Detections
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3.10 Use Identity Aware Proxy (IAP) to Ensure Only Traffic From Google IP Addresses are 'Allowed'

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This audit has been deprecated and will be removed in a future update.

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Information

IAP authenticates the user requests to your apps via a Google single sign in. You can then manage these users with permissions to control access. It is recommended to use both IAP permissions and firewalls to restrict this access to your apps with sensitive information.

Rationale:

IAP ensure that access to VMs is controlled by authenticating incoming requests. Access to your apps and the VMs should be restricted by firewall rules that allow only the proxy IAP IP addresses contained in the 35.235.240.0/20 subnet. Otherwise, unauthenticated requests can be made to your apps. To ensure that load balancing works correctly health checks should also be allowed.

Impact:

If firewall rules are not configured correctly, legitimate business services could be negatively impacted. It is recommended to make these changes during a time of low usage.

NOTE: Nessus has not performed this check. Please review the benchmark to ensure target compliance.

Solution

From Google Cloud Console

Go to the Cloud Console VPC network > Firewall rules.

Select the checkbox next to the following rules:

default-allow-http

default-allow-https

default-allow-internal

Click Delete.

Click Create firewall rule and set the following values:

Name: allow-iap-traffic

Targets: All instances in the network

Source IP ranges (press Enter after you paste each value in the box, copy each full CIDR IP address):

IAP Proxy Addresses 35.235.240.0/20

Google Health Check 130.211.0.0/22

Google Health Check 35.191.0.0/16

Protocols and ports:

Specified protocols and ports required for access and management of your app. For example most health check connection protocols would be covered by;

tcp:80 (Default HTTP Health Check port)

tcp:443 (Default HTTPS Health Check port)
Note: if you have custom ports used by your load balancers, you will need to list them here

When you're finished updating values, click Create.

Default Value:

By default all traffic is allowed.

See Also

https://workbench.cisecurity.org/benchmarks/11843

Item Details

References: CSCv7|16.2

Plugin: GCP

Control ID: 60b3481d943a9f9371402ead31eb11d517abc85fd456113225aa4fa9a6b86e31