Re: [TLS] Security review of TLS1.3 0-RTT
Viktor Dukhovni <ietf-dane@dukhovni.org> Tue, 02 May 2017 17:37 UTC
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From: Viktor Dukhovni <ietf-dane@dukhovni.org>
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Date: Tue, 02 May 2017 13:33:37 -0400
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Subject: Re: [TLS] Security review of TLS1.3 0-RTT
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> On May 2, 2017, at 10:44 AM, Colm MacCárthaigh <colm@allcosts.net> wrote: > > https://github.com/tlswg/tls13-spec/issues/1001 > > I'll summarize the summary: Naturally the focus was on forward secrecy and replay. On forward secrecy the main finding was that it's not necessary to trade off Forward Secrecy and 0-RTT. A single-use session cache can provide it, and with the modification that ekr has created in https://github.com/tlswg/tls13-spec/pull/998 , such a cache works for both pre-auth and post-auth tickets, and it allows clients to build up pools of meaningfully distinct tickets. > > There's also an observation there that it should really be that clients "MUST" use tickets only once. Any re-use likely discloses the obfuscated ticket age, which is intended to be secret. Right now it's a "SHOULD". Well, just a few days ago there was a discussion of ticket re-use, and I was re-assured that ticket re-use was likely to going to work just fine... https://www.ietf.org/mail-archive/web/tls/current/threads.html#23035 TLS is a general-purpose protocol, used broadly beyond just the browser space. With TLS in SMTP there's no demand or need for 0-RTT and server resources are often more constrained than you'd find on a CDN server farm. Repeat connections are spaced further apart, and session lifetimes are longer (Postfix defaults to an hour). For Postfix, going back to a server-side session *increases* risk of loss of forward secrecy, because bulky server-side session objections are written out an on disk database, and e.g. with LMDB (a COW database) may take a long time to be deleted. By contrast session ticket encryption keys (STEKs) are small, kept in memory, and are overrwritten and freed after ~2 hours. Going back to server-side sessions would reduce resumption security for Postfix, and would make servers more susceptible to DoS through cache exhaustion. On the client side, non-reusable tickets would require substantially more complex cache designs, and probably significant changes in the session APIs and internals of TLS toolkits rather late in the evolution of the TLS 1.3 support code. I am far from convinced that the effort would not be better spent improving STEK key management in TLS server farms, which will need to support TLS 1.2 in parallel with TLS 1.3 for quite a long time (likely a decade or more). I believe that the proposed change is well intentioned but counter-productive. -- Viktor.
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Viktor Dukhovni
- Re: [TLS] Security review of TLS1.3 0-RTT Nico Williams
- Re: [TLS] Security review of TLS1.3 0-RTT Nico Williams
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Nico Williams
- Re: [TLS] Security review of TLS1.3 0-RTT Viktor Dukhovni
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Nico Williams
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Nico Williams
- Re: [TLS] Security review of TLS1.3 0-RTT Viktor Dukhovni
- Re: [TLS] Security review of TLS1.3 0-RTT Benjamin Kaduk
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Ilari Liusvaara
- Re: [TLS] Security review of TLS1.3 0-RTT Viktor Dukhovni
- Re: [TLS] Security review of TLS1.3 0-RTT Benjamin Kaduk
- Re: [TLS] Security review of TLS1.3 0-RTT Nico Williams
- Re: [TLS] Security review of TLS1.3 0-RTT Benjamin Kaduk
