pwncat

pwncat is a raw bind and reverse shell handler. It streamlines common red team operations and all staging code is from your own attacker machine, not the target.

After receiving a connection, pwncat will setup some common configurations when working with remote shells.

• Unset the HISTFILE environment variable to disable command history
• Normalize shell prompt
• Locate useful binaries (using which)
• Attempt to spawn a pseudoterminal (pty) for a full interactive session

pwncat knows how to spawn pty's with a few different methods and will cross-reference the methods with the executables previously enumerated. After spawning a pty, it will setup the controlling terminal in raw mode, so you can interact in a similar fashion to ssh.

pwncat will also synchronize the remote pty settings (such as rows, columns, TERM environment variable) with your local settings to ensure the shell behaves correctly.

To showcase a little bit of the cool functionality, I have recorded a short asciinema cast.

Install

To install pwncat into its own python virtual environment:

git clone https://github.com/calebstewart/pwncat/ # get pwncat

cd pwncat
sudo apt-get install python3-devel # install dependencies
python3 -m venv .venv
.venv/bin/pip install -r requirements.txt
.venv/bin/python3 setup.py install

. .venv/bin/activate # activate the virtual environment

Usage

# start a reverse shell listener on port 9999
python -m pwncat -r -p 9999

# access a bind shell on a given host and port
python -m pwncat -b -H 127.0.0.1 -p 9999

Features and Functionality

pwncat allows you to local command interpreter at any time by getting to a blank line and pressing the sequence ~C (that's Shift+` then Shift+c). This new prompt provides some basic interaction between your local host and the remote host.

When at this prompt, you can return to your shell at any time with C-d or the "back" command. To get a list of available commands, you can use help. At the time of writing the following commands are supported:

(local) pwncat$ help                                                  
back            Exit command mode 
download        Download a file from the remote host 
help            View help for local commands 
privesc         Attempt privilege escalation 
reset           Reset the remote terminal (calls sync, reset, and sets PS1) 
set             Set or view the currently assigned variables 
sync            Synchronize the remote PTY with the local terminal settings 
upload          Upload a file to the remote host

Transfering Files

Within the local prompt, you have the capability to upload and download files to and from the target. pwncat will attempt to determine a lhost IP address to refer to your attacker machine, but if you need to change this, you can modify the variable like so:

# change local host IP address if you need to
(local) pwncat$ set lhost "8.8.8.8"

The logic to transfer files is defined in pwncat/uploaders and pwncat/downloaders respectively. pwncat will smartly determine a usable method to transfer files, but you can choose a specific one with the --method option.

usage: upload [-h] [--method {nc,curl,shell,bashtcp,wget}] [--output OUTPUT] path

positional arguments:
  path                  path to the file to upload

optional arguments:
  -h, --help            show this help message and exit
  --method, -m {nc,curl,shell,bashtcp,wget}
                        set the download method (default: auto)
  --output OUTPUT, -o OUTPUT
                        path to the output file (default: basename of input)

usage: download [-h] [--method {nc,curl,shell,bashtcp,raw}] [--output OUTPUT] path

positional arguments:
  path                  path to the file to download

optional arguments:
  -h, --help            show this help message and exit
  --method, -m  {nc,curl,shell,bashtcp,raw}
                        set the download method (default: auto)
  --output OUTPUT, -o OUTPUT
                        path to the output file (default: basename of input)

The methods that pwncat can transfer files with are as follows:

Both:
	nc 				netcat socket with random port -- requires port to be accessible
	curl 			HTTP request with port 80 -- requires curl on the target
	shell 			send echo and base64 -- no requirements, but can be slow
	bashtcp 		reuse the current socket -- no requirements
Upload specific:
	wget 			HTTP request with port 80 -- requires wget on the target

Download specific:
	raw 			read file contents and save to attacker -- no requirements

Privilege Escalation

pwncat can attempt to perform privilege escalation with known techniques. It will look for binaries on the target system that have known GTFOBins capabilities, and perform different methods to try and reach new users and ultimately root.

usage: privesc [-h] [--list] [--all]
               [--user {root,caleb,john,sean,etc}]
               [--max-depth MAX_DEPTH] [--read READ] [--write WRITE] [--data DATA] [--text]

optional arguments:
  -h, --help            show this help message and exit
  --list, -l            do not perform escalation. list potential escalation methods
  --all, -a             when listing methods, list for all users. when escalating, escalate to
                        root.
  --user {root,caleb,john,sean,etc}
                        the target user
  --max-depth MAX_DEPTH, -m MAX_DEPTH
                        Maximum depth for the privesc search (default: no maximum)
  --read READ, -r READ  remote filename to try and read
  --write WRITE, -w WRITE
                        attempt to write to a remote file as the specified user
  --data DATA, -d DATA  the data to write a file. ignored if not write mode
  --text, -t            whether to use safe readers/writers

pwncat will try and run all known privilege escalation techniques. The current methods that are supported by privesc are:

sudo 				Run available sudo commands with GTFOBins techniques
setuid 				Run available setuid binaries with GTFOBins techniques
screen 				Abuse screen-4.5.0 (CVE-2017-5618)
dirtycow 			Run DirtyCow exploit (CVE-2016-5195)

BusyBox

If the target system does not have many useful "live-off-the-land" binaries, pwncat can upload an appropriate copy of busybox in order to access more commands.

Planned Features

pwncat would like to be come a red team swiss army knife. Hopefully soon, more features will be added.

• More privilege escalation methods (sudo -u#-1 CVE, LXD containers, etc.)
• More transfer file methods (FTP, SMB, DNS, ICMP, etc. )
• Persistence methods (bind shell, cronjobs, SSH access, PAM abuse, etc.)
• Aggression methods (spam randomness to terminals, flush firewall, etc.)
• Meme methods (terminal-parrot, cowsay, wall, etc.)
• Network methods (port forward, internet access through host, etc.)