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scripts: imgtool: compression
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Adds LZMA2 compression to imgtool.
Python lzma library is unable to compress with proper parameters while using
"ALONE" container, therefore 2 header bytes are calculated and added
to payload by imgtool.

Signed-off-by: Mateusz Michalek <mateusz.michalek@nordicsemi.no>
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@michalek-no @nvlsianpu
michalek-no authored and nvlsianpu committed Oct 4, 2024
1 parent 30bcd46 commit 63fa7e4
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Showing 2 changed files with 132 additions and 14 deletions.
67 changes: 60 additions & 7 deletions scripts/imgtool/image.py
View file
Original file line number Diff line number Diff line change
Expand Up @@ -20,7 +20,15 @@
Image signing and management.
"""

from . import version as versmod
from .boot_record import create_sw_component_data
import click
import copy
from enum import Enum
import array
from intelhex import IntelHex
import hashlib
import array
import os.path
import struct
from enum import Enum
Expand Down Expand Up @@ -60,6 +68,8 @@
'NON_BOOTABLE': 0x0000010,
'RAM_LOAD': 0x0000020,
'ROM_FIXED': 0x0000100,
'COMPRESSED_LZMA1': 0x0000200,
'COMPRESSED_LZMA2': 0x0000400,
}

TLV_VALUES = {
Expand All @@ -80,6 +90,9 @@
'DEPENDENCY': 0x40,
'SEC_CNT': 0x50,
'BOOT_RECORD': 0x60,
'DECOMP_SIZE': 0x70,
'DECOMP_SHA': 0x71,
'DECOMP_SIGNATURE': 0x72,
}

TLV_SIZE = 4
Expand Down Expand Up @@ -238,6 +251,9 @@ def __init__(self, version=None, header_size=IMAGE_HEADER_SIZE,
if load_addr and rom_fixed:
raise click.UsageError("Can not set rom_fixed and load_addr at the same time")

self.image_hash = None
self.image_size = None
self.signature = None
self.version = version or versmod.decode_version("0")
self.header_size = header_size
self.pad_header = pad_header
Expand All @@ -253,6 +269,7 @@ def __init__(self, version=None, header_size=IMAGE_HEADER_SIZE,
self.rom_fixed = rom_fixed
self.erased_val = 0xff if erased_val is None else int(erased_val, 0)
self.payload = []
self.infile_data = []
self.enckey = None
self.save_enctlv = save_enctlv
self.enctlv_len = 0
Expand Down Expand Up @@ -307,13 +324,31 @@ def load(self, path):
try:
if ext == INTEL_HEX_EXT:
ih = IntelHex(path)
self.payload = ih.tobinarray()
self.infile_data = ih.tobinarray()
self.payload = copy.copy(self.infile_data)
self.base_addr = ih.minaddr()
else:
with open(path, 'rb') as f:
self.payload = f.read()
self.infile_data = f.read()
self.payload = copy.copy(self.infile_data)
except FileNotFoundError:
raise click.UsageError("Input file not found")
self.image_size = len(self.payload)

# Add the image header if needed.
if self.pad_header and self.header_size > 0:
if self.base_addr:
# Adjust base_addr for new header
self.base_addr -= self.header_size
self.payload = bytes([self.erased_val] * self.header_size) + \
self.payload

self.check_header()

def load_compressed(self, data, compression_header):
"""Load an image from buffer"""
self.payload = compression_header + data
self.image_size = len(self.payload)

# Add the image header if needed.
if self.pad_header and self.header_size > 0:
Expand Down Expand Up @@ -408,7 +443,8 @@ def ecies_hkdf(self, enckey, plainkey):
return cipherkey, ciphermac, pubk

def create(self, key, public_key_format, enckey, dependencies=None,
sw_type=None, custom_tlvs=None, encrypt_keylen=128, clear=False,
sw_type=None, custom_tlvs=None, compression_tlvs=None,
compression_type=None, encrypt_keylen=128, clear=False,
fixed_sig=None, pub_key=None, vector_to_sign=None, user_sha='auto'):
self.enckey = enckey