- Re: [TLS] Security review of TLS1.3 0-RTT Nico Williams
- Re: [TLS] Security review of TLS1.3 0-RTT Benjamin Kaduk
- Re: [TLS] Security review of TLS1.3 0-RTT Nico Williams
- Re: [TLS] Security review of TLS1.3 0-RTT Daniel Kahn Gillmor
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Nico Williams
- Re: [TLS] Security review of TLS1.3 0-RTT Eric Rescorla
- Re: [TLS] Security review of TLS1.3 0-RTT Nico Williams
- Re: [TLS] Security review of TLS1.3 0-RTT Eric Rescorla
- Re: [TLS] Security review of TLS1.3 0-RTT Peter Gutmann
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Viktor Dukhovni
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Jeffrey Walton
- Re: [TLS] Security review of TLS1.3 0-RTT Eric Rescorla
- Re: [TLS] Security review of TLS1.3 0-RTT Viktor Dukhovni
- Re: [TLS] Security review of TLS1.3 0-RTT Nico Williams
- Re: [TLS] Security review of TLS1.3 0-RTT Nico Williams
- Re: [TLS] Security review of TLS1.3 0-RTT Nico Williams
- Re: [TLS] Security review of TLS1.3 0-RTT Nico Williams
- Re: [TLS] Security review of TLS1.3 0-RTT Eric Rescorla
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Martin Thomson
- Re: [TLS] Security review of TLS1.3 0-RTT Hannes Tschofenig
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Viktor Dukhovni
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Salz, Rich
- Re: [TLS] Security review of TLS1.3 0-RTT Viktor Dukhovni
- Re: [TLS] Security review of TLS1.3 0-RTT Salz, Rich
- Re: [TLS] Security review of TLS1.3 0-RTT Viktor Dukhovni
- Re: [TLS] Security review of TLS1.3 0-RTT Salz, Rich
- Re: [TLS] Security review of TLS1.3 0-RTT Nico Williams
- Re: [TLS] Security review of TLS1.3 0-RTT Viktor Dukhovni
- Re: [TLS] Security review of TLS1.3 0-RTT Nico Williams
- Re: [TLS] Security review of TLS1.3 0-RTT Timothy Jackson
- Re: [TLS] Security review of TLS1.3 0-RTT Viktor Dukhovni
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Nico Williams
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Viktor Dukhovni
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Nico Williams
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Viktor Dukhovni
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Martin Thomson
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Viktor Dukhovni
- Re: [TLS] Security review of TLS1.3 0-RTT Bill Cox
- Re: [TLS] Security review of TLS1.3 0-RTT Martin Thomson
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Viktor Dukhovni
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Watson Ladd
- Re: [TLS] Security review of TLS1.3 0-RTT Martin Thomson
- Re: [TLS] Security review of TLS1.3 0-RTT Viktor Dukhovni
- Re: [TLS] Security review of TLS1.3 0-RTT Salz, Rich
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Viktor Dukhovni
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Blumenthal, Uri - 0553 - MITLL
- Re: [TLS] Security review of TLS1.3 0-RTT Eric Rescorla
- Re: [TLS] Security review of TLS1.3 0-RTT Peter Gutmann
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Eric Rescorla
- Re: [TLS] Security review of TLS1.3 0-RTT Ilari Liusvaara
- Re: [TLS] Security review of TLS1.3 0-RTT Andrei Popov
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Andrei Popov
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Andrei Popov
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Andrei Popov
- Re: [TLS] Security review of TLS1.3 0-RTT Erik Nygren
- Re: [TLS] Security review of TLS1.3 0-RTT Nico Williams
- Re: [TLS] Security review of TLS1.3 0-RTT Benjamin Kaduk
- Re: [TLS] Security review of TLS1.3 0-RTT Nico Williams
- Re: [TLS] Security review of TLS1.3 0-RTT Ilari Liusvaara
- Re: [TLS] Security review of TLS1.3 0-RTT Nico Williams
