Re: [PATCH] builddeb: Support signing kernels with a Machine Owner Key

[Ard Biesheuvel <ardb@kernel.org>]

(+ Peter)

On Thu, 6 May 2021 at 15:37, Matthew Wilcox <willy@infradead.org> wrote:
>
> On Thu, May 06, 2021 at 02:01:53PM +0200, Ard Biesheuvel wrote:
> > On Thu, 6 May 2021 at 14:00, Matthew Wilcox (Oracle)
> > <willy@infradead.org> wrote:
> > >
> > > If the config file specifies a signing key, use it to sign
> > > the kernel so that machines with SecureBoot enabled can boot.
> > > See https://wiki.debian.org/SecureBoot
> > >
> > > Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> > > ---
> > >  scripts/package/builddeb | 10 +++++++++-
> > >  1 file changed, 9 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/scripts/package/builddeb b/scripts/package/builddeb
> > > index 91a502bb97e8..4fa6ff2b5cac 100755
> > > --- a/scripts/package/builddeb
> > > +++ b/scripts/package/builddeb
> > > @@ -147,7 +147,15 @@ else
> > >         cp System.map "$tmpdir/boot/System.map-$version"
> > >         cp $KCONFIG_CONFIG "$tmpdir/boot/config-$version"
> > >  fi
> > > -cp "$($MAKE -s -f $srctree/Makefile image_name)" "$tmpdir/$installed_image_path"
> > > +
> > > +vmlinux=$($MAKE -s -f $srctree/Makefile image_name)
> > > +if is_enabled CONFIG_MODULE_SIG; then
> >
> > Shouldn't this be conditional on CONFIG_EFI as well?
>
> Maybe!  We're a long way outside my area of expertise.  I'm just chuffed
> I thought of using cut -d\" -f2.
>
> There should probably also be something conditional on sbsign actually
> being in $PATH, I guess?
>
> And I wasn't sure about putting all of this in builddeb -- does make
> rpm-pkg already have its own way of doing the same thing, or should this
> be somewhere more generic?
>

No, sbsign is Debian/Ubuntu specific. Fedora/Redhat uses something
else IIRC. But yes, it obviously helps if the tool exists.


> > > +       cert=$srctree/$(grep ^CONFIG_MODULE_SIG_KEY= include/config/auto.conf | cut -d\" -f2)
> > > +       key=${cert%pem}priv
> > > +       sbsign --key $key --cert $cert "$vmlinux" --output "$tmpdir/$installed_image_path"
> > > +else
> > > +       cp "$vmlinux" "$tmpdir/$installed_image_path"
> > > +fi
> > >
> > >  if is_enabled CONFIG_OF_EARLY_FLATTREE; then
> > >         # Only some architectures with OF support have this target
> > > --
> > > 2.30.2
> > >