106 lines
4.0 KiB
Python
106 lines
4.0 KiB
Python
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import hashlib, hmac, json
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from base64 import b64encode, b64decode
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from binascii import hexlify, unhexlify
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from Crypto.Cipher import AES
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from Crypto.Random import random
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from copy import deepcopy
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class EncryptionHelper:
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def pure_generatePasswordAndKey(self, password, pw_salt, pw_cost):
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output = hashlib.pbkdf2_hmac('sha512', password.encode(), pw_salt.encode(), pw_cost, dklen=96)
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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 encryptDirtyItems(self, dirty_items, keys):
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return [self.pure_encryptItem(item, keys) for item in dirty_items]
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def decryptResponseItems(self, response_items, keys):
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return [self.pure_decryptItem(item, keys) for item in response_items]
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def pure_encryptItem(self, item, keys):
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uuid = item['uuid']
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content = json.dumps(item['content'])
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item_key = hex(random.getrandbits(512))
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item_key = item_key[2:].rjust(128, '0') # remove '0x', pad to 128
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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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enc_item = deepcopy(item)
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enc_item['content'] = self.pure_encryptString002(content, item_ek, item_ak, uuid)
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enc_item['enc_item_key'] = self.pure_encryptString002(item_key, keys['mk'], keys['ak'], uuid)
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return enc_item
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def pure_decryptItem(self, item, keys):
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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 not content:
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return item
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if content[:3] == '002':
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item_key = self.pure_decryptString002(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_decryptString002(content, item_ek, item_ak, uuid)
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else:
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print('Invalid protocol version.')
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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_encryptString002(self, string_to_encrypt, encryption_key, auth_key, uuid):
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IV = hex(random.getrandbits(128))
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IV = IV[2:].rjust(32, '0') # remove '0x', pad to 32
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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 = 16 - len(pt) % 16
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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(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_decryptString002(self, string_to_decrypt, encryption_key, auth_key, uuid):
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components = string_to_decrypt.split(':')
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version = components[0]
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auth_hash = components[1]
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local_uuid = components[2]
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IV = components[3]
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ciphertext = components[4]
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if local_uuid != uuid:
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print('UUID does not match.')
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return
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string_to_auth = ':'.join([version, uuid, IV, ciphertext])
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local_auth_hash = hmac.new(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('Message has been tampered with.')
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return
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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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return result.decode()
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