How to Write a Simple Plugin¶
This guide will step through how to construct a simple plugin using Volatility 3.
The example plugin we’ll use is
DllList, which features the main traits
of a normal plugin, and reuses other plugins appropriately.
Inherit from PluginInterface¶
The first step is to define a class that inherits from
Volatility automatically finds all plugins defined under the various plugin directories by importing them and then
making use of any classes that inherit from
from volatility.framework import interfaces class DllList(interfaces.plugins.PluginInterface):
The next step is to define the requirements of the plugin, these will be converted into options the user can provide based on the User Interface.
Define the plugin requirements¶
These requirements are the names of variables that will need to be populated in the configuration tree for the plugin to be able to run properly. Any that are defined as optional need not necessarily be provided.
@classmethod def get_requirements(cls): return [requirements.TranslationLayerRequirement(name = 'primary', description = 'Memory layer for the kernel', architectures = ["Intel32", "Intel64"]), requirements.SymbolTableRequirement(name = "nt_symbols", description = "Windows kernel symbols"), requirements.PluginRequirement(name = 'pslist', plugin = pslist.PsList, version = (1, 0, 0)), requirements.IntRequirement(name = 'pid', description = "Process ID to include (all other processes are excluded)", optional = True)]
This is a classmethod, because it is called before the specific plugin object has been instantiated (in order to know how to instantiate the plugin). At the moment these requirements are fairly straightforward:
requirements.TranslationLayerRequirement(name = 'primary', description = 'Memory layer for the kernel', architectures = ["Intel32", "Intel64"]),
This requirement indicates that the plugin will operate on a single
TranslationLayer. The name of the
loaded layer will appear in the plugin’s configuration under the name
The name itself is dynamic depending on the other layers already present in the Context. Always use the value from the configuration rather than attempting to guess what the layer will be called.
Finally, this defines that the translation layer must be on the Intel Architecture. At the moment, this acts as a filter, failing to be satisfied by memory images that do not match the architecture required.
This requirement (and the next two) are known as Complex Requirements, and user interfaces will likely not directly
request a value for this from a user. The value stored in the configuration tree for a
the string name of a layer present in the context’s memory that satisfies the requirement.
Most plugins will only operate on a single layer, but it is entirely possible for a plugin to request two different layers, for example a plugin that carries out some form of difference or statistics against multiple memory images.
requirements.SymbolTableRequirement(name = "nt_symbols", description = "Windows kernel symbols"),
This requirement specifies the need for a particular
to be loaded. This gets populated by various
Automagic as the nearest sibling to a particular
This means that if the
is satisfied and the
Automagic can determine
name of the
SymbolTable will be stored in the configuration.
This requirement is also a Complex Requirement and therefore will not be requested directly from the user.
requirements.PluginRequirement(name = 'pslist', plugin = pslist.PsList, version = (1, 0, 0)),
This requirement indicates that the plugin will make use of another plugin’s code, and specifies the version requirements on that plugin. The version is specified in terms of Semantic Versioning, meaning that to be compatible, the major versions must be identical and the minor version must be equal to or higher than the one provided. This requirement does not make use of any data from the configuration, even if it were provided, it is merely a functional check before running the plugin.
requirements.IntRequirement(name = 'pid', description = "Process ID to include (all other processes are excluded)", optional = True)]
The final requirement is a Simple Requirement, populated by an integer. The description will be presented to the user to
describe what the value represents. The optional flag indicates that the plugin can function without the
being defined within the configuration tree at all.
Define the run method¶
The run method is the primary method called on a plugin. It takes no parameters (these have been passed through the
context’s configuration tree, and the context is provided at plugin initialization time) and returns an unpopulated
TreeGrid object. These are typically constructed based on a
generator that carries out the bulk of the plugin’s processing. The
TreeGrid also specifies the column names and types
that will be output as part of the
def run(self): filter_func = pslist.PsList.create_pid_filter([self.config.get('pid', None)]) return renderers.TreeGrid([("PID", int), ("Process", str), ("Base", format_hints.Hex), ("Size", format_hints.Hex), ("Name", str), ("Path", str)], self._generator(pslist.PsList.list_processes(self.context, self.config['primary'], self.config['nt_symbols'], filter_func = filter_func)))
In this instance, the plugin constructs a filter (using the PsList plugin’s classmethod for creating filters).