- Re: [TLS] Security review of TLS1.3 0-RTT Nico Williams
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Nico Williams
- Re: [TLS] Security review of TLS1.3 0-RTT Eric Rescorla
- Re: [TLS] Security review of TLS1.3 0-RTT Kyle Nekritz
- Re: [TLS] Security review of TLS1.3 0-RTT Eric Rescorla
- Re: [TLS] Security review of TLS1.3 0-RTT Nico Williams
- Re: [TLS] Security review of TLS1.3 0-RTT Erik Nygren
- Re: [TLS] Security review of TLS1.3 0-RTT Eric Rescorla
- Re: [TLS] Security review of TLS1.3 0-RTT Kyle Nekritz
- Re: [TLS] Security review of TLS1.3 0-RTT Derrell Piper
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Benjamin Kaduk
- Re: [TLS] Security review of TLS1.3 0-RTT Eric Rescorla
- Re: [TLS] Security review of TLS1.3 0-RTT Ilari Liusvaara
- Re: [TLS] Security review of TLS1.3 0-RTT Nico Williams
- Re: [TLS] Security review of TLS1.3 0-RTT Christian Huitema
- Re: [TLS] Security review of TLS1.3 0-RTT Eric Rescorla
- Re: [TLS] Security review of TLS1.3 0-RTT Viktor Dukhovni
- Re: [TLS] Security review of TLS1.3 0-RTT Eric Rescorla
- Re: [TLS] Security review of TLS1.3 0-RTT Ilari Liusvaara
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Ilari Liusvaara
- Re: [TLS] Security review of TLS1.3 0-RTT Eric Rescorla
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT David Benjamin
- Re: [TLS] Security review of TLS1.3 0-RTT Viktor Dukhovni
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Eric Rescorla
- Re: [TLS] Security review of TLS1.3 0-RTT Ilari Liusvaara
- Re: [TLS] Security review of TLS1.3 0-RTT Ilari Liusvaara
- Re: [TLS] Security review of TLS1.3 0-RTT Eric Rescorla
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Christian Huitema
- Re: [TLS] Security review of TLS1.3 0-RTT Kyle Nekritz
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Christian Huitema
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Benjamin Kaduk
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Christian Huitema
- Re: [TLS] Security review of TLS1.3 0-RTT Viktor Dukhovni
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Viktor Dukhovni
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Benjamin Kaduk
- Re: [TLS] Security review of TLS1.3 0-RTT Salz, Rich
- Re: [TLS] Security review of TLS1.3 0-RTT Salz, Rich
- Re: [TLS] Security review of TLS1.3 0-RTT Benjamin Kaduk
- Re: [TLS] Security review of TLS1.3 0-RTT Benjamin Kaduk
- Re: [TLS] Security review of TLS1.3 0-RTT Ilari Liusvaara
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Benjamin Kaduk
- Re: [TLS] Security review of TLS1.3 0-RTT Victor Vasiliev
- Re: [TLS] Security review of TLS1.3 0-RTT Dave Garrett
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Ilari Liusvaara
- Re: [TLS] Security review of TLS1.3 0-RTT Victor Vasiliev
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Bill Cox
- Re: [TLS] Security review of TLS1.3 0-RTT Ilari Liusvaara
- Re: [TLS] Security review of TLS1.3 0-RTT Victor Vasiliev
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Eric Rescorla
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Ilari Liusvaara
- Re: [TLS] Security review of TLS1.3 0-RTT Eric Rescorla
- Re: [TLS] Security review of TLS1.3 0-RTT Eric Rescorla
- Re: [TLS] Security review of TLS1.3 0-RTT Victor Vasiliev
- Re: [TLS] Security review of TLS1.3 0-RTT Victor Vasiliev
- Re: [TLS] Security review of TLS1.3 0-RTT Ilari Liusvaara
- Re: [TLS] Security review of TLS1.3 0-RTT Bill Cox
- Re: [TLS] Security review of TLS1.3 0-RTT Colm MacCárthaigh
- Re: [TLS] Security review of TLS1.3 0-RTT Benjamin Kaduk
- Re: [TLS] Security review of TLS1.3 0-RTT Benjamin Kaduk
- Re: [TLS] Security review of TLS1.3 0-RTT Benjamin Kaduk
- Re: [TLS] Security review of TLS1.3 0-RTT Bill Cox
- Re: [TLS] Security review of TLS1.3 0-RTT Yoav Nir