Overview of App Security

Region ID

The REGION_ID is an abbreviated code that Google assigns based on the region you select when you create your app. The code does not correspond to a country or province, even though some region IDs may appear similar to commonly used country and province codes. For apps created after February 2020, REGION_ID.r is included in App Engine URLs. For existing apps created before this date, the region ID is optional in the URL.

Learn more about region IDs.

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 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 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.

App handlers

To force HTTPS for your app's handlers, you can specify the secure: always element for each handler in your app.yaml, for example:

handlers:
- url: /.*
  script: auto
  secure: always
  redirect_http_response_code: 301

Using secure: always redirects all HTTP traffic to an HTTPS URL with the same path, see the app.yaml configuration reference for more information.

Access control

In each 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

By default, your App Engine app receives all HTTP requests that are sent to its appspot URL or to a custom domain that you have configured for your app.

You can use network ingress controls to restrict traffic so that your app only receives HTTP requests from specific sources:

All: Default. Your app will receive all traffic, including direct requests sent from the internet.
Internal and Cloud Load Balancing: Your app will only receive requests that are routed through Cloud Load Balancing, or that are sent from VPC networks in the same project (including Serverless VPC Access connectors or Shared VPC if you are using them). All other requests are denied with a 403 error.
Internal-only: Your app will only receive requests that are sent from VPC networks in the same project. All other requests are denied with a 403 error.

View ingress settings

Console

Go to the App Engine Services page.

Go to the Services page
Locate the Ingress column. For each service, the value in this column shows the ingress setting as one of All (default), Internal + Load Balancing, or Internal.

gcloud

To view the ingress setting for a service using the gcloud CLI:

gcloud app services describe SERVICE

Replace SERVICE with the name of your service.

For example, to view the ingress settings and other information for the default service run:

gcloud app services describe default

Edit ingress settings

Console

Go to the App Engine Services page.

Go to the Services page
Select the service you wish to edit.
Click Edit ingress setting.
Select the ingress setting that you want from the menu and click Save.

gcloud

To update the ingress setting for a service using the gcloud CLI:

gcloud app services update SERVICE --ingress=INGRESS

Replace:

SERVICE: The name of your service.
INGRESS: The ingress control you want to apply. One of all, internal-only, or internal-and-cloud-load-balancing.

For example:

To update the default service of an App Engine app to accept traffic only from Cloud Load Balancing and VPC networks that are in the same project:
```
gcloud app services update default --ingress=internal-and-cloud-load-balancing
```
To update a service named "internal-requests" to accept traffic only from VPC networks that are in the same project:
```
gcloud app services update internal-requests --ingress=internal-only
```

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.

To configure the egress behavior of your App Engine service:

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 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.
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 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 Security Scanner Quickstart.