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Running the Vault secret webhook alongside Istio

Author Nandor Kracser

One of the most popular feature of Bank-Vaults, the Vault swiss-army knife for Kubernetes is the secret injection webhook. With the growing popularity of Istio, recently the most requested feature was to support for running Bank-Vaults alongside Istio. We are big fans of Istio (a year ago we open sourced an Istio operator) and we have built an automated and operationalized service mesh, Banzai Cloud Backyards. As both components (Bank-Vaults and Backyards) are part of our hybrid cloud container management plaform, Pipeline, we went ahead and made them work together smoothly.

We support the following three scenarios:

  • Scenario 1: Vault runs outside an Istio mesh, whereas the namespace where the application runs and the webhook injects secrets has Istio sidecar injection enabled
  • Scenario 2: The namespace where Vault is running has Istio sidecar injection enabled
  • Scenario 3: Both namespaces have Istio sidecar injection enabled

Prerequisites 🔗︎

Install the Banzai Cloud Istio operator with the Backyards CLI 🔗︎

  1. Register for an evaluation version and run the following command to install the CLI tool (KUBECONFIG must be set for your cluster):

    curl https://getbackyards.sh | sh
    
  2. Install the Istio operator using Backyards. For this example we need only the Istio operator, however feel free to experiment with the nice Backyards UI/CLI and the large collection of automated features like observability, traffic routing, canary, circuit breakers, and so on - check out this long list of features.

    backyards install
    ? Install istio-operator (recommended). Press enter to accept Yes
    ? Install canary-operator (recommended). Press enter to accept No
    ? Install and run demo application (optional). Press enter to skip No
    
  3. Make sure you have mTLS enabled in the Istio mesh through the operator with the following command:

    Enable mTLS if it is not set to STRICT:

    ❯ backyards mtls require mesh
    INFO[0000] switched global mTLS to STRICT successfully
    

    After this, we can check that mesh is configured with mTLS turned on which applies to all applications in the cluster in Istio-enabled namespaces. You can change this if you would like to use another policy.

    $ backyards mtls get mesh
    mTLS rule for /mesh
    
    Policy    Targets  MtlsMode  
    /default  []       STRICT
    

Now your cluster is properly running on Istio with mTLS enabled globally.

Install the Bank-Vaults components 🔗︎

  1. You are recommended to create a separate namespace for Bank-Vaults called vault-system. You can enable Istio sidecar injection here as well, but Kubernetes won’t be able to call back the webhook properly since mTLS is enabled (and Kubernetes is outside of the Istio mesh). To overcome this, apply a PERMISSIVE Istio authentication policy to the vault-secrets-webhook Service itself, so Kubernetes can call it back without Istio mutual TLS authentication.

    $ kubectl create namespace vault-system
    namespace/vault-system created
    
    $ backyards sidecar-proxy auto-inject on vault-system
    INFO[0002] auto sidecar injection successfully set to namespace default
    
    $ backyards mtls allow vault-system/vault-secrets-webhook
    INFO[0001] policy peers for vault-system/vault-secrets-webhook set successfully
    
    mTLS rule for vault-system/vault-secrets-webhook
    
    Policy                                    Targets                  MtlsMode
    vault-system/vault-secrets-webhook-rw6mc  [vault-secrets-webhook]  PERMISSIVE
    
  2. Now you can install the operator and the webhook to the prepared namespace:

    helm repo add banzaicloud-stable https://kubernetes-charts.banzaicloud.com
    helm upgrade --install vault-secrets-webhook banzaicloud-stable/vault-secrets-webhook --namespace vault-system
    helm upgrade --install vault-operator banzaicloud-stable/vault-operator --namespace vault-system
    

Soon the webhook and the operator become up and running. Check that the istio-proxy got injected into all Pods in vault-system.

Scenario 1: Vault runs outside, the application inside the mesh 🔗︎

To recap Scenario 1: Vault runs outside an Istio mesh, whereas the namespace where the application runs and the webhook injects secrets has Istio sidecar injection enabled.

First, install Vault outside the mesh, then install an application within the mesh.

Install Vault outside the mesh 🔗︎

  1. Provision a Vault instance with the Bank-Vaults operator in a separate namespace:

    kubectl create namespace vault
    
  2. Apply the RBAC and CR files to the cluster to create a Vault instance in the vault namespace with the operator:

    kubectl apply -f rbac.yaml -f cr-istio.yaml
    
    $ kubectl get pods -n vault
    NAME                               READY   STATUS    RESTARTS   AGE
    vault-0                            3/3     Running   0          22h
    vault-configurer-6458cc4bf-6tpkz   1/1     Running   0          22h
    

    If you are writing your own Vault CR make sure that istioEnabled: true is configured, this influences port naming so the Vault service port protocols are detected by Istio correctly.

