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Version: 1.15

Testing for cluster operators

As a Kubernetes cluster operator, you'll want to perform testing for Kubewarden policies you want to use.

You'll have questions like:

  • What are the correct policy settings to get the validation/mutation outcome needed?
  • How can I be sure everything keeps working as expected when I:
    • upgrade the policy to a newer version?
    • add/change Kubernetes resources?
    • change the configuration parameters of the policy?
    • and so forth?

Kubewarden has a utility, kwctl, that permits testing of the policies outside of Kubernetes.

To use kwctl you invoke it with following inputs:

  1. A WebAssembly binary file URI of the policy to be run. The Kubewarden policy can load from the:
    • local filesystem file://
    • a HTTP(s) server https://
    • an OCI registry registry://.
  2. The admission request object to test. You give it with the --request-path argument. Use stdin by setting --request-path to -.
  3. The policy settings for runtime as an inline JSON via --settings-json flag. Or a JSON, or a YAML file, loaded from the file system via --settings-path.

After the test kwctl, prints the ValidationResponse object to the standard output.

You can download pre-built binaries of kwctl here.

A testing example​

This section describes how to test the psp-apparmor policy with different configurations and validation request objects.

Create AdmissionReview requests​

You need to create files holding the AdmissionReview objects to test the policy.

You can create a file named pod-req-no-specific-apparmor-profile.json with the following contents:

pod-req-no-specific-apparmor-profile.json
{
"uid": "1299d386-525b-4032-98ae-1949f69f9cfc",
"kind": {
"kind": "Pod",
"version": "v1"
},
"object": {
"metadata": {
"name": "no-apparmor"
},
"spec": {
"containers": [
{
"image": "nginx",
"name": "nginx"
}
]
}
},
"operation": "CREATE",
"requestKind": {"version": "v1", "kind": "Pod"},
"userInfo": {
"username": "alice",
"uid": "alice-uid",
"groups": ["system:authenticated"]
}
}

This request tries to create a Pod that doesn't specify any AppArmor profile to use. This is because it doesn't have an annotation with the container.apparmor.security.beta.kubernetes.io/<container-name> key.

You can create a file named pod-req-apparmor-unconfined.json with the following contents:

pod-req-apparmor-unconfined.json
{
"uid": "1299d386-525b-4032-98ae-1949f69f9cfc",
"kind": {
"kind": "Pod",
"version": "v1"
},
"object": {
"metadata": {
"name": "privileged-pod",
"annotations": {
"container.apparmor.security.beta.kubernetes.io/nginx": "unconfined"
}
},
"spec": {
"containers": [
{
"image": "nginx",
"name": "nginx"
}
]
}
},
"operation": "CREATE",
"requestKind": {"version": "v1", "kind": "Pod"},
"userInfo": {
"username": "alice",
"uid": "alice-uid",
"groups": ["system:authenticated"]
}
}

This request tries to create a Pod with a container called nginx running with the unconfined AppArmor profile. This is for tutorial purposes only. Running in unconfined mode is a bad security practice.

Now you can create a file named pod-req-apparmor-custom.json with the following contents:

pod-req-apparmor-custom.json
{
"uid": "1299d386-525b-4032-98ae-1949f69f9cfc",
"kind": {
"kind": "Pod",
"version": "v1"
},
"object": {
"metadata": {
"name": "privileged-pod",
"annotations": {
"container.apparmor.security.beta.kubernetes.io/nginx": "localhost/nginx-custom"
}
},
"spec": {
"containers": [
{
"image": "nginx",
"name": "nginx"
}
]
}
},
"operation": "CREATE",
"requestKind": {"version": "v1", "kind": "Pod"},
"userInfo": {
"username": "alice",
"uid": "alice-uid",
"groups": ["system:authenticated"]
}
}
note

These are all simplified AdmissionReview objects. Only the fields relevant to our testing of the policy are used.

Test the policy​

Now you can use kwctl to test the creation of a Pod not specifying an AppArmor profile:

$ kwctl run \
--request-path pod-req-no-specific-apparmor-profile.json \
registry://ghcr.io/kubewarden/policies/psp-apparmor:v0.1.4 \
| jq

The policy accepts the request and produces output like:

{
"uid": "1299d386-525b-4032-98ae-1949f69f9cfc",
"allowed": true
}

The policy rejects the creation of a Pod with an unconfined AppArmor profile:

$ kwctl run \
--request-path pod-req-apparmor-unconfined.json \
registry://ghcr.io/kubewarden/policies/psp-apparmor:v0.1.4 \
| jq
{
"uid": "1299d386-525b-4032-98ae-1949f69f9cfc",
"allowed": false,
"status": {
"message": "These AppArmor profiles are not allowed: [\"unconfined\"]"
}
}

On both occasions you ran the policy without providing any kind of setting. As the policy's documentation states, this results in preventing the usage of non-default profiles.

The Pod using a custom nginx profile gets rejected by the policy too:

$ kwctl run \
--request-path pod-req-apparmor-custom.json \
registry://ghcr.io/kubewarden/policies/psp-apparmor:v0.1.4 \
| jq
{
"uid": "1299d386-525b-4032-98ae-1949f69f9cfc",
"allowed": false,
"status": {
"message": "These AppArmor profiles are not allowed: [\"localhost/nginx-custom\"]"
}
}

You can change the default behavior, allowing chosen AppArmor profiles to be used:

$ kwctl run \
--request-path pod-req-apparmor-custom.json \
--settings-json '{"allowed_profiles": ["runtime/default", "localhost/nginx-custom"]}' \
registry://ghcr.io/kubewarden/policies/psp-apparmor:v0.1.4 \
| jq

Now the request succeeds:

{
"uid": "1299d386-525b-4032-98ae-1949f69f9cfc",
"allowed": true
}

Automation​

You can automate all these steps using bats.

You can write a series of tests and integrate their execution inside your existing CI and CD pipelines.

The commands can be "wrapped" into a bats test:

A batstest
@test "all is good" {
run kwctl run \
--request-path pod-req-no-specific-apparmor-profile.json \
registry://ghcr.io/kubewarden/policies/psp-apparmor:v0.1.4

# this prints the output when one the checks below fails
echo "output = ${output}"

# request accepted
[ $(expr "$output" : '.*"allowed":true.*') -ne 0 ]
}

@test "reject" {
run kwctl run \
--request-path pod-req-apparmor-custom.json \
registry://ghcr.io/kubewarden/policies/psp-apparmor:v0.1.4

# this prints the output when one the checks below fails
echo "output = ${output}"

# request rejected
[ $(expr "$output" : '.*"allowed":false.*') -ne 0 ]
}

If the bats code is in the file e2e.bats, you can run the test as:

$ bats e2e.bats
✓ all is good
✓ reject

2 tests, 0 failures

This section has more about writing end-to-end tests for your policies.