[New-bugs-announce] [issue12059] hashlib does not handle missing hash functions correctly

Ian Wienand report at bugs.python.org
Wed May 11 20:59:19 CEST 2011

New submission from Ian Wienand <ian at wienand.org>:

If one of the hash functions isn't defined in _hashlib, the code suggests it should just be skipped

      # this one has no builtin implementation, don't define it

This doesn't happen however; due to ImportError not being caught the module decides the whole _hashlib module isn't available and tries to fall back to the older individual libraries.  You then get thrown an unrelated error about _md5 being unavailable

You can easily replicate this

$ python
Python 2.6.6 (r266:84292, Dec 26 2010, 22:31:48) 
[GCC 4.4.5] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> def foo():
...     raise ValueError
>>> import _hashlib
>>> _hashlib.openssl_sha224 = foo
>>> import hashlib
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python2.6/hashlib.py", line 136, in <module>
    md5 = __get_builtin_constructor('md5')
  File "/usr/lib/python2.6/hashlib.py", line 63, in __get_builtin_constructor
    import _md5
ImportError: No module named _md5

I think the solution is to catch the ImportError in __get_builtin_constructor and, if caught, consider the hash function unsupported

files: hashlib.py.diff
keywords: patch
messages: 135794
nosy: Ian.Wienand
priority: normal
severity: normal
status: open
title: hashlib does not handle missing hash functions correctly
type: behavior
versions: Python 2.6, Python 2.7
Added file: http://bugs.python.org/file21971/hashlib.py.diff

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