Do not use user input to form file paths.

• Rule ID: php_lang_path_using_user_input
• Languages: php
• 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

✅ Restrict the user input to known values

  $allowed_filenames = array("resource-1", "resource-2");
  $filename = $_GET["resource_name"];

  if (in_array($filename, $allowed_filenames)) {
    readfile("/files/${filename}");
  } else {
    // filename is unexpected
  }

✅ Validate expected file paths

  $path = realpath("/safe/prefix/" . $_GET["resource_name"]);
  if (str_starts_with($path, "/safe/prefix/")) {
    readfile($path);
  } else {
    // path is unexpected
  }

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

Configuration

To skip this rule during a scan, use the following flag

bearer scan /path/to/your-project/ --skip-rule=php_lang_path_using_user_input

To run only this rule during a scan, use the following flag

bearer scan /path/to/your-project/ --only-rule=php_lang_path_using_user_input