detecting-privilege-escalation-in-kubernetes-pods

# Detecting Privilege Escalation in Kubernetes Pods ## Overview Privilege escalation in Kubernetes occurs when a pod or container gains elevated permissions beyond its intended scope. This includes running as root, using privileged mode, mounting host filesystems, enabling dangerous Linux capabilities, or exploiting kernel vulnerabilities. Detection combines admission control (prevention), runtime monitoring (detection), and audit logging (investigation). ## Prerequisites - Kubernetes cluster v1.25+ (Pod Security Admission support) - kubectl with cluster-admin access - Falco or similar runtime security tool - OPA Gatekeeper or Kyverno for admission policies ## Privilege Escalation Vectors in Kubernetes | Vector | Risk | Detection Method | |--------|------|-----------------| | privileged: true | Full host access | Admission control + audit | | hostPID: true | Access host processes | Admission control | | hostNetwork: true | Access host network stack | Admission control | | hostPath volumes | Read/write host filesystem | Admission control | | SYS_ADMIN capability | Near-privileged access | Admission + runtime | | allowPrivilegeEscalation: true | setuid/setgid exploitation | Admission control | | runAsUser: 0 | Container root | Admission control | | automountServiceAccountToken | Token theft for API access | Admission control | | Writable /proc or /sys | Kernel parameter manipulation | Runtime monitoring | ## Detection with Admission Control ### Pod Security Admission (Built-in) ```yaml # Enforce restricted policy on namespace apiVersion: v1 kind: Namespace metadata: name: production labels: pod-security.kubernetes.io/enforce: restricted pod-security.kubernetes.io/enforce-version: latest pod-security.kubernetes.io/audit: restricted pod-security.kubernetes.io/warn: restricted ``` ### OPA Gatekeeper Policies ```yaml # Block dangerous capabilities apiVersion: templates.gatekeeper.sh/v1 kind: ConstraintTemplate metadata: name: k8sdangerouspriv spec: crd: spec: names: kind: K8sDangerousPriv targets: - target: admission.k8s.gatekeeper.sh rego: | package k8sdangerouspriv dangerous_caps := {"SYS_ADMIN", "SYS_PTRACE", "SYS_MODULE", "DAC_OVERRIDE", "NET_ADMIN", "NET_RAW"} violation[{"msg": msg}] { container := input.review.object.spec.containers[_] cap := container.securityContext.capabilities.add[_] dangerous_caps[cap] msg := sprintf("Container %v adds dangerous capability: %v", [container.name, cap]) } violation[{"msg": msg}] { container := input.review.object.spec.containers[_] container.securityContext.privileged == true msg := sprintf("Container %v runs in privileged mode", [container.name]) } violation[{"msg": msg}] { container := input.review.object.spec.containers[_] container.securityContext.allowPrivilegeEscalation == true msg := sprintf("Container %v allows privilege escalation", [container.name]) } violation[{"msg": msg}] { input.review.object.spec.hostPID == true msg := "Pod uses host PID namespace" } violation[{"msg": msg}] { input.review.object.spec.hostNetwork == true msg := "Pod uses host network" } ``` ## Runtime Detection with Falco ```yaml # /etc/falco/rules.d/privesc-detection.yaml - rule: Setuid Binary Execution in Container desc: Detect execution of setuid/setgid binaries in a container condition: > spawned_process and container and (proc.name in (su, sudo, newgrp, chsh, passwd) or proc.is_exe_upper_layer=true) output: > Setuid/setgid binary executed in container (user=%user.name container=%container.name image=%container.image.repository command=%proc.cmdline parent=%proc.pname) priority: WARNING tags: [container, privilege-escalation, T1548] - rule: Capability Gained in Container desc: Detect when a process gains elevated capabilities condition: > evt.type = capset and container and evt.arg.cap != "" output: > Process gained capabilities in container (container=%container.name image=%container.image.repository capabilities=%evt.arg.cap command=%proc.cmdline) priority: WARNING tags: [container, privilege-escalation, T1548.001] - rule: Container with Dangerous Capabilities Started desc: Detect container launched with dangerous capabilities condition: > container_started and container and (container.image.repository != "registry.k8s.io/pause") and (container.cap_effective contains SYS_ADMIN or container.cap_effective contains SYS_PTRACE or container.cap_effective contains SYS_MODULE) output: > Container with dangerous capabilities (container=%container.name image=%container.image.repository caps=%container.cap_effective) priority: CRITICAL tags: [container, privilege-escalation, T1068] - rule: Write to /etc/passwd in Container desc: Detect writes to /etc/passwd inside container condition: > open_write and container and fd.name = /etc/passwd output: > Write to /etc/passwd in container (container=%container.name image=%container.image.repository command=%proc.cmdline user=%user.name) priority: CRITICAL tags: [container, privilege-escalation, T1136] ``` ## Kubernetes Audit Log Detection ```yaml # audit-policy.yaml - Capture privilege escalation events apiVersion: audit.k8s.io/v1 kind: Policy rules: # Log pod creation with security context details - level: RequestResponse resources: - group: "" resources: ["pods"] verbs: ["create", "update", "patch"] # Log privilege escalation attempts - level: RequestResponse resources: - group: "rbac.authorization.k8s.io" resources: ["clusterroles", "clusterrolebindings", "roles", "rolebindings"] verbs: ["create", "update", "patch", "bind", "escalate"] # Log service account token requests - level: Metadata resources: - group: "" resources: ["serviceaccounts/token"] verbs: ["create"] ``` ### Query Audit Logs for Privilege Escalation ```bash # Find pods created with privileged security context kubectl logs -n kube-system kube-apiserver-* | \ jq 'select(.verb == "create" and .objectRef.resource == "pods") | select(.requestObject.spec.containers[].securityContext.privileged == true)' # Find RBAC escalation attempts kubectl logs -n kube-system kube-apiserver-* | \ jq 'select(.objectRef.resource == "clusterrolebindings" and .verb == "create")' ``` ## Investigation Playbook ```bash # Check pod security context kubectl get pod <pod-name> -n <ns> -o jsonpath='{.spec.containers[*].securityContext}' # Check effective capabilities kubectl exec <pod-name> -n <ns> -- cat /proc/1/status | grep -i cap # List pods running as root kubectl get pods --all-namespaces -o json | \ jq '.items[] | select(.spec.containers[].securityContext.runAsUser == 0 or .spec.containers[].securityContext.privileged == true) | {name: .metadata.name, ns: .metadata.namespace}' # Check for hostPath volumes kubectl get pods --all-namespaces -o json | \ jq '.items[] | select(.spec.volumes[]?.hostPath != null) | {name: .metadata.name, ns: .metadata.namespace, paths: [.spec.volumes[].hostPath.path]}' ``` ## Best Practices 1. **Enable Pod Security Admission** at `restricted` level for production namespaces 2. **Drop ALL capabilities** and add back only what is needed 3. **Set allowPrivilegeEscalation: false** on all containers 4. **Run as non-root** (runAsNonRoot: true, runAsUser > 0) 5. **Disable automountServiceAccountToken** unless API access is needed 6. **Monitor with Falco** for runtime privilege escalation attempts 7. **Audit RBAC changes** with Kubernetes audit logging 8. **Use seccomp profiles** to restrict syscalls @ref(api-reference.md) @ref(standards.md) @ref(workflows.md)