fat_split.py

#!/usr/local/bin/python
import sys
import struct

if len(sys.argv)-1 < 1:
    print('usage: {} <binary>'.format(sys.argv[0]))
    sys.exit(1)

f = open(sys.argv[1], 'rb')
data = f.read()
f.close()

offset = 0

# FAT header
h = struct.unpack_from('<LL', data, offset)
offset += 8
if h[0] != 0xcafebabe:
    print('FAT_MAGIC is wrong')
    sys.exit(1)

print('Number of structs: {}'.format(h[1]))

for x in range(0, h[1]):
    s = struct.unpack_from('<LLLLL', data, offset)
    offset += 20
    print('CPU type 0x{:x} and sub type 0x{:x}'.format(s[0], s[1]))
    print('Offset {} and size {}'.format(s[2], s[3]))

    if (s[0] & 0x1000007 == 0x1000007): # CPU_TYPE_X86_64
        suffix = 'x64'
    elif (s[0] & 0x100000C == 0x100000C): # CPU_TYPE_ARM64
        suffix = 'arm64'
    else:
        suffix = str(s[0])

    begining = s[2]
    end = s[2] + s[3]
    f = open(sys.argv[1] + '_' + suffix, "wb")
    f.write(data[begining:end])
    f.close()