283 lines
9.6 KiB
Python
283 lines
9.6 KiB
Python
# Copyright 2017 Linaro Limited
|
|
# Copyright (c) 2018-2019, Arm Limited.
|
|
#
|
|
# Licensed under the Apache License, Version 2.0 (the "License");
|
|
# you may not use this file except in compliance with the License.
|
|
# You may obtain a copy of the License at
|
|
#
|
|
# http://www.apache.org/licenses/LICENSE-2.0
|
|
#
|
|
# Unless required by applicable law or agreed to in writing, software
|
|
# distributed under the License is distributed on an "AS IS" BASIS,
|
|
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
# See the License for the specific language governing permissions and
|
|
# limitations under the License.
|
|
|
|
"""
|
|
Image signing and management.
|
|
"""
|
|
|
|
from . import version as versmod
|
|
import hashlib
|
|
from . import boot_record as br
|
|
import struct
|
|
|
|
MANIFEST_VERSION = 0
|
|
IMAGE_MAGIC = 0x96f3b83d
|
|
IMAGE_HEADER_SIZE = 32
|
|
TLV_HEADER_SIZE = 4
|
|
PAYLOAD_DIGEST_SIZE = 32 # SHA256 hash
|
|
KEYHASH_SIZE = 32
|
|
|
|
IMG_HASH_SHA256 = 1
|
|
IMG_SIG_ED25519 = 1
|
|
|
|
# Image Type.
|
|
IMG_TYPE_VALUES = {
|
|
'MBL' : 0x1,
|
|
'PROT': 0x2,
|
|
'AROT': 0x4,
|
|
'NSPE': 0x8,}
|
|
|
|
# Image header flags.
|
|
TLV_VALUES = {
|
|
'SHA256' : 0x10,
|
|
'KEYHASH': 0x20,
|
|
'ED25519': 0x30,
|
|
'BOOT_RECORD': 0x40,}
|
|
TLV_INFO_SIZE = 4
|
|
TLV_INFO_MAGIC = 0x6907
|
|
|
|
# Sizes of the image trailer, depending on flash write size.
|
|
# trailer_sizes = {
|
|
# write_size: 128 * 3 * write_size + 8 * 2 + 16
|
|
# for write_size in [1, 2, 4, 8]
|
|
# }
|
|
|
|
tail_magic = bytearray([
|
|
0x77, 0xc2, 0x95, 0xf3,
|
|
0x60, 0xd2, 0xef, 0x7f,
|
|
0x35, 0x52, 0x50, 0x0f,
|
|
0x2c, 0xb6, 0x79, 0x80, ])
|
|
|
|
class TLV():
|
|
def __init__(self):
|
|
self.buf = bytearray()
|
|
|
|
def add(self, kind, payload):
|
|
"""Add a TLV record. Kind should be a string found in TLV_VALUES above."""
|
|
buf = struct.pack('<BBH', TLV_VALUES[kind], 0, len(payload))
|
|
self.buf += buf
|
|
self.buf += payload
|
|
|
|
def get(self):
|
|
header = struct.pack('<HH', TLV_INFO_MAGIC, TLV_INFO_SIZE + len(self.buf))
|
|
return header + bytes(self.buf)
|
|
|
|
class Image():
|
|
@classmethod
|
|
def load(cls, path, included_header=False, **kwargs):
|
|
"""Load an image from a given file"""
|
|
with open(path, 'rb') as f:
|
|
payload = f.read()
|
|
obj = cls(**kwargs)
|
|
obj.payload = payload
|
|
|
|
# Add the image header if needed.
|
|
if not included_header and obj.header_size > 0:
|
|
obj.payload = (b'\000' * obj.header_size) + obj.payload
|
|
|
|
obj.check()
|
|
return obj
|
|
|
|
def __init__(self, type, version, header_size=IMAGE_HEADER_SIZE,
|
|
pad=0):
|
|
self.type = type
|
|
self.version = version
|
|
self.header_size = header_size or IMAGE_HEADER_SIZE
|
|
self.pad = pad
|
|
|
|
def __repr__(self):
|
|
return "<Image type={}, version={}, header_size={}, \
|
|
pad={}, payloadlen=0x{:x}>".format(
|
|
self.type,
|
|
self.version,
|
|
self.header_size,
|
|
self.pad,
|
|
len(self.payload))
|
|
|
|
def save(self, path):
|
|
with open(path, 'wb') as f:
|
|
f.write(self.payload)
|
|
|
|
def check(self):
|
|
"""Perform some sanity checking of the image."""
