Azure Key Vault FlexVolume for Kubernetes - Integrates Azure Key Vault with Kubernetes via a FlexVolume.

With the Azure Key Vault FlexVolume, developers can access application-specific secrets, keys, and certs stored in Azure Key Vault directly from their pods.

The detailed design of this solution:

• Concept

💡 Make sure you have a Kubernetes cluster

Follow this to use acs-engine to create a new Kubernetes cluster with the Azure Key Vault FlexVolume already deployed.

kubectl create -f https://raw.githubusercontent.com/Azure/kubernetes-keyvault-flexvol/master/deployment/kv-flexvol-installer.yaml

To validate the installer is running as expected, run the following commands:

kubectl get pods -n kv

You should see the keyvault flexvolume installer pods running on each agent node:

keyvault-flexvolume-f7bx8   1/1       Running   0          3m
keyvault-flexvolume-rcxbl   1/1       Running   0          3m
keyvault-flexvolume-z6jm6   1/1       Running   0          3m

The KeyVault FlexVolume offers two modes for accessing a Key Vault instance: Service Principal and Pod Identity.

Add your service principal credentials as a Kubernetes secrets accessible by the KeyVault FlexVolume driver.

kubectl create secret generic kvcreds --from-literal clientid=<CLIENTID> --from-literal clientsecret=<CLIENTSECRET> --type=azure/kv

Ensure this service principal has all the required permissions to access content in your key vault instance. If not, you can run the following using the Azure cli:

# Assign Reader Role to the service principal for your keyvault
az role assignment create --role Reader --assignee <principalid> --scope /subscriptions/<subscriptionid>/resourcegroups/<resourcegroup>/providers/Microsoft.KeyVault/vaults/<keyvaultname>

az keyvault set-policy -n $KV_NAME --key-permissions get --spn <YOUR SPN CLIENT ID>
az keyvault set-policy -n $KV_NAME --secret-permissions get --spn <YOUR SPN CLIENT ID>
az keyvault set-policy -n $KV_NAME --certificate-permissions get --spn <YOUR SPN CLIENT ID>

Fill in the missing pieces in this deployment for your own deployment, make sure to:

1. reference the service principal kubernetes secret created in the previous step

secretRef:
  name: kvcreds

2. pass in properties for the Key Vault instance to the flexvolume driver.

3. Specify mount path of flexvolume to mount key vault objects

volumeMounts:
    - name: test
      mountPath: /kvmnt
      readOnly: true

Example of an nginx pod accessing a secret from a key vault instance:

apiVersion: v1
kind: Pod
metadata:
  name: nginx-flex-kv
spec:
  containers:
  - name: nginx-flex-kv
    image: nginx
    volumeMounts:
    - name: test
      mountPath: /kvmnt
      readOnly: true
  volumes:
  - name: test
    flexVolume:
      driver: "azure/kv"
      secretRef:
        name: kvcreds # mounting point to the pod
      options:
        usepodidentity: "false"
        keyvaultname: "testkeyvault"
        keyvaultobjectname: "testsecret"
        keyvaultobjecttype: secret # OPTIONS: secret, key, cert
        keyvaultobjectversion: "testversion"
        resourcegroup: "testresourcegroup"
        subscriptionid: "testsub"
        tenantid: "testtenant"

Deploy your app

kubectl create -f deployment/nginx-flex-kv.yaml

Validate the pod has access to the secret from key vault:

kubectl exec -it nginx-flex-kv cat /kvmnt/testsecret
testvalue

💡 Make sure you have installed pod identity to your Kubernetes cluster

1. Deploy pod identity components to your cluster Follow these steps to install pod identity.

2. Create an Azure User Identity

   Create an Azure User Identity with the following command. Get clientId and id from the output.

   az identity create -g <resourcegroup> -n <idname>
   

3. Assign permissions to new identity Ensure your Azure user identity has all the required permissions to read the keyvault instance and to access content within your key vault instance. If not, you can run the following using the Azure cli:

   # Assign Reader Role to new Identity for your keyvault
   az role assignment create --role Reader --assignee <principalid> --scope /subscriptions/<subscriptionid>/resourcegroups/<resourcegroup>/providers/Microsoft.KeyVault/vaults/<keyvaultname>
   
   # set policy to access keys in your keyvault
   az keyvault set-policy -n $KV_NAME --key-permissions get --spn <YOUR AZURE USER IDENTITY CLIENT ID>
   # set policy to access secrets in your keyvault
   az keyvault set-policy -n $KV_NAME --secret-permissions get --spn <YOUR AZURE USER IDENTITY CLIENT ID>
   # set policy to access certs in your keyvault
   az keyvault set-policy -n $KV_NAME --certificate-permissions get --spn <YOUR AZURE USER IDENTITY CLIENT ID>

4. Add a new AzureIdentity for the new identity to your cluster

   Edit and save this as aadpodidentity.yaml

   Set type: 0 for Managed Service Identity; type: 1 for Service Principal In this case, we are using managed service identity, type: 0. Create a new name for the AzureIdentity. Set ResourceID to id of the Azure User Identity created from the previous step.

   apiVersion: "aadpodidentity.k8s.io/v1"
   kind: AzureIdentity
   metadata:
    name: <any-name>
   spec:
    type: 0
    ResourceID: /subscriptions/<subid>/resourcegroups/<resourcegroup>/providers/Microsoft.ManagedIdentity/userAssignedIdentities/<idname>
    ClientID: <clientid>

   kubectl create -f aadpodidentity.yaml

5. Add a new AzureIdentityBinding for the new Azure identity to your cluster

   Edit and save this as aadpodidentitybinding.yaml

   apiVersion: "aadpodidentity.k8s.io/v1"
   kind: AzureIdentityBinding
   metadata:
    name: demo1-azure-identity-binding
   spec:
    AzureIdentity: <name_of_AzureIdentity_created_from_previous_step>
    Selector: <label value to match in your app>

   kubectl create -f aadpodidentitybinding.yaml
   

6. Add the following to your deployment yaml, like deployment/nginx-flex-kv-podidentity.yaml:

   a. Include the aadpodidbinding label matching the Selector value set in the previous step so that this pod will be assigned an identity

   metadata:
   labels:
       aadpodidbinding: "NAME OF the AzureIdentityBinding SELECTOR"

   b. make sure to update usepodidentity to true

   usepodidentity: "true"

7. Deploy your app

   kubectl create -f deployment/nginx-flex-kv-podidentity.yaml

8. Validate the pod has access to the secret from key vault:

   kubectl exec -it nginx-flex-kv-podid cat /kvmnt/testsecret
   testvalue

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