yaml.kubernetes.security.run-as-non-root.run-as-non-root

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When running containers in Kubernetes, it's important to ensure that they are properly secured to prevent privilege escalation attacks. One potential vulnerability is when a container is allowed to run applications as the root user, which could allow an attacker to gain access to sensitive resources. To mitigate this risk, it's recommended to add a securityContext to the container, with the parameter runAsNonRoot set to true. This will ensure that the container runs as a non-root user, limiting the damage that could be caused by any potential attacks. By adding a securityContext to the container in your Kubernetes pod, you can help to ensure that your containerized applications are more secure and less vulnerable to privilege escalation attacks.

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Defintion

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rules:
  - id: run-as-non-root
    patterns:
      - pattern-inside: |
          $SPEC:
            ...
            containers:
              ...
            ...
      - metavariable-regex:
          metavariable: $SPEC
          regex: ^(spec)$
      - pattern-not-inside: |
          spec:
            ...
            securityContext:
              ...
            ...
      - pattern-inside: |
          $SPEC:
            ...
            containers:
              ...
      - pattern-not-inside: |
          $SPEC:
            ...
            containers:
              ...
              - name: $NAME
                image: ...
                ...
                securityContext:
                  ...
                  runAsNonRoot: $VALUE
      - focus-metavariable: $SPEC
    fix: |
      $SPEC:
        securityContext:
          runAsNonRoot: true #
    message: When running containers in Kubernetes, it's important to ensure that
      they  are properly secured to prevent privilege escalation attacks.  One
      potential vulnerability is when a container is allowed to
      run  applications as the root user, which could allow an attacker to
      gain  access to sensitive resources. To mitigate this risk, it's
      recommended to  add a `securityContext` to the container, with the
      parameter `runAsNonRoot`  set to `true`. This will ensure that the
      container runs as a non-root user,  limiting the damage that could be
      caused by any potential attacks. By  adding a `securityContext` to the
      container in your Kubernetes pod, you can  help to ensure that your
      containerized applications are more secure and  less vulnerable to
      privilege escalation attacks.
    metadata:
      references:
        - https://kubernetes.io/blog/2016/08/security-best-practices-kubernetes-deployment/
        - https://kubernetes.io/docs/concepts/policy/pod-security-policy/
        - https://cheatsheetseries.owasp.org/cheatsheets/Docker_Security_Cheat_Sheet.html#rule-2-set-a-user
      category: security
      cwe:
        - "CWE-250: Execution with Unnecessary Privileges"
      owasp:
        - A05:2021 - Security Misconfiguration
        - A06:2017 - Security Misconfiguration
      technology:
        - kubernetes
      subcategory:
        - audit
      likelihood: LOW
      impact: LOW
      confidence: LOW
      license: Commons Clause License Condition v1.0[LGPL-2.1-only]
    languages:
      - yaml
    severity: INFO

Examples

run-as-non-root.test.yaml

---
apiVersion: v1
kind: Pod
# ruleid: run-as-non-root
spec:
  containers:
    - name: nginx
      image: nginx
    - name: postgres
      image: postgres
      securityContext:
        runAsUser: 1000
        runAsGroup: 3000
        fsGroup: 2000
    - name: haproxy
      image: haproxy
---
apiVersion: v1
kind: Pod
# this is ok because runAsNonRoot defined at container level: fix other containers at that level
# ok: run-as-non-root
spec:
  containers:
    - name: nginx
      image: nginx
    - name: postgres
      image: postgres
      securityContext:
        runAsUser: 1000
        runAsGroup: 3000
        fsGroup: 2000
    - name: haproxy
      image: haproxy
      securityContext:
        runAsNonRoot: true
---
apiVersion: v1
kind: Pod
spec:
  # this is ok because securityContext defined at pod level already: different fix needed
  # ok: run-as-non-root
  securityContext:
    runAsGroup: 3000
  containers:
    - name: nginx
      image: nginx
    - name: postgres
      image: postgres
      securityContext:
        runAsUser: 1000
        runAsGroup: 3000
        fsGroup: 2000
    - name: haproxy
      image: haproxy
---
apiVersion: v1
kind: Pod
spec:
  # this is ok because runAsNonRoot defined at pod level already
  # ok: run-as-non-root
  securityContext:
    runAsNonRoot: true
  containers:
    - name: nginx
      image: nginx
    - name: postgres
      image: postgres
      securityContext:
        runAsUser: 1000
        runAsGroup: 3000
        fsGroup: 2000
    - name: haproxy
      image: haproxy