[PATCH v6 5/8] efi_loader: check lowest supported version

[Masahisa Kojima]

The FMP Payload Header which EDK II capsule generation scripts
insert has a firmware version.
This commit reads the lowest supported version stored in the
device tree, then check if the firmware version in FMP payload header
of the ongoing capsule is equal or greater than the
lowest supported version. If the firmware version is lower than
lowest supported version, capsule update will not be performed.

Signed-off-by: Masahisa Kojima <masahisa.kojima at linaro.org>
---
Changes in v6:
- get aligned to the latest implementation

Changes in v5:
- newly implement the device tree based versioning

Changes in v4:
- use log_err() instead of printf()

Changes in v2:
- add error message when the firmware version is lower than
  lowest supported version

 lib/efi_loader/efi_firmware.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/lib/efi_loader/efi_firmware.c b/lib/efi_loader/efi_firmware.c
index 00cf9a088a..7cd0016765 100644
--- a/lib/efi_loader/efi_firmware.c
+++ b/lib/efi_loader/efi_firmware.c
@@ -424,7 +424,8 @@ static void efi_firmware_get_fw_version(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
  */
@@ -434,11 +435,27 @@ efi_status_t efi_firmware_verify_image(const void **p_image,
 				       u8 image_index,
 				       struct fmp_state *state)
 {
+	u32 lsv;
 	efi_status_t ret;
+	efi_guid_t *image_type_id;
 
 	ret = efi_firmware_capsule_authenticate(p_image, p_image_size);
 	efi_firmware_get_fw_version(p_image, p_image_size, state);
 
+	/* check lowest_supported_version if capsule authentication passes */
+	if (ret == EFI_SUCCESS) {
+		image_type_id = efi_firmware_get_image_type_id(image_index);
+		if (!image_type_id)
+			return EFI_INVALID_PARAMETER;
+
+		efi_firmware_get_lsv_from_dtb(image_index, image_type_id, &lsv);
+		if (state->fw_version < lsv) {
+			log_err("Firmware version %u too low. Expecting >= %u. Aborting update\n",
+				state->fw_version, lsv);
+			return EFI_INVALID_PARAMETER;
+		}
+	}
+
 	return ret;
 }
 
-- 
2.17.1