Re: [PATCH] efi_loader: capsule: add a debug message in case of no key

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

On Tue, Jul 20, 2021 at 09:39:12AM +0300, Ilias Apalodimas wrote:
> Akashi-san,
> 
> On Tue, Jul 20, 2021 at 11:13:40AM +0900, AKASHI Takahiro wrote:
> > On Thu, May 20, 2021 at 04:06:12AM +0200, Heinrich Schuchardt wrote:
> > > On 5/10/21 10:19 AM, AKASHI Takahiro wrote:
> > > > It will probably be a common error case that a certificate (public key)
> > > > is not provided by the system while capsule authentication is enabled.
> > > > So add a debug message.
> > > > 
> > > > Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
> > > > ---
> > > >   lib/efi_loader/efi_capsule.c | 4 +++-
> > > >   1 file changed, 3 insertions(+), 1 deletion(-)
> > > > 
> > > > diff --git a/lib/efi_loader/efi_capsule.c b/lib/efi_loader/efi_capsule.c
> > > > index 90893f85e22c..84ddaf50d13f 100644
> > > > --- a/lib/efi_loader/efi_capsule.c
> > > > +++ b/lib/efi_loader/efi_capsule.c
> > > > @@ -316,8 +316,10 @@ efi_status_t efi_capsule_authenticate(const void *capsule, efi_uintn_t capsule_s
> > > >   	}
> > > > 
> > > >   	ret = efi_get_public_key_data(&fdt_pkey, &pkey_len);
> > > > -	if (ret < 0)
> > > > +	if (ret < 0) {
> > > > +		debug("Public key/certificate not found\n");
> > > 
> > > Currently the only implementation of efi_get_public_key_data() actually
> > > providing keys is the one in board/emulation/common/qemu_capsule.c where
> > > the user has to manually upload the esl file.
> > > 
> > > For future implementation it is preferable to build the public key data
> > > into the U-Boot binary. If it is part of the build process then the only
> > > error that could come up is that the public key data has the wrong format.
> > 
> > Now Ilias posted a patch to embed a public key in the U-Boot binary.
> > But it won't be the only solution in the future and the system owners
> > may want to provide a key in their own way; hence, it might not be "part
> > of build process."
> > 
> 
> Correct.  My patch intentionally leaves out that part and I hope someone
> will need it and implement it.
> 
> > So I think that adding a message is still valid, even it should be
> > treated as an error message instead of a debug message to warn "users".
> 
> 
> Keep in mind that the makefile currently checks for the .esl file.  if the
> file is not found there's a compilation error, prompting the user to add a
> valid file

If your efi_get_public_key_data() is the only implementation in
the system, checking a return value (if ret < 0) is also meaningless.

-Takahiro Akashi


> 
> Thanks
> /Ilias
> > 
> > -Takahiro Akashi
> > 
> > 
> > > If we are using the weak implementation of efi_get_public_key_data() in
> > > lib/efi_loader/efi_capsule.cwith CONFIG_EFI_CAPSULE_AUTHENTICATE=y, the
> > > system is misconfigured. Do we need that weak implementation at all? I
> > > would prefer to remove to get a build error.
> > > 
> > > I suggest that you add a log_err() message with above text into the
> > > board/emulation/common/qemu_capsule.c implementation of
> > > efi_get_public_key_data(). This way the user will see that he forgot a step.
> > > 
> > > Best regards
> > > 
> > > Heinrich
> > > 
> > > >   		goto out;
> > > > +	}
> > > > 
> > > >   	pkey = malloc(pkey_len);
> > > >   	if (!pkey)
> > > > 
> > >