linux-kernel - Re: Firmware signing -- Re: [PATCH 00/27] security, efi: Add kernel lockdown

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Message-ID: <20171114123856.GA31142@kroah.com>
Date:   Tue, 14 Nov 2017 13:38:56 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Mimi Zohar <zohar@...ux.vnet.ibm.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        David Howells <dhowells@...hat.com>,
        Alan Cox <gnomes@...rguk.ukuu.org.uk>,
        "Luis R. Rodriguez" <mcgrof@...nel.org>,
        "AKASHI, Takahiro" <takahiro.akashi@...aro.org>,
        Jan Blunck <jblunck@...radead.org>,
        Julia Lawall <julia.lawall@...6.fr>,
        Marcus Meissner <meissner@...e.de>, Gary Lin <GLin@...e.com>,
        LSM List <linux-security-module@...r.kernel.org>,
        linux-efi <linux-efi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Matthew Garrett <mjg59@...gle.com>
Subject: Re: Firmware signing -- Re: [PATCH 00/27] security, efi: Add kernel
 lockdown

On Tue, Nov 14, 2017 at 07:21:38AM -0500, Mimi Zohar wrote:
> On Mon, 2017-11-13 at 14:09 -0800, Linus Torvalds wrote:
> > On Mon, Nov 13, 2017 at 1:44 PM, David Howells <dhowells@...hat.com> wrote:
> > >
> > > Whilst that may be true, we either have to check signatures on every bit of
> > > firmware that the appropriate driver doesn't say is meant to be signed or not
> > > bother.
> > 
> > I vote for "not bother".
> > 
> > Seriously, if you have firmware in /lib/firmware, and you don't trust
> > it, what the hell are you doing?
> 
> I might "trust" the files in /lib/firmware, but I also want to make
> sure that they haven't changed.  File signatures provide file
> provenance and integrity guarantees.

Then "verify" them with signatures that you generate yourself.  Like
dm-verify does for the partition that you put the firmware on.

thanks,

greg k-h