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

👉 Overview

👀 What ?

Disable_functions bypass in PHP 7.0-7.4 is a cybersecurity concept that involves circumventing the disable_functions directive in PHP, which is a security feature designed to disable certain functions for security reasons. The bypass is usually performed in *nix environments and primarily concerns versions 7.0 to 7.4 of PHP.

🧐 Why ?

Understanding disable_functions bypass is important because it presents a potential security vulnerability in PHP applications. If a malicious user discovers a way to bypass disable_functions, they can potentially execute forbidden commands, which can lead to unauthorized access, data leaks, or even complete takeover of the system. Therefore, it's crucial for developers and system administrators to understand this concept and how to mitigate the risks associated with it.

⛏️ How ?

To bypass disable_functions in PHP 7.0-7.4, it's common to use 'LD_PRELOAD', an environmental variable in Unix-like operating systems that can be used to load a shared library before any others when a program is run. By preloading a custom library that redefines certain system functions (like 'system()', 'exec()', etc.), you can effectively bypass the disable_functions directive. However, this method requires certain conditions to be met, such as the ability to write files on the server and the absence of security modules like Suhosin or open_basedir restrictions.

⏳ When ?

The practice of bypassing disable_functions in PHP has been around since the introduction of the disable_functions directive, which was included in PHP as a security measure. However, the specific methods for bypassing it in PHP 7.0-7.4 have become more widely known and discussed in the cybersecurity community in recent years. It's important to note that these methods are often used by attackers exploiting vulnerabilities, so they should not be used lightly.

⚙️ Technical Explanations

At a technical level, disable_functions bypass in PHP 7.0-7.4 involves exploiting the dynamic linking process in Unix-like operating systems. The 'LD_PRELOAD' environment variable is used to load a custom shared library before any others when a program is run. This library can contain redefined versions of system functions, which will be used in place of the original functions. The disable_functions directive in PHP only prevents the direct use of certain functions, not their use via system calls. Therefore, by preloading a library that redefines these system calls, you can bypass the disable_functions directive. However, this method has its limitations and depends on the specific system configuration and security measures in place.

🖇️ References