Validate certificates on HTTPS connections to avoid man-in-the-middle attacks

When developing a module that makes secure HTTPS connections, use a library that verifies certificates. Many such libraries also provide an option to ignore certificate verification failures. These options should be exposed to the OpenStack deployer to choose their level of risk.

Although the title of this guideline calls out HTTPS, verifying the identity of the hosts you are connecting to applies to most protocols (SSH, LDAPS, etc).

Incorrect

import requests
requests.get('https://www.openstack.org/', verify=False)

The example above uses verify=False to bypass the check of the certificate received against those in the CA trust store.

It is important to note that modules such as httplib within the Python standard library did not verify certificate chains until it was fixed in 2.7.9 release. For more specifics about the modules affected refer to CVE-2014-9365 <https://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2014-9365>.

Correct

import requests
requests.get('https://www.openstack.org/', verify=CONF.ca_file)

The example above uses the variable CONF.ca_file to store the location of the CA trust store, which is used to confirm that the certificate received is from a trusted authority.

Consequences

A main-in-the-middle (MITM) attack can allow a party to monitor, copy, and manipulate all data transferred between the parties. The impact of this depends on what data is sent. Customer satisfaction survey data will be less valuable than banking passwords and account information.

Table Of Contents

Previous topic

Create, use, and remove temporary files securely

This Page