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

[Thomas Frauendorfer]

On Fri, Mar 5, 2021 at 1:12 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>

[cut out]

>        /* 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

The lockdown verifier makes sure that at least one verifer has
validated the image.
So removing GRUB_FILE_TYPE_EFI_CHAINLOADED_IMAGE from it is a very bad idea.

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