zigoo0 / pycobalt

Python API for Cobalt Strike

PyCobalt is a Python API for Cobalt Strike.

Quick Start

Have Python3+ installed on Linux. PyCobalt probably works on macOS and Windows as well. I only test it on Linux though.

First you're going to install the PyCobalt Python library. To do that run python3 setup.py install. If you need more installation help head over to the Installation section.

Now you're ready to start writing PyCobalt scripts. A Python script for PyCobalt looks like this:

#!/usr/bin/env python3

import pycobalt.engine as engine
import pycobalt.aggressor as aggressor
import pycobalt.aliases as aliases

# register this function as a Beacon Console alias
@aliases.alias('example-alias')
def example_alias(bid):
    aggressor.blog2(bid, 'example alias')

# read commands from cobaltstrike. must be called last
engine.loop()

You need to execute this Python script from an Aggressor script. An Aggressor script for PyCobalt looks like this:

$pycobalt_path = '/root/pycobalt/aggressor';
include($pycobalt_path . '/pycobalt.cna');
python(script_resource('example.py'));

It's necessary to set the $pycobalt_path variable so that PyCobalt can find its dependencies.

Now load this Aggressor script into Cobalt Strike. Open up the Cobalt Strike Script Console and you'll see this:

[pycobalt] Executing script /root/pycobalt/example.py

PyCobalt comes with some Script Console commands:

aggressor> python-list
[pycobalt] Running scripts:
 -  /root/pycobalt/example.py

aggressor> python-stop /root/pycobalt/example.py
[pycobalt] Asking script to stop: /root/pycobalt/example.py
[pycobalt] Script process exited: /root/pycobalt/example.py

aggressor> python /root/pycobalt/example.py
[pycobalt] Executing script /root/pycobalt/example.py

aggressor> python-stop-all
[pycobalt] Asking script to stop: /root/pycobalt/example.py
[pycobalt] Script process exited: /root/pycobalt/example.py

When you reload your Aggressor script you should explicitly stop the Python scripts first. Otherwise they'll run forever doing nothing.

aggressor> python-stop-all
[pycobalt] Asking script to stop: /root/pycobalt/example.py
[pycobalt] Script process exited: /root/pycobalt/example.py

aggressor> reload example.cna
[pycobalt] Executing script /root/pycobalt/example.py

You can restart individual scripts as well:

aggressor> python /root/pycobalt/example.py
[pycobalt] /root/pycobalt/example.py is already running. Restarting.
[pycobalt] Asking script to stop: /root/pycobalt/example.py 
[pycobalt] Script process exited: /root/pycobalt/example.py
[pycobalt] Executing script /root/pycobalt/example.py 

For these commands to work properly you can only call PyCobalt in one Aggressor script. Personally I have a single all.cna file with a bunch of calls to python() and include().

PyCobalt Python Library

PyCobalt includes several Python modules. Here's the full list, with links to usage and examples:

• pycobalt.engine: Main communication code
• pycobalt.aggressor: Stubs for calling Aggressor functions
• pycobalt.aliases: Beacon Console alias registration
• pycobalt.commands: Script Console command registration
• pycobalt.events: Event handler registration
• pycobalt.console: Output modifiers and console colors
• pycobalt.gui: Context menu registration
• pycobalt.helpers: Assorted helper functions and classes to make writing scripts easier
• pycobalt.bot: Event Log bot toolkit
• pycobalt.sharpgen: Helper functions for using SharpGen

For full pydoc documentation head over to the docs/ directory.

Usage and Examples

Here are some script examples. For more complete examples see the examples directory.

