k8s-svc-acct-key: Ensure service-account-key-file set

id: k8s-svc-acct-key

info:
  name: Ensure service-account-key-file set
  author: princechaddha
  severity: medium
  description: Checks if the service-account-key-file argument is properly set in the API server configuration, which is critical for validating service account tokens.
  impact: |
    The absence of the service-account-key-file argument means that the API server might not perform robust authentication checks for service accounts, potentially allowing unauthorized access.
  remediation: |
    Configure the API server to use a service-account-key-file that points to a valid private key used to sign service account tokens. This setting should be part of the API server startup arguments or in its configuration file.
  reference:
    - https://kubernetes.io/docs/admin/kube-apiserver/
  tags: cloud,devops,kubernetes,security,devsecops,api-server,k8s,k8s-cluster-security

variables:
  argument: "service-account-key-file"

self-contained: true
code:
  - engine:
      - sh
      - bash
    source: |
      kubectl get pods -n kube-system -l component=kube-apiserver -o jsonpath="{.items[*].spec.containers[*].command}"

    matchers-condition: and
    matchers:
      - type: word
        words:
          - 'kube-apiserver'

      - type: word
        words:
          - "service-account-key-file"
        negative: true

    extractors:
      - type: dsl
        dsl:
          - '"API server configuration is missing the " + argument + " argument."'
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