trezor-firmware/tools/check_bootloader

#!/usr/bin/env python3
import sys
import struct

# bootloader header specification: https://github.com/trezor/trezor-core/blob/master/docs/bootloader.md#bootloader-header

def check_bootloader(filename):
    data = open(filename, 'rb').read()
    hdr = struct.unpack('<4sIIIBBBBB64s171s', data[:256])
    code = data[256:]
    magic, hdrlen, expiry, codelen, vmajor, vminor, vpatch, vbuild, sigidx, sig, reserved = hdr
    sigidx = tuple([ i + 1 for i in range(8) if sigidx & (1 << i) ])
    print('magic    :', magic)
    assert magic == b'TRZB'
    print('hdrlen   :', hdrlen)
    assert hdrlen == 256
    print('expiry   :', expiry)
    print('codelen  :', codelen)
    print('vmajor   :', vmajor)
    print('vminor   :', vminor)
    print('vpatch   :', vpatch)
    print('vbuild   :', vbuild)
    print('sigidx   :', sigidx)
    print('sig      :', sig)
    assert reserved == 171 * b'\x00'
    assert codelen == 64*1024
    assert codelen == len(code)


def main():
    if len(sys.argv) < 2:
        print('Usage: check_bootloader bootloader.bin')
        return 1
    fn = sys.argv[1]
    check_bootloader(fn)


main()