Secure Authentication: JWT, Refresh Tokens, and OAuth 2.0

Authentication is where many applications fail security audits. Here's how I implement secure authentication that protects users without creating friction.

JWT Best Practices

JSON Web Tokens are powerful but easy to misuse. Follow these practices:

• **Short Expiration**: Access tokens expire in 15 minutes
• **Refresh Tokens**: Longer-lived tokens stored securely
• **HttpOnly Cookies**: Prevent XSS token theft
• **Strong Secrets**: Use cryptographically secure random strings

Token Rotation

Implement refresh token rotation to limit the impact of token theft. Each refresh generates a new refresh token and invalidates the old one.

OAuth 2.0 Integration

For social login, OAuth 2.0 is the standard. The authorization code flow is most secure:

1. Redirect user to provider (Google, GitHub)
2. User authenticates and grants permissions
3. Provider redirects back with authorization code
4. Exchange code for tokens server-side

Never expose client secrets to the browser.

Protecting Against Common Attacks

• **CSRF**: Use SameSite cookies and CSRF tokens
• **XSS**: Sanitize inputs, use Content Security Policy
• **Brute Force**: Rate limiting and account lockout
• **Session Fixation**: Regenerate session on login

Password Security

If using passwords:

• Hash with bcrypt or Argon2 (never MD5 or SHA1)
• Enforce minimum complexity
• Check against breach databases
• Implement password reset securely

Multi-Factor Authentication

Add MFA for sensitive applications. TOTP (Time-based One-Time Password) is widely supported. Libraries like speakeasy make implementation straightforward.

Security is a process, not a feature. Regular security audits and staying updated on vulnerabilities is essential.