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Insecure Use of Dangerous Function

Fixing Command Injection​

About Command Injection

What is command injection?​

Command injection is a type of security vulnerability that allows an attacker to execute arbitrary commands on a target system. It occurs when an application accepts user input as part of a command or query that is executed by the system without proper validation or sanitization.

For example, consider a web application that allows users to search for products by entering a product name. If the application does not properly sanitize user input and passes the input directly to the operating system's command shell, an attacker can insert malicious code into the input that could be executed by the command shell.

This could result in the attacker gaining unauthorized access to the system or performing other malicious actions.

Check out this video for a high-level explanation:

What is the impact of command injection?​

A successful command injection attack can have a wide-ranging impact, depending on the system and the attacker's goals. Here are a few potential impacts:

  • Unauthorized access: An attacker may be able to gain unauthorized access to a system or application, giving them access to sensitive data or functionality.
  • Data theft: An attacker may be able to steal data from the system, including personally identifiable information, financial data, or other sensitive data.
  • Malware installation: An attacker may be able to install malware on the system, allowing them to further compromise the system or use it as a launching point for other attacks.
  • Denial of service: An attacker may be able to launch a denial-of-service attack by executing commands that overwhelm the system's resources, or deleting important system files.
  • System compromise: In some cases, a successful command injection attack can lead to complete compromise of the system, allowing the attacker to take full control.

How to prevent command injection?​

Some measures that can help prevent command injection attacks are:

  • Input validation and sanitization: Ensure that user input is validated and sanitized before it is used in any system command. Use regular expressions or input filters to remove or encode any special characters that could be used to execute arbitrary commands.
  • Use parameterized queries: When executing commands that include user input, use parameterized queries instead of string concatenation.
  • Limit permissions: Limit the permissions of the user account that runs the application to only those that are necessary to perform its functions.
  • Perform regular security audits: Regularly audit your system and application for security vulnerabilities, including command injection vulnerabilities. Use automated tools and manual testing to identify potential issues and fix them before they can be exploited.
  • Educate your development team: Educate your development team about the risks of command injection attacks and the measures that can be taken to prevent them.

References​

Taxonomies​

Explanation & Prevention​

Training​

PHP offers several ways to execute operating system commands, such as:

Option A: Escape dangerous user input​

Solution-specific references:

  1. Go through the issues that GuardRails identified in the PR/MR

  2. Locate the dangerous function. For example:

    # One example is exec, but many other dangerous functions exist in PHP.
    exec('./configure '.$_POST['configure_options']);

  3. Otherwise, replace the dangerous function with the following:

    $command = './configure '.$_POST['configure_options'];
    # For escaping whole command strings use escapeshellcmd
    $escaped_command = escapeshellcmd($command);
    exec($escaped_command)

    or for escaping single arguments:

    # For escaping single arguments escapeshellarg
    $safe_command = './configure ' . escapeshellarg($_POST['configure_options']);
    exec($safe_command)

  4. Test it and ensure the functionality works as expected

  5. Ship it 🚢 and relax 🌴

Option B: Remove the dangerous function​

  1. Using dangerous functions should be avoided whenever possible

    If eval() is the answer, you're almost certainly asking the
    wrong question. -- Rasmus Lerdorf, BDFL of PHP

  2. Go through the issues that GuardRails identified in the PR/MR

  3. Verify if the dangerous function is needed, or can be replaced

  4. Remove the dangerous function

  5. Test it and ensure the functionality works as expected

  6. Ship it 🚢 and relax 🌴

Last updated on by Stefan Streichsbier