CatTails (Alpha)

Overview

This project is a redteam implant that leverages raw sockets to send/recieve callbacks from a C2 infrastructure. It also offers a library, cattails.go, for users to create their own raw socket applications in Golang. This project does not use host dependecies like libpcap.

The callbacks and communication happen over a UDP port. You will be able to send/execute commands on the remote host via a C2 server.

Current Features

Root commands
- CatTails allows you to send bash commands which will be sent to bots where they will be executed with root privleges.
Bypass Host Firewalls
- CatTails uses raw sockets for the communication between the server and bots. This means that host firewalls will not be able to stop the traffic, allowing you to run commands even when the host is set to drop all.
Command feedback/output
- There is currently no feedback from bots in the alpha verison
Customized HELLO
- I am leaving the implementation of the HELLO messages up the person writing the bot/c2 to allow flexibility. However, there is a function for creating HELLO messages if you choose to use it. The parsing will be left up to the implementation.

v.Alpha Overview

RAW sockets that allow bypass of host-based firewalls
Bots dynamically determine gateway MAC, IP, etc. during install
IP/UDP Header lengths and checksums are properly computed
Packets are properly filtered
Does not use libpcap or similar host dependencies
Payloads are parsed and handled based on C2 or bot needs
Bots will send HELLO messages on a time interval, providing the C2 with client info
C2 simple CLI to interface with bots

Issues at a Glance

Segfault if bot/server receives UDP packets that are not packets for/from CatTails. This issue lies in the parsing of received packets
Possible bottle necking and performance issues when the number of bots reaches around 90+ (more testing needed)
You are currently only able to stage/send commands to ALL hosts or a single, targeted host.
Bug when staging a TARGET command where the server says sending response to for any bot that calls back. This means that the server does not inform the operator that the TARGET command was actually sent to the target.

Usage

CatTails' main purpose is to offer a Golang library that allows people to create and use raw sockets without host dependencies like libpcap. However, I have completed a bot/c2 implementation that, albeit basic, works very well for red team competitions. I included some of the bot/c2 functions in the library as example code, but much of the application level functionality should be handled by the user. I just wanted to create a library so that people would not have to deal with raw sockets.

Configuration

Below you will find instructions on how to configure the bot/c2 for a competition.

To configure the bot and server you will need to edit a few lines in both the server.go, bot.go, and optionally the cattails.go files.

bot.go
- Change the IP Address in main() where cattails.GetOutwardIface() is called. This will be used to auto configure the interface for CatTails to use on the infected machines. This IP is most commonly 8.8.8.8:80 (for general internet access) or you can set this IP as the IP of your server.
- Change the IP Address in main() where go sendHello() is called. This defines the IP address for the CatTails server. This can be the same IP as the bullet above.
- Optional -- Change the SRC and DST port values in sendHello() where cattails.CreatePacket() is called. You will need to change these values based on the filter you set.
server.go
- Change the IP Address in main() where cattails.GetOutwardIface() is called. This will be used to auto configure the interface for CatTails to use on the server. This IP is most commonly set to an infected machine's IP, or some IP that, if you can hit it, means you can also hit the network of the infected hosts.

NOTE

An IP setting is only used for automatic configuration of the CatTails bot/server. Once they are running these IPs no longer matter (except for where the bot is sending data back to the C2). This means if you set the IP address for the server configuration option to an infected machine's IP and you lose the ability to hit that infected machine, you will not lose all of the bots.

cattails.go
- You can change the BPF filter in the cattails.go file. It is defined as var FilterRaw. You can generate these filters by using tcpdump _your-filter-here_ -dd. This will output a BPF struct that implements the filter you made in the tcpdump command. Just copy and paste the struct that tcpdump gave you into cattails.go to replace the current filter.

NOTE

If you replace the filter, remember to configure the bot with the correct filter information otherwise it will not receive any information from the server (Look at the optional configuration for bot.go).

Installation

Installing CatTails is up to the user. Once the bot and server have been configured correctly all you have to do is run the respective binaries on the systems you wish to use. That's it! You do NOT need to run the server before running the bots or vice versa.

SEND THOSE COMMANDS!

Now that you have your server and bots running, you can stage commands through the server CLI. To stage a command, type in the desired bash command to run and hit enter. You should see a message informing you of the staged command. Now whenever a bot calls back, you should see a message that the server sent a response to a bot. When this message appears, it means that the server has sent the command to the bot for execution. To unstage a command hit the enter key once to effectively enter an empty string as the STAGED command (really high tech I know).

To stage a TARGET command, type TARGET into the CatTails> prompt. Then enter the IP of the machine you want to target. Then enter the command you want the target machine to execute. Then wait for that machine to callback! See bugs section To clear a TARGET command you need to type TARGET again into the CLI and spam the enter key to "zero" out the TARGET COMMAND and TARGET IP values (super high tech).

oneNutW0nder / CatTails