linux-kernel - Re: [PATCH] binfmt_misc: allow selecting the interpreter based on xattr keywords

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Date:   Fri, 26 Aug 2016 17:26:18 -0400
From:   James Bottomley <James.Bottomley@...senPartnership.com>
To:     One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
        Florian Weimer <fweimer@...hat.com>
Cc:     Josh Max <JMax@...l.greenriver.edu>, viro@...iv.linux.org.uk,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Carlos O'Donell <carlos@...hat.com>
Subject: Re: [PATCH] binfmt_misc: allow selecting the interpreter based on
 xattr keywords

On Fri, 2016-08-26 at 22:12 +0100, One Thousand Gnomes wrote:
> > A non-security use case would be to run the binary (without 
> > modification) with a different ELF interpreter (assuming this 
> > allows to override binfmt_elf, but self-sandboxing would need that 
> > as well).  This would make it easier to use older or newer libcs 
> > for select binaries on the system.  Right now, one has to write 
> > wrappers for that, and the explicit dynamic linker invocation is 
> > not completely transparent to the application.
> 
> If it gets in I'll be using it to label CP/M COM files so that they 
> can be auto-run nicely when crossbuilding stuff in part with the 
> original tools but a modern build environment 8)
> 
> Sandboxing is an obvious use but there are more bizarre ones such as
> marking a file system image to get auto-run under a virtual machine 
> or make containers fire up as if they were commands.

So I asked previously but didn't get an answer.  If this is useful for
sandboxing and being in the sandbox depends on the xattr value,
shouldn't it be in one of the privileged xattr namespaces, not the
user. one?

James


> It's effectively also the long missing but much needed "this document
> belongs to this app" meta data that MacOS and the like have had for
> decades.
> 
> Alan
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