Re: [PATCH] Add chainloaded image as shim's verifiable object

[Dimitri John Ledkov]

This is not an oversight but intentional.

Currently there is no chainloader support with SBAT as further
development is required to ensure policy is applied correctly. Once
SBAT support for chainloading is defined, it will be introduced.

And yes it is intended to continue to allow "boot windows" as the menu
entry in grub.

On Fri, Mar 5, 2021 at 12:12 PM Michael Chang via Grub-devel
<grub-devel@gnu.org> wrote:
>
> While attempting to dual boot Microsoft Windows with efi chainloader, it
> failed with below error when secure boot was enabled.
>
> error ../../grub-core/kern/verifiers.c:119:verification requested but
> nobody cares: /EFI/Microsoft/Boot/bootmgfw.efi.
>
> It is a regression, as previously it worked without problem.
>
> It turns out chainloading image has been locked down introduced by
>
> 578c95298 kern: Add lockdown support
>
> However we should consider it as verifiable object to shim to allow
> booting in secure boot enabled mode. The chainloaded image could also
> have trusted signature signed by vendor with their pubkey cert in db.
> For that matters it's usage should not be locked down in secure boot,
> and instead use shim to validate it's signature before running it.
>
> Signed-off-by: Michael Chang <mchang@suse.com>
> ---
>  grub-core/kern/efi/sb.c   | 1 +
>  grub-core/kern/lockdown.c | 1 -
>  2 files changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/grub-core/kern/efi/sb.c b/grub-core/kern/efi/sb.c
> index 41dadcd14..96d237722 100644
> --- a/grub-core/kern/efi/sb.c
> +++ b/grub-core/kern/efi/sb.c
> @@ -129,6 +129,7 @@ shim_lock_verifier_init (grub_file_t io __attribute__ 
> ((unused)),
>      case GRUB_FILE_TYPE_BSD_KERNEL:
>      case GRUB_FILE_TYPE_XNU_KERNEL:
>      case GRUB_FILE_TYPE_PLAN9_KERNEL:
> +    case GRUB_FILE_TYPE_EFI_CHAINLOADED_IMAGE:
>        *flags = GRUB_VERIFY_FLAGS_SINGLE_CHUNK;
>
>        /* Fall through. */
> diff --git a/grub-core/kern/lockdown.c b/grub-core/kern/lockdown.c
> index 0bc70fd42..e1fd1c1e2 100644
> --- a/grub-core/kern/lockdown.c
> +++ b/grub-core/kern/lockdown.c
> @@ -48,7 +48,6 @@ lockdown_verifier_init (grub_file_t io __attribute__ 
> ((unused)),
>      case GRUB_FILE_TYPE_PXECHAINLOADER:
>      case GRUB_FILE_TYPE_PCCHAINLOADER:
>      case GRUB_FILE_TYPE_COREBOOT_CHAINLOADER:
> -    case GRUB_FILE_TYPE_EFI_CHAINLOADED_IMAGE:
>      case GRUB_FILE_TYPE_ACPI_TABLE:
>      case GRUB_FILE_TYPE_DEVICE_TREE_IMAGE:
>        *flags = GRUB_VERIFY_FLAGS_DEFER_AUTH;
> --
> 2.26.2
>
>
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-- 
Regards,

Dimitri.