65 lines
1.9 KiB
Python
65 lines
1.9 KiB
Python
#!/usr/bin/env python3
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# -*- coding: utf-8 -*-
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# Many thanks to Alex W. who figured this out!
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"""
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Calculates the SHA1 of a fw_all.bin until the ending marker.
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"""
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from hashlib import sha1
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from struct import unpack
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from grmn import devices
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import sys
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FILE = sys.argv[1]
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BLOCKSIZE = 4096
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END_MARKER = b"\xff\xff\x5a\xa5\xff\xff\xff\xff"
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first_block = True
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past_end = False
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trailer = bytes()
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trailer_pos = -1
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csum = sha1()
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print("Reading {} ...".format(FILE))
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with open(FILE, "rb") as f:
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while True:
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block = f.read(BLOCKSIZE)
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if first_block:
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start = block.find(b"\xff\xff\xff\xff\xf0\xb9\x9d\x38\x0f\x46\x62\xc7")
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if start < 0:
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print("No Fenix firmware header found.")
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else:
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start += 4
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hwid = unpack("<H", block[start+24:start+24+2])[0]
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fver = unpack("<H", block[start+28:start+28+2])[0]
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print("- Hardware ID: 0x{:04x} / {:d} ({})".format(hwid, hwid, devices.get_name(hwid, 0, "Unknown device")))
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print("- Firmware Version: 0x{:04x} / {:04d}".format(fver, fver))
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first_block = False
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if END_MARKER in block:
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end_pos = block.find(END_MARKER)
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marker_end = end_pos + len(END_MARKER)
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past_end = True
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csum.update(block[0:marker_end])
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block = block[marker_end:]
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trailer_pos = f.tell() - len(block)
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if past_end:
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trailer += block
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else:
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csum.update(block)
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if len(block) < BLOCKSIZE:
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break
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f.close()
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expected_sha1 = csum.hexdigest()
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found_sha1 = trailer[:20].hex()
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print("Calculated SHA1: {}".format(expected_sha1))
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print("SHA1 in file : {} (offset 0x{:x})".format(found_sha1, trailer_pos))
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if expected_sha1 == found_sha1:
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print("☑ CHECKSUM VALID.")
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else:
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print("☒ CHECKSUM INVALID!!! (Or GCD or other type.)")
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