Quick start
The Kubewarden stack comprises:
-
Some
ClusterAdmissionPolicyA ClusterAdmissionPolicy defines how policies evaluate requests. Glossaryresources: this is how policies are defined for Kubernetes clusters. -
Some
PolicyServerA PolicyServer validates incoming requests by executing Kubewarden policies against requests. Glossaryresources: representing a deployment of a KubewardenPolicyServer
. The KubewardenPolicyServer
loads and evaluates your administrator's policies. -
Some
AdmissionPolicyA namespace-wide resource. The policy processes only requests targeting the namespace where the AdmissionPolicy is defined. Glossaryresources: policies for a defined namespace. -
A deployment of a
kubewarden-controller
: this controller monitors the [[< cluster-admission-policy >]] resources and interacts with the Kubewarden [[< policy-server >]] components.
Kubewarden describes its Kubernetes Custom Resource Definitions (CRDs) here.
Kubewarden CRDs mentioned in this tutorial and in the whole documentation have short names, which are easier to use. These are the short names for all the CRDs:
Resource | shortName |
---|---|
AdmissionPolicies | ap |
ClusterAdmissionPolicies | cap |
AdmissionPolicyGroups | apg |
ClusterAdmissionPolicyGroups | capg |
PolicyServers | ps |
Installation​
You can retrieve Kubewarden policies from the GitHub container registry at https://ghcr.io. You need authentication to use the repository with the Kubewarden CLI, a GitHub personal access token (PAT). Their documentation guides you through creating one if you haven't already done so. Then you authenticate with a command like:
echo $PAT | docker login ghcr.io --username <my-gh-username> --password-stdin
Deploy the Kubewarden stack using helm
charts as follows:
helm repo add kubewarden https://charts.kubewarden.io
helm repo update kubewarden
Install the following Helm charts inside the kubewarden
namespace in your
Kubernetes cluster:
-
kubewarden-crds
, which registers theClusterAdmissionPolicyA ClusterAdmissionPolicy defines how policies evaluate requests. Glossary,AdmissionPolicyA namespace-wide resource. The policy processes only requests targeting the namespace where the AdmissionPolicy is defined. GlossaryandPolicyServerA PolicyServer validates incoming requests by executing Kubewarden policies against requests. GlossaryCustom Resource Definitions. Also, thePolicyReportA PolicyReport and a ClusterPolicyReport store results of policy scans. Which one is used depends on the scope of the resource. GlossaryCustom Resource Definitions used by the audit scanner. -
kubewarden-controller
, which installs the Kubewarden controller and the audit scannernoteIf you need to disable the audit scanner component check the audit scanner installation documentation page.
-
kubewarden-defaults
, which creates aPolicyServer
resource nameddefault
. It can also install a set of recommended policies to secure your cluster by enforcing some well known best practices.
helm install --wait -n kubewarden --create-namespace kubewarden-crds kubewarden/kubewarden-crds
helm install --wait -n kubewarden kubewarden-controller kubewarden/kubewarden-controller
helm install --wait -n kubewarden kubewarden-defaults kubewarden/kubewarden-defaults
Since
v0.4.0
,
a PolicyServer
resource named default
will not be created using the
kubewarden-controller
chart. Now a Helm chart called kubewarden-defaults
,
installs the default policy server.
This means that if you aren't using the latest version of the
kubewarden-controller
and are trying to upgrade or delete, your default
policy server won't be upgraded or deleted. So, you might run into issues if
you try to install the kubewarden-defaults
with some conflicting information,
for example, the same policy server name. To be able to take advantage of
future upgrades in the kubewarden-defaults
Helm chart remove the existing
PolicyServer
resource created by the kubewarden-controller
before
installing the new chart. Now you can update your policy server using Helm
upgrades without resource conflicts. When you remove the PolicyServer
, all
the policies bound to it will be removed as well.
The default configuration values are sufficient for most deployments. The documentation describes all the options.
