Re: [TLS] PR#1091: Changes to provide middlebox robustness

Eric Rescorla <ekr@rtfm.com> Mon, 04 December 2017 12:04 UTC

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From: Eric Rescorla <ekr@rtfm.com>
Date: Mon, 4 Dec 2017 04:03:27 -0800
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To: Alex C <immibis@gmail.com>
Cc: Yuhong Bao <yuhongbao_386@hotmail.com>, Andrei Popov <Andrei.Popov@microsoft.com>, Peter Saint-Andre <stpeter@stpeter.im>, "tls@ietf.org" <tls@ietf.org>, Tapio Sokura <tapio.sokura@iki.fi>
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Subject: Re: [TLS] PR#1091: Changes to provide middlebox robustness
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On Mon, Dec 4, 2017 at 1:59 AM, Alex C <immibis@gmail.com>; wrote:

> The obvious problem with randomly adding fake versions is you have to have
> a way of ensuring they won't conflict with *real* future versions - and
> whatever pattern you decide upon in order to do that, middleboxes will use
> that pattern to filter out fake versions, and fail as soon as you present
> one with a real future version (i.e. TLS 1.4).
>
> Can I also suggest adding a section about expected middlebox behaviour to
> TLS 1.3? That way there is a reasonable chance that TLS 1.4 won't face the
> same issues.
> (Or can I do that myself? I'm not really familiar with the process, sorry)
>
>
Yes, you can send a a PR at:
https://github.com/tlswg/tls13-spec/

-Ekr


> On Sat, Nov 25, 2017 at 8:21 AM, Yuhong Bao <yuhongbao_386@hotmail.com>;
> wrote:
>
>> That only applies to the ClientHello.
>>
>> ________________________________________
>> From: Andrei Popov <Andrei.Popov@microsoft.com>;
>> Sent: Wednesday, November 22, 2017 11:22:23 AM
>> To: Yuhong Bao; Peter Saint-Andre; Eric Rescorla
>> Cc: tls@ietf.org; Tapio Sokura
>> Subject: RE: [TLS] PR#1091: Changes to provide middlebox robustness
>>
>> The idea was for the client to randomly add non-existent TLS versions to
>> supported_versions.
>> Presumably, this will exercise the extensibility joint and prevent it
>> from becoming unusable.
>>
>> I'm not convinced this new approach will help, but we know the old one
>> required fallbacks every time a new protocol version was introduced.
>>
>> Cheers,
>>
>> Andrei
>>
>> -----Original Message-----
>> From: TLS [mailto:tls-bounces@ietf.org] On Behalf Of Yuhong Bao
>> Sent: Wednesday, November 22, 2017 11:04 AM
>> To: Peter Saint-Andre <stpeter@stpeter.im>;; Eric Rescorla <ekr@rtfm.com>;
>> Cc: tls@ietf.org; Tapio Sokura <tapio.sokura@iki.fi>;
>> Subject: Re: [TLS] PR#1091: Changes to provide middlebox robustness
>>
>> They are basically doing a supported_versions extension with only one
>> entry in the ServerHello.
>> The problem with future middleboxes should be obvious.
>>
>> ________________________________________
>> From: Peter Saint-Andre <stpeter@stpeter.im>;
>> Sent: Wednesday, November 22, 2017 11:02:39 AM
>> To: Yuhong Bao; Eric Rescorla
>> Cc: tls@ietf.org; Tapio Sokura
>> Subject: Re: [TLS] PR#1091: Changes to provide middlebox robustness
>>
>> On 11/22/17 11:16 AM, Yuhong Bao wrote:
>> > The problem is not TLS 1.3, the problem is future versions of TLS.
>>
>> Would you mind explaining that in more detail?
>>
>> Peter
>>
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