  3. The vault-secrets-webhook can’t inject Vault secrets into initContainers in an Istio-enabled namespace when the STRICT authentication policy is applied to the Vault service, because Istio needs a sidecar container to do mTLS properly, and in the phase when initContainers are running the Pod doesn’t have a sidecar yet. If you wish to inject into initContainers as well, you need to apply a PERMISSIVE authentication policy in the vault namespace, since it has its own TLS certificate outside of Istio scope (so this is safe to do from networking security point of view).

    $ backyards mtls allow vault
    INFO[0001] policy peers for vault/ set successfully
    
    mTLS rule for vault/
    
    Policy         Targets  MtlsMode
    vault/default  []       PERMISSIVE
    

Install the application inside a mesh 🔗︎

In this scenario Vault is running outside the Istio mesh (as we have installed it in the previous steps) and our demo application runs within the Istio mesh. To install the demo application inside the mesh, complete the following steps:

  1. Create a namespace first for the application and enable Istio sidecar injection:

    kubectl create namespace app
    
    backyards sidecar-proxy auto-inject on app
    
  2. Install the application manifest to the cluster:

    kubectl apply -f app.yaml
    
  3. Check that the application is up and running. It should have two containers, the app itself and the istio-proxy:

    $ kubectl get pods -n app
    NAME                  READY   STATUS    RESTARTS   AGE
    app-5df5686c4-sl6dz   2/2     Running   0          119s
    
    $ kubectl logs -f -n app deployment/app app
    time="2020-02-18T14:26:01Z" level=info msg="Received new Vault token"
    time="2020-02-18T14:26:01Z" level=info msg="Initial Vault token arrived"
    s3cr3t
    going to sleep...
    

Scenario 2: Running Vault inside the mesh 🔗︎

To run Vault inside the mesh, complete the following steps. Note that these instructions assume that you have Scenario 1 up and running, and modifying it to run Vault inside the mesh.

  1. Turn off Istio in the app namespace by removing the istio-injection label:

    backyards sidecar-proxy auto-inject off app
    backyards sidecar-proxy auto-inject on vault
    
  2. Delete the Vault pods in the vault namespace, so they will get recreated with the istio-proxy sidecar:

    kubectl delete pods --all -n vault
    
  3. Check that they both come back with an extra container (4/4 and 2/2 now):

    $ kubectl get pods -n vault
    NAME                                READY   STATUS    RESTARTS   AGE
    vault-0                             4/4     Running   0          1m
    vault-configurer-6d9b98c856-l4flc   2/2     Running   0          1m
    
  4. Delete the application pods in the app namespace, so they will get recreated without the istio-proxy sidecar:

    kubectl delete pods --all -n app
    

The app pod got recreated with only the app container (1/1) and Vault access still works:

$ kubectl get pods -n app
NAME                  READY   STATUS    RESTARTS   AGE
app-5df5686c4-4n6r7   1/1     Running   0          71s

$ kubectl logs -f -n app deployment/app
time="2020-02-18T14:41:20Z" level=info msg="Received new Vault token"
time="2020-02-18T14:41:20Z" level=info msg="Initial Vault token arrived"
s3cr3t
going to sleep...

Scenario 3: both Vault and the app are running inside the mesh 🔗︎

In this scenario, both Vault and the app are running inside the mesh. You can configure this scenario right after completing the Prerequisites.

  1. Enable sidecar auto-injection for both namespaces:

    backyards sidecar-proxy auto-inject on app
    backyards sidecar-proxy auto-inject on vault
    
  2. Delete all pods so they are getting injected with the proxy:

    kubectl delete pods --all -n app
    kubectl delete pods --all -n vault
    
  3. Check the logs in the app container. It should sill show success:

    $ kubectl logs -f -n app deployment/app
    time="2020-02-18T15:04:03Z" level=info msg="Initial Vault token arrived"
    time="2020-02-18T15:04:03Z" level=info msg="Renewed Vault Token"
    s3cr3t
    going to sleep...
    

Conclusion 🔗︎

The Bank-Vaults alongside Istio feature, Backing up Vault with Velero, Vault replication across multiple datacenters and HSM support with the Bank-Vaults operator are three major features in the upcoming Bank-Vaults release, so stay tuned.

Update: since releasing Bank-Vaults 1.0, we also provide commercial support for Bank-Vaults. If you’re interested in commercial support, or anything else from our suite of products, make sure you get in touch with us, here.

To learn more about the Bank-Vaults operator and similar topics, subscribe to our newsletter. If you’re interested in contributing, check out the Bank-Vaults repository, or give us a GitHub star.

Learn more about Bank-Vaults:

About Backyards 🔗︎

Banzai Cloud’s Backyards is a multi and hybrid-cloud enabled service mesh platform for constructing modern applications. Built on Kubernetes, our Istio operator and the Banzai Cloud Pipeline platform gives you flexibility, portability, and consistency across on-premise datacenters and on five cloud environments. Use our simple, yet extremely powerful UI and CLI, and experience automated canary releases, traffic shifting, routing, secure service communication, in-depth observability and more, for yourself.