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This sample shows how Azure Front Door Premium can be set to use a Private Link Service to expose an AKS-hosted workload via NGINX Ingress Controller configured to use a private IP address on the internal load balancer.

License: MIT License

Shell 15.57% Bicep 84.43%

aks-front-door-private-link-service's Introduction

page_type languages products name description urlFragment azureDeploy
sample
azurecli
bicep
bash
csharp
yaml
json
azure
azure-front-door
azure-resource-manager
azure-kubernetes-service
azure-container-registry
azure-storage
azure-blob-storage
azure-storage-accounts
azure-bastion
azure-private-link
azure-virtual-network
azure-key-vault
azure-monitor
azure-log-analytics
azure-virtual-machines
How to expose NGINX Ingress Controller via Azure Front Door and Azure Private Link Service
This sample shows how Azure Front Door Premium can be set to use an Azure Private Link Service to expose an AKS-hosted workload via NGINX Ingress Controller configured to use a private IP address on the internal load balancer.
aks-api-server-vnet-integration-bicep

How to expose NGINX Ingress Controller via Azure Front Door and Azure Private Link Service

Azure Front Door Premium can connect to a backend application via Azure Private Link Service (PLS). For more information, see Secure your Origin with Private Link in Azure Front Door Premium.

This article shows how to use Azure Front Door Premium, Azure Web Application Firewall, and Azure Private Link Service (PLS) to securely expose and protect a workload running in Azure Kubernetes Service(AKS). The sample application is exposed via the NGINX Ingress Controller configured to use a private IP address as a frontend IP configuration of the kubernetes-internal internal load balancer. For more information, see Create an ingress controller using an internal IP address.

In addition, this sample shows how to deploy an Azure Kubernetes Service cluster with the API Server VNET Integration and how to use an Azure NAT Gateway to manage outbound connections initiated by AKS-hosted workloads. AKS clusters with API Server VNET integration provide a series of advantages, for example, they can have public network access or private cluster mode enabled or disabled without redeploying the cluster. For more information, see Create an Azure Kubernetes Service cluster with API Server VNet Integration.

Prerequisites

Architecture

This sample provides a set of Bicep modules to deploy and configure an Azure Front Door Premium with an WAF Policy as global load balancer in front of a public or a private AKS cluster with API Server VNET Integration, Azure CNI as a network plugin and Dynamic IP Allocation. The following diagram shows the architecture and network topology deployed by the sample:

AKS Architecture

A Deployment Script is used to create the NGINX Ingress Controller, configured to use a private IP address as frontend IP configuration of the kubernetes-internal internal load balancer, via Helm and a sample httpbin web application via YAML manifests. The Origin child resource of the Azure Front Door Premium global load balancer is configured to call the sample application via Azure Private Link Service, the AKS the kubernetes-internal internal load balancer, and the NGINX Ingress Controller, as shown in the following figure:

Message Flow

Bicep modules are parametric, so you can choose any network plugin:

NOTE
The sample was tested only with Azure CNI and Azure CNI Overlay

The Bicep modules also allow installing the following extensions and add-ons for Azure Kubernetes Service(AKS):

In a production environment, we strongly recommend deploying a private AKS cluster with Uptime SLA. For more information, see private AKS cluster with a Public DNS address. Alternatively, you can deploy a public AKS cluster and secure access to the API server using authorized IP address ranges.

The Bicep modules deploy the following Azure resources:

NOTE
You can find the architecture.vsdx file used for the diagram under the visio folder.

What is Bicep?

Bicep is a domain-specific language (DSL) that uses a declarative syntax to deploy Azure resources. It provides concise syntax, reliable type safety, and support for code reuse. Bicep offers the best authoring experience for your infrastructure-as-code solutions in Azure.

Deploy the Bicep modules

You can deploy the Bicep modules in the bicep folder using the deploy.sh Bash script in the same folder. Specify a value for the following parameters in the deploy.sh script and main.parameters.json parameters file before deploying the Bicep modules.

  • prefix: specifies a prefix for all the Azure resources.
  • authenticationType: specifies the type of authentication when accessing the Virtual Machine. sshPublicKey is the recommended value. Allowed values: sshPublicKey and password.
  • vmAdminUsername: specifies the name of the administrator account of the virtual machine.
  • vmAdminPasswordOrKey: specifies the SSH Key or password for the virtual machine.
  • aksClusterSshPublicKey: specifies the SSH Key or password for AKS cluster agent nodes.
  • aadProfileAdminGroupObjectIDs: when deploying an AKS cluster with Azure AD and Azure RBAC integration, this array parameter contains the list of Azure AD group object IDs that will have the admin role of the cluster.
  • keyVaultObjectIds: Specifies the object ID of the service principals to configure in Key Vault access policies.

We suggest reading sensitive configuration data such as passwords or SSH keys from a pre-existing Azure Key Vault resource. For more information, see Use Azure Key Vault to pass secure parameter value during Bicep deployment.

