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Re: [AC] Access Control Algorithm

From: Thomas Roessler <tlr@w3.org>
Date: Mon, 21 May 2007 12:47:10 +0200
To: Jonas Sicking <jonas@sicking.cc>
Cc: Anne van Kesteren <annevk@opera.com>, "WAF WG (public)" <public-appformats@w3.org>
Message-ID: <20070521104710.GP23223@raktajino.does-not-exist.org>

On 2007-04-26 03:54:38 -0700, Jonas Sicking wrote:

> I think I was unclear. I don't expect access control to ever
> block access further than what browsers today already does. The
> simplest reason is that current, already released, browsers
> obviously ignore such headers/PIs and always will. So access
> control is not adequate to restrict data access further than
> browsers do today.

We're in wild agreement there.

> However once I deploy access control PIs/headers they allow other
> sites to read data from my server. But if I then realize that I
> have put errorous access control information in my files, for
> example not having a restrictive enough deny/exclude lists, or
> putting the PIs in too many files, it would be very useful to
> immediately being able block evil.com or any other site from 
> reading any of the files on the server.

> Another scenario is a server administrator for a server behind a
> firewall at a corporation wants to make sure that no data is
> accidentally leaked even though the employees are responsible for
> putting files on the server. The administrator could then add a
> access control header that denied all external servers from
> reading any data.

I can see the use case, but I wonder if it really warrants a change
to the access control language.

On the one hand, the currently proposed syntax would make an easy
programmatic change possible -- all you'd do is add evil.com to the

On the other hand, adding an order dependency and unscoped
exclusions would make the language more complex.  I wouldn't be
surprised to see bug reports coming in against implementations that
claim brokenness because an unscoped "exclude" doesn't have whatever
effect an author might have desired...

Thomas Roessler, W3C  <tlr@w3.org>
Received on Monday, 21 May 2007 10:47:17 UTC

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