Small utility to demonstrate the validity / rotation of certificates. Particularly helpful for demonstrating HashiCorp Vault's PKI Secrets Engine in Kubernetes clusters.

Note that this will not show details on the certificate chain used in the process of securing in-transit communication with the application.

Set the following environment variables:

• TLS_CERT_PATH - Filesystem path to certificate file
• CA_CERT_PATH - Filesystem path to issuing CA file

Run the application:

$ python3 app.py
 * Serving Flask app 'app'
 * Debug mode: on
WARNING: This is a development server. Do not use it in a production deployment. Use a production WSGI server instead.
 * Running on http://0.0.0.0:5000
Press CTRL+C to quit
 * Restarting with stat
 * Debugger is active!

Access using a browser either via FQDN, or via the URL presented the CLI (depending on how you're running it):

When using in Kubernetes, it's useful to mount the Secret containing the managed certificates as a volume on a deployment:

When something like the Vault Secrets Operator rotates the certificate, the next request to this app will show the details.

...
    spec:
      volumes:
        - name: short-lived-cert
          secret:
            secretName: short-lived-cert
            defaultMode: 420
          ...
          volumeMounts:
            - name: short-lived-cert
              readOnly: true
              mountPath: /opt/certificate/
          ...
          env:
            - name: TLS_CERT_PATH
              value: /opt/certificate/tls.crt
            - name: CA_CERT_PATH
              value: /opt/certificate/issuing_ca
...