Re: [dane] Digest Algorithm Agility discussion
Viktor Dukhovni <viktor1dane@dukhovni.org> Mon, 17 March 2014 17:44 UTC
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From: Viktor Dukhovni <viktor1dane@dukhovni.org>
To: dane@ietf.org
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References: <20140315051704.GY21390@mournblade.imrryr.org> <alpine.LFD.2.10.1403171115580.32251@bofh.nohats.ca> <20140317155049.GB24183@mournblade.imrryr.org> <B4473EDA-DAB4-4CC2-ACCD-B4F8939E5A2C@vpnc.org>
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Subject: Re: [dane] Digest Algorithm Agility discussion
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On Mon, Mar 17, 2014 at 09:47:46AM -0700, Paul Hoffman wrote: > >>> * It should be possible for servers to publish TLSA records > >>> employing multiple digest algorithms allowing clients to > >>> choose the best mutually supported digest. > >> > >> Isn't that already possible? > > > > Not based on RFC 6698 alone. With RFC 6698 the client trusts all > > TLSA records whether "weak" and "strong". > > Can you point to the specific text for that? It was not my > intention, and I doubt it was the intention of the WG. Per RFC 6698, the client evaluats all "usable" TLSA records until one matches, regardless of digest algorithm strength. > > My proposal is essentially the same. The client uses the strongest > > acceptable digest algorithm. The *client* decides what "strongest" > > means. It never chooses an unsupported algorithm. > > Again, that was at least my intention for 6698. If we need to > clarify that, that would be much better than adding another layer > of protocol grease. There is no text in 6698 that even approximately suggests that clients get to use only the records with the strongest (local criteria) digest. > > Stronger clients will never use the published weak records. > > I strongly doubt that is the desired outcome. If so, lots of > zones will go invisible when the "later" in "remove weak digests > later" stretches to a decade. One can audit for weak TLSA RRsets on peer systems before deciding to disable a weak algorithm. My proposal makes it possible to ramp security before completely disabling an algorithm. Not doing the proposed agility algorithm makes the problem worse. > > This works poorly. While the weak algorithm is being phased out > > (years) even clients that support stronger algorithms are at risk. > > At risk of what? Seriously: DANE is additional security over > non-TLS, so a "weak" algorithm is still better than "no TLS". > Reduction to absurdity is not helpful here. Of all people, I am quite surprised to see you say that. DANE IS NOT additional security over non-TLS. DANE is a specification for publishing public keys in DNS. It can be used for both opportunistic and non-opportunistic use-cases. Postfix supports DANE in both opportunistic and mandatory modes. Please see also my reply to Paul W. -- Viktor.
- [dane] Digest Algorithm Agility discussion Viktor Dukhovni
- Re: [dane] Digest Algorithm Agility discussion Paul Wouters
- Re: [dane] Digest Algorithm Agility discussion Viktor Dukhovni
- Re: [dane] Digest Algorithm Agility discussion Paul Hoffman
- Re: [dane] Digest Algorithm Agility discussion Paul Wouters
- Re: [dane] Digest Algorithm Agility discussion Viktor Dukhovni
- Re: [dane] Digest Algorithm Agility discussion Viktor Dukhovni
- Re: [dane] Digest Algorithm Agility discussion Paul Hoffman
- Re: [dane] Digest Algorithm Agility discussion Viktor Dukhovni
- Re: [dane] Digest Algorithm Agility discussion Paul Wouters
- Re: [dane] Digest Algorithm Agility discussion Viktor Dukhovni
- Re: [dane] Digest Algorithm Agility discussion Paul Hoffman
- Re: [dane] Digest Algorithm Agility discussion Viktor Dukhovni
- Re: [dane] Digest Algorithm Agility discussion Martin Rex
- Re: [dane] Digest Algorithm Agility discussion Viktor Dukhovni
- Re: [dane] Digest Algorithm Agility discussion Mark Andrews
- Re: [dane] Digest Algorithm Agility discussion Viktor Dukhovni
- Re: [dane] Digest Algorithm Agility discussion (c… Viktor Dukhovni
- Re: [dane] Digest Algorithm Agility discussion Jim Schaad
- Re: [dane] Digest Algorithm Agility discussion (c… Paul Hoffman
- Re: [dane] Digest Algorithm Agility discussion (c… Andrew Sullivan
- Re: [dane] Digest Algorithm Agility discussion (c… Viktor Dukhovni
- Re: [dane] Digest Algorithm Agility discussion (c… Scott Rose
- Re: [dane] Digest Algorithm Agility discussion (c… Viktor Dukhovni
- Re: [dane] Digest Algorithm Agility discussion (c… Scott Rose
- Re: [dane] Digest Algorithm Agility discussion Wes Hardaker
- Re: [dane] Digest Algorithm Agility discussion Viktor Dukhovni
- Re: [dane] Digest Algorithm Agility discussion Peter Palfrader
- Re: [dane] Digest Algorithm Agility discussion Mark Andrews
- Re: [dane] Digest Algorithm Agility discussion Viktor Dukhovni
- Re: [dane] Digest Algorithm Agility discussion Mark Andrews
- Re: [dane] Digest Algorithm Agility discussion Peter Palfrader
- Re: [dane] Digest Algorithm Agility discussion Mark Andrews
- Re: [dane] Digest Algorithm Agility discussion Viktor Dukhovni
- Re: [dane] Digest Algorithm Agility discussion Peter Palfrader
- Re: [dane] Digest Algorithm Agility discussion Viktor Dukhovni
- Re: [dane] Digest Algorithm Agility discussion Mark Andrews
- Re: [dane] Digest Algorithm Agility discussion Mark Andrews
- Re: [dane] Digest Algorithm Agility discussion Viktor Dukhovni
- Re: [dane] Digest Algorithm Agility discussion Paul Wouters
- Re: [dane] Digest Algorithm Agility discussion Viktor Dukhovni
- Re: [dane] Digest Algorithm Agility discussion Peter Palfrader
- Re: [dane] Digest Algorithm Agility discussion Wes Hardaker
- Re: [dane] Digest Algorithm Agility discussion Wes Hardaker