#!/bin/bash

# Template
template="main.bicep"
parameters="main.parameters.json"

# AKS cluster name
prefix="<Azure-Resource-Name-Prefix>"
aksName="${prefix}Aks"
validateTemplate=1
useWhatIf=0
update=1
installExtensions=0

# Name and location of the resource group for the Azure Kubernetes Service (AKS) cluster
resourceGroupName="${prefix}RG"
location="westeurope"
deploymentName="main"

# Subscription id, subscription name, and tenant id of the current subscription
subscriptionId=$(az account show --query id --output tsv)
subscriptionName=$(az account show --query name --output tsv)
tenantId=$(az account show --query tenantId --output tsv)

# Install aks-preview Azure extension
if [[ $installExtensions == 1 ]]; then
  echo "Checking if [aks-preview] extension is already installed..."
  az extension show --name aks-preview &>/dev/null

  if [[ $? == 0 ]]; then
    echo "[aks-preview] extension is already installed"

    # Update the extension to make sure you have the latest version installed
    echo "Updating [aks-preview] extension..."
    az extension update --name aks-preview &>/dev/null
  else
    echo "[aks-preview] extension is not installed. Installing..."

    # Install aks-preview extension
    az extension add --name aks-preview 1>/dev/null

    if [[ $? == 0 ]]; then
      echo "[aks-preview] extension successfully installed"
    else
      echo "Failed to install [aks-preview] extension"
      exit
    fi
  fi

  # Registering AKS feature extensions
  aksExtensions=(
    "PodSecurityPolicyPreview"
    "KubeletDisk"
    "AKS-KedaPreview"
    "RunCommandPreview"
    "EnablePodIdentityPreview "
    "UserAssignedIdentityPreview"
    "EnablePrivateClusterPublicFQDN"
    "PodSubnetPreview"
    "EnableOIDCIssuerPreview"
    "EnableWorkloadIdentityPreview"
    "EnableImageCleanerPreview"
    "AKS-VPAPreview"
    "AzureOverlayPreview"
    "KubeProxyConfigurationPreview"
  )
  ok=0
  registeringExtensions=()
  for aksExtension in ${aksExtensions[@]}; do
    echo "Checking if [$aksExtension] extension is already registered..."
    extension=$(az feature list -o table --query "[?contains(name, 'Microsoft.ContainerService/$aksExtension') && @.properties.state == 'Registered'].{Name:name}" --output tsv)
    if [[ -z $extension ]]; then
      echo "[$aksExtension] extension is not registered."
      echo "Registering [$aksExtension] extension..."
      az feature register --name $aksExtension --namespace Microsoft.ContainerService
      registeringExtensions+=("$aksExtension")
      ok=1
    else
      echo "[$aksExtension] extension is already registered."
    fi
  done
  echo $registeringExtensions
  delay=1
  for aksExtension in ${registeringExtensions[@]}; do
    echo -n "Checking if [$aksExtension] extension is already registered..."
    while true; do
      extension=$(az feature list -o table --query "[?contains(name, 'Microsoft.ContainerService/$aksExtension') && @.properties.state == 'Registered'].{Name:name}" --output tsv)
      if [[ -z $extension ]]; then
        echo -n "."
        sleep $delay
      else
        echo "."
        break
      fi
    done
  done

  if [[ $ok == 1 ]]; then
    echo "Refreshing the registration of the Microsoft.ContainerService resource provider..."
    az provider register --namespace Microsoft.ContainerService
    echo "Microsoft.ContainerService resource provider registration successfully refreshed"
  fi
fi

# Get the last Kubernetes version available in the region
kubernetesVersion=$(az aks get-versions --location $location --query "orchestrators[?isPreview==false].orchestratorVersion | sort(@) | [-1]" --output tsv)

if [[ -n $kubernetesVersion ]]; then
  echo "Successfully retrieved the last Kubernetes version [$kubernetesVersion] supported by AKS in [$location] Azure region"
else
  echo "Failed to retrieve the last Kubernetes version supported by AKS in [$location] Azure region"
  exit
fi

# Check if the resource group already exists
echo "Checking if [$resourceGroupName] resource group actually exists in the [$subscriptionName] subscription..."

az group show --name $resourceGroupName &>/dev/null

if [[ $? != 0 ]]; then
  echo "No [$resourceGroupName] resource group actually exists in the [$subscriptionName] subscription"
  echo "Creating [$resourceGroupName] resource group in the [$subscriptionName] subscription..."

