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Using Docker Bench for Security to Audit Your Docker Setup

Docker security has become an essential consideration for organizations using containerization. Docker, by default, provides isolation between applications, but it’s still crucial to follow security best practices to harden your Docker setup.

Using Docker Bench for Security to Audit Your Docker Setup

Introduction

As the adoption of Docker continues to grow, security has become an essential consideration for organizations using containerization. Docker, by default, provides isolation between applications, but it’s still crucial to follow security best practices to harden your Docker setup. One valuable tool in this security toolkit is Docker Bench for Security.

Docker Bench for Security is an open-source script that checks for dozens of common security best practices around Docker deployments. It automates the process of auditing your Docker environment based on the Center for Internet Security (CIS) Docker Benchmark, ensuring that your Docker setup adheres to industry standards.

In this post, we’ll provide an overview of Docker Bench for Security, explain how to use it, review some of the best practices it checks for, and discuss how to integrate it into your CI/CD pipeline to automate security audits.

1. What Is Docker Bench for Security?

Docker Bench for Security is a security auditing tool developed by Docker Inc. and the open-source community. It automates the evaluation of Docker environments against the CIS Docker Benchmark, a set of security best practices and recommendations for Docker deployments.

The tool checks the security configuration of Docker hosts, Docker daemon, containers, images, and networks. It runs a series of automated checks to identify potential misconfigurations or insecure settings that could make your Docker setup vulnerable to attacks.

Key features of Docker Bench for Security:

  • Automated Checks: Docker Bench for Security evaluates your environment without manual intervention, saving you time and ensuring thorough coverage.
  • Based on CIS Docker Benchmark: The checks are based on industry-standard guidelines for securing Docker.
  • Open-source: Docker Bench is an open-source project, making it accessible and customizable to fit your environment’s needs.

2. Why Is Security Auditing Important in Docker?

While Docker containers provide process isolation and are built to run applications securely, security risks still exist if configurations are not correctly set up. Misconfigured containers, improper Docker daemon settings, and outdated software packages can all contribute to security vulnerabilities.

Here are several reasons why security auditing is critical in Docker environments:

  • Protecting the Host System: Containers share the host kernel, meaning any compromise within a container can potentially escalate and affect the host system. Auditing helps mitigate this risk by ensuring the Docker host is properly configured.
  • Securing Containers: Improperly configured containers may run with too many privileges or expose sensitive data. Security audits ensure that containers are appropriately isolated and secure.
  • Compliance: Many organizations need to comply with regulatory requirements or industry standards, such as GDPR, HIPAA, or PCI-DSS. Docker Bench helps ensure your containerized environment meets these security requirements.
  • Minimizing Attack Surface: Regular audits identify weaknesses and misconfigurations in your Docker setup, allowing you to fix them before attackers can exploit them.

3. Key Docker Security Best Practices Audited by Docker Bench

Docker Bench for Security checks various aspects of Docker security, from host configuration to container runtime settings. Let’s take a look at some of the key areas it audits:

a. Host Configuration

The Docker host is the foundation of your containerized environment. A compromised host can jeopardize the security of all the containers running on it. Docker Bench checks for the following host security best practices:

  • Operating System Updates: Ensure that the host OS is running the latest security patches and updates.
  • User Authentication and Authorization: Ensure that user access to the Docker host is properly configured (e.g., SSH access, user groups).
  • Kernel Parameters: Check that kernel parameters are properly configured for security, such as disabling IP forwarding and limiting core dumps.
  • Firewall Configuration: Ensure that firewalls are in place to limit network exposure of the Docker daemon.

b. Docker Daemon Configuration

The Docker daemon is responsible for managing containers and images. Misconfigurations here can expose your containers to security risks. Docker Bench checks the following best practices for the Docker daemon:

  • Running the Docker Daemon as a Non-Root User: Ensures that the Docker daemon is running with the least privileges necessary.
  • Daemon Configuration File: Verifies that the daemon configuration file (/etc/docker/daemon.json) is properly set up with secure options, such as disabling remote access.
  • Daemon Security Flags: Checks if flags like --icc=false (disables inter-container communication) and --no-new-privileges are enabled.

c. Container Runtime

Docker Bench also audits how containers are run and configured. Running containers with excessive privileges or insecure settings can increase the risk of exploitation. Some container runtime checks include:

  • Running Containers as Non-Root Users: Ensure that containers are not running as the root user, which could lead to privilege escalation.
  • Container Capabilities: Verifies that containers are not granted unnecessary Linux capabilities, such as SYS_ADMIN or NET_ADMIN.
  • Read-Only Filesystems: Checks whether containers have their root filesystem set to read-only to prevent unwanted modifications.
  • Resource Limits: Ensures that containers have appropriate CPU and memory resource limits to prevent resource exhaustion.

d. Docker Security Policies

Docker Bench also evaluates the use of Docker security policies, such as AppArmor and SELinux, to provide additional isolation for containers. These policies are crucial in limiting the actions that containers can perform on the host system.

