👉 Overview
👀 What ?
disable_functions bypass and PHP safe_mode bypass via proc_open() and custom environment exploit are methods used by attackers to run arbitrary commands on a server even when certain functions are disabled for security reasons in PHP.
🧐 Why ?
Understanding this exploit is important as it can be used to run dangerous commands on a server, leading to loss of data, corruption of files, and other forms of damage. It is crucial for developers and system administrators to understand this exploit to effectively protect their systems against it.
⛏️ How ?
The exploit works by calling the proc_open() function with a custom environment. The function proc_open() is used to execute a command and open file pointers for input/output in a child process. By providing a custom environment, an attacker can circumvent the disable_functions and safe_mode restrictions, allowing them to run arbitrary commands.
⏳ When ?
This exploit began to gain attention in the mid-2000s when PHP's safe_mode and disable_functions were commonly used as security measures.
⚙️ Technical Explanations
PHP's safe_mode is a security feature designed to prevent certain functions from being called, which could potentially be used to compromise the server. However, this security feature can be bypassed using the proc_open() function with a custom environment. The custom environment is created using the putenv() function, which allows the attacker to define their own environment variables. By defining the PATH environment variable, the attacker can control which directories are searched when executing system commands, thus bypassing the safe_mode and disabled functions restrictions.