Google Cloud Platform network is not ensured to define a firewall misconfiguration detected in code

Rule Details

Cortex AppSec Rule ID	APPSEC2_GCP_18
Category - Subcategory	Public Exposure - Ingress Controls
Provider	GCP
Severity	MEDIUM
Framework	Terraform, Terraform Plan

Impact

This rule is verifying that a Google Cloud Platform (GCP) network has a defined firewall and is not using the default firewall settings. By using the default firewall settings, a network may expose vulnerabilities or unnecessary access points, thereby increasing the risk of unauthorized access and potential data breaches. Therefore, it is essential to define a custom firewall rule that aligns with the specific security needs of the network.

How to Fix

Resource: google_compute_network, google_compute_firewall

To fix this issue, you need to create a new firewall in the GCP network and make sure it does not use the default firewall. You can do this by defining it in your Terraform scripts.

[source,go]

resource "google_compute_firewall" "default" { name = "test-firewall" network = google_compute_network.default.self_link

allow { protocol = "icmp" } allow { protocol = "tcp" ports = ["80", "443"] } }

resource "google_compute_network" "default" { name = "test-network" auto_create_subnetworks = "false" }

This Terraform code creates custom network and firewall which does not rely on default firewall. The firewall rule test-firewall is associated with the custom network test-network, thus the GCP network no longer uses the default firewall. It has specific rules which only allows traffic on ICMP protocol and TCP ports 80 and 443, reducing the attack surface.