  # Create the resource group
  az group create --name $resourceGroupName --location $location 1>/dev/null

  if [[ $? == 0 ]]; then
    echo "[$resourceGroupName] resource group successfully created in the [$subscriptionName] subscription"
  else
    echo "Failed to create [$resourceGroupName] resource group in the [$subscriptionName] subscription"
    exit
  fi
else
  echo "[$resourceGroupName] resource group already exists in the [$subscriptionName] subscription"
fi

# Create AKS cluster if does not exist
echo "Checking if [$aksName] aks cluster actually exists in the [$resourceGroupName] resource group..."

az aks show --name $aksName --resource-group $resourceGroupName &>/dev/null
notExists=$?

if [[ $notExists != 0 || $update == 1 ]]; then

  if [[ $notExists != 0 ]]; then
    echo "No [$aksName] aks cluster actually exists in the [$resourceGroupName] resource group"
  else
    echo "[$aksName] aks cluster already exists in the [$resourceGroupName] resource group. Updating the cluster..."
  fi

  # Delete any existing role assignments for the user-defined managed identity of the AKS cluster
  # in case you are re-deploying the solution in an existing resource group
  echo "Retrieving the list of role assignments on [$resourceGroupName] resource group..."
  assignmentIds=$(az role assignment list \
    --scope "/subscriptions/${subscriptionId}/resourceGroups/${resourceGroupName}" \
    --query [].id \
    --output tsv \
    --only-show-errors)

  if [[ -n $assignmentIds ]]; then
    echo "[${#assignmentIds[@]}] role assignments have been found on [$resourceGroupName] resource group"
    for assignmentId in ${assignmentIds[@]}; do
      if [[ -n $assignmentId ]]; then
        az role assignment delete --ids $assignmentId

        if [[ $? == 0 ]]; then
          assignmentName=$(echo $assignmentId | awk -F '/' '{print $NF}')
          echo "[$assignmentName] role assignment on [$resourceGroupName] resource group successfully deleted"
        fi
      fi
    done
  else
    echo "No role assignment actually exists on [$resourceGroupName] resource group"
  fi

  # Get the kubelet managed identity used by the AKS cluster
  echo "Retrieving the kubelet identity from the [$aksName] AKS cluster..."
  clientId=$(az aks show \
    --name $aksName \
    --resource-group $resourceGroupName \
    --query identityProfile.kubeletidentity.clientId \
    --output tsv 2>/dev/null)

  if [[ -n $clientId ]]; then
    # Delete any role assignment to kubelet managed identity on any ACR in the resource group
    echo "kubelet identity of the [$aksName] AKS cluster successfully retrieved"
    echo "Retrieving the list of ACR resources in the [$resourceGroupName] resource group..."
    acrIds=$(az acr list \
      --resource-group $resourceGroupName \
      --query [].id \
      --output tsv)

    if [[ -n $acrIds ]]; then
      echo "[${#acrIds[@]}] ACR resources have been found in [$resourceGroupName] resource group"
      for acrId in ${acrIds[@]}; do
        if [[ -n $acrId ]]; then
          acrName=$(echo $acrId | awk -F '/' '{print $NF}')
          echo "Retrieving the list of role assignments on [$acrName] ACR..."
          assignmentIds=$(az role assignment list \
            --scope "$acrId" \
            --query [].id \
            --output tsv \
            --only-show-errors)

          if [[ -n $assignmentIds ]]; then
            echo "[${#assignmentIds[@]}] role assignments have been found on [$acrName] ACR"
            for assignmentId in ${assignmentIds[@]}; do
              if [[ -n $assignmentId ]]; then
                az role assignment delete --ids $assignmentId

                if [[ $? == 0 ]]; then
                  assignmentName=$(echo $assignmentId | awk -F '/' '{print $NF}')
                  echo "[$assignmentName] role assignment on [$acrName] ACR successfully deleted"
                fi
              fi
            done
          else
            echo "No role assignment actually exists on [$acrName] ACR"
          fi
        fi
      done
    else
      echo "No ACR actually exists in [$resourceGroupName] resource group"
    fi
  else
    echo "No kubelet identity exists for the [$aksName] AKS cluster"
  fi

  # Validate the Bicep template
  if [[ $validateTemplate == 1 ]]; then
    if [[ $useWhatIf == 1 ]]; then
      # Execute a deployment What-If operation at resource group scope.
      echo "Previewing changes deployed by [$template] Bicep template..."
      az deployment group what-if \
        --resource-group $resourceGroupName \
        --template-file $template \
        --parameters $parameters \
        --parameters prefix=$prefix \
        location=$location \
        aksClusterKubernetesVersion=$kubernetesVersion

      if [[ $? == 0 ]]; then
        echo "[$template] Bicep template validation succeeded"
      else
        echo "Failed to validate [$template] Bicep template"
        exit
      fi
    else
      # Validate the Bicep template
      echo "Validating [$template] Bicep template..."
      output=$(az deployment group validate \
        --resource-group $resourceGroupName \
        --template-file $template \
        --parameters $parameters \
        --parameters prefix=$prefix \
        location=$location \
        aksClusterKubernetesVersion=$kubernetesVersion)

      if [[ $? == 0 ]]; then
        echo "[$template] Bicep template validation succeeded"
      else
        echo "Failed to validate [$template] Bicep template"
        echo $output
        exit
      fi
    fi
  fi

  # Deploy the Bicep template
  echo "Deploying [$template] Bicep template..."
  az deployment group create \
    --name $deploymentName \
    --resource-group $resourceGroupName \
    --only-show-errors \
    --template-file $template \
    --parameters $parameters \
    --parameters prefix=$prefix \
    location=$location \
    aksClusterKubernetesVersion=$kubernetesVersion 1>/dev/null

  if [[ $? == 0 ]]; then
    echo "[$template] Bicep template successfully provisioned"
  else
    echo "Failed to provision the [$template] Bicep template"
    exit
  fi
else
  echo "[$aksName] aks cluster already exists in the [$resourceGroupName] resource group"
fi

