[PATCH v3 3/4] efi_loader: simplify efi_sigstore_parse_sigdb()

[Ilias Apalodimas]

On Wed, 6 Oct 2021 at 16:15, Heinrich Schuchardt
<heinrich.schuchardt at canonical.com> wrote:
>
> On 10/6/21 10:02, Ilias Apalodimas wrote:
> > On Wed, 6 Oct 2021 at 10:21, Heinrich Schuchardt
> > <heinrich.schuchardt at canonical.com> wrote:
> >>
> >>
> >>
> >> On 10/6/21 08:29, Ilias Apalodimas wrote:
> >>> On Sun, Oct 03, 2021 at 11:23:19AM +0200, Heinrich Schuchardt wrote:
> >>>> Simplify efi_sigstore_parse_sigdb() by using existing functions.
> >>>>
> >>>> Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt at canonical.com>
> >>>> ---
> >>>> v3:
> >>>>       Keep error handling in efi_sigstore_parse_sigdb()
> >>>> v2:
> >>>>       remove a superfluous check
> >>>> ---
> >>>>    lib/efi_loader/efi_signature.c | 11 ++---------
> >>>>    1 file changed, 2 insertions(+), 9 deletions(-)
> >>>>
> >>>> diff --git a/lib/efi_loader/efi_signature.c b/lib/efi_loader/efi_signature.c
> >>>> index bdd09881fc..97f6dfacd9 100644
> >>>> --- a/lib/efi_loader/efi_signature.c
> >>>> +++ b/lib/efi_loader/efi_signature.c
> >>>> @@ -746,18 +746,11 @@ struct efi_signature_store *efi_sigstore_parse_sigdb(u16 *name)
> >>>>       efi_uintn_t db_size;
> >>>>       efi_status_t ret;
> >>>>
> >>>> -    if (!u16_strcmp(name, L"PK") || !u16_strcmp(name, L"KEK")) {
> >>>> -            vendor = &efi_global_variable_guid;
> >>>> -    } else if (!u16_strcmp(name, L"db") || !u16_strcmp(name, L"dbx")) {
> >>>> -            vendor = &efi_guid_image_security_database;
> >>>> -    } else {
> >>>> -            EFI_PRINT("unknown signature database, %ls\n", name);
> >>>> -            return NULL;
> >>>> -    }
> >>>> +    vendor = efi_auth_var_get_guid(name);
> >>>
> >>> Should we return NULL if we get back the default guid?
> >>
> >> efi_sigstore_parse_sigdb() is only called with fixed values of 'name'.
> >> So how should this occur?
> >
> > Bugs that slip through maybe?  I generally prefer being more pedantic
> > with security related code
>
> PK and KEK use efi_global_variable_guid and will be used as argument for
> efi_sigstore_parse_sigdb(). Your proposed check would break the code.

Yea that's the reason I was asking about efi_auth_var_get_guid().  I
would prefer if that returned NULL if the variable is not found
instead of the default GUID

Regards
/Ilias
>
> Best regards
>
> Heinrich
>
> >
> > Regards
> > /Ilias
> >>
> >> Best regards
> >>
> >> Heinrich
> >>
> >>>
> >>>>
> >>>>       /* retrieve variable data */
> >>>>       db_size = 0;
> >>>> -    ret = EFI_CALL(efi_get_variable(name, vendor, NULL, &db_size, NULL));
> >>>> +    ret = efi_get_variable_int(name, vendor, NULL, &db_size, NULL);
> >>>>       if (ret == EFI_NOT_FOUND) {
> >>>>               EFI_PRINT("variable, %ls, not found\n", name);
> >>>>               sigstore = calloc(sizeof(*sigstore), 1);
> >>>> --
> >>>> 2.32.0
> >>>>
> >>>
> >>> Regards
> >>> /Ilias
> >>>
>