Prevent read of user password hash

changeset c9be44cd05e1 did not add the same hiding protection to the new
password_hash field as the password field.
This allow any authenticated user to read the hash of any other user.

CVE-2016-1241
issue5795
review32441002

CHANGELOG

@@ -1,3 +1,4 @@
+* Prevent read of user password hash (CVE-2016-1241)
 * Add database dump cache for tests
 * Remove unused tools: find_in_path, exec_command_pipe and mod10r
 * Implementation of drop_column for SQLite

trytond/res/user.py

@@ -232,6 +232,14 @@ class User(ModelSQL, ModelView):
             vals['menu'] = Action.get_action_id(vals['menu'])
         return vals
 
+    @classmethod
+    def read(cls, ids, fields_names=None):
+        result = super(User, cls).read(ids, fields_names=fields_names)
+        if not fields_names or 'password_hash' in fields_names:
+            for values in result:
+                values['password_hash'] = None
+        return result
+
     @classmethod
     def create(cls, vlist):
         vlist = [cls._convert_vals(vals) for vals in vlist]