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Dynamic Kubernetes Cluster Registration
Register and unregister Kubernetes clusters without restarting a Teleport Kubernetes Service instance.

With dynamic Kubernetes cluster registration, you can manage the Kubernetes clusters connected to your Teleport cluster without needing to modify the configuration file of an individual Kubernetes Service instance.

Dynamic Kubernetes cluster registration is useful when you have deployed multiple Kubernetes Service instances or need to regularly reconfigure access to Kubernetes clusters in your infrastructure.

In this guide, we will show you how to set up dynamic Kubernetes cluster registration, then create, list, update, and delete Kubernetes clusters via tctl.

Prerequisites

(!docs/pages/includes/edition-prereqs-tabs.mdx!)

  • A Linux host where you will install the Teleport Kubernetes Service.

    Our teleport-kube-agent Helm chart does not support dynamic Kubernetes cluster registration.

  • A Kubernetes cluster to join to your Teleport cluster. You must have permissions to create namespaces, secrets, service accounts, cluster roles, and cluster role bindings in the cluster.

  • (!docs/pages/includes/tctl.mdx!)

Step 1/3. Set up the Teleport Kubernetes Service

The Teleport Kubernetes Service proxies traffic from Teleport users to a Kubernetes API server so you can take advantage of passwordless authentication, role-based access controls, audit logging, and other Teleport features in order to manage access to Kubernetes.

In this step, you will install the Teleport Kubernetes Service on a Linux host and configure it to access any Kubernetes cluster you register with your Teleport cluster.

Get a join token

Establish trust between your Teleport cluster and your new Kubernetes Service instance by creating a join token:

$ tctl tokens add --type=kube --ttl=1h --format=text
(=presets.tokens.first=)

Copy the token and keep it somewhere safe so you can use it when running the Teleport Kubernetes Service.

Install the Teleport Kubernetes Service

Install the Teleport Kubernetes Service on your Linux host:

(!docs/pages/includes/install-linux.mdx!)

Configure the Teleport Kubernetes Service

On the host where you will run the Teleport Kubernetes Service, run the following command to create a base configuration for your Teleport instance, assigning to the host and port of your Teleport Proxy Service or Teleport Cloud tenant and to the join token we created earlier:

$ sudo teleport configure \
--proxy=<Var name="example.teleport.sh:443" /> \
--roles=kube \
--token=<Var name="join-token" /> \
-o file

Edit your configuration file at /etc/teleport.yaml to include the following:

kubernetes_service:
  enabled: "yes"
  resources:
  - labels:
      "*": "*"

This configuration enables your Kubernetes Service instance to connect to any Kubernetes clusters you register with your Teleport cluster. This is because the resources[0].labels field includes the wildcard pattern ("*": "*"), which allows this Kubernetes Service instance to connect to Kubernetes cluster resources with any label key or value.

You can configure a Kubernetes Service instance to watch for a subset of Kubernetes clusters by including specific label keys and values instead of wildcard characters:

resources:
- labels:
    "env": "prod"
    "region": "us-east-2"
- labels:
    "env": "test"
    "region": "us-west-1"

For the Kubernetes Service to register a cluster, any of the items in resources must match the cluster's labels. For an item in resources to match, all of the labels entries within that item must match the cluster's labels.

For example, a cluster with the labels env:prod and region:us-west-1 would not match the configuration above, since it only matches the env:prod label in the first resources item and the region:us-west-1 label in the second resources item.

However, a cluster with env:test and region:us-west-1 would match, since it matches both labels given in the second resources item.

When you create dynamic Kubernetes cluster resources later in this guide, you can assign them labels to ensure that only specific Kubernetes Service instances will watch for them.

Run the Teleport Kubernetes Service

(!docs/pages/includes/start-teleport.mdx service="the Teleport Kubernetes Service"!)

