Secure ingress gateway for Istio service mesh add-on for Azure Kubernetes Service

Article
05/09/2024

The Deploy external or internal Istio Ingress article describes how to configure an ingress gateway to expose an HTTP service to external/internal traffic. This article shows how to expose a secure HTTPS service using either simple or mutual TLS.

Prerequisites

Enable the Istio add-on on the cluster as per documentation
Deploy an external Istio ingress gateway as per documentation
- Enable external ingress gateway

Note

This article refers to the external ingress gateway for demonstration, same steps would apply for configuring mutual TLS for internal ingress gateway.

Required client/server certificates and keys

This article requires several certificates and keys. You can use your favorite tool to create them or you can use the following openssl commands.

Create a root certificate and private key for signing the certificates for sample services:

mkdir bookinfo_certs
openssl req -x509 -sha256 -nodes -days 365 -newkey rsa:2048 -subj '/O=bookinfo Inc./CN=bookinfo.com' -keyout bookinfo_certs/bookinfo.com.key -out bookinfo_certs/bookinfo.com.crt

Generate a certificate and private key for productpage.bookinfo.com:

openssl req -out bookinfo_certs/productpage.bookinfo.com.csr -newkey rsa:2048 -nodes -keyout bookinfo_certs/productpage.bookinfo.com.key -subj "/CN=productpage.bookinfo.com/O=product organization"
openssl x509 -req -sha256 -days 365 -CA bookinfo_certs/bookinfo.com.crt -CAkey bookinfo_certs/bookinfo.com.key -set_serial 0 -in bookinfo_certs/productpage.bookinfo.com.csr -out bookinfo_certs/productpage.bookinfo.com.crt

Generate a client certificate and private key:

openssl req -out bookinfo_certs/client.bookinfo.com.csr -newkey rsa:2048 -nodes -keyout bookinfo_certs/client.bookinfo.com.key -subj "/CN=client.bookinfo.com/O=client organization"
openssl x509 -req -sha256 -days 365 -CA bookinfo_certs/bookinfo.com.crt -CAkey bookinfo_certs/bookinfo.com.key -set_serial 1 -in bookinfo_certs/client.bookinfo.com.csr -out bookinfo_certs/client.bookinfo.com.crt

Configure a TLS ingress gateway

Create a Kubernetes TLS secret for the ingress gateway; use Azure Key Vault to host certificates/keys and Azure Key Vault Secrets Provider add-on to sync secrets to the cluster.

Set up Azure Key Vault and sync secrets to the cluster

Create Azure Key Vault

You need an Azure Key Vault resource to supply the certificate and key inputs to the Istio add-on.

export AKV_NAME=<azure-key-vault-resource-name>  
az keyvault create --name $AKV_NAME --resource-group $RESOURCE_GROUP --location $LOCATION

Enable Azure Key Vault provider for Secret Store CSI Driver add-on on your cluster.

az aks enable-addons --addons azure-keyvault-secrets-provider --resource-group $RESOURCE_GROUP --name $CLUSTER

Authorize the user-assigned managed identity of the add-on to access Azure Key Vault resource using access policy. Alternatively, if your Key Vault is using Azure RBAC for the permissions model, follow the instructions here to assign an Azure role of Key Vault for the add-on's user-assigned managed identity.

OBJECT_ID=$(az aks show --resource-group $RESOURCE_GROUP --name $CLUSTER --query 'addonProfiles.azureKeyvaultSecretsProvider.identity.objectId' -o tsv | tr -d '\r')
CLIENT_ID=$(az aks show --resource-group $RESOURCE_GROUP --name $CLUSTER --query 'addonProfiles.azureKeyvaultSecretsProvider.identity.clientId')
TENANT_ID=$(az keyvault show --resource-group $RESOURCE_GROUP --name $AKV_NAME --query 'properties.tenantId')

az keyvault set-policy --name $AKV_NAME --object-id $OBJECT_ID --secret-permissions get list

Create secrets in Azure Key Vault using the certificates and keys.

