Bug 1528775

Description of problem:

Changes made to the hashlib module included in the Python standard library as part of SCL Python 3.6 will prevent use of Django with that Python version.

Version-Release number of selected component (if applicable):

SCL Python 3.6

How reproducible:

Always.

Steps to Reproduce:

The problem is exhibited with the following small test case.

import hashlib

class Test:
    digest = hashlib.sha256

    def check(self):
        print(self.digest)

    def name(self):
        print(self.digest().name)

t = Test()

t.check()
t.name()

Run this with SCL Python 3.5, or any non SCL Python 3.6 distribution and it will work fine.

If run with SCL Python 3.6, it fails.

Actual results:

$ python3.6 bug.py
<bound method openssl_sha256 of <__main__.Test object at 0x7f437c2616a0>>
Traceback (most recent call last):
  File "bug.py", line 15, in <module>
    t.name()
  File "bug.py", line 10, in name
    print(self.digest().name)
  File "/opt/app-root/lib64/python3.6/hashlib.py", line 90, in inner
    return func(*args, **kwargs)
TypeError: object supporting the buffer API required

Expected results:

$ python3.6 bug.py
<built-in function openssl_sha256>
sha256

Additional info:

The way this breaks Django is that it isn't possible to create a super user account for Django by running 'python manage.py createsuperuser'.

This will be a significant problem for OpenShift where SCL Python 3.6 is used in the S2I builder for Python 3.6. When this S2I builder makes its way into OpenShift Online and other OpenShift 3.7 installations, it will not be possible to create those users when using Django, forcing users to go back to using Python 3.5.

An issue has also been created against OpenShift Python S2I builder image at:

* https://github.com/sclorg/s2i-python-container/issues/237

The problem code in the hashlib changes made for SCL are:

# Code in hashlib.py which causes issue.

import functools
def __ignore_usedforsecurity(func):
    """Used for sha3_* functions. Until OpenSSL implements them, we want
    to use them from Python _sha3 module, but we want them to accept
    usedforsecurity argument too."""
    # TODO: remove this function when OpenSSL implements sha3
    @functools.wraps(func)
    def inner(*args, **kwargs):
        if 'usedforsecurity' in kwargs:
            kwargs.pop('usedforsecurity')
        return func(*args, **kwargs)
    return inner
 
  ....
  
  for __func_name in __always_supported:
    # try them all, some may not work due to the OpenSSL
    # version not supporting that algorithm.
    try:
        func = __get_hash(__func_name)
        if 'sha3_' or 'blake2' or 'shake_' in __func_name:
            func = __ignore_usedforsecurity(func)
        globals()[__func_name] = func
    except ValueError:
        import logging
        logging.exception('code for hash %s was not found.', __func_name)

The simplistic decorator implementation fails when used in a situation where method binding against None occurs, which happens when function with decorator applied is saved as class attribute and then accessed via self.