One critical aspect of server security, especially when running PHP, is the careful management of functions that can pose serious risks if misused. PHP, being a powerful server-side scripting language, offers a plethora of functions that, if not handled with caution, can expose vulnerabilities and potentially compromise the entire web server. Disabling dangerous PHP functions is a crucial step in fortifying the server against various security threats. Here are several reasons why taking this precautionary measure is essential:
Why to Disable PHP Functions
1. Preventing Code Injection Attacks:
Certain PHP functions, such as eval(), system(), and exec(), allow the execution of arbitrary code on the server. Hackers often exploit these functions to inject malicious code into the server, leading to unauthorized access and data breaches. Disabling these functions is a preventive measure against code injection attacks, reducing the attack surface and enhancing overall server security.
2. Mitigating File System Manipulation:
Functions like unlink(), rename(), and rmdir() enable file system manipulation. Disabling these functions helps prevent unauthorized deletion, renaming, or modification of files on the server. Attackers commonly leverage file system manipulation to disrupt services, delete critical files, or gain unauthorized access to sensitive information.
3. Enhancing Database Security:
Certain PHP functions, such as exec(), system(), and shell_exec(), can be exploited to execute arbitrary commands, including those that interact with databases. Disabling these functions mitigates the risk of SQL injection attacks, a prevalent method used by attackers to manipulate databases and gain unauthorized access to sensitive data.
4. Securing Against Cross-Site Scripting (XSS):
Functions like echo() and print() are often used to output data to a web page. If not handled properly, they can become vectors for Cross-Site Scripting attacks. By disabling or carefully controlling the usage of these functions, web developers can minimize the risk of injecting malicious scripts into web pages, thereby safeguarding users against potential attacks.
5. Protecting Server Resources:
Functions like shell_exec(), system(), and passthru() can be resource-intensive, especially if misused or abused by malicious actors. Disabling these functions helps prevent scenarios where the server resources are excessively consumed, leading to denial-of-service (DoS) or distributed denial-of-service (DDoS) attacks. This is critical for maintaining the availability and performance of the web server.
6. Compliance with Security Best Practices:
Security best practices recommend disabling unnecessary or risky functions to reduce the attack surface and potential vulnerabilities. Following these guidelines ensures that the web server aligns with established security standards and is less susceptible to exploitation.
7. Strengthening Overall Server Resilience:
Disabling dangerous PHP functions is part of a comprehensive strategy to strengthen the overall resilience of a web server. By taking a proactive approach to security, web administrators can minimize the likelihood of successful attacks and better protect sensitive data, user information, and the integrity of the server infrastructure.
Here is a complete list of those functions that you can disable on server to increase your web security:
For more details on these functions search it on https://php.net/
How to disable dangerous php functions on WHM server:
You can disable any of the php function by adding it manually to disable_functions inside your php.ini file or through php.ini editor inside whm panel.
1. Log in to WHM
2. Go to Home->Software->MultiPHP INI Editor.
3. Choose the Editor Mode tab.
4. From the drop-down list choose the PHP version you want to edit.
5. In this window search for “disable_functions”.
As shown in the above image write all the php functions you want to disable on your server infront of disable_functions, write all functions coma separated, then click save button.
Now if a function is disabled the user will get a warning message: phpinfo() has been disabled for security reasons