  • AppArmor Profiles: Verifies that AppArmor profiles are applied to containers to enforce mandatory access control (MAC) policies.
  • SELinux Policies: Checks whether SELinux is enabled and correctly configured for Docker containers.

4. How to Install and Run Docker Bench for Security

Docker Bench for Security is straightforward to install and run. Here’s a step-by-step guide to getting started:

Step 1: Download Docker Bench for Security

You can download Docker Bench directly from the official GitHub repository. Run the following command to clone the repository:

git clone https://github.com/docker/docker-bench-security.git

Alternatively, you can run Docker Bench as a Docker container itself:

docker run -it --net host --pid host --cap-add audit_control \
    -v /var/lib:/var/lib -v /var/run/docker.sock:/var/run/docker.sock \
    -v /usr/lib/systemd:/usr/lib/systemd -v /etc:/etc \
    --label docker_bench_security docker/docker-bench-security

Step 2: Run the Audit

Once you’ve downloaded Docker Bench or set up the Docker container, navigate to the directory where you cloned the repository and run the script:

cd docker-bench-security
sudo sh docker-bench-security.sh

Step 3: Review the Output

Docker Bench will run several security checks and output the results directly in the terminal. You’ll see a list of checks, categorized as INFO, WARN, or PASS. Each check includes a description of what was audited and the result.

5. Understanding the Docker Bench for Security Report

Docker Bench’s output provides a detailed report on the state of your Docker environment’s security. Here’s how to interpret the results:

  • PASS: This indicates that the check passed, and the audited configuration meets best practices.
  • WARN: This indicates that the check failed, meaning the configuration is not compliant with best practices. You should investigate these warnings and fix them accordingly.
  • INFO: This indicates a general information message. No action is required, but you may want to review the information for further insight.

For each failed check, Docker Bench provides a reference to the CIS Docker Benchmark, giving you context on why the check is important and how to remediate it.

Example output:

[INFO] 1 - Host Configuration
[PASS] 1.1 - Ensure a separate partition for containers has been created
[WARN] 1.2 - Ensure that the Docker server is running with the latest OS updates
[PASS] 1.3 - Ensure that the filesystem is mounted read-only

6. Automating Docker Bench Audits in CI/CD Pipelines

For continuous security assurance, it’s important to integrate Docker Bench for Security into your CI/CD pipeline. This ensures that every time you make changes to your Docker setup, your environment remains secure.

Here’s an example of how you can integrate Docker Bench into a Jenkins pipeline:

pipeline {
    agent any

    stages {
        stage('Build Docker Image') {
            steps {
                script {
                    docker.build('my-app:latest')
                }
            }
        }

        stage('Security Audit') {
            steps {
                script {
                    sh 'docker run --rm -v /var/run/docker.sock:/var/run/docker.sock docker/docker-bench-security'
                }
            }
        }
    }
}

In this pipeline, Jenkins runs the Docker Bench security audit after building the Docker image. You can configure the pipeline to fail if any high-priority warnings are found.

7. Best Practices to Follow Based on Docker Bench Results

After running Docker Bench for Security, you should take action to fix any WARN items in the report. Here are some common best practices you can follow:

  • Regular Audits: Make Docker Bench part of your regular security audits, especially after updating Docker, the host OS, or any container-related services.
  • Use Non-Root Users: Always ensure that both Docker daemons and containers are running as non-root users.
  • Minimize Privileges: Limit container capabilities and disable unnecessary features, such as inter-container communication and container networking, unless needed.
  • Enforce Security Policies: Use security policies like AppArmor or SELinux to apply mandatory access control and isolate containers.
  • Harden the Host: Regularly update the Docker host, configure firewall rules, and harden kernel parameters.

Conclusion

Docker Bench for Security is an essential tool for auditing and improving the security of your Docker environment. By running automated checks based on the CIS Docker Benchmark, you can ensure that your Docker hosts, containers, and configurations meet industry standards.

Security is a critical aspect of any containerized environment, and Docker Bench helps you stay ahead of potential threats by identifying misconfigurations and vulnerabilities before they can be exploited.

By integrating Docker Bench into your CI/CD pipelines and making it a regular part of your security process, you can ensure that your Docker environment remains secure, compliant, and ready to handle production workloads.

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