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

[Masahiro Yamada]

On Fri, Dec 17, 2021 at 7:04 AM Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote:
>
> On Thu, Nov 04, 2021 at 06:28:40PM +0900, Masahiro Yamada wrote:
> > On Thu, Oct 14, 2021 at 6:47 PM Ard Biesheuvel <ardb@xxxxxxxxxx> wrote:
> > >
> > > On Wed, 13 Oct 2021 at 22:07, Matthew Wilcox (Oracle)
> > > <willy@xxxxxxxxxxxxx> 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@xxxxxxxxxxxxx>
> > >
> > > For the change itself
> > >
> > > Acked-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
> > >
> > > although I'd suggest to fix the subject not to refer to Machine Owner
> > > Keys, as I don't see anything shim related here (i.e., if you sign
> > > using a key that is listed in db, it should also work)
> > >
> > >
> > > > ---
> > > >  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 $srctree/Makefile image_name)
> > > > +if is_enabled CONFIG_MODULE_SIG; then
> > > > +       cert=$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
> > > > --
> > > > 2.32.0
> > > >
> >
> > How to compile this patch?
> >
> > "make  bindeb-pkg" fails with
> > Can't load key from file './certs/signing_key.priv'
>
> I'm sorry; I missed this email.
>
> I don't know why you're seeing this error, exactly.  I'm just trying to
> automate the step here:

[1] Apply your patch
[2] Enable CONFIG_MODULE_SIG
[3] make bindeb-pkg

That's all.


> https://wiki.debian.org/SecureBoot#Using_your_key_to_sign_your_kernel
>
> Have you followed the other steps on that page; ie do you have:
> signing_key.priv, signing_key.der and signing_key.pem files?



certs/signing_key.pem is automatically generated by Kbuild.

There is no such file as signing_key.priv


You can see the content of certs/signing_key.pem
This file contains both certificate and private key.






>
> >
> > Also, sbsign emits "Invalid DOS header magic" error
> > if CONFIG_EFI_STUB is not set.
> >
> > The CONFIG name might depend on arch.
> > CONFIG_EFI for ARCH=arm64, but CONFIG_EFI_STUB for ARCH=x86.
> >
> >
> > If you require sbsign, you need to update Build-Depends ?
>
> It looks like we should add a few extra checks before running sbsign ...
>
> > sh ./scripts/package/builddeb
> > Can't load key from file './certs/signing_key.priv'
> > 139999825022720:error:02001002:system library:fopen:No such file or
> > directory:../crypto/bio/bss_file.c:69:fopen('./certs/signing_key.priv','r')
> > 139999825022720:error:2006D080:BIO routines:BIO_new_file:no such
> > file:../crypto/bio/bss_file.c:76:
> > make[4]: *** [scripts/Makefile.package:87: intdeb-pkg] Error 1
> > make[3]: *** [Makefile:1539: intdeb-pkg] Error 2
> > make[2]: *** [debian/rules:13: binary-arch] Error 2
> > dpkg-buildpackage: error: debian/rules binary subprocess returned exit status 2
> > make[1]: *** [scripts/Makefile.package:83: bindeb-pkg] Error 2
> > make: *** [Makefile:1539: bindeb-pkg] Error 2
>
>


-- 
Best Regards
Masahiro Yamada