Bola Idor in Loopback

BOLA (Broken Object Level Authorization) and IDOR (Insecure Direct Object Reference) vulnerabilities in Loopback applications typically arise from improper access control on object identifiers passed through URLs or request bodies. In Loopback, these vulnerabilities often manifest through the framework's dynamic model resolution and relation handling.

The most common pattern occurs when Loopback's default findById or find methods are exposed without proper authorization checks. Consider a user management endpoint:

// Vulnerable Loopback controller method
async findById(@param.path.number('id') id: number) {
  return await this.userRepository.findById(id);
}

This code exposes a critical flaw: any authenticated user can access any user record by simply changing the ID parameter. The framework's default behavior doesn't automatically enforce that users can only access their own records.

Relation-based BOLA is particularly prevalent in Loopback due to its relation definitions. When a User model has relations like 'orders' or 'posts', endpoints often look like:

// Vulnerable relation endpoint
async findOrders(
  @param.path.number('id') userId: number,
  @param.filter(Order) filter?: Filter<Order>
) {
  return await this.userRepository.orders(userId).find(filter);
}

Here, an attacker can enumerate user IDs and access all orders across the system. The relation resolver in Loopback doesn't inherently check if the requesting user owns the parent resource.

Loopback's dynamic scope resolution can also introduce BOLA through filter injection. When filters are constructed from request parameters without proper validation:

// Vulnerable filter construction
async findUsers(@param.query.object('filter') filter: any) {
  return await this.userRepository.find(filter);
}

An attacker can craft filter objects that bypass authorization, such as adding a 'where' clause that always evaluates to true, or manipulating relation filters to access unauthorized data.

Detecting BOLA/IdOR in Loopback applications requires understanding the framework's specific patterns and default behaviors. The most effective approach combines static analysis of controller definitions with dynamic testing of exposed endpoints.

Static analysis should focus on identifying methods that directly expose model repositories without authorization wrappers. Look for patterns like:

// Red flag: direct repository exposure
async getUser(@param.path.number('id') id: number) {
  return await this.userRepository.findById(id);
}

Automated tools can scan Loopback applications for these patterns by examining controller files and identifying methods that accept ID parameters but lack authorization decorators or middleware.

Dynamic testing with middleBrick specifically targets Loopback's exposed endpoints. The scanner sends authenticated requests with manipulated IDs to test for BOLA vulnerabilities. For example, it will:

• Request a resource with the authenticated user's ID, then with incrementally modified IDs
• Check if relation endpoints return data for arbitrary parent IDs
• Test filter parameter injection by sending crafted filter objects
• Verify that role-based access controls are properly enforced
• Check for ID enumeration through timing analysis and error messages

middleBrick's Loopback-specific detection includes recognizing the framework's default route patterns and testing against them. It understands that a Loopback application with a User model will likely expose /users/{id} endpoints and relation endpoints like /users/{id}/orders.

The scanner also tests for Loopback's specific authentication integration patterns. Many Loopback applications use JWT tokens or session-based auth, and middleBrick verifies that authorization checks are properly scoped to the authenticated user's context, not just checking for authentication presence.

Remediating BOLA/IdOR vulnerabilities in Loopback requires leveraging the framework's built-in authorization features and implementing proper access control patterns. The most effective approach uses Loopback's Access Control List (ACL) system and operation hooks.

First, implement ACLs to restrict model operations:

// ACL definitions in JSON
{
  "accessType": "READ",
  "principalType": "ROLE",
  "principalId": "$authenticated",
  "permission": "ALLOW",
  "property": "findById"
}

However, ACLs alone are insufficient for BOLA prevention because they don't scope operations to the current user's owned resources. You need to combine ACLs with operation hooks:

// Operation hook for BOLA prevention
this.userRepository.observe('access', async (context) => {
  const userId = context.options.accessToken?.userId;
  
  if (context.accessType === 'READ' && context.query.where?.id) {
    // Only allow access to own record or if user has admin role
    if (!context.options.isAdmin && context.query.where.id !== userId) {
      throw new HttpErrors.Forbidden('Access denied to requested resource');
    }
  }
});

For relation endpoints, implement scoped access control:

async findOrders(
  @param.path.number('id') userId: number,
  @param.filter(Order) filter?: Filter<Order>
) {
  const currentUserId = this.getCurrentUserId();
  
  // Only allow access to own orders or if user has admin role
  if (userId !== currentUserId && !this.isAdmin()) {
    throw new HttpErrors.Forbidden('Access denied to requested resource');
  }
  
  return await this.userRepository.orders(userId).find(filter);
}

Loopback's built-in 'owner' scope provides another layer of protection:

// Use owner scope to automatically filter by current user
async findMyOrders() {
  return await this.orderRepository.find({
    where: { userId: this.getCurrentUserId() }
  });
}

For applications using Loopback's authentication system, ensure that all repository operations include the current user context:

async findById(@param.path.number('id') id: number) {
  const userId = this.getCurrentUserId();
  const isAdmin = await this.userRepository.findById(userId, {
    fields: { role: true }
  });
  
  if (!isAdmin && id !== userId) {
    throw new HttpErrors.Forbidden('Access denied to requested resource');
  }
  
  return await this.userRepository.findById(id);
}

Finally, implement comprehensive testing for BOLA vulnerabilities using middleBrick's continuous monitoring. The Pro plan's scheduled scanning will automatically detect if new BOLA vulnerabilities are introduced during development, providing immediate feedback when security regressions occur.