Overview of App Security

Security is a core feature of the Google Cloud, but there are still steps you should take to protect your App Engine app and identify vulnerabilities.

Use the following features to ensure that your App Engine app is secure. To learn more about the Google Security Model and the available steps that you can take to secure your Google Cloud projects, see Google Cloud Platform Security.

HTTPS requests

Use HTTPS requests to access to your App Engine app securely. Depending on how your app is configured, you have the following options:

appspot.com domains

• Use the https URL prefix to send HTTPS request to the default service of your Google Cloud project, for example:
  https://PROJECT_ID.REGION_ID.r.appspot.com

• To target specific resources in your App Engine app, use the -dot- syntax to separate each resource you want to target, for example:
  https://VERSION-dot-SERVICE-dot-PROJECT_ID.REGION_ID.r.appspot.com

• To convert an HTTP URL to an HTTPS URL, replace the periods between each resource with -dot-, for example:
  http://SERVICE_ID.PROJECT_ID.REGION_ID.r.appspot.com
https://SERVICE_ID-dot-PROJECT_ID.REGION_ID.r.appspot.com

For more information about HTTPS URLs and targeting resources, see How Requests are Routed.

Custom domains

To send HTTPS requests with your custom domain, you can use the managed SSL certificates that are provisioned by App Engine. For more information, see Securing Custom Domains with SSL.

Access control

In each Google Cloud project, set up access control to determine who can access the services within the project, including App Engine. You can assign different roles to different accounts to ensure each account has only the permissions it needs to support your app. For details see, Setting Up Access Control.

App Engine firewall

The App Engine firewall enables you to control access to your App Engine app through a set of rules that can either allow or deny requests from the specified ranges of IP addresses. You are not billed for traffic or bandwidth that is blocked by the firewall. Create a firewall to:

Allow only traffic from within a specific network

Ensure that only a certain range of IP addresses from specific networks can access your app. For example, create rules to allow only the range of IP addresses from within your company's private network during your app's testing phase. You can then create and modify your firewall rules to control the scope of access throughout your release process, allowing only certain organizations, either within your company or externally, to access your app as it makes its way to public availability.

Allow only traffic from a specific service

Ensure that all the traffic to your App Engine app is first proxied through a specific service. For example, if you use a third-party Web Application Firewall (WAF) to proxy requests directed at your app, you can create firewall rules to deny all requests except those that are forwarded from your WAF.

Block abusive IP addresses

While Google Cloud has many mechanisms in place to prevent attacks, you can use the App Engine firewall to block traffic to your app from IP addresses that present malicious intent or shield your app from denial of service attacks and similar forms of abuse. You can add IP addresses or subnetworks to a denylist, so that requests routed from those addresses and subnetworks are denied before they reach your App Engine app.

For details about creating rules and configuring your firewall, see Controlling App Access with Firewalls.

Ingress controls

This section describes how to use ingress settings to restrict network access to your App Engine app. At a network level, by default, any resource on the internet is able to reach your App Engine app on its appspot URL or at a custom domain set up in App Engine. For example, the appspot.com URL can have the following format: SERVICE_ID.PROJECT_ID.REGION_ID.r.appspot.com.

You can change this default setting by specifying a different setting for ingress. All ingress paths, including the default appspot.com URL, are subject to your ingress setting. Ingress is set at the service level.

Available ingress settings

The following settings are available:

Accessing internal services

The following considerations apply:

• For requests from a Shared VPC, traffic is only considered internal if the App Engine app is deployed in the Shared VPC host project. If the App Engine app is deployed in a Shared VPC service project, only traffic from networks owned by the app's own project is internal. All other traffic, including traffic from other Shared VPCs, is external.

• When accessing internal services, call them as you would normally do by using their public URLs, either the default appspot.com URL or a custom domain set up in App Engine.

• For requests from Compute Engine VM instances or other resources running inside a VPC network in the same project, no further setup is required.

• For requests from other App Engine services or from Cloud Run or Cloud Run functions in the same project, connect the service or function to a VPC network and route all egress through the connector, as described in Connecting to a Shared VPC network.

• Requests from resources within VPC networks in the same project are classified as internal even if the resource they originate from has a public IP address.

• Requests from on-premises resources connected to the VPC network via Cloud VPN are considered internal.

View ingress settings

gcloud app services describe SERVICE

gcloud app services describe default

Edit ingress settings

gcloud app services update SERVICE --ingress=INGRESS

Egress settings

If you use Serverless VPC Access, you can specify the egress setting for your App Engine service.

By default, only requests to internal IP addresses and internal DNS names are routed through a Serverless VPC Access connector. You can specify the egress setting for your service in your app.yaml file.

Egress settings are not compatible with the URL Fetch service. If you have not already done so, disable the URL Fetch default and discontinue any explicit use of the urlfetch library. Using the urlfetch library ignores egress settings, and requests will not route through a Serverless VPC Access connector.

To configure the egress behavior of your App Engine service:

1. Add the egress_setting attribute to the vpc_access_connector field of your service's app.yaml file:

   vpc_access_connector:
     name: projects/PROJECT_ID/locations/REGION/connectors/CONNECTOR_NAME
     egress_setting: EGRESS_SETTING

   Replace:

   • PROJECT_ID with your Google Cloud project ID
   • REGION with the region your connector is in
   • CONNECTOR_NAME with the name of your connector
   • EGRESS_SETTING with one of the following:
     • private-ranges-only Default. Only requests to RFC 1918 and RFC 6598 IP address ranges or internal DNS names are routed to your VPC network. All other requests are routed directly to the internet.
     • all-traffic All outbound requests from your service are routed to your VPC network. Requests are then subject to the firewall, DNS, and routing rules of your VPC network. Note that routing all outbound requests to your VPC network increases the amount of egress handled by the Serverless VPC Access connector and can incur charges.

2. Deploy the service:

   gcloud app deploy
   

Security scanner

The Google Cloud Web Security Scanner discovers vulnerabilities by crawling your App Engine app, following all that links within the scope of your starting URLs, and attempting to exercise as many user inputs and event handlers as possible.

In order to use the security scanner, you must be an owner of the Google Cloud project. For more information on assigning roles, see Setting Up Access Control.

You can run security scans from the Google Cloud console to identify security vulnerabilities in your App Engine app. For details about running the Security Scanner, see the Using Web Security Scanner.