GCP Firewall rule allows all traffic on RDP port (3389) misconfiguration detected in code

Rule Details

Cortex AppSec Rule ID	APPSEC_GCP_3
Category - Subcategory	Public Exposure - Sensitive Ports
Provider	GCP
Severity	LOW
Framework	Terraform, Terraform Plan
Mapped CSPM/KSPM Rule	34175634-0e4a-4e9d-9c77-0c75390b8bdc

Impact

Firewall rules setup fine grained allow/deny traffic policies to and from a virtual machine (VM). Enabled rules are always enforced, and help protecting instances from unwanted traffic. Firewall rules are defined at the network level, and only apply to the network where they are created. Every VPC functions as a distributed firewall. While firewall rules are defined at the network level, connections are allowed or denied on a per-instance basis. A default network is pre-populated with firewall rules that allow incoming traffic to instances. The default-allow-rdp rule permits ingress connections on TCP port 3389 from any source to any instance in the network. We recommend you restrict or remove the default-allow-rdp rule when you no longer need it.

How to Fix

Resource: google_compute_firewall

• Arguments: deny.

The deny block supports: protocol (Required) The IP protocol to which this rule applies. The protocol type is required when creating a firewall rule. This value can either be one of the following well known protocol strings (tcp, udp, icmp, esp, ah, sctp, ipip), or the IP protocol number. ports (Optional) An optional list of ports to which this rule applies. This field is only applicable for UDP or TCP protocol. Each entry must be either an integer or a range. If not specified, this rule applies to connections through any port. Example inputs include: ["22"], ["80","443"], and ["12345-12349"]. [source,go]

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

allow { protocol = "icmp" }

deny { protocol = "tcp" ports = ["3389"] }

", }