Search code examples
pythoncsecuritymd5libcrypto

How do I know if the 'usedforsecurity' flag is supported by hashlib.md5?

When I run the following on my Macbook, I get the error:

>>> import hashlib
>>> hashlib.md5(usedforsecurity=False)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: openssl_md5() takes no keyword arguments

But when I run it on my Linux box, it works!

>>> import hashlib
>>> hashlib.md5(usedforsecurity=False)
<md5 HASH object @ 0x7f763c1375d0>

My problem is, I need to run some safe, non-security related code on my FIPS enabled system (such as managing a cache of user requests which hashes the user query as an MD5 string). Using the usedforsecurity flag prevents a FIPs exception.

This works fine, except when I want to test my code on my Macbook. My Macbook's "libcrypto" library apparently doesn't support this usedforsecurity flag. Is there a good way to detect if the underlying C bindings behind hashlib.md5 support this flag or not?

Solution

  • If you use hashlib.new('md5', usedforsecurity=False) instead of hashlib.md5(usedforsecurity=False) it will not raise exception, even if the keyword argument is not supported.