Expand Down Expand Up @@ -471,6 +507,9 @@ def create(self, key, public_key_format, enckey, dependencies=None,
dependencies_num = len(dependencies[DEP_IMAGES_KEY])
protected_tlv_size += (dependencies_num * 16)

if compression_tlvs is not None:
for value in compression_tlvs.values():
protected_tlv_size += TLV_SIZE + len(value)
if custom_tlvs is not None:
for value in custom_tlvs.values():
protected_tlv_size += TLV_SIZE + len(value)
Expand All @@ -492,11 +531,15 @@ def create(self, key, public_key_format, enckey, dependencies=None,
else:
self.payload.extend(pad)

compression_flags = 0x0
if compression_tlvs is not None:
if compression_type == "lzma2":
compression_flags = IMAGE_F['COMPRESSED_LZMA2']
# This adds the header to the payload as well
if encrypt_keylen == 256:
self.add_header(enckey, protected_tlv_size, 256)
self.add_header(enckey, protected_tlv_size, compression_flags, 256)
else:
self.add_header(enckey, protected_tlv_size)
self.add_header(enckey, protected_tlv_size, compression_flags)

prot_tlv = TLV(self.endian, TLV_PROT_INFO_MAGIC)

Expand Down Expand Up @@ -526,6 +569,9 @@ def create(self, key, public_key_format, enckey, dependencies=None,
)
prot_tlv.add('DEPENDENCY', payload)

if compression_tlvs is not None:
for tag, value in compression_tlvs.items():
prot_tlv.add(tag, value)
if custom_tlvs is not None:
for tag, value in custom_tlvs.items():
prot_tlv.add(tag, value)
Expand All @@ -544,6 +590,7 @@ def create(self, key, public_key_format, enckey, dependencies=None,
digest = sha.digest()
message = digest;
tlv.add(hash_tlv, digest)
self.image_hash = digest

if vector_to_sign == 'payload':
# Stop amending data to the image
Expand Down Expand Up @@ -623,10 +670,16 @@ def create(self, key, public_key_format, enckey, dependencies=None,

self.check_trailer()

def get_struct_endian(self):
return STRUCT_ENDIAN_DICT[self.endian]

def get_signature(self):
return self.signature

def add_header(self, enckey, protected_tlv_size, aes_length=128):
def get_infile_data(self):
return self.infile_data

def add_header(self, enckey, protected_tlv_size, compression_flags, aes_length=128):
"""Install the image header."""

flags = 0
Expand Down Expand Up @@ -664,7 +717,7 @@ def add_header(self, enckey, protected_tlv_size, aes_length=128):
protected_tlv_size, # TLV Info header +
# Protected TLVs
len(self.payload) - self.header_size, # ImageSz
flags,
flags | compression_flags,
self.version.major,
self.version.minor or 0,
self.version.revision or 0,
Expand Down
79 changes: 72 additions & 7 deletions scripts/imgtool/main.py
View file
Original file line number Diff line number Diff line change
Expand Up @@ -22,13 +22,24 @@
import getpass
import imgtool.keys as keys
import sys
import struct
import os
import lzma
import hashlib
import base64
from imgtool import image, imgtool_version
from imgtool.version import decode_version
from imgtool.dumpinfo import dump_imginfo
from .keys import (
RSAUsageError, ECDSAUsageError, Ed25519UsageError, X25519UsageError)

comp_default_dictsize=131072
comp_default_pb=2
comp_default_lc=3
comp_default_lp=1
comp_default_preset=9


MIN_PYTHON_VERSION = (3, 6)
if sys.version_info < MIN_PYTHON_VERSION:
sys.exit("Python %s.%s or newer is required by imgtool."
Expand Down Expand Up @@ -300,6 +311,14 @@ def get_dependencies(ctx, param, value):
dependencies[image.DEP_VERSIONS_KEY] = versions
return dependencies

def create_lzma2_header(dictsize, pb, lc, lp):
header = bytearray()
for i in range(0, 40):
if dictsize <= ((2 | ((i) & 1)) << int((i) / 2 + 11)):
header.append(i)
break
header.append( ( pb * 5 + lp) * 9 + lc)
return header

