buildroot/share/PlatformIO/scripts/chitu_crypt.py

   1 #
   2 # chitu_crypt.py
   3 # Customizations for Chitu boards
   4 #
   5 import pioutil
   6 if pioutil.is_pio_build():
   7     import os,random,struct,uuid,marlin
   8     # Relocate firmware from 0x08000000 to 0x08008800
   9     marlin.relocate_firmware("0x08008800")
  10
  11     def calculate_crc(contents, seed):
  12         accumulating_xor_value = seed;
  13
  14         for i in range(0, len(contents), 4):
  15             value = struct.unpack('<I', contents[ i : i + 4])[0]
  16             accumulating_xor_value = accumulating_xor_value ^ value
  17         return accumulating_xor_value
  18
  19     def xor_block(r0, r1, block_number, block_size, file_key):
  20         # This is the loop counter
  21         loop_counter = 0x0
  22
  23         # This is the key length
  24         key_length = 0x18
  25
  26         # This is an initial seed
  27         xor_seed = 0x4BAD
  28
  29         # This is the block counter
  30         block_number = xor_seed * block_number
  31
  32         #load the xor key from the file
  33         r7 =  file_key
  34
  35         for loop_counter in range(0, block_size):
  36             # meant to make sure different bits of the key are used.
  37             xor_seed = int(loop_counter / key_length)
  38
  39             # IP is a scratch register / R12
  40             ip = loop_counter - (key_length * xor_seed)
  41
  42             # xor_seed = (loop_counter * loop_counter) + block_number
  43             xor_seed = (loop_counter * loop_counter) + block_number
  44
  45             # shift the xor_seed left by the bits in IP.
  46             xor_seed = xor_seed >> ip
  47
  48             # load a byte into IP
  49             ip = r0[loop_counter]
  50
  51             # XOR the seed with r7
  52             xor_seed = xor_seed ^ r7
  53
  54             # and then with IP
  55             xor_seed = xor_seed ^ ip
  56
  57             #Now store the byte back
  58             r1[loop_counter] = xor_seed & 0xFF
  59
  60             #increment the loop_counter
  61             loop_counter = loop_counter + 1
  62
  63     def encrypt_file(input, output_file, file_length):
  64         input_file = bytearray(input.read())
  65         block_size = 0x800
  66         key_length = 0x18
  67
  68         uid_value = uuid.uuid4()
  69         file_key = int(uid_value.hex[0:8], 16)
  70
  71         xor_crc = 0xEF3D4323;
  72
  73         # the input file is exepcted to be in chunks of 0x800
  74         # so round the size
  75         while len(input_file) % block_size != 0:
  76             input_file.extend(b'0x0')
  77
  78         # write the file header
  79         output_file.write(struct.pack(">I", 0x443D2D3F))
  80         # encrypt the contents using a known file header key
  81
  82         # write the file_key
  83         output_file.write(struct.pack("<I", file_key))
  84
  85         #TODO - how to enforce that the firmware aligns to block boundaries?
  86         block_count = int(len(input_file) / block_size)
  87         print ("Block Count is ", block_count)
  88         for block_number in range(0, block_count):
  89             block_offset = (block_number * block_size)
  90             block_end = block_offset + block_size
  91             block_array = bytearray(input_file[block_offset: block_end])
  92             xor_block(block_array, block_array, block_number, block_size, file_key)
  93             for n in range (0, block_size):
  94                 input_file[block_offset + n] = block_array[n]
  95
  96             # update the expected CRC value.
  97             xor_crc = calculate_crc(block_array, xor_crc)
  98
  99         # write CRC
 100         output_file.write(struct.pack("<I", xor_crc))
 101
 102         # finally, append the encrypted results.
 103         output_file.write(input_file)
 104         return
 105
 106     # Encrypt ${PROGNAME}.bin and save it as 'update.cbd'
 107     def encrypt(source, target, env):
 108         firmware = open(target[0].path, "rb")
 109         update = open(target[0].dir.path + '/update.cbd', "wb")
 110         length = os.path.getsize(target[0].path)
 111
 112         encrypt_file(firmware, update, length)
 113
 114         firmware.close()
 115         update.close()
 116
 117     marlin.add_post_action(encrypt);