linux-kernel - Re: [PATCH 1/5] MODSIGN: do not load mok when secure boot disabled

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Date:   Wed, 14 Mar 2018 18:23:52 +0800
From:   joeyli <jlee@...e.com>
To:     Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc:     "Lee, Chun-Yi" <joeyli.kernel@...il.com>,
        David Howells <dhowells@...hat.com>, linux-fs@...r.kernel.org,
        linux-efi@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Josh Boyer <jwboyer@...oraproject.org>,
        James Bottomley <James.Bottomley@...senpartnership.com>
Subject: Re: [PATCH 1/5] MODSIGN: do not load mok when secure boot disabled

Hi Ard, 

First! Thanks for your review!

On Tue, Mar 13, 2018 at 05:25:30PM +0000, Ard Biesheuvel wrote:
> On 13 March 2018 at 10:37, Lee, Chun-Yi <joeyli.kernel@...il.com> wrote:
> > The mok can not be trusted when the secure boot is disabled. Which
> > means that the kernel embedded certificate is the only trusted key.
> >
> > Due to db/dbx are authenticated variables, they needs manufacturer's
> > KEK for update. So db/dbx are secure when secureboot disabled.
> >
> 
> Did you consider the case where secure boot is not implemented? I
> don't think db/dbx are secure in that case, although perhaps it may
> not matter (a bit more information on the purpose of these patches and
> all the shim lingo etc would be appreciated)
> 

The patch 5 in this series checks that the db/dbx must have
EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS attribute. But I agree
with you that kernel should checks the SecureBoot variable must
exist in system. I will add patch to detect it.

> > Cc: David Howells <dhowells@...hat.com>
> > Cc: Josh Boyer <jwboyer@...oraproject.org>
> > Cc: James Bottomley <James.Bottomley@...senPartnership.com>
> > Signed-off-by: "Lee, Chun-Yi" <jlee@...e.com>
> > ---
> >  certs/load_uefi.c | 26 +++++++++++++++-----------
> >  1 file changed, 15 insertions(+), 11 deletions(-)
> >
> > diff --git a/certs/load_uefi.c b/certs/load_uefi.c
> > index 3d88459..d6de4d0 100644
> > --- a/certs/load_uefi.c
> > +++ b/certs/load_uefi.c
> > @@ -164,17 +164,6 @@ static int __init load_uefi_certs(void)
> >                 }
> >         }
> >
> > -       mok = get_cert_list(L"MokListRT", &mok_var, &moksize);
> 
> Which tree does this apply to? My tree doesn't have get_cert_list()
>

This patch set is base on the efi-lock-down and keys-uefi branchs in
David Howells's linux-fs git tree.
    https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=keys-uefi

Thanks a lot!
Joey Lee