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A tiny tool for generating Kubernetes Admission Review Requests

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Kube Admission Review Generator

A tiny tool to generate Kubernetes Admission Review Requests, which can be utilized for Gatekeeper constraint/policy testing purposes (e.g., Gator test).

Admission Reviews in Kubernetes are part of the dynamic admission control system which are HTTP callbacks that receive admission requests and process them. They are an integral part of the Kubernetes API and are used to govern and enforce custom policies or modifications on objects.

Relevant links:

https://kubernetes.io/docs/reference/access-authn-authz/extensible-admission-controllers/

https://open-policy-agent.github.io/gatekeeper/website/docs/gator/

Installation

Binary file can be directly dowloaded in the release page here

OR：

Use go get to donwload and install the file if you have Golang env ready.

The tool will be installed in $GOPATH/bin directory.

go get -u "github.com/ArrisLee/admr-gen"

If you haven't add bin dir to your system $PATH, modify your bash profile by adding following lines:

export GOPATH=/your/own/go/path
export PATH=$PATH:$GOPATH/bin

This will allow you to use installed go binaries in terminal.

Parameters

  • --file - mandatory. Path to the input resource YAML file, e.g., ./deployment.yaml or ./pod.yaml.
  • --operation - optional. Expect operation value in admission review output, available values: create, update and delete. There will be an extra section in the generated yaml file called OldOBject when using update or delete operations.create operation will be applied if this parameter is missing.
  • --output - optional. Output format can be either json or yaml. yaml format will be applied if this parameter is missing.

Usage

Pass file and operation params to generate different types of kube admission review outputs:

admr-gen --file=pod.yaml --operation=create --output=yaml

Save output into a file if needed:

admr-gen --file=pod.yaml --operation=create --output=json > example.json

Example

Command

admr-gen --file=./pod_sample.yaml --operation=update
admr-gen --file=./pod_sample.yaml --operation=delete --output=json

Input file

apiVersion: v1
kind: Pod
metadata:
  name: allowed
  namespace: test
spec:
  serviceAccountName: test-user
  containers:
    - name: test
      image: openpolicyagent/opa:0.9.2
      args:
        - "run"
        - "--server"
        - "--addr=localhost:8080"
      resources:
        limits:
          cpu: "100m"
          memory: "30Mi"

Output YAML

apiVersion: admission.k8s.io/v1
kind: AdmissionReview
request:
  dryRun: true
  kind:
    group: ""
    kind: Pod
    version: v1
  object:
    apiVersion: v1
    kind: Pod
    metadata:
      name: allowed
      namespace: test
    spec:
      containers:
      - args:
        - run
        - --server
        - --addr=localhost:8080
        image: openpolicyagent/opa:0.9.2
        name: test
        resources:
          limits:
            cpu: 100m
            memory: 30Mi
      serviceAccountName: test-user
  oldObject:
    apiVersion: v1
    kind: Pod
    metadata:
      name: allowed-old
      namespace: test
    spec:
      containers:
      - args:
        - run
        - --server
        - --addr=localhost:8080
        image: openpolicyagent/opa:0.9.2
        name: test
        resources:
          limits:
            cpu: 100m
            memory: 30Mi
      serviceAccountName: test-user
  operation: UPDATE
  options: null
  requestKind:
    group: ""
    kind: Pod
    version: v1
  resource:
    group: ""
    resource: Pod
    version: v1
  uid: 8f248c68-639d-452f-a28f-3f331b001821
  userInfo:
    uid: 502ab568-4acd-4776-8326-b10b5414eb6b
    username: fake-k8s-admin-review

Output JSON

{
    "kind": "AdmissionReview",
    "apiVersion": "admission.k8s.io/v1",
    "request": {
        "uid":