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Re: [TLS] The TLS_FALLBACK_SCSV time bomb (was: Re: Working Group Last Call for draft-ietf-tls-downgrade-scsv-00)

Andrei Popov <Andrei.Popov@microsoft.com> Fri, 17 October 2014 23:54 UTC

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From: Andrei Popov <Andrei.Popov@microsoft.com>
To: Marsh Ray <maray@microsoft.com>, Martin Thomson <martin.thomson@gmail.com>
Thread-Topic: [TLS] The TLS_FALLBACK_SCSV time bomb (was: Re: Working Group Last Call for draft-ietf-tls-downgrade-scsv-00)
Thread-Index: AQHP6g/vkqpMmvBKoUCxL3G2jHnzlpw0TqsAgABoBICAAAgfwIAACI2AgAAH2aCAACaKgIAAAF8g
Date: Fri, 17 Oct 2014 23:54:27 +0000
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References: <2112FCAD-4820-49D9-9871-6501C83A554D@cisco.com> <543F9893.806@redhat.com> <543FA0A0.1030205@polarssl.org> <543FCAED.50502@redhat.com> <2A0EFB9C05D0164E98F19BB0AF3708C71D39ECECB4@USMBX1.msg.corp.akamai.com> <5440E005.6000607@redhat.com> <180027849.13041583.1413544466157.JavaMail.zimbra@redhat.com> <CADMpkcL2mntDd0dOruziqF0F=xURnqGgd_YkpF+ONzz8v-wQ9Q@mail.gmail.com> <1354095824.13104897.1413553221955.JavaMail.zimbra@redhat.com> <CADMpkcLRCsfQSr0=f97kXJw3RwHN5A79MYQ2j7XaxPxUy2MCLg@mail.gmail.com> <CABkgnnUBYtWUY-CZDDzFiDpMWYbca74o6kejh2Q3L+FHVaHoOA@mail.gmail.com> <d8ce6c7437404bcbbea3a17e5c0b1582@BL2PR03MB419.namprd03.prod.outlook.com> <CABkgnnVJZhr3sD5iobbyLu-Vw3_i477zcbLFr-P+YB7RiKUtfg@mail.gmail.com> <7fe248e5b4374fbd8d04ff460bc3ace8@BL2PR03MB419.namprd03.prod.outlook.com> <76533ab02b644597a170cb5b76a42a99@BY2PR03MB554.namprd03.prod.outlook.com>
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Subject: Re: [TLS] The TLS_FALLBACK_SCSV time bomb (was: Re: Working Group Last Call for draft-ietf-tls-downgrade-scsv-00)
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Correct; however thanks to POODLE, these auto-downgrading client applications are rapidly removing SSL3 from the fallback sequence. So the reason for having SCSV (instead of a proper TLS extension) is disappearing.

-----Original Message-----
From: Marsh Ray 
Sent: Friday, October 17, 2014 4:49 PM
To: Andrei Popov; Martin Thomson
Cc: tls@ietf.org
Subject: RE: [TLS] The TLS_FALLBACK_SCSV time bomb (was: Re: Working Group Last Call for draft-ietf-tls-downgrade-scsv-00)

From: TLS [mailto:tls-bounces@ietf.org] On Behalf Of Andrei Popov
> It's not an RFC yet, so perhaps we should at least consider using a 
> TLS extension. SCSVs are ugly hacks. A simple TLS extension is 
> probably not much harder to implement than an SCSV, and may result in 
> cleaner code.

At least I think I remember hearing somewhere that
"SSLv3 without extensions" is one of the configurations that some of these auto-downgrading client applications fall back to.

- Marsh

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