Gardenlogin

gardenlogins get-client-certificate command can be used as a kubectl credential plugin. It fetches the cluster-admin credentials from the API introduced with GEP-16. See more details under Authentication Flow

With GEP-16, users are able to generate kubeconfigs for Shoot clusters with short-lived certificates, to access the cluster as cluster-admin.

Installation

Install the latest release from Homebrew, Chocolatey or GitHub Releases.

Install using Package Managers

# Homebrew (macOS and Linux)
brew install gardener/tap/gardenlogin

# Chocolatey (Windows)
choco install gardenlogin

Install using Nix

Nix with Flakes (prerequisite: Nix, the package manager):

# Nix (macOS, Linux, and Windows)

# development version
nix profile install github:gardener/gardenlogin
# or release <version>
nix profile install github:gardener/gardenlogin/<version>

#check installation
nix profile list | grep gardenlogin

# optionally, open a new shell and verify that cmd completion works
gardenlogin --help
kubectl gardenlogin --help

Install from Github Release

If you install via GitHub releases, you need to put the gardenlogin binary on your path under the name kubectl-gardenlogin so that the kubectl plugin mechanism can find it when you invoke kubectl gardenlogin. The other install methods do this for you.

# Example for macOS

# set operating system and architecture
os=darwin # choose between darwin, linux, windows
arch=amd64

# Get latest version. Alternatively set your desired version
version=$(curl -s https://raw.githubusercontent.com/gardener/gardenlogin/master/LATEST)

# Download gardenlogin
curl -LO "https://github.com/gardener/gardenlogin/releases/download/${version}/gardenlogin_${os}_${arch}"

# Make the gardenlogin binary executable
chmod +x "./gardenlogin_${os}_${arch}"

# Move the binary in to your PATH
sudo mv "./gardenlogin_${os}_${arch}" /usr/local/bin/gardenlogin

# create kubectl-gardenlogin symlink
ln -s /usr/local/bin/gardenlogin /usr/local/bin/kubectl-gardenlogin

Configure Gardenlogin

gardenlogin requires a configuration file. The default location is in ~/.garden/gardenlogin.yaml.

If no configuration file is found, it falls back to the gardenctl-v2 configuration file (~/.garden/gardenctl-v2.yaml) which shares the same configuration properties.

Hint: If you intend to use both gardenlogin and gardenctl-v2, it is recommended to store the configuration file in ~/.garden/gardenctl-v2.yaml. This allows both applications to share a single configuration.

Example Config

gardens:
- identity: landscape-dev # Unique identity of the garden cluster. See cluster-identity ConfigMap in kube-system namespace of the garden cluster
  kubeconfig: ~/path/to/garden-cluster/kubeconfig.yaml
#  context: different-context # Overrides the current-context of the garden cluster kubeconfig  

Config Path Overwrite

• The gardenlogin config path can be overwritten with the environment variable GL_HOME.
• The gardenlogin config name can be overwritten with the environment variable GL_CONFIG_NAME.

export GL_HOME=/alternate/garden/config/dir
export GL_CONFIG_NAME=myconfig # without extension!
# config is expected to be under /alternate/garden/config/dir/myconfig.yaml

Usage

An example kubeconfig for a shoot cluster looks like the following:

# supported with kubectl version v1.20.0 onwards
apiVersion: v1
kind: Config
clusters:
- name: shoot--myproject--mycluster
  cluster:
    server: https://api.mycluster.myproject.example.com
    certificate-authority-data: LS0tLS1CRUdJTiBDRVJUSUZJQ0FURS0tLS0tCi4uLgotLS0tLUVORCBDRVJUSUZJQ0FURS0tLS0t
    extensions:
    - name: client.authentication.k8s.io/exec
      extension:
        shootRef:
          namespace: garden-myproject
          name: mycluster
        gardenClusterIdentity: landscape-dev # must match with the garden cluster identity from the config
contexts:
- name: shoot--myproject--mycluster
  context:
    cluster: shoot--myproject--mycluster
    user: shoot--myproject--mycluster
current-context: shoot--myproject--mycluster
users:
- name: shoot--myproject--mycluster
  user:
    exec:
      apiVersion: client.authentication.k8s.io/v1
      provideClusterInfo: true
      command: kubectl
      args:
      - gardenlogin
      - get-client-certificate

An example kubeconfig supporting kubectl version v1.11.0 onwards can be found under example/02-kubeconfig.yaml.

Authentication Flow

The following describes the flow to authenticate against a Shoot cluster as cluster admin:

1. The user would either download the Shoot cluster kubeconfig
   • using the gardener/dashboard (TODO)
   • by targeting the cluster with gardenctl
   • or using gardenctl kubeconfig --raw --garden landscape-dev --project my-project --shoot my-shoot to print the kubeconfig for the respective target cluster
2. kubectl is then configured to use the downloaded kubeconfig for the shoot cluster
3. A kubectl command is executed, e.g. kubectl get namespaces
4. The gardenlogin credential plugin is called to print the ExecCredential to stdout, see input and output formats for more information.
5. In case a valid credential is already cached locally it is returned directly. Otherwise, a new credential has to be requested
6. According to the garden cluster identity under clusters[].cluster.extensions[].extension.gardenClusterIdentity, the gardenlogin plugin searches a matching garden cluster in its configuration file (gardenClusters[].clusterIdentity) to get the kubeconfig of the garden cluster
7. The gardenlogin plugin calls shoots/adminkubeconfig resource with an AdminKubeConfigRequest for the Shoot cluster referenced under clusters[].cluster.extensions[].extension.shootRef
8. The gardenlogin plugin takes the x509 client certificate from the returned AdminKubeConfigRequest under status.kubeconfig and prints it as ExecCredential to stdout