Main components​
Kubewarden has three main components which you will interact with:
- The PolicyServerA PolicyServer validates incoming requests by executing Kubewarden policies against requests. Glossary
- The ClusterAdmissionPolicyA ClusterAdmissionPolicy defines how policies evaluate requests. Glossary
- The AdmissionPolicyA namespace-wide resource. The policy processes only requests targeting the namespace where the AdmissionPolicy is defined. Glossary
PolicyServer
​
The kubewarden-controller
manages a Kubewarden PolicyServer
.
You can deploy multiple
A PolicyServer
validates incoming requests by executing Kubewarden policies against them.
This is the default PolicyServer
configuration:
apiVersion: policies.kubewarden.io/v1
kind: PolicyServer
metadata:
name: reserved-instance-for-tenant-a
spec:
image: ghcr.io/kubewarden/policy-server:v1.3.0
replicas: 2
serviceAccountName: ~
env:
- name: KUBEWARDEN_LOG_LEVEL
value: debug
Check the latest released PolicyServer
version and change the tag to match.
Overview of the attributes of the PolicyServer
resource:
Required | Placeholder | Description |
---|---|---|
Y | image | The name of the container image |
Y | replicas | The number of desired instances |
N | serviceAccountName | The name of the ServiceAccount to use for the PolicyServer deployment. If no value is provided, the default ServiceAccount from the namespace, where the kubewarden-controller is installed, is used |
N | env | The list of environment variables |
N | annotations | The list of annotations |
Changing any of these attributes causes a PolicyServer
deployment with the new configuration.
ClusterAdmissionPolicy​
The
Enforcing policies is the most common operation which a Kubernetes
administrator performs. You can declare as many policies as you want, each
targets one or more Kubernetes resources (that is, pods
, Custom Resource
and others). You also specify the type of operations applied to targeted
resources. The operations available are CREATE
, UPDATE
, DELETE
and
CONNECT
.
Default
apiVersion: policies.kubewarden.io/v1
kind: ClusterAdmissionPolicy
metadata:
name: psp-capabilities
spec:
policyServer: reserved-instance-for-tenant-a
module: registry://ghcr.io/kubewarden/policies/psp-capabilities:v0.1.9
rules:
- apiGroups: [""]
apiVersions: ["v1"]
resources: ["pods"]
operations:
- CREATE
- UPDATE
mutating: true
settings:
allowed_capabilities:
- CHOWN
required_drop_capabilities:
- NET_ADMIN
Overview of the attributes of the
Required | Placeholder | Description |
---|---|---|
N | policy-server | Identifies an existing PolicyServer object. The policy will be served only by this PolicyServer instance. The policy server named default serves a ClusterAdmissionPolicyA ClusterAdmissionPolicy defines how policies evaluate requests. Glossary without an explicit PolicyServer . |
Y | module | The location of the Kubewarden policy. Kubewarden permits the following schemes: |
N | - registry : The policy is downloaded from an OCI artifacts compliant container registry. Example: registry://<OCI registry/policy URL> . | |
N | - http , https : The policy is downloaded from a regular HTTP(s) server. Example: https://<website/policy URL> . | |
N | - file : The policy is loaded from a file in the computer file system. Example: file:///<policy WASM binary full path> . | |
Y | resources | The Kubernetes resources evaluated by the policy. |
Y | operations | What operations for the previously given types to forward to this admission policy by the API server for evaluation. |
Y | mutating | A boolean value to be set to true for policies that can mutate incoming requests. |
N | settings | A free-form object that contains the policy configuration values. |
N | failurePolicy | The action to take if the request evaluated by a policy results in an error. Permitted options: |
N | - Ignore : ignore an error calling the webhook, and the API request continues. | |
N | - Fail : an error calling the webhook causes the admission to fail and the API request is rejected. |
The
*
webhook scope
. This means that registered webhooks forward all requests
matching the given resources
and operations
, either namespaced or
cluster-wide resources.AdmissionPolicy​
kubernetes.io/metadata.name
label, introduced in
Kubernetes 1.21.0The complete documentation of these Custom Resources can be found here or on docs.crds.dev.
