Unauthenticated Issuer Discovery

If you are using Kubernetes with tools like kind, vCluster, minikube, or similar solutions for local development, it's highly likely that the Kubernetes OIDC Issuer operates within the cluster and is secured with self-signed certificates.

To facilitate the use of m2m tokens with oauth2-proxy and Istio, both tools must perform OIDC Connect Discovery on the Token Issuer. Kubernetes offers OIDC Discovery functionality at a specific URI:

https://kubernetes.default.svc.cluster.local/.well-known/openid-configuration

Access to this endpoint is blocked by default due to RBAC policies, but it can be enabled by creating a ClusterRoleBinding. This binding associates the predefined ClusterRole system:service-account-issuer-discovery with the system:unauthenticated group. The configuration for this is detailed in the resource file clusterrolebinding.unauthenticated-oidc-viewer.yaml.

Once this step is completed, the endpoint can be accessed to reveal the Issuer URL:

$ curl -k https://kubernetes.default.svc.cluster.local/.well-known/openid-configuration

# Example output in kind:
{"issuer":"https://kubernetes.default.svc.cluster.local","jwks_uri":"https://172.18.0.5:6443/openid/v1/jwks","response_types_supported":["id_token"],"subject_types_supported":["public"],"id_token_signing_alg_values_supported":["RS256"]}

# Example output in vCluster:
{"issuer":"https://kubernetes.default.svc.cluster.local","jwks_uri":"https://1.2.3.4:6443/openid/v1/jwks","response_types_supported":["id_token"],"subject_types_supported":["public"],"id_token_signing_alg_values_supported":["RS256"]}

# Example output in AWS EKS:
{"issuer":"https://oidc.eks.region.amazonaws.com/id/123abc","jwks_uri":"https://ip-1-2-3-4.eu-central-1.compute.internal:443/openid/v1/jwks","response_types_supported":["id_token"],"subject_types_supported":["public"],"id_token_signing_alg_values_supported":["RS256"]}

If you're operating in a vCluster, access to the endpoint specified under jwks_uri (for example, https://1.2.3.4:6443/openid/v1/jwks) is managed separately, and merely creating the previously mentioned ClusterRoleBinding is insufficient. To circumvent this limitation, you can configure the kube-apiserver to allow anonymous authentication by setting --anonymous-auth=true. This is achieved by appending --kube-apiserver-arg=anonymous-auth=true to the list of arguments in the Helm Chart Values file:

vcluster:
    extraArgs:
    - --kube-apiserver-arg=anonymous-auth=true

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Unauthenticated Issuer Discovery

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