75c6ddb5b3
* Add a couple of tweaks to stop the sensor from crashing. * A few more comments and TODOs
160 lines
5.3 KiB
Python
160 lines
5.3 KiB
Python
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import os
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from struct import pack, unpack
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from binascii import hexlify, unhexlify
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import logging
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from hashlib import sha256
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import hmac
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from cryptography.hazmat.primitives import hashes
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from cryptography.hazmat.primitives.asymmetric import ec
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from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
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from cryptography.hazmat.backends import default_backend
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from .tls import tls, hs_key, crt_hardcoded
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from .usb import usb
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from .flash import write_flash, erase_flash, call_cleanups, PartitionInfo, get_flash_info
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from .sensor import reboot, RomInfo
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from .util import assert_status, unhex
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from .blobs import reset_blob
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flash_layout_hardcoded=[
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# id type access offset size
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# lvl
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PartitionInfo(1, 4, 7, 0x00001000, 0x00001000), # cert store
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PartitionInfo(2, 1, 2, 0x00002000, 0x0003e000), # xpfwext
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PartitionInfo(5, 5, 3, 0x00040000, 0x00008000), # ???
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PartitionInfo(6, 6, 3, 0x00048000, 0x00008000), # calibration data
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PartitionInfo(4, 3, 5, 0x00050000, 0x00080000), # template database
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]
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partition_signature=unhex('''
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1db02a886b007e2b47263bb8fe30bd64a1f58bea7b25f1e1ba9ae09add7ecff36333f8198339cdd713f043633710a17bc7b3f418f1d8ff435a1bf47f065dffca
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727109152217fce73bf2bf8e01a1641f6a24b0c492a6a3f10114057275846842b1c8b66bd6700738524d4471bca3315ba23bb832743220ad195b60558aa79a3e
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deb2604834e2bb62e890b0ce405b3b8ef2fec2aab3e22bff23f89a58ff0dc015fece5d3ed3f5496ace879a92980aec9d85eb7e9df245eae03a41acfd4e7d1cb1
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dbd0df42d534904de00b6389f68867646e9d7c3d0b1dffd74070b2d0f2049b9f1dc7b0c9651c59be3ea891674725e1f2f7a484a941615b80211105978369cf71
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''')
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crypto_backend=default_backend()
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def get_partition_signature():
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if usb.usb_dev().idVendor == 0x138a:
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if usb.usb_dev().idProduct == 0x0090:
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return b''
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return partition_signature
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def with_hdr(id, buf):
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return pack('<HH', id, len(buf)) + buf
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def encrypt_key(client_private, client_public):
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x = unhexlify('%064x' % client_public.x)[::-1]
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y = unhexlify('%064x' % client_public.y)[::-1]
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d = unhexlify('%064x' % client_private)[::-1]
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m = x+y+d
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l = 16 - (len(m) % 16)
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m = m + bytes([l])*l
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iv = os.urandom(0x10)
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cipher = Cipher(algorithms.AES(tls.psk_encryption_key), modes.CBC(iv), backend=crypto_backend)
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encryptor = cipher.encryptor()
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c = iv + encryptor.update(m) + encryptor.finalize()
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sig = hmac.new(tls.psk_validation_key, c, sha256).digest()
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return b'\x02' + c + sig
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def make_cert(client_public):
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msg=(pack('<LL', 0x17, 0x20) +
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unhexlify('%064x' % client_public.x)[::-1] +
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(b'\0'*0x24) +
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unhexlify('%064x' % client_public.y)[::-1] +
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(b'\0'*0x4c))
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pk = ec.derive_private_key(hs_key(), ec.SECP256R1(), backend=crypto_backend)
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s=pk.sign(msg, ec.ECDSA(hashes.SHA256()))
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s=pack('<L', len(s)) + s
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msg = msg + s
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msg += b'\0'*(444 - len(msg)) # FIXME not sure this math is right
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return msg
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def serialize_flash_params(ic):
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return pack('<LLxxBx', ic.size, ic.secror_size, ic.sector_erase_cmd)
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def serialize_partition(p):
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b = pack('<BBHLL', p.id, p.type, p.access_lvl, p.offset, p.size)
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b = b + b'\0'*4 + sha256(b).digest()
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return b
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def partition_flash(info, layout, client_public):
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logging.info('Detected Flash IC: %s, %d bytes' % (info.ic.name, info.ic.size))
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cmd = unhex('4f 0000 0000')
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cmd += with_hdr(0, serialize_flash_params(info.ic))
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cmd += with_hdr(1, b''.join([serialize_partition(p) for p in layout]) + get_partition_signature())
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cmd += with_hdr(5, make_cert(client_public))
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cmd += with_hdr(3, crt_hardcoded)
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rsp = tls.cmd(cmd)
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assert_status(rsp)
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rsp = rsp[2:]
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crt_len, rsp=rsp[:4], rsp[4:]
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crt_len, = unpack('<L', crt_len)
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tls.handle_cert(rsp[:crt_len])
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rsp = rsp[crt_len:]
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# ^ TODO - figure out what the rest of rsp means
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def init_flash():
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info = get_flash_info()
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if len(info.partitions) > 0:
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logging.info('Flash has %d partitions.' % len(info.partitions))
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return
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else:
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logging.info('Flash was not initialized yet. Formatting...')
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assert_status(usb.cmd(reset_blob))
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skey = ec.generate_private_key(ec.SECP256R1(), crypto_backend)
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snums = skey.private_numbers()
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client_private = snums.private_value
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client_public = snums.public_numbers
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partition_flash(info, flash_layout_hardcoded, client_public)
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RomInfo.get()
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# ^ TODO: use the firmware version which to lookup pubkey for server cert validation
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try:
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rsp=usb.cmd(unhex('50'))
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assert_status(rsp)
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finally:
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call_cleanups()
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rsp=rsp[2:]
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l,=unpack('<L', rsp[:4])
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if len(rsp) != l:
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raise Exception('Length mismatch')
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zeroes, rsp = rsp[4:-400], rsp[-400:]
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if zeroes != b'\0' * len(zeroes):
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raise Exception('Expected zeroes')
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tls.handle_ecdh(rsp)
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tls.handle_priv(encrypt_key(client_private, client_public))
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tls.open()
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# Wipe newly created partitions clean
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erase_flash(1)
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erase_flash(2)
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erase_flash(5)
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erase_flash(6)
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erase_flash(4)
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# Persist certs and keys on cert partition.
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write_flash(1, 0, tls.makeTlsFlash())
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# Reboot.
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# The device will disconnect and our service will be started by udev as soon as it is connected again.
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reboot()
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