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Resource Reference

Installing Kritis, creates a number of resources in your cluster. Here are the most important ones:

Resource Name Resource Kind Description
kritis-validation-hook ValidatingWebhookConfiguration This is Kubernetes Validating Admission Webhook which enforces the policies.
imagesecuritypolicies.kritis.grafeas.io crd This CRD defines the image security policy kind ImageSecurityPolicy.
attestationauthorities.kritis.grafeas.io crd The CRD defines the attestation authority policy kind AttestationAuthority.
tls-webhook-secret secret Secret required for ValidatingWebhookConfiguration

kritis-validation-hook

The validating admission Webhook runs a https service and a background cron job. The webhook, runs when pods and deployments are created or updated in your cluster. To view webhook, run

kubectl describe ValidatingWebhookConfiguration kritis-validation-hook

The cron job validates and reconcile policies on an hourly basis, and ads labels and annotations to pods out of policy. You may force it to run via:

kubectl exec -l label=kritis-validation-hook -- /kritis/kritis-server --run-cron

To view the list of pods it has annotated:

kubetl get pods -l kritis.grafeas.io/invalidImageSecPolicy=invalidImageSecPolicy

ImageSecurityPolicy CRD

ImageSecurityPolicy is Custom Resource Definition which enforce policies. The ImageSecurityPolicy are Namespace Scoped meaning, it will only be verified against pods in the same namespace. You can deploy multiple ImageSecurityPolicies in different namespaces, ideally one per namespace.

Example policy:

apiVersion: kritis.github.com/v1beta1
kind: ImageSecurityPolicy
metadata:
    name: my-isp
    namespace: example-namespace
spec:
  imageWhitelist:
  - gcr.io/my-project/whitelist-image@sha256:<DIGEST>
  packageVulnerabilityPolicy:
    maximumSeverity: MEDIUM
    whitelistCVEs:
      providers/goog-vulnz/notes/CVE-2017-1000082
      providers/goog-vulnz/notes/CVE-2017-1000082

To view the CRD:

kubectl describe crd imagesecuritypolicies.kritis.grafeas.io

To list all Image Security Policies.

kubectl get ImageSecurityPolicy --all-namespaces

Example output:

NAMESPACE             NAME      AGE
example-namespace     my-isp    22h
qa                    qa-isp    11h

To view the active ImageSecurityPolicy:

% kubectl describe ImageSecurityPolicy my-isp

Image Security Policy Spec description:

Field Default (if applicable) Description
imageWhitelist List of images that are whitelisted and are not inspected by Admission Controller.
packageVulnerabilityPolicy.whitelistCVEs List of CVEs which will be ignored.
packageVulnerabilityPolicy.maximumSeverity ALLOW_ALL Tolerance level for vulnerabilities found in the container image.
packageVulnerabilityPolicy.maximumFixUnavailableSeverity ALLOW_ALL The tolerance level for vulnerabilities found that have no fix available.

Here are the valid values for Policy Specs.

Field Value Outcome
packageVulnerabilityPolicy.maximumSeverity LOW Only allow containers with low vulnerabilities.
MEDIUM Allow Containers with Low and Medium vulnerabilities.
HIGH Allow Containers with Low, Medium & High vulnerabilities.
ALLOW_ALL Allow all vulnerabilities.
BLOCK_ALL Block all vulnerabilities except listed in whitelist.
packageVulnerabilityPolicy.maximumFixUnavailableSeverity LOW Only allow containers with low unpatchable vulnerabilities.
MEDIUM Allow Containers with Low and Medium unpatchable vulnerabilities.
HIGH Allow Containers with Low, Medium & High unpatchaable vulnerabilities.
ALLOW_ALL Allow all unpatchable vulnerabilities.
BLOCK_ALL Block all unpatchable vulnerabilities except listed in whitelist.

AttestationAuthority CRD

The webhook will attest valid images once they pass the validity check. This is important because re-deployments can occur from scaling events,rescheduling, termination, etc. Attested images are always admitted in custer. This allows users to manually deploy a container with an older image which was validated in past.

To view the attesation authority CRD run,

kubectl describe crd attestationauthorities.kritis.grafeas.io

To list all attestation authorities:

kubectl get AttestationAuthority --all-namespaces

Here is example output:

NAMESPACE             NAME             AGE
qa                    qa-attestator    11h

example AttestionAuthority:

apiVersion: kritis.github.com/v1beta1
kind: AttestationAuthority
metadata:
    name: qa-attestator
    namespace: qa
spec:
    noteReference: v1alpha1/projects/image-attestor
    privateKeySecretName: foo
    publicKeyData: ...

Where “image-attestor” is the project for creating AttestationAuthority Notes.

In order to create notes, the service account gac-ca-admin must have containeranalysis.notes.attacher role on this project.

The Kubernetes secret foo must have data fields private and public which contain the gpg private and public key respectively.

publicKeyData is the base encoded PEM public key for the gpg secret.