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