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Re: Challenge: Find potential use cases for non-trivial confinement


From: Bas Wijnen
Subject: Re: Challenge: Find potential use cases for non-trivial confinement
Date: Wed, 17 May 2006 15:14:04 +0200
User-agent: Mutt/1.5.11+cvs20060403

On Wed, May 17, 2006 at 01:56:48PM +0100, Sam Mason wrote:
> On Sun, Apr 30, 2006 at 11:17:53PM +0200, Marcus Brinkmann wrote:
> > Propose a use case for non-trivial confinement.
> 
>   How about the little (image) preview window that appears in some
>   graphical open file dialogs?
> 
> To me this seems as though the application would pass a capability to
> the open dialog naming a preview constructor in the calling application.

That is one way to implement it.  Another is to pass the preview code itself
(by reference, it shouldn't be copied if it isn't used).

> Non-trivial confinement is needed because the open dialog doesn't trust
> the calling program to not grant itself permission to the previewers
> address space and to pull information out of it after the user has
> selected a file.

If you remove the "non-trivial", I agree. :-)  I think this can easily be
implemented using trivial confinement as well, though.  Or am I missing
something?

Thanks,
Bas

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