Integrating IAP with Cloud Service Mesh

This guide describes how to integrate Identity-Aware Proxy (IAP) with Cloud Service Mesh. The IAP integration with Cloud Service Mesh enables you to safely access services based on Google's BeyondCorp principles. IAP verifies user identity and context of the request to determine if a user should be allowed to access an application or resource. The IAP integration with Cloud Service Mesh provides you with the following benefits:

• Complete context-aware access control to the workloads running on Cloud Service Mesh. You can set fine-grained access policies based on attributes of the originating request, such as user identity, the IP address, and device type. You can combine your access policies with restrictions based on the hostname and path of a request URL.

• Enable support for context-aware claims in Cloud Service Mesh authorization.

• Scalable, secure, and highly available access to your application through a Google Cloud load balancer. High performance load balancing provides built-in protection of distributed denial-of-service (DDoS) attacks and support for global anycast IP addressing.

Prerequisites

Warning: HTTP Load Balancing with Cloud Service Mesh requires GKE 1.17.6-gke.11 or later.

Follow the steps in Install dependent tools and validate cluster to:

• Install required tools
• Download asmcli
• Grant cluster admin permissions
• Validate your project and cluster

Additionally, this guide assumes that you have:

• A Google Cloud project.
• A Cloud Billing account.

Setting up a cluster with Anthos Service Mesh

This section explains how to get set up for the IAP integration for both new installations of Cloud Service Mesh and upgrades.

New installations

1. Enable iap.googleapis.com. In the following command, replace PROJECT_IDwith the project that you will install Cloud Service Mesh in:

   gcloud services enable \
     --project=PROJECT_ID \
     iap.googleapis.com
   

2. The cluster that you are updating must have the --addons=HttpLoadBalancing option set. The HttpLoadBalancing add-on enables an HTTP (L7) load balancing controller for the cluster. Run the following command to update the cluster with the options required by Cloud Service Mesh. Unless you've set a default zone or region, you need to supply the region (--region=REGION) or zone (--zone=ZONE) in the command.

   gcloud container clusters update CLUSTER_NAME \
     --project=PROJECT_ID \
     --update-addons=HttpLoadBalancing=ENABLED
   

3. By default, the iap-operator.yaml file has port 31223 set as the status port, and port 31224 set as the http port. If port 31223 is already in use in your cluster, run the following to set another status port:

   Important: You must use a kpt version earlier than v1.0.

   kpt cfg set asm gcloud.container.cluster.ingress.statusPort STATUS_PORT
   

   If port 31224 is already in use in your cluster, run the following to set another http port:

   kpt cfg set asm gcloud.container.cluster.ingress.httpPort HTTP_PORT
   

4. Follow the steps in Install default features and Mesh CA to use a Google-provided script to install Cloud Service Mesh. When you run the script, include the following option:

   --option iap-operator
   

   For example:

   ./asmcli install \
     --project_id "PROJECT_ID" \
     --cluster_name "CLUSTER_NAME" \
     --cluster_location "CLUSTER_LOCATION" \
     --fleet_id FLEET_PROJECT_ID \
     --output_dir DIR_PATH \
     --enable_all \
     --option iap-operator
   

   When you install Cloud Service Mesh, the iap-operator.yaml file sets the type field on the istio-ingressgateway service to NodePort, which configures the gateway to open a specific port on the service mesh. This allows you to set up a load balancer, which routes traffic sent to your domain name to this port.

5. If you are installing managed Cloud Service Mesh, then also complete the following steps:

   1. Add the revision label to the istio-system namespace.

   2. Download the Istio ingress gateway service spec for IAP and name it iap_operator.yaml.

   3. Install the ingress as a NodePort service. For more information, see Migrate from IstioOperator.

      asmcli experimental mcp-migrate-check -f iap_operator.yaml
      
      istioctl install -f /asm-generated-configs/gateways-istiooperator/"GATEWAY_NAME".yaml
      

After installing Cloud Service Mesh, return to this guide and continue with the next section to set up the integration with IAP.

Upgrades

This section covers the following upgrade use cases:

• You have already set up the IAP integration and you are upgrading Cloud Service Mesh. In this case, you have already enabled iap.googleapis.com on your project and the HttpLoadBalancing add-on on your cluster. Skip to step 3, to download the asm package and upgrade Cloud Service Mesh.

• You are upgrading Cloud Service Mesh and you want to set up the integration with IAP for the first time. In this case, you need to complete all of the following steps, upgrade Cloud Service Mesh, and return to this guide after the upgrade to complete the integration.

