Securing Your Clusters

How to secure Kubeflow clusters using private GKE

These instructions explain how to deploy Kubeflow using private GKE.

  1. Follow the blueprint instructions to setup a management cluster

  2. As a workaround for Issue kubeflow/gcp-blueprints#32 (in CNRM 1.9.1, the CustomResourceDefinition (CRD) for container cluster is missing ipAllocationPolicy fields needed to create a private GKE cluster), modify the container cluster CRD schema in your management cluster to include the missing fields.

    • Check Issue kubeflow/gcp-blueprints#32 to find out if it has been resolved in later versions of CNRM. If the issue hasn’t been resolved, you can follow the instructions in the issue to work around the problem.

  3. Fetch the blueprint by running this command:

    1. kpt pkg get https://github.com/kubeflow/gcp-blueprints.git/kubeflow@master ./${PKGDIR}
    • This will create the directory ${PKGDIR} with the blueprint.

  4. Change to the Kubeflow directory:

    1. cd ${PKGDIR}

  5. Fetch Kubeflow manifests:

    1. make get-pkg

  6. Add the private GKE patches to your kustomization

    1. Open instance/gcp_config

    2. In patchesStrategicMerge add

      1. - ../../upstream/manifests/gcp/v2/privateGKE/cluster-private-patch.yaml

    3. In resources add

      1. - ../../upstream/manifests/gcp/v2/privateGKE/

  7. Open the Makefile and edit the set-values rule to invoke kpt cfg set with the desired values for your deployment.

    • Change kpt cfg set ./instance gke.private false to kpt cfg set ./instance gke.private true
    • You need to set region, location and zone because the deployment is a mix of zonal and regional resources and some which could be either

Deploy Kubeflow

  1. Configure the setters

    1. make set-values

  2. Set environment variables with OAuth Client ID and Secret for IAP.

    1. export CLIENT_ID=<client id>
    2. export CLIENT_SECRET=<client secret>

  3. Deploy Kubeflow

    1. make apply

    • In this case you can simply edit the Makefile and comment out the line

      1. kubectl --context=$(MGMTCTXT) wait --for=condition=Ready --timeout=600s  containercluster $(NAME)

    • Then rerun make apply

  4. The cloud endpoints controller doesn’t work with private GKE (kubeflow/gcp-blueprints#36) as a workaround you can run kfctl locally to create the endpoint

    1. kfctl apply -f .build/iap-ingress/ctl.isla.solutions_v1_cloudendpoint_${KFNAME}.yaml

Architectural notes

  • The reference architecture uses Cloud Nat to allow outbound internet access from node even though they don’t have public IPs.

    • Outbound traffic can be restricted using firewall rules

    • Outbound internet access is needed to download the JWKs keys used to verify JWTs attached by IAP

    • If you want to completely disable all outbound internet access you will have to find some alternative solution to keep the JWKs in sync with your ISTIO policy

Troubleshooting

  • Cluster is stuck in provisioning state.

    • Use the UI or gcloud to figure out what state the cluster is stuck in

    • If you use gcloud you need to look at the operation e.g.

      1. Find the operations

        1. gcloud --project=${PROJECT} container operations list

      2. Get operation details

        1. gcloud --project=${PROJECT} container operations describe --region=${REGION} ${OPERATION}

  • Cluster health checks are failing.

    • This is usually because the firewall rules allowing the GKE health checks are not configured correctly

    • A good place to start is verifying they were created correctly

      1. kubectl --context=${MGMTCTXT} describe computefirewall

    • Turn on firewall rule logging to see what traffic is being blocked.

      1. kpt cfg set ./upstream/manifests/gcp/v2/privateGKE/ log-firewalls true
      2. make apply

    • To look for traffic blocked by firewall rules in stackdriver use a filter like the following

      1. logName: "projects/${PROJECT}/logs/compute.googleapis.com%2Ffirewall" 
      2. jsonPayload.disposition = "DENIED"

      • Logging must be enabled on your firewall rules. You can enable it by using a kpt setter

        1. kpt cfg set ./upstream/manifests/gcp/v2/privateGKE/ log-firewalls true

      • Change project to your project

      • Then look at the fields jsonPayload.connection this will tell you source and destination ips

      • Based on the IPs try to figure out where the traffic is coming from (e.g. node to master) and then match to appropriate firewall rules

      • For example

        1. connection: {
        2.  dest_ip: "172.16.0.34"    
        3.  dest_port: 443    
        4.  protocol: 6    
        5.  src_ip: "10.10.10.31"    
        6.  src_port: 60556    
        7. }
        8. disposition: "DENIED"
        • The destination IP in this case is for a GKE master so the firewall rules are not configured to correctly allow traffic to the master.

  • Common cause for networking related issue is is that some of the network resources (e.g. the Network, Routes, Firewall Rules, etc… ) don’t get created

    • This could be because a reference is incorrect (e.g. firewall rules reference the wrong network)

    • You can double check resources by doing kubectl describe and looking for errors.

  • Google Container Registry (GCR) images can’t be pulled.

    • This likely indicates an issue with access to private GCR. This could be because of:

      • DNS configurations: Check that the DNSRecordSet and DNSManagedZone CNRM resources are in a ready state.

      • Routes: Make sure any default route to the internet has a larger value for the priority then any routes to private GCP APIs so that the private routes match first.

        • If image pull errors show IP addresses and not the restricted.googleapis.com VIP, then you have an issue with networking.
      • Firewall rules

  • Access to allowed (non-Google) sites is blocked

    • The configuration uses CloudNat to allow selective access to sites/

      • In addition to allowing IAP, this allows sites like GitHub to be accessed.

    • In order for CloudNat to work you need

      • A default route to the internet

      • Firewall rules to allow egress traffic to allowed sites

        • These rules need to be higher priority then the deny all firewall egress rules.

Kubernetes Webhooks are blocked by firewall rules

A common failure mode is that webhooks for custom resources are blocked by default firewall rules. As explained in the GKE docs, only connections from master to ports 443 and 10250 are allowed by default. If you have a webhook serving on a different port you will need to add an explict ingress firewall rule to allow that port to be accessed.

These errors usually manifest as failures to create custom resources that depend on webhooks. An example error is:

  1. Error from server (InternalError): error when creating ".build/kubeflow-apps/cert-manager.io_v1alpha2_certificate_admission-webhook-cert.yaml": Internal error occurred: failed calling webhook "webhook.cert-manager.io": the server is currently unable to handle the request

Next steps

Last modified 05.10.2020: Fix typos GKE documentation (#2253) (e1a85d47)