Re: [secdir] secdir review of draft-ietf-httpbis-tunnel-protocol-04

Martin Thomson <martin.thomson@gmail.com> Wed, 10 June 2015 20:02 UTC

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Date: Wed, 10 Jun 2015 13:02:25 -0700
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From: Martin Thomson <martin.thomson@gmail.com>
To: Scott Kelly <scott@hyperthought.com>
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Cc: draft-ietf-httpbis-tunnel-protocol.all@tools.ietf.org, The IESG <iesg@ietf.org>, "secdir@ietf.org" <secdir@ietf.org>
Subject: Re: [secdir] secdir review of draft-ietf-httpbis-tunnel-protocol-04
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On 10 June 2015 at 12:09, Scott Kelly <scott@hyperthought.com> wrote:
>
> +          A proxy can use the value of the ALPN header field as input to
> +          authorization decisions.  The header field exposes protocol
> +          information at the HTTP layer, allowing authorization decisions to be
> +          made earlier, with better error reporting (such as a 403 status code).
>
> The term “authorization” evokes notions of security, at least for me. This text gives me the impression that the ALPN header is suitable for use in security decisions.
>
> I can think of a couple of ways to address this. One easy way is to replace “authorization” with something more security-neutral (“filtering”? “allow/deny”?). Another is to simply add a statement saying this header may be falsified by either the client or a MitM, and therefore should not be relied upon for security-relevant decisions unless additional security measures are applied.


Would it make more sense like this?

          A proxy can use the value of the ALPN header field to more cleanly and
          efficiently reject requests for a CONNECT tunnel.  Exposing protocol
          information at the HTTP layer allows a proxy to deny requests earlier,
          with better error reporting (such as a 403 status code).  The ALPN
          header field can be falsified and is therefore not sufficient basis
          for authorizing a request.