linux-kernel - Re: [PATCH 10/8] modsign: Allow password to be specified for signing key

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Date:	Tue, 19 May 2015 17:15:12 +0100
From:	David Woodhouse <dwmw2@...radead.org>
To:	Petko Manolov <petkan@...-labs.com>
Cc:	dhowells@...hat.com, rusty@...tcorp.com.au, mmarek@...e.cz,
	mjg59@...f.ucam.org, keyrings@...ux-nfs.org,
	dmitry.kasatkin@...il.com, mcgrof@...e.com,
	linux-kernel@...r.kernel.org, seth.forshee@...onical.com,
	linux-security-module@...r.kernel.org
Subject: Re: [PATCH 10/8] modsign: Allow password to be specified for
 signing key

On Tue, 2015-05-19 at 18:50 +0300, Petko Manolov wrote:
> On 15-05-19 15:45:58, David Woodhouse wrote:
> > We don't want this in the Kconfig since it might then get exposed in
> > /proc/config.gz. So make it a parameter to Kbuild instead. This also
> > means we don't have to jump through hoops to strip quotes from it, as
> > we would if it was a config option.
> 
> If it were on a network-less, secure sign/build server i'd say it is OK.  
> 
> However, exposing your private key's password in an environment variable on a 
> regular Linux box is a bit fishy.

I don't quite understand the objection.

If you want the modules to be signed with an external key of your
choice, then for the duration of the 'make modules_sign' run (or 'make
modules_install if CONFIG_MODULE_SIG_ALL=y) surely the password has to
be available *somehow*? 

You are, of course, free to sign the modules by invoking sign-file
directly. In which case you *still* need to provide it with the password
for the key somehow, if there is one.

Mimi quite rightly pointed out that my original mechanism for this, a
CONFIG_MODULE_SIG_KEY_PASSWORD option, was inadvertently exposing it
more than was necessary.

As it is now, you *only* need it in the environment for the duration of
the operations that actually *use* it.

Do you have a better suggestion?

-- 
David Woodhouse                            Open Source Technology Centre
David.Woodhouse@...el.com                              Intel Corporation

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