# Create AKS cluster if does not exist
echo "Checking if [$aksName] aks cluster actually exists in the [$resourceGroupName] resource group..."

az aks show --name $aksName --resource-group $resourceGroupName &>/dev/null

if [[ $? != 0 ]]; then
  echo "No [$aksName] aks cluster actually exists in the [$resourceGroupName] resource group"
  exit
fi

# Get the user principal name of the current user
echo "Retrieving the user principal name of the current user from the [$tenantId] Azure AD tenant..."
userPrincipalName=$(az account show --query user.name --output tsv)
if [[ -n $userPrincipalName ]]; then
  echo "[$userPrincipalName] user principal name successfully retrieved from the [$tenantId] Azure AD tenant"
else
  echo "Failed to retrieve the user principal name of the current user from the [$tenantId] Azure AD tenant"
  exit
fi

# Retrieve the objectId of the user in the Azure AD tenant used by AKS for user authentication
echo "Retrieving the objectId of the [$userPrincipalName] user principal name from the [$tenantId] Azure AD tenant..."
userObjectId=$(az ad user show --id $userPrincipalName --query id --output tsv 2>/dev/null)

if [[ -n $userObjectId ]]; then
  echo "[$userObjectId] objectId successfully retrieved for the [$userPrincipalName] user principal name"
else
  echo "Failed to retrieve the objectId of the [$userPrincipalName] user principal name"
  exit
fi

# Retrieve the resource id of the AKS cluster
echo "Retrieving the resource id of the [$aksName] AKS cluster..."
aksClusterId=$(az aks show \
  --name "$aksName" \
  --resource-group "$resourceGroupName" \
  --query id \
  --output tsv 2>/dev/null)

if [[ -n $aksClusterId ]]; then
  echo "Resource id of the [$aksName] AKS cluster successfully retrieved"
else
  echo "Failed to retrieve the resource id of the [$aksName] AKS cluster"
  exit
fi

# Assign Azure Kubernetes Service RBAC Cluster Admin role to the current user
role="Azure Kubernetes Service RBAC Cluster Admin"
echo "Checking if [$userPrincipalName] user has been assigned to [$role] role on the [$aksName] AKS cluster..."
current=$(az role assignment list \
  --assignee $userObjectId \
  --scope $aksClusterId \
  --query "[?roleDefinitionName=='$role'].roleDefinitionName" \
  --output tsv 2>/dev/null)

if [[ $current == "Owner" ]] || [[ $current == "Contributor" ]] || [[ $current == "$role" ]]; then
  echo "[$userPrincipalName] user is already assigned to the [$current] role on the [$aksName] AKS cluster"
else
  echo "[$userPrincipalName] user is not assigned to the [$role] role on the [$aksName] AKS cluster"
  echo "Assigning the [$userPrincipalName] user to the [$role] role on the [$aksName] AKS cluster..."

  az role assignment create \
    --role "$role" \
    --assignee $userObjectId \
    --scope $aksClusterId \
    --only-show-errors 1>/dev/null

  if [[ $? == 0 ]]; then
    echo "[$userPrincipalName] user successfully assigned to the [$role] role on the [$aksName] AKS cluster"
  else
    echo "Failed to assign the [$userPrincipalName] user to the [$role] role on the [$aksName] AKS cluster"
    exit
  fi
fi

# Assign Azure Kubernetes Service Cluster Admin Role role to the current user
role="Azure Kubernetes Service Cluster Admin Role"
echo "Checking if [$userPrincipalName] user has been assigned to [$role] role on the [$aksName] AKS cluster..."
current=$(az role assignment list \
  --assignee $userObjectId \
  --scope $aksClusterId \
  --query "[?roleDefinitionName=='$role'].roleDefinitionName" \
  --output tsv 2>/dev/null)

if [[ $current == "Owner" ]] || [[ $current == "Contributor" ]] || [[ $current == "$role" ]]; then
  echo "[$userPrincipalName] user is already assigned to the [$current] role on the [$aksName] AKS cluster"
else
  echo "[$userPrincipalName] user is not assigned to the [$role] role on the [$aksName] AKS cluster"
  echo "Assigning the [$userPrincipalName] user to the [$role] role on the [$aksName] AKS cluster..."

  az role assignment create \
    --role "$role" \
    --assignee $userObjectId \
    --scope $aksClusterId \
    --only-show-errors 1>/dev/null

  if [[ $? == 0 ]]; then
    echo "[$userPrincipalName] user successfully assigned to the [$role] role on the [$aksName] AKS cluster"
  else
    echo "Failed to assign the [$userPrincipalName] user to the [$role] role on the [$aksName] AKS cluster"
    exit
  fi
fi

