• 👉 Overview
• 👀 What ?
• 🧐 Why ?
• ⛏️ How ?
• ⏳ When ?
• ⚙️ Technical Explanations
• 🖇️ References

👉 Overview

👀 What ?

Disable_functions bypass is a technique used in PHP 5.2.3 for evading restrictions set by the disable_functions directive in php.ini file. The Win32std ext is a Windows extension for PHP that provides a set of functions for Windows-specific tasks like interacting with the operating system's underlying functionality. The bypass is usually used to execute system commands that are otherwise restricted.

🧐 Why ?

Understanding disable_functions bypass in PHP is crucial for both developers and security professionals. For developers, it's important to understand this bypass to prevent introducing potential security vulnerabilities in their applications. For security professionals, knowing how this bypass works can help in penetration testing and vulnerability assessments. The use of this bypass can lead to unauthorized command execution, data leakage, and even full system control if not properly managed.

⛏️ How ?

The bypass is achieved by leveraging the functionality of the Win32std extension. Here are the steps: 1. Ensure that the Win32std extension is enabled in the php.ini file. 2. Prepare a PHP script that uses the 'win_shell_execute' function from the Win32std extension to execute the desired system command. 3. Run the PHP script. The 'win_shell_execute' function will execute the system command, bypassing the disable_functions restriction.

⏳ When ?

The use of disable_functions bypass started gaining popularity around the release of PHP 5.2.3, when developers started using the disable_functions directive more frequently to restrict potentially harmful functions in their applications. However, this led to the discovery of bypass techniques, including the one explained in this article.

⚙️ Technical Explanations

The disable_functions directive in PHP is a security feature that allows developers to disable certain functions that can be potentially harmful. However, in PHP 5.2.3, it's possible to bypass this restriction using the Win32std extension for Windows. This extension provides a function called 'win_shell_execute' that can execute system commands. When a PHP script calls this function, it bypasses the disable_functions directive because the execution does not rely on the restricted PHP functions but on the capabilities of the Win32std extension itself. This way, even if the system() function, for example, is disabled in php.ini, an attacker can still execute system commands using the 'win_shell_execute' function.

🖇️ References