DS4Key generation

gen_ds4key.py

#!/usr/bin/env python3

from Cryptodome.PublicKey import RSA
from Cryptodome.Signature import pss
from Cryptodome.Hash import SHA256
from Cryptodome.Math.Numbers import Integer

import io
import shutil
import sys

if __name__ == '__main__':
    if len(sys.argv) < 4:
        print(f'Usage {sys.argv[0]} ca serial out')
        print('Serial format: 00000000000000000001TTTTNNNNNNNN (T: type [1|2: DS4, 3: A7105], N: actual serial)')
        sys.exit(1)
    with open(sys.argv[1], 'rb') as f:
        ca = RSA.import_key(f.read())
    if not ca.can_sign:
        raise RuntimeError('CA private key missing.')
    ca_pss = pss.new(ca)

    serial = bytes.fromhex(sys.argv[2])
    if len(serial) != 16:
        raise RuntimeError('Bad serial.')

    ds4key_key = RSA.generate(2048)
    buf = io.BytesIO()
    #buf.write(b'\x00' * 8)
    #buf.write(b'\x00\x01\x00\x01\xde\xad\xbe\xef')
    buf.write(serial)
    buf.write(ds4key_key.n.to_bytes(0x100, 'big'))
    buf.write(ds4key_key.e.to_bytes(0x100, 'big'))

    sha = SHA256.new(buf.getvalue())
    sig = ca_pss.sign(sha)
    buf.write(sig)

    pq = Integer(ds4key_key.q).inverse(ds4key_key.p)
    dp1 = Integer(ds4key_key.d) % (ds4key_key.p-1)
    dq1 = Integer(ds4key_key.d) % (ds4key_key.q-1)

    buf.write(ds4key_key.p.to_bytes(0x80, 'big'))
    buf.write(ds4key_key.q.to_bytes(0x80, 'big'))
    buf.write(dp1.to_bytes(0x80))
    buf.write(dq1.to_bytes(0x80))
    buf.write(pq.to_bytes(0x80))

    buf.seek(0)

    with open(sys.argv[3], 'wb') as f:
        shutil.copyfileobj(buf, f)