Issue 22172: Local files shadow system modules, even from system modules (original) (raw)

In Python 3.4 (but not 3.2 or 2.7) when a system module does an import then files with the same name in the directory of the original python script which match that name are used.

E.g. With a directory containing: test.py: #!/usr/bin/env python3 from collections import OrderedDict print('do stuff')

operator.py: #!/usr/bin/env python3 print('EXPLOIT!')

Running test.py will cause: EXPLOIT! Traceback (most recent call last): File "./test.py", line 4, in from collections import OrderedDict File "/usr/lib/python3.4/collections/init.py", line 11, in from operator import itemgetter as _itemgetter, eq as _eq ImportError: cannot import name 'itemgetter'

While test.py is perfectly innocent it is in the same directory as the nasty operator.py and test.py makes no reference at all to operator.py but when 'collections' is imported it imports from operator which is resolved to operator.py in the local directory

This is a security vulnerability because it is possible to verify that a python script is safe to run by reading its code and then on running it find that other code is implicitly loaded by the system libraries which is never referenced in the original file or part of any of the standard libraries.

It is also rather confusing but a related issue is already filed for that in . This is similar to the standard name shadowing trap http://python-notes.curiousefficiency.org/en/latest/python_concepts/import_traps.html#the-name-shadowing-trap but now applies to other files in the source directory in a way which it didn't in previous versions of python. I suspect this was introduced in python 3.3 through changes to the import system and init.py becoming optional but I don't have a 3.3 install to check that with.

sys.path here is: ['/auto/homes/drt24/pythontest', '/usr/lib/python3.4', '/usr/lib/python3.4/plat-x86_64-linux-gnu', '/usr/lib/python3.4/lib-dynload', '/usr/local/lib/python3.4/dist-packages', '/usr/lib/python3/dist-packages'] Running Python 3.4.0-0ubuntu2 on Ubuntu 14.04.1 LTS with Linux 3.13.0-32-generic

This is not new behaviour. It's just normal system shadowing:

$ python test.py Traceback (most recent call last): File "test.py", line 1, in import collections File "/usr/lib64/python2.7/collections.py", line 9, in from operator import itemgetter as _itemgetter, eq as _eq ImportError: cannot import name itemgetter

Avoiding that behaviour is what the new isolated mode is for:

$ ~/devel/py34/python -I test.py $