1. Enable iap.googleapis.com. In the following command, replace PROJECT_IDwith the project that you will install Cloud Service Mesh in.

   gcloud services enable \
     --project=PROJECT_ID \
     iap.googleapis.com
   

2. The cluster that you are updating must have the --addons=HttpLoadBalancing option set. The HttpLoadBalancing add-on enables an HTTP (L7) load balancing controller for the cluster. Run the following command to update the cluster with the options required by Cloud Service Mesh. Unless you've set a default zone or region, you need to supply the region (--region=REGION) or zone (--zone=ZONE) in the command.

   gcloud container clusters update CLUSTER_NAME \
     --project=PROJECT_ID
     --update-addons=HttpLoadBalancing=ENABLED
   

3. If you are updating an existing, functioning HTTP Cloud Load Balancer, run the following to preserve your existing http and status ports:

   Important: You must use a kpt version earlier than v1.0.

   kpt cfg set asm gcloud.container.cluster.ingress.httpPort $(kubectl -n istio-system get service istio-ingressgateway -o jsonpath='{.spec.ports[?(@.name=="http2")].nodePort}')
   

   kpt cfg set asm gcloud.container.cluster.ingress.statusPort $(kubectl -n istio-system get service istio-ingressgateway -o jsonpath='{.spec.ports[?(@.name=="status-port")].nodePort}')
   

4. Follow the steps in Upgrading Cloud Service Mesh to use a Google-provided script to upgrade Cloud Service Mesh.

   When you upgrade Cloud Service Mesh, the iap-operator.yaml file sets the type field on the istio-ingressgateway service to NodePort, which configures the gateway to open a specific port on the service mesh. This allows you to set up a load balancer, which routes traffic sent to your domain name to this port.

   By default, the iap-operator.yaml file has port 31223 set as the status port, and port 31224 set as the http port.

   When you run the script, include the following option:

   --option iap-operator
   

   For example:

   ./asmcli install \
     --project_id "PROJECT_ID" \
     --cluster_name "CLUSTER_NAME" \
     --cluster_location "CLUSTER_LOCATION" \
     --fleet_id FLEET_PROJECT_ID \
     --output_dir DIR_PATH \
     --enable_all \
     --option iap-operator
   

5. Complete the upgrade by triggering automatic sidecar proxy injection on your workloads. For details, see Deploying and redeploying workloads.

   After completing the upgrade, return to this guide and continue with the next section to set up the integration with IAP.

Reserving a static IP address and configuring DNS

To integrate Identity-Aware Proxy with Cloud Service Mesh, you have to set up a Google Cloud HTTP(S) load balancer, which requires a domain name that points to a static IP address. You can reserve a static external IP address, which assigns the address to your project indefinitely until you explicitly release it.

1. Reserve a static external IP address:

   gcloud compute addresses create example-static-ip --global
   

2. Get the static IP address:

   gcloud compute addresses describe example-static-ip --global
   

3. In your domain name registrar, configure a fully qualified domain name (FQDN) with the static IP address. Typically, you add an A record to your DNS settings. The configuration steps and terminology for adding an A record for a FQDN vary depending on your domain name registrar.

   It can take 24 to 48 hours for the DNS setting to propagate. You can continue setting up everything in this guide, but you won't be able to test the setup until the DNS settings propagate.

Deploying a sample application

Before you enable IAP, you need an application running on your GKE cluster so you can verify that all requests have an identity. This guide uses the Bookinfo sample to demonstrate how to setup the HTTP(S) load balancer and enable IAP.

Follow the steps to deploy Bookinfo. Until you deploy the load balancer, the Bookinfo application isn't accessible outside of your GKE cluster (such as from a browser).

External requests

Bookinfo's Gateway resource (defined in samples/bookinfo/networking/bookinfo-gateway.yaml) uses the preconfigured istio-ingressgateway. Recall that when you deployed Cloud Service Mesh, you specified NodePort for the istio-ingressgateway, which opens a specific port on the service mesh. Although the nodes in your cluster have external IP addresses, requests coming from outside your cluster are blocked by Google Cloud firewall rules. With IAP, the correct way to expose applications to the public internet is by using a load balancer. Don't expose the node addresses using firewall rules, which would bypass IAP.

To route requests to Bookinfo, you set up an HTTP(S) load balancer in your Google Cloud project. Because the load balancer is in your project, it is inside of the firewall and can access the nodes in your cluster. After you configure the load balancer with the static IP address and your domain name, you can send requests to the domain name, and the load balancer forwards the requests to the nodes in the cluster.

Enabling IAP

The following steps describe how to enable IAP.

Note: OAuth clients for IAP can be created using gcloud CLI, but there are a few limitations to how these clients can be used. Learn more here. Alternatively, you can follow these steps to create a client with more relaxed restrictions.

