hardening-docker-containers-for-production skill (Anthropic-Cybersecurity-Skills)

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What it does. Hardens Dockerfiles, images, and per-container runtime settings against the CIS Docker Benchmark v1.8.0: non-root users, dropped capabilities, read-only root filesystem, seccomp and AppArmor profiles, and minimal multi-stage builds, validated with docker-bench-security, Hadolint, and Dockle. Use when preparing a container or Dockerfile for production, or auditing images and runtime flags against CIS Docker controls. Keywords: Dockerfile, USER, --cap-drop, read-only rootfs, seccomp, AppArmor, multi-stage, Hadolint, Dockle. Do not use for the Docker daemon's own configuration - use hardening-docker-daemon-configuration. Part of mukul975/Anthropic-Cybersecurity-Skills (817 security skills) (mukul975/Anthropic-Cybersecurity-Skills).
Upstream mukul975/Anthropic-Cybersecurity-Skills
Skill file skills/hardening-docker-containers-for-production/SKILL.md
License Apache-2.0 (skill folder LICENSE)
Author mukul975
Fetched 2026-09-10

Install

  • npx skills add mukul975/Anthropic-Cybersecurity-Skills --skill hardening-docker-containers-for-production, or copy the skill folder into ~/.claude/skills/hardening-docker-containers-for-production/.
  • Raw file: curl -sL https://raw.githubusercontent.com/mukul975/Anthropic-Cybersecurity-Skills/HEAD/skills/hardening-docker-containers-for-production/SKILL.md

SKILL.md (verbatim)

name: hardening-docker-containers-for-production
description: >-
  Hardens Dockerfiles, images, and per-container runtime settings against the CIS Docker
  Benchmark v1.8.0: non-root users, dropped capabilities, read-only root filesystem, seccomp
  and AppArmor profiles, and minimal multi-stage builds, validated with docker-bench-security,
  Hadolint, and Dockle. Use when preparing a container or Dockerfile for production, or
  auditing images and runtime flags against CIS Docker controls. Keywords: Dockerfile, USER,
  --cap-drop, read-only rootfs, seccomp, AppArmor, multi-stage, Hadolint, Dockle. Do not use
  for the Docker daemon's own configuration - use hardening-docker-daemon-configuration.
domain: cybersecurity
subdomain: container-security
tags:
- containers
- docker
- security
- hardening
- CIS-benchmark
version: '1.0'
author: mahipal
license: Apache-2.0
nist_csf:
- PR.PS-01
- PR.IR-01
- ID.AM-08
- DE.CM-01
mitre_attack:
- T1610
- T1611
- T1609
- T1525
- T1068

Hardening Docker Containers for Production

Overview

Hardening Docker containers for production involves applying security best practices aligned with CIS Docker Benchmark v1.8.0 to minimize attack surface, prevent privilege escalation, and enforce least-privilege principles across Docker daemon, images, containers, and runtime configurations.

When to Use

  • When deploying or configuring hardening docker containers for production capabilities in your environment
  • When establishing security controls aligned to compliance requirements
  • When building or improving security architecture for this domain
  • When conducting security assessments that require this implementation

Prerequisites

  • Docker Engine 24.0+ installed
  • Docker Compose v2
  • Linux host with kernel 5.10+
  • Root or sudo access on Docker host
  • docker-bench-security tool
  • Hadolint for Dockerfile linting
  • Dockle for image linting

Core Concepts

CIS Docker Benchmark Sections

  1. Host Configuration - Audit Docker daemon files, restrict access to /var/run/docker.sock
  2. Docker Daemon Configuration - Enable TLS, restrict inter-container communication, configure logging
  3. Docker Daemon Configuration Files - Set ownership and permissions on daemon.json
  4. Container Images and Build File - Use trusted base images, scan for vulnerabilities, multi-stage builds
  5. Container Runtime - Drop capabilities, read-only rootfs, restrict syscalls
  6. Docker Security Operations - Monitor, audit, and rotate credentials

