Closes issue 11133. Fixes two cases where inspect.getattr_static could trigger code execution

This commit is contained in:
Michael Foord 2011-03-15 19:20:44 -04:00
parent c867239a31
commit dcebe0f2dc
4 changed files with 75 additions and 13 deletions

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@ -589,13 +589,10 @@ but avoids executing code when it fetches attributes.
that raise AttributeError). It can also return descriptors objects
instead of instance members.
.. versionadded:: 3.2
If the instance `__dict__` is shadowed by another member (for example a
property) then this function will be unable to find instance members.
The only known case that can cause `getattr_static` to trigger code execution,
and cause it to return incorrect results (or even break), is where a class uses
:data:`~object.__slots__` and provides a `__dict__` member using a property or
descriptor. If you find other cases please report them so they can be fixed
or documented.
.. versionadded:: 3.2
`getattr_static` does not resolve descriptors, for example slot descriptors or
getset descriptors on objects implemented in C. The descriptor object

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@ -1069,15 +1069,16 @@ def _check_instance(obj, attr):
instance_dict = object.__getattribute__(obj, "__dict__")
except AttributeError:
pass
return instance_dict.get(attr, _sentinel)
return dict.get(instance_dict, attr, _sentinel)
def _check_class(klass, attr):
for entry in _static_getmro(klass):
try:
return entry.__dict__[attr]
except KeyError:
pass
if not _shadowed_dict(type(entry)):
try:
return entry.__dict__[attr]
except KeyError:
pass
return _sentinel
def _is_type(obj):
@ -1087,6 +1088,19 @@ def _is_type(obj):
return False
return True
def _shadowed_dict(klass):
dict_attr = type.__dict__["__dict__"]
for entry in _static_getmro(klass):
try:
class_dict = dict_attr.__get__(entry)["__dict__"]
except KeyError:
pass
else:
if not (type(class_dict) is types.GetSetDescriptorType and
class_dict.__name__ == "__dict__" and
class_dict.__objclass__ is entry):
return True
return False
def getattr_static(obj, attr, default=_sentinel):
"""Retrieve attributes without triggering dynamic lookup via the
@ -1101,8 +1115,9 @@ def getattr_static(obj, attr, default=_sentinel):
"""
instance_result = _sentinel
if not _is_type(obj):
instance_result = _check_instance(obj, attr)
klass = type(obj)
if not _shadowed_dict(klass):
instance_result = _check_instance(obj, attr)
else:
klass = obj

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@ -906,6 +906,53 @@ class TestGetattrStatic(unittest.TestCase):
self.assertEqual(inspect.getattr_static(Something(), 'foo'), 3)
self.assertEqual(inspect.getattr_static(Something, 'foo'), 3)
def test_dict_as_property(self):
test = self
test.called = False
class Foo(dict):
a = 3
@property
def __dict__(self):
test.called = True
return {}
foo = Foo()
foo.a = 4
self.assertEqual(inspect.getattr_static(foo, 'a'), 3)
self.assertFalse(test.called)
def test_custom_object_dict(self):
test = self
test.called = False
class Custom(dict):
def get(self, key, default=None):
test.called = True
super().get(key, default)
class Foo(object):
a = 3
foo = Foo()
foo.__dict__ = Custom()
self.assertEqual(inspect.getattr_static(foo, 'a'), 3)
self.assertFalse(test.called)
def test_metaclass_dict_as_property(self):
class Meta(type):
@property
def __dict__(self):
self.executed = True
class Thing(metaclass=Meta):
executed = False
def __init__(self):
self.spam = 42
instance = Thing()
self.assertEqual(inspect.getattr_static(instance, "spam"), 42)
self.assertFalse(Thing.executed)
class TestGetGeneratorState(unittest.TestCase):

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@ -40,6 +40,9 @@ Core and Builtins
Library
-------
- Issue #11133: fix two cases where inspect.getattr_static can trigger code
execution. Patch by Daniel Urban.
- Issue #11501: disutils.archive_utils.make_zipfile no longer fails if zlib is
not installed. Instead, the zipfile.ZIP_STORED compression is used to create
the ZipFile. Patch by Natalia B. Bidart.
@ -48,7 +51,7 @@ Library
encoding was not done if euc-jp or shift-jis was specified as the charset.
- Issue #11500: Fixed a bug in the os x proxy bypass code for fully qualified
IP addresses in the proxy exception list.
IP addresses in the proxy exception list.
- Issue #11491: dbm.error is no longer raised when dbm.open is called with
the "n" as the flag argument and the file exists. The behavior matches