1. Use the client ID (CLIENT_ID in the above step) and CLIENT_SECRET to enable Cloud Service Mesh. Create a kubernetes secret with the materials from your OAuth Client:

   kubectl create secret generic -n istio-system my-secret --from-literal=client_id=CLIENT_ID \
   --from-literal=client_secret=CLIENT_SECRET

Deploying the load balancer

You can use an Ingress resource to create an HTTP(S) load balancer with automatically configured SSL certificates. Managed SSL certificates are provisioned, renewed, and managed for your domain.

1. Create a ManagedCertificate resource. This resource specifies the domain for the SSL certificate. The spec.domains list must contain only one domain. Wildcard domains aren't supported. In the following YAML, replace DOMAIN_NAME with the domain name that you configured for the external static IP address.

   cat <<EOF | kubectl apply -f -
   apiVersion: networking.gke.io/v1
   kind: ManagedCertificate
   metadata:
     name: example-certificate
     namespace: istio-system
   spec:
     domains:
       - DOMAIN_NAME
   EOF

2. Create a BackendConfig resource. This resource instructs GCLB how to perform Health Checks on the Ingress Gateway, as well as configure Identity-Aware Proxy. First, collect a few values from the Ingress Gateway about health checks:

   • Health check ingress port: This is the health check port of istio-ingress.

     export HC_INGRESS_PORT=$(kubectl -n istio-system get service istio-ingressgateway -o jsonpath='{.spec.ports[?(@.name=="status-port")].nodePort}')

   • Health check ingress path: This is the health check path of istio-ingress.

     export HC_INGRESS_PATH=$(kubectl get pods -n istio-system -l app=istio-ingressgateway -o jsonpath='{.items[0].spec.containers[?(@.name=="istio-proxy")].readinessProbe.httpGet.path}')

   cat <<EOF | kubectl apply -n istio-system -f -
   apiVersion: cloud.google.com/v1
   kind: BackendConfig
   metadata:
     name: http-hc-config
   spec:
     healthCheck:
       checkIntervalSec: 2
       timeoutSec: 1
       healthyThreshold: 1
       unhealthyThreshold: 10
       port: ${HC_INGRESS_PORT}
       type: HTTP
       requestPath: ${HC_INGRESS_PATH}
     iap:
       enabled: true
       oauthclientCredentials:
         secretName: my-secret
   EOF

3. Annotate the ingress service with your BackendConfig.

       kubectl annotate -n istio-system service/istio-ingressgateway --overwrite \
         cloud.google.com/backend-config='{"default": "http-hc-config"}' \
         cloud.google.com/neg='{"ingress":false}'
   

4. Create the load balancer by defining the Ingress resource.

   • Set the networking.gke.io/managed-certificates annotation to the name of the certificate you created in the previous step, example-certificate.

   • Set the kubernetes.io/ingress.global-static-ip-name annotation to the name of the static IP address you reserved, example-static-ip.

   • Set the serviceName to istio-ingressgateway, which is used in the Gateway resource for the Bookinfo sample.

   cat <<EOF | kubectl apply -f -
   apiVersion: networking.k8s.io/v1
   kind: Ingress
   metadata:
     name: example-ingress
     namespace: istio-system
     annotations:
       kubernetes.io/ingress.global-static-ip-name: example-static-ip
       networking.gke.io/managed-certificates: example-certificate
   spec:
     defaultBackend:
       service:
         name: istio-ingressgateway
         port:
           number: 80
   EOF

   Note: It can take up to 10-20 minutes for the load balancer to be functional.

5. In the Google Cloud console, go to the Kubernetes Engine > Services & Ingress page.

   Go to the Services & Ingress page

   You should see the "Creating ingress" message in the Status column. Wait for GKE to fully provision the Ingress before continuing. Refresh the page every few minutes to get the most up-to-date status on the Ingress. After the Ingress is provisioned, you might see the "Ok" status, or the error "All backend services are in UNHEALTHY state." One of the resources that GKE provisions is a default health check. If you see the error message, that indicates that the Ingress is provisioned and that the default health check ran. When you see either the "Ok" status or the error, continue with the next section to configure the health checks for the load balancer.

Configure the IAP access list

Add a user to the access policy for IAP:

Caution: The below commands configure IAP settings and IAP policies at the project level. Therefore, the configurations will be applicable to all IAP resources in the project, including non-Cloud Service Mesh resources. This is required because the resources are deleted and recreated with every upgrade, and configuring IAP at project level allows us to persist IAP configuration across upgrades.

gcloud beta iap web add-iam-policy-binding \
    --member=user:EMAIL_ADDRESS \
    --role=roles/iap.httpsResourceAccessor

where EMAIL_ADDRESS is the user's full email address such as [e-mail].

1. Test the load balancer. Point your browser to:

   http://DOMAIN_NAME/productpage

   where DOMAIN_NAME is the domain name that you configured with the external static IP address.

