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Lack of data validation - Dates

Need​

Implementation of robust data validation for date fields

Context​

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

Description​

Non compliant code​

public function update(Request $request, $id)
{
    $user = User::find($id);
    $user->update($request->all());
    return response()->json($user, 200);
}

This is a typical example of a Laravel update function. It takes a HTTP request and an ID as parameters. The method tries to find the user with the provided ID and then updates all fields of the user with the data from the request.

The vulnerability here is that there is no validation of the data that is being received from the request. This means that a malicious user could potentially send a request with invalid or malicious data, and the server would process it as a valid request.

For example, if the date_of_birth field is expected to be a date, a malicious user could send a string or an integer, which could lead to unexpected behavior or even security issues.

Additionally, there is no check to ensure that the user sending the request has permission to modify the user with the provided ID. This means that a user could potentially modify another user's data.

In the context of date validation, a user could potentially change their date of birth to a future date or a date that doesn't exist (e.g., February 30th). This could lead to logical errors in the application.

Steps​

  • Implement server-side validation for the incoming request data. This should include checking the data types, lengths, formats, and ranges of the values.
  • Use Laravel's built-in validation rules or create custom validation rules to ensure the data is valid before processing it.
  • Check the user's permissions before allowing them to update certain fields. This can be done using Laravel's authorization features, such as gates and policies.
  • Only allow the fields that are safe to be updated by the user. This can be done by specifying the fillable fields in the User model or by manually specifying the fields to be updated in the update method.
  • Handle validation errors and return appropriate error messages to the client. This can be done using Laravel's built-in error handling features.

Compliant code​

public function update(Request $request, $id)
{
    $validatedData = $request->validate([
        'field1' => 'required|date',
        'field2' => 'required|string|max:255',
        // Add more fields as needed
    ]);

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

    // Check if the user has permission to update the fields
    if (Gate::allows('update-user', $user)) {
        $user->fill($validatedData);
        $user->save();
        return response()->json($user, 200);
    } else {
        return response()->json(['error' => 'Unauthorized'], 403);
    }
}

The updated code now includes server-side validation for the incoming request data using Laravel's built-in validation rules. The validate method on the $request object is used to validate the incoming request data. If the validation fails, a validation exception is thrown and a 422 HTTP response is automatically sent back to the client.

The fields to be validated are specified in the array passed to the validate method. In this example, 'field1' is required to be a valid date and 'field2' is required to be a string with a maximum length of 255 characters. You can add more fields as needed, and use other validation rules as appropriate for your application.

After validating the data, the code checks if the user has permission to update the fields using Laravel's authorization features. In this example, a gate is used to determine if the user is authorized to 'update-user'. If the user is not authorized, a 403 HTTP response is returned to the client with an 'Unauthorized' error message.

If the user is authorized, the validated data is filled into the $user model using the fill method, and the model is saved to the database. The updated user is then returned to the client in a 200 HTTP response.

This way, the server-side validation and authorization checks ensure that only valid and authorized requests are processed, thereby fixing the vulnerability.

References​

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