# Get the FQDN of the Azure Front Door endpoint
azureFrontDoorEndpointFqdn=$(az deployment group show \
 --name $deploymentName \
 --resource-group $resourceGroupName \
 --query properties.outputs.frontDoorEndpointFqdn.value \
 --output tsv)

if [[ -n $azureFrontDoorEndpointFqdn ]]; then
 echo "FQDN of the Azure Front Door endpoint: $azureFrontDoorEndpointFqdn"
else
 echo "Failed to get the FQDN of the Azure Front Door endpoint"
 exit -1
fi

# Get the private link service name
privateLinkServiceName=$(az deployment group show \
 --name $deploymentName \
 --resource-group $resourceGroupName \
 --query properties.outputs.privateLinkServiceName.value \
 --output tsv)

if [[ -z $privateLinkServiceName ]]; then
 echo "Failed to get the private link service name"
 exit -1
fi

# Get the resource id of the Private Endpoint Connection
privateEndpointConnectionId=$(az network private-endpoint-connection list \
 --name $privateLinkServiceName \
 --resource-group $resourceGroupName \
 --type Microsoft.Network/privateLinkServices \
 --query [0].id \
 --output tsv)

if [[ -n $privateEndpointConnectionId ]]; then
 echo "Resource id of the Private Endpoint Connection: $privateEndpointConnectionId"
else
 echo "Failed to get the resource id of the Private Endpoint Connection"
 exit -1
fi

# Approve the private endpoint connection
echo "Approving [$privateEndpointConnectionId] private endpoint connection ID..."
az network private-endpoint-connection approve \
 --name $privateLinkServiceName \
 --resource-group $resourceGroupName \
 --id $privateEndpointConnectionId \
 --description "Approved" 1>/dev/null

if [[ $? == 0 ]]; then
 echo "[$privateEndpointConnectionId] private endpoint connection ID successfully approved"
else
 echo "Failed to approve [$privateEndpointConnectionId] private endpoint connection ID"
 exit -1
fi

The last steps of the Bash script perform the following actions:

If you miss running these steps, Azure Front Door cannot invoke the httpbin web application via the Azure Private Link Service, and the kubernetes-internal internal load balancer of the AKS cluster.

Deployment Script

The sample makes use of a Deployment Script to run the install-helm-charts-and-app.sh Bash script which installs the httpbin web application via YAML templates and the following packages to the AKS cluster via Helm. For more information on deployment scripts, see Use deployment scripts in Bicep

# Install kubectl
az aks install-cli --only-show-errors

# Get AKS credentials
az aks get-credentials \
  --admin \
  --name $clusterName \
  --resource-group $resourceGroupName \
  --subscription $subscriptionId \
  --only-show-errors

# Check if the cluster is private or not
private=$(az aks show --name $clusterName \
  --resource-group $resourceGroupName \
  --subscription $subscriptionId \
  --query apiServerAccessProfile.enablePrivateCluster \
  --output tsv)

# Install Helm
curl https://raw.githubusercontent.com/helm/helm/main/scripts/get-helm-3 -o get_helm.sh -s
chmod 700 get_helm.sh
./get_helm.sh &>/dev/null

# Add Helm repos
helm repo add prometheus-community https://prometheus-community.github.io/helm-charts
helm repo add ingress-nginx https://kubernetes.github.io/ingress-nginx
helm repo add jetstack https://charts.jetstack.io

# Update Helm repos
helm repo update

if [[ $private == 'true' ]]; then
  # Log whether the cluster is public or private
  echo "$clusterName AKS cluster is public"

  # Install Prometheus
  command="helm install prometheus prometheus-community/kube-prometheus-stack \
  --create-namespace \
  --namespace prometheus \
  --set prometheus.prometheusSpec.podMonitorSelectorNilUsesHelmValues=false \
  --set prometheus.prometheusSpec.serviceMonitorSelectorNilUsesHelmValues=false"

  az aks command invoke \
    --name $clusterName \
    --resource-group $resourceGroupName \
    --subscription $subscriptionId \
    --command "$command"

  # Install NGINX ingress controller using the internal load balancer
  command="helm install nginx-ingress ingress-nginx/ingress-nginx \
    --create-namespace \
    --namespace ingress-basic \
    --set controller.config.enable-modsecurity=true \
    --set controller.config.enable-owasp-modsecurity-crs=true \
    --set controller.config.modsecurity-snippet=\
'SecRuleEngine On
SecRequestBodyAccess On
SecAuditLog /dev/stdout
SecAuditLogFormat JSON
SecAuditEngine RelevantOnly' \
    --set controller.replicaCount=3 \
    --set controller.nodeSelector.\"kubernetes\.io/os\"=linux \
    --set defaultBackend.nodeSelector.\"kubernetes\.io/os\"=linux \
    --set controller.metrics.enabled=true \
    --set controller.metrics.serviceMonitor.enabled=true \
    --set controller.metrics.serviceMonitor.additionalLabels.release=\"prometheus\" \
    --set controller.service.annotations.\"service\.beta\.kubernetes\.io/azure-load-balancer-health-probe-request-path\"=/healthz \
    --set controller.service.annotations.\"service\.beta\.kubernetes\.io/azure-load-balancer-internal\"=true"

  az aks command invoke \
    --name $clusterName \
    --resource-group $resourceGroupName \
    --subscription $subscriptionId \
    --command "$command"

