Create an OpenID Connect provider on Azure Kubernetes Service (AKS)

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OpenID Connect (OIDC) extends the OAuth 2.0 authorization protocol for use as another authentication protocol issued by Microsoft Entra ID. You can use OIDC to enable single sign-on (SSO) between OAuth-enabled applications on your Azure Kubernetes Service (AKS) cluster by using a security token called an ID token. With your AKS cluster, you can enable the OpenID Connect (OIDC) issuer, which allows Microsoft Entra ID, or another cloud provider's identity and access management platform, to discover the API server's public signing keys.

AKS rotates the key automatically and periodically. If you don't want to wait, you can rotate the key manually and immediately. The maximum lifetime of the token issued by the OIDC provider is one day.

Warning

Enabling the OIDC issuer on an existing cluster changes the current service account token issuer to a new value, which can cause down time as it restarts the API server. If your application pods using a service token remain in a failed state after you enable the OIDC issuer, we recommend you manually restart the pods.

In this article, you learn how to create, update, and manage the OIDC issuer for your cluster.

Important

After you enable the OIDC issuer on the cluster, disabling it is not supported.

The token needs to be refreshed periodically. If you use the SDK, the rotation is automatic. Otherwise, you need to refresh the token manually every 24 hours.

Prerequisites

  • The Azure CLI version 2.42.0 or higher. Run az --version to find your version. If you need to install or upgrade, see Install Azure CLI.
  • AKS supports the OIDC issuer on version 1.22 and higher.

Create an AKS cluster with the OIDC issuer

You can create an AKS cluster using the az aks create command with the --enable-oidc-issuer parameter to enable the OIDC issuer. The following example creates a cluster named myAKSCluster with one node in the myResourceGroup:

az aks create \
    --resource-group myResourceGroup \
    --name myAKSCluster \
    --node-count 1 \
    --enable-oidc-issuer \
    --generate-ssh-keys

Update an AKS cluster with OIDC issuer

You can update an AKS cluster using the az aks update command with the --enable-oidc-issuer parameter to enable the OIDC issuer. The following example updates a cluster named myAKSCluster:

az aks update --resource-group myResourceGroup --name myAKSCluster --enable-oidc-issuer

Show the OIDC issuer URL

To get the OIDC issuer URL, run the az aks show command. Replace the default values for the cluster name and the resource group name.

az aks show --name myAKScluster --resource-group myResourceGroup --query "oidcIssuerProfile.issuerUrl" -o tsv

By default, the issuer is set to use the base URL https://{region}.oic.prod-aks.azure.com, where the value for {region} matches the location the AKS cluster is deployed in.

Rotate the OIDC key

To rotate the OIDC key, run the az aks oidc-issuer command. Replace the default values for the cluster name and the resource group name.

az aks oidc-issuer rotate-signing-keys --name myAKSCluster --resource-group myResourceGroup

Important

Once you rotate the key, the old key (key1) expires after 24 hours. Both the old key (key1) and the new key (key2) are valid within the 24-hour period after rotation. If you want to invalidate the old key (key1) immediately, you must rotate the OIDC key twice and restart the pods using projected service account tokens. With this process, key2 and key3 are valid, and key1 is invalid.

Check the OIDC keys

Get the OIDC issuer URL

To get the OIDC issuer URL, run the az aks show command. Replace the default values for the cluster name and the resource group name.

az aks show --name myAKScluster --resource-group myResourceGroup --query "oidcIssuerProfile.issuerUrl" -o tsv

The output should resemble the following:

https://chinaeast2.oic.prod-aks.azure.com/00000000-0000-0000-0000-000000000000/11111111-1111-1111-1111-111111111111/

By default, the issuer is set to use the base URL https://{region}.oic.prod-aks.azure.com/{tenant_id}/{uuid}, where the value for {region} matches the location the AKS cluster is deployed in. The value {uuid} represents the OIDC key, which is a randomly generated guid for each cluster that is immutable.

Get the discovery document

To get the discovery document, copy the URL https://(OIDC issuer URL).well-known/openid-configuration and open it in browser.

The output should resemble the following:

{
  "issuer": "https://chinaeast2.oic.prod-aks.azure.com/ffffffff-eeee-dddd-cccc-bbbbbbbbbbb0/00000000-0000-0000-0000-000000000000/",
  "jwks_uri": "https://chinaeast2.oic.prod-aks.azure.com/00000000-0000-0000-0000-000000000000/00000000-0000-0000-0000-000000000000/openid/v1/jwks",
  "response_types_supported": [
    "id_token"
  ],
  "subject_types_supported": [
    "public"
  ],
  "id_token_signing_alg_values_supported": [
    "RS256"
  ]
}

Get the JWK Set document

To get the JWK Set document, copy the jwks_uri from the discovery document and past it in your browser's address bar.

The output should resemble the following:

{
  "keys": [
    {
      "use": "sig",
      "kty": "RSA",
      "kid": "xxx",
      "alg": "RS256",
      "n": "xxxx",
      "e": "AQAB"
    },
    {
      "use": "sig",
      "kty": "RSA",
      "kid": "xxx",
      "alg": "RS256",
      "n": "xxxx",
      "e": "AQAB"
    }
  ]
}

During key rotation, there's one other key present in the discovery document.

Next steps