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105 lines
4.0 KiB
105 lines
4.0 KiB
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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