Access Control

Access Control Overview

Access Control lets you structure authentication work so it stays readable, testable, and easy to scale. Instead of ad-hoc code, you follow a clear pattern that other developers can recognise immediately.

The key is to keep access control focused and predictable. Start from the minimal example here, then layer in only the complexity your feature actually needs.

function requireRole(role) {
  return (req, res, next) => {
    if (req.user?.role !== role) {
      return res.status(403).json({ error: 'Forbidden' });
    }
    next();
  };
}

app.delete('/users/:id', requireRole('admin'), deleteUser);

Authorization middleware checks the authenticated user's role before allowing an action.

Access Control Example

// verify the caller on every protected request
function authenticate(req, res, next) {
  const token = req.headers.authorization?.replace('Bearer ', '');
  req.user = verifyToken(token); // throws if invalid
  next();
}

• Start from a minimal Access Control example and grow it only as needed.
• Keep configuration explicit so Access Control behaves the same in every environment.
• Name things clearly so teammates understand your Access Control at a glance.
• Add tests around Access Control early to lock in expected behaviour.

Authentication Cheatsheet

Quick authentication reference related to access control.

How Access Control Works

Access Control is part of proving who a user is and what they are allowed to do. Authentication verifies identity, while authorization decides access — and access control plays a specific role in that flow.

Authorization middleware checks the authenticated user's role before allowing an action.

• Never store or log plain-text passwords or secrets.
• Prefer short-lived tokens with refresh over long-lived ones.
• Always send credentials over HTTPS.
• Fail closed: deny access when anything is uncertain.

Security Guidance for Access Control

Security is the whole point of access control. Small mistakes — weak hashing, tokens in localStorage, missing rate limits — are exactly what attackers look for, so follow proven defaults.

Common Mistakes

• Copying access control snippets without understanding what each line does.
• Skipping error handling and edge cases when wiring up access control.
• Leaving access control untested, so regressions slip into production.
• Over-engineering access control before you actually need the extra flexibility.

Key Takeaways

• Access Control is a core part of working effectively with authentication.
• Start small and keep access control focused on a single responsibility.
• Apply consistent patterns so access control scales across your project.
• Test and document access control to keep it maintainable over time.