Securing App Engine apps with IAP

This page walks you through deploying an App Engine standard or flexible environment application and securing it with Identity-Aware Proxy (IAP). The quickstart includes sample code for an App Engine standard environment web app that verifies a logged-in user's name.

If you plan to serve resources from a content delivery network (CDN), see the best practices guide for important information.

To secure resources not on Google Cloud, see Securing on-premises apps and resources.

Before you begin

To enable IAP for App Engine, you need the following:

• A Google Cloud console project with billing enabled.

If you don't have your App Engine instance set up already, see Deploying App Engine for a complete walkthrough.

IAP uses a Google-managed OAuth client to authenticate users. Only users within the organization can access the IAP-enabled application. If you want to allow access to users outside of your organization, see Enable IAP for external applications.

Note: The ability to authenticate users with a Google-managed OAuth client is available in Preview.

Enabling IAP

Console

The Google-managed OAuth client is not available when enabling IAP using the Google Cloud console.

If you haven't configured your project's OAuth consent screen, you'll be prompted to do so. To configure your OAuth consent screen, see Setting up your OAuth consent screen.

Setting up IAP access

1. Go to the Identity-Aware Proxy page.
   Go to the Identity-Aware Proxy page
2. Select the project you want to secure with IAP.
3. Select the checkbox next to the resource you want to grant access to.
4. On the right side panel, click Add principal.
5. In the Add principals dialog that appears, enter the email addresses of groups or individuals who should have the IAP-secured Web App User role for the project.

   The following kinds of principals can have this role:

   • Google Account: [e-mail]
   • Google Group: [e-mail]
   • Service account: [e-mail]
   • Google Workspace domain: example.com

   Make sure to add a Google Account that you have access to.

6. Select Cloud IAP > IAP-secured Web App User from the Roles drop-down list.
7. Click Save.

Turning on IAP

1. On the Identity-Aware Proxy page, under APPLICATIONS, find the application you want to restrict access to. To turn on IAP for a resource, toggle the on/off switch in the IAP column.
   
2. In the Turn on IAP window that appears, click Turn On to confirm that you want IAP to secure your resource. After you turn on IAP, it requires login credentials for all connections to your load balancer. Only accounts with the IAP-Secured Web App User role on the project will be given access.

gcloud

Before you set up your project and IAP, you need an up-to-date version of the gcloud CLI. For instructions on how to install the gcloud CLI, see Install the gcloud CLI.

1. To authenticate, use the Google Cloud CLI and run the following command.

   gcloud auth login

2. Click the URL that appears and sign in.
3. After you sign in, copy the verification code that appears and paste it in the command line.
4. Run the following command to specify the project that contains the applications that you want to protect with IAP.

   gcloud config set project PROJECT_ID

5. To enable IAP, run the following command.

   gcloud iap web enable --resource-type=app-engine --versions=version

6. Add principals who should have the IAP-secured Web App user role to the project.

   gcloud projects add-iam-policy-binding PROJECT_ID \
          --member=PRINCIPAL_IDENTIFIER \
          --role=roles/iap.httpsResourceAccessor

   • Replace PROJECT_ID with your project ID.
   • Replace PRINCIPAL_IDENTIFIER with the necessary principals. This can be a type of domain, group, serviceAccount, or user. For example, user:[e-mail].

After you enable IAP, you can use the gcloud CLI to modify the IAP access policy using the IAM role roles/iap.httpsResourceAccessor. Learn more about managing roles and permissions.

API

1. Run the following command to prepare a settings.json file.

   cat << EOF > settings.json
   {
   "iap":
     {
       "enabled":true
     }
   }
   EOF
   

2. Run the following command to enable IAP.

   curl -X PATCH \
   -H "Authorization: Bearer $(gcloud auth print-access-token)" \
   -H "Accept: application/json" \
   -H "Content-Type: application/json" \
   -d @settings.json \
   "https://appengine.googleapis.com/v1/apps/PROJECT_ID?updateMask=iap"
   

After you enable IAP, you can use the Google Cloud CLI to modify the IAP access policy using the IAM role roles/iap.httpsResourceAccessor. Learn more about managing roles and permissions.

Note: When a App Engine application consists of multiple services, in order to make some services publicly-accessible and keep others restricted, enable IAP on the entire application, then grant the IAP-secured Web App User role to `allUsers` or `allAuthenticatedUsers` on the services that should be publicly-accessible.

Role-based access: If you're a project owner, you may think that you get automatic access to the app. That is not the case as only accounts with the IAP-secured Web App User role on this project will be given access. Imagine you're in corporate IT implementing IAP access to the HR payroll system. In most scenarios, only the staff on the Payroll team should have access to the app. This is one of the reasons why role-based access is more secure. The owner (or editor, etc.) of a project can manage all aspects of the project but doesn't automatically get app access.

Test user authentication

1. Access the app URL from a Google account that you added to IAP with the IAP-secured Web App User role as described above. You should have unrestricted access to the app.

2. Use an incognito window in Chrome to access the app and sign in when prompted. If you try to access the app with an account that isn't authorized with the IAP-secured Web App User role, you'll see a message saying that you don't have access.

Next steps

• Set richer context rules by applying access levels.
• See access requests by enabling Cloud Audit Logs.
• Learn more about IAP.
• Learn about getting the user's identity and develop your own App Engine app.