Base library code

src/cryptbase/__init__.py

@@ -1 +1,60 @@
 __version__ = '0.0.0'
+
+
+from .cryptbase import AES256CTREncryptor
+from .cryptbase import CryptoContainer
+
+try:
+    from django.db import models
+
+    class EncryptedTextField(models.TextField):
+        description = 'Encrypted data'
+
+        def __init__(self, *args, **kwargs):
+            if 'key' in kwargs:
+                self.__key = kwargs['key']
+                del kwargs['key']
+                self.encryptor = AES256CTREncryptor(bytes.fromhex(self.__key))
+            super().__init__(*args, **kwargs)
+
+        def get_db_prep_value(self, value, *args, **kwargs):
+            if value is None:
+                return None
+            return str(CryptoContainer(plaintext=value, encryptor=self.encryptor))
+
+        def from_db_value(self, value, expression, connection):
+            if value is None:
+                return value
+            return CryptoContainer.from_encrypted(value, self.encryptor).plaintext
+
+        def to_python(self, value):
+            if isinstance(value, str):
+                return CryptoContainer.from_encrypted(value, self.encryptor).plaintext
+            return None
+
+        def deconstruct(self):
+            name, path, args, kwargs = super().deconstruct()
+            return name, path, args, kwargs
+except ImportError:
+    pass
+
+
+try:
+    from sqlalchemy import types
+
+    class EncryptedText(types.TypeDecorator):
+        impl = types.TEXT
+
+        def __init__(self, *args, **kwargs):
+            self.__key = kwargs['key']
+            del kwargs['key']
+            self.encryptor = AES256CTREncryptor(bytes.fromhex(self.__key))
+            super().__init__(*args, **kwargs)
+
+        def process_bind_param(self, value, dialect):
+            return str(CryptoContainer(plaintext=value, encryptor=self.encryptor))
+
+        def process_result_value(self, value, dialect):
+            return CryptoContainer.from_encrypted(value, self.encryptor).plaintext
+except ImportError:
+    pass

src/cryptbase/cryptbase.py

@@ -0,0 +1,63 @@
+import base64
+import secrets
+
+from cryptography.hazmat.primitives.ciphers import Cipher
+from cryptography.hazmat.primitives.ciphers import algorithms
+from cryptography.hazmat.primitives.ciphers import modes
+
+
+class AES256CTREncryptor:
+
+    def __init__(self, key):
+        self.__key = key
+
+    def encrypt(self, plaintext):
+        iv = secrets.token_bytes(16)
+        cipher = Cipher(algorithms.AES(self.__key), modes.CTR(iv))
+        encryptor = cipher.encryptor()
+        ciphertext = encryptor.update(plaintext) + encryptor.finalize()
+        return ciphertext, iv
+
+    def decrypt(self, ciphertext, iv):
+        cipher = Cipher(algorithms.AES(self.__key), modes.CTR(iv))
+        decryptor = cipher.decryptor()
+        return decryptor.update(ciphertext) + decryptor.finalize()
+
+
+class CryptoContainer:
+
+    def __init__(self, **kwargs):
+        if 'encryptor' not in kwargs:
+            raise ValueError()
+
+        if 'plaintext' in kwargs:
+            self.__plaintext = kwargs['plaintext']
+            self.__ciphertext, self.__iv = kwargs['encryptor'].encrypt(self.__plaintext.encode('utf-8'))
+        elif 'ciphertext' in kwargs and 'iv' in kwargs:
+            self.__ciphertext = kwargs['ciphertext']
+            self.__iv = kwargs['iv']
+            self.__plaintext = kwargs['encryptor'].decrypt(self.__ciphertext, self.__iv)
+        else:
+            raise ValueError()
+
+    @property
+    def plaintext(self):
+        return self.__plaintext.decode('utf-8')
+
+    @property
+    def ciphertext(self):
+        return base64.b64encode(self.__ciphertext).decode('ascii')
+
+    @property
+    def iv(self):
+        return base64.b64encode(self.__iv).decode('ascii')
+
+    def __str__(self):
+        return '@'.join([self.ciphertext, self.iv])
+
+    @staticmethod
+    def from_encrypted(container_str, encryptor):
+        ciphertext, iv = container_str.split('@')
+        return CryptoContainer(ciphertext=base64.b64decode(ciphertext),
+                               iv=base64.b64decode(iv),
+                               encryptor=encryptor)