Use doc_id with HMAC for symmetric encryption

2 files changed, 10 insertions, 8 deletions

diff --git a/__init__.py b/__init__.py
index 4325d773..9f5d6e22 100644
--- a/__init__.py
+++ b/__init__.py
@@ -6,6 +6,7 @@ import os
 import string
 import random
 import cStringIO
+import hmac
 from soledad.util import GPGWrapper
 
 class Soledad(object):
@@ -39,7 +40,7 @@ class Soledad(object):
     def _load_secret(self):
         try:
             with open(self.SECRET_PATH) as f:
-               self._secret = self._gpg.decrypt(f.read())
+               self._secret = str(self._gpg.decrypt(f.read()))
         except IOError as e:
            raise IOError('Failed to open secret file %s.' % self.SECRET_PATH)
 
@@ -72,12 +73,13 @@ class Soledad(object):
         return str(self._gpg.encrypt(data, self._fingerprint, sign=sign,
                                      passphrase=passphrase, symmetric=symmetric))
 
-    def encrypt_symmetric(self, data, sign=None):
-        return self.encrypt(data, sign=sign, passphrase=self._secret,
-                            symmetric=True)
+    def encrypt_symmetric(self, doc_id, data, sign=None):
+        h = hmac.new(self._secret, doc_id).hexdigest()
+        return self.encrypt(data, sign=sign, passphrase=h, symmetric=True)
 
     def decrypt(self, data, passphrase=None, symmetric=False):
         return str(self._gpg.decrypt(data, passphrase=passphrase))
 
-    def decrypt_symmetric(self, data):
-        return self.decrypt(data, passphrase=self._secret)
+    def decrypt_symmetric(self, doc_id, data):
+        h = hmac.new(self._secret, doc_id).hexdigest()
+        return self.decrypt(data, passphrase=h)
diff --git a/backends/leap.py b/backends/leap.py
index c019ed3f..9fbd49fe 100644
--- a/backends/leap.py
+++ b/backends/leap.py
@@ -37,7 +37,7 @@ class LeapDocument(Document):
         """
         if not self._soledad:
             raise NoSoledadInstance()
-        ciphertext = self._soledad.encrypt_symmetric(self.get_json())
+        ciphertext = self._soledad.encrypt_symmetric(self.doc_id, self.get_json())
         return json.dumps({'_encrypted_json' : ciphertext})
 
     def set_encrypted_json(self, encrypted_json):
@@ -47,7 +47,7 @@ class LeapDocument(Document):
         if not self._soledad:
             raise NoSoledadInstance()
         ciphertext = json.loads(encrypted_json)['_encrypted_json']
-        plaintext = self._soledad.decrypt_symmetric(ciphertext)
+        plaintext = self._soledad.decrypt_symmetric(self.doc_id, ciphertext)
         return self.set_json(plaintext)