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Lack of data validation - Content Spoofing

Need​

Implementation of robust data validation and authentication mechanisms

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 response for handling HTTP responses in a Node.js application

Description​

Non compliant code​

public function uploadFile(Request $request)
{
    if($request->hasFile('file')){
        $file = $request->file('file');
        $name = $file->getClientOriginalName();
        $path = public_path('/uploads');
        $file->move($path, $name);
        return response()->json(['success' => 'File uploaded successfully.']);
    }
    else{
        return response()->json(['error' => 'No file was uploaded.']);
    }
}

This vulnerable code is a function within a Laravel controller that handles file uploads.

The function uploadFile takes a Request object as a parameter. It checks if the request contains a file using the hasFile method. If a file is present, it retrieves the file using the file method, gets the original name of the file with getClientOriginalName, defines the path where the file will be stored with public_path, and then moves the file to the defined path with the move method.

The vulnerability lies in the fact that there is no validation of the file being uploaded. An attacker can generate a token without credentials and replace files that have already been uploaded by a client. The application does not validate if these files were already sent in the file upload request.

This lack of data validation can lead to Content Spoofing, where an attacker can make it appear as though the application is presenting content which is not actually from the application. This can lead to a variety of attacks, such as phishing or defacement attacks.

To fix this vulnerability, the application needs to implement data validation checks to ensure that a file with the same name does not already exist in the upload directory, and also validate the authenticity of the user uploading the file.

Steps​

  • Implement a validation mechanism to check if a file with the same name already exists in the upload directory before moving the new file.
  • Generate a unique name for each uploaded file to prevent overwriting existing files. This can be done by appending a timestamp or a unique ID to the original file name.
  • Implement an authentication mechanism to ensure that only authorized users can upload files.
  • Implement a token-based system where each upload request must include a valid token. The token should be generated server-side and associated with the user's session.
  • Ensure that the token is validated server-side before processing the upload request.

Compliant code​

public function uploadFile(Request $request)
{
    if($request->hasFile('file')){
        $file = $request->file('file');
        $name = $file->getClientOriginalName();
        $path = public_path('/uploads');

        // Generate a unique name for the file
        $uniqueName = time() . '_' . $name;

        // Check if a file with the same name already exists
        if(file_exists($path . '/' . $uniqueName)){
            return response()->json(['error' => 'A file with the same name already exists.']);
        }

        // Move the file to the upload directory
        $file->move($path, $uniqueName);

        return response()->json(['success' => 'File uploaded successfully.']);
    }
    else{
        return response()->json(['error' => 'No file was uploaded.']);
    }
}

The updated code includes a validation mechanism to check if a file with the same name already exists in the upload directory before moving the new file. This is done using the file_exists function.

A unique name is generated for each uploaded file to prevent overwriting existing files. This is done by appending a timestamp to the original file name.

Please note that this code does not include an authentication mechanism or a token-based system. These should be implemented separately to ensure that only authorized users can upload files and that each upload request includes a valid token. The token should be generated server-side and associated with the user's session, and it should be validated server-side before processing the upload request.

References​

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