Re: [dns-privacy] [TLS] Martin Duke's No Objection on draft-ietf-dprive-xfr-over-tls-11: (with COMMENT)

[Stephen Farrell <[e-mail]>]

On 29/04/2021 19:28, Salz, Rich wrote:
> To make it obvious (I thought it was): I agree, and think we need to
> make that fact more widely known.

I think I agree but seems like ECH may add a subtlety - maybe
what we need to promote is the idea that new protocols should
define new ALPN strings, but also that intermediaries can't
depend on those to route connections as the inner and outer
ALPN values can be independent in the case of ECH (use of
which might not that visible to the application if a library
were to default to use of ECH where possible).

Cheers,
S.

> 
> From: Eric Rescorla <[e-mail]> Date: Thursday, April 29, 2021 at
> 2:24 PM To: Rich Salz <[e-mail]> Cc: Martin Thomson
> <[e-mail]>, "[e-mail]" <[e-mail]>,
> "[e-mail]" <[e-mail]> Subject: Re: [dns-privacy] [TLS] Martin
> Duke's No Objection on draft-ietf-dprive-xfr-over-tls-11: (with
> COMMENT)
> 
> Probably not, but I agree with MT.
> 
> The general idea here is that any given protocol trace should only be
> interpretable in one way. So, either you need the interior protocol
> to be self-describing or you need to separate the domains with ALPN.
> I don't believe that either the IP ACL or mTLS addresses this issue,
> and in fact arguably mTLS makes the problem worse because it provides
> authenticated protocol traces which might be usable for
> cross-protocol attacks.
> 
> -Ekr
> 
> 
> On Thu, Apr 29, 2021 at 7:26 AM Salz, Rich
> <rsalz=[e-mail]<mailto:[e-mail]>>
> wrote:
>> No new protocol should use TLS without ALPN.  It only opens space
>> for cross-protocol attacks.  Did the working group consider this
>> possibility in their discussions?
> 
> I don't believe that message has been made as public as it should
> be.
> 
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