Re: [TLS] WGLC for draft-ietf-tls-exported-authenticator

Eric Rescorla <ekr@rtfm.com> Mon, 07 May 2018 16:07 UTC

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From: Eric Rescorla <ekr@rtfm.com>
Date: Mon, 07 May 2018 09:06:13 -0700
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To: Roelof duToit <r@nerd.ninja>
Cc: Benjamin Kaduk <bkaduk@akamai.com>, TLS WG <tls@ietf.org>
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Subject: Re: [TLS] WGLC for draft-ietf-tls-exported-authenticator
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Note that this is different from Token Binding because that's negotiated by
an extension, so per S 9.3, non-supporting middleboxes need to strip out
the extension

-Ekr


On Mon, May 7, 2018 at 8:06 AM, Roelof duToit <r@nerd.ninja> wrote:

>
> > On May 4, 2018, at 5:48 PM, Benjamin Kaduk <bkaduk@akamai.com> wrote:
> >
> > On Fri, May 04, 2018 at 11:20:55AM -0400, Roelof duToit wrote:
> >> How will this (and any mechanism built on top of RFC 5705 exported key
> material) interoperate with middleboxes?  This use of the mechanism is not
> negotiated on the TLS level, so there is no extension for the middlebox to
> strip that would warn the endpoints not to use exported authenticators.
> Are application level proxies the only compatible middleboxes?
> >
> > I'm not sure I properly understand the question, in particular what kind
> of
> > middlebox you're considering.  Note that application protocols will need
> to
> > have some way to negotiate the use of this functionality, which
> presumably a
> > middlebox could also inspect.
>
>
> That is the problem.. some middleboxes are protocol agnostic and are used
> to strip the TLS layer before feeding the rest of the security stack - so
> called “Transport Layer Active Intercept” vs “Application Layer Intercept”
> (ignoring “Transport Layer Passive Intercept” for the moment).  Some
> middleboxes might also perform transport layer active intercept in
> combination with passive application detection, i.e. L7 analysis vs L7
> termination.
> In summary: the endpoints cannot assume that exported key material is
> identical in a middlebox environment.
>
>
>
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