Do not use user input to form file paths.

• Rule ID: ruby_lang_path_using_user_input
• Languages: ruby
• Source: path_using_user_input.yml

Description

Using raw unsanitized input when forming filenames or file paths is bad practice. It can lead to path manipulation, by which attackers can gain access to resources outside of the intended scope.

Remediations

❌ Avoid wherever possible

✅ Validate expected file paths using File methods

  path = File.expand("/home/" + params[:resource_name])
  if path.starts_with?("/home/")
    Dir.chdir(path)
  else
    # path is unexpected
  end

Resources

• OWASP path traversal attack

Associated CWE

• CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
• CWE-73: External Control of File Name or Path

OWASP Top 10

• A01:2021 - Broken Access Control
• A04:2021 - Insecure Design