Re: [TLS] chairs - please shutdown wiretapping discussion...

Tony Arcieri <bascule@gmail.com> Sat, 08 July 2017 17:34 UTC

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From: Tony Arcieri <bascule@gmail.com>
Date: Sat, 08 Jul 2017 17:34:00 +0000
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To: Russ Housley <housley@vigilsec.com>
Cc: IETF TLS <tls@ietf.org>
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Subject: Re: [TLS] chairs - please shutdown wiretapping discussion...
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On Sat, Jul 8, 2017 at 11:17 AM Russ Housley <housley@vigilsec.com>; wrote:

> I want to highlight that draft-green-tls-static-dh-in-tls13-01 does not
> enable MitM.  The server does not share the signing private key, so no
> other party can perform a valid handshake.
>

This method allows a middlebox to recover the plaintext of a TLS session.
While I took issue with Stephen's attempts to shut down conversations this
line of inquiry, I have a much, much stronger objection to downplay the
fact that this is still a self-inflicted MitM attack.

Let me be very clear: full plaintext recovery by a passive middlebox
absolutely is "MitM". Just because it does not allow full impersonation of
the server does not make it MitM. It is MitM, and we should be very clear
it is MitM.

Further, the server is choosing to use a (EC)DH key that was generated by
> the key manager, so it is quite different than the mandatory key escrow used
> in the Clipper Chip.
>

It enables the same ends: recovery of session plaintexts, and as I stated
on other threads I would personally prefer a more explicit key escrow
mechanism implemented as a TLS extension, which to some degree would
actually look a bit more like LEAP.

> --
Tony Arcieri