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From: David Howells <dhowells@redhat.com>
In-Reply-To: <87obpfxdpr.fsf@rustcorp.com.au>
References: <87obpfxdpr.fsf@rustcorp.com.au> <20120522230218.24007.3556.stgit@warthog.procyon.org.uk>
To: Rusty Russell <rusty@rustcorp.com.au>
Cc: dhowells@redhat.com, kyle@mcmartin.ca, linux-kernel@vger.kernel.org,
        linux-security-module@vger.kernel.org, keyrings@linux-nfs.org
Subject: Re: [PATCH 00/23] Crypto keys and module signing
Date: Wed, 23 May 2012 15:20:47 +0100
Message-ID: <7474.1337782847@redhat.com>
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1423
Lines: 30

Rusty Russell <rusty@rustcorp.com.au> wrote:

>         That's pretty weird.  Why not put the "@This Is A Crypto Signed
> Module\n" before the signature?  Then module-size is implied: everything
> before that signature.  The signature size is implied: everything after
> that signature.

This makes it simpler.  No scanning required.  The magic number can only be in
one place and you can find it by dead reckoning.

>         In fact, I'd modify this slightly, to allow multiple signatures.
> This would work nicely with a deterministic strip.  Find the signatures
> backward, and truncate as they fail.

Why would you want multiple signatures?  That just complicates things.  If
you're in FIPS mode, you probably have to panic if any of them fail.

I suppose I may as well punt the signature detection and removal to userspace
and pass the signature as an argument to init_module() as Dmitry suggested.
Then the signature need not be in the file at all (he wants to use an xattr or
hardware, I think).  mkinitrd and rpmbuild/kernel spec have to be changed to
accommodate enablement of these patches, so why not module-init-tools, dracut
and busybox whilst we're at it?

David
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