  # Install certificate manager
  command="helm install cert-manager jetstack/cert-manager \
    --create-namespace \
    --namespace cert-manager \
    --set installCRDs=true \
    --set nodeSelector.\"kubernetes\.io/os\"=linux"

  az aks command invoke \
    --name $clusterName \
    --resource-group $resourceGroupName \
    --subscription $subscriptionId \
    --command "$command"

  # Create cluster issuer
  command="cat <<EOF | kubectl apply -f -
apiVersion: cert-manager.io/v1
kind: ClusterIssuer
metadata:
  name: letsencrypt-nginx
spec:
  acme:
    server: https://acme-v02.api.letsencrypt.org/directory
    email: $email
    privateKeySecretRef:
      name: letsencrypt
    solvers:
    - http01:
        ingress:
          class: nginx
          podTemplate:
            spec:
              nodeSelector:
                "kubernetes.io/os": linux
EOF"

  az aks command invoke \
    --name $clusterName \
    --resource-group $resourceGroupName \
    --subscription $subscriptionId \
    --command "$command"

  # Create a namespace for the application
  command="kubectl create namespace $namespace"

  az aks command invoke \
    --name $clusterName \
    --resource-group $resourceGroupName \
    --subscription $subscriptionId \
    --command "$command"

  # Create a deployment and service for the application
  command="cat <<EOF | kubectl apply -n $namespace -f -
apiVersion: apps/v1
kind: Deployment
metadata:
  name: httpbin
spec:
  replicas: 3
  selector:
    matchLabels:
      app: httpbin
  template:
    metadata:
      labels:
        app: httpbin
    spec:
      topologySpreadConstraints:
      - maxSkew: 1
        topologyKey: topology.kubernetes.io/zone
        whenUnsatisfiable: DoNotSchedule
        labelSelector:
          matchLabels:
            app: httpbin
      - maxSkew: 1
        topologyKey: kubernetes.io/hostname
        whenUnsatisfiable: DoNotSchedule
        labelSelector:
          matchLabels:
            app: httpbin
      nodeSelector:
        "kubernetes.io/os": linux
      containers:
      - image: docker.io/kennethreitz/httpbin
        imagePullPolicy: IfNotPresent
        name: httpbin
        resources:
          requests:
            memory: "64Mi"
            cpu: "125m"
          limits:
            memory: "128Mi"
            cpu: "250m"
        ports:
        - containerPort: 80
        env:
        - name: PORT
          value: "80"
---
apiVersion: v1
kind: Service
metadata:
  name: httpbin
spec:
  ports:
    - port: 80
      targetPort: 80
      protocol: TCP
  type: ClusterIP
  selector:
    app: httpbin
EOF"

  az aks command invoke \
    --name $clusterName \
    --resource-group $resourceGroupName \
    --subscription $subscriptionId \
    --command "$command"

  # Create an ingress resource for the application
  command="cat <<EOF | kubectl apply -n $namespace -f -
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: httpbin
spec:
  ingressClassName: nginx
  rules:
  - host: $hostName
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: httpbin
            port:
              number: 80
EOF"

  az aks command invoke \
    --name $clusterName \
    --resource-group $resourceGroupName \
    --subscription $subscriptionId \
    --command "$command"

else
  # Log whether the cluster is public or private
  echo "$clusterName AKS cluster is private"

  # Install Prometheus
  helm install prometheus prometheus-community/kube-prometheus-stack \
    --create-namespace \
    --namespace prometheus \
    --set prometheus.prometheusSpec.podMonitorSelectorNilUsesHelmValues=false \
    --set prometheus.prometheusSpec.serviceMonitorSelectorNilUsesHelmValues=false

  # Install NGINX ingress controller using the internal load balancer
  helm install nginx-ingress ingress-nginx/ingress-nginx \
    --create-namespace \
    --namespace ingress-basic \
    --set controller.config.enable-modsecurity=true \
    --set controller.config.enable-owasp-modsecurity-crs=true \
    --set controller.config.modsecurity-snippet='SecRuleEngine On
SecRequestBodyAccess On
SecAuditLog /dev/stdout
SecAuditLogFormat JSON
SecAuditEngine RelevantOnly' \
    --set controller.replicaCount=3 \
    --set controller.nodeSelector."kubernetes\.io/os"=linux \
    --set defaultBackend.nodeSelector."kubernetes\.io/os"=linux \
    --set controller.metrics.enabled=true \
    --set controller.metrics.serviceMonitor.enabled=true \
    --set controller.metrics.serviceMonitor.additionalLabels.release="prometheus" \
    --set controller.service.annotations."service\.beta\.kubernetes\.io/azure-load-balancer-health-probe-request-path"=/healthz \
    --set controller.service.annotations."service\.beta\.kubernetes\.io/azure-load-balancer-internal"=true

  helm install $nginxReleaseName $nginxRepoName/$nginxChartName \
    --create-namespace \
    --namespace $nginxNamespace

