[PATCH v2 08/17] efi_loader: signature: fix a size check against revocation list

[AKASHI Takahiro <takahiro.akashi@linaro.org>]

On Fri, Jul 03, 2020 at 01:00:21PM +0200, Heinrich Schuchardt wrote:
> On 09.06.20 07:09, AKASHI Takahiro wrote:
> > Since the size check against an entry in efi_search_siglist() is
> > incorrect, this function will never find out a to-be-matched certificate
> > and its associated revocation time in the signature list.
> >
> > Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
> > ---
> >  lib/efi_loader/efi_signature.c | 5 +++--
> >  1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/lib/efi_loader/efi_signature.c b/lib/efi_loader/efi_signature.c
> > index a05c75472721..f22dc151971f 100644
> > --- a/lib/efi_loader/efi_signature.c
> > +++ b/lib/efi_loader/efi_signature.c
> > @@ -434,10 +434,11 @@ static bool efi_search_siglist(struct x509_certificate *cert,
> >  		 *	time64_t revocation_time;
> >  		 * };
> >  		 */
> > -		if ((sig_data->size == SHA256_SUM_LEN) &&
> > -		    !memcmp(sig_data->data, hash, SHA256_SUM_LEN)) {
> > +		if ((sig_data->size >= SHA256_SUM_LEN + sizeof(time64_t)) &&
> > +		    !memcmp(sig_data->data, msg, SHA256_SUM_LEN)) {
> >  			memcpy(revoc_time, sig_data->data + SHA256_SUM_LEN,
> >  			       sizeof(*revoc_time));
> > +			EFI_PRINT("revocation time: %llu\n", *revoc_time);
> 
> *revoc_time is of type __s64. So this must be %lld. Cf.
> 
> include/linux/time.h:156

I know that because I added the definition.
Interestingly, linux added another type, timeu64_t, later on
to avoid an overflow in some calculation.

While I don't think the current format is harmful, I will change it.

-Takahiro Akashi


> Best regards
> 
> Heinrich
> 
> >  			found = true;
> >  			goto out;
> >  		}
> >
>