Step 2/3. Authorize your user

To enable dynamic Kubernetes cluster registration in Teleport, you will need to authorize your user to access the Kubernetes clusters you want to register with Teleport. We will configure this access in this step, both in Teleport and on your Kubernetes cluster.

Allow access to your Kubernetes cluster

Ensure that you are in the correct Kubernetes context for the cluster you would like to enable access to.

Retrieve all available contexts:

$ kubectl config get-contexts

Switch to your context, replacing CONTEXT_NAME with the name of your chosen context:

$ kubectl config use-context CONTEXT_NAME
Switched to context CONTEXT_NAME

(!docs/pages/includes/kubernetes-access/rbac.mdx!)

Authorize your user to manage Kubernetes clusters

Teleport tracks Kubernetes clusters in your infrastructure via dynamic kube_cluster resources. To manage access to Kubernetes clusters with Teleport, your user will need permissions to manage these resources.

In the previous section, you authorized your user to access all Kubernetes clusters registered in your Teleport cluster. Now that you can access these clusters, create a role that enables you to manage them.

Create a role definition called kube-manager.yaml with the following content:

kind: role
metadata:
  name: kube-manager
spec:
  allow:
    rules:
    - resources:
      - kube_cluster
      verbs:
      - list
      - create
      - read
      - update
      - delete
version: v5

Create the role:

$ tctl create -f kube-manager.yaml

(!docs/pages/includes/create-role-using-web.mdx!)

(!docs/pages/includes/add-role-to-user.mdx role="kube-manager"!)

Step 3/3. Manage dynamic Kubernetes cluster resources

Now that your Teleport user has permissions to manage Kubernetes cluster resources, we will show you how to create, list, update, and delete them.

Create a kubeconfig

In this section, you will create a Kubernetes Config resource, or kubeconfig, that your Teleport cluster will use to authenticate to your Kubernetes cluster.

When you signed into Teleport earlier in this guide, tsh may have changed your Kubernetes context to one based on your Teleport cluster, so make sure you update your Kubernetes context to match the cluster you would like to connect to Teleport:

$ kubectl config get-contexts
# Assign CONTEXT_NAME to your chosen context
$ kubectl config use-context CONTEXT_NAME

On your workstation, download Teleport's get-kubeconfig.sh script, which you will use to generate the kubeconfig:

$ curl -OL \
https://raw.githubusercontent.com/gravitational/teleport/v(=teleport.version=)/examples/k8s-auth/get-kubeconfig.sh

The script creates a service account for the Teleport Kubernetes Service that can get Kubernetes pods as well as impersonate users, groups, and other service accounts. The Teleport Kubernetes Service uses this service account to manage access to resources in your Kubernetes cluster. The script also ensures that there is a Kubernetes Secret in your cluster to store service account credentials.

get-kubeconfig.sh creates a namespace called teleport for the resources it deploys, though you can choose a different name by assigning the TELEPORT_NAMESPACE environment variable in the shell where you run the script.

After creating resources, get-kubeconfig.sh writes a new kubeconfig to a file called kubeconfig in the directory where you run the script.

Run the get-kubeconfig.sh script:

$ bash get-kubeconfig.sh

The script is successful if you see this message:

Done!

Ignore the script's instructions to copy the generated kubeconfig file to the Teleport Proxy Service. In the next section, we will show you how to use the kubeconfig file when creating a dynamic kube_cluster resource.

Create a Kubernetes cluster resource

Define a kube_cluster resource with the following content in a file called kube_cluster.yaml:

kind: kube_cluster
version: v3
metadata:
  name: mycluster
spec:
  kubeconfig: |

The spec.kubeconfig field in the snippet above begins a multi-line string. Below, you will include the contents of the kubeconfig file as its value.

Since spec.kubeconfig must be a base64-encoded string, convert the kubeconfig file to base64, then indent it and add it to the kube_cluster.yaml resource definition using the following command:

$ printf "    %s" $(cat kubeconfig | base64) >> kube_cluster.yaml

You can add labels to the kube_cluster resource, allowing you to manage access to specific clusters from your Teleport roles or Kubernetes Service instances.

