Plugin Development

Overview

There are several plugin categories that are available currently:

  • worker
  • connector
  • reader
  • source
  • extractor
  • carver
  • decoder

The worker plugin category is for the plugins that will produce data from payloads and provide the results back to the framework for output. Once the worker plugin is complete, the framework will want to handle the results in some fashion. This is where the connector plugins come into play. Once the results have been provided back to the framework, the connector is then called. The connector plugins may also be used for file archiving if supported within the plugin. One may save a file using a connector by simply calling save() with the archive=True option. Conversely, in order to retrieve a file from MongoDB’s GridFS, one simply would call get_file(). Reader plugins are used to enrich data for worker plugins such as indicator extraction, STIX support, or a multitude of other enhancements. Source plugins handle the messaging and queueing of objects that the worker should handle. For instance, monitoring a directory for new files or AMQP. Extractor plugins handle various tasks such as decompressing zip files and deflating pdf streams. Carver plugins are used to carve content out of payloads (e.g., SWF streams out of DOC files, PE out of RTF, etc...). Decoder plugins provide the capability to automatically decode a payload, such as XOR, ROR, and base64.

Configuration

Each plugin has it’s own configuration file ending in .stoq. Upon initialization of the plugin, the configuration options within the file will be loaded and made available to the worker object.

At a minimum, the below configuration options are required for all plugins.

[Core]
# Name of plugin. stoQ will use this when calling the plugin.
Name = basicplugin
# Name of the .py file for this plugin
Module = basicplugin

[Documentation]
Author = Joe Stoq
Version = 0.1
Website = https://github.com/PUNCH-Cyber/stoq
Description = Basic Plugin Example

If a plugin requires additional configuration parameters, they can be added to the [options] section and will be made available via the plugin object. For example, if we have defined our plugin object as plugin, we can access the hashpayload attribute by calling self.hashpayload.

[options]
hashpayload = True
saveresults = True
max_tlp = red
max_stoq_version = 0.10.3
min_stoq_version = 0.9

Note

As of stoQ version 0.10.3, plugin version checking is supported. If the min/max version of stoQ is not met, processing of the payload will proceed, but the user will be warned unpredictable results may be encountered.

Note

Worker plugins require the hashpayload and saveresults configuration options. No other plugins have additional requirements.

Note

Worker plugin supports a max_tlp option, which will limit it’s ability to scan a payload based on the TLP level of the payload itself. Valid options are red, amber, green, and white. More information on TLP levels can be found at https://www.us-cert.gov/tlp

Plugin Development

A Worker plugin extends the StoqWorkerPlugin class. As such, it must inherit the StoqWorkerPlugin class when initialized. In order to function properly, there must be several methods defined within the worker plugin.

  • __init__
  • activate

The __init__ method is called upon initialization of the plugin. This occurs when the Stoq.load_plugin method is called with the plugin name or when Stoq.collect_plugins plugins is called.

The activate method is automatically called after the plugin has been initialized. When it is called, it must have stoq as an attribute. This allows the plugin to have full access to the stoQ framework and configuration options. The activate method should only be called once by the framework upon initialization. Any initial configuration and command line options should be placed here. This method must also return True in order for the framework to continue, otherwise stoQ will assume that the plugin activation has failed.

Additionally, the deactivate method is called when/if the plugin is ever deactivated, including when stoQ shuts down. This method is not required, though it is recommended should the plugin have any actions that need to cleaning up or if stoQ needs to deactivate the plugin for any reason.

For each of the above core methods, they should minimally call super().METHOD_NAME() right before they return. METHOD_NAME should be changed to the respective method. This will allow the respective parent class execute any required code.

For time-based events (periodic flushes of buffers, etc), every plugin can define a wants_heartbeat property of the plugin. If that property is True, then a separate thread will be launched by stoQ to call the plugin’s heartbeat method. The heartbeat method will be called with the plugin object as its only argument (so heartbeat can be treated as a class method of the plugin). The heartbeat method will only be called once, and it is expected to loop to call whatever periodic actions the plugin wishes to take. For example

def heartbeat(self):
    while True:
        time.sleep(1)
        self._checkCommit()

Note

Actions performed in the heartbeat must be multithread/multiprocess safe. If the actions in the heartbeat may change the values of properties that other plugin methods (like save) may also change, it is the responsibility of the plugin to properly handle locking access to those objects, or find other methods of thread safety.

