API Server: Unable to authenticate the request due to an error: invalid bearer token

Question

I set up a sample Kubernetes Cluster with 3 master nodes and 2 worker nodes. I tried to connect it to an OpenId Provider (in my case Keycloak). But when querying the API I get the following message from kubectl:

error: You must be logged in to the server (Unauthorized)

or via curl:

curl -H "Authorization: Bearer $token" -k https://192.168.178.30:6443/api/v1/namespaces/default/pods
{
  "kind": "Status",
  "apiVersion": "v1",
  "metadata": {
    
  },
  "status": "Failure",
  "message": "Unauthorized",
  "reason": "Unauthorized",
  "code": 401
}

and in the API server logs it says

Unable to authenticate the request due to an error: invalid bearer token

According to jwt.io my token seems to be valid.

Configuration of the API server

In the API server I specified the following parameters:

oidc-issuer-url: https://192.168.178.25:8443/auth/realms/master
oidc-client-id: account
oidc-ca-file: /etc/kubernetes/ssl/keycloak-rootCA.pem
oidc-username-claim: sub
oidc-groups-claim: groups

I had to specify the CA file, because the certificate used for keycloak was a self signed one

The certificate seems to work, because a curl without the CA file results in an error; where specifying the CA file doesn't:

ansible@node1:~$ curl https://192.168.178.25:8443/auth/realms/master
curl: (60) SSL certificate problem: unable to get local issuer certificate
More details here: https://curl.haxx.se/docs/sslcerts.html

curl failed to verify the legitimacy of the server and therefore could not
establish a secure connection to it. To learn more about this situation and
how to fix it, please visit the web page mentioned above.


ansible@node1:~$ curl --cacert /etc/kubernetes/ssl/keycloak-rootCA.pem https://192.168.178.25:8443/auth/realms/master
{"realm":"master","public_key":"...","token-service":"https://192.168.178.25:8443/auth/realms/master/protocol/openid-connect","account-service":"https://192.168.178.25:8443/auth/realms/master/account","tokens-not-before":0}

JWT Token

The payload of my JWT token looks the following:

{
  "jti": "455feab7-5828-49f3-9243-a2ce0a1ae6f9",
  "exp": 1557246081,
  "nbf": 0,
  "iat": 1557246021,
  "iss": "https://192.168.178.25:8443/auth/realms/master",
  "aud": "account",
  "sub": "78f9bdc8-d1a4-43c4-ab83-f1b4645519f6",
  "typ": "ID",
  "azp": "account",
  "auth_time": 1557246020,
  "session_state": "ccafaa62-a888-43dd-9135-1c5a31766e0b",
  "acr": "1",
  "email_verified": true,
  "name": "Testuser",
  "groups": [
    "group1",
    "k8s-admin"
  ],
  "preferred_username": "dummy-username",
  "given_name": "Firstname1",
  "family_name": "Lastname1",
  "email": "[email protected]"
}

When I try to login with the token of a generated service account (from kubernetes) everything works fine.

additional Information

The environment was set up via Kubespray and the API server parameters specified in the following way:

kube_oidc_url: https://192.168.178.25:8443/auth/realms/master
kube_oidc_client_id: account
kube_oidc_ca_file: "{{ kube_cert_dir }}/keycloak-rootCA.pem"
kube_oidc_username_claim: sub
kube_oidc_groups_claim: groups
#kube_oidc_username_prefix: "oidc:"
#kube_oidc_groups_prefix: "oidc:"

Thanks for your help.

Answer 1

The issue was that Kubespray did not overtake my settings into the Pod spec of the api-server (/etc/kubernetes/manifests/kube-apiserver.yaml). When I added the parameters in the Pod spec of each api-server (I have a multi master setup), it worked as expected:

- --oidc-issuer-url=https://192.168.178.25:8443/auth/realms/master
- --oidc-client-id=account
- --oidc-username-claim=email
- '--oidc-username-prefix=oidc:'
- --oidc-groups-claim=groups
- '--oidc-groups-prefix=oidc:'
- --oidc-ca-file=/etc/kubernetes/ssl/keycloak-rootCA.pem