Labels can either be static or dynamic. Static labels are key/value pairs. This example defines the env=prod and team=dev labels:

kind: kube_cluster
version: v3
metadata:
  name: mycluster
  labels:
    env: prod
    team: dev
spec:
  kubeconfig: KUBECONFIG

You can also add dynamic labels, which define shell commands that a Kubernetes Service instance will execute in order to generate labels. To do so, edit the spec.dynamic_labels field of a kube_cluster resource.

This example runs the python3 get_region.py command to fetch the region in which the Kubernetes Service is deployed and assign the result to the region key:

kind: kube_cluster
version: v3
metadata:
  name: mycluster
spec:
  kubeconfig: KUBECONFIG
  dynamic_labels:
    region:
      period: "24h"
      command: ["python3", "get_region.py"]

When defining a dynamic label, the key within the spec.dynamic_labels field behaves the same as keys within the metadata.labels field, indicating the key of the label.

The Kubernetes Service obtains a value for that key by running the command given in command every period. command is an array of strings, where the first element indicates the command to execute and each subsequent element indicates an argument.

period is a Go duration string, which includes a number and a unit of time. Supported units are ns, us (or µs), ms, s, m, and h. The example above configures the Kubernetes Service to run the command every day.

To create the kube_cluster resource, run the following command:

$ tctl create kube_cluster.yaml
kubernetes cluster "mycluster" has been created

Access your new Kubernetes cluster

Instances of the Teleport Kubernetes Service watch for newly created or updated kube_cluster resources. When you create the kube_cluster resource, any Kubernetes Service instances you have configured to track that cluster's labels will register that cluster and enable access to it via Teleport.

As a result, you should now see the cluster you registered above when you run tsh kube ls:

$ tsh kube ls
 Kube Cluster Name Labels                      Selected
 ----------------- --------------------------- --------
 mycluster         teleport.dev/origin=dynamic

The teleport.dev/origin=dynamic label indicates that the cluster was registered dynamically.

You can also log in to the cluster you just registered:

$ tsh kube login mycluster
Logged into kubernetes cluster "mycluster". Try 'kubectl version' to test the
connection.

List Kubernetes cluster resources

You can list kube_cluster resources with the following command:

$ tctl get kube_clusters

Update a Kubernetes cluster resource

To update the kube_cluster resource you created earlier, execute the following command to open the resource as it exists on the Auth Service's backend in your text editor:

$ tctl edit kube_clusters/mycluster

Edit the resource to add a label to your kube_cluster:

  kind: kube_cluster
  metadata:
    id: 9999999999999999999
    labels:
      teleport.dev/origin: dynamic
+     env: test
    name: mycluster
  spec:
    aws: {}
    azure: {}
    kubeconfig: KUBECONFIG
  version: v3

Save and close the file in your editor to apply your changes.

You should now see the updated labels:

$ tsh kube ls
 Kube Cluster Name Labels                               Selected
 ----------------- ------------------------------------ --------
 mycluster         env=test teleport.dev/origin=dynamic *

If the updated kube_cluster resource's labels no longer match the ones a Teleport Kubernetes Service instance is configured to watch, the instance will unregister and stop proxying the Kubernetes cluster.

Delete Kubernetes cluster resources

To delete the kube_cluster resource you created earlier, run the following command:

$ tctl rm kube_clusters/mycluster
kubernetes cluster "mycluster" has been deleted

This will unregister the Kubernetes cluster from Teleport:

$ tsh kube ls
Kube Cluster Name Labels Selected
----------------- ------ --------

Next steps

In this guide, we showed you how to manage kube_cluster resources using tctl. If you are interested in other ways you can manage access to Kubernetes clusters via Teleport, check out the following guides: