Re: [TLS] Negotiate only symmetric cipher via cipher suites (was: Ala Carte Cipher suites - was: DSA should die)
Daniel Kahn Gillmor <dkg@fifthhorseman.net> Mon, 13 April 2015 16:50 UTC
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From: Daniel Kahn Gillmor <dkg@fifthhorseman.net>
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Subject: Re: [TLS] Negotiate only symmetric cipher via cipher suites (was: Ala Carte Cipher suites - was: DSA should die)
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On Mon 2015-04-13 12:00:00 -0400, Dave Garrett wrote: > On Monday, April 13, 2015 03:14:45 am Daniel Kahn Gillmor wrote: >> On Mon 2015-04-13 02:01:52 -0400, Dave Garrett wrote: >> > Assign points to NamedGroup and >> > SignatureAlgorithm to negotiate PSK usage via the >> > extensions. (e.g. NamedGroup=0 for plain PSK) >> >> I'm not convinced that we want to use 0 for PSK (this may be purely >> aesthetic: it makes PSK sound like the "default", and if we later find >> other non-DH key exchange we want to stuff in this registry, it'd be >> nice to group them together, and there are no available neighbors close >> to 0). I think i'd be ok using some other currently-unallocated >> codepoint, though. > > The thought process was 0 for N/A in the case of PSK without > (EC)DHE. I would much prefer that only (EC)DHE_PSK be permitted, which > would make this a non-issue. Hm, let's look at the representations of ((EC)DHE_)PSK in the scheme you propose. You've split the suite using these terms and mechanisms: "symmetric" (indicated by ciphersuite list) "handshake" (indicated by known_groups extension) "signature" (indicated by signature_algorithms extension) I'd recommend using slightly different terminology, since at least "handshake" is already overloaded to mean something broader in TLS. "symmetric" (ciphersuite list) "key agreement" (known_groups extension) "authentication" (signature_algorithms extension) In this model, ECDHE_PSK would have: key agreement: ECDHE authentication: PSK while non-(EC)DHE PSK would have: key agreement: PSK authentication: PSK right? we'd only need a key agreement codepoint for PSK in the case we have non-(EC)DHE, but i have heard some constrained-devices people arguing for that in the WG, so that seems like a likely outcome. So if we have to have non-(EC)DHE PSK, what would it mean if a TLS peer were to try to negotiate: key agreement: PSK authentication: RSA-PSS Do we just say "don't do that"? clients using existing RSA_PSK ciphersuites [0] use the server's RSA key to encrypt the, uh, pre-premaster secret, which is then mixed with the PSK to complete the key exchange. This is *not* an RSA signature, and we're getting rid of the encrypted premaster secret approach in TLS 1.3 entirely. So the above seems like a novel (and possibly useless) combination. As for placing the known_groups codepoint at 0: it's conceivable that in the future someone wants to resurrect SRP or add some other PAKE or any other non-DH key agreement scheme (with or without forward secrecy and with or without authentication), in which case it would be aesthetically nice to have a block of "neighbors" with similar properties -- using 0 doesn't let us do that grouping. --dkg [0] https://tools.ietf.org/html/rfc4279#section-4
- Re: [TLS] DSA should die Yoav Nir
- Re: [TLS] DSA should die Dave Garrett
- [TLS] DSA should die Hanno Böck
- Re: [TLS] DSA should die Aaron Zauner
- Re: [TLS] DSA should die David Benjamin
- Re: [TLS] DSA should die Stephen Checkoway
- Re: [TLS] DSA should die Tony Arcieri
- Re: [TLS] DSA should die Bill Frantz
- Re: [TLS] DSA should die Tom Ritter
- Re: [TLS] DSA should die Viktor Dukhovni
- Re: [TLS] DSA should die Stephen Farrell
- Re: [TLS] DSA should die Nico Williams