Key Hardening Principles

  • Least Privilege: Run containers as non-root, drop all capabilities except required
  • Immutability: Use read-only root filesystem, tmpfs for writable directories
  • Minimalism: Use distroless or Alpine base images, multi-stage builds
  • Isolation: Apply seccomp profiles, AppArmor/SELinux, namespace restrictions
  • Auditability: Enable content trust, log all container activity

Workflow

Step 1: Harden the Dockerfile

# Use specific digest for reproducibility
FROM python:3.12-slim@sha256:abc123... AS builder

WORKDIR /app
COPY requirements.txt .
RUN pip install --no-cache-dir --user -r requirements.txt

# Production stage - minimal image
FROM gcr.io/distroless/python3-debian12

# Copy only necessary artifacts
COPY --from=builder /root/.local /root/.local
COPY --from=builder /app /app

WORKDIR /app

# Create non-root user
USER 65534:65534

# Set read-only filesystem expectation
LABEL org.opencontainers.image.source="https://github.com/org/app"

ENTRYPOINT ["python", "app.py"]

Step 2: Harden Docker Daemon Configuration

{
  "icc": false,
  "log-driver": "json-file",
  "log-opts": {
    "max-size": "10m",
    "max-file": "3"
  },
  "live-restore": true,
  "userland-proxy": false,
  "no-new-privileges": true,
  "default-ulimits": {
    "nofile": {
      "Name": "nofile",
      "Hard": 64000,
      "Soft": 64000
    },
    "nproc": {
      "Name": "nproc",
      "Hard": 1024,
      "Soft": 1024
    }
  },
  "seccomp-profile": "/etc/docker/seccomp-default.json",
  "tls": true,
  "tlscacert": "/etc/docker/tls/ca.pem",
  "tlscert": "/etc/docker/tls/server-cert.pem",
  "tlskey": "/etc/docker/tls/server-key.pem",
  "tlsverify": true
}

Step 3: Harden Container Runtime

docker run -d \
  --name production-app \
  --read-only \
  --tmpfs /tmp:rw,noexec,nosuid,size=100m \
  --tmpfs /var/run:rw,noexec,nosuid,size=10m \
  --cap-drop ALL \
  --cap-add NET_BIND_SERVICE \
  --security-opt no-new-privileges:true \
  --security-opt seccomp=/etc/docker/seccomp-default.json \
  --security-opt apparmor=docker-default \
  --pids-limit 100 \
  --memory 512m \
  --memory-swap 512m \
  --cpus 1.0 \
  --user 65534:65534 \
  --network custom-bridge \
  --restart on-failure:3 \
  --health-cmd "curl -f http://localhost:8080/health || exit 1" \
  --health-interval 30s \
  --health-timeout 10s \
  --health-retries 3 \
  myapp:latest

Step 4: Enable Docker Content Trust

export DOCKER_CONTENT_TRUST=1
export DOCKER_CONTENT_TRUST_SERVER=https://notary.example.com

# Sign and push image
docker trust sign myregistry.com/myapp:v1.0.0

# Verify image signature before pull
docker trust inspect --pretty myregistry.com/myapp:v1.0.0

Step 5: Configure Host-Level Auditing

# Add audit rules for Docker files and directories
cat >> /etc/audit/rules.d/docker.rules << 'EOF'
-w /usr/bin/docker -k docker
-w /var/lib/docker -k docker
-w /etc/docker -k docker
-w /lib/systemd/system/docker.service -k docker
-w /lib/systemd/system/docker.socket -k docker
-w /etc/default/docker -k docker
-w /etc/docker/daemon.json -k docker
-w /usr/bin/containerd -k docker
-w /usr/bin/runc -k docker
EOF

systemctl restart auditd

Validation Commands

# Run Docker Bench Security
docker run --rm --net host --pid host \
  --userns host --cap-add audit_control \
  -e DOCKER_CONTENT_TRUST=$DOCKER_CONTENT_TRUST \
  -v /etc:/etc:ro \
  -v /usr/bin/containerd:/usr/bin/containerd:ro \
  -v /usr/bin/runc:/usr/bin/runc:ro \
  -v /usr/lib/systemd:/usr/lib/systemd:ro \
  -v /var/lib:/var/lib:ro \
  -v /var/run/docker.sock:/var/run/docker.sock:ro \
  docker/docker-bench-security

