re: [dane] Improving DANE S/MIME Privacy Paul Wouters
- Re: [dane] Improving DANE S/MIME Privacy Viktor Dukhovni
- Re: [dane] Improving DANE S/MIME Privacy John Levine
- Re: [dane] Improving DANE S/MIME Privacy Alice Wonder
- Re: [dane] Improving DANE S/MIME Privacy Paul Wouters
- Re: [dane] Improving DANE S/MIME Privacy Viktor Dukhovni
- Re: [dane] Improving DANE S/MIME Privacy Viktor Dukhovni
- Re: [dane] Improving DANE S/MIME Privacy Phil Pennock