Basic support for cryptography.io

Still needs better hash function

jrnl/upgrade.py

@@ -1,3 +1,30 @@
+from cryptography.hazmat.backends import default_backend
+from cryptography.hazmat.primitives import padding
+from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
+import hashlib
+import util
+from . import __version__
+import sys
+
+def upgrade_encrypted_journal(filename, key_plain):
+    """Decrypts a journal in memory using the jrnl 1.x encryption scheme
+    and returns it in plain text."""
+    with open(filename) as f:
+        iv_cipher = f.read()
+    iv, cipher = iv_cipher[:16], iv_cipher[16:]
+    decryption_key = hashlib.sha256(key_plain.encode('utf-8')).digest()
+    decryptor = Cipher(algorithms.AES(decryption_key), modes.CBC(iv), default_backend())
+    plain_padded = decryptor.update(cipher)
+    try:
+        plain_padded += decryptor.finalize()
+        unpadder = padding.PKCS7(algorithms.AES.block_size).unpadder()
+        plain = unpadder.update(plain_padded)
+        plain += unpadder.finalize()
+    except ValueError:
+        return None
+    return plain
+
+
 def upgrade_jrnl_if_necessary(config_path):
     with open(config_path) as f:
         config = f.read()