linux-kernel - Re: [RFC v2 7/7] modsig: build rules and scripts to generate keys and sign modules

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Date:	Fri, 17 Aug 2012 13:52:23 -0400
From:	Josh Boyer <jwboyer@...il.com>
To:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
Cc:	"Kasatkin, Dmitry" <dmitry.kasatkin@...el.com>, jmorris@...ei.org,
	rusty@...tcorp.com.au, dhowells@...hat.com,
	linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC v2 7/7] modsig: build rules and scripts to generate keys and
 sign modules

On Fri, Aug 17, 2012 at 1:44 PM, Josh Boyer <jwboyer@...il.com> wrote:
>> I still think the signed_modules_install script, renamed to something
>> like ephemeral_signed_modules_install, is worthwhile and becomes a
>> convience tool for the developer, wanting to use ephemeral keys.  The
>> private key, in Dmitry's updated patches soon to be posted, will be
>> password protected with a random number, that is only accessible to the
>> current shell.
>
> I think the existence of an additional make target for signed modules
> is really confusing.  Particularly when you consider the target still
> exists even if the kernel isn't setup to work with signed modules.  If
> the config options are set, just have 'make modules_install' do it and
> create a key if one doesn't exist (or better yet, have 'make' do it).
>
> Also... password protecting the key that only responds to the current
> shell really sounds like a show-stopper for this being used by distros.
> There is no way a distro is going to be able to type a password in
> during a kernel build.  It completely removes the usability of distros
> that want to use a per-kernel build ephemeral key.  If you're going to
> do this, please wrap it in a kconfig option so the second distro case
> I mentio above is still possible.

Here's a suggestion that might help the discussion.  In the next
revision of the patch set, include a document in Documentation/ that
covers the module signing design, the purposes it's intended to fit,
and a high level description of the various module loading scenarios
(signed, unsigned, signed with a key not in the keyring, etc).  That
way we can at least see at a higher level what the thinking behind the
implemenation is.  I think some of our back and forth (while good!) is
because we see signed modules being used for different purposes.

josh
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