Need

Secure access to financial information

Context

• Usage of TypeScript for type-checking and adding static typing to JavaScript
• Usage of Express for building web applications and APIs

Description

Non compliant code

        import express from 'express';

const app = express();

app.get('/credit-card/:cardNumber/expenses', (req, res) => {
  const cardNumber = req.params.cardNumber;
  const sessionUserId = req.session.userId; // Assuming session is already implemented

  // Check if the user has permission to access the credit card expenses
  if (sessionUserId !== cardNumber) {
    return res.status(403).json({ error: 'Unauthorized access' });
  }

  // Query and return the credit card expenses
  // ...
});

app.listen(3000, () => {
  console.log('Server is running on port 3000');
});
        
        

The vulnerability in this code is an insecure object reference.

In the app.get route handler, the code retrieves the cardNumber from the request parameters and the sessionUserId from the session. It then compares the sessionUserId with the cardNumber to check if the user has permission to access the credit card expenses.

However, the vulnerability lies in the comparison if (sessionUserId !== cardNumber). This comparison assumes that the cardNumber is a valid and secure identifier for the user. But in reality, the cardNumber is an input provided by the user, which can be manipulated.

An attacker can exploit this vulnerability by intercepting the request and modifying the cardNumber parameter to a different valid card number associated with another user. Since the comparison only checks for inequality, the attacker can bypass the permission check and gain access to the expenses of another user.

To fix this vulnerability, the code should not rely solely on the cardNumber for authorization. Instead, it should validate the user's access rights based on their session or user ID, and ensure that the user has the necessary permissions to access the requested credit card expenses.

Steps

• Implement a proper authentication and authorization system to ensure that only authorized users can access the credit card expenses.
• When querying the credit card expenses, validate that the user making the request has the necessary permissions to access the information.
• Consider using a different identifier for the credit card, such as a unique card ID, instead of the card number to avoid exposing sensitive information in the URL.
• Encrypt the credit card expenses data to add an extra layer of security.
• Regularly review and update the authentication and authorization system to address any potential vulnerabilities.

Compliant code

        import express from 'express';

const app = express();

// Implement authentication and authorization middleware
app.use((req, res, next) => {
  // Your authentication and authorization logic here
  // Verify user's session and permissions
  // Set req.user with authenticated user information
  // If user is not authorized, return appropriate response
  next();
});

app.get('/credit-card/:cardId/expenses', (req, res) => {
  const cardId = req.params.cardId;
  const userId = req.user.id;

  // Query and return the credit card expenses
  // Validate that the user has necessary permissions to access the information
  // ...

  res.status(200).json({ expenses: [] });
});

app.listen(3000, () => {
  console.log('Server is running on port 3000');
});
        
        

The fixed code addresses the vulnerability by implementing authentication and authorization middleware. Here's an explanation of the code:

1. The code imports the 'express' module and creates an instance of the Express application. 2. The middleware function is added using the app.use method. This middleware function is responsible for authenticating and authorizing the user. 3. Inside the middleware function, you would typically implement your authentication and authorization logic. This may involve verifying the user's session, checking their permissions, and setting req.user with the authenticated user information. 4. If the user is not authorized, an appropriate response should be returned, which could be an error message or a redirect to a login page. 5. The app.get method is used to define a route for accessing credit card expenses. The route path includes a parameter :cardId to specify the card ID. 6. Inside the route handler function, req.params.cardId is used to retrieve the card ID from the request parameters. 7. req.user.id is used to retrieve the authenticated user's ID from the req.user object. 8. The code should then query and return the credit card expenses, ensuring that the user has the necessary permissions to access the information. 9. Finally, a JSON response with an empty array of expenses is sent back to the client with a status code of 200.

By implementing authentication and authorization middleware and validating the user's permissions, the fixed code ensures that only authorized users can access the credit card expenses, mitigating the insecure object reference vulnerability.

References

• 288. Insecure object reference - Financial information