az keyvault secret set --vault-name $AKV_NAME --name test-productpage-bookinfo-key --file bookinfo_certs/productpage.bookinfo.com.key
az keyvault secret set --vault-name $AKV_NAME --name test-productpage-bookinfo-crt --file bookinfo_certs/productpage.bookinfo.com.crt
az keyvault secret set --vault-name $AKV_NAME --name test-bookinfo-crt --file bookinfo_certs/bookinfo.com.crt

Use the following manifest to deploy SecretProviderClass to provide Azure Key Vault specific parameters to the CSI driver.

cat <<EOF | kubectl apply -f -
apiVersion: secrets-store.csi.x-k8s.io/v1
kind: SecretProviderClass
metadata:
  name: productpage-credential-spc
  namespace: aks-istio-ingress
spec:
  provider: azure
  secretObjects:
  - secretName: productpage-credential
    type: tls
    data:
    - objectName: test-productpage-bookinfo-key
      key: key
    - objectName: test-productpage-bookinfo-crt
      key: cert
  parameters:
    useVMManagedIdentity: "true"
    userAssignedIdentityID: $CLIENT_ID 
    keyvaultName: $AKV_NAME
    cloudName: ""
    objects:  |
      array:
        - |
          objectName: test-productpage-bookinfo-key
          objectType: secret
          objectAlias: "test-productpage-bookinfo-key"
        - |
          objectName: test-productpage-bookinfo-crt
          objectType: secret
          objectAlias: "test-productpage-bookinfo-crt"
    tenantId: $TENANT_ID
EOF

Use the following manifest to deploy a sample pod. The secret store CSI driver requires a pod to reference the SecretProviderClass resource to ensure secrets sync from Azure Key Vault to the cluster.

cat <<EOF | kubectl apply -f -
apiVersion: v1
kind: Pod
metadata:
  name: secrets-store-sync-productpage
  namespace: aks-istio-ingress
spec:
  containers:
    - name: busybox
      image: mcr.microsoft.com/oss/busybox/busybox:1.33.1
      command:
        - "/bin/sleep"
        - "10"
      volumeMounts:
      - name: secrets-store01-inline
        mountPath: "/mnt/secrets-store"
        readOnly: true
  volumes:
    - name: secrets-store01-inline
      csi:
        driver: secrets-store.csi.k8s.io
        readOnly: true
        volumeAttributes:
          secretProviderClass: "productpage-credential-spc"
EOF

Verify productpage-credential secret created on the cluster namespace aks-istio-ingress as defined in the SecretProviderClass resource.

kubectl describe secret/productpage-credential -n aks-istio-ingress

Example output:

Name:         productpage-credential
Namespace:    aks-istio-ingress
Labels:       secrets-store.csi.k8s.io/managed=true
Annotations:  <none>

Type:  tls

Data
====
cert:  1066 bytes
key:   1704 bytes

Configure ingress gateway and virtual service

Route HTTPS traffic via the Istio ingress gateway to the sample applications. Use the following manifest to deploy gateway and virtual service resources.

cat <<EOF | kubectl apply -f -
apiVersion: networking.istio.io/v1beta1
kind: Gateway
metadata:
  name: bookinfo-gateway
spec:
  selector:
    istio: aks-istio-ingressgateway-external
  servers:
  - port:
      number: 443
      name: https
      protocol: HTTPS
    tls:
      mode: SIMPLE
      credentialName: productpage-credential
    hosts:
    - productpage.bookinfo.com
---
apiVersion: networking.istio.io/v1beta1
kind: VirtualService
metadata:
  name: productpage-vs
spec:
  hosts:
  - productpage.bookinfo.com
  gateways:
  - bookinfo-gateway
  http:
  - match:
    - uri:
        exact: /productpage
    - uri:
        prefix: /static
    - uri:
        exact: /login
    - uri:
        exact: /logout
    - uri:
        prefix: /api/v1/products
    route:
    - destination:
        port:
          number: 9080
        host: productpage
EOF

Note

In the gateway definition, credentialName must match the secretName in SecretProviderClass resource and selector must refer to the external ingress gateway by its label, in which the key of the label is istio and the value is aks-istio-ingressgateway-external. For internal ingress gateway label is istio and the value is aks-istio-ingressgateway-internal.