- Re: [TLS] DSA should die Stephen Farrell
- Re: [TLS] DSA should die Viktor Dukhovni
- Re: [TLS] DSA should die Dave Garrett
- Re: [TLS] DSA should die Martin Thomson
- Re: [TLS] DSA should die Nico Williams
- Re: [TLS] DSA should die Martin Rex
- Re: [TLS] DSA should die Watson Ladd
- Re: [TLS] DSA should die Nico Williams
- Re: [TLS] DSA should die CodesInChaos
- Re: [TLS] DSA should die Martin Thomson
- Re: [TLS] DSA should die Dave Garrett
- Re: [TLS] DSA should die Nico Williams
- Re: [TLS] DSA should die Ilari Liusvaara
- Re: [TLS] DSA should die Joseph Salowey
- Re: [TLS] DSA should die Kurt Roeckx
- Re: [TLS] DSA should die Michael StJohns
- Re: [TLS] Ala Carte Cipher suites - was: DSA shou… Michael StJohns
- Re: [TLS] Ala Carte Cipher suites - was: DSA shou… Brian Smith
- Re: [TLS] Ala Carte Cipher suites - was: DSA shou… Tony Arcieri
- Re: [TLS] Ala Carte Cipher suites - was: DSA shou… Martin Thomson
- Re: [TLS] Ala Carte Cipher suites - was: DSA shou… Dave Garrett
- Re: [TLS] Ala Carte Cipher suites - was: DSA shou… Aaron Zauner
- Re: [TLS] Ala Carte Cipher suites - was: DSA shou… Dave Garrett
- Re: [TLS] Ala Carte Cipher suites - was: DSA shou… Viktor Dukhovni
- Re: [TLS] Ala Carte Cipher suites - was: DSA shou… Salz, Rich
- Re: [TLS] Ala Carte Cipher suites - was: DSA shou… Tony Arcieri
- Re: [TLS] Ala Carte Cipher suites - was: DSA shou… Yoav Nir
- Re: [TLS] Ala Carte Cipher suites - was: DSA shou… Brian Smith
- Re: [TLS] Ala Carte Cipher suites - was: DSA shou… Tony Arcieri
- Re: [TLS] Ala Carte Cipher suites - was: DSA shou… Ilari Liusvaara
- Re: [TLS] Ala Carte Cipher suites - was: DSA shou… Brian Sniffen
- Re: [TLS] Ala Carte Cipher suites - was: DSA shou… Viktor Dukhovni
- Re: [TLS] Ala Carte Cipher suites - was: DSA shou… Viktor Dukhovni
- Re: [TLS] Negotiate only symmetric cipher via cip… Dave Garrett
- Re: [TLS] Negotiate only symmetric cipher via cip… Daniel Kahn Gillmor
- Re: [TLS] Ala Carte Cipher suites - was: DSA shou… Aaron Zauner
- Re: [TLS] Negotiate only symmetric cipher via cip… Dave Garrett
- Re: [TLS] Negotiate only symmetric cipher via cip… Daniel Kahn Gillmor
- Re: [TLS] Negotiate only symmetric cipher via cip… Dave Garrett
- Re: [TLS] Negotiate only symmetric cipher via cip… Daniel Kahn Gillmor
- Re: [TLS] Negotiate only symmetric cipher via cip… Andrei Popov
- Re: [TLS] Negotiate only symmetric cipher via cip… Blumenthal, Uri - 0553 - MITLL
- Re: [TLS] Negotiate only symmetric cipher via cip… Viktor Dukhovni
- Re: [TLS] Negotiate only symmetric cipher via cip… Dave Garrett
- Re: [TLS] Negotiate only symmetric cipher via cip… Daniel Kahn Gillmor
- Re: [TLS] Negotiate only symmetric cipher via cip… Ilari Liusvaara
- Re: [TLS] Negotiate only symmetric cipher via cip… Dmitry Belyavsky
- Re: [TLS] Negotiate only symmetric cipher via cip… Daniel Kahn Gillmor
- Re: [TLS] Ala Carte Cipher suites - was: DSA shou… Geoffrey Keating
- Re: [TLS] Ala Carte Cipher suites - was: DSA shou… Yoav Nir
- Re: [TLS] Ala Carte Cipher suites - was: DSA shou… Viktor Dukhovni
- Re: [TLS] Ala Carte Cipher suites - was: DSA shou… Blumenthal, Uri - 0553 - MITLL
- Re: [TLS] Ala Carte Cipher suites - was: DSA shou… Geoffrey Keating
- Re: [TLS] Ala Carte Cipher suites - was: DSA shou… Viktor Dukhovni
- Re: [TLS] Ala Carte Cipher suites - was: DSA shou… Brian Smith
- Re: [TLS] Ala Carte Cipher suites - was: DSA shou… Brian Smith
- Re: [TLS] Ala Carte Cipher suites - was: DSA shou… Daniel Kahn Gillmor
- Re: [TLS] Ala Carte Cipher suites - was: DSA shou… Salz, Rich
- Re: [TLS] Ala Carte Cipher suites - was: DSA shou… Viktor Dukhovni
- Re: [TLS] Ala Carte Cipher suites - was: DSA shou… Dave Garrett
- Re: [TLS] Negotiate only symmetric cipher via cip… Ilari Liusvaara
- Re: [TLS] Ala Carte Cipher suites - was: DSA shou… Yoav Nir