Note

Also, at present only Worker and Connector plugins are checked to see if they need heartbeats. Others may be added in the future if the need arises.

Workers

In addition to the above requirements, the below method is required for Worker plugins:

  • scan

The scan method is called when stoq-cli.py has a payload available for processing. scan requires two attributes, payload and **kwargs. payload is the payload that the plugin should process. If the plugin does not require a payload, payload will be None. **kwargs is a dict() that contains the message provide by RabbitMQ, or some basic metadata if RabbitMQ is not utilized. Once the scan method has completed processing the payload, it should return it’s results as a dict(). Optionally, if the results do not need to be process, it can return None.

Below is an example of a basic worker plugin.

# Required imports
import argparse
from stoq.args import StoqArgs
from stoq.plugins import StoqWorkerPlugin


# The worker plugin class must be unique. It will be inheriting
# the StoqWorkerPlugin class.
class BasicWorker(StoqWorkerPlugin):

    def __init__(self):
        # In nearly all cases, we do not want to handle anything here
        super().__init__()

    # This function is required in order to initialize the worker.
    # The framework will call the activate() function upon initialization
    # and must return True in order for the framework to continue
    def activate(self, stoq):

        # Ensure the stoQ class is available throughout the
        # plugin
        self.stoq = stoq

        # Instantiate our workers command line argument parser
        parser = argparse.ArgumentParser()

        # Initialize the default requirements for a worker, if needed.
        parser = StoqArgs(parser)

        # Define the argparse group for this plugin
        worker_opts = parser.add_argument_group("Plugin Options")

        # Define the command line arguments for the worker
        worker_opts.add_argument("-r", "--rules",
                                 dest='rulepath',
                                 help="Path to rules file.")

        # The first command line argument is reserved for the framework.
        # The work should only parse everything after the first command
        # line argument. We must always use stoQ's argv object to ensure
        # the plugin is properly instantied whether it is imported or
        # used via a command line script
        options = parser.parse_args(self.stoq.argv[2:])

        # If we need to handle command line argument, let's pass them
        # to super().activate so they can be instantied within the worker
        super().activate(options=options)

        # Must return true, otherwise the framework believes something
        # went wrong
        return True

    # The framework will call the scan() function when it is ready to
    # scan. All of the initial functionality should reside here
    def scan(self, payload, **kwargs):

        # Must return a dict
        kwargs['err'] = "Need more to do!"
        return kwargs

Note

super().activate(options=options) must be called for the plugin to be fully initialized.

Connectors

In addition to the above requirements, the below methods are required for Connector plugins

  • save

The save method is called to save a payload to the specified connector. It must have the payload and **kwargs attributes. The payload attribute should be the data that will be saved via the connector. **kwargs are any additional attributes that the method may require.

Optionally, the below methods can be provided.

  • connect
  • disconnect
  • get_file

connect should be called when a connection, or reconnection, to the connector database is required. Ideally, logic should be placed in save that will call connect to verify a live connection still exists.

disconnect is called when the connector should cleanly disconnect from the database.

get_file is used if the database supports the saving of files. get_file may be used to retrieve any files that are saved to the connector. The **kwargs attribute should contain whatever datapoints are need to retrieve the file.

from stoq.plugins import StoqConnectorPlugin


class BasicConnector(StoqConnectorPlugin):

    def __init__(self):
        super().__init__()

    def activate(self, stoq):
        self.stoq = stoq

        # Any additonal requirements once the connector is activated
        # should be placed here

        super().activate()

    def get_file(self, **kwargs):

        # Code to retrieve file from this connector should be placed here

        # No results, carry on.
        return None

    def save(self, payload, **kwargs):
        """
        Save results to mongodb

        :param str payload: Content to be inserted into database
        :param dict **kwargs: Any additional attributes that should
                                be added to the GridFS object on insert
        """

        # Make sure we have a valid connection
        self.connect()

        # Code to handle saving of the results should be placed here

        super().save()

    def connect(self, force_connect=False):
        # Logic should reside here that determines if we have an
        # active/valid connection, and if not, make one. Otherwise
        # continue on so the framework can save it's results.
        super().connect()

    def disconnect(self):
        super().disconnect()