class BasedIntParamType(click.ParamType):
name = 'integer'
Expand Down Expand Up @@ -343,6 +362,11 @@ def convert(self, value, param, ctx):
type=click.Choice(['128', '256']),
help='When encrypting the image using AES, select a 128 bit or '
'256 bit key len.')
@click.option('--compression', default='disabled',
type=click.Choice(['disabled', 'lzma2']),
help='Enable image compression using specified type. '
'Will fall back without image compression automatically '
'if the compression increases the image size.')
@click.option('-c', '--clear', required=False, is_flag=True, default=False,
help='Output a non-encrypted image with encryption capabilities,'
'so it can be installed in the primary slot, and encrypted '
Expand Down Expand Up @@ -414,10 +438,11 @@ def convert(self, value, param, ctx):
.hex extension, otherwise binary format is used''')
def sign(key, public_key_format, align, version, pad_sig, header_size,
pad_header, slot_size, pad, confirm, max_sectors, overwrite_only,
endian, encrypt_keylen, encrypt, infile, outfile, dependencies,
load_addr, hex_addr, erased_val, save_enctlv, security_counter,
boot_record, custom_tlv, rom_fixed, max_align, clear, fix_sig,
fix_sig_pubkey, sig_out, user_sha, vector_to_sign, non_bootable):
endian, encrypt_keylen, encrypt, compression, infile, outfile,
dependencies, load_addr, hex_addr, erased_val, save_enctlv,
security_counter, boot_record, custom_tlv, rom_fixed, max_align,
clear, fix_sig, fix_sig_pubkey, sig_out, user_sha, vector_to_sign,
non_bootable):

if confirm:
# Confirmed but non-padded images don't make much sense, because
Expand All @@ -431,6 +456,7 @@ def sign(key, public_key_format, align, version, pad_sig, header_size,
erased_val=erased_val, save_enctlv=save_enctlv,
security_counter=security_counter, max_align=max_align,
non_bootable=non_bootable)
compression_tlvs = {}
img.load(infile)
key = load_key(key) if key else None
enckey = load_key(encrypt) if encrypt else None
Expand Down Expand Up @@ -484,10 +510,49 @@ def sign(key, public_key_format, align, version, pad_sig, header_size,
}

img.create(key, public_key_format, enckey, dependencies, boot_record,
custom_tlvs, int(encrypt_keylen), clear, baked_signature,
pub_key, vector_to_sign, user_sha)
custom_tlvs, compression_tlvs, int(encrypt_keylen), clear,
baked_signature, pub_key, vector_to_sign, user_sha)

if compression == "lzma2":
compressed_img = image.Image(version=decode_version(version),
header_size=header_size, pad_header=pad_header,
pad=pad, confirm=confirm, align=int(align),
slot_size=slot_size, max_sectors=max_sectors,
overwrite_only=overwrite_only, endian=endian,
load_addr=load_addr, rom_fixed=rom_fixed,
erased_val=erased_val, save_enctlv=save_enctlv,
security_counter=security_counter, max_align=max_align)
compression_filters = [
{"id": lzma.FILTER_LZMA2, "preset": comp_default_preset,
"dict_size": comp_default_dictsize, "lp": comp_default_lp,
"lc": comp_default_lc}
]
compressed_data = lzma.compress(img.get_infile_data(),filters=compression_filters,
format=lzma.FORMAT_RAW)
uncompressed_size = len(img.get_infile_data())
compressed_size = len(compressed_data)
print(f"compressed image size: {compressed_size} bytes")
print(f"original image size: {uncompressed_size} bytes")
compression_tlvs["DECOMP_SIZE"] = struct.pack(
img.get_struct_endian() + 'L', img.image_size)
compression_tlvs["DECOMP_SHA"] = img.image_hash
compression_tlvs_size = len(compression_tlvs["DECOMP_SIZE"])
compression_tlvs_size += len(compression_tlvs["DECOMP_SHA"])
if img.get_signature():
compression_tlvs["DECOMP_SIGNATURE"] = img.get_signature()
compression_tlvs_size += len(compression_tlvs["DECOMP_SIGNATURE"])
if (compressed_size + compression_tlvs_size) < uncompressed_size:
compression_header = create_lzma2_header(
dictsize = comp_default_dictsize, pb = comp_default_pb,
lc = comp_default_lc, lp = comp_default_lp)
compressed_img.load_compressed(compressed_data, compression_header)
compressed_img.base_addr = img.base_addr
compressed_img.create(key, public_key_format, enckey,
dependencies, boot_record, custom_tlvs, compression_tlvs,
compression, int(encrypt_keylen), clear, baked_signature,
pub_key, vector_to_sign)
img = compressed_img
img.save(outfile, hex_addr)

if sig_out is not None:
new_signature = img.get_signature()
save_signature(sig_out, new_signature)
Expand Down

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