Check for VPC Firewall Rules with Port Ranges

ID: gcloud-vpc-firewall-port-ranges

Severity: medium

Author: princechaddha

Tags: cloud,devops,gcp,gcloud,vpc,firewall,security,networking,gcp-cloud-config

Description

Ensure that your Google Cloud VPC network firewall rules don’t have ranges of ports configured to allow inbound traffic. This protects associated virtual machine instances against Denial-of-Service (DoS) attacks or brute-force attacks. It is recommended to open only specific ports within your firewall rules based on your application requirements.

YAML Source

id: gcloud-vpc-firewall-port-ranges

info:
  name: Check for VPC Firewall Rules with Port Ranges
  author: princechaddha
  severity: medium
  description: |
    Ensure that your Google Cloud VPC network firewall rules don't have ranges of ports configured to allow inbound traffic. This protects associated virtual machine instances against Denial-of-Service (DoS) attacks or brute-force attacks. It is recommended to open only specific ports within your firewall rules based on your application requirements.
  impact: |
    Allowing a range of ports in firewall rules increases the attack surface, exposing cloud resources to potential attacks.
  remediation: |
    Update your VPC firewall rules to allow only specific ports required for your applications, rather than a range of ports.
  reference:
    - https://cloud.google.com/vpc/docs/firewalls
  tags: cloud,devops,gcp,gcloud,vpc,firewall,security,networking,gcp-cloud-config

flow: |
  code(1)
  for(let projectId of iterate(template.projectIds)){
    set("projectId", projectId)
    code(2)
    for(let networkName of iterate(template.networks)){
      set("networkName", networkName)
      code(3)
      set("firewallRules", template.firewallRules)
      javascript(1)
    }
  }

self-contained: true

code:
  - engine:
      - sh
      - bash
    source: |
      gcloud projects list --format="json(projectId)"

    extractors:
      - type: json
        name: projectIds
        internal: true
        json:
          - '.[].projectId'

  - engine:
      - sh
      - bash
    source: |
      gcloud compute networks list --project $projectId --format="json(name)"

    extractors:
      - type: json
        name: networks
        internal: true
        json:
          - '.[].name'

  - engine:
      - sh
      - bash
    source: |
      gcloud compute firewall-rules list --filter network=$networkName --sort-by priority --format="json(name,disabled,direction,allowed[].ports)"

    extractors:
      - type: json
        name: firewallRules
        internal: true
        json:
          - '.[]'

javascript:
  - code: |
      let firewallRules = template.firewallRules;
            if (typeof firewallRules === "string") {
              firewallRules = JSON.parse(firewallRules); }

      let insecureRules = [];
      for (let rule of firewallRules) {
          if (
              rule.disabled === false &&
              rule.direction === "INGRESS" &&
              Array.isArray(rule.allowed) &&
              rule.allowed.some(allowed =>
                  Array.isArray(allowed.ports) &&
                  allowed.ports.some(port => port.includes("0-") || port.includes("80-8080"))
              )
          ) {
              insecureRules.push(rule.name);
          }
      }

      if (insecureRules.length > 0) {
          Export(`The firewall rules in network ${template.networkName} of project ${template.projectId} allow insecure port ranges for ingress traffic: ${insecureRules.join(", ")}`);
      }

    extractors:
      - type: dsl
        dsl:
          - response
# digest: 4a0a0047304502201cd818761078f4037d69a38657656c26cb8e75a392059cadcebf2ea0fe9e1717022100c11730f4cb93daf0366e3c43a4e465ce5de1a590fa6655c870ab2fc59b4a2115:922c64590222798bb761d5b6d8e72950

Guide to check the vulnerabilities

This template is used to detect vulnerabilities in web applications. It can be used with the Nuclei tool to scan for specific patterns or behaviors.

$ nuclei -u "URL" -t "cloud/gcp/vpc/gcloud-vpc-firewall-port-ranges.yaml"

View on Github