Readers

In addition to the above requirements, the below method is required for Reader plugins:

  • read

The read method requires the payload attribute, and optionally **kwargs. The payload should be the content that the Reader plugin should process. Any additional attributes should be defined in **kwargs. Once the Reader plugin is done processing the payload, it should return its results.

from stoq.plugins import StoqReaderPlugin


class BasicReader(StoqReaderPlugin):

    def __init__(self):
        super().__init__()

    def activate(self, stoq):
        self.stoq = stoq
        super().activate()

    def read(self, payload, **kwargs):
        """
        Basic Reader

        :param bytes payload: Payload to be processed
        :returns: Content of payload

        """
        return payload

Sources

In addition to the above requirements, the below methods are required for Source plugins:

  • ingest

The ingest method does not require any arrtributes when called. Source plugins should push data back to the worker by calling the worker.multiprocess_put method. This is will pull data back to the main method for processing data in and our of the framework to include retrieving payloads, hashing, metadata generation, result handling, and saving of results.

from stoq.plugins import StoqSourcePlugin


class FileSource(StoqSourcePlugin):

    def __init__(self):
        super().__init__()

    def activate(self, stoq):
        self.stoq = stoq
        super().activate()

    def ingest(self):

        path = "/tmp/bad.exe"
        self.stoq.worker.multiprocess_put(path=path, archive='file')

        return True

A source plugin also requires the multiprocess boolean configuration option in it’s .stoq file under the [options] header. For example:

[options]
multiprocess = True

If set to True, the source plugin will be capable of being run with multiple instances simultaneously. Note: if multiprocess option is set to False the source will still be run in a Python process, but stoq will only run one instance of that process.

Extractors

In addition to the above requirements, the below methods are required for Extractor plugins:

  • extract

extract() must be called with the payload parameter. Optionally, **kwargs may be provided. The plugin may return None or a list of tuples. Index 0 of the tuple must be a dict() containing metadata associated with the decoded content, and Index 1 must be the decoded content itself as bytes.

from stoq.plugins import StoqExtractorPlugin


class ExampleExtractor(StoqExtractorPlugin):

    def __init__(self):
        super().__init__()

    def activate(self, stoq):
        self.stoq = stoq
        super().activate()

    def extract(self, payload, **kwargs):

        # handle any extraction requirements here
        meta = {"size": len(payload), "type": "test"}
        return [(meta, payload)]

Carvers

In addition to the above requirements, the below methods are required for Carver plugins:

  • carve

carve() must be called with the payload parameter. Optionally, **kwargs may be provided. The plugin may return None or a list of tuples. Index 0 of the tuple must be a dict() containing metadata associated with the decoded content, and Index 1 must be the decoded content itself as bytes.

from stoq.plugins import StoqCarverPlugin


class ExampleCarver(StoqExtractorPlugin):

    def __init__(self):
        super().__init__()

    def activate(self, stoq):
        self.stoq = stoq
        super().activate()

    def carve(self, payload, **kwargs):

        # handle any carving requirements here
        meta = {"size": len(payload), "type": "test"}
        return [(meta, payload)]

Decoders

In addition to the above requirements, the below methods are required for Decoder plugins:

  • decode

decode() must be called with the payload parameter. Optionally, **kwargs may be provided. The plugin may return None or a list of tuples. Index 0 of the tuple must be a dict() containing metadata associated with the decoded content, and Index 1 must be the decoded content itself as bytes.

from stoq.plugins import StoqDecoderPlugin


class ExampleDecoder(StoqDecoderPlugin):

    def __init__(self):
        super().__init__()

    def activate(self, stoq):
        self.stoq = stoq
        super().activate()

    def decode(self, payload, **kwargs):

        # handle any decoding requirements here
        meta = {"size": len(payload), "type": "test"}
        return [(meta, payload)]

Packaging Plugins

stoQ provides a method to install plugins and their dependencies utilzing setuptool and pip. In order to leverage the plugin installation feature, some requirements must be met for the plugin package.

