[PATCH] efi_loader: update SetVariable attribute check

[Masahisa Kojima]

On Tue, 14 Feb 2023 at 20:15, Heinrich Schuchardt <xypron.glpk at gmx.de> wrote:
>
> On 2/14/23 10:19, Masahisa Kojima wrote:
> > UEFI specification v2.10 says that
> > EFI_VARIABLE_AUTHENTICATED_WRITE_ACCESS is deprecated and
> > EFI_UNSUPPORTED should be returned in SetVariable variable service.
> > Current implementation returns EFI_INVALID_PARAMETER,
> > let's fix the return value.
> >
> > Together with above change, this commit also updates the SetVariable
> > attribute check to be aligned with the EDK2 reference implementation.
> >
> > Signed-off-by: Masahisa Kojima <masahisa.kojima at linaro.org>
> > ---
> >   lib/efi_loader/efi_variable.c | 30 +++++++++++++++++++++++-------
> >   1 file changed, 23 insertions(+), 7 deletions(-)
> >
> > diff --git a/lib/efi_loader/efi_variable.c b/lib/efi_loader/efi_variable.c
> > index 4c85cfa607..1076ff7585 100644
> > --- a/lib/efi_loader/efi_variable.c
> > +++ b/lib/efi_loader/efi_variable.c
> > @@ -230,9 +230,28 @@ efi_status_t efi_set_variable_int(const u16 *variable_name,
> >       u64 time = 0;
> >       enum efi_auth_var_type var_type;
> >
> > -     if (!variable_name || !*variable_name || !vendor ||
> > -         ((attributes & EFI_VARIABLE_RUNTIME_ACCESS) &&
> > -          !(attributes & EFI_VARIABLE_BOOTSERVICE_ACCESS)))
> > +     if (!variable_name || !*variable_name || !vendor)
> > +             return EFI_INVALID_PARAMETER;
> > +
> > +     if (data_size != 0 && !data)
>
> We tend to not use '!= 0' and ' == 0' in logical constraints. You could use
>
>     if (data_size && !data)
>
> instead.

OK.

>
> > +             return EFI_INVALID_PARAMETER;
> > +
> > +     /* EFI_VARIABLE_AUTHENTICATED_WRITE_ACCESS is deprecated */
> > +     if (attributes & EFI_VARIABLE_AUTHENTICATED_WRITE_ACCESS ||
> > +         ((attributes & EFI_VARIABLE_MASK) == 0))
>
> !(attributes & EFI_VARIABLE_MASK)

OK.

>
> > +             return EFI_UNSUPPORTED;
> > +
> > +     /* Make sure if runtime bit is set, boot service bit is set also */
> > +     if ((attributes &
> > +          (EFI_VARIABLE_RUNTIME_ACCESS | EFI_VARIABLE_BOOTSERVICE_ACCESS)) ==
> > +         EFI_VARIABLE_RUNTIME_ACCESS)
> > +             return EFI_INVALID_PARAMETER;
> > +
> > +     /* only EFI_VARIABLE_NON_VOLATILE attribute is invalid */
> > +     if ((attributes & EFI_VARIABLE_MASK) == EFI_VARIABLE_NON_VOLATILE)
> > +             return EFI_INVALID_PARAMETER;
> > +
> > +     if (attributes & EFI_VARIABLE_HARDWARE_ERROR_RECORD)
> >               return EFI_INVALID_PARAMETER;
>
> Variables with flags NV, BS, RT, HR, name HwErrRec####, and GUID
> EFI_HARDWARE_ERROR_VARIABLE are allowable according to the UEFI spec.
> Why do we return EFI_INVALID_PARAMETER here?

Sorry, I misunderstood EDK2 implementation.
I will update to check HR must be set with NV.

454a9442fb(efi_loader: update attribute check for QueryVariableInfo()) also does
wrong check for HR, I will fix it.

>
> Please, sort the checks above such that all EFI_INVALID_PARAMETER are
> together followed by EFI_UNSUPPORTED.

SCT SIE(Security Interface Extension) expects that deprecated
EFI_VARIABLE_AUTHENTICATED_WRITE_ACCESS attribute check is first priority.
So let me prioritise EFI_VARIABLE_AUTHENTICATED_WRITE_ACCESS check.
In the next version, the error check order is:
 - basic parameter check such as variable_name is NULL
 - deprecated and unsupported attribute check
 - invalid attribute check

Thanks,
Masahisa Kojima

>
> Best regards
>
> Heinrich
>
> >
> >       /* check if a variable exists */
> > @@ -281,8 +300,6 @@ efi_status_t efi_set_variable_int(const u16 *variable_name,
> >
> >       /* authenticate a variable */
> >       if (IS_ENABLED(CONFIG_EFI_SECURE_BOOT)) {
> > -             if (attributes & EFI_VARIABLE_AUTHENTICATED_WRITE_ACCESS)
> > -                     return EFI_INVALID_PARAMETER;
> >               if (attributes &
> >                   EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS) {
> >                       u32 env_attr;
> > @@ -300,8 +317,7 @@ efi_status_t efi_set_variable_int(const u16 *variable_name,
> >               }
> >       } else {
> >               if (attributes &
> > -                 (EFI_VARIABLE_AUTHENTICATED_WRITE_ACCESS |
> > -                  EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS)) {
> > +                 EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS) {
> >                       EFI_PRINT("Secure boot is not configured\n");
> >                       return EFI_INVALID_PARAMETER;
> >               }
>