pwncat

pwncat is a post-exploitation platform for Linux targets. It started out as a wrapper around basic bind and reverse shells and has grown from there. It streamlines common red team operations while staging code from your attacker machine, not the target.

pwncat intercepts the raw communication with a remote shell and allows the user to perform automated actions on the remote host including enumeration, persistence installation and even privilege escalation.

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

• Disable history in the remote shell
• 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 with interactive applications such as vim or nano.

John Hammond and I presented pwncat at GRIMMCon. Our presentation, which covers the usage as well as some of the backend API can be found on YouTube here.

pwncat documentation is being built out on Read the Docs. Head there for the latest usage and development documentation!

Modules

Recently, the architecture of the pwncat framework was redesigned to encorporate a generic "module" structure. All functionality is now implemented as modules. This includes enumeration, persistence and privilege escalation. Interacting with modules is similar to most other post-exploitation platforms. You can utilize the familiar run, search and info commands and enter module contexts with the use command. Refer to the documentation for more information.

Install

pwncat only depends on a working Python development environment. In order to install some of the packages required with pip, you will likely need your distribution's "Python Development" package. On Debian based systems, this is python-dev. For Arch, the development files are shipped with the main Python repository. For Enterprise Linux, the package is named python-devel.

pwncat is configured as a standard python package with distutils. You can install pwncat directly from GitHub with:

pip install git+https://github.com/calebstewart/pwncat.git

Or, you can install after cloning the repository with:

python setup.py install

pwncat depends on a custom fork of paramiko. I'm working on removing this dependency, but sadly my fork of paramiko was never merged upstream so currently that's where we stand. If pip decided not to install the fork (which happens sometimes), then you will get a message from pwncat stating that you have the wrong version with instructions for correcting the dependency failure.

It is recommended to install pwncat from a virtual environment.

python3 -m venv pwncat-env
source pwncat-env/bin/activate
python setup.py install

If you would like to develop custom privilege escalation or persistence modules, we recommend you use the develop target vice the install target for setup.py. This allows changes to the local repository to immediately be observed with your installed package.

The setup script will install three binaries. They are all identical, but provide convenience aliases for pwncat. The three binaries are: pwncat, pc and pcat.

Connecting to a Victim

The command line parameters for pwncat attempt to be flexible and accept a variety of common connection syntax. Specifically, it will try to accept common netcat and ssh like syntax. The following are all valid:

# Connect to a bind shell
pwncat connect://10.10.10.10:4444
pwncat 10.10.10.10:4444
pwncat 10.10.10.10 4444
# Listen for reverse shell
pwncat bind://0.0.0.0:4444
pwncat 0.0.0.0:4444
pwncat :4444
pwncat -lp 4444
# Connect via ssh
pwncat ssh://user:password@10.10.10.10
pwncat user@10.10.10.10
pwncat user:password@10.10.10.10
pwncat -i id_rsa user@10.10.10.10
# SSH w/ non-standard port
pwncat -p 2222 user@10.10.10.10
pwncat user@10.10.10.10:2222
# Reconnect utilizing installed persistence
#   If reconnection failes and no protocol is specified,
#   SSH is used as a fallback.
pwncat reconnect://user@10.10.10.10
pwncat reconnect://user@c228fc49e515628a0c13bdc4759a12bf
pwncat user@10.10.10.10
pwncat c228fc49e515628a0c13bdc4759a12bf
pwncat 10.10.10.10

For more information on the syntax and argument handling, see the help information with pwncat --help or visit the documentation.

Paramiko

When connecting to a host with SSH, paramiko is used to connect. Due to paramiko not implementing the full socket interface, I forked paramiko and implemented the features to make it compatible with a built-in socket. I submitted a pull request with paramiko. The pull request was accepted but has still not been merged. As a result, the setup.py script references my custom fork of paramiko. Some users have had issues where python does not install the custom fork and instead installs standard paramiko. In this case, you will get an error telling you to install the custom fork of paramiko. I'm working on fixing the setup script to ensure the correct version is installed and in the long run would like to remove this dependency eventually. In the meantime, if the fix recommended by pwncat does not work, please comment on issue #60 for help.

Docker Image

The recommended installation method is a Python virtual environment. This provides the easiest day-to-day usage of pwncat. However, there has been interest in using pwncat from a docker image, so I have provided a Dockerfile which provides a working pwncat installation. To build the image use:

docker build -t pwncat .

This will build the pwncat docker image with the tag "pwncat". The working directory within the container is /work. The entrypoint for the container is the pwncat binary. It can be used like so:

# Connect to a bind shell at 10.0.0.1:4444
docker run -v "/some/directory":/work -t pwncat 10.0.0.1 4444

In this example, only the files in /some/directory are exposed to the container. Obviously, for upload/download, the container will only be able to see the files exposed through any mounted directories.

Features and Functionality

pwncat provides two main features. At it's core, it's goal is to automatically setup a remote PseudoTerminal (pty) which allows interaction with the remote host much like a full SSH session. When operating in a pty, you can use common features of your remote shell such as history, line editing, and graphical terminal applications.

The other half of pwncat is a framework which utilizes your remote shell to perform automated enumeration, persistence and privilege escalation tasks. The local pwncat prompt provides a number of useful features for standard penetration tests including:

• File upload and download
• Automated privilege escalation enumeration
• Automated privielge escalation execution
• Automated persistence installation/removal
• Automated tracking of modified/created files
  • pwncat also offers the ability to revert these remote "tampers" automatically

The underlying framework for interacting with the remote host aims to abstract away the underlying shell and connection method as much as possible, allowing commands and plugins to interact seamlessly with the remote host.

You can learn more about interacting with pwncat and about the underlying framework in the documentation. If you have an idea for a new privilege escalation method or persistence method, please take a look at the API documentation specifically. Pull requests are welcome!

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.)
• 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.)

Known Issues

Because pwncat is trying to abstractly interact with any shell with minimal remote system dependencies, there are some edge cases we have found. Where we find them, we do everything we can to account for them and hide them from the user. However, some have slipped through the cracks and been observed in the wild. When this happens, pwncat will do whatever it can to preserve your terminal, but you may be greeted with some peculiar output or command failures.

BSD Support

While BSD is a Unix-based kernel, in practice it's userland tools are noticeably different from their Linux counterparts. Due to this, many of the automated features of pwncat will not work or outright fail when running against a BSD based target. I have tried to catch all errors or edge cases, however there are likely some hiccups which haven't been fully tested against BSD. In any case, the stabilized shell should function within a BSD environment, but I don't provide any guarantees.

If I find some time later down the road, I may try to stabilize pwncat on BSD, but for now my focus is on Linux-based distributions. If you'd like to contribute to making pwncat behave better on BSD, you are more then welcome to reach out or just fork the repo. As always, pull requests are welcome!