How to make Python use CA certificates from Mac OS TrustStore?

Question

I need to use curtom root certificates on the company intranet and loading them in the Mac OS TrustStore (KeyChain) does solve the problem for all browsers and GUI apps.

It seems that it works even with the version of curl that ships with Mac OS X but it doesn't work with python, even the version that ships with Mac OS 10.12 Sierra (Python 2.7.10)

Still, it seems that I would be hit by:

urllib2.URLError: <urlopen error [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:590)> 

How can I solve this?

Because I encounter this issue in lots and lots of Python tools I would really appreciate if I find a way to avoid it without having to patch them.

Providing the custom CA certificate myself is not an option because I cannot patch tens of Python tools that I use.

Most of the tools are using the requests library but there are a few that are using the native ssl support in Python directly.

Answer 1

This is also a problem in Python 3.6 with MacOS Sierrra. I know your use case is different. But I stumbled upon this thread while investigating this problem. So if anyone is also having this article is worth checking out:

http://www.cdotson.com/2017/01/sslerror-with-python-3-6-x-on-macos-sierra/

In a nutshell: Python 3.6 does not rely on MacOS' openSSL anymore. It comes with its own openSSL bundled and doesn't have access on MacOS' root certificates.

You have two options:

Run an install command shipped with Python 3.6

cd /Applications/Python\ 3.6/ ./Install\ Certificates.command 

or

Install the certifi package with

pip install certifi 

I chose the first option and it worked.