Re: [TLS] Data volume limits

Florian Weimer <fweimer@redhat.com> Mon, 04 January 2016 12:03 UTC

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To: Hubert Kario <hkario@redhat.com>
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From: Florian Weimer <fweimer@redhat.com>
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Date: Mon, 4 Jan 2016 13:02:57 +0100
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Subject: Re: [TLS] Data volume limits
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On 01/04/2016 12:59 PM, Hubert Kario wrote:
> On Monday 28 December 2015 21:08:10 Florian Weimer wrote:
>> On 12/21/2015 01:41 PM, Hubert Kario wrote:
>>> if the rekey doesn't allow the application to change authentication
>>> tokens (as it now stands), then rekey is much more secure than
>>> renegotiation was in TLS <= 1.2
>>
>> You still have the added complexity that during rekey, you need to
>> temporarily switch from mere sending or receiving to at least
>> half-duplex interaction.
> 
> this situation already happens in initial handshake so the 
> implementation needs to support that

But after and the handshake and without real re-key, sending and
receiving operations exactly match what the application requests.  If
you need to switch directions against the application's wishes, you end
up with an API like OpenJDK's SSLEngine (or a callback variant which is
equivalent in complexity).

Dealing with this during the initial handshake is fine.  But supporting
direction-switching after that is *really* difficult.

Florian