  # Install certificate manager
  helm install cert-manager jetstack/cert-manager \
    --create-namespace \
    --namespace cert-manager \
    --set installCRDs=true \
    --set nodeSelector."kubernetes\.io/os"=linux

  # Create cluster issuer
  cat <<EOF | kubectl apply -f -
apiVersion: cert-manager.io/v1
kind: ClusterIssuer
metadata:
  name: letsencrypt-nginx
spec:
  acme:
    server: https://acme-v02.api.letsencrypt.org/directory
    email: $email
    privateKeySecretRef:
      name: letsencrypt
    solvers:
    - http01:
        ingress:
          class: nginx
          podTemplate:
            spec:
              nodeSelector:
                "kubernetes.io/os": linux
EOF

  # Create a namespace for the application
  kubectl create namespace $namespace

  # Create a deployment and service for the application
  cat <<EOF | kubectl apply -n $namespace -f -
apiVersion: apps/v1
kind: Deployment
metadata:
  name: httpbin
spec:
  replicas: 3
  selector:
    matchLabels:
      app: httpbin
  template:
    metadata:
      labels:
        app: httpbin
    spec:
      topologySpreadConstraints:
      - maxSkew: 1
        topologyKey: topology.kubernetes.io/zone
        whenUnsatisfiable: DoNotSchedule
        labelSelector:
          matchLabels:
            app: httpbin
      - maxSkew: 1
        topologyKey: kubernetes.io/hostname
        whenUnsatisfiable: DoNotSchedule
        labelSelector:
          matchLabels:
            app: httpbin
      nodeSelector:
        "kubernetes.io/os": linux
      containers:
      - image: docker.io/kennethreitz/httpbin
        imagePullPolicy: IfNotPresent
        name: httpbin
        resources:
          requests:
            memory: "64Mi"
            cpu: "125m"
          limits:
            memory: "128Mi"
            cpu: "250m"
        ports:
        - containerPort: 80
        env:
        - name: PORT
          value: "80"
---
apiVersion: v1
kind: Service
metadata:
  name: httpbin
spec:
  ports:
    - port: 80
      targetPort: 80
      protocol: TCP
  type: ClusterIP
  selector:
    app: httpbin
EOF

  # Create an ingress resource for the application
  cat <<EOF | kubectl apply -n $namespace -f -
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: httpbin
spec:
  ingressClassName: nginx
  rules:
  - host: $hostName
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: httpbin
            port:
              number: 80
EOF

fi

# Create output as JSON file
echo '{}' |
  jq --arg x 'prometheus' '.prometheus=$x' |
  jq --arg x 'cert-manager' '.certManager=$x' |
  jq --arg x 'ingress-basic' '.nginxIngressController=$x' >$AZ_SCRIPTS_OUTPUT_PATH

As you can note, when deploying the NGINX Ingress Controller via Helm, the service.beta.kubernetes.io/azure-load-balancer-internal to create the kubernetes-internal internal load balancer in the node resource group of the AKS cluster and expose the ingress controller service via a private IP address.

In this sample, the httpbin web application via YAML templates. In particular, an ingress is used to expose the application via the NGINX Ingress Controller via the HTTP protocol and using the httpbin.local hostname. The ingress object can be easily modified to expose the server via HTTPS and provide a certificate for TLS termination. You can use the cert-manager to issue a Let's Encrypt certificate. For more information, see Securing NGINX-ingress. In particular, cert-manager can create and then delete DNS-01 records in Azure DNS but it needs to authenticate to Azure first. The suggested authentication method is Managed Identity Using AAD Workload Identity.

Alternative Solution

Azure Private Link Service (PLS) is an infrastructure component that allows users to privately connect via an Azure Private Endpoint (PE) in a virtual network in Azure and a Frontend IP Configuration associated with an internal or public Azure Load Balancer (ALB). With Private Link, users as service providers can securely provide their services to consumers who can connect from within Azure or on-premises without data exfiltration risks.

Before Private Link Service integration, users who wanted private connectivity from on-premises or other virtual networks to their services in an Azure Kubernetes Service(AKS) cluster were required to create a Private Link Service (PLS) to reference the cluster Azure Load Balancer, like in this sample. The user would then create an Azure Private Endpoint (PE) to connect to the PLS to enable private connectivity. With the Azure Private Link Service Integration feature, a managed Azure Private Link Service (PLS) to the AKS cluster load balancer can be created automatically, and the user would only be required to create Private Endpoint connections to it for private connectivity. You can expose a Kubernetes service via a Private Link Service using annotations. For more information, see Azure Private Link Service Integration.

CI/CD and GitOps Considerations

Azure Private Link Service Integration simplifies the creation of a Azure Private Link Service (PLS) when deploying Kubernetes services or ingress controllers via a classic CI/CD pipeline using Azure DevOps, GitHub Actions, Jenkins, or GitLab, but even when using a GitOps approach with Argo CD or Flux v2.

