Secure functionality - File Creation
public function createFile(Request $request) {
$user = Auth::user();
$fileName = $request->input('filename');
$fileContent = $request->input('content');
if ($user->canCreateFiles()) {
// Create the file
Storage::disk('local')->put($fileName, $fileContent);
return response()->json(['status' => 'success', 'message' => 'File created successfully']);
} else {
return response()->json(['status' => 'error', 'message' => 'You do not have permission to create files']);
}
}
The above code is a function in a Laravel controller that creates a file with the given name and content. The function first retrieves the authenticated user and then checks if the user has the permission to create files by calling the
canCreateFiles() method on the user object.
The vulnerability lies in the fact that the permission check is only performed on the frontend by disabling the button for creating files. This means that if a malicious user were to bypass the frontend and send a direct HTTP request to the server, the server would still process the request and create the file, even though the user does not have the necessary permissions.
This is a serious security vulnerability as it allows unauthorized file creation, which can lead to various risks such as data leakage, corruption, or even system compromise if the created file is executable.
The root cause of this vulnerability is the lack of proper access control enforcement on the backend. The backend should always verify the permissions of a user before performing any action on their behalf, regardless of what the frontend is doing.
public function __construct()
{
$this->middleware('can:create,App\\File');
}
public function createFile(Request $request) {
$user = Auth::user();
$fileName = $request->input('filename');
$fileContent = $request->input('content');
// Create the file
Storage::disk('local')->put($fileName, $fileContent);
return response()->json(['status' => 'success', 'message' => 'File created successfully']);
}
The updated code now includes a middleware check in the constructor of the controller. This middleware check uses Laravel's built-in authorization system to ensure that the authenticated user has the necessary permissions to create a file before the
createFile method is even called.
The
can:create,App\\File middleware will call the
create method on the
FilePolicy associated with the
File model. This method should return
true if the user is authorized to create files, and
false otherwise. If the user is not authorized, Laravel will automatically return a 403 HTTP response.
This way, we ensure that the server-side is also validating the user's permissions, not just the client-side. This makes it impossible for a user to bypass the restrictions by simply enabling a disabled button on the front-end.
The actual file creation process remains the same. If the user is authorized, the file will be created and a success message will be returned. If not, the user will receive a 403 error response.
This solution is more secure because it relies on server-side validation, which cannot be manipulated by the user. It also makes use of Laravel's built-in authorization system, which is designed to handle these types of security issues.