SSL Certificate Validation in <v2.0

SSL Certificate Validation in <v2.0

When establishing a secure connection to a cloud provider endpoint, Libcloud verifies server SSL certificate. By default, Libcloud searches paths listed in libcloud.security.CA_CERTS_PATH variable for the CA certificate files.

CA_CERTS_PATH contains common paths to CA bundle installations on the following platforms:

certifi package on PyPi
openssl package on CentOS / Fedora
ca-certificates package on Debian / Ubuntu / Arch / Gentoo
ca_root_nss port on FreeBSD
curl-ca-bundle port on Mac OS X
openssl and curl-ca-bundle homebrew package

If no valid CA certificate files are found, you will see an error message similar to the one below:

No CA Certificates were found in CA_CERTS_PATH.

The easiest way to resolve this issue is to install certifi Python package from PyPi using pip. This package provides curated collection of Root Certificates based on the Mozilla CA bundle. If this package is installed and available, Libcloud will use CA bundle which is bundled by default.

As the list of trusted CA certificates can and does change, you are also encouraged to periodically update this package (pip install --upgrade certifi or similar).

If for some reason you want to avoid this behavior, you can set LIBCLOUD_SSL_USE_CERTIFI environment variable to false. Or even, better provide a direct path to the CA bundle you want to use using SSL_CERT_FILE environment variable as shown below.

Windows Users

The CA loading system does not load the Windows Certificate store, since this is not a directory. Windows users should download the following file and place in a directory like %APPDATA%libcloud or somewhere easily accessible. https://raw.githubusercontent.com/bagder/ca-bundle/master/ca-bundle.crt

Then configure this file using one of the 2 methods in Using a custom CA certificate

Acquiring CA Certificates

If the above packages are unavailable to you, and you don’t wish to roll your own, the makers of cURL provides an excellent resource, generated from Mozilla: http://curl.haxx.se/docs/caextract.html.

Using a custom CA certificate

If you want to use a custom CA certificate file for validating the server certificate, you can do that using two different approaches:

Setting SSL_CERT_FILE environment variable to point to your CA file

SSL_CERT_FILE=/home/user/path-to-your-ca-file.crt python my_script.py

Setting libcloud.security.CA_CERTS_PATH variable in your script to point to your CA file

import libcloud.security
libcloud.security.CA_CERTS_PATH = ['/home/user/path-to-your-ca-file.crt']
# Instantiate and work with the driver here...

Adding additional CA certificate to the path

If you want to add an additional CA certificate to the CA_CERTS_PATH, you can do this by appending a path to your CA file to the libcloud.security.CA_CERTS_PATH list.

For example:

import libcloud.security
libcloud.security.CA_CERTS_PATH.append('/home/user/path-to-your-ca-file.crt')
# Instantiate and work with the driver here...

Disabling SSL certificate validation

Note

Disabling SSL certificate validations makes you vulnerable to MITM attacks so you are strongly discouraged from doing that. You should only disable it if you are aware of the consequences and you know what you are doing.

To disable SSL certificate validation, set libcloud.security.VERIFY_SSL_CERT variable to False at the top of your script, before instantiating a driver and interacting with other Libcloud code.

For example:

import libcloud.security
libcloud.security.VERIFY_SSL_CERT = False
# Instantiate and work with the driver here...

Changing used SSL / TLS version

Note

Linode recently dropped support for TLS v1.0 and it only supports TLS v1.1 and higher. If you are using Linode driver you need to update your code to use TLS v1.1 or TLS v1.2 as shown below.

For compatibility and safety reasons (we also support older Python versions), Libcloud uses TLS v1.0 by default.

If the provier doesn’t support this version or if you want to use a different version because of security reasons (you should always use the highest version which is supported by your system and your provider) you can tell Libcloud to use a different version as shown below.

import ssl
import libcloud.security
libcloud.security.SSL_VERSION = ssl.PROTOCOL_TLSv1_1
# or
libcloud.security.SSL_VERSION = ssl.PROTOCOL_TLSv1_2
# Instantiate and work with the driver here...

Keep in mind that TLS v1.1 and v1.2 is right now only supported in Python >= 3.4 and Python 2.7.9. In addition to that, your system also needs to have a recent version of OpenSSL available.

Another (unsafe and unrecommended) option is to use ssl.PROTOCOL_SSLv23 constant which will let client know to pick the highest protocol version which both the client and server support. If this constant is selected, the client will be selecting between SSL v3.0, TLS v1.0, TLS v1.1 and TLS v1.2.

Keep in mind that SSL v3.0 is considered broken and unsafe and using this option can result in a downgrade attack so we strongly recommend NOT to use it.