circuitpython/ports/stm32/mboot/mboot_pack_dfu.py

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# This file is part of the MicroPython project, http://micropython.org/
#
# The MIT License (MIT)
#
# Copyright (c) 2020-2021 Damien P. George
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
"""
Utility to create compressed, encrypted and signed DFU files.
"""
import argparse
import os
import re
import struct
import sys
import zlib
sys.path.append(os.path.dirname(__file__) + "/../../../tools")
import dfu
try:
import pyhy
except ImportError:
raise SystemExit(
"ERROR: pyhy not found. Please install python pyhy for encrypted mboot support: pip3 install pyhy"
)
# Currently supported version of a packed DFU file.
MBOOT_PACK_HEADER_VERSION = 1
# Must match MBOOT_PACK_HYDRO_CONTEXT in mboot/pack.h
MBOOT_PACK_HYDRO_CONTEXT = "mbootenc"
# Must match enum in mboot/pack.h.
MBOOT_PACK_CHUNK_META = 0
MBOOT_PACK_CHUNK_FULL_SIG = 1
MBOOT_PACK_CHUNK_FW_RAW = 2
MBOOT_PACK_CHUNK_FW_GZIP = 3
class Keys:
def __init__(self, filename):
self.filename = filename
def generate(self):
kp = pyhy.hydro_sign_keygen()
self.sign_sk = kp.sk
self.sign_pk = kp.pk
self.secretbox = pyhy.hydro_secretbox_keygen()
def _save_data(self, name, data, file_, hide=False):
prefix = "//" if hide else ""
data = ",".join("0x{:02x}".format(b) for b in data)
file_.write("{}const uint8_t {}[] = {{{}}};\n".format(prefix, name, data))
def _load_data(self, name, line):
line = line.split(name + "[] = ")
if len(line) != 2:
raise Exception("malformed input keys: {}".format(line))
data = line[1].strip()
return bytes(int(value, 16) for value in data[1:-2].split(","))
def save(self):
with open(self.filename, "w") as f:
self._save_data("mboot_pack_sign_secret_key", self.sign_sk, f, hide=True)
self._save_data("mboot_pack_sign_public_key", self.sign_pk, f)
self._save_data("mboot_pack_secretbox_key", self.secretbox, f)
def load(self):
with open(self.filename) as f:
for line in f:
for key, attr in (
("mboot_pack_sign_secret_key", "sign_sk"),
("mboot_pack_sign_public_key", "sign_pk"),
("mboot_pack_secretbox_key", "secretbox"),
):
if key in line:
setattr(self, attr, self._load_data(key, line))
def dfu_read(filename):
elems = []
with open(filename, "rb") as f:
hdr = f.read(11)
sig, ver, size, num_targ = struct.unpack("<5sBIB", hdr)
file_offset = 11
for i in range(num_targ):
hdr = f.read(274)
sig, alt, has_name, name, t_size, num_elem = struct.unpack("<6sBi255sII", hdr)
file_offset += 274
file_offset_t = file_offset
for j in range(num_elem):
hdr = f.read(8)
addr, e_size = struct.unpack("<II", hdr)
data = f.read(e_size)
elems.append((addr, data))
file_offset += 8 + e_size
if t_size != file_offset - file_offset_t:
raise Exception("corrupt DFU {} {}".format(t_size, file_offset - file_offset_t))
if size != file_offset:
raise Exception("corrupt DFU {} {}".format(size, file_offset))
hdr = f.read(16)
hdr = struct.unpack("<HHHH3sBI", hdr)
vid_pid = "0x{:04x}:0x{:04x}".format(hdr[2], hdr[1])
return vid_pid, elems
def compress(data):
c = zlib.compressobj(level=9, memLevel=9, wbits=-15) # wsize=15, no header
return c.compress(data) + c.flush()
def encrypt(keys, data):
return pyhy.hydro_secretbox_encrypt(data, 0, MBOOT_PACK_HYDRO_CONTEXT, keys.secretbox)
def sign(keys, data):
if not hasattr(keys, "sign_sk"):
raise Exception("packing a dfu requires a secret key")
return pyhy.hydro_sign_create(data, MBOOT_PACK_HYDRO_CONTEXT, keys.sign_sk)
def pack_chunk(keys, format_, chunk_addr, chunk_payload):
header = struct.pack(
"<BBBBII", MBOOT_PACK_HEADER_VERSION, format_, 0, 0, chunk_addr, len(chunk_payload)
)
chunk = header + chunk_payload
sig = sign(keys, chunk)
chunk = chunk + sig
return chunk
def data_chunks(data, n):
for i in range(0, len(data), n):
yield data[i : i + n]
def generate_keys(keys, args):
keys.generate()
keys.save()
def pack_dfu(keys, args):
chunk_size = int(args.chunk_size[0])
