autohandai/auditing-kubernetes-rbac-permissions

Auditing Kubernetes RBAC Permissions

Overview

Kubernetes Role-Based Access Control (RBAC) auditing systematically reviews roles, cluster roles, bindings, and service account permissions to identify overly permissive access, privilege escalation paths, and violations of least-privilege principles. Tools like rbac-tool, KubiScan, and rakkess automate discovery of dangerous permission combinations.

Prerequisites

• Kubernetes cluster with RBAC enabled (default since 1.6)
• kubectl with cluster-admin access for full audit
• rbac-tool, rakkess, or KubiScan installed

Core Concepts

RBAC Components

| Resource | Scope | Purpose | |----------|-------|---------| | Role | Namespace | Grants permissions within a namespace | | ClusterRole | Cluster | Grants permissions cluster-wide | | RoleBinding | Namespace | Binds Role/ClusterRole to subjects in namespace | | ClusterRoleBinding | Cluster | Binds ClusterRole to subjects cluster-wide |

Dangerous Permission Combinations

| Permission | Risk | Impact | |-----------|------|--------| | * on * resources | Critical | Equivalent to cluster-admin | | create pods | High | Can deploy privileged pods | | create pods/exec | High | Can exec into any pod | | get secrets | High | Can read all secrets | | create clusterrolebindings | Critical | Can escalate to cluster-admin | | impersonate users | Critical | Can act as any user | | escalate on roles | Critical | Can grant permissions beyond own | | bind on roles | High | Can create new role bindings |

Implementation Steps

Step 1: Enumerate All RBAC Resources

# List all ClusterRoles
kubectl get clusterroles -o name | wc -l
kubectl get clusterroles --no-headers | grep -v "system:"

# List all ClusterRoleBindings
kubectl get clusterrolebindings -o wide

# List all Roles per namespace
kubectl get roles -A

# List all RoleBindings per namespace
kubectl get rolebindings -A -o wide

# Export all RBAC for offline analysis
kubectl get clusterroles,clusterrolebindings,roles,rolebindings -A -o yaml > rbac-export.yaml

Step 2: Identify Wildcard Permissions

# Find ClusterRoles with wildcard verbs on all resources
kubectl get clusterroles -o json | jq -r '
  .items[] |
  select(.rules[]? |
    (.verbs | index("*")) and
    (.resources | index("*"))
  ) |
  .metadata.name'

# Find roles that can create pods
kubectl get clusterroles -o json | jq -r '
  .items[] |
  select(.rules[]? |
    (.verbs | index("create") or index("*")) and
    (.resources | index("pods") or index("*"))
  ) |
  .metadata.name'

# Find roles that can read secrets
kubectl get clusterroles -o json | jq -r '
  .items[] |
  select(.rules[]? |
    (.verbs | index("get") or index("list") or index("*")) and
    (.resources | index("secrets") or index("*"))
  ) |
  .metadata.name'

Step 3: Check Service Account Permissions

# List all service accounts
kubectl get serviceaccounts -A

# Check permissions for default service accounts
for ns in $(kubectl get ns -o jsonpath='{.items[*].metadata.name}'); do
  echo "=== $ns/default ==="
  kubectl auth can-i --list --as=system:serviceaccount:$ns:default 2>/dev/null | grep -v "no"
done

# Check for service accounts with cluster-admin
kubectl get clusterrolebindings -o json | jq -r '
  .items[] |
  select(.roleRef.name == "cluster-admin") |
  {binding: .metadata.name, subjects: [.subjects[]? | {kind, name, namespace}]}'

Step 4: Use rbac-tool for Automated Analysis

# Install rbac-tool
kubectl krew install rbac-tool

# Visualize RBAC
kubectl rbac-tool viz --outformat dot | dot -Tpng > rbac-graph.png

# Find who can perform specific actions
kubectl rbac-tool who-can get secrets -A
kubectl rbac-tool who-can create pods -A
kubectl rbac-tool who-can '*' '*'

# Analyze all permissions
kubectl rbac-tool analysis

# Generate RBAC policy report
kubectl rbac-tool auditgen > rbac-audit.yaml

Step 5: Check for Privilege Escalation Paths

# Check if any role can escalate privileges
kubectl get clusterroles -o json | jq -r '
  .items[] |
  select(.rules[]? |
    (.verbs | index("escalate") or index("bind") or index("impersonate")) and
    (.resources | index("clusterroles") or index("roles") or index("clusterrolebindings") or index("rolebindings") or index("users") or index("groups") or index("serviceaccounts"))
  ) |
  .metadata.name'

# Check for impersonation permissions
kubectl get clusterroles -o json | jq -r '
  .items[] |
  select(.rules[]? |
    (.verbs | index("impersonate"))
  ) |
  {name: .metadata.name, rules: .rules}'

Step 6: Audit with KubiScan

# Install KubiScan
pip install kubiscan

# Find risky roles
kubiscan --risky-roles

# Find risky ClusterRoles
kubiscan --risky-clusterroles

# Find risky subjects
kubiscan --risky-subjects

# Find pods with risky service accounts
kubiscan --risky-pods

# Full report
kubiscan --all

Validation Commands

# Verify specific permission
kubectl auth can-i create pods --as=system:serviceaccount:default:myapp

# Check all permissions for a user
kubectl auth can-i --list [email protected]

# Validate RBAC with kubescape
kubescape scan framework nsa --controls-config rbac-controls.json

# Test least privilege
kubectl auth can-i delete nodes --as=system:serviceaccount:app:web-server
# Expected: no

References

• Kubernetes RBAC Documentation
• rbac-tool GitHub
• KubiScan - Risky Permissions Scanner
• CIS Kubernetes Benchmark - Section 5.1