Riccardo Schirone 5080ba5133 Prevents arbitrary code execution during python/object/new constructor (#386) ... * Prevents arbitrary code execution during python/object/new constructor In FullLoader python/object/new constructor, implemented by construct_python_object_apply, has support for setting the state of a deserialized instance through the set_python_instance_state method. After setting the state, some operations are performed on the instance to complete its initialization, however it is possible for an attacker to set the instance' state in such a way that arbitrary code is executed by the FullLoader. This patch tries to block such attacks in FullLoader by preventing set_python_instance_state from setting arbitrary properties. It implements a blacklist that includes `extend` method (called by construct_python_object_apply) and all special methods (e.g. __set__, __setitem__, etc.). Users who need special attributes being set in the state of a deserialized object can still do it through the UnsafeLoader, which however should not be used on untrusted input. Additionally, they can subclass FullLoader and redefine `get_state_keys_blacklist()` to extend/replace the list of blacklisted keys, passing the subclassed loader to yaml.load. * Make sure python/object/new constructor does not set some properties * Add test to show how to subclass FullLoader with new blacklist		2020-03-17 19:09:55 +01:00
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yaml	Prevents arbitrary code execution during python/object/new constructor (#386)	2020-03-17 19:09:55 +01:00