140 lines
5.1 KiB
Python
140 lines
5.1 KiB
Python
from base64 import b64decode, b64encode
|
|
from binascii import hexlify, unhexlify
|
|
from copy import deepcopy
|
|
import hashlib
|
|
import hmac
|
|
import json
|
|
import sys
|
|
|
|
from Crypto.Cipher import AES
|
|
from Crypto.Random import random
|
|
|
|
BITS_PER_HEX_DIGIT = 4
|
|
|
|
PASS_KEY_LEN = 96
|
|
AES_KEY_LEN = 256
|
|
AES_BLK_SIZE = 16
|
|
AES_STR_KEY_LEN = AES_KEY_LEN // BITS_PER_HEX_DIGIT
|
|
AES_IV_LEN = 128
|
|
AES_STR_IV_LEN = AES_IV_LEN // BITS_PER_HEX_DIGIT
|
|
|
|
class EncryptionHelper:
|
|
def pure_generate_password_and_key(self, password, pw_salt, pw_cost):
|
|
output = hashlib.pbkdf2_hmac(
|
|
'sha512', password.encode(), pw_salt.encode(), pw_cost,
|
|
dklen=PASS_KEY_LEN)
|
|
output = hexlify(output).decode()
|
|
|
|
output_length = len(output)
|
|
split_length = output_length // 3
|
|
pw = output[0 : split_length]
|
|
mk = output[split_length : split_length * 2]
|
|
ak = output[split_length * 2 : split_length * 3]
|
|
|
|
return dict(pw=pw, mk=mk, ak=ak)
|
|
|
|
def encrypt_dirty_items(self, dirty_items, keys):
|
|
return [self.pure_encrypt_item(item, keys) for item in dirty_items]
|
|
|
|
def decrypt_response_items(self, response_items, keys):
|
|
return [self.pure_decrypt_item(item, keys) for item in response_items]
|
|
|
|
def pure_encrypt_item(self, item, keys):
|
|
uuid = item['uuid']
|
|
content = json.dumps(item['content'])
|
|
|
|
# all this is to follow the Standard Notes spec
|
|
item_key = hex(random.getrandbits(AES_KEY_LEN * 2))
|
|
# remove '0x', pad with 0's, then split in half
|
|
item_key = item_key[2:].rjust(AES_STR_KEY_LEN * 2, '0')
|
|
item_ek = item_key[:AES_STR_KEY_LEN]
|
|
item_ak = item_key[AES_STR_KEY_LEN:]
|
|
|
|
enc_item = deepcopy(item)
|
|
enc_item['content'] = self.pure_encrypt_string_002(
|
|
content, item_ek, item_ak, uuid)
|
|
enc_item['enc_item_key'] = self.pure_encrypt_string_002(
|
|
item_key, keys['mk'], keys['ak'], uuid)
|
|
|
|
return enc_item
|
|
|
|
def pure_decrypt_item(self, item, keys):
|
|
if item['deleted']:
|
|
return item
|
|
|
|
uuid = item['uuid']
|
|
content = item['content']
|
|
enc_item_key = item['enc_item_key']
|
|
|
|
if content[:3] == '001':
|
|
print('Old encryption protocol detected. This version is not '
|
|
'supported by standardnotes-fs. Please resync all of '
|
|
'your notes by following the instructions here:\n'
|
|
'https://standardnotes.org/help/resync')
|
|
sys.exit(1)
|
|
elif content[:3] == '002':
|
|
item_key = self.pure_decrypt_string_002(
|
|
enc_item_key, keys['mk'], keys['ak'], uuid)
|
|
item_key_length = len(item_key)
|
|
item_ek = item_key[:item_key_length//2]
|
|
item_ak = item_key[item_key_length//2:]
|
|
|
|
dec_content = self.pure_decrypt_string_002(
|
|
content, item_ek, item_ak, uuid)
|
|
else:
|
|
print('Invalid protocol version. This could indicate tampering or '
|
|
'that something is wrong with the server. Exiting.')
|
|
sys.exit(1)
|
|
|
|
dec_item = deepcopy(item)
|
|
dec_item['content'] = json.loads(dec_content)
|
|
|
|
return dec_item
|
|
|
|
def pure_encrypt_string_002(self, string_to_encrypt, encryption_key,
|
|
auth_key, uuid):
|
|
IV = hex(random.getrandbits(AES_IV_LEN))
|
|
IV = IV[2:].rjust(AES_STR_IV_LEN, '0') # remove '0x', pad with 0's
|
|
|
|
cipher = AES.new(unhexlify(encryption_key), AES.MODE_CBC, unhexlify(IV))
|
|
pt = string_to_encrypt.encode()
|
|
pad = AES_BLK_SIZE - len(pt) % AES_BLK_SIZE
|
|
padded_pt = pt + pad * bytes([pad])
|
|
ciphertext = b64encode(cipher.encrypt(padded_pt)).decode()
|
|
|
|
string_to_auth = ':'.join(['002', uuid, IV, ciphertext])
|
|
auth_hash = hmac.new(
|
|
unhexlify(auth_key), string_to_auth.encode(), 'sha256').digest()
|
|
auth_hash = hexlify(auth_hash).decode()
|
|
|
|
result = ':'.join(['002', auth_hash, uuid, IV, ciphertext])
|
|
|
|
return result
|
|
|
|
def pure_decrypt_string_002(self, string_to_decrypt, encryption_key,
|
|
auth_key, uuid):
|
|
components = string_to_decrypt.split(':')
|
|
version, auth_hash, local_uuid, IV, ciphertext = components
|
|
|
|
if local_uuid != uuid:
|
|
print('UUID does not match. This could indicate tampering or '
|
|
'that something is wrong with the server. Exiting.')
|
|
sys.exit(1)
|
|
|
|
string_to_auth = ':'.join([version, uuid, IV, ciphertext])
|
|
local_auth_hash = hmac.new(
|
|
unhexlify(auth_key), string_to_auth.encode(), 'sha256').digest()
|
|
local_auth_hash = hexlify(local_auth_hash).decode()
|
|
|
|
if local_auth_hash != auth_hash:
|
|
print('Auth hash does not match. This could indicate tampering or '
|
|
'that something is wrong with the server. Exiting.')
|
|
sys.exit(1)
|
|
|
|
cipher = AES.new(unhexlify(encryption_key), AES.MODE_CBC, unhexlify(IV))
|
|
result = cipher.decrypt(b64decode(ciphertext))
|
|
result = result[:-result[-1]] # remove PKCS#7 padding
|
|
result = result.decode()
|
|
|
|
return result
|