How do I use a .cer file as part of a python request

Question

Say that I have a cer file called symantec-class3.cer, this is what I'm trying:

headers = {"content-type": "application/json"}
api_url = "https://www.someurl.com/search"
pprint.pprint(requests.post(api_url, auth=HTTPBasicAuth(username, password), verify="symantec-class3.cer", data=json.dumps(payload), headers=headers).json())

This is not liking it and spews out the following error:

requests.exceptions.SSLError: [Errno 0] _ssl.c:344: error:00000000:lib(0):func(0):reason(0)

It works fine if I turn verify False, but I'm trying to use a cert file in my local directory.

Answer 1

Python expect cert in PEM format.

So you should extract the public key component from the X509 certificate using the openssl x509 command.

.cer extension often means a binary DER format, so this command should extract the public key in a form that can be used by pycrypto:

openssl x509 -inform der -pubkey -noout -in you.cer >public_key.pem