Dedicated K8s Service Accounts

Prerequisites

  • Akeyless Gateway with network access to Kubernetes cluster.

  • Kubernetes version 1.21 and higher.

Dedicated Service Account

This flow describes the creation of a dedicated K8s Service Account which will work based on token projection.

For a Rancher cluster, please create your Rancher API Key and refer to this section to extract your Rancher server CA certificate.

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Note:

To enable and use token request projection on a self-managed cluster, you must specify each of the following command line arguments to kube-apiserver:
--service-account-issuer
--service-account-key-file
--service-account-signing-key-file
--api-audiences

For more details, check out the minikube configuration example at the end of this page.

  1. Create a Service Account named gateway-token-reviewer with permission to access token review API. This Service Account will be used to validate a Kubernetes JWT coming from a pod that will try to authenticate to Akeyless.
cat << EOF > akl_gw_token_reviewer.yaml 
apiVersion: v1
kind: ServiceAccount
metadata:
  name: gateway-token-reviewer
  namespace: default
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: role-tokenreview-binding
  namespace: default
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: system:auth-delegator
subjects:
- kind: ServiceAccount
  name: gateway-token-reviewer
  namespace: default 
EOF

Apply:

kubectl apply -f akl_gw_token_reviewer.yaml

Bearer Token Extraction for K8s Server Version 1.23 or Older

  1. Extract the gateway-token-reviewer Service Account secret name:
GW_SA_NAME=$(kubectl get sa gateway-token-reviewer \
    --output jsonpath="{.secrets[*]['name']}")
  1. Extract the Service Account JWT Bearer Token (Kubernetes Server Version <= 1.23):
SA_JWT_TOKEN=$(kubectl get secret $GW_SA_NAME \
    --output 'go-template={{ .data.token | base64decode }}')

Bearer Token Extraction for K8s Server Version 1.24 or Higher

K8s won’t generate Secrets automatically for ServiceAccounts, to get your Service Account token, run the following commands instead:

  1. Create the long-lived service account secret (Kubernetes Server Version >= 1.24):
cat <<EOF > akl_gw_token_reviewer_token.yaml 
apiVersion: v1
kind: Secret
metadata:
  name: gateway-token-reviewer-token
  namespace: default
  annotations:
    kubernetes.io/service-account.name: gateway-token-reviewer
type: kubernetes.io/service-account-token
EOF
kubectl apply -f akl_gw_token_reviewer_token.yaml
  1. Extract the service account JWT Bearer Token (Kubernetes Server Version >= 1.24):
SA_JWT_TOKEN=$(kubectl get secret gateway-token-reviewer-token \
  --output 'go-template={{.data.token | base64decode}}')

Extract K8s Cluster CA Certificate

To extract the K8s cluster CA cert used to talk to Kubernetes API run the following command:

CA_CERT=$(kubectl config view --raw --minify --flatten  \
    --output 'jsonpath={.clusters[].cluster.certificate-authority-data}')
CA_CERT=$(openssl s_client -host <Rancher Server> -port 443 2>&1  | sed -n -e '/-----BEGIN CERTIFICATE-----/,/-----END CERTIFICATE-----/ p' | base64)

Create K8s Auth Method

  1. Use the Akeyless CLI to create the Kubernetes auth method which will restrict access to 2 different pods, named mypod1 and mypod2 from the namespace my-namespace-a. The result contains an access Id and a private key that you will need later for the K8S Auth configuration in your Gateway:
akeyless create-auth-method-k8s -n my-k8s-auth-method --bound-pod-names mypod1 \
    --bound-pod-names mypod2 --bound-namespaces my-namespace-a --json

Upon successful creation, the response:

{
  "access_id": "p-abcdefg1234",
  "prv_key": "LS0tLS1CRUdJTiBSUlNDUUxt.....QVRFIEtFWS0tLS0tCg=="
}

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Tip

Save returned private key & AccessID for next steps inside an environment variables $PRV_KEY and $ACCESS_ID.

Create K8s Gateway Auth Config Using Tokens

To discover your K8s service account issuer run the following command:

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Tip

Open a new tab to run this command as it starts a server. Then, go back to your original tab to extract the issuer.

Forwarding the Kubernetes API:

kubectl proxy --api-prefix=/k8s-api

Extract the issuer:

K8S_ISSUER=$(curl -s http://localhost:8001/k8s-api/.well-known/openid-configuration | jq -r .issuer)

Or extract the issuer directly from your pod token:

K8S_ISSUER=$(jq -R 'split(".") | .[1] | @base64d | fromjson |.iss' <<< $(cat /var/run/secrets/kubernetes.io/serviceaccount/token) -r)

Use the Akeyless CLI to create the K8S auth config. The following parameters are required:

  • name: The config name (will be used during the authentication process).

