On Tue, Apr 03, 2018 at 08:44:41AM -0700, James Bottomley wrote:
> On Tue, 2018-04-03 at 16:39 +0200, Daniel Kiper wrote:
> > Initialize UEFI secure boot state during dom0 boot. Otherwise the
> > kernel
> > may not even know that it runs on secure boot enabled platform.
> >
> > Signed-off-by: Daniel Kiper <daniel.kiper@xxxxxxxxxx>
> > ---
> > arch/x86/xen/efi.c | 57
> > +++++++++++++++++++++++++++++
> > drivers/firmware/efi/libstub/secureboot.c | 3 ++
> > 2 files changed, 60 insertions(+)
> >
> > diff --git a/arch/x86/xen/efi.c b/arch/x86/xen/efi.c
> > index a18703b..1804b27 100644
> > --- a/arch/x86/xen/efi.c
> > +++ b/arch/x86/xen/efi.c
> > @@ -115,6 +115,61 @@ static efi_system_table_t __init
> > *xen_efi_probe(void)
> > return &efi_systab_xen;
> > }
> >
> > +/*
> > + * Determine whether we're in secure boot mode.
> > + *
> > + * Please keep the logic in sync with
> > + * drivers/firmware/efi/libstub/secureboot.c:efi_get_secureboot().
> > + */
> > +static enum efi_secureboot_mode xen_efi_get_secureboot(void)
> > +{
> > + static efi_guid_t efi_variable_guid =
> > EFI_GLOBAL_VARIABLE_GUID;
> > + static efi_guid_t shim_guid = EFI_SHIM_LOCK_GUID;
> > + efi_status_t status;
> > + u8 moksbstate, secboot, setupmode;
> > + unsigned long size;
> > +
> > + size = sizeof(secboot);
> > + status = efi.get_variable(L"SecureBoot", &efi_variable_guid,
> > + NULL, &size, &secboot);
> > +
> > + if (status == EFI_NOT_FOUND)
> > + return efi_secureboot_mode_disabled;
> > +
> > + if (status != EFI_SUCCESS)
> > + goto out_efi_err;
> > +
> > + size = sizeof(setupmode);
> > + status = efi.get_variable(L"SetupMode", &efi_variable_guid,
> > + NULL, &size, &setupmode);
> > +
> > + if (status != EFI_SUCCESS)
> > + goto out_efi_err;
> > +
> > + if (secboot == 0 || setupmode == 1)
> > + return efi_secureboot_mode_disabled;
> > +
> > + /* See if a user has put the shim into insecure mode. */
> > + size = sizeof(moksbstate);
> > + status = efi.get_variable(L"MokSBStateRT", &shim_guid,
> > + NULL, &size, &moksbstate);
> > +
> > + /* If it fails, we don't care why. Default to secure. */
> > + if (status != EFI_SUCCESS)
> > + goto secure_boot_enabled;
> > +
> > + if (moksbstate == 1)
> > + return efi_secureboot_mode_disabled;
> > +
> > + secure_boot_enabled:
> > + pr_info("UEFI Secure Boot is enabled.\n");
> > + return efi_secureboot_mode_enabled;
> > +
> > + out_efi_err:
> > + pr_err("Could not determine UEFI Secure Boot status.\n");
> > + return efi_secureboot_mode_unknown;
> > +}
> > +
>
> This looks like a bad idea: you're duplicating the secure boot check in
>
> drivers/firmware/efi/libstub/secureboot.c
>
> Which is an implementation of policy. If we have to have policy in the
> kernel, it should really only be in one place to prevent drift; why
> can't you simply use the libstub efi_get_secureboot() so we're not
> duplicating the implementation of policy?
Well, here is the first version of this patch: https://lkml.org/lkml/2018/1/9/496
Ard did not like it. I was not happy too. In general both approaches are not perfect.
More you can find in the discussion around this patchset. If you have better idea
how to do that I am happy to implement it.
Daniel
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