Script Console Messages

To print a message on the Script Console:

import pycobalt.engine as engine

engine.message('test message')

engine.loop()

This shows up in the Script Console as:

[pycobalt example.py] test message

To print an error message on the Script Console:

import pycobalt.engine as engine

engine.error('test error')

engine.loop()

This shows up in the Script Console as:

[pycobalt example.py error] test error

To print debug messages to the Script Console:

import pycobalt.engine as engine

engine.enable_debug()
engine.debug('debug message 1')
engine.debug('debug message 2')
engine.disable_debug()
engine.debug('debug message 3')

engine.loop()

This shows up in the Script Console as:

[pycobalt example.py debug] debug message 1
[pycobalt example.py debug] debug message 2

To print raw stuff to the Script Console you can just call the Aggressor print functions:

import pycobalt.engine as engine
import pycobalt.aggressor as aggressor

aggressor.println('raw message')

engine.loop()

Aggressor

pycobalt.aggressor provides wrappers for all ~300 Aggressor functions and some Sleep functions. Here's how you call an Aggressor function:

import pycobalt.engine as engine
import pycobalt.aggressor as aggressor

for beacon in aggressor.beacons():
    engine.message(beacon['user'])

engine.loop()

To call an Aggressor function with a callback:

import pycobalt.engine as engine
import pycobalt.aggressor as aggressor

def my_callback(bid, results):
    aggressor.blog2(bid, 'ipconfig: ' + results)

for beacon in aggressor.beacons():
    bid = beacon['bid']
    aggressor.bipconfig(bid, my_callback)

engine.loop()

To call an Aggressor function without printing tasking information to the Beacon Console (! operator, only supported by certain functions):

...
aggressor.bshell(bid, 'whoami', silent=True)
...

For information on calling Sleep or Aggressor functions that aren't in pycobalt.aggressor (including your own Aggressor functions) see the Sleep Functions section below.

For notes on using non-primitive objects such as dialog objects see the Non-Primitive Objects section.

Aliases

pycobalt.aliases provides the ability to register Beacon Console aliases.

import pycobalt.engine as engine
import pycobalt.aliases as aliases
import pycobalt.aggressor as aggressor

@aliases.alias('test_alias')
def test_alias(bid, arg1, arg2='test'):
    aggressor.blog2(bid, 'test alias called with args {} {}'.format(arg1, arg2))

engine.loop()

You can register help info with an alias and it will show up when you run Cobalt Strike's help command:

...
@aliases.alias('test_alias', short_help='Tests alias registration')
...

By default the long help will be based on the short help and Python function syntax. For example:

beacon> help test_alias
Tests alias registration

Syntax: test_alias arg1 [arg2=test]

Or you can specify the long help yourself:

...
@aliases.alias('test_alias', 'Tests alias registration', 'Test alias\n\nLong help')
...

Argument Checking

When the alias is called its arguments will be automagically checked against the arguments of the Python function. For example:

beacon> test_alias 1 2 3
[-] Syntax: test_alias arg1 [arg2=test]

To bypass this you can use python's * operator:

import pycobalt.engine as engine
import pycobalt.aliases as aliases
import pycobalt.aggressor as aggressor

@aliases.alias('test_alias', 'Tests alias registration')
def test_alias(bid, *args):
    aggressor.blog2(bid, 'test alias called with args: ' + ', '.join(args))

engine.loop()

This also allows you to use Python's argparse with aliases. For more information about using argparse see the Argparse section below.

Exception Handling

If an unhandled exception occurs in your alias callback PyCobalt will catch it and print the exception information to the Beacon Console. For example, while I was writing the previous example I typed engine.blog2() instead of aggressor.blog2() by accident and got this error:

beacon> test_alias
[-] Caught Python exception while executing alias 'test_alias': module 'pycobalt.engine' has no attribute 'blog2'
    See Script Console for more details.

