Container Security Checker

Purpose & When-To-Use

Trigger conditions:

• Container security audit before production deployment
• Kubernetes cluster security review
• CIS Benchmark compliance requirement
• Post-incident container security assessment
• Third-party container security questionnaire

Not for:

• Image vulnerability scanning (use dedicated SBOM/CVE scanning tools)
• Runtime threat detection (use container runtime security tools)
• Application security (use security-appsec-validator)
• Cloud infrastructure security (use security-cloud-analyzer)

Pre-Checks

Time normalization:

• Compute NOW_ET using NIST/time.gov semantics (America/New_York, ISO-8601): 2025-10-26T01:33:55-04:00
• Use NOW_ET for all citation access dates

Input validation:

• platform must be one of: [docker, kubernetes, both]
• check_scope must be one of: [images, runtime, rbac, network, all]
• If platform includes kubernetes, cluster_identifier should be provided

Source freshness:

• CIS Docker Benchmark (accessed 2025-10-26T01:33:55-04:00): https://www.cisecurity.org/benchmark/docker
• CIS Kubernetes Benchmark v1.8+ (accessed 2025-10-26T01:33:55-04:00): https://www.cisecurity.org/benchmark/kubernetes
• Pod Security Standards (accessed 2025-10-26T01:33:55-04:00): https://kubernetes.io/docs/concepts/security/pod-security-standards/

Procedure

Step 1: Critical Container Security Controls

Docker/Container Images:

1. Container images from trusted registries (verified signatures)
2. Non-root user execution (USER directive in Dockerfile)
3. No secrets in environment variables or image layers
4. Resource limits defined (memory, CPU)

Kubernetes Pod Security:

1. Pod Security Standards enforcement (Baseline or Restricted level)
2. Non-privileged containers (securityContext.privileged: false)
3. Read-only root filesystem where possible
4. No host namespace sharing (hostNetwork, hostPID, hostIPC: false)

Kubernetes RBAC:

1. Role bindings follow least privilege principle
2. No wildcard permissions in Roles/ClusterRoles
3. Service accounts scoped to namespaces
4. Minimal ClusterRole bindings

Kubernetes Network Security:

1. Network policies defined for namespace isolation
2. Ingress and egress rules explicit (no default allow-all)
3. Service mesh security (if applicable)

Step 2: Generate CIS-Aligned Remediation

For each finding, provide:

• CIS Benchmark control reference
• Kubernetes YAML manifest fixes or Dockerfile changes
• Platform-specific commands (kubectl, docker)

Token budgets:

• T1: ≤2k tokens (critical findings)
• T2: ≤6k tokens (full CIS coverage)
• T3: Not applicable for this skill (use security-auditor agent for comprehensive assessments)

Decision Rules

Ambiguity thresholds:

• If cluster access unavailable → request kubeconfig or architecture docs
• If Dockerfile unavailable → assess runtime configuration only

Abort conditions:

• No platform specified → cannot proceed
• Kubernetes platform selected but no cluster access → limited to manifest review

Severity classification:

• Critical: Privileged containers, host namespace sharing (CVSS 9.0-10.0)
• High: Weak RBAC, missing network policies (CVSS 7.0-8.9)
• Medium: Resource limits missing, root user (CVSS 4.0-6.9)
• Low: Best practice deviations (CVSS 0.1-3.9)

Output Contract

Required fields:

{
  "platform": "docker|kubernetes|both",
  "cluster_identifier": "string or null",
  "check_scope": "images|runtime|rbac|network|all",
  "timestamp": "ISO-8601 with timezone",
  "findings": [
    {
      "id": "unique identifier",
      "check_type": "image|pod|rbac|network",
      "resource_type": "pod|deployment|role|networkpolicy|...",
      "resource_name": "resource identifier",
      "severity": "critical|high|medium|low",
      "cvss_score": 0.0,
      "title": "brief description",
      "description": "detailed finding",
      "cis_control": "CIS Docker 4.1 or CIS Kubernetes 5.2.3",
      "remediation": "specific fix steps",
      "remediation_manifest": "YAML or Dockerfile snippet"
    }
  ],
  "cis_compliance": {
    "benchmark": "CIS Docker v1.6.0 or CIS Kubernetes v1.8.0",
    "controls_assessed": ["list"],
    "controls_passed": ["list"],
    "controls_failed": ["list"]
  },
  "summary": {
    "total_findings": 0,
    "critical_count": 0,
    "high_count": 0,
    "overall_risk": "critical|high|medium|low"
  }
}

Examples

Example: Kubernetes Pod Security Check

# Input
platform: "kubernetes"
cluster_identifier: "prod-cluster-us-east"
check_scope: "runtime"

# Output (abbreviated)
{
  "platform": "kubernetes",
  "findings": [
    {
      "id": "CONTAINER-001",
      "check_type": "pod",
      "resource_name": "web-app-deployment",
      "severity": "high",
      "cvss_score": 7.5,
      "title": "Privileged container detected",
      "cis_control": "CIS Kubernetes 5.2.1",
      "remediation_manifest": "securityContext:\\n  privileged: false"
    }
  ],
  "summary": {"high_count": 1, "overall_risk": "high"}
}

Quality Gates

Token budgets:

• T1 ≤2k tokens (critical findings only)
• T2 ≤6k tokens (full CIS Benchmark coverage)

Safety:

• No secrets in remediation manifests
• No actual cluster credentials

Auditability:

• Findings cite CIS Benchmark controls
• CVSS scores follow CVSSv3.1 methodology

Determinism:

• Same cluster state + inputs = consistent findings

Resources

CIS Benchmarks:

• CIS Docker Benchmark: https://www.cisecurity.org/benchmark/docker (accessed 2025-10-26T01:33:55-04:00)
• CIS Kubernetes Benchmark: https://www.cisecurity.org/benchmark/kubernetes (accessed 2025-10-26T01:33:55-04:00)

Kubernetes Security:

• Pod Security Standards: https://kubernetes.io/docs/concepts/security/pod-security-standards/ (accessed 2025-10-26T01:33:55-04:00)
• Kubernetes Security Best Practices: https://kubernetes.io/docs/concepts/security/ (accessed 2025-10-26T01:33:55-04:00)
• RBAC Documentation: https://kubernetes.io/docs/reference/access-authn-authz/rbac/ (accessed 2025-10-26T01:33:55-04:00)

Container Security:

• Docker Security Best Practices: https://docs.docker.com/engine/security/ (accessed 2025-10-26T01:33:55-04:00)
• Network Policies: https://kubernetes.io/docs/concepts/services-networking/network-policies/ (accessed 2025-10-26T01:33:55-04:00)