[omemo] Fix old invalid BLOB database values

The way BLOBs are written to the database has changed in python3
So we read all BLOB values cast them to BLOB then write them back to
the table

Fixes #402, #278

omemo/backend/liteaxolotlstore.py

@@ -254,6 +254,30 @@ class LiteAxolotlStore(AxolotlStore):
                     END TRANSACTION;
                 """ % convert)
 
+        if self.user_version() < 8:
+            # Sanitize invalid BLOBs from the python2 days
+            query_keys = '''SELECT recipient_id, registration_id,
+                            CAST(public_key as BLOB) as public_key,
+                            CAST(private_key as BLOB) as private_key,
+                            timestamp, trust, shown
+                            FROM identities'''
+            rows = self._con.execute(query_keys).fetchall()
+
+            delete = 'DELETE FROM identities'
+            self._con.execute(delete)
+
+            insert = '''INSERT INTO identities (
+                        recipient_id, registration_id, public_key, private_key,
+                        timestamp, trust, shown)
+                        VALUES (?, ?, ?, ?, ?, ?, ?)'''
+            for row in rows:
+                try:
+                    self._con.execute(insert, row)
+                except Exception as error:
+                    self._log.warning(error)
+            self._con.execute('PRAGMA user_version=8')
+            self._con.commit()
+
     def loadSignedPreKey(self, signedPreKeyId):
         query = 'SELECT record FROM signed_prekeys WHERE prekey_id = ?'
         result = self._con.execute(query, (signedPreKeyId, )).fetchone()