In the Script Console:

...
[pycobalt script error] exception: module 'pycobalt.engine' has no attribute 'blog2'
[pycobalt script error] traceback: Traceback (most recent call last):
  File "/usr/lib/python3.7/site-packages/pycobalt-1.0.0-py3.7.egg/pycobalt/engine.py", line 122, in loop
    handle_message(name, message)
  File "/usr/lib/python3.7/site-packages/pycobalt-1.0.0-py3.7.egg/pycobalt/engine.py", line 89, in handle_message
    callbacks.call(callback_name, callback_args)
  File "/usr/lib/python3.7/site-packages/pycobalt-1.0.0-py3.7.egg/pycobalt/callbacks.py", line 42, in call
    callback(*args)
  File "/usr/lib/python3.7/site-packages/pycobalt-1.0.0-py3.7.egg/pycobalt/aliases.py", line 36, in alias_callback
    raise e
  File "/usr/lib/python3.7/site-packages/pycobalt-1.0.0-py3.7.egg/pycobalt/aliases.py", line 32, in alias_callback
    callback(*args)
  File "/sandboxed/tools/cobaltstrike/scripts/recon.py", line 170, in test_alias
    engine.blog2(bid, 'test alias called with args: ' + ', '.join(args))
AttributeError: module 'pycobalt.engine' has no attribute 'blog2'

Double Quotes

Cobalt Strike's Beacon and Script Consoles allow you to pass arguments containing spaces if they're enclosed in double quotes. There's no way to escape double quotes and pass arguments containing both spaces and double quotes though. As a bit of a workaround PyCobalt includes an optional quote replacement mechanism.

To use it simply pass quote_replacement=<string> to the alias registration function or decorator. For example:

...
@aliases.alias('test_alias', quote_replacement='^')
def test_alias(bid, *args):
    aggressor.blog2(bid, 'test alias called with args: ' + ', '.join(args))
...

beacon> test_alias "a ^b^" ^c^
test alias called with args: a "b", "c"

Commands

pycobalt.commands provides the ability to register Script Console commands.

import pycobalt.engine as engine
import pycobalt.commands as commands

@commands.command('test_command')
def test_command():
    engine.message('test_command called')

engine.loop()

Exception handling, argument checking, and double quote replacement is similar to that of aliases. Exceptions are printed to the Script Console.

Events

pycobalt.events provides the ability to register event handlers (Aggressor's on function).

import pycobalt.engine as engine
import pycobalt.events as events

@events.event('beacon_initial')
def beacon_initial_handler(bid):
    aggressor.bnote(bid, 'fresh')

engine.loop()

This will raise an exception if the event isn't one of the official Cobalt Strike ones. To register an arbitrary event (e.g. for use with fireEvent):

...
@events.event('myevent', official_only=False)
...

The arguments to your event callback are checked against incoming events. If they don't match an Exception will be printed to the Script Console.

Console

pycobalt.console provides helpers for working with console output. This includes:

• Registering console output modifiers (Aggressor's set BEACON_OUTPUT).
• Helper functions for coloring and styling text.
• Helper functions for creating ASCII tables and aligned text in the console.

Output Modifiers

Here's how you register output modifiers:

import pycobalt.engine as engine
import pycobalt.console as console

# this is case-insensitive
@console.modifier('beacon_input')
def _(bid, user, text, when):
    # the return text is what you'll see in the Beacon Console
    return user + '> ' + text

engine.loop()

Output modifiers aren't officially documented. I attempted to document them over at docs/console.md.

As usual the arguments to your modifier callbacks are checked. If they don't match an Exception will be printed to the Script Console and an error message will be returned in place of your callback's return value.

Unlike alias, command, and event callbacks, output modifier callbacks are called in Cobalt Strike's main thread. This means you need to write your output modifiers to be relatively fast. In order to avoid freezing up the entire application PyCobalt will timeout and return/print an error if your callback doesn't return within 8 seconds. You may modify this timeout by setting $pycobalt_timeout.

Console Colors

This module also contains console color and style helpers.

...
@aliases.alias('red', 'Print red text to the Beacon Console')
def _(bid, red_text, plain_text=''):
	aggressor.blog2(bid, console.red(red_text) + plain_text)
...

