Agent skill

implementing-runtime-security-with-tetragon

Implement eBPF-based runtime security observability and enforcement in Kubernetes clusters using Cilium Tetragon for kernel-level threat detection and policy enforcement.

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SKILL.md

Implementing Runtime Security with Tetragon

Overview

Tetragon is a CNCF project under Cilium that provides flexible Kubernetes-aware security observability and runtime enforcement using eBPF. By operating at the Linux kernel level, Tetragon can monitor and enforce policies on process execution, file access, network connections, and system calls with less than 1% performance overhead -- far more efficient than traditional user-space security agents.

Prerequisites

  • Kubernetes cluster v1.24+ with Helm 3.x installed
  • Linux kernel 5.4+ (5.10+ recommended for full eBPF feature support)
  • kubectl access with cluster-admin privileges
  • Familiarity with eBPF concepts and Kubernetes security primitives

Core Concepts

eBPF-Based Security

Tetragon attaches eBPF programs directly to kernel functions, enabling:

  • Process lifecycle tracking: Monitor every process creation, execution, and termination across all pods
  • File integrity monitoring: Detect unauthorized reads/writes to sensitive files
  • Network observability: Track all TCP/UDP connections with full pod context
  • System call filtering: Enforce policies on dangerous syscalls like ptrace, mount, or unshare

TracingPolicy Custom Resources

Tetragon uses TracingPolicy CRDs to define what kernel events to observe and what actions to take:

yaml
apiVersion: cilium.io/v1alpha1
kind: TracingPolicy
metadata:
  name: detect-privilege-escalation
spec:
  kprobes:
    - call: "security_bprm_check"
      syscall: false
      args:
        - index: 0
          type: "linux_binprm"
      selectors:
        - matchBinaries:
            - operator: "In"
              values:
                - "/bin/su"
                - "/usr/bin/sudo"
                - "/usr/bin/passwd"
          matchNamespaces:
            - namespace: Pid
              operator: NotIn
              values:
                - "host_ns"
          matchActions:
            - action: Post

Enforcement Actions

Tetragon can take three types of actions directly in the kernel:

  1. Sigkill: Immediately terminate the offending process
  2. Signal: Send a configurable signal to the process
  3. Override: Override the return value of a kernel function to deny an operation

Installation and Configuration

Step 1: Install Tetragon with Helm

bash
helm repo add cilium https://helm.cilium.io
helm repo update

helm install tetragon cilium/tetragon \
  --namespace kube-system \
  --set tetragon.enableProcessCred=true \
  --set tetragon.enableProcessNs=true \
  --set tetragon.grpc.address="localhost:54321"

Step 2: Install the Tetragon CLI

bash
GOOS=$(go env GOOS)
GOARCH=$(go env GOARCH)
curl -L --remote-name-all \
  https://github.com/cilium/tetragon/releases/latest/download/tetra-${GOOS}-${GOARCH}.tar.gz
tar -xzvf tetra-${GOOS}-${GOARCH}.tar.gz
sudo install tetra /usr/local/bin/

Step 3: Verify Installation

bash
kubectl get pods -n kube-system -l app.kubernetes.io/name=tetragon
tetra status

Practical Implementation

Detecting Container Escape Attempts

Create a TracingPolicy to detect processes attempting to escape container namespaces:

yaml
apiVersion: cilium.io/v1alpha1
kind: TracingPolicy
metadata:
  name: detect-container-escape
spec:
  kprobes:
    - call: "__x64_sys_setns"
      syscall: true
      args:
        - index: 0
          type: "int"
        - index: 1
          type: "int"
      selectors:
        - matchNamespaces:
            - namespace: Pid
              operator: NotIn
              values:
                - "host_ns"
          matchActions:
            - action: Sigkill

Monitoring Sensitive File Access

Detect reads of sensitive credentials:

yaml
apiVersion: cilium.io/v1alpha1
kind: TracingPolicy
metadata:
  name: monitor-sensitive-files
spec:
  kprobes:
    - call: "security_file_open"
      syscall: false
      args:
        - index: 0
          type: "file"
      selectors:
        - matchArgs:
            - index: 0
              operator: "Prefix"
              values:
                - "/etc/shadow"
                - "/etc/kubernetes/pki"
                - "/var/run/secrets/kubernetes.io"
          matchActions:
            - action: Post

Blocking Crypto-Miner Execution

Prevent known crypto-mining binaries from executing:

yaml
apiVersion: cilium.io/v1alpha1
kind: TracingPolicy
metadata:
  name: block-cryptominers
spec:
  kprobes:
    - call: "security_bprm_check"
      syscall: false
      args:
        - index: 0
          type: "linux_binprm"
      selectors:
        - matchBinaries:
            - operator: "In"
              values:
                - "/usr/bin/xmrig"
                - "/tmp/xmrig"
                - "/usr/bin/minerd"
          matchActions:
            - action: Sigkill

Observing Events with Tetra CLI

Stream runtime events in real-time:

bash
# Watch all process execution events
kubectl exec -n kube-system ds/tetragon -c tetragon -- \
  tetra getevents -o compact --process-only

# Filter events for a specific namespace
kubectl exec -n kube-system ds/tetragon -c tetragon -- \
  tetra getevents -o compact --namespace production

# Export events in JSON for SIEM integration
kubectl exec -n kube-system ds/tetragon -c tetragon -- \
  tetra getevents -o json | tee /var/log/tetragon-events.json

Integration with SIEM and Alerting

Export to Elasticsearch

yaml
# tetragon-helm-values.yaml
export:
  stdout:
    enabledCommand: true
    enabledArgs: true
  filenames:
    - /var/log/tetragon/tetragon.log
  elasticsearch:
    enabled: true
    url: "https://elasticsearch.monitoring:9200"
    index: "tetragon-events"

Prometheus Metrics

Tetragon exposes metrics at :2112/metrics:

yaml
apiVersion: monitoring.coreos.com/v1
kind: ServiceMonitor
metadata:
  name: tetragon-metrics
  namespace: kube-system
spec:
  selector:
    matchLabels:
      app.kubernetes.io/name: tetragon
  endpoints:
    - port: metrics
      interval: 15s

Key Metrics and Alerts

Metric Description Alert Threshold
tetragon_events_total Total security events observed Spike > 3x baseline
tetragon_policy_events_total Events matching TracingPolicies Any Sigkill action
tetragon_process_exec_total Process executions tracked Anomalous new binaries
tetragon_missed_events_total Dropped events due to buffer overflow > 0 sustained

References

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