It checks the plugin’s configuration for the
pid value, and passes it in as a list if it finds it, or None if
it does not. The
create_pid_filter() method accepts a list of process
identifiers that are included in the list. If the list is empty, all processes are returned.
The next line specifies the columns by their name and type. The types are simple types (int, str, bytes, float, and bool)
but can also provide hints as to how the output should be displayed (such as a hexidecimal number, using
This indicates to user interfaces that the value should be displayed in a particular way, but does not guarantee that the value
will be displayed that way (for example, if it doesn’t make sense to do so in a particular interface).
Finally, the generator is provided. The generator accepts a list of processes, which is gathered using a different plugin,
PsList plugin. That plugin features a classmethod,
so that other plugins can call it. As such, it takes all the necessary parameters rather than accessing them
from a configuration. Since it must be portable code, it takes a context, as well as the layer name,
symbol table and optionally a filter. In this instance we unconditionally
pass it the values from the configuration for the
nt_symbols requirements. This will generate a list
EPROCESS objects, as provided by the
and is not covered here but is used as an example for how to share code across plugins
(both as the provider and the consumer of the shared code).
Define the generator¶
TreeGrid can be populated without a generator,
but it is quite a common model to use. This is where the main processing for this plugin lives.
def _generator(self, procs): for proc in procs: for entry in proc.load_order_modules(): BaseDllName = FullDllName = renderers.UnreadableValue() try: BaseDllName = entry.BaseDllName.get_string() # We assume that if the BaseDllName points to an invalid buffer, so will FullDllName FullDllName = entry.FullDllName.get_string() except exceptions.InvalidAddressException: pass yield (0, (proc.UniqueProcessId, proc.ImageFileName.cast("string", max_length = proc.ImageFileName.vol.count, errors = 'replace'), format_hints.Hex(entry.DllBase), format_hints.Hex(entry.SizeOfImage), BaseDllName, FullDllName))
This iterates through the list of processes and for each one calls the
load_order_modules() method on it. This provides
a list of the loaded modules within the process.
The plugin then defaults the
FullDllName variables to an
which is a way of indicating to the user interface that the value couldn’t be read for some reason (but that it isn’t fatal).
There are currently four different reasons a value may be unreadable:
Unreadble: values which are empty because the data cannot be read
Unparsable: values which are empty because the data cannot be interpreted correctly
NotApplicable: values which are empty because they don’t make sense for this particular entry
NotAvailable: values which cannot be provided now (but might in a future run, via new symbols or an updated plugin)
This is a safety provision to ensure that the data returned by the Volatility library is accurate and describes why information may not be provided.
The plugin then takes the process’s
BaseDllName value, and calls
get_string() on it. All structure attributes,
as defined by the symbols, are directly accessible and use the case-style of the symbol library it came from (in Windows,
attributes are CamelCase), such as
entry.BaseDllName in this instance. Any attribtues not defined by the symbol but added
by Volatility extensions cannot be properties (in case they overlap with the attributes defined in the symbol libraries)
and are therefore always methods and prepended with
get_, in this example
FullDllName is populated. These operations read from memory, and as such, the memory image may be unable to
read the data at a particular offset. This will cause an exception to be thrown. In Volatility 3, exceptions are thrown
as a means of communicating when something exceptional happens. It is the responsibility of the plugin developer to
appropriately catch and handle any non-fatal exceptions and otherwise allow the exception to be thrown by the user interface.
In this instance, the
InvalidAddressException class is caught, which is thrown
by any layer which cannot access an offset requested of it. Since we have already populated both values with
we do not need to write code for the exception handler.
Finally, we yield the record in the format required by the
a tuple, listing the indentation level (for trees) and then the list of values for each column.
This plugin demonstrates casting a value
ImageFileName to ensure it’s returned
as a string with a specific maximum length, rather than its original type (potentially an array of characters, etc).
This is carried out using the
cast() method which takes a type (either a native type, such as string or pointer, or a
structure type defined in a
<table>!_UNICODE) and the parameters to that type.
Since the cast value must populate a string typed column, it had to be a Python string (such as being cast to the native
type string) and could not have been a special Structure such as
_UNICODE. For the format hint columns, the format
hint type must be used to ensure the error checking does not fail.