Bài 18: Container & Kubernetes Security Testing

Performance Testing & Pentest: Quy trình Chuẩn Doanh nghiệp 2026

Phần 4: Pentest Nâng cao — Cloud, Container & AI

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1. Container Threat Landscape

Container Attack Surface:

Build Time:
  ├── Malicious base images
  ├── Vulnerable dependencies
  ├── Hardcoded secrets in Dockerfile
  └── Unsigned images

Runtime:
  ├── Container escape (privileged mode)
  ├── Host filesystem access
  ├── Network namespace attacks
  ├── Resource exhaustion
  └── Cryptomining

Orchestration (Kubernetes):
  ├── RBAC misconfiguration
  ├── Exposed API server
  ├── etcd without auth
  ├── Kubelet unauthenticated
  ├── Pod-to-pod attacks
  └── Service account token abuse

Supply Chain:
  ├── Compromised base images
  ├── Typosquatting in registries
  ├── CI/CD pipeline poisoning
  └── Unsigned artifacts

2. Docker Security Testing

# --- Image scanning with Trivy ---

# Scan image for vulnerabilities
trivy image --severity HIGH,CRITICAL myapp:latest

# Scan with SBOM output
trivy image --format cyclonedx --output sbom.json myapp:latest

# Scan Dockerfile for misconfigurations
trivy config Dockerfile

# Scan filesystem
trivy fs --scanners vuln,secret,misconfig ./

# --- Docker Bench Security ---
# CIS Docker Benchmark automated checker
docker run --rm --net host --pid host \
  --userns host --cap-add audit_control \
  -e DOCKER_CONTENT_TRUST=$DOCKER_CONTENT_TRUST \
  -v /etc:/etc:ro \
  -v /usr/bin/containerd:/usr/bin/containerd:ro \
  -v /usr/bin/runc:/usr/bin/runc:ro \
  -v /usr/lib/systemd:/usr/lib/systemd:ro \
  -v /var/lib:/var/lib:ro \
  -v /var/run/docker.sock:/var/run/docker.sock:ro \
  docker/docker-bench-security

# --- Container Escape Techniques ---

# Check if running in privileged mode
cat /proc/1/status | grep CapEff
# CapEff: 0000003fffffffff = PRIVILEGED!

# Check if Docker socket is mounted
ls -la /var/run/docker.sock
# If accessible → can create privileged containers

# Escape via Docker socket
docker -H unix:///var/run/docker.sock run -it \
  --privileged --pid=host \
  -v /:/host \
  alpine chroot /host

# Check for sensitive mounts
mount | grep -E "(proc|sys|dev)"
cat /proc/1/cgroup | grep docker

# Check capabilities
capsh --print
# Look for: cap_sys_admin, cap_sys_ptrace, cap_net_admin

# --- Secure Dockerfile ---
# ❌ Insecure
FROM ubuntu:latest
RUN apt-get update && apt-get install -y python3
COPY . /app
USER root
CMD ["python3", "/app/main.py"]

# ✅ Secure
FROM python:3.12-slim AS builder
WORKDIR /app
COPY requirements.txt .
RUN pip install --no-cache-dir -r requirements.txt

FROM gcr.io/distroless/python3-debian12
WORKDIR /app
COPY --from=builder /usr/local/lib/python3.12/site-packages /usr/local/lib/python3.12/site-packages
COPY --chown=65534:65534 . .
USER 65534
HEALTHCHECK --interval=30s --timeout=3s CMD ["python3", "-c", "import urllib.request; urllib.request.urlopen('http://localhost:8080/health')"]
CMD ["main.py"]

3. Kubernetes Security Testing

# --- K8s Enumeration ---

# Check current permissions
kubectl auth can-i --list
kubectl auth can-i create pods
kubectl auth can-i get secrets

# List all namespaces
kubectl get namespaces

# Get service account tokens
kubectl get secrets -A -o json | jq '.items[] | select(.type=="kubernetes.io/service-account-token") | .metadata.name'

# Check RBAC
kubectl get clusterrolebindings -o json | jq '.items[] | select(.subjects[]?.name=="system:anonymous")'

# Check pod security
kubectl get pods -A -o json | jq '.items[] | select(.spec.containers[].securityContext.privileged==true) | .metadata.name'

# --- kube-hunter — K8s pentest tool ---
# Run from inside the cluster
kubectl run kube-hunter --image=aquasec/kube-hunter \
  --restart=Never --command -- kube-hunter --pod

# Run from outside
docker run --rm aquasec/kube-hunter --remote 

# --- kubeaudit ---
kubeaudit all -f deployment.yaml
kubeaudit all  # Audit entire cluster

# --- Common K8s Misconfigurations ---

# 1. Check if API server is exposed
curl -k https://:6443/api/v1/namespaces
# If returns data without auth → critical!

# 2. Check kubelet
curl -sk https://:10250/pods
# Unauthenticated kubelet → can execute in pods

# 3. Check etcd
etcdctl --endpoints=http://:2379 get / --prefix --keys-only
# Unprotected etcd → can read ALL cluster secrets

