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Re: [TLS] Encrypting record headers: practical for TLS 1.3 after all?

mrex@sap.com (Martin Rex) Wed, 02 December 2015 18:48 UTC

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To: Jacob Appelbaum <jacob@appelbaum.net>
Date: Wed, 02 Dec 2015 19:48:39 +0100
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From: mrex@sap.com
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Cc: tls@ietf.org
Subject: Re: [TLS] Encrypting record headers: practical for TLS 1.3 after all?
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Jacob Appelbaum wrote:
> On 12/2/15, Martin Rex <mrex@sap.com> wrote:
>>
>> So your client will have to know a-priori, out-of-band or be configured
>> to TLSv1.3-only in order to avoid using a TLSv1.2-compatible ClientHello
>> with cleartext SNI.
> 
> I think that is false. One could easily use the "cleartext" SNI field
> and insert an encrypted value. A hash of the name would be a simple
> example but not a secure example, of course.

No you can NOT do this (in TLSv1.2 and earlier), because it is entirely
backwards-incompatible.

Server-side SNI can even be implemented completely outside of the TLS
protocol stack (that is how I implemented it).


> 
> To the point about TLS 1.2 vs TLS 1.3: Legacy clients will be less
> secure

That is a myth.

>
> and in ways that will only become worse over time. We should
> remember that TLS 1.3, while not yet finished or deployed, is a future
> legacy protocol.

TLSv1.3 is looking more and more like a future market failure to me,
worse than IPv6.


-Martin

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