Connaisseur adds Kubernetes image signature verification and digest pinning

Connaisseur is an open-source admission controller designed to secure Kubernetes clusters by validating the authenticity of container images. It intercepts resource creation and update requests to ensure that only images signed by authorized entities are permitted to run within the cluster.

The tool provides a mechanism to replace mutable image tags with immutable digests upon successful verification, preventing potential supply chain attacks where a tag might be redirected to a malicious image. It supports multiple signature standards and offers a non-blocking detection mode to help administrators transition to strict enforcement policies.

Technical capabilities of Connaisseur

• Signature Standard Support: Integrates with Notary, Docker Content Trust, Sigstore/Cosign, and Notation to verify image authenticity.
• Supply Chain Security: Implements image digest pinning, which replaces mutable image references with immutable digests after successful validation.
• Policy Granularity: Allows administrators to define specific validation rules, trusted public keys, and signing authorities based on image repositories, patterns, or Kubernetes namespaces.
• Observability and Alerting: Features built-in integrations for Slack, Opsgenie, Keybase, and Microsoft Teams, with support for custom JSON payloads and Elastic Common Schema exports.
• Operational Modes: Includes a detection mode for monitoring untrusted images without blocking deployments, alongside configurable failure behaviors for when validation services are unreachable.

Why it matters

By supporting diverse signature protocols like Sigstore/Cosign and Notation, Connaisseur helps cloud-native engineers secure the software supply chain across heterogeneous Kubernetes environments. Its ability to pin digests and provide namespace-specific policies makes it a critical tool for system administrators managing production-grade container orchestration.