k8s-readonly-fs: Enforce Read-Only Filesystem for Containers

id: k8s-readonly-fs

info:
  name: Enforce Read-Only Filesystem for Containers
  author: princechaddha
  severity: critical
  description: Checks for containers that do not use a read-only filesystem, which can prevent malicious write operations at runtime
  impact: |
    Not using a read-only filesystem can expose containers to risks of malicious modifications at runtime, compromising the container's integrity and security.
  remediation: Configure containers to use read-only filesystems where possible to enhance security and minimize risk of unauthorized data modification
  reference:
    - https://kubernetes.io/docs/concepts/storage/volumes/#mount-propagation
  tags: cloud,devops,kubernetes,k8s,devsecops,pods,k8s-cluster-security

flow: |
  code(1);
  for (let container of template.items) {
    set("container", container)
    javascript(1);
  }

self-contained: true
code:
  - engine:
      - sh
      - bash
    source: kubectl get pods --all-namespaces --output=json
    extractors:
      - type: json
        name: items
        internal: true
        json:
          - '.items[].spec.containers[]'

javascript:
  - code: |
        container = JSON.parse(template.container);
        if (!container.securityContext || container.securityContext.readOnlyRootFilesystem !== true) {
          let result = (`Container '${container.name}' in pod '${container.metadata.name}' in namespace '${container.metadata.namespace}' does not use a read-only filesystem.`);
          Export(result);
        }

    extractors:
      - type: dsl
        dsl:
          - response
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