hashlib suddenly broken

Steven D'Aprano steve+comp.lang.python at pearwood.info
Thu Sep 18 19:07:35 CEST 2014

Larry Martell wrote:

> I am on a mac running 10.8.5, python 2.7
> Suddenly, many of my scripts started failing with:
> ValueError: unsupported hash type sha1
> This just started happening yesterday, and I cannot think of anything
> that I've done that could cause this.

Ah, the ol' "I didn't change anything, I swear!" excuse *wink*

But seriously... did you perhaps upgrade Python prior to yesterday? Or
possibly an automatic update ran?

Check the creation/last modified dates on:


but I expect that's probably not where the problem lies. My *wild guess* is
that your system updated SSL, and removed some underlying SHA-1 library
needed by hashlib. SHA-1 is pretty old, and there is now a known attack on
it, so some over-zealous security update may have removed it.

If that's the case, it really is over-zealous, for although SHA-1 is
deprecated, the threat is still some years away. Microsoft, Google and
Mozilla have all announced that they will continue accepting it until 2017.
I can't imagine why Apple would removed it so soon.


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