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8009 - Pentesting Apache JServ Protocol (AJP)

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Basic Information

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>

AJP Proxy

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>

Nginx Dockerized-version

git clone https://github.com/ScribblerCoder/nginx-ajp-docker
cd nginx-ajp-docker
Replace TARGET-IP in nginx.conf witg AJP IP then build and run
docker build . -t nginx-ajp-proxy
docker run -it --rm -p 80:80 nginx-ajp-proxy

Apache AJP Proxy

Encountering an open port 8009 without any other accessible web ports is rare. However, it is still possible to exploit it using Metasploit. By leveraging Apache as a proxy, requests can be redirected to Tomcat on port 8009.
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
This setup offers the potential to bypass intrusion detection and prevention systems (IDS/IPS) due to the AJP protocol's binary nature, although this capability has not been verified. By directing a regular Metasploit Tomcat exploit to 127.0.0.1:80, you can effectively seize control of the targeted system.
msf exploit(tomcat_mgr_deploy) > show options

References

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