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Is This npm Package Safe? A 4-Step Checklist For Secure Code

technpmsecurity

You've landed your first software engineering role. You're working on features, closing tickets, and trying to absorb a boatload of new information. Then, you're faced with a critical task: choosing a safe npm package for a new feature. A quick search reveals dozens of options. Which one do you trust? And how do you know it won't introduce a critical vulnerability into your company's codebase?

This was a real interview question I fumbled. Now, it's a critical part of my workflow. Here's a no-nonsense guide to determining if an npm package is safe to use.

Step 1: The Built-in Health Check (npm audit)

Before you even think about adding a new package, get familiar with npm's built-in security tool. The npm audit command scans your project's dependencies for known vulnerabilities and gives you a report.

To see it in action, simply run:

npm audit

If vulnerabilities are found, npm will provide a summary of their severity (low, moderate, high, critical). For many of these, a simple fix is available:

npm audit fix

This command will attempt to upgrade the vulnerable packages to a safe version without breaking changes. It's a good first line of defense and should be a regular part of your development hygiene.

Step 2: Vital Signs on npm and GitHub

Before you npm install, do some quick reconnaissance. Think of it as a background check on the package.

On the npm Registry Page:

  • Downloads: A high number of weekly downloads is a good sign. It indicates that many other developers trust and use the package. Be wary of packages with very few downloads.

  • Last Publish: When was the last version published? A package that hasn't been updated in years is likely unmaintained and could have unpatched vulnerabilities.

  • Dependencies: Check the number of dependencies the package has. More dependencies mean a larger attack surface. You can use tools like npm ls <package-name> to inspect the dependency tree.

On the GitHub Repository:

  • Stars: While not a direct measure of security, a high number of stars indicates popularity and a larger community.

  • Contribution Activity: Look at the commit history. Is the package actively being developed? Are there recent commits from multiple contributors?

  • Maintainer Engagement: Are the maintainers actively responding to issues and merging pull requests? A healthy project has engaged maintainers.

Step 3: Digging Deeper with External Tools

For a more in-depth analysis, you can use third-party tools that provide detailed security insights.

  • Snyk Advisor: This is a fantastic free tool. Simply search for a package on the Snyk Advisor website, and it will give you a comprehensive health score. It provides information on security vulnerabilities, maintenance status, community activity, and more.

Step 4: When in Doubt, Read the Code

If a package is small and you're still unsure, take a look at the source code. You don't need to understand every line, but you can look for red flags:

  • Obfuscated Code: If the code is intentionally made difficult to read, that's a major red flag.

  • Network Requests: Does the code make unexpected network requests? Be cautious of packages that send data to unknown servers.

  • File System Access: Does the package read from or write to the file system in a way that seems unnecessary for its stated purpose?

Security is a Process, Not a One-Time Check

It's crucial to remember that security is an ongoing process, not a one-time check. A package that is safe today could have a vulnerability discovered tomorrow. Here's how to stay on top of it:

  • Lock Your Dependencies: Always use a lock file (package-lock.json for npm). This ensures that you and your teammates are using the exact same versions of all dependencies, preventing unexpected updates that could introduce vulnerabilities.

  • Schedule Periodic Updates: Set aside time regularly to update your dependencies. This helps you stay on top of security patches and new features. Tools like npm outdated can help you identify packages that need updating.

  • Automate Scanning in Your CI/CD Pipeline: Integrate security scanning into your continuous integration and continuous delivery (CI/CD) pipeline. This means that every time you push code, your dependencies will be automatically scanned for vulnerabilities. This is a critical step in catching issues before they make it to production.

Example Walkthrough: Checking the express Package

Let's put this into practice and check the popular express package.

  1. npm Registry: A quick look at the express page on npmjs.com shows millions of weekly downloads and a recent publish date. These are both good signs.

  2. GitHub: The express repository on GitHub has a high number of stars and a long history of contributions from many developers. This indicates a mature and well-maintained project.

  3. Snyk Advisor: A search on the Snyk Advisor gives express a high health score. It shows no major security vulnerabilities and highlights the package's popularity and active maintenance.

  4. npm audit: In a project with express installed, running npm audit shows no vulnerabilities.

Based on this walkthrough, we can be confident that express is a safe and reliable package to use.

By following these steps, you can significantly reduce the risk of introducing a malicious or vulnerable package into your project. It might seem like a bit of extra work upfront, but it's far better than dealing with a security breach down the line.

sam