What are some best practices for handling sensitive data in JavaScript?

TL;DR

Handling sensitive data in JavaScript requires careful attention to security practices. Avoid storing sensitive data in client-side storage like localStorage or sessionStorage. Use HTTPS to encrypt data in transit. Implement proper authentication and authorization mechanisms. Sanitize and validate all inputs to prevent injection attacks. Consider using environment variables for sensitive data in server-side code.

Best practices for handling sensitive data in JavaScript

Avoid client-side storage for sensitive data

Storing sensitive data such as tokens, passwords, or personal information in client-side storage like localStorage or sessionStorage is risky because it can be easily accessed by malicious scripts. Instead, use secure cookies with the HttpOnly and Secure flags.

// Example of setting a secure cookie in an Express.js server
res.cookie('token', token, { httpOnly: true, secure: true });

Use HTTPS

Always use HTTPS to encrypt data in transit between the client and server. This ensures that sensitive data is not exposed to eavesdroppers.

Implement proper authentication and authorization

Ensure that your application has robust authentication and authorization mechanisms. Use libraries and frameworks that are well-tested and maintained.

// Example of using JSON Web Tokens (JWT) for authentication
const jwt = require('jsonwebtoken');

const token = jwt.sign({ userId: user.id }, process.env.JWT_SECRET, {
  expiresIn: '1h',
});

Sanitize and validate inputs

Always sanitize and validate user inputs to prevent injection attacks such as SQL injection and cross-site scripting (XSS).

// Example of input validation using the express-validator library
const { body, validationResult } = require('express-validator');

app.post(
  '/submit',
  [body('email').isEmail(), body('password').isLength({ min: 5 })],
  (req, res) => {
    const errors = validationResult(req);
    if (!errors.isEmpty()) {
      return res.status(400).json({ errors: errors.array() });
    }
    // Proceed with handling the request
  },
);

Use environment variables

Store sensitive data such as API keys and database credentials in environment variables rather than hardcoding them in your source code.

// Example of accessing environment variables in Node.js
const dbPassword = process.env.DB_PASSWORD;

Regularly update dependencies

Keep your dependencies up to date to ensure that you have the latest security patches. Use tools like npm audit to identify and fix vulnerabilities.

# Example of running npm audit
npm audit fix

Further reading

• OWASP Top Ten Security Risks
• MDN Web Docs: HTTPS
• Express.js Security Best Practices
• JSON Web Tokens (JWT) Introduction
• express-validator Documentation