How to Scan Docker Images for Vulnerabilities

Scanning Docker images for vulnerabilities is an essential practice to ensure the security of your applications. Vulnerabilities in images can lead to security breaches, data leaks, and other serious issues. This guide will explain how to scan Docker images for vulnerabilities using various tools, along with sample code for practical implementation.

1. Why Scan Docker Images?

Docker images can contain outdated libraries, misconfigurations, or known vulnerabilities that can be exploited by attackers. Regularly scanning images helps identify and remediate these vulnerabilities before deploying applications in production.

2. Tools for Scanning Docker Images

• Trivy: A simple and comprehensive vulnerability scanner for containers and other artifacts.
• Clair: An open-source project for the static analysis of vulnerabilities in application containers.
• Anchore Engine: A tool for analyzing container images and enforcing policies.

3. Using Trivy to Scan Docker Images

Trivy is a popular and easy-to-use vulnerability scanner for Docker images. Below are the steps to install and use Trivy.

Step 1: Install Trivy

You can install Trivy using the following command:

brew install aquasecurity/trivy/trivy

For other installation methods, refer to the Trivy installation guide.

Step 2: Scan a Docker Image

To scan a Docker image, use the following command:

trivy image <image-name>
</image-name>

For example, to scan the official Nginx image:

trivy image nginx:latest

Step 3: Interpreting the Results

Trivy will output a list of vulnerabilities found in the image, along with their severity levels (e.g., LOW, MEDIUM, HIGH, CRITICAL). Review the results to identify any vulnerabilities that need to be addressed.

4. Using Clair to Scan Docker Images

Clair is another powerful tool for scanning Docker images. It requires a bit more setup compared to Trivy.

Step 1: Set Up Clair

To set up Clair, you can use Docker Compose. Create a docker-compose.yml file with the following content:

version: '3'
services:
  clair:
    image: quay.io/coreos/clair:latest
    ports:
      - "6060:6060"
      - "6061:6061"
    environment:
      - POSTGRES_HOST=postgres
      - POSTGRES_PORT=5432
      - POSTGRES_USER=clair
      - POSTGRES_PASSWORD=clair
      - POSTGRES_DB=clair
  postgres:
    image: postgres:latest
    environment:
      - POSTGRES_USER=clair
      - POSTGRES_PASSWORD=clair
      - POSTGRES_DB=clair

Step 2: Start Clair

Run the following command to start Clair and PostgreSQL:

docker-compose up -d

Step 3: Scan an Image with Clair

To scan an image with Clair, you need to push the image to a registry that Clair can access. After that, you can use the Clair API to analyze the image.

5. Using Anchore Engine to Scan Docker Images

Anchore Engine is another tool for scanning Docker images. It provides a web interface and API for managing image analysis.

Step 1: Set Up Anchore Engine

You can set up Anchore Engine using Docker Compose. Create a docker-compose.yml file with the following content:

version: '3'
services:
  anchore-postgresql:
    image: anchore/anchore-postgresql:latest
  anchore-engine:
    image: anchore/anchore-engine:latest
    depends_on:
      - anchore-postgresql

Step 2: Start Anchore Engine

Run the following command to start Anch ore Engine:

docker-compose up -d

Step 3: Scan an Image with Anchore Engine

To scan an image with Anchore Engine, you can use the following command:

anchore-cli image add <image-name>
anchore-cli image wait <image-name>
anchore-cli image get <image-name>
</image-name></image-name></image-name>

For example, to scan the official Nginx image:

anchore-cli image add nginx:latest
anchore-cli image wait nginx:latest
anchore-cli image get nginx:latest

Conclusion

Regularly scanning Docker images for vulnerabilities is essential for maintaining the security of your applications. Tools like Trivy, Clair, and Anchore Engine provide effective ways to identify and remediate vulnerabilities in your Docker images, ensuring a secure deployment environment.