Alternatively you may use the escape codes directly:

...
@aliases.alias('red', 'Print red text to the Beacon Console')
def _(bid, red_text, plain_text=''):
	aggressor.blog2(bid, console.codes['red'] + red_text + console.codes['reset'] + plain_text)
...

There are a bunch of colors and styles. See docs/console.md for the full list.

PS Command Example

Inspired by the Shadow Brokers leak I set out to improve the output of my ps command.

beacon> ps
...
| PID  | PPID |          Name          |                  Description                   |     User     | Session |
+------+------+------------------------+------------------------------------------------+--------------+---------+
|    0 |    0 | [System Process]       | System Idle Process                            |              |         |
|    4 |    0 |     System             | System Kernel                                  |              |         |
|  260 |    4 |         smss           | Session Manager Subsystem                      |              |         |
|  355 |  344 | csrss                  | Client-Server Runtime Server Subsystem         |              |         |
|  418 |  344 | wininit                | Vista background service launcher              |              |         |
|  519 |  418 |     services           | Windows Service Controller                     |              |         |
|  201 |  519 |         svchost        | Microsoft Service Host Process (check path)    |              |         |
|  300 |  519 |         svchost        | Microsoft Service Host Process (check path)    |              |         |
...

The code (examples/ps.py) uses every feature in this module.

GUI

pycobalt.gui provides the ability to register menu trees.

The following menu tree pieces are supported:

• popup
• menu
• item
• insert_menu
• separator

Here's an example using all of those:

import pycobalt.engine as engine
import pycobalt.gui as gui

def beacon_top_callback(bids):
    engine.message('showing menu for: ' + ', '.format(bids))

def node_sysadmin(bids):
    for bid in bids:
        aggressor.bnote(bid, 'sysadmin!')

menu = gui.popup('beacon_top', callback=beacon_top_callback, children=[
    gui.menu('Note', children=[
        gui.insert_menu('note_top'),
        gui.item('sysadmin', callback=note_sysadmin),
        gui.separator(),
        gui.insert_menu('note_bottom'),
    ])
])
gui.register(menu)

engine.loop()

Callbacks are called before children are produced.

GUI registration must happen before engine.loop() is called. engine.loop() creates a new thread in Cobalt Strike and trying to register callbacks for menus created before that point (e.g. beacon_top) will result in a thread safety exception within Java. It's not possible to register menus using the regular Aggressor functions for the same reason.

The one downside to this is that you can't generate the menu labels dynamically from within the menu callbacks.

Bot

pycobalt.bot provides tools for creating Event Log bots.

For example:

import pycobalt.bot as bot
import pycobalt.engine as engine

bot.set_prefix('!')
bot.set_triggers(bot.PRIVMSG, bot.PREFIX, bot.ADDRESSED)
bot.add_help()

@bot.command('test-command', 'Tests bot')
def _(*args):
    for arg in args:
        bot.say(arg)

engine.loop()

Using the example:

event> !help test-command
10/19 10:21:01 <bot> test-command: Tests bot
Syntax: test-command(*args)

event> !test-command arg1 "arg 2" arg3
10/19 10:24:13 <bot> arg1
10/19 10:24:13 <bot> arg 2
10/19 10:24:13 <bot> arg3

See examples/bot.py for more examples.

Helpers

pycobalt.helpers contains helper functions and classes to make writing scripts easier. Here are some of the functions available:

• parse_jobs(content): Parses the output of bjobs as returned by the beacon_output_jobs event. Returns a list of dictionaries. Each dictionary represents a job with the following fields: jid (job ID), pid (process ID), and description.
• parse_ps(content): Parses the callback output of bps. Returns a list of dictionaries. Each dictionary represents a process with the following fields: name, pid, ppid, arch (if available), user (if available), and session (if available).
• parse_ls(content): Parses the callback output of bls. Returns a list of dictionaries. Each dictionary represents a file with the following fields: type ('D' or 'F'), size (in bytes), modified (date and time), and name.
• recurse_ls(bid, directory, callback, depth=9999): Recursively list files with bls and call callback(path) for each file.
• find_process(bid, proc_name, callback): Calls bps to find a process by name and calls callback with a list of matching processes (as returned by parse_ps).
• explorer_stomp(bid, file): Stomps a file timestamp with the modification time of explorer.exe.
• upload_to(bid, local_file, remote_file): Like aggressor.bupload but lets you specify the remote file path/name.
• powershell_quote(arg)/pq(arg): Quote a string for use as an argument to a Powershell function. Encloses in single quotation marks with internal quotation marks escaped.
• argument_quote(arg)/aq(arg): Quote a string for use as an argument to a cmd.exe command that uses CommandLineToArgvW. Read this.
• cmd_quote(arg)/cq(arg): Quote a string for use as an arguent to a cmd.exe command that does not use CommandLineToArgvW.
• execute_assembly_quote(arg)/eaq(arg): Turn a list of arguments into a quoted argument string for aggressor.bexecute_assembly.
• powershell_base64(string): Encode a string as UTF-16LE and base64 it. The output is compatible with Powershell's -EncodedCommand flag.

Argparse

There's a helpers.ArgumentParser class which extends argparse.ArgumentParser to support printing to the Beacon Console, script console, or Event Log. Here's an example using it with an alias:

@aliases.alias('outlook', 'Retrieve an outlook folder', 'See `outlook -h`')
def _(bid, *args):
    parser = helpers.ArgumentParser(bid=bid, prog='outlook')
    parser.add_argument('-f', '--folder', help='Folder name to grab')
    parser.add_argument('-s', '--subject', help='Match subject line (glob)')
    parser.add_argument('-t', '--top', metavar='N', type=int, help='Only show top N results')
    parser.add_argument('-d', '--dump', action='store_true', help='Get full dump')
    parser.add_argument('-o', '--out', help='Output file')
    try: args = parser.parse_args(args)
    except: return
    ...

In the Beacon Console:

beacon> outlook -h
[-] usage: outlook [-h] [-f FOLDER] [-s SUBJECT] [-t N] [-d] [-o OUT]

optional arguments:
  -h, --help            show this help message and exit
  -f FOLDER, --folder FOLDER
                        Folder name to grab
  -s SUBJECT, --subject SUBJECT
                        Match subject line (glob)
  -t N, --top N         Only show top N results
  -d, --dump            Get full dump
  -o OUT, --out OUT     Output file

beacon> outlook -z
[-] unrecognized arguments: -z

To use helpers.ArgumentParser with the Event Log pass event_log=True to the constructor. This is useful for creating bots.

SharpGen

pycobalt.sharpgen provides helpers for compiling and executing C# code with SharpGen.

With the help of SharpGen I've managed to mostly replace PowerShell in my personal Cobalt Strike setup. Read this blog post first if you're interested in using SharpGen.

Functions

The main functions are as follows:

• compile_file(source, ...): Compile a C# file. By default this creates a temporary output file and returns its name.
• compile(code, ...): Compile inline C# code. By default this creates a temporary output file and returns its name.
• execute_file(bid, source, ...): Compile and execute a C# file.
• execute(bid, code, ...): Compile and execute inline C# code.

These functions have a large number of shared keyword arguments. See the module docs for the full list.

Examples

Here's a basic usage example:

import pycobalt.sharpgen as sharpgen
sharpgen.set_location('/root/tools/SharpGen')

@aliases.alias('sharpgen-exec')
def _(bid, code):
    sharpgen.execute(bid, code)

See examples/sharpgen.py for example Script Console commands and Beacon Console aliases to go with each compile/execute function (including a full version of sharpgen-exec).

This module is also pretty useful on its own, independent of Cobalt Strike.