Example: Enforce your first policy​
We will use the pod-privileged
policy.
We want to prevent the creation of privileged containers inside our Kubernetes cluster by enforcing this policy.
Let's define a
kubectl apply -f - <<EOF
apiVersion: policies.kubewarden.io/v1
kind: ClusterAdmissionPolicy
metadata:
name: privileged-pods
spec:
module: registry://ghcr.io/kubewarden/policies/pod-privileged:v0.2.2
rules:
- apiGroups: [""]
apiVersions: ["v1"]
resources: ["pods"]
operations:
- CREATE
- UPDATE
mutating: false
EOF
This produces the following output:
clusteradmissionpolicy.policies.kubewarden.io/privileged-pods created
When a
pending
, and it forces a rollout of the targeted PolicyServer
. In our
example, it's the PolicyServer
named default
. You can monitor the rollout
by running the following command:
kubectl get clusteradmissionpolicy.policies.kubewarden.io/privileged-pods
You should see the following output:
NAME POLICY SERVER MUTATING STATUS
privileged-pods default false pending
Once the new policy is ready to be served, the kubewarden-controller
will
register a
ValidatingWebhookConfiguration
object.
The
active
once the
Deployment completes for every PolicyServer
instance.
Show AdmissionReview
. Glossarykubectl get validatingwebhookconfigurations.admissionregistration.k8s.io -l kubewarden
You should see the following output:
NAME WEBHOOKS AGE
clusterwide-privileged-pods 1 9s
Once the
AdmissionReview
. GlossaryFirst, you can create a Pod with a Container not in privileged
mode:
kubectl apply -f - <<EOF
apiVersion: v1
kind: Pod
metadata:
name: unprivileged-pod
spec:
containers:
- name: nginx
image: nginx:latest
EOF
This produces the following output:
pod/unprivileged-pod created
The Pod is successfully created.
Now, you can create a Pod with at least one Container privileged
flag:
kubectl apply -f - <<EOF
apiVersion: v1
kind: Pod
metadata:
name: privileged-pod
spec:
containers:
- name: nginx
image: nginx:latest
securityContext:
privileged: true
EOF
The policy denies creation of the Pod and you should see the following message:
Error from server: error when creating "STDIN": admission webhook "clusterwide-privileged-pods.kubewarden.admission" denied the request: Privileged container is not allowed
Both examples didn't define a namespace
, which means the default
namespace
was the target. However, as you could see in the second example, the policy is
still applied. As stated previously, this is due to the scope being
cluster-wide and not targeting a specific namespace.
Uninstall​
You can remove the resources created by uninstalling the helm
charts as
follows:
helm uninstall --namespace kubewarden kubewarden-defaults
helm uninstall --namespace kubewarden kubewarden-controller
helm uninstall --namespace kubewarden kubewarden-crds
After removal of the helm
charts remove the Kubernetes namespace that
used to deploy the Kubewarden stack:
kubectl delete namespace kubewarden
Kubewarden contains a helm pre-delete hook that removes all PolicyServer
s and
kubewarden-controller
s. Then the kubewarden-controller
deletes all
resources, so it's important that kubewarden-controller
is running when helm
uninstall executes.
Kubewarden deletes
AdmissionReview
. GlossaryAdmissionReview
. Glossarykubectl get validatingwebhookconfigurations.admissionregistration.k8s.io -l "kubewarden"
kubectl get mutatingwebhookconfigurations.admissionregistration.k8s.io -l "kubewarden"
If these resources aren't automatically removed, remove them manually using the following command:
kubectl delete -l "kubewarden" validatingwebhookconfigurations.admissionregistration.k8s.io
kubectl delete -l "kubewarden" mutatingwebhookconfigurations.admissionregistration.k8s.io
Wrapping up​
kubewarden-controller
module automatically takes care of
the configuration for the rest of the resources needed to run the policies.
What's next?​
Now, you are ready to deploy Kubewarden! Have a look at the policies on artifacthub.io, on GitHub, or reuse existing Rego policies as shown in the following chapters.