# Lint Dockerfile
hadolint Dockerfile

# Lint built image
dockle myapp:latest

# Verify no containers running as root
docker ps -q | xargs docker inspect --format '{{.Id}}: User={{.Config.User}}'

Key Security Controls

Control Implementation CIS Section
Non-root user USER instruction in Dockerfile 4.1
Read-only rootfs --read-only flag 5.12
Drop capabilities --cap-drop ALL 5.3
Resource limits --memory, --cpus, --pids-limit 5.10
No new privileges --security-opt no-new-privileges 5.25
Content trust DOCKER_CONTENT_TRUST=1 4.5
TLS for daemon daemon.json TLS config 2.6
Audit logging auditd rules 1.1

References

Other files in this skill

assets/template.md (verbatim)

Docker Container Hardening Assessment Template

Project Information

Field Value
Application Name
Docker Image
Base Image
Environment Development / Staging / Production
Assessment Date
Assessor

Pre-Hardening Checklist

Dockerfile Security

  • Using minimal base image (distroless, Alpine, scratch)
  • Specific image tag with digest pinning (not :latest)
  • Multi-stage build implemented
  • Non-root USER instruction present
  • COPY used instead of ADD
  • No secrets in Dockerfile or image layers
  • HEALTHCHECK instruction present
  • Unnecessary packages removed
  • setuid/setgid binaries removed

Daemon Configuration (/etc/docker/daemon.json)

  • icc set to false
  • TLS authentication enabled (tlsverify: true)
  • Live restore enabled
  • Userland proxy disabled
  • no-new-privileges enabled
  • Log rotation configured (max-size, max-file)
  • Default ulimits configured
  • Seccomp profile specified

Runtime Security Flags

  • --read-only enabled
  • --cap-drop ALL applied
  • Minimum --cap-add for required capabilities only
  • --security-opt no-new-privileges:true
  • --security-opt seccomp=<profile>
  • --memory limit set
  • --cpus limit set
  • --pids-limit set
  • --user set to non-root UID:GID
  • --tmpfs for writable directories
  • --network set to custom bridge (not host)
  • --restart on-failure with max retries

Host Security

  • Separate partition for /var/lib/docker
  • Docker group membership restricted
  • Audit rules configured for Docker files
  • Docker socket not exposed to containers
  • Content Trust enabled (DOCKER_CONTENT_TRUST=1)

Vulnerability Scan Results

Trivy Scan

trivy image <image-name>
Severity Count Action Required
CRITICAL Immediate fix
HIGH Fix before production
MEDIUM Plan remediation
LOW Accept or fix

Docker Bench Score

docker run --rm docker/docker-bench-security
Section Score Notes
Host Configuration /10
Daemon Configuration /10
Container Images /10
Container Runtime /10
Docker Security Ops /10

Risk Acceptance

Finding Severity Justification Approved By Date

Remediation Plan

Priority Finding Action Owner Target Date Status
P1
P2
P3

Sign-Off

Role Name Signature Date
Security Engineer
DevOps Lead
Application Owner

references/api-reference.md (verbatim)

API Reference: Docker Container Hardening

Docker CLI

List Containers

docker ps --format '{{json .}}'

Inspect Container

docker inspect <container_id>

Key Inspect Fields

Path Description
.HostConfig.Privileged Privileged mode
.HostConfig.NetworkMode Network namespace
.HostConfig.CapAdd Added capabilities
.HostConfig.ReadonlyRootfs Read-only filesystem
.HostConfig.Memory Memory limit (bytes)
.Config.User Container user

CIS Docker Benchmark Checks

Check Description Severity
4.1 Non-root user HIGH
5.3 Restrict capabilities HIGH
5.4 No privileged containers CRITICAL
5.5 No sensitive host mounts HIGH
5.10 No host network HIGH
5.12 Read-only root FS MEDIUM
5.13 CPU limits set LOW
5.14 Memory limits set MEDIUM