For every workload that you expose via Azure Private Link Service (PLS) and Azure Front Door Premium, you need to create - Microsoft.Cdn/profiles/originGroups: an Origin Group, an Origin, endpoint, a route, and a security policy if you want to protect the workload with a WAF policy. You can accomplish this task using [az network front-door](az network front-door) Azure CLI commands in the CD pipeline used to deploy your service.

Test the application

If the deployment succeeds, and the private endpoint connection from the Azure Front Door Premium instance to the Azure Private Link Service (PLS) is approved, you should be able to access the AKS-hosted httpbin web application as follows:

  • Navigate to the overview page of your Front Door Premium in the Azure Portal and copy the URL from the Endpoint hostname, as shown in the following picture

Azure Front Door Premium in the Azure Portal

  • Paste and open the URL in your favorite internet browser. You should see the user interface of the httpbin application:

HTTPBIN application

You can use the bicep/calls.sh Bash script to simulate a few attacks and see the managed rule set and custom rule of the Azure Web Application Firewall in action.

#!/bin/bash

# Variables
url="<Front Door Endpoint Hostname URL>"

# Call REST API
echo "Calling REST API..."
curl -I -s "$url"

# Simulate SQL injection
echo "Simulating SQL injection..."
curl -I -s "${url}?users=ExampleSQLInjection%27%20--"

# Simulate XSS
echo "Simulating XSS..."
curl -I -s "${url}?users=ExampleXSS%3Cscript%3Ealert%28%27XSS%27%29%3C%2Fscript%3E"

# A custom rule blocks any request with the word blockme in the querystring.
echo "Simulating query string manipulation with the 'attack' word in the query string..."
curl -I -s "${url}?task=blockme"

The Bash script should produce the following output, where the first call succeeds, while the remaining one are blocked by the WAF Policy configured in prevention mode.

Calling REST API...
HTTP/2 200
content-length: 9593
content-type: text/html; charset=utf-8
accept-ranges: bytes
vary: Accept-Encoding
access-control-allow-origin: *
access-control-allow-credentials: true
x-azure-ref: 05mwQZAAAAADma91JbmU0TJqRqS2lyFurTUlMMzBFREdFMDYwOQA3YTk2NzZiMS0xZmRjLTQ0OWYtYmI1My1hNDUxMDVjNGZmYmM=
x-cache: CONFIG_NOCACHE
date: Tue, 14 Mar 2023 12:47:33 GMT

Simulating SQL injection...
HTTP/2 403
x-azure-ref: 05mwQZAAAAABaQCSGQToQT4tifYGpmsTmTUlMMzBFREdFMDYxNQA3YTk2NzZiMS0xZmRjLTQ0OWYtYmI1My1hNDUxMDVjNGZmYmM=
date: Tue, 14 Mar 2023 12:47:34 GMT

Simulating XSS...
HTTP/2 403
x-azure-ref: 05mwQZAAAAAAJZzCrTmN4TLY+bZOxskzOTUlMMzBFREdFMDYxMwA3YTk2NzZiMS0xZmRjLTQ0OWYtYmI1My1hNDUxMDVjNGZmYmM=
date: Tue, 14 Mar 2023 12:47:33 GMT

Simulating query string manipulation with the 'attack' word in the query string...
HTTP/2 403
x-azure-ref: 05mwQZAAAAADAle0hOg4FTYH6Q1LHIP50TUlMMzBFREdFMDYyMAA3YTk2NzZiMS0xZmRjLTQ0OWYtYmI1My1hNDUxMDVjNGZmYmM=
date: Tue, 14 Mar 2023 12:47:33 GMT

Front Door WAF Policies and Application Gateway WAF policies can be configured to run in the following two modes:

  • Detection mode: When run in detection mode, WAF doesn't take any other actions other than monitors and logs the request and its matched WAF rule to WAF logs. You can turn on logging diagnostics for Front Door. When you use the portal, go to the Diagnostics section.

  • Prevention mode: In prevention mode, WAF takes the specified action if a request matches a rule. If a match is found, no further rules with lower priority are evaluated. Any matched requests are also logged in the WAF logs.

For more information, see Azure Web Application Firewall on Azure Front Door.

Review deployed resources

Use the Azure portal, Azure CLI, or Azure PowerShell to list the deployed resources in the resource group.

Azure CLI

az resource list --resource-group <resource-group-name>

PowerShell

Get-AzResource -ResourceGroupName <resource-group-name>

Clean up resources

When you no longer need the resources you created, just delete the resource group. This will remove all the Azure resources.

Azure CLI

az group delete --name <resource-group-name>

PowerShell

Remove-AzResourceGroup -Name <resource-group-name>

Next Steps

You could add a custom domain to your Front Door. If you use Azure DNS to manage your domain, you could extend the Bicep modules to automatically create a custom domain for your Front Door and create a CNAME DNS record in your public DNS zone.

aks-front-door-private-link-service's People

Contributors

iamaliyousefi avatar microsoftopensource avatar paolosalvatori avatar

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