mirror of https://github.com/ArduPilot/ardupilot
92 lines
2.1 KiB
Python
92 lines
2.1 KiB
Python
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#!/usr/bin/env python3
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'''
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sign an ArduPilot APJ firmware with a private key
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'''
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import sys
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import struct
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import json, base64, zlib
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try:
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import monocypher
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except ImportError:
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print("Please install monocypher with: python3 -m pip install pymonocypher")
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sys.exit(1)
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key_len = 32
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sig_len = 64
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sig_version = 30437
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descriptor = b'\x41\xa3\xe5\xf2\x65\x69\x92\x07'
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if len(sys.argv) < 3:
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print("Usage: make_secure_fw.py APJ_FILE PRIVATE_KEYFILE")
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sys.exit(1)
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def to_unsigned(i):
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'''convert a possibly signed integer to unsigned'''
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if i < 0:
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i += 2**32
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return i
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apj_file = sys.argv[1]
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key_file = sys.argv[2]
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# open apj file
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apj = open(apj_file, 'r').read()
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# decode json in apj
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d = json.loads(apj)
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# get image data
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img = zlib.decompress(base64.b64decode(d['image']))
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img_len = len(img)
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def decode_key(ktype, key):
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ktype += "_KEYV1:"
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if not key.startswith(ktype):
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print("Invalid key type")
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sys.exit(1)
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return base64.b64decode(key[len(ktype):])
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key = decode_key("PRIVATE", open(key_file, 'r').read())
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if len(key) != key_len:
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print("Bad key length %u" % len(key))
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sys.exit(1)
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offset = img.find(descriptor)
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if offset == -1:
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print("No APP_DESCRIPTOR found")
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sys.exit(1)
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offset += 8
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desc_len = 92
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flash1 = img[:offset]
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flash2 = img[offset+desc_len:]
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flash12 = flash1 + flash2
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signature = monocypher.signature_sign(key, flash12)
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if len(signature) != sig_len:
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print("Bad signature length %u should be %u" % (len(signature), sig_len))
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sys.exit(1)
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# pack signature in 4 bytes length, 8 byte signature version and 64 byte
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# signature. We have a signature version to allow for changes to signature
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# system in the future
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desc = struct.pack("<IQ64s", sig_len+8, sig_version, signature)
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img = img[:(offset + 16)] + desc + img[(offset + desc_len):]
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if len(img) != img_len:
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print("Error: Image length changed")
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sys.exit(1)
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print("Applying signature")
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d["image"] = base64.b64encode(zlib.compress(img,9)).decode('utf-8')
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d["signed_firmware"] = True
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f = open(sys.argv[1], "w")
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f.write(json.dumps(d, indent=4))
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f.close()
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print("Wrote %s" % apj_file)
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