SSL error with Python requests despite up-to-date dependencies

Question

I am getting an SSL "bad handshake" error. Most similar responses to this problem seem to stem from old libraries, 1024bit cert. incompatibility, etc... I think i'm up to date, and can't figure out why i'm getting this error.

SETUP:

• requests 2.13.0
• certifi 2017.01.23
• 'OpenSSL 1.0.2g 1 Mar 2016'

I'm hitting this API (2048bit certificate key): https://api.sidecar.io/rest/v1/provision/application/device/count/

And getting this error: requests.exceptions.SSLError: ("bad handshake: Error([('SSL routines', 'ssl3_get_server_certificate', 'certificate verify failed')],)",)

See l.44 of https://github.com/sidecar-io/sidecar-python-sdk/blob/master/sidecar.py

If I turn verify=False in requests, I can bypass, but i'd rather figure out why the certification is failing.

Any help is greatly appreciated; thanks!

Answer 1

The validation fails because the server you access is setup improperly, i.e. it is not a fault of your setup or code. Looking at the report from SSLLabs you see

This server's certificate chain is incomplete. Grade capped to B.

This means that the server sends a certificate chain which is missing an intermediate certificate to the trusted root and thus your client can not build the trust chain. Most desktop browsers work around this problem by trying to get the missing certificate from somewhere else but normal TLS libraries will fail in this case. You would need to explicitly add the missing chain certificate as trusted to work around this problem:

import requests
requests.get('https://api.sidecar.io', verify = 'mycerts.pem')

mycerts.pem should contain the missing intermediate certificate and the trusted root certificate. A tested version for mycerts.pem can be found in http://pastebin.com/aZSKfyb7.