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Using bound service account tokens

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You can use bound service account tokens, which improves the ability to integrate with cloud provider identity access management (IAM) services, such as Red Hat OpenShift Service on AWS on AWS IAM or Google Cloud Platform IAM.

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About bound service account tokens

You can use bound service account tokens to limit the scope of permissions for a given service account token. These tokens are audience and time-bound. This facilitates the authentication of a service account to an IAM role and the generation of temporary credentials mounted to a pod. You can request bound service account tokens by using volume projection and the TokenRequest API.

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Configuring bound service account tokens using volume projection

You can configure pods to request bound service account tokens by using volume projection.

Prerequisites

  • You have access to the cluster as a user with the dedicated-admin role.

  • You have created a service account. This procedure assumes that the service account is named build-robot.

Procedure

  1. Configure a pod to use a bound service account token by using volume projection.

    1. Create a file called pod-projected-svc-token.yaml with the following contents:

      apiVersion: v1
kind: Pod
metadata:
  name: nginx
spec:
  securityContext:
    runAsNonRoot: true (1)
    seccompProfile:
      type: RuntimeDefault (2)
  containers:
  - image: nginx
    name: nginx
    volumeMounts:
    - mountPath: /var/run/secrets/tokens
      name: vault-token
    securityContext:
      allowPrivilegeEscalation: false
      capabilities:
        drop: [ALL]
  serviceAccountName: build-robot (3)
  volumes:
  - name: vault-token
    projected:
      sources:
      - serviceAccountToken:
          path: vault-token (4)
          expirationSeconds: 7200 (5)
          audience: vault (6)
      1 Prevents containers from running as root to minimize compromise risks.
      2 Sets the default seccomp profile, limiting to essential system calls, to reduce risks.
      3 A reference to an existing service account.
      4 The path relative to the mount point of the file to project the token into.
      5 Optionally set the expiration of the service account token, in seconds. The default value is 3600 seconds (1 hour), and this value must be at least 600 seconds (10 minutes). The kubelet starts trying to rotate the token if the token is older than 80 percent of its time to live or if the token is older than 24 hours.
      6 Optionally set the intended audience of the token. The recipient of a token should verify that the recipient identity matches the audience claim of the token, and should otherwise reject the token. The audience defaults to the identifier of the API server.

      In order to prevent unexpected failure, Red Hat OpenShift Service on AWS overrides the expirationSeconds value to be one year from the initial token generation with the --service-account-extend-token-expiration default of true. You cannot change this setting.

    2. Create the pod:

      $ oc create -f pod-projected-svc-token.yaml

      The kubelet requests and stores the token on behalf of the pod, makes the token available to the pod at a configurable file path, and refreshes the token as it approaches expiration.

  2. The application that uses the bound token must handle reloading the token when it rotates.

    The kubelet rotates the token if it is older than 80 percent of its time to live, or if the token is older than 24 hours.

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Creating bound service account tokens outside the pod

Prerequisites

  • You have created a service account. This procedure assumes that the service account is named build-robot.

Procedure

  • Create the bound service account token outside the pod by running the following command:

    $ oc create token build-robot
    Example output
    eyJhbGciOiJSUzI1NiIsImtpZCI6IkY2M1N4MHRvc2xFNnFSQlA4eG9GYzVPdnN3NkhIV0tRWmFrUDRNcWx4S0kifQ.eyJhdWQiOlsiaHR0cHM6Ly9pc3N1ZXIyLnRlc3QuY29tIiwiaHR0cHM6Ly9pc3N1ZXIxLnRlc3QuY29tIiwiaHR0cHM6Ly9rdWJlcm5ldGVzLmRlZmF1bHQuc3ZjIl0sImV4cCI6MTY3OTU0MzgzMCwiaWF0IjoxNjc5NTQwMjMwLCJpc3MiOiJodHRwczovL2lzc3VlcjIudGVzdC5jb20iLCJrdWJlcm5ldGVzLmlvIjp7Im5hbWVzcGFjZSI6ImRlZmF1bHQiLCJzZXJ2aWNlYWNjb3VudCI6eyJuYW1lIjoidGVzdC1zYSIsInVpZCI6ImM3ZjA4MjkwLWIzOTUtNGM4NC04NjI4LTMzMTM1NTVhNWY1OSJ9fSwibmJmIjoxNjc5NTQwMjMwLCJzdWIiOiJzeXN0ZW06c2VydmljZWFjY291bnQ6ZGVmYXVsdDp0ZXN0LXNhIn0.WyAOPvh1BFMUl3LNhBCrQeaB5wSynbnCfojWuNNPSilT4YvFnKibxwREwmzHpV4LO1xOFZHSi6bXBOmG_o-m0XNDYL3FrGHd65mymiFyluztxa2lgHVxjw5reIV5ZLgNSol3Y8bJqQqmNg3rtQQWRML2kpJBXdDHNww0E5XOypmffYkfkadli8lN5QQD-MhsCbiAF8waCYs8bj6V6Y7uUKTcxee8sCjiRMVtXKjQtooERKm-CH_p57wxCljIBeM89VdaR51NJGued4hVV5lxvVrYZFu89lBEAq4oyQN_d6N1vBWGXQMyoihnt_fQjn-NfnlJWk-3NSZDIluDJAv7e-MTEk3geDrHVQKNEzDei2-Un64hSzb-n1g1M0Vn0885wQBQAePC9UlZm8YZlMNk1tq6wIUKQTMv3HPfi5HtBRqVc2eVs0EfMX4-x-PHhPCasJ6qLJWyj6DvyQ08dP4DW_TWZVGvKlmId0hzwpg59TTcLR0iCklSEJgAVEEd13Aa_M0-faD11L3MhUGxw0qxgOsPczdXUsolSISbefs7OKymzFSIkTAn9sDQ8PHMOsuyxsK8vzfrR-E0z7MAeguZ2kaIY7cZqbN6WFy0caWgx46hrKem9vCKALefElRYbCg3hcBmowBcRTOqaFHLNnHghhU1LaRpoFzH7OUarqX9SGQ
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