|
|
# If there is a header requested, make sure that the image
|
|
# starts with all zeros.
|
|
if self.header_size > 0:
|
|
if any(v != 0 and v != b'\000' for v in self.payload[0:self.header_size]):
|
|
raise Exception("Padding requested, but image does not start with zeros")
|
|
|
|
def sign(self, key, cert_file):
|
|
#image_version = (str(self.version.major) + '.'
|
|
# + str(self.version.minor) + '.'
|
|
# + str(self.version.revision))
|
|
image_version = (str((self.version >> 24) & 0xff) + '.'
|
|
+ str((self.version >> 16) & 0xff) + '.'
|
|
+ str(self.version & 0xffff))
|
|
|
|
tlv = TLV()
|
|
|
|
# Full TLV size needs to be calculated in advance, because the
|
|
# header will be protected as well
|
|
tlv_size = (TLV_INFO_SIZE + len(tlv.buf) + TLV_HEADER_SIZE
|
|
+ PAYLOAD_DIGEST_SIZE)
|
|
if key is not None:
|
|
tlv_size += (TLV_HEADER_SIZE + KEYHASH_SIZE
|
|
+ TLV_HEADER_SIZE + key.sig_len())
|
|
pub = key.get_public_bytes()
|
|
sha = hashlib.sha256()
|
|
sha.update(pub)
|
|
pubbytes = sha.digest()
|
|
else:
|
|
pubbytes = bytes(KEYHASH_SIZE)
|
|
|
|
# The image hash is computed over the image header, the image itself
|
|
# and the protected TLV area. However, the boot record TLV (which is
|
|
# part of the protected area) should contain this hash before it is
|
|
# even calculated. For this reason the script fills this field with
|
|
# zeros and the bootloader will insert the right value later.
|
|
image_hash = bytes(PAYLOAD_DIGEST_SIZE)
|
|
|
|
# Create CBOR encoded boot record
|
|
boot_record = br.create_sw_component_data(self.type, image_version,
|
|
"SHA256", image_hash,
|
|
pubbytes)
|
|
|
|
tlv_size += TLV_HEADER_SIZE + len(boot_record)
|
|
|
|
if cert_file is not None:
|
|
with open(cert_file, 'rb') as f:
|
|
cert = f.read()
|
|
cert_size = len(cert)
|
|
else:
|
|
cert_size = 0
|
|
|
|
self.add_header(key, tlv_size, cert_size)
|
|
|
|
hashsrc = self.payload[(self.header_size - IMAGE_HEADER_SIZE):len(self.payload)]
|
|
sha = hashlib.sha256()
|
|
sha.update(hashsrc)
|
|
digest = sha.digest()
|
|
tlv.add('SHA256', digest)
|
|
|
|
tlv_header = struct.pack('HH', TLV_INFO_MAGIC, tlv_size)
|
|
self.payload += tlv_header
|
|
|
|
if key is not None:
|
|
tlv.add('KEYHASH', pubbytes)
|
|
|
|
# `sign` expects the full image payload (sha256 done internally),
|
|
# while `sign_digest` expects only the digest of the payload
|
|
|
|
if hasattr(key, 'sign'):
|
|
sig = key.sign(bytes(self.payload))
|
|
else:
|
|
sig = key.sign_digest(digest)
|
|
tlv.add(key.sig_tlv(), sig)
|
|
|
|
tlv.add('BOOT_RECORD', boot_record)
|
|
|
|
self.payload += tlv.get()[TLV_INFO_SIZE:]
|
|
|
|
if cert_file is not None:
|
|
self.payload += cert
|
|
|
|
def add_header(self, key, tlv_size, cert_size):
|
|
"""Install the image header.
