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Re: [hybi] Masked framing VS mask in frame

"Pat McManus @Mozilla" <mcmanus@ducksong.com> Tue, 01 March 2011 14:37 UTC

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From: "Pat McManus @Mozilla" <mcmanus@ducksong.com>
To: Greg Wilkins <gregw@intalio.com>
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Date: Tue, 01 Mar 2011 09:37:47 -0500
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Cc: Hybi <hybi@ietf.org>
Subject: Re: [hybi] Masked framing VS mask in frame
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On Tue, 2011-03-01 at 15:42 +1100, Greg Wilkins wrote:
>   However, I do not think
> they have well communicated the technical case against it. 

* The mask increases the security properties of the protocol by making
it safe for transmission across transparent http proxies with certain
classes of bugs. This is true for both server (i.e. attacker) provided
data as well more generally true other data sources that should be
masked for transport across legacy http. The hybi archives might qualify
as such a data source. 

* The mask is incredibly cheap to implement. You can do XOR at the rate
of your memory bandwidth. The benefit to "optimizing it away" is at best
marginal even in high bandwidth scenarios.

* transparent and silent proxies are infrastructure elements and their
presence are not always known to clients at extension negotiation time.
Even clients such as websocket intermediaries may not be aware of them,
or they may come and go as routing schemes change.

--> consistent application of masking makes websockets a generally more
robust protocol at an insignificant cost. Creating a path for the
defense to be disabled is penny wise pound foolish.

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