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secure-storage-with-psp.md

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Secure storage access using Pod Security Policy (PSP)

Pod Security Policy can be used to control the security aspects of the pod deployments. This document walks you through an example deployment using nginx unprivileged container.

Requirements

  1. Kubernetes v1.14 or above.

    • On Kubernetes versions lower than v1.14 runAsGroup does not work

  2. Quobyte CSI driver deployment with PSP policies.

  3. PodSecurityPolicy admission plugin must be enabled. Edit /etc/kubernetes/manifests/kube-apiserver.yaml on master nodes and append --enable-admission-plugins with PodSecurityPolicy. After that, restart the nodes or kube-apiserver pods.

  4. User and Group specified in PSP must exist on the host nodes.

  5. Nginx PSP Demo pod requires

    • Hosts with nginx user (UID: 5050) and group (GID:5050). These UID and GID are used in the example PSP. Create nginx user and group.

      sudo groupadd -g 5050 nginx; sudo useradd -u 5050 -g 5050 nginx

    • Volume with at least read and execute permissions for the nginx user. Volume permissions can be configured in StorageClass as accessMode for dynamically provisioned volumes.

  6. All the example commands should be executed from the root directory of Quobyte CSI. Please get the Quobyte CSI example files and change to root directory.

      git clone https://github.com/quobyte/quobyte-csi.git
  cd quobyte-csi

PSP example

Let us dive in and create an example PSP with restricted access. Using the example psp, we can deploy unprivileged nginx pod.

  1. Create quobyte namespace

    kubectl create ns quobyte

  2. Create Quobyte admin secret (credentials are required for dynamic volume provision)

    kubectl create -f example/quobyte-admin-credentials.yaml

  3. Review and create storage class

    kubectl create -f example/psp/StorageClass-PSP.yaml

  4. Create a namespace psp-example to run the nginx pod nginx user

    kubectl create namespace psp-example

  5. Create a service account psp-user in psp-example namespace

    kubectl create serviceaccount -n psp-example psp-user

  6. Create aliases for kubectl commands. kubectl-admin is the admin user and kubectl-user is the service account psp-user in the namespace psp-example.

    # Admin user in the namespace "psp-example"
alias kubectl-admin='kubectl -n psp-example'
# psp-user in the namespace "psp-example"
alias kubectl-user='kubectl --as=system:serviceaccount:psp-example:psp-user -n psp-example'

  7. Update UID and GID in example PSP definition and create PSP.

    kubectl create -f example/psp/psp-example-definition.yaml

  8. Create Role and RoleBindings for the psp-user in psp-example namespace

    kubectl-admin create -f example/psp/psp-example-roles.yaml

  9. Verify psp-user can access the pod security policy example-psp

    kubectl-user auth can-i use psp/example-psp

    The above command should output yes for user to be able to deploy pods.

  10. Create PVC

    kubectl-user create -f example/psp/pvc-dynamic-provision-psp.yaml

  11. Create Pod with the created PVC

    kubectl-user create -f example/psp/nginx-demo-pod-with-psp.yaml

  12. Wait for the pod to be in running state

    kubectl get po -w | grep 'nginx-psp-demo'

  13. Verify user UID/GID inside created pod

    kubectl-admin exec -it nginx-psp-demo -- id

  14. Copy index file into the pod

    Unfortunately, kubectl cp does not work with non-root users. This should be done manually.

    Connect to the pod

    kubectl-admin exec -it nginx-psp-demo -- bash

    Create index.html

    cat > /usr/share/nginx/html/index.html <<EOF
<!DOCTYPE html>
<html>

<head>
  <title>Welcome to Quobyte CSI!</title>
</head>

<body>
  <h1>Welcome to Quobyte CSI!</h1>
  <p>This file is retrieved from the mounted Quobyte volume.</p>

  <p><em>Thank you for using Quobyte.</em></p>
</body>

</html>
EOF

    Please verify file permissions on the created index.html and exit from the pod.

    ls -l /usr/share/nginx/html/index.html
exit

  15. Access the index page from the command line

    curl http://$(kubectl-user get pods nginx-psp-demo -o yaml | grep 'podIP:' | awk '{print $2}'):8080

    The above command should retrieve the Quobyte CSI welcome page (in raw html format).