Re: [TLS] padding bug

Ben Laurie <benl@google.com> Mon, 09 September 2013 13:31 UTC

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Date: Mon, 9 Sep 2013 14:31:10 +0100
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From: Ben Laurie <benl@google.com>
To: Eric Rescorla <ekr@rtfm.com>
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Subject: Re: [TLS] padding bug
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On 9 September 2013 14:01, Eric Rescorla <ekr@rtfm.com> wrote:

> Ben,
>
> Generally, we're not doing advance code point assignments for documents
> that haven't been accepted by the TLS WG.
>
> Of course, this naturally raises the question of whether this document will
> be accepted by the TLS WG. However, as I think recent discussion indicates,
> there are a number of proposed approaches and there isn't really consensus
> to adopt this particular one (especially in view of the increased adoption
> of existing
> mechanisms such as GCM). If someone (Peter? You?) wants agenda time
> to argue for this particular approach instead of others, we're happy to
> have the
> discussion in YVR. This of course also applies to proponents of other
> approaches.
>

I'm not planning to be at YVR, what happened to using the mailing list for
discussion?

So, in favour of the WG adoption this I-D:

1. Nothing in this I-D prevents the adoption of other approaches.

2. If fixes the problem for all versions of TLS and SSLv3.

3. I've seen no objection that makes any sense. One objection I have seen
was that it "may not protect from key-recovery in a weak MAC construction"
- firstly, I am not aware of any such constructions in use in SSL/TLS, and
secondly, if there are any, it would be trivial to deprecate their use in
conjunction with this extension.

How about we take a vote?

Note, BTW, that unless convinced otherwise, we intend to implement this in
OpenSSL (it went into master yesterday), so you can consider that a vote in
favour :-)


> Best,
> -Ekr
>
> [As Chair]
>
>
>
> On Sun, Sep 8, 2013 at 10:57 AM, Ben Laurie <benl@google.com> wrote:
>
>>
>>
>>
>> On 8 September 2013 14:47, Dr Stephen Henson <lists@drh-consultancy.co.uk
>> > wrote:
>>
>>> On 08/09/2013 13:07, Dr Stephen Henson wrote:
>>> > On 08/09/2013 03:59, Peter Saint-Andre wrote:
>>> >> [old thread alert!]
>>> >>
>>> >>
>>> >>> 2.       An extension for Encrypt-then-MAC (i.e. this draft)
>>> >>
>>> >>> Was any consensus achieved as to the best approach?
>>> >>
>>> >
>>> > I can add a data point to this. I spent an afternoon implementing this
>>> (i.e.
>>> > the encrypt then mac draft) a while ago in OpenSSL. It was pretty easy
>>> to do
>>> > and interoped fine with the test servers.
>>> >
>>> > I'll make it available as an experimental feature in OpenSSL master
>>> branch.
>>> >
>>>
>>> Well I've added this and spotted a problem. The draft extension value
>>> (0x10)
>>> clashes with the draft value used in the ALPN specification.
>>>
>>
>> Given that the ALPN draft apparently has an allocated number, can we get
>> one allocated to this I-D?
>>
>>
>> _______________________________________________
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>> https://www.ietf.org/mailman/listinfo/tls
>>
>>
>