8009 - Pentesting Apache JServ Protocol (AJP)

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Basic Information

From: https://diablohorn.com/2011/10/19/8009-the-forgotten-tomcat-port/

AJP is a wire protocol. It an optimized version of the HTTP protocol to allow a standalone web server such as Apache to talk to Tomcat. Historically, Apache has been much faster than Tomcat at serving static content. The idea is to let Apache serve the static content when possible, but proxy the request to Tomcat for Tomcat related content.

Also interesting:

The ajp13 protocol is packet-oriented. A binary format was presumably chosen over the more readable plain text for reasons of performance. The web server communicates with the servlet container over TCP connections. To cut down on the expensive process of socket creation, the web server will attempt to maintain persistent TCP connections to the servlet container, and to reuse a connection for multiple request/response cycles

Default port: 8009

PORT     STATE SERVICE
8009/tcp open  ajp13

CVE-2020-1938 'Ghostcat'

If the AJP port is exposed, Tomcat might be susceptible to the Ghostcat vulnerability. Here is an exploit that works with this issue.

Ghostcat is a LFI vulnerability, but somewhat restricted: only files from a certain path can be pulled. Still, this can include files like WEB-INF/web.xml which can leak important information like credentials for the Tomcat interface, depending on the server setup.

Patched versions at or above 9.0.31, 8.5.51, and 7.0.100 have fixed this issue.

Enumeration

Automatic

nmap -sV --script ajp-auth,ajp-headers,ajp-methods,ajp-request -n -p 8009 <IP>

Brute force

AJP Proxy

Apache AJP Proxy

It’s not often that you encounter port 8009 open and no other web port open. In which case it would be nice to use existing tools like metasploit to still pwn it right? As stated in one of the quotes you can (ab)use Apache to proxy the requests to Tomcat port 8009. In the references you will find a nice guide on how to do that (read it first), what follows is just an overview of the commands I used on my own machine. I omitted some of the original instruction since they didn’t seem to be necessary.

sudo apt-get install libapache2-mod-jk
sudo vim /etc/apache2/apache2.conf # append the following line to the config
    Include ajp.conf
sudo vim /etc/apache2/ajp.conf     # create the following file, change HOST to the target address 
    ProxyRequests Off
    <Proxy *>
        Order deny,allow
        Deny from all
        Allow from localhost
    </Proxy>
    ProxyPass       / ajp://HOST:8009/
    ProxyPassReverse    / ajp://HOST:8009/
sudo a2enmod proxy_http
sudo a2enmod proxy_ajp
sudo systemctl restart apache2

A nice side effect of using this setup is that you might thwart IDS/IPS systems in place since the AJP protocol is somewhat binary, but I haven’t verified this. Now you can just point your regular metasploit tomcat exploit to 127.0.0.1:80 and take over that system. Here is the metasploit output also:

msf  exploit(tomcat_mgr_deploy) > show options

Module options (exploit/multi/http/tomcat_mgr_deploy):

   Name      Current Setting  Required  Description
   ----      ---------------  --------  -----------
   PASSWORD  tomcat           no        The password for the specified username
   PATH      /manager         yes       The URI path of the manager app (/deploy and /undeploy will be used)
   Proxies                    no        Use a proxy chain
   RHOST     localhost        yes       The target address
   RPORT     80               yes       The target port
   USERNAME  tomcat           no        The username to authenticate as
   VHOST                      no        HTTP server virtual host

Nginx Reverse Proxy & AJP

When we come across an open AJP proxy port (8009 TCP), we can use Nginx with the ajp_module to access the "hidden" Tomcat Manager. This can be done by compiling the Nginx source code and adding the required module, as follows:

Download the Nginx source code
Download the required module
Compile Nginx source code with the ajp_module.
Create a configuration file pointing to the AJP Port

# Download Nginx code
wget https://nginx.org/download/nginx-1.21.3.tar.gz
tar -xzvf nginx-1.21.3.tar.gz

# Compile Nginx source code with the ajp module
git clone https://github.com/dvershinin/nginx_ajp_module.git
cd nginx-1.21.3
sudo apt install libpcre3-dev
./configure --add-module=`pwd`/../nginx_ajp_module --prefix=/etc/nginx --sbin-path=/usr/sbin/nginx --modules-path=/usr/lib/nginx/modules
make
sudo make install
nginx -V

Comment out the entire server block and append the following lines inside the http block in /etc/nginx/conf/nginx.conf.

upstream tomcats {
	server <TARGET_SERVER>:8009;
	keepalive 10;
	}
server {
	listen 80;
	location / {
		ajp_keep_conn on;
		ajp_pass tomcats;
	}
}

Start Nginx and check if everything is working correctly by issuing a cURL request to your local host.

sudo nginx
curl http://127.0.0.1:80

<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8" />
        <title>Apache Tomcat/X.X.XX</title>
        <link href="favicon.ico" rel="icon" type="image/x-icon" />
        <link href="favicon.ico" rel="shortcut icon" type="image/x-icon" />
        <link href="tomcat.css" rel="stylesheet" type="text/css" />
    </headas
    <body>
        <div id="wrapper">
            <div id="navigation" class="curved container">
                <span id="nav-home"><a href="https://tomcat.apache.org/">Home</a></span>
                <span id="nav-hosts"><a href="/docs/">Documentation</a></span>
                <span id="nav-config"><a href="/docs/config/">Configuration</a></span>
                <span id="nav-examples"><a href="/examples/">Examples</a></span>
                <span id="nav-wiki"><a href="https://wiki.apache.org/tomcat/FrontPage">Wiki</a></span>
                <span id="nav-lists"><a href="https://tomcat.apache.org/lists.html">Mailing Lists</a></span>
                <span id="nav-help"><a href="https://tomcat.apache.org/findhelp.html">Find Help</a></span>
                <br class="separator" />
            </div>
            <div id="asf-box">
                <h1>Apache Tomcat/X.X.XX</h1>
            </div>
            <div id="upper" class="curved container">
                <div id="congrats" class="curved container">
                    <h2>If you're seeing this, you've successfully installed Tomcat. Congratulations!</h2>
<SNIP>

References

https://academy.hackthebox.com/module/145/section/1295