Security is paramount in the world of containerised applications. Malicious actors constantly seek vulnerabilities to exploit, and your container images are a prime target. But it is possible to fortify your Kubernetes cluster and safeguard your applications, by leveraging image signatures and Kyverno.
Why do image signatures matter?
Container images are the building blocks of your applications. If an attacker compromises an image, they can inject malware or gain unauthorised access to your system. Image signatures offer a critical layer of defence. By signing your images with a cryptographic key, you can verify their authenticity and integrity. Any unauthorised modifications will invalidate the signature, alerting you to a potential security breach.
Introducing Kyverno: your Kubernetes policy enforcer
Kyverno is your Kubernetes policy engine. It acts as a gatekeeper, enforcing security policies on deployments within your cluster. Kyverno leverages image signatures to ensure only authorised and verified images are deployed.
Kyverno: enforcing image security
This policy engine takes image security to the next level. It acts as an admission controller, intercepting requests to your cluster and applying security policies. You can define Kyverno policies to validate image signatures before deployment.
Here's how it works:
- Policy Definition: You define a Kyverno policy that specifies the public key for verification. This key corresponds to the private key used for signing images with Notation.
- Admission Request: When a deployment request is submitted, Kyverno intercepts it.
- Signature Verification: Kyverno checks the image signature against the defined public key.
- Enforcement: If the signature is valid, the deployment proceeds. If not, Kyverno rejects the request, preventing potentially compromised images from deploying.
The perfect match: Image Signing and Kyverno
Let's explore how these two powerful tools work in tandem:
- Signing Your Images: Tools like Cosign can be used to generate a cryptographic key pair. The private key is used to sign your container images, while the public key is used for verification.
- Kyverno Policy Implementation: Kyverno policies are written in YAML and reside within your cluster as Kubernetes resources. These policies can leverage the verifyImages rule to specify that deployments must use signed images and reference the appropriate public key for verification.
- Enforcing Security: When a deployment is attempted, Kyverno intercepts the request. It checks the image references against the defined policy. If the image is signed and the signature validates using the provided public key, the deployment proceeds. However, if the image is unsigned or the signature fails verification, Kyverno blocks the deployment, preventing a potentially compromised image from reaching your cluster.
The benefits of this approach
- Enhanced security: Image signatures and Kyverno provide a robust defence against unauthorised modifications and malware injection in container images.
- Improved trust: By verifying image authenticity, you ensure your applications are built from trusted sources.
- Streamlined workflows: Kyverno policies automate security checks, freeing you from manual verification tasks.
In this blog post, we've explored the critical role of image signatures and Kyverno in bolstering the security of your Kubernetes cluster and applications. By combining the power of image verification with policy enforcement, you can significantly reduce the risk of malicious attacks targeting your containerized workloads.
In the next part, we'll delve into the practical implementation steps. These will include configuring image signing mechanisms, crafting effective Kyverno policies, and integrating these solutions into your CI/CD pipeline. By following these guidelines, you'll be well-equipped to protect your applications from malicious attacks.