def calculate_new_obb_digest(ifwi_file, fv_list, digest_file):
"""Calculate new OBB hash for one or more firmware volumes.
The assumption is all FVs are continuous in one region."""
bios = bytearray()
ifwi = IFWI_IMAGE(ifwi_file)
if not ifwi.is_ifwi_image():
logger.warn("Invalid IFWI descriptor signature. Assuming BIOS image")
with open(ifwi_file, "rb") as fd:
bios = FirmwareDevice(0, bytearray(fd.read()))
else:
ifwi.parse()
bios_start = ifwi.region_list[1][1]
bios_limit = ifwi.region_list[1][2]
bios = FirmwareDevice(0, ifwi.data[bios_start:bios_limit + 1])
logger.info("Found BIOS ({}MB)...".format(
len(bios.FdData) // (1024 * 1024)))
bios.ParseFd()
# Locate FVs (note: only the first FV index is used)
fv_id_list = []
for fv in fv_list:
obb_fv_idx = bios.get_fv_index_by_guid(fv.bytes_le)
if not (0 < obb_fv_idx < len(bios.FvList)):
raise ValueError("FV {} for OBB region is not found".format(fv))
logger.info("Found FV @ index {}".format(obb_fv_idx))
fv_id_list.append(obb_fv_idx)
starting_fv_idx = fv_id_list[0]
logger.info("*** OBB region starts from FV{} (len:{})".format(
starting_fv_idx, len(fv_id_list)))
obb_offset = bios.FvList[starting_fv_idx].Offset
obb_length = 0
if bios.is_fsp_wrapper():
logger.info("FSP Wrapper BIOS")
obb_fv_end = starting_fv_idx + len(fv_list)
else:
logger.critical("EDK2 BIOS image format is not supported any more")
exit(2)
# Get total length of OBB
logger.info("start FV: {} end FV: {}".format(starting_fv_idx, obb_fv_end))
for fv in bios.FvList[starting_fv_idx:obb_fv_end]:
logger.info("Adding FV size 0x{:x} ...".format(len(fv.FvData)))
obb_length += len(fv.FvData)
logger.debug("OBB offset: {:x} len {:x}".format(obb_offset, obb_length))
# Hash it
digest = hashes.Hash(hashes.SHA256(), backend=default_backend())
digest.update(bios.FdData[obb_offset:obb_offset + obb_length])
result = digest.finalize()
with open(digest_file, "wb") as hash_fd:
hash_fd.write(result)
return
def update_obb_digest(ifwi_file, digest_file):
"""Calculate OBB hash according to a predefined range"""
ifwi = IFWI_IMAGE(ifwi_file)
if not ifwi.is_ifwi_image():
logger.critical("Bad IFWI image")
exit(1)
ifwi.parse()
bios_start = ifwi.region_list[1][1]
bios_limit = ifwi.region_list[1][2]
logger.info("Parsing BIOS ...")
bios = FirmwareDevice(0, ifwi.data[bios_start:bios_limit + 1])
bios.ParseFd()
# Extract FVs belongs to OBB
obb_fv_idx = bios.get_fv_index_by_guid(GUID_FVOSBOOT.bytes_le)
if not (0 < obb_fv_idx < len(bios.FvList)):
raise ValueError("Starting OBB FV is not found")
logger.debug("OBB region starts from FV{}".format(obb_fv_idx))
obb_offset = bios.FvList[obb_fv_idx].Offset
obb_length = 0
if bios.is_fsp_wrapper():
# FVOSBOOT + FVUEFIBOOT_PRIME + FVADVANCED + FVPOSTMEMORY + FSPS
logger.info("FSP Wrapper BIOS")
obb_fv_end = obb_fv_idx + 5
else:
# FVOSBOOT + FVUEFIBOOT_PRIME + FVADVANCED + FVPOSTMEMORY
logger.info("EDK2 BIOS")
obb_fv_end = obb_fv_idx + 4
for fv in bios.FvList[obb_fv_idx:obb_fv_end]:
obb_length += len(fv.FvData)
logger.debug("OBB offset: {:x} len {:x}".format(obb_offset, obb_length))
# Hash it
digest = hashes.Hash(hashes.SHA256(), backend=default_backend())
digest.update(bios.FdData[obb_offset:obb_offset + obb_length])
result = digest.finalize()
with open(digest_file, "wb") as hash_fd:
hash_fd.write(result)
return