Unauthorized access to files - PHP

Unauthorized access to files - PHP

Need

Prevention of unauthorized access to files and functionalities

Context

  • Usage of PHP 7.0 for server-side scripting and web development
  • Usage of Request for making HTTP requests in Node.js
  • Usage of the User dependency for managing user-related functionality

Description

Non compliant code

        public function updateUser(Request $request, $id)
{
    $user = User::find($id);
    $user->name = $request->get('name');
    $user->email = $request->get('email');
    $user->password = bcrypt($request->get('password'));
    $user->save();
    return redirect('users')->with('success', 'User has been updated');
}

In the above PHP code, we are using Laravel's Eloquent ORM to interact with the database. The function updateUser is supposed to update a user's details.

The vulnerability lies in the fact that the code does not sanitize or validate the user input received from the request. It directly uses the input from the request to update the user details in the database. This can potentially allow a user to inject malicious characters or scripts into the user fields, leading to various security issues such as SQL Injection, Cross-Site Scripting (XSS), etc.

Furthermore, there is no authorization check to verify if the user making the request has the necessary permissions to update the user details. This can lead to unauthorized access and modification of user data.

This vulnerability can be exploited to gain unauthorized access to functionalities and files, as the application is connected to Sharepoint.

Steps

  • Validate and sanitize the input data: Ensure that the data provided by the user is valid and safe. Use Laravel's built-in validation rules to check for appropriate data types, lengths, formats, etc. Also, sanitize the data to remove any potentially harmful characters or strings.
  • Implement authorization checks: Before allowing a user to update data, check if they have the necessary permissions to do so. Laravel's built-in authorization services can be used for this purpose.
  • Use prepared statements for database queries: This can help prevent SQL injection attacks. Laravel's query builder uses PDO parameter binding, which protects your application from SQL injection.
  • Limit the data that can be updated: Instead of allowing any user data to be updated, specify which fields can be updated in the request. This can be done using Laravel's fillable property on the model.
  • Implement rate limiting: This can help prevent brute force attacks. Laravel provides middleware for rate limiting.

Compliant code

        public function updateUser(Request $request, $id)
{
    $validatedData = $request->validate([
        'name' => 'required|max:255',
        'email' => 'required|email|max:255',
        'password' => 'required|min:8',
    ]);

    $user = User::find($id);

    if (Gate::denies('update-user', $user)) {
        abort(403);
    }

    $user->name = $validatedData['name'];
    $user->email = $validatedData['email'];
    $user->password = bcrypt($validatedData['password']);
    $user->save();

    return redirect('users')->with('success', 'User has been updated');
}

The updated code includes several security measures to prevent unauthorized access to files:

1. Input Validation: The validate method is used to ensure that the data provided by the user is valid and safe. The 'name' and 'email' fields are required and must not exceed 255 characters. The 'email' field must be a valid email address. The 'password' field is required and must be at least 8 characters long.

2. Authorization Checks: The Gate::denies method is used to check if the user has the necessary permissions to update the data. If the user does not have the necessary permissions, a 403 error is returned.

3. Prepared Statements: Laravel's query builder uses PDO parameter binding, which protects your application from SQL injection. This is already implemented in the find and save methods.

4. Limited Data Update: Only the 'name', 'email', and 'password' fields can be updated. This is controlled by the input validation rules.

5. Rate Limiting: Although not shown in this code snippet, Laravel provides middleware for rate limiting, which can help prevent brute force attacks. This should be implemented in the routes file.

By implementing these security measures, the vulnerability of unauthorized access to files is mitigated.

References