kubernetes-ldap

Lightweight Directory Access Protocol (LDAP) for Kubernetes™

Getting Started

This project provides an LDAP authentication webhook for Kubernetes. The current implementation exposes two endpoints:

• /authenticate: Handles token authentication requests coming from Kubernetes
• /ldapAuth: Issues token to be used when interacting with the Kubernetes API

Pre-requisites

• Certificate and corresponding private key for the webhook server
• Certificate and corresponding private key for the Kubernetes webhook client

Starting the webhook server

Run the following to start the server

kubernetes-ldap --ldap-host ldap.example.com \
    --ldap-base-dn "DC=example,DC=com" \
    --tls-cert-file pathToCert \
    --tls-private-key-file pathToKey \
    --ldap-user-attribute userPrincipalName

Configuring the Kubernetes Webhook

Create a yaml file to define the webhook:

# clusters refers to the remote service.
clusters:
  - name: ldap-auth-webhook
    cluster:
      certificate-authority: ~/ldap.example.com.cert      # CA for verifying the remote service.
      server: https://ldap-webhook:4000/authenticate # URL of remote service to query. Must use 'https'.

# users refers to the API Server's webhook configuration.
users:
  - name: ldap-auth-webhook-client
    user:
      client-certificate: ~/k8s-webhook-client.cert # cert for the webhook plugin to use
      client-key: ~/k8s-webhook-client.key          # key matching the cert

# kubeconfig files require a context. Provide one for the API Server.
current-context: webhook
contexts:
- context:
    cluster: ldap-auth-webhook
    user: ldap-auth-webhook-client
  name: webhook

Set the following flags to configure the authentication webhook when starting the Kubernetes API Server:

--authentication-token-webhook-cache-ttl=30m0s # Set appropriate cache TTL 
--authentication-token-webhook-config-file=/root/webhook-config.yaml # Path to file where the webhook is defined

Authenticating and using kubectl

Once the webhook and API servers are running, we are ready to authenticate using LDAP.

1. Obtain an authentication token from the webhook server

AUTH_TOKEN=$(curl https://ldap-webhook:4000/ldapAuth --user alice@example.com:password)

2. Store the auth token in kubectl's configuration

kubectl config set-credentials alice --token=$AUTH_TOKEN

3. Start using kubectl with the authenticated user

kubectl -s="https://localhost:6443" --user=alice get nodes