|
|
|
|
The key is needed to know the type of signature, and
|
|
approximate the size of the signature.
|
|
Now use ED25519 as default. """
|
|
|
|
pbytes = b'\xff' * (self.header_size - IMAGE_HEADER_SIZE)
|
|
|
|
fmt = ('<' +
|
|
# type ImageHdr struct {
|
|
'I' + # Magic uint32
|
|
'I' + # TotalSz uint32
|
|
'B' + # ManiVer uint8
|
|
'B' + # ImgType uint8
|
|
'B' + # HashAlg uint8
|
|
'B' + # SignAlg uint8
|
|
'H' + # HdrSz uint16
|
|
'H' + # PTLVSz uint16
|
|
'I' + # ImgSz uint32
|
|
'B' + # Major version uint8
|
|
'B' + # Minor version uint8
|
|
'H' + # Revision uint16
|
|
'I' # Rsvd uint32
|
|
# Checksum uint32
|
|
) # }
|
|
#assert struct.calcsize(fmt) == IMAGE_HEADER_SIZE
|
|
img_size = len(self.payload) - self.header_size
|
|
tot_size = IMAGE_HEADER_SIZE + img_size + tlv_size + cert_size
|
|
#print("img_size : ", img_size)
|
|
#print("tlv_size : ", tlv_size)
|
|
#print("cert_size : ", cert_size)
|
|
#print("tot_size : ", tot_size, " hex: ", hex(tot_size))
|
|
major = (self.version >> 24)
|
|
minor = ((self.version & 0xFFFFFF) >> 16)
|
|
revision = (self.version & 0xFFFF)
|
|
#print("major: ", major, " minor: ", minor, " rev: ", revision)
|
|
#print("image type : ", IMG_TYPE_VALUES[self.type])
|
|
header = struct.pack(fmt,
|
|
IMAGE_MAGIC,
|
|
tot_size,
|
|
MANIFEST_VERSION,
|
|
IMG_TYPE_VALUES[self.type],
|
|
IMG_HASH_SHA256,
|
|
IMG_SIG_ED25519,
|
|
IMAGE_HEADER_SIZE,
|
|
tlv_size,
|
|
img_size,
|
|
major,
|
|
minor,
|
|
revision,
|
|
0) # Rsvd
|
|
|
|
n = 0
|
|
chksum = 0
|
|
while n < len(header):
|
|
num = header[n]
|
|
num += (header[n + 1]) << 8
|
|
num += (header[n + 2]) << 16
|
|
num += (header[n + 3]) << 24
|
|
#print("num: ", num, " hex: ", hex(num))
|
|
chksum ^= num
|
|
n += 4
|
|
#print("chksum hex: ", hex(chksum))
|
|
chksum &= 0xFFFFFFFF
|
|
header += struct.pack('<I', chksum)
|
|
|
|
#print("header : ", header)
|
|
header_with_pad = pbytes + header
|
|
|
|
self.payload = bytearray(self.payload)
|
|
self.payload[:len(header_with_pad)] = header_with_pad
|
|
|
|
def pad_to(self, size, align):
|
|
"""Pad the image to the given size, with the given flash alignment."""
|
|
if align not in [1, 2, 4, 8]:
|
|
raise Exception("Align must be one of 1, 2, 4 or 8.")
|
|
remain = size % align
|
|
if remain != 0:
|
|
size += align - remain
|
|
padding = size - len(self.payload)
|
|
if padding < 0:
|
|
msg = "Image size (0x{:x}) exceeds requested size 0x{:x}".format(
|
|
len(self.payload), size)
|
|
raise Exception(msg)
|
|
pbytes = b'\xff' * padding
|
|
self.payload += pbytes
|