Block Project-Wide SSH Keys Not Enabled

ID: gcloud-vm-project-ssh-keys-enabled

Severity: medium

Author: princechaddha

Tags: cloud,devops,gcp,gcloud,compute,security,ssh,gcp-cloud-config

Description

Ensure that your Google Compute Engine instances are configured to ignore GCP project-wide (shared) public SSH keys and use instance-level SSH keys instead. Project-wide SSH keys can be used to log in to all the VM instances running inside a GCP project. While project-wide SSH keys can ease SSH key management, if compromised, they pose a security risk which can impact all VM instances within the project.

YAML Source

id: gcloud-vm-project-ssh-keys-enabled

info:
  name: Block Project-Wide SSH Keys Not Enabled
  author: princechaddha
  severity: medium
  description: |
    Ensure that your Google Compute Engine instances are configured to ignore GCP project-wide (shared) public SSH keys and use instance-level SSH keys instead. Project-wide SSH keys can be used to log in to all the VM instances running inside a GCP project. While project-wide SSH keys can ease SSH key management, if compromised, they pose a security risk which can impact all VM instances within the project.
  impact: |
    Using project-wide SSH keys increases the attack surface - if compromised, an attacker could gain access to all VM instances in the project instead of just a single instance.
  remediation: |
    Enable "Block Project-Wide SSH Keys" feature for your VM instances and configure instance-specific SSH keys instead. This limits the impact if any single key is compromised.
  reference:
    - https://www.trendmicro.com/cloudoneconformity/knowledge-base/gcp/ComputeEngine/enable-block-project-wide-ssh-keys.html
    - https://cloud.google.com/compute/docs/instances/adding-removing-ssh-keys
  tags: cloud,devops,gcp,gcloud,compute,security,ssh,gcp-cloud-config

flow: |
  code(1)
  for(let projectId of iterate(template.projectIds)){
    set("projectId", projectId)
    code(2)
    for(let instance of iterate(template.instances)){
      instance = JSON.parse(instance)
      set("instanceName", instance.name)
      set("zone", instance.zone)
      code(3)
    }
  }

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 instances list --project $projectId --format="json(name,zone.basename())"

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

  - engine:
      - sh
      - bash
    source: |
      gcloud compute instances describe $instanceName --zone $zone --project $projectId --format="json(metadata.items)"

    matchers:
      - type: word
        words:
          - "null"

    extractors:
      - type: dsl
        dsl:
          - '"VM instance " + instanceName + " in zone " + zone + " of project " + projectId + " is not configured to block project-wide SSH keys"'
# digest: 490a0046304402207f53624c0d249b3aac27bf5fb31e65c05aec746010620bd810326b22598254f00220109787c755180220327be63e40bf99f95211d459a00abb5adb61d89e9b55afa1:922c64590222798bb761d5b6d8e72950

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/compute/gcloud-vm-project-ssh-keys-enabled.yaml"

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