Check for Unrestricted SSH Access

ID: gcloud-unrestricted-ssh-access

Severity: critical

Author: princechaddha

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

Description

Ensure that your Google Cloud VPC firewall rules do not allow unrestricted SSH access (0.0.0.0/0 on TCP port 22). Restrict SSH access to trusted IP addresses or ranges to reduce the attack surface and adhere to the principle of least privilege.

YAML Source

id: gcloud-unrestricted-ssh-access

info:
  name: Check for Unrestricted SSH Access
  author: princechaddha
  severity: critical
  description: |
    Ensure that your Google Cloud VPC firewall rules do not allow unrestricted SSH access (0.0.0.0/0 on TCP port 22). Restrict SSH access to trusted IP addresses or ranges to reduce the attack surface and adhere to the principle of least privilege.
  impact: |
    Allowing unrestricted SSH access exposes your infrastructure to potential brute-force attacks or unauthorized access.
  remediation: |
    Update your VPC firewall rules to allow SSH traffic only from trusted IP addresses or ranges.
  reference:
    - https://cloud.google.com/vpc/docs/firewalls
  tags: cloud,devops,gcp,gcloud,vpc,firewall,security,ssh,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)
      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,sourceRanges,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.sourceRanges) && rule.sourceRanges.includes("0.0.0.0/0") &&
          Array.isArray(rule.allowed) && rule.allowed.some(allowed =>
            Array.isArray(allowed.ports) && allowed.ports.includes("22")
          )
        ) {
          insecureRules.push(rule.name);
        }
      }

      if (insecureRules.length > 0) {
        Export(`The firewall rules in network ${template.networkName} of project ${template.projectId} allow unrestricted SSH access: ${insecureRules.join(", ")}`);
      }

    extractors:
      - type: dsl
        dsl:
          - response
# digest: 4a0a00473045022100ae76292b65867cbae75a860bb9fe3b7ea51d83dfc2de5a2a0d6e34d48adf3447022061bcb759bd6b54ab8dc1ebb27c918227f82000aaeca6c4ace2cbad063869f0ff: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-unrestricted-ssh-access.yaml"

View on Github