Automate Kubernetes Image Vulnerability Scanning

josepraveen Posted on May 30 Automate Kubernetes Image Vulnerability Scanning # kubernetes # trivy # devops # devsecops Security in a cloud-native environment is only as strong as its weakest link. A recent security audit revealed a critical gap: container images were being deployed to our cluster with outdated software versions harboring numerous vulnerabilities. To solve this, we are implementing an ImagePolicyWebhook . By configuring an Admission Controller to point to a webhook backend image scanner, we can intercept deployment requests and reject any image that doesn't meet our security standards. The Solution In this walkthrough, we will configure the Kubernetes API server to communicate with an existing scanner (like Trivy) via a webhook. 1. Configure the Admission Controller First, we need to define the configuration for the ImagePolicyWebhook plugin. This file tells Kubernetes where to find the backend credentials and how to behave if the scanner is unreachable. Edit the configuration file: sudo vi /etc/kubernetes/admission-control/admission-control.conf Enter fullscreen mode Exit fullscreen mode Paste the following configuration: apiVersion : apiserver.config.k8s.io/v1 kind : AdmissionConfiguration plugins : - name : ImagePolicyWebhook configuration : imagePolicy : kubeConfigFile : /etc/kubernetes/admission-control/imagepolicy_backend.kubeconfig allowTTL : 50 denyTTL : 50 retryBackoff : 500 defaultAllow : false # Fails closed for security Enter fullscreen mode Exit fullscreen mode Pro Tip: Setting defaultAllow: false ensures that if the scanner is down, no unverified images are allowed into the cluster. 2. Point the Kubeconfig to the Backend Webhook The Admission Controller needs a kubeconfig file to know the endpoint of the scanning service. Edit the kubeconfig: sudo vi /etc/kubernetes/admission-control/imagepolicy_backend.kubeconfig Enter fullscreen mode Exit fullscreen mode Update the server endpoint: Locate the server line under the cluster section and