  • gateway-url: Your Gateway URL (default is http://localhost:8000).

  • access-id: The Access Id of the Kubernetes auth method that was created.

  • signing-key: The private key (The key that was created when the Kubernetes auth method was created).

  • cluster-api-type: By default work with native-k8s. To work with Rancher, please set rancher.

  • k8s-host: The URL of your Kubernetes API server endpoint. Or your Rancher server.

  • token-reviewer-jwt: Relevant only for native k8s - The service account JWT used to access the TokenReview API.

  • rancher-api-key: Relevant only for Rancher - Rancher Bearer token, based on the created Rancher API Key..

  • rancher-cluster-id: Relevant only for Rancher - Rancher Cluster ID, i.e., your Rancher API Key Scope.

  • k8s-ca-cert: The certificate to use to call into your Kubernetes API.

  • k8s-issuer: The Kubernetes JWT issuer name (default - kubernetes/serviceaccount).

akeyless gateway-create-k8s-auth-config  --name k8s-conf \
--gateway-url <https://Your-GW-URL>:8000 \
--access-id $ACCESS_ID \
--signing-key $PRV_KEY \
--k8s-host=<https://Your-K8s-Cluster-IP:8443> \
--token-reviewer-jwt $SA_JWT_TOKEN \
--k8s-ca-cert $CA_CERT \
--k8s-issuer $K8S_ISSUER
akeyless gateway-create-k8s-auth-config  --name k8s-conf-rancher \
--gateway-url <https://Your-GW-URL>:8000 \
--access-id $ACCESS_ID \
--signing-key $PRV_KEY \
--cluster-api-type rancher \
--k8s-host=<https://Rancher Host>:443 \
--k8s-ca-cert $CA_CERT \
--k8s-issuer $K8S_ISSUER \
--rancher-api-key <API_KEY> \
--rancher-cluster-id <CLUSTER_ID> \

Authenticate from a pod in your K8s cluster

  1. Create a namespace with a name that the auth method access is restricted to:
kubectl create namespace my-namespace-a
  1. In this namespace, create a pod with a name that the auth method access is restricted to:
kubectl run mypod1 --image=nginx -n my-namespace-a
  1. Start an interactive shell session on the pod and perform the following commands in the pod :
kubectl exec --stdin=true --namespace my-namespace-a  --tty=true mypod1 -- /bin/sh
  1. Install Akeyless CLI inside your pod:
curl -o akeyless https://akeyless-cli.s3.us-east-2.amazonaws.com/cli/latest/production/cli-linux-amd64
chmod +x akeyless
  1. Authenticate via your Kubernetes auth method with the following parameters :
  • access-id: The Access Id of the Kubernetes auth method that was created.

  • access-type: the access type - k8s

  • gateway-url: Your Gateway URL (default is http://localhost:8000)

  • k8s-auth-config-name: The K8s auth config name in your Gateway.

  • k8s-token-path: An optional path to a projected service account token inside the pod, for use instead of the default /var/run/secrets/kubernetes.io/serviceaccount/token

./akeyless auth --access-id $ACCESS_ID \
    --access-type k8s \
    --gateway-url https://<Your-GW-URL>:8000 \
    --k8s-auth-config-name k8s-conf

Upon successful authentication, the response will be:

Authentication succeeded.
Token: t-bb7b...3564a7c9

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Tip

Delete the private key and Access ID which you stored as an environment variables $PRV_KEY and $ACCESS_ID

Available claims for K8s Auth

The following list of claims can be configured within Akeyless Access Roles (RBAC) to control and segregate the relevant policy for K8s.

"service_account_name"
"service_account_uid"
"service_account_secret_name"
"namespace"
"aud"
"pod_name"   # available only when "token request projection" is enabled on your Kubernetes cluster
"pod_uid"    # available only when "token request projection" is enabled on your Kubernetes cluster

Each claim can be enforced as part of your role association to enforce the right policy for your items.

Enable token request projection on Minikube

To enable token request projection on a managed K8s cluster you can follow this guide.

To get this to work with Minikube you can start your cluster with the following configuration.

minikube start \
    --vm-driver=none \
    --extra-config=apiserver.service-account-signing-key-file=/var/lib/minikube/certs/sa.key \
    --extra-config=apiserver.service-account-key-file=/var/lib/minikube/certs/sa.pub \
    --extra-config=apiserver.service-account-issuer=api \
    --extra-config=apiserver.service-account-api-audiences=api,spire-server \
    --extra-config=apiserver.authorization-mode=Node,RBAC \
    --extra-config=kubelet.authentication-token-webhook=true

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Note:

This example uses api as the service account issuer name, for your service accounts API audience.