Build Cache

PyCobalt's SharpGen module includes an optional build cache. Using it is pretty simple:

import pycobalt.sharpgen as sharpgen
sharpgen.enable_cache()

@aliases.alias('sharpgen-exec')
def _(bid, code, *args):
    from_cache = sharpgen.execute(bid, code, args)
    if from_cache:
        aggressor.blog2(bid, 'Build was executed from the cache')

The cache works by MD5 hashing your source code before it's compiled. When you call compile_file, compile, execute_file, or execute with the cache enabled PyCobalt will search the cache for your code's hash. If it finds the hash it will return a cached build. Otherwise it will compile your code and add a successful build to the cache.

By default the cache location will be a directory named Cache within your SharpGen directory. You can change the cache location with the sharpgen.set_cache_location(<location>) function.

You can enable or disable the cache for individual compilation calls by passing cache=True or cache=False respectively. To force an overwrite of a cached build you may pass overwrite_cache=True.

To clear the entire cache call sharpgen.clear_cache().

There are other caching-related functions. You'll need to read the module docs or the code for more info.

Setting up SharpGen

You need a compiled version of SharpGen to use this module. By default it points to the repo copy (pycobalt/third_party/SharpGen) which is a Git submodule of github.com/cobbr/SharpGen. To use it you'll need to initialize and build it first. To do that run:

git submodule init
git submodule update
cd third_party/SharpGen
dotnet build

You can use your own copy of SharpGen by calling sharpgen.set_location('<your copy>') or by passing it on the sharpgen_location= parameter to any of the four compile/execute functions.

Advanced Usage

Aggressor Configuration

The PyCobalt Aggressor scripts are configurable with some variables.

Configuration variables for pycobalt.cna:

• $pycobalt_path: Directory containing pycobalt.cna (default: script_resource())
• $pycobalt_python: Location of the Python interpreter (default: "/usr/bin/env python3")
• $pycobalt_debug_on: Enable debug messages (boolean, default: false)
• $pycobalt_timeout: Global timeout value in milliseconds to use for various operations (default: 8000)

Configuration variables for json.cna:

• $json_path: Directory containing json.cna (default: $pycobalt_path)
• $json_jar_file: Full file path of json.jar (default: $json_path . '/jars/json.jar')

Non-Primitive Objects

When passed from Cobalt Strike to Python a non-primitive object's reference is stored. A string identifying this stored reference is passed to Python (let's call it a "serialized reference"). When passed back to Cobalt Strike the serialized reference is deserialized back into the original object reference.

Non-primitive objects are effectively opaque on the Python side.

This also means there's a global reference to every non-primitive object sitting around. To save memory PyCobalt allows you to remove an object's global reference after you're finished referencing it:

...
dialog = aggressor.dialog('Test dialog', {}, callback)
...
aggressor.dialog_show(dialog)
engine.delete(dialog)

I figure passing serialized references around is better than serializing entire Java objects. There's a Python library called javaobj which supports serializing and deserializing Java objects. It doesn't work well with complex Java objects though.

Sleep Functions

You can call arbitrary Sleep and Aggressor functions (including your own Aggressor functions) like this:

engine.call('printAll', [['a', 'b', 'c']])

Which turns into:

printAll(@('a', 'b', 'c'))

To call a Sleep function in its own thread without getting its return value:

engine.call('println', args=['printing from another thread'], fork=True)

You can also eval arbitrary Sleep code:

engine.eval('println("foo")')

engine.eval doesn't perform any sort of parameter marshalling or callback serialization.

Installation

Python Side

Run setup.py install to install the PyCobalt python library.

Or you can run it straight out of the repo if you're familiar with PYTHONPATH.

Cobalt Strike Side

The Aggressor library is in the aggressor directory. It's also installed by setup.py at /usr/lib/python-*/site-packages/pycobalt-*/aggressor.

You can include pycobalt.cna straight out of the repo. It comes with its dependencies and all.

PyCobalt depends on the org.json Java library. A copy is included in this repo at aggressor/jars/json.jar. You can optionally replace json.jar with a more trusted copy. It's PyCobalt's only binary dependency.