Clair vs Open Policy Agent Gatekeeper

Clair is free, self-hosted software that continuously scans container images for vulnerabilities in operating-system bases, installed packages, and programming-language components. Clients use its API to index images and match them against known vulnerabilities. Clair updates its vulnerability database as new issues appear and can reanalyze images without rereading their complete contents. It supports OCI Distribution and Docker v2 images, and lists RHEL, Alpine, Ubuntu, Debian, Oracle, Photon, and SUSE distributions, plus Java, Python, Golang, and Javascript. Deployment options include microservices, monolithic installations, CI pipelines, and disconnected environments. Clair can run as an indexer, matcher, notifier, or combo process. It uses PostgreSQL for persistence and is released as a Quay.io container, with the clairctl command-line tool among its artifacts. Clair runs on Linux, supports registry scanning, and is licensed under Apache 2.0. Runtime protection is not provided.

Open Policy Agent Gatekeeper is a free, open-source Kubernetes policy controller for Linux and self-hosted deployments. It runs as a validating and mutating webhook, enforcing CRD-based policies evaluated by Open Policy Agent. Validation constraints can deny requests, warn, run in dry-run mode or report violations without changing resources. Mutation policies can alter matching resources during admission before validation checks the final object. An audit function periodically evaluates existing cluster resources against constraints to identify pre-existing misconfigurations. The project includes an extensible policy library with parameterized examples, and provider connections to external data such as image registries and directory services. Named integrations or backed services include Azure Policy for Kubernetes, Google Kubernetes Engine Policy Controller, Rancher, AWS EKS Blueprints and Alibaba Cloud. Installation options include prebuilt, development or locally built images and Helm. Gatekeeper requires Kubernetes resources introduced in version 1.16 and cluster-admin permissions for installation. The gator CLI is documented as beta from version 3.11.