Secure Your Docker Images with Trivy: A Step-by-Step Guide

Containers are at the heart of modern DevOps workflows, but they’re not immune to vulnerabilities. That’s where Trivy comes in! Trivy is a powerful, open-source vulnerability scanner that makes securing your container images straightforward and effective. In this post, we’ll explore how to use Trivy to scan Docker images and ensure your applications are secure.

Why Trivy?

Trivy is a versatile and easy-to-use tool that helps you:

• Detect vulnerabilities in container images and application dependencies.
• Identify misconfigurations in Dockerfiles and Kubernetes manifests.
• Ensure compliance with security standards, such as CIS Benchmarks.

Key Benefits:

1. Fast and Comprehensive Scanning: Supports both OS and application libraries.
2. Wide Ecosystem Support: Works with Docker, Kubernetes, CI/CD pipelines, and more.
3. Open Source: Free to use and continuously updated by Aqua Security.

Getting Started with Trivy

Step 1: Install Trivy

Linux Installation

sudo apt-get install wget apt-transport-https gnupg lsb-release -y
wget -qO - https://aquasecurity.github.io/trivy-repo/deb/public.key | sudo apt-key add -
echo deb https://aquasecurity.github.io/trivy-repo/deb $(lsb_release -sc) main | sudo tee -a /etc/apt/sources.list.d/trivy.list
sudo apt-get update
sudo apt-get install trivy

MacOS Installation

brew install aquasecurity/trivy/trivy

Windows Installation

Use PowerShell with Chocolatey:

choco install trivy

Verify the installation:

trivy --version

Step 2: Scanning a Docker Image

Basic Command

To scan a Docker image for vulnerabilities, use:

trivy image <image_name>:<tag>

Example:

Scan the official NGINX image:

trivy image nginx:latest

Sample Output:

nginx:latest (debian 11.7)

Total: 5 (CRITICAL: 1, HIGH: 2, MEDIUM: 1, LOW: 1)

+------------+------------------+----------+--------------------------------+--------------------------------+---------------------------------------+
|  Library   | Vulnerability ID | Severity |         Installed Version      |           Fixed Version       |                 Title                 |
+------------+------------------+----------+--------------------------------+--------------------------------+---------------------------------------+
| libzstd1   | CVE-2023-34251   | HIGH     | 1.4.8+dfsg-3                  | 1.4.8+dfsg-3+deb11u2          | zstd: Double free                    |
+------------+------------------+----------+--------------------------------+--------------------------------+---------------------------------------+

Step 3: Advanced Scanning Options

1. Skip Pulling the Image

If the image is already present locally:

trivy image --skip-update nginx:latest

2. Filter by Severity

Focus on critical and high-severity issues:

trivy image --severity CRITICAL,HIGH nginx:latest

3. Output Results as JSON

Save the scan report for further analysis:

trivy image --format json --output results.json nginx:latest

4. Ignore Unfixable Issues

Exclude vulnerabilities without fixes:

trivy image --ignore-unfixed nginx:latest

5. Scan Specific Vulnerability Types

Target OS vulnerabilities, application libraries, or both:

trivy image --vuln-type os,library nginx:latest

Step 4: Automate Scanning in CI/CD Pipelines

Example: Azure Devops

Use Trivy in your Azure Devops workflow to enforce security checks:

name: Trivy Scan

on:
  push:
    branches:
      - main

jobs:
  scan:
    runs-on: Agentpool  #your agent pool or any which you want
    steps:
      - name: Checkout Code
        uses: actions/checkout@v3
      - name: Run Trivy Scan
        uses: aquasecurity/trivy-action@v0.9.1
        with:
          image-ref: 'nginx:latest'

Example: AzureDeops Pipeline

pipeline {
    agent any
    stages {
        stage('Vulnerability Scan') {
            steps {
                sh 'trivy image nginx:latest'
            }
        }
    }
}

Step 5: Best Practices

1.Update the Vulnerability Database Keep the database current
to ensure the latest vulnerabilities are detected:

trivy image --update nginx:latest

2.Focus on Fixing Critical Issues Prioritize addressing
CRITICAL and HIGH vulnerabilities first to minimize risk.

3.Integrate Scanning Early Shift security left by integrating
Trivy scans into your CI/CD pipelines.

Final Thoughts

Trivy makes vulnerability scanning easy, fast, and effective. Whether you're working with container images, IaC, or application dependencies, it’s a must-have tool for your DevSecOps toolkit.

Want to explore more about Trivy? Check out the official documentation. Start scanning today and keep your applications secure!