Kubernetes-KeyVault-FlexVolume

Key Vault FlexVolume for Kubernetes - Integrates Key Management Systems with Kubernetes via a FlexVolume.

With the Key Vault FlexVolume, developers can mount multiple secrets, keys, and certs stored in Key Management Systems into their pods as a volume. Once the Volume is attached, the data in it is mounted into the container's file system.

Supported Providers

• Azure Key Vault

💡 NOTE: To enable encryption at rest of Kubernetes data in etcd using Azure Key Vault, use Kubernetes KMS plugin for Azure Key Vault.

Design

The detailed design of this solution:

• Concept

How to use

Prerequisites:

💡 Make sure you have a Kubernetes cluster

Install the KeyVault Flexvolume

OPTION 1 - AKS-Engine addon

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

OPTION 2 - AKS (Azure Kubernetes Service) Manually

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

Use the KeyVault FlexVolume

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

OPTION 1 - Service Principal

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.

Name	Required	Description	Default Value
usepodidentity	no	specify access mode: service principal or pod identity	"false"
keyvaultname	yes	name of KeyVault instance	""
keyvaultobjectnames	yes	names of KeyVault objects to access	""
keyvaultobjectaliases	no	filenames to use when writing the objects	keyvaultobjectnames
keyvaultobjecttypes	yes	types of KeyVault objects: secret, key or cert	""
keyvaultobjectversions	no	versions of KeyVault objects, if not provided, will use latest	""
resourcegroup	yes	name of resource group containing key vault instance	""
subscriptionid	yes	name of subscription containing key vault instance	""
tenantid	yes	name of tenant containing key vault instance	""

keyvaultobjectnames, keyvaultobjecttypes and keyvaultobjectversions are semi-colon (;) separated.

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"
        keyvaultobjectnames: "testsecret"
        keyvaultobjectaliases: "secret.json" # optional
        keyvaultobjecttypes: secret # OPTIONS: secret, key, cert
        keyvaultobjectversions: "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

OPTION 2 - Pod identity

Prerequisites:

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

This project makes use of the aad-pod-identity project located here to handle the identity management of the pods. Reference the aad-pod-identity README if you need further instructions on any of these steps.

Not all steps need to be followed on the instructions for the aad-pod-identity project as we will also complete some of the steps on our installation here.

1. Install the aad-pod-identity components to your cluster

   • Install the RBAC enabled aad-pod-identiy infrastructure components:

     kubectl create -f https://raw.githubusercontent.com/Azure/aad-pod-identity/master/deploy/infra/deployment-rbac.yaml
     

   • (Optional) Providing required permissions for MIC

     • If the SPN you are using for the AKS cluster was created separately (before the cluster creation - i.e. not part of the MC_ resource group) you will need to assign it the "Managed Identity Operator" role.

       az role assignment create --role "Managed Identity Operator" --assignee <sp id> --scope <full id of the managed 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

Specific use cases

• A detailed example for using a KeyVault certificate to setup an SSL entrypoint with Traefik

About KeyVault

The Key Vault FlexVolume interacts with keyvault objects by using the keyvault API. If you need to understand the difference between Keys, Secrets and Certificate objects, we recommend that you start by reading the thorough documentation available on Keyvault : About keys, secrets, and certificates

More about Certificates

It is important to understand how a certificate is structured in keyvault. As mentioned in the REST API docs here and here, Azure Key Vault (AKV) represents a given X.509 certificate via three interrelated resources: an AKV-certificate, an AKV-key, and an AKV-secret. All three will share the same name and the same version and can be fetched independently.

• The AKV-certificate provides the public key and certificate metadata. Specifying cert in keyvaultobjecttypes will fetch the public key and certificate metadata.
• The AKV-key provides the private key of the X.509 certificate. It can be useful for performing cryptographic operations such as signing if the corresponding certificate was marked as non-exportable. Specifying key in keyvaultobjecttypes will fetch the private key of the certificate if its policy allows for private key exporting.
• The AKV-secret provides a way to export the full X.509 certificate, including its private key (if its policy allows for private key exporting). Specifying secret in keyvaultobjecttypes will fetch the base64-encoded certificate bundle.

Contributing

This project welcomes contributions and suggestions. Most contributions require you to agree to a Contributor License Agreement (CLA) declaring that you have the right to, and actually do, grant us the rights to use your contribution. For details, visit https://cla.microsoft.com.

When you submit a pull request, a CLA-bot will automatically determine whether you need to provide a CLA and decorate the PR appropriately (e.g., label, comment). Simply follow the instructions provided by the bot. You will only need to do this once across all repos using our CLA.

This project has adopted the Microsoft Open Source Code of Conduct. For more information see the Code of Conduct FAQ or contact [email protected] with any additional questions or comments.