[PATCH v3 3/4] efi_loader: check lowest supported version in capsule update

[Masahisa Kojima]

On Tue, 21 Mar 2023 at 15:42, Heinrich Schuchardt <xypron.glpk at gmx.de> wrote:
>
> On 3/20/23 06:54, Masahisa Kojima wrote:
> > The FMP Payload Header which EDK2 capsule generation scripts
> > insert contains lowest supported version.
> > This commit reads the lowest supported version stored in the
> > "FmpStateXXXX" EFI non-volatile variable, then check if the
> > firmware version of ongoing capsule is equal or greater than
> > the lowest supported version.
> >
> > Signed-off-by: Masahisa Kojima <masahisa.kojima at linaro.org>
> > ---
> > No changes since v2
> >
> > Changes in v2:
> > - add error message when the firmware version is lower than
> >    lowest supported version
> >
> >   lib/efi_loader/efi_firmware.c | 50 ++++++++++++++++++++++++++++++++++-
> >   1 file changed, 49 insertions(+), 1 deletion(-)
> >
> > diff --git a/lib/efi_loader/efi_firmware.c b/lib/efi_loader/efi_firmware.c
> > index 289456ecbb..8d6e32006d 100644
> > --- a/lib/efi_loader/efi_firmware.c
> > +++ b/lib/efi_loader/efi_firmware.c
> > @@ -391,6 +391,39 @@ void efi_firmware_parse_payload_header(const void **p_image,
> >       *p_image_size = image_size;
> >   }
> >
> > +/**
> > + * efi_firmware_get_lowest_supported_version - get the lowest supported version
> > + * @image_index:     image_index
> > + *
> > + * Get the lowest supported version from FmpStateXXXX variable.
> > + *
> > + * Return:           lowest supported version, return 0 if reading FmpStateXXXX
> > + *                   variable failed
> > + */
> > +static
> > +u32 efi_firmware_get_lowest_supported_version(u8 image_index)
> > +{
> > +     u16 varname[13]; /* u"FmpStateXXXX" */
> > +     efi_status_t ret;
> > +     efi_uintn_t size;
> > +     efi_guid_t *image_type_id;
> > +     struct fmp_state var_state = { 0 };
> > +
> > +     image_type_id = efi_firmware_get_image_type_id(image_index);
> > +     if (!image_type_id)
> > +             return 0;
> > +
> > +     efi_create_indexed_name(varname, sizeof(varname), "FmpState",
> > +                             image_index);
> > +     size = sizeof(var_state);
> > +     ret = efi_get_variable_int(varname, image_type_id, NULL, &size,
> > +                                &var_state, NULL);
> > +     if (ret != EFI_SUCCESS)
> > +             return 0;
> > +
> > +     return var_state.lowest_supported_version;
> > +}
> > +
> >   /**
> >    * efi_firmware_verify_image - verify image
> >    * @p_image:                Pointer to new image
> > @@ -398,7 +431,8 @@ void efi_firmware_parse_payload_header(const void **p_image,
> >    * @image_index             Image index
> >    * @state           Pointer to fmp state
> >    *
> > - * Verify the capsule file
> > + * Verify the capsule authentication and check if the fw_version
> > + * is equal or greater than the lowest supported version.
> >    *
> >    * Return:          status code
> >    */
> > @@ -409,10 +443,24 @@ efi_status_t efi_firmware_verify_image(const void **p_image,
> >                                      struct fmp_state *state)
> >   {
> >       efi_status_t ret;
> > +     u32 lowest_supported_version;
> >
> >       ret = efi_firmware_capsule_authenticate(p_image, p_image_size, state);
> >       efi_firmware_parse_payload_header(p_image, p_image_size, state);
> >
> > +     /* check lowest_supported_version if capsule authentication passes */
> > +     if (ret == EFI_SUCCESS) {
> > +             lowest_supported_version =
> > +                     efi_firmware_get_lowest_supported_version(image_index);
> > +             if (lowest_supported_version > state->fw_version) {
> > +                     printf("fw_version(%u) is too low(expected >%u). Aborting update\n",
> > +                            state->fw_version, lowest_supported_version);
>
> Please, use log_warning() or log_err() instead of printf().
>
> The addressee is a user not a developer:
>
> "Firmware version %u too low. Expecting >= %u"

OK.

>
> We should have one central place where upon exit we write a message
> indicating that either the capsule update was successful or failed.
>
> "Firmware updated to version %u" : "Firmware update failed"

Yes, I will add the log output for the user.

Thanks,
Masahisa Kojima

>
> Best regards
>
> Heinrich
>
> > +                     state->last_attempt_status =
> > +                             LAST_ATTEMPT_STATUS_ERROR_INCORRECT_VERSION;
> > +                     ret = EFI_INVALID_PARAMETER;
> > +             }
> > +     }
> > +
> >       return ret;
> >   }
> >
>