Re: [TLS] Data volume limits

Florian Weimer <fweimer@redhat.com> Thu, 07 January 2016 10:45 UTC

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To: Benjamin Kaduk <bkaduk@akamai.com>
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From: Florian Weimer <fweimer@redhat.com>
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Date: Thu, 7 Jan 2016 11:45:04 +0100
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Subject: Re: [TLS] Data volume limits
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On 01/06/2016 01:56 AM, Benjamin Kaduk wrote:
> On 01/04/2016 06:22 AM, Florian Weimer wrote:
>> On 01/04/2016 01:19 PM, Hubert Kario wrote:
>>
>>>> Dealing with this during the initial handshake is fine.  But
>>>> supporting direction-switching after that is *really* difficult.
>>> yes, this is a bit more problematic, especially for one-sided transfers. 
>>> For example, when one side is just sending a multi-gigabyte transfer as 
>>> a reply to a single command - there may be megabytes transferred before 
>>> the other side reads our request for rekey and then our "CCS" message
>> Yes, this is the issue I meant.  I simply don't see a way to re-inject
>> new randomness without a round-trip.  (Key update without new randomness
>> doesn't face this challenge, but then it's mostly cheating.)
>>
> 
> EKR asked for an explanation of what risk you want to mitigate by adding
> new randomness on the 28th of December, but I don't recall seeing an
> explanation.

I tried, but maybe it's not clear.

Anyway, I don't see the current key update mechanism provides much
value.  I don't think it is desirable to have a full re-key mechanism
with the complexity it involves.

Florian