# 4. Service account token in pod
cat /var/run/secrets/kubernetes.io/serviceaccount/token
# Use this token to access K8s API from within pod

# 5. Check for hostPath mounts
kubectl get pods -A -o json | jq '.items[] | 
  select(.spec.volumes[]?.hostPath != null) | 
  {name: .metadata.name, paths: [.spec.volumes[] | select(.hostPath) | .hostPath.path]}'

4. Falco — Runtime Security

# Falco rules for runtime threat detection
# /etc/falco/custom_rules.yaml

- rule: Container Escape Attempt
  desc: Detect attempts to escape container
  condition: >
    spawned_process and container and
    (proc.name in (nsenter, unshare) or
     proc.cmdline contains "chroot /host" or
     proc.cmdline contains "/proc/1/root")
  output: >
    Container escape attempt detected
    (user=%user.name command=%proc.cmdline
     container=%container.name image=%container.image.repository)
  priority: CRITICAL
  tags: [container, escape]

- rule: Crypto Mining Detection
  desc: Detect crypto mining processes
  condition: >
    spawned_process and container and
    (proc.name in (xmrig, minerd, minergate, cpuminer) or
     proc.cmdline contains "stratum+tcp" or
     proc.cmdline contains "mining.pool")
  output: >
    Crypto mining detected
    (user=%user.name command=%proc.cmdline
     container=%container.name)
  priority: CRITICAL
  tags: [container, cryptomining]

- rule: Sensitive File Access
  desc: Detect access to sensitive files
  condition: >
    open_read and container and
    (fd.name startswith /etc/shadow or
     fd.name startswith /etc/passwd or
     fd.name startswith /proc/1/ or
     fd.name contains serviceaccount/token)
  output: >
    Sensitive file accessed
    (user=%user.name file=%fd.name
     container=%container.name)
  priority: HIGH
  tags: [container, filesystem]

# Deploy Falco on Kubernetes
# helm install
helm repo add falcosecurity https://falcosecurity.github.io/charts
helm install falco falcosecurity/falco \
  --namespace falco --create-namespace \
  --set falcosidekick.enabled=true \
  --set falcosidekick.config.slack.webhookurl="https://hooks.slack.com/..." \
  --set falcosidekick.config.slack.minimumpriority="warning"

5. Supply Chain Security

# --- Image signing with Cosign ---
# Sign image
cosign sign --key cosign.key myregistry.com/myapp:v1.0

# Verify signature
cosign verify --key cosign.pub myregistry.com/myapp:v1.0

# --- SBOM generation ---
# Syft — SBOM generator
syft myapp:latest -o cyclonedx-json > sbom.json

# Grype — vulnerability scanner using SBOM
grype sbom:sbom.json --by-cve --fail-on high

# --- Admission control ---
# Kyverno policy — require signed images

# kyverno-policy.yaml — Require image signatures
apiVersion: kyverno.io/v1
kind: ClusterPolicy
metadata:
  name: verify-image-signature
spec:
  validationFailureAction: Enforce
  background: false
  rules:
    - name: verify-cosign-signature
      match:
        any:
          - resources:
              kinds:
                - Pod
      verifyImages:
        - imageReferences:
            - "myregistry.com/*"
          attestors:
            - entries:
                - keys:
                    publicKeys: |-
                      -----BEGIN PUBLIC KEY-----
                      MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAE...
                      -----END PUBLIC KEY-----

6. K8s Security Checklist

Kubernetes Pentest Checklist:

API Server:
  □ Authentication required (no anonymous access)
  □ RBAC enforced (no permissive ClusterRoleBindings)
  □ Audit logging enabled
  □ API server not publicly exposed

Workloads:
  □ No privileged containers
  □ No host namespace sharing (PID, Network, IPC)
  □ No hostPath volume mounts
  □ Resource limits set (CPU, memory)
  □ Read-only root filesystem
  □ Non-root user (runAsNonRoot: true)
  □ Drop all capabilities, add only needed

Network:
  □ Network Policies applied (deny by default)
  □ Pod-to-pod communication restricted
  □ Ingress TLS configured
  □ Service mesh with mTLS

Secrets:
  □ Secrets encrypted at rest (EncryptionConfiguration)
  □ External secret management (Vault, AWS SM)
  □ No secrets in environment variables
  □ Service account tokens auto-mounted only when needed

Supply Chain:
  □ Images from trusted registries only
  □ Image signatures verified (Cosign + admission)
  □ Base images regularly updated
  □ SBOM generated and scanned

7. Tổng kết

• Docker: Trivy scanning, Docker Bench, container escape detection
• Kubernetes: RBAC audit, API server, kubelet, etcd security
• Falco: Runtime threat detection — escape, cryptomining, sensitive access
• Supply Chain: Cosign signing, SBOM, Kyverno admission control
• Defense: Non-root, drop capabilities, network policies, encrypted secrets

Bài tiếp theo sẽ tập trung vào API Security Testing — OWASP API Top 10.