Re: [TLS] Downgrade protection, fallbacks, and server time
Hubert Kario <hkario@redhat.com> Thu, 02 June 2016 10:40 UTC
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From: Hubert Kario <hkario@redhat.com>
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Date: Thu, 02 Jun 2016 12:39:57 +0200
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Subject: Re: [TLS] Downgrade protection, fallbacks, and server time
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On Wednesday 01 June 2016 22:29:06 David Benjamin wrote: > In case folks hoped we could bump the ClientHello version without > those dreaded browser fallbacks, I have bad news. :-( 1.3 intolerance > very much exists. (Maybe we should just give up on > ClientHello.version and use an extension? Extensions have rusted > less.) > > I picked a large list of top sites and tried connecting to them. Just > under 2% of them could handle a TLS 1.2 ClientHello, but not the same > ClientHello with the version switched to 1.3 (no other changes, so I > haven't tested a real 1.3 ClientHello). They're not unknown hosts > either. I expect if you probe any top site list, you'll very quickly > find some. there are also servers which choke on large extensions (say 4096 bit DH client key share with 384 bit ECDH key share), so avoiding the bump in version number won't solve all the problems either... Speaking of version number, does the text say that a server _MUST_ accept any version higher than the one that is specified in the RFC, but reply with 0x03,0x04 in case it doesn't support any future version of the protocol? It would be nice to have some kind of stick for the broken implementations... -- Regards, Hubert Kario Senior Quality Engineer, QE BaseOS Security team Web: www.cz.redhat.com Red Hat Czech s.r.o., Purkyňova 99/71, 612 45, Brno, Czech Republic
- Re: [TLS] Downgrade protection, fallbacks, and se… David Benjamin
- Re: [TLS] Downgrade protection, fallbacks, and se… Martin Rex
- [TLS] Downgrade protection, fallbacks, and server… David Benjamin
- Re: [TLS] Downgrade protection, fallbacks, and se… Eric Rescorla
- Re: [TLS] Downgrade protection, fallbacks, and se… David Benjamin
- Re: [TLS] Downgrade protection, fallbacks, and se… Eric Rescorla
- Re: [TLS] Downgrade protection, fallbacks, and se… Martin Thomson
- [TLS] no fallbacks please [was: Downgrade protect… Nikos Mavrogiannopoulos
- Re: [TLS] no fallbacks please [was: Downgrade pro… Yoav Nir
- Re: [TLS] Downgrade protection, fallbacks, and se… Hubert Kario
- Re: [TLS] no fallbacks please [was: Downgrade pro… Hubert Kario
- Re: [TLS] Downgrade protection, fallbacks, and se… David Benjamin
- Re: [TLS] Downgrade protection, fallbacks, and se… Viktor Dukhovni
- Re: [TLS] no fallbacks please [was: Downgrade pro… David Benjamin
- Re: [TLS] Downgrade protection, fallbacks, and se… David Benjamin
- Re: [TLS] Downgrade protection, fallbacks, and se… Hubert Kario
- Re: [TLS] no fallbacks please [was: Downgrade pro… David Benjamin
- Re: [TLS] Downgrade protection, fallbacks, and se… David Benjamin
- Re: [TLS] no fallbacks please [was: Downgrade pro… Hubert Kario
- Re: [TLS] no fallbacks please [was: Downgrade pro… Hubert Kario
- Re: [TLS] Downgrade protection, fallbacks, and se… Viktor Dukhovni
- Re: [TLS] no fallbacks please [was: Downgrade pro… Martin Thomson
- Re: [TLS] no fallbacks please [was: Downgrade pro… Dave Garrett
- Re: [TLS] no fallbacks please [was: Downgrade pro… Nikos Mavrogiannopoulos
- Re: [TLS] no fallbacks please [was: Downgrade pro… Ilari Liusvaara
- Re: [TLS] no fallbacks please [was: Downgrade pro… Hubert Kario
- Re: [TLS] no fallbacks please [was: Downgrade pro… Xiaoyin Liu
- Re: [TLS] no fallbacks please [was: Downgrade pro… Hubert Kario
- Re: [TLS] no fallbacks please [was: Downgrade pro… Eric Rescorla
- Re: [TLS] no fallbacks please [was: Downgrade pro… Andrei Popov
- Re: [TLS] no fallbacks please [was: Downgrade pro… Eric Rescorla
- Re: [TLS] no fallbacks please [was: Downgrade pro… Viktor Dukhovni
- Re: [TLS] no fallbacks please [was: Downgrade pro… David Benjamin
- Re: [TLS] no fallbacks please [was: Downgrade pro… Dave Garrett
- Re: [TLS] no fallbacks please [was: Downgrade pro… Bill Frantz
- Re: [TLS] Downgrade protection, fallbacks, and se… Yaron Sheffer
- Re: [TLS] Downgrade protection, fallbacks, and se… Stefan Winter
- Re: [TLS] no fallbacks please [was: Downgrade pro… Hubert Kario
- Re: [TLS] [FORGED] Re: no fallbacks please [was: … Peter Gutmann
- Re: [TLS] [FORGED] Re: no fallbacks please [was: … Peter Gutmann
- Re: [TLS] no fallbacks please [was: Downgrade pro… Dave Garrett
- Re: [TLS] no fallbacks please [was: Downgrade pro… Jeffrey Walton
- Re: [TLS] [FORGED] Re: no fallbacks please [was: … Peter Gutmann
- Re: [TLS] [FORGED] Re: no fallbacks please [was: … Kyle Rose
- Re: [TLS] [FORGED] Re: no fallbacks please [was: … Hubert Kario
- Re: [TLS] [FORGED] Re: no fallbacks please [was: … Yoav Nir
- Re: [TLS] [FORGED] Re: no fallbacks please [was: … Salz, Rich
- Re: [TLS] [FORGED] Re: no fallbacks please [was: … Yoav Nir
- Re: [TLS] [FORGED] Re: no fallbacks please [was: … Hubert Kario
- Re: [TLS] [FORGED] Re: no fallbacks please [was: … Yoav Nir
- Re: [TLS] [FORGED] Re: no fallbacks please [was: … David Benjamin
- Re: [TLS] [FORGED] Re: no fallbacks please [was: … Andrei Popov
- Re: [TLS] [FORGED] Re: no fallbacks please [was: … Yuhong Bao
- Re: [TLS] [FORGED] Re: no fallbacks please [was: … Dave Garrett
- Re: [TLS] [FORGED] Re: no fallbacks please [was: … Hubert Kario
- Re: [TLS] [FORGED] Re: no fallbacks please [was: … Hubert Kario
- Re: [TLS] [FORGED] Re: no fallbacks please [was: … Nikos Mavrogiannopoulos
- Re: [TLS] no fallbacks please [was: Downgrade pro… Tony Arcieri