[TLS] padding bug (was: Re: Requesting feedback on TACK draft)

Peter Saint-Andre <stpeter@stpeter.im> Sun, 08 September 2013 02:59 UTC

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Date: Sat, 07 Sep 2013 20:59:20 -0600
From: Peter Saint-Andre <stpeter@stpeter.im>
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Subject: [TLS] padding bug (was: Re: Requesting feedback on TACK draft)
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[old thread alert!]

On 7/1/13 3:02 AM, Lewis, Nick wrote:
>> While people are looking at that, there's also the
>> encrypt-then-MAC draft, 
>> http://www.ietf.org/internet-drafts/draft-gutmann-tls-encrypt-then-mac-03.txt,
>>
>> 
which has been stable for about as long, has already been deployed by
>> several vendors, and for which TLS extension 0x10 has been de
>> facto claimed, so it'd be good to get this published to
>> legitimise the use (and to document what's already being deployed
>> in production).
> 
> As I recall there were three proposals for resolving the padding
> bug in TLS
> 
> 1.       An extension for Pad First (i.e. padding before an
> otherwise standard TLS mode of operation)
> 
> 2.       An extension for Encrypt-then-MAC (i.e. this draft)
> 
> 3.       The replacement of each existing cipher suite with an 
> equivalent AEAD one
> 
> Was any consensus achieved as to the best approach?

I never saw further discussion on this topic. Are there I-Ds for each
approach? #3 seems onerous to me (and doubling the number of cipher
suites doesn't seem like a desirable outcome), and as far as I can
tell there's no specification for #1. Although I am not a TLS expert,
the Encrypt-then-MAC I-D referenced above seems reasonable, it neatly
solves a real-world problem, and we have running code; thus IMHO
formalization of this approach deserves to be considered in the WG.

Peter

- -- 
Peter Saint-Andre
https://stpeter.im/


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