Data uniqueness not properly verified

Need

Ensure proper validation of data uniqueness

Context

• Usage of TypeScript for type-checking and compiling JavaScript code
• Usage of Express for building web applications and APIs

Description

Non compliant code

import express from 'express';

const app = express();

// Vulnerable route that does not properly verify data uniqueness
app.post('/register', (req, res) => {
  const { username } = req.body;

  // Check if the username already exists in the database
  const userExists = checkIfUserExists(username);

  if (userExists) {
    // Allow the attacker to reuse or regenerate the username
    console.log('Username already exists');
    res.status(400).json({ error: 'Username already exists' });
  } else {
    // Proceed with user registration
    registerUser(username);
    res.status(200).json({ message: 'User registered successfully' });
  }
});

function checkIfUserExists(username: string): boolean {
  // Implementation to check if the username already exists in the database
  // This implementation is intentionally omitted for the sake of example
  return false;
}

function registerUser(username: string): void {
  // Implementation to register the user in the database
  // This implementation is intentionally omitted for the sake of example
}

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

The vulnerability in this code lies in the /register route. The route is responsible for handling user registration requests. However, it does not properly verify the uniqueness of the username provided by the user.

The code first checks if the username already exists in the database by calling the checkIfUserExists function. However, in this example, the function always returns false, indicating that the username does not exist. This is a simplified implementation for the sake of example, but in a real application, this function would typically query the database to check for the existence of the username.

If the checkIfUserExists function returns true, indicating that the username already exists, the code logs a message and returns a 400 Bad Request response to the client. However, this allows an attacker to reuse or regenerate the username, as there is no proper validation to prevent it.

On the other hand, if the checkIfUserExists function returns false, indicating that the username does not exist, the code proceeds with the user registration by calling the registerUser function. This assumes that the username is unique and can be safely registered.

The impact of this vulnerability is that an attacker can exploit the misconfigured feature by repeatedly sending registration requests with the same username, bypassing the uniqueness check. This can lead to various vulnerabilities, such as account takeover, data corruption, or denial of service.

To mitigate this vulnerability, proper validations should be implemented to ensure that the data, in this case, the username, cannot be reused or regenerated if the application requires a unique value.

Steps

• Implement a proper validation to check if the username already exists in the database
• If the username exists, return an error response indicating that the username is already taken
• If the username does not exist, proceed with user registration
• Update the checkIfUserExists function to query the database and check if the username exists
• Update the registerUser function to insert the user into the database

Compliant code

import express from 'express';

const app = express();

// Vulnerable route that does not properly verify data uniqueness
app.post('/register', (req, res) => {
  const { username } = req.body;

  // Check if the username already exists in the database
  const userExists = checkIfUserExists(username);

  if (userExists) {
    // Username already exists, return an error response
    console.log('Username already exists');
    res.status(400).json({ error: 'Username already exists' });
  } else {
    // Proceed with user registration
    registerUser(username);
    res.status(200).json({ message: 'User registered successfully' });
  }
});

function checkIfUserExists(username: string): boolean {
  // Implementation to check if the username already exists in the database
  // Replace this with your actual implementation to query the database
  // and check if the username exists
  const userExists = /* Your database query logic here */;
  return userExists;
}

function registerUser(username: string): void {
  // Implementation to register the user in the database
  // Replace this with your actual implementation to insert the user into the database
  /* Your database insertion logic here */
}

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

In the fixed code, we have implemented proper data uniqueness verification to address the vulnerability.

First, we import the necessary modules, including Express, to create our application. Then, we create an instance of the Express application.

We define a route for the '/register' endpoint using the app.post() method. Inside the route handler, we extract the 'username' from the request body.

To ensure data uniqueness, we call the checkIfUserExists() function, passing the 'username' as an argument. This function is responsible for checking if the username already exists in the database.

If the username already exists, we return an error response with a status code of 400 and a JSON object containing an error message. This prevents the reuse or regeneration of data that should be unique.

If the username does not exist, we proceed with the user registration by calling the registerUser() function and passing the 'username' as an argument. This function is responsible for registering the user in the database.

Finally, we set up the server to listen on port 3000 using the app.listen() method.

Overall, the fixed code ensures that the uniqueness of the data is properly verified before proceeding with user registration, mitigating the vulnerability.

References

• 095.Data uniqueness not properly verified