  • The plugin package must be a directory
  • The plugin directory must have a subdirectory by the same name as defined in the plugins .stoq configuration file
  • The plugin directory must contain a valid stoQ configuration file
  • The plugin directory must contain a valid stoQ plugin
  • The plugin directory must contain a file named __init__.py
  • Optionally, the archive/directory may contain a valid pip requirements.txt file. The pip packages within this file will automatically be installed with the stoQ plugin.
  • Optionally, a MANIFEST.in file can be included to define which files within the package should be copied to the installation path.

Note

The plugin’s configuration file will not be copied by default, this file should either be defined here or within package_data in setup.py.

As an example, a stoQ plugin archive should have the following structure:

basicworker-plugin/
    setup.py
    MANIFEST.in (optional)
    requirements.txt (optional)
    basicworker/
        __init__.py
        basicworker.stoq
        basicworker.py

The stoQ installation process will extract plugin options from it’s .stoq configuration file. As such, the plugin’s setup.py file should be fairly simple. The below setup.py should suffice for most plugins.:

from setuptools import setup, find_packages

setup(
    name=open("NAME").read(),
    version=open("VERSION").read(),
    author=open("AUTHOR").read(),
    url=open("WEBSITE").read(),
    license="Apache License 2.0",
    description=open("DESCRIPTION").read(),
    packages=find_packages(),
    include_package_data=True,
    classifiers=[
        "Development Status :: 3 - Alpha",
        "Topic :: Utilities",
    ],
)

Templates

stoQ allows for two types of outputs. First, a JSON blob that can be easily parsed in an automated fashion. In addition, stoQ can handle output using Jinja2 templating. This allows for highly customizable and human readable output that may be neccessary in many circumstances. As an example, when using the slack worker plugin, it is not ideal to have hundreds, maybe even thousands, of lines sent to a channel as a result of scanning a payload. With stoQ‘s templating engine, one can easily send human readable and easily digested results to the Slack channel, while at the same time providing the JSON results to a connector for saving into a database for later use.

Using stoQ‘s templates is a simple process. Simply create a templates directory in the plugin’s directory and then create a new template file in Jinja2 format. For example, let’s say we have a worker plugin by the name peinfo. We want to create a Slack template for this plugin. All that is needed now is for a slack.tpl template to be placed in this directory. Now, we just need to run the slack worker with the -T slack.tpl argument. The slack worker plugin will then load the template and render the results.

Additionally, content that is passed to the connector plugin may also be parsed using the templating engine. In order to use this functionality, the worker plugin that is producing the data must have a template named after the connector plugin that is being utilized. For instance, if one would like to ensure the stdout connector output is human readable and not the JSON results, simply create a new template with the name stdout.tpl and call the worker with -T stdout.tpl.

Installing a Plugin

Installation of a stoQ plugin is very simple. Let’s assume that we want to install the basicworker plugin that comes prepackaged with stoQ. We must first package the plugin as detailed above, and then run the command from within the stoQ directory:

stoq-cli.py install basicworker-plugin


    .d8888b.  888             .d88888b.
   d88P  Y88b 888            d88P" "Y88b
   Y88b.      888            888     888
    "Y888b.   888888 .d88b.  888     888
       "Y88b. 888   d88""88b 888     888
         "888 888   888  888 888 Y8b 888
   Y88b  d88P Y88b. Y88..88P Y88b.Y8b88P
    "Y8888P"   "Y888 "Y88P"   "Y888888"
                                    Y8b

[+] Looking for plugin in /vagrant/stoq/plugin-packages/worker/yara...
[+] Found a plugin named yara
[+] yara's category is worker
[+] Installing yara plugin into /vagrant/stoq/stoq/plugins/worker...
[+] Install complete.

Let’s examine what stoQ just did. First, we opened the basicworker-plugin plugin package and began searching for a stoQ plugin configuration file. Once it was found, we loaded it and searched for the Name and Module configuration options within the file. That allowed us to discover the plugin name along with the plugins .py filename. stoQ then discovered the plugin class to determine the full path where the plugin should be installed to. It then called pip to complete the installation.

If a file or directory exists, it will not be overwritten. Instead, a warning message will be displayed letting the user know that the plugin will not be installed. In order to successfully install the plugin, the file or directory must be removed, renamed, or –upgrade be called at the command line.