   You should see the Bookinfo application's productpage. If you refresh the page several times, you should see different versions of reviews, presented in a round robin style: red stars, black stars, no stars.

   You should also test https access to Bookinfo.

Enable RCToken support on the service mesh

By default, IAP generates a JSON Web Token (JWT) that is scoped to the OAuth client. For Cloud Service Mesh, you can configure IAP to generate a RequestContextToken (RCToken), which is a JWT but with a configurable audience. RCToken lets you configure the audience of the JWT to an arbitrary string, which can be used in the Cloud Service Mesh policies for fine-grained authorization.

To configure the RCToken:

1. Create an environment variable for the RCToken audience. This can be any string that you want.

   export RCTOKEN_AUD="your-rctoken-aud"
   

2. Optional: The following step requires the BACKEND_SERVICE_ID. If you need to find out the BACKEND_SERVICE_ID, run the following command:

   kubectl -n istio-system get Ingress example-ingress -o json | jq \
    '.metadata.annotations."ingress.kubernetes.io/backends"'
   

   The expected output is similar to "{\"BACKEND_SERVICE_ID\":\"HEALTHY\"}". For example, "ingress.kubernetes.io/backends": "{\"k8s-be-31224--51f3b55cd1457fb6\":\"HEALTHY\"}". The BACKEND_SERVICE_ID in this example is k8s-be-31224--51f3b55cd1457fb6.

3. Fetch the existing IAP settings.

   gcloud iap settings get --format json \
   --project=${PROJECT_ID} --resource-type=compute --service=BACKEND_SERVICE_ID > iapSettings.json
   

4. Update IapSettings with the RCToken audience.

   cat iapSettings.json | jq --arg RCTOKEN_AUD_STR $RCTOKEN_AUD \
   '. + {applicationSettings: {csmSettings: {rctokenAud: $RCTOKEN_AUD_STR}}}' \
   > updatedIapSettings.json
   

   gcloud iap settings set updatedIapSettings.json --format json \
   --project=${PROJECT_ID} --resource-type=compute --service=BACKEND_SERVICE_ID
   

5. Enable RCToken authentication on the Istio ingress gateway.

   cat <<EOF | kubectl apply -f -
   apiVersion: "security.istio.io/v1beta1"
   kind: "RequestAuthentication"
   metadata:
     name: "ingressgateway-jwt-policy"
     namespace: "istio-system"
   spec:
     selector:
       matchLabels:
         app: istio-ingressgateway
     jwtRules:
     - issuer: "https://cloud.google.com/iap"
       jwksUri: "https://www.gstatic.com/iap/verify/public_key-jwk"
       audiences:
       - $RCTOKEN_AUD
       fromHeaders:
       - name: ingress-authorization
         prefix: "Istio "
       outputPayloadToHeader: "verified-jwt"
       forwardOriginalToken: true
   EOF
   

6. Optional: Ensure requests that don't have valid JWTs are rejected:

   Note: For more information, see Require a valid token.

     cat <<EOF | kubectl apply -f -
     apiVersion: security.istio.io/v1beta1
     kind: AuthorizationPolicy
     metadata:
       name: iap-gateway-require-jwt
       namespace: istio-system
     spec:
       selector:
         matchLabels:
           app: istio-iap-ingressgateway
       action: DENY
       rules:
         - from:
             - source:
                 notRequestPrincipals: ["*"]
     EOF
     

7. Make sure requests to the Bookinfo productpage are still successful:

   http://DOMAIN_NAME/productpage

To test the policy:

1. Create an IapSettings request object, but set the rctokenAud to a different string:

   cat iapSettings.json | jq --arg RCTOKEN_AUD_STR wrong-rctoken-aud \
   '. + {applicationSettings: {csmSettings: {rctokenAud: $RCTOKEN_AUD_STR}}}' \
   > wrongIapSettings.json
   

2. Call the IapSettings API to set the RCtoken audience.

   gcloud beta iap settings set wrongIapSettings.json --project=PROJECT_ID --resource-type=compute --service=BACKEND_SERVICE

3. Make a request to the Bookinfo productpage and it should fail:

   http://DOMAIN_NAME/productpage

Cleaning up

After completing this tutorial, remove the following resources to prevent unwanted charges incurring on your account:

1. Delete the managed certificate:

   kubectl delete managedcertificates example-certificate

2. Delete the Ingress, which deallocates the load balancing resources:

   kubectl -n istio-system delete ingress example-ingress

3. Delete the static IP address:

   gcloud compute addresses delete example-static-ip --global

   If you do this, be sure to delete the IP address from your domain registrar.

4. Delete the cluster, which deletes the resources that make up the cluster, such as the compute instances, disks and network resources:

   gcloud container clusters delete CLUSTER_NAME