Preventing Broken Access Control in RESTful APIs

Broken Access Control (BAC) is a severe security flaw in RESTful APIs that compromises sensitive data and allows unauthorized actions. This blog covers real-world examples, practical coding implementations, and strategies to prevent BAC and safeguard your API endpoints.

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What is Broken Access Control in RESTful APIs?

BAC occurs when an API fails to enforce restrictions on users, leading to unauthorized data access or actions. It’s ranked as a critical vulnerability in the OWASP API Security Top 10.

Real-Life Example:

In 2021, an e-commerce platform’s API allowed users to escalate their privileges by tampering with the user_role field in API requests. This flaw let regular users perform admin operations, exposing sensitive customer data and orders.

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Common Causes of Broken Access Control

1. Direct Object References (IDOR): Exposing resource identifiers in URLs, e.g., /api/user/12345, without validating ownership.
2. Improper Validation: Missing server-side checks for user roles or privileges.
3. Hardcoded Role Assignments: Failing to implement dynamic RBAC systems.

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Detecting Broken Access Control in RESTful APIs

You can identify BAC vulnerabilities using automated tools like our free website security checker.

Example Scenario:
Imagine an API endpoint /api/orders that allows users to fetch their orders. If BAC is poorly implemented, a user could access others’ orders by tampering with the order_id in the API request.

GET /api/orders?order_id=1002  
Authorization: Bearer <user-token>  

If no ownership validation is done, attackers could alter the order_id to 1003 and access someone else’s data.

Here’s a snapshot of the report generated by our tool identifying BAC issues:

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Coding Examples

1. Preventing IDOR

// Middleware to validate resource ownership  
function validateOwnership(req, res, next) {  
  const userId = req.user.id;  
  const requestedResourceOwnerId = req.params.ownerId;  

  if (userId !== requestedResourceOwnerId) {  
    return res.status(403).send('Access Denied');  
  }  
  next();  
}  

// API route  
app.get('/api/orders/:ownerId', validateOwnership, (req, res) => {  
  res.send('Order details fetched securely.');  
});  

2. Enforcing Role-Based Access Control (RBAC)

const rolesPermissions = {  
  admin: ['view_users', 'delete_users'],  
  user: ['view_profile'],  
};  

function authorize(action) {  
  return (req, res, next) => {  
    const role = req.user.role;  
    if (!rolesPermissions[role] || !rolesPermissions[role].includes(action)) {  
      return res.status(403).send('Forbidden');  
    }  
    next();  
  };  
}  

app.delete('/api/user/:id', authorize('delete_users'), (req, res) => {  
  res.send('User deleted successfully.');  
});  

3. Secure JWT Validation

const jwt = require('jsonwebtoken');  

function verifyToken(req, res, next) {  
  const token = req.headers.authorization.split(' ')[1];  
  if (!token) return res.status(401).send('Unauthorized');  

  jwt.verify(token, process.env.JWT_SECRET, (err, user) => {  
    if (err) return res.status(403).send('Token is invalid');  
    req.user = user;  
    next();  
  });  
}  

app.use(verifyToken);  

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Best Practices

1. Strict Role and Permission Management: Use dynamic RBAC models.
2. Server-Side Validation: Avoid relying solely on client-side checks.
3. Audit Logs: Track API access to detect misuse.
4. Minimize Exposure: Avoid exposing sensitive resource identifiers in URLs.

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Linking Resources

For more strategies on strengthening RESTful APIs, check out our previous blog on avoiding security misconfigurations in RESTful APIs. You can also explore other related topics on our blog page.

Laravel developers can read our guide on fixing broken access control in Laravel.

Conclusion

Broken Access Control is one of the most exploited API vulnerabilities, but it’s preventable with proper coding practices, regular vulnerability scans, and security-first design principles. Use our tools to test website security free to detect and fix these issues.

Take action today and secure your APIs against unauthorized access!

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