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Insecurely deleted files

Need​

Secure file deletion mechanism

Context​

  • Usage of Ruby for developing dynamic and object-oriented applications
  • Usage of the File module for file manipulation and operations

Description​

Non compliant code​

def delete_file(file_path)
  File.delete(file_path)
end

In the above code snippet, the delete_file function is used to delete a file located at file_path. The File.delete method in Ruby is used to delete the specified file. However, this deletion is insecure because the deleted file is not permanently wiped from the system but rather moved to the Recycle Bin, making it possible to restore the file and access its content.

In other words, the file is not securely deleted and can be recovered using various file recovery tools or methods. This is a potential security risk if the file contains sensitive information.

The vulnerability here is that an attacker can potentially recover these files and gain access to sensitive data that was supposed to be deleted. This can lead to information disclosure, which can have serious implications depending on the nature of the data in the file.

Steps​

  • Use a secure file deletion method instead of the default File.delete method.
  • Overwrite the file content before deleting it to ensure it cannot be recovered.
  • Consider using a secure file deletion library or utility that provides more robust file deletion methods.
  • Implement proper access controls to prevent unauthorized deletion of sensitive files.
  • Regularly monitor and audit file deletion activities to detect any suspicious or unauthorized deletions.

Compliant code​

require 'fileutils'

def secure_delete(file_path)
  # Overwrite the file with zeros
  File.open(file_path, 'w') {|f| f.write("\\0" * File.size(file_path)) }
  
  # Delete the file securely
  FileUtils.rm(file_path, :secure => true)
end

The above code provides a secure way to delete files in a Ruby on Rails application.

Firstly, it overwrites the file with zeros. This is done by opening the file in write mode, and then writing a null byte ("\0") for each byte in the file. This ensures that the original content of the file is completely overwritten and cannot be recovered.

After overwriting the file, it is then deleted securely using the FileUtils.rm method with the :secure option set to true. This option ensures that the file is not just removed from the file system, but also overwritten with random data to prevent any possibility of recovery.

This method provides a more secure way to delete files compared to the default File.delete method, which simply removes the file from the file system without overwriting it. This can potentially allow the file to be recovered using specialized software or techniques.

In addition to using a secure file deletion method, it is also important to implement proper access controls to prevent unauthorized deletion of sensitive files, and to regularly monitor and audit file deletion activities to detect any suspicious or unauthorized deletions.

References​

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