Secure Dockerfile Practices

Non-Root User

FROM alpine:3.18
RUN adduser -D appuser
USER appuser

Read-Only Filesystem

docker run --read-only --tmpfs /tmp:rw,noexec,nosuid myimage

Drop Capabilities

docker run --cap-drop ALL --cap-add NET_BIND_SERVICE myimage

Resource Limits

docker run --memory=512m --cpus=1.0 myimage

Docker Bench Security

Run Audit

docker run --rm --net host --pid host --userns host \
    --cap-add audit_control \
    -v /var/lib:/var/lib \
    -v /var/run/docker.sock:/var/run/docker.sock \
    -v /etc:/etc \
    docker/docker-bench-security

Seccomp and AppArmor

Custom Seccomp Profile

docker run --security-opt seccomp=profile.json myimage

AppArmor Profile

docker run --security-opt apparmor=docker-default myimage

references/standards.md (verbatim)

Standards Reference - Docker Container Hardening

CIS Docker Benchmark v1.8.0

Section 1: Host Configuration

  • 1.1.1: Ensure a separate partition for containers has been created
  • 1.1.2: Ensure only trusted users are allowed to control Docker daemon
  • 1.1.3-1.1.18: Ensure Docker daemon audit configuration

Section 2: Docker Daemon Configuration

  • 2.1: Run the Docker daemon as non-root user (rootless mode)
  • 2.2: Ensure network traffic is restricted between containers (--icc=false)
  • 2.3: Ensure logging level is set to info
  • 2.4: Ensure Docker is allowed to make changes to iptables
  • 2.5: Ensure insecure registries are not used
  • 2.6: Ensure aufs storage driver is not used
  • 2.7: Ensure TLS authentication for Docker daemon is configured
  • 2.8: Ensure default ulimit is configured appropriately
  • 2.9: Enable user namespace support
  • 2.10: Ensure default cgroup usage has been confirmed
  • 2.11: Ensure base device size is not changed until needed
  • 2.12: Ensure centralized and remote logging is configured
  • 2.13: Ensure live restore is enabled
  • 2.14: Ensure Userland Proxy is disabled
  • 2.15: Ensure daemon-wide custom seccomp profile is applied
  • 2.16: Ensure experimental features are not used in production
  • 2.17: Ensure containers are restricted from acquiring new privileges

Section 4: Container Images and Build Files

  • 4.1: Ensure that a user for the container has been created
  • 4.2: Ensure containers use trusted base images
  • 4.3: Ensure unnecessary packages are not installed
  • 4.4: Ensure images are scanned for vulnerabilities
  • 4.5: Ensure Content trust for Docker is enabled
  • 4.6: Ensure HEALTHCHECK instructions have been added to container images
  • 4.7: Ensure update instructions are not used alone in the Dockerfile
  • 4.8: Ensure setuid and setgid permissions are removed
  • 4.9: Ensure COPY is used instead of ADD
  • 4.10: Ensure secrets are not stored in Dockerfiles
  • 4.11: Ensure only verified packages are installed

Section 5: Container Runtime

  • 5.1: Ensure AppArmor profile is enabled
  • 5.2: Ensure SELinux security options are set
  • 5.3: Ensure Linux kernel capabilities are restricted
  • 5.4: Ensure privileged containers are not used
  • 5.5: Ensure sensitive host system directories are not mounted
  • 5.6: Ensure sshd is not running within containers
  • 5.7: Ensure privileged ports are not mapped within containers
  • 5.8: Ensure only needed ports are open on the container
  • 5.9: Ensure host network mode is not used
  • 5.10: Ensure memory usage for container is limited
  • 5.11: Ensure CPU priority is set appropriately
  • 5.12: Ensure container root filesystem is mounted as read only
  • 5.13: Ensure incoming container traffic is bound to a specific host interface
  • 5.25: Ensure container is restricted from acquiring additional privileges

NIST SP 800-190 - Application Container Security Guide

Key Recommendations

  • Use container-specific host OS (CoreOS, Flatcar, Bottlerocket)
  • Segment container networks by sensitivity level
  • Use container runtime with minimal attack surface
  • Implement image signing and verification
  • Harden container registries with access controls
  • Monitor container runtime behavior for anomalies

