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# SPDX-License-Identifier: GPL-3.0+
# Copyright (C) 2020 nlscc
""" Calculate keys and decrypt encrypted firmware packages. """
import hashlib
import xml.etree.ElementTree as ET
from Cryptodome.Cipher import AES
from clint.textui import progress
from . import request
from . import fusclient
# PKCS#7 unpad
unpad = lambda d: d[:-d[-1]]
def getv4key(version, model, region):
""" Retrieve the AES key for V4 encryption. """
client = fusclient.FUSClient()
req = request.binaryinform(version, model, region, client.nonce)
resp = client.makereq("NF_DownloadBinaryInform.do", req)
root = ET.fromstring(resp)
fwver = root.find("./FUSBody/Results/LATEST_FW_VERSION/Data").text
logicval = root.find("./FUSBody/Put/LOGIC_VALUE_FACTORY/Data").text
deckey = request.getlogiccheck(fwver, logicval)
return hashlib.md5(deckey.encode()).digest()
def getv2key(version, model, region):
""" Calculate the AES key for V2 (legacy) encryption. """
deckey = region + ":" + model + ":" + version
return hashlib.md5(deckey.encode()).digest()
def decrypt_progress(inf, outf, key, length):
""" Decrypt a stream of data while showing a progress bar. """
cipher = AES.new(key, AES.MODE_ECB)
if length % 16 != 0:
raise Exception("invalid input block size")
chunks = length//4096+1
for i in progress.bar(range(chunks)):
block = inf.read(4096)
if not block:
break
decblock = cipher.decrypt(block)
if i == chunks - 1:
outf.write(unpad(decblock))
else:
outf.write(decblock)
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