# Load previously generated keys.
keys.load()
# Read the input DFU file.
vid_pid, elems = dfu_read(args.infile[0])
# Ensure firmware sections are processed in order of destination memory address.
elems = sorted(elems, key=lambda e: e[0])
# Build list of packed chunks.
target = []
full_fw = b""
full_signature_payload = b""
for address, fw in elems:
# Update full firmware and full signature chunk.
full_fw += fw
full_signature_payload += struct.pack("<II", address, len(fw))
# Split the firmware into chunks, encrypt and sign the chunks
# then register them as individual DFU targets.
for i, chunk in enumerate(data_chunks(fw, chunk_size)):
chunk_addr = address + i * chunk_size
if args.gzip:
chunk = compress(chunk)
chunk = encrypt(keys, chunk)
chunk = pack_chunk(
keys,
MBOOT_PACK_CHUNK_FW_GZIP if args.gzip else MBOOT_PACK_CHUNK_FW_RAW,
chunk_addr,
chunk,
)
target.append({"address": chunk_addr, "data": chunk})
# Add full signature to targets, at location following the last chunk.
chunk_addr += chunk_size
sig = sign(keys, full_fw)
full_signature_payload += sig
full_signature_chunk = pack_chunk(
keys, MBOOT_PACK_CHUNK_FULL_SIG, chunk_addr, full_signature_payload
)
target.append({"address": chunk_addr, "data": full_signature_chunk})
# Build the packed DFU file of all the encrypted and signed chunks.
dfu.build(args.outfile[0], [target], vid_pid)
# Verify the packed DFU file.
verify_pack_dfu(keys, args.outfile[0])
def verify_pack_dfu(keys, filename):
"""Verify packed dfu file against keys. Gathers decrypted binary data."""
full_sig = pyhy.hydro_sign(MBOOT_PACK_HYDRO_CONTEXT)
_, elems = dfu_read(filename)
base_addr = None
binary_data = b""
for addr, data in elems:
if base_addr is None:
base_addr = addr
header = struct.unpack("<BBBBII", data[:12])
chunk = data[12 : 12 + header[5]]
sig = data[12 + header[5] :]
sig_pass = pyhy.hydro_sign_verify(
sig, data[:12] + chunk, MBOOT_PACK_HYDRO_CONTEXT, keys.sign_pk
)
assert sig_pass
if header[1] == MBOOT_PACK_CHUNK_FULL_SIG:
actual_sig = chunk[-64:]
else:
chunk = pyhy.hydro_secretbox_decrypt(
chunk, 0, MBOOT_PACK_HYDRO_CONTEXT, keys.secretbox
)
assert chunk is not None
if header[1] == MBOOT_PACK_CHUNK_FW_GZIP:
chunk = zlib.decompress(chunk, wbits=-15)
full_sig.update(chunk)
assert addr == base_addr + len(binary_data)
binary_data += chunk
full_sig_pass = full_sig.final_verify(actual_sig, keys.sign_pk)
assert full_sig_pass
return [{"address": base_addr, "data": binary_data}]
def unpack_dfu(keys, args):
# Load previously generated keys.
keys.load()
# Build a DFU file from the decrypted binary data.
data = verify_pack_dfu(keys, args.infile[0])
dfu.build(args.outfile[0], [data])
def main():
cmd_parser = argparse.ArgumentParser(description="Build signed/encrypted DFU files")
cmd_parser.add_argument("-k", "--keys", default="mboot_keys.h", help="filename for keys")
subparsers = cmd_parser.add_subparsers()
parser_gk = subparsers.add_parser("generate-keys", help="generate keys")
parser_gk.set_defaults(func=generate_keys)
parser_ed = subparsers.add_parser("pack-dfu", help="encrypt and sign a DFU file")
parser_ed.add_argument("-z", "--gzip", action="store_true", help="compress chunks")
parser_ed.add_argument("chunk_size", nargs=1, help="maximum size in bytes of each chunk")
parser_ed.add_argument("infile", nargs=1, help="input DFU file")
parser_ed.add_argument("outfile", nargs=1, help="output DFU file")
parser_ed.set_defaults(func=pack_dfu)
parser_dd = subparsers.add_parser("unpack-dfu", help="decrypt a signed/encrypted DFU file")
parser_dd.add_argument("infile", nargs=1, help="input packed DFU file")
parser_dd.add_argument("outfile", nargs=1, help="output DFU file")
parser_dd.set_defaults(func=unpack_dfu)
args = cmd_parser.parse_args()
keys = Keys(args.keys)
args.func(keys, args)
if __name__ == "__main__":
main()