Datree Admission Webhook

Overview

Datree offers cluster integration that allows you to validate your resources against your configured policy upon pushing them into a cluster, by using an admission webhook.

The webhook will catch create, apply and edit operations and initiate a policy check against the configs associated with each operation. If any misconfigurations are found, the webhook will reject the operation, and display a detailed output with instructions on how to resolve each misconfiguration.

Webhook validation triggers

K8s use different abstractions to simplify and automate complex processes. For example, when explicitly applying an object type “Deployment”, under the hood, K8s will “translate” this object into implicit objects of type “Pod.”

When installed on your cluster, other policy enforcement tools will validate both explicit and implicit objects. This approach may create a lot of noise and false positive failures since it will cause the webhook to validate objects that the users don’t manage and, in some cases, are not even accessible.

To avoid such issues, we decided to define the specific operations that the admission webhook should validate:

• Kubectl - validate objects that were created or updated using kubectl create, edit, and apply commands. Objects that were implicitly created (e.g., pods created via deployment) are ignored since the webhook validates the deployment that generated them and is accessible to the user.
• Gitops CD tools - validate objects that were explicitly created and distinguish them from other objects (custom resources) that were implicitly created during the installation and are required for the ongoing operation of these tools (e.g., ArgoCD, FluxCD, etc.)

Installation

The webhook officially supports Kubernetes version 1.19 and higher, and has been tested with EKS.

Prerequisites
The following applications need to be installed on the machine:

• kubectl
• openssl - required for creating a certificate authority (CA).
• curl

Installation
Simply copy the following command and run it in your terminal:

bash <(curl https://get.datree.io/admission-webhook)

[NOTE] the link above will prompt you to enter your Datree token during installation.
To install without a prompt, you can provide your token as part of the installation command, by running this in your terminal:

DATREE_TOKEN=[your-token] bash <(curl https://get.datree.io/admission-webhook)

Usage

Once the webhook is installed, every hooked operation will trigger a Datree policy check.
If any misconfigurations are found, the following output will be displayed:

If no misconfigurations are found, the resource will be applied/updated normally.

Behavior

The webhook’s behavior is configured within the webhook-server resource.
The following settings are supported:

Setting	Values	Description
DATREE_TOKEN		Your Datree token, see our docs for instructions on how to obtain it
DATREE_POLICY	e.g. "Argo", "NSA"	The name of the desired Datree policy to run
DATREE_VERBOSE	true, false	Display 'How to Fix' link for failed rules in output
DATREE_NO_RECORD	true, false	Don’t send policy checks metadata to the backend
DATREE_OUTPUT	json, yaml, xml, JUnit	Output the policy check results in the requested format

To change the behavior:

1. Create a YAML file in your repository with this content:

spec:
  template:
    spec:
      containers:
        - name: server
          env:
            - name: DATREE_POLICY
              value: ""
            - name: DATREE_VERBOSE
              value: ""
            - name: DATREE_OUTPUT
              value: ""
            - name: DATREE_NO_RECORD
              value: ""

2. Change the values of your settings as you desire.
3. Run the following command to apply your changes to the webhook resource:

kubectl patch deployment webhook-server -n datree --patch-file /path/to/patch/file.yaml

🤫 Since your token is sensitive and you would not want to keep it in your repository, we recommend to set/change it by running a separate kubectl patch command:

kubectl patch deployment webhook-server -n datree -p '
spec:
  template:
    spec:
      containers:
        - name: server
          env:
            - name: DATREE_TOKEN
              value: "<your-token>"'

Simply replace <your-token> with your actual token, then copy the entire command and run it in your terminal.

Uninstallation

To uninstall the webhook, copy the following command and run it in your terminal:

bash <(curl https://get.datree.io/admission-webhook-uninstall)

Local development

To run the webhook locally (in development), view our developer guide.