OWASP Docker Security Cheat Sheet

Top Docker Security Risks

  1. Unrestricted container access to host resources
  2. Running containers in privileged mode
  3. Running as root inside containers
  4. Unverified or unscanned container images
  5. Exposed Docker daemon socket
  6. Insecure container networking
  7. Secrets stored in images or environment variables
  8. Missing resource limits
  9. Outdated base images with known vulnerabilities
  10. Insufficient logging and monitoring

references/workflows.md (verbatim)

Workflows - Docker Container Hardening

Workflow 1: New Container Hardening Pipeline

[Dockerfile Created] --> [Hadolint Lint] --> [Build Image] --> [Dockle Scan]
        |                      |                    |               |
        v                      v                    v               v
  Use multi-stage        Fix warnings         Tag with digest   Fix findings
  Non-root USER          No ADD, use COPY     Sign image        Remove setuid
  Minimal base           Pin versions         Push to registry  Drop caps
        |                      |                    |               |
        +----------+-----------+--------------------+               |
                   |                                                |
                   v                                                v
          [Trivy Vulnerability Scan] -----> [Docker Bench Assessment]
                   |                                    |
                   v                                    v
          Fix HIGH/CRITICAL CVEs              Remediate CIS failures
                   |                                    |
                   +------------------------------------+
                   |
                   v
          [Deploy to Production with Hardened Runtime Flags]
                   |
                   v
          [Continuous Monitoring with Falco]

Workflow 2: Existing Container Remediation

Step 1: Assess Current State
  - Run docker-bench-security against host
  - Run Trivy scan against all running images
  - Audit all running containers for root users
  - Check daemon.json configuration

Step 2: Prioritize Remediation
  - Critical: Privileged containers, root users, exposed daemon socket
  - High: Missing seccomp profiles, no resource limits, capability escalation
  - Medium: Missing health checks, no content trust, excessive open ports
  - Low: Missing labels, audit rules, log rotation

Step 3: Apply Fixes
  - Update Dockerfiles with non-root users
  - Rebuild images with multi-stage builds
  - Update docker-compose or orchestrator configs
  - Configure daemon.json with TLS and security options

Step 4: Validate
  - Re-run docker-bench-security
  - Confirm score improvement
  - Document remaining accepted risks

Workflow 3: CI/CD Integration

# GitHub Actions hardening pipeline
name: Container Hardening Pipeline
on: [push]

jobs:
  lint-dockerfile:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: hadolint/hadolint-action@v3.1.0
        with:
          dockerfile: Dockerfile

  build-and-scan:
    needs: lint-dockerfile
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - name: Build image
        run: docker build -t myapp:${{ github.sha }} .

      - name: Dockle lint
        uses: erzz/dockle-action@v1
        with:
          image: myapp:${{ github.sha }}
          failure-threshold: WARN

      - name: Trivy scan
        uses: aquasecurity/trivy-action@master
        with:
          image-ref: myapp:${{ github.sha }}
          format: table
          exit-code: 1
          severity: CRITICAL,HIGH

      - name: Sign image with Cosign
        if: github.ref == 'refs/heads/main'
        uses: sigstore/cosign-installer@v3
        run: cosign sign --yes myapp:${{ github.sha }}

Workflow 4: Runtime Hardening Checklist

Pre-deployment:
  [ ] Image built from minimal base (distroless/Alpine)
  [ ] Non-root USER specified in Dockerfile
  [ ] No secrets in image layers
  [ ] Image signed and verified
  [ ] Vulnerability scan shows no CRITICAL/HIGH CVEs
  [ ] Hadolint and Dockle pass with zero errors

Runtime configuration:
  [ ] --read-only flag enabled
  [ ] --cap-drop ALL with minimum cap-add
  [ ] --security-opt no-new-privileges:true
  [ ] --security-opt seccomp=<profile>
  [ ] --memory and --cpus limits set
  [ ] --pids-limit configured
  [ ] --user flag set to non-root UID
  [ ] --tmpfs for writable directories only
  [ ] Health check configured
  [ ] Restart policy set (on-failure with max retries)

Host configuration:
  [ ] Docker daemon TLS enabled
  [ ] Inter-container communication disabled (icc=false)
  [ ] User namespace remapping enabled
  [ ] Audit rules for Docker binaries and directories
  [ ] Docker socket not exposed to containers

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