Set environment variables for external ingress host and ports:

export INGRESS_HOST_EXTERNAL=$(kubectl -n aks-istio-ingress get service aks-istio-ingressgateway-external -o jsonpath='{.status.loadBalancer.ingress[0].ip}')
export SECURE_INGRESS_PORT_EXTERNAL=$(kubectl -n aks-istio-ingress get service aks-istio-ingressgateway-external -o jsonpath='{.spec.ports[?(@.name=="https")].port}')
export SECURE_GATEWAY_URL_EXTERNAL=$INGRESS_HOST_EXTERNAL:$SECURE_INGRESS_PORT_EXTERNAL

echo "https://$SECURE_GATEWAY_URL_EXTERNAL/productpage"

Verification

Send an HTTPS request to access the productpage service through HTTPS:

curl -s -HHost:productpage.bookinfo.com --resolve "productpage.bookinfo.com:$SECURE_INGRESS_PORT_EXTERNAL:$INGRESS_HOST_EXTERNAL" --cacert bookinfo_certs/bookinfo.com.crt "https://productpage.bookinfo.com:$SECURE_INGRESS_PORT_EXTERNAL/productpage" | grep -o "<title>.*</title>"

Confirm that the sample application's product page is accessible. The expected output is:

<title>Simple Bookstore App</title>

Note

To configure HTTPS ingress access to an HTTPS service, i.e., configure an ingress gateway to perform SNI passthrough instead of TLS termination on incoming requests, update the tls mode in the gateway definition to PASSTHROUGH. This instructs the gateway to pass the ingress traffic “as is”, without terminating TLS.

Configure a mutual TLS ingress gateway

Extend your gateway definition to support mutual TLS.

Update the ingress gateway credential by deleting the current secret and creating a new one. The server uses the CA certificate to verify its clients, and we must use the key ca.crt to hold the CA certificate.

kubectl delete secretproviderclass productpage-credential-spc -n aks-istio-ingress
kubectl delete secret/productpage-credential -n aks-istio-ingress
kubectl delete pod/secrets-store-sync-productpage -n aks-istio-ingress

Use the following manifest to recreate SecretProviderClass with CA certificate.

cat <<EOF | kubectl apply -f -
apiVersion: secrets-store.csi.x-k8s.io/v1
kind: SecretProviderClass
metadata:
  name: productpage-credential-spc
  namespace: aks-istio-ingress
spec:
  provider: azure
  secretObjects:
  - secretName: productpage-credential
    type: opaque
    data:
    - objectName: test-productpage-bookinfo-key
      key: tls.key
    - objectName: test-productpage-bookinfo-crt
      key: tls.crt
    - objectName: test-bookinfo-crt
      key: ca.crt
  parameters:
    useVMManagedIdentity: "true"
    userAssignedIdentityID: $CLIENT_ID 
    keyvaultName: $AKV_NAME
    cloudName: ""
    objects:  |
      array:
        - |
          objectName: test-productpage-bookinfo-key
          objectType: secret
          objectAlias: "test-productpage-bookinfo-key"
        - |
          objectName: test-productpage-bookinfo-crt
          objectType: secret
          objectAlias: "test-productpage-bookinfo-crt"
        - |
          objectName: test-bookinfo-crt
          objectType: secret
          objectAlias: "test-bookinfo-crt"
    tenantId: $TENANT_ID
EOF

Use the following manifest to redeploy sample pod to sync secrets from Azure Key Vault to the cluster.

