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

[Heinrich Schuchardt]

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"

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"

Best regards

Heinrich

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