cat <<EOF | kubectl apply -f -
apiVersion: v1
kind: Pod
metadata:
  name: secrets-store-sync-productpage
  namespace: aks-istio-ingress
spec:
  containers:
    - name: busybox
      image: registry.k8s.io/e2e-test-images/busybox:1.29-4
      command:
        - "/bin/sleep"
        - "10"
      volumeMounts:
      - name: secrets-store01-inline
        mountPath: "/mnt/secrets-store"
        readOnly: true
  volumes:
    - name: secrets-store01-inline
      csi:
        driver: secrets-store.csi.k8s.io
        readOnly: true
        volumeAttributes:
          secretProviderClass: "productpage-credential-spc"
EOF

Verify productpage-credential secret created on the cluster namespace aks-istio-ingress.

kubectl describe secret/productpage-credential -n aks-istio-ingress

Example output:

Name:         productpage-credential
Namespace:    aks-istio-ingress
Labels:       secrets-store.csi.k8s.io/managed=true
Annotations:  <none>

Type:  opaque

Data
====
ca.crt:   1188 bytes
tls.crt:  1066 bytes
tls.key:  1704 bytes

Use the following manifest to update the gateway definition to set the TLS mode to MUTUAL.

cat <<EOF | kubectl apply -f -
apiVersion: networking.istio.io/v1beta1
kind: Gateway
metadata:
  name: bookinfo-gateway
spec:
  selector:
    istio: aks-istio-ingressgateway-external # use istio default ingress gateway
  servers:
  - port:
      number: 443
      name: https
      protocol: HTTPS
    tls:
      mode: MUTUAL
      credentialName: productpage-credential # must be the same as secret
    hosts:
    - productpage.bookinfo.com
EOF

Verification

Attempt to send HTTPS request using the prior approach - without passing the client certificate - and see it fail.

curl -v -HHost:productpage.bookinfo.com --resolve "productpage.bookinfo.com:$SECURE_INGRESS_PORT_EXTERNAL:$INGRESS_HOST_EXTERNAL" --cacert bookinfo_certs/bookinfo.com.crt "https://productpage.bookinfo.com:$SECURE_INGRESS_PORT_EXTERNAL/productpage"

Example output:


...
* TLSv1.2 (IN), TLS header, Supplemental data (23):
* TLSv1.3 (IN), TLS alert, unknown (628):
* OpenSSL SSL_read: error:0A00045C:SSL routines::tlsv13 alert certificate required, errno 0
* Failed receiving HTTP2 data
* OpenSSL SSL_write: SSL_ERROR_ZERO_RETURN, errno 0
* Failed sending HTTP2 data
* Connection #0 to host productpage.bookinfo.com left intact
curl: (56) OpenSSL SSL_read: error:0A00045C:SSL routines::tlsv13 alert certificate required, errno 0

Pass your client’s certificate with the --cert flag and private key with the --key flag to curl.

curl -s -HHost:productpage.bookinfo.com --resolve "productpage.bookinfo.com:$SECURE_INGRESS_PORT_EXTERNAL:$INGRESS_HOST_EXTERNAL" --cacert bookinfo_certs/bookinfo.com.crt --cert bookinfo_certs/client.bookinfo.com.crt --key bookinfo_certs/client.bookinfo.com.key "https://productpage.bookinfo.com:$SECURE_INGRESS_PORT_EXTERNAL/productpage" | grep -o "<title>.*</title>"

Confirm that the sample application's product page is accessible. The expected output is:

<title>Simple Bookstore App</title>

Delete resources

If you want to clean up the Istio service mesh and the ingresses (leaving behind the cluster), run the following command:

az aks mesh disable --resource-group ${RESOURCE_GROUP} --name ${CLUSTER}

If you want to clean up all the resources created from the Istio how-to guidance documents, run the following command:

az group delete --name ${RESOURCE_GROUP} --yes --no-wait

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Secure ingress gateway for Istio service mesh add-on for Azure Kubernetes Service

Prerequisites

Required client/server certificates and keys

Configure a TLS ingress gateway

Set up Azure Key Vault and sync secrets to the cluster

Configure ingress gateway and virtual service

Verification

Configure a mutual TLS ingress gateway

Verification

Delete resources

Feedback

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