""" Created on 4 May 2013 @author: mike """ import collections import collections.abc import math from abc import ABCMeta, abstractmethod, abstractproperty from volatility.framework import exceptions, validity from volatility.framework.interfaces import configuration, context class ScannerInterface(validity.ValidityRoutines, metaclass = ABCMeta): """Class for layer scanners that return locations of particular values from within the data These are designed to be given a chunk of data and return a generator which yields any found items. They should NOT perform complex/time-consuming tasks, these should be carried out by the consumer of the generator on the items returned. They will be provided all *available* data (therefore not necessarily contiguous) in ascending offset order, in chunks no larger than chunk_size + overlap where overlap is the amount of data read twice once at the end of an earlier chunk and once at the start of the next chunk. It should be noted that the scanner can maintain state if necessary. Scanners should balance the size of chunk based on the amount of time scanning the chunk will take (ie, do not set an excessively large chunksize and try not to take a significant amount of time in the __call__ method). """ def __init__(self): self.chunk_size = 0x1000000 # Default to 16Mb chunks self.overlap = 0x1000 # A page of overlap by default self._context = None self._layer_name = None @property def context(self): return self._context @context.setter def context(self, ctx): """Stores the context locally in case the scanner needs to access the layer""" self._context = self._check_type(ctx, context.ContextInterface) @property def layer_name(self): return self._layer_name @layer_name.setter def layer_name(self, layer_name): """Stores the layer_name being scanned locally in case the scanner needs to access the layer""" self._layer_name = self._check_type(layer_name, str) @abstractmethod def __call__(self, data, data_offset): """Searches through a chunk of data for a particular value/pattern/etc Always returns an iterator of the same type of object (need not be a volatility object) data is the chunk of data to search through data_offset is the offset within the layer that the data being searched starts at """ class DataLayerInterface(configuration.ConfigurableInterface, validity.ValidityRoutines, metaclass = ABCMeta): """A Layer that directly holds data (and does not translate it""" provides = {"type": "interface"} def __init__(self, context, config_path, name): super().__init__(context, config_path) self._name = self._check_type(name, str) @property def name(self): """Returns the layer name""" return self._name @abstractproperty def maximum_address(self): """Returns the maximum valid address of the space""" @abstractproperty def minimum_address(self): """Returns the minimum valid address of the space""" @property def address_mask(self): """Returns a mask which encapsulates all the actives bit of an address for this layer""" return (1 << int(math.ceil(math.log2(self.maximum_address)))) - 1 @abstractmethod def is_valid(self, offset, length = 1): """Returns a boolean based on whether the offset is valid or not""" @abstractmethod def read(self, offset, length, pad = False): """Reads an offset for length bytes and returns 'bytes' (not 'str') of length size If there is a fault of any kind (such as a page fault), an exception will be thrown unless pad is set, in which case the read errors will be replaced by null characters. """ @abstractmethod def write(self, offset, data): """Writes a chunk of data at offset. Any unavailable sections in the underlying bases will cause an exception to be thrown. Note: Writes are not atomic, therefore some data can be written, even if an exception is thrown. """ def destroy(self): """Allows DataLayers to close any open handles, etc. Systems that make use of Data Layers should called destroy when they are done with them. This will close all handles, and make the object unreadable (exceptions will be thrown using a DataLayer after destruction)""" pass @classmethod def get_requirements(cls): """Returns a list of Requirement objects for this type of layer""" return [] # ## General scanning methods def _pre_scan(self, context, min_address, max_address, progress_callback, scanner): """Prepares the scanner based on standard procedures shared between TranslationLayers and DataLayers""" if progress_callback is not None: self._check_type(progress_callback, collections.Callable) scanner = self._check_type(scanner, ScannerInterface) scanner.context = context scanner.layer_name = self.name if min_address is None: min_address = self.minimum_address if max_address is None: max_address = self.maximum_address min_address = min(self.minimum_address, min_address) max_address = max(self.maximum_address, max_address) total_size = (max_address - min_address) return min_address, max_address, scanner, total_size def scan(self, context, scanner, progress_callback = None, min_address = None, max_address = None): """Scans the layer using scanner, between min_address and max_address calling progress_callback at internvals to report percentage progress""" min_address, max_address, scanner, total_size = self._pre_scan(context, min_address, max_address, progress_callback, scanner) for offset in range(min_address, max_address, scanner.chunk_size): length = min(scanner.chunk_size + scanner.overlap, max_address - offset) chunk = self.read(offset, length) if progress_callback: progress_callback((offset * 100) / total_size) for x in scanner(chunk, offset): yield x def build_configuration(self): config = super().build_configuration() # Translation Layers are constructable, and therefore require a class configuration variable config["class"] = self.__class__.__module__ + "." + self.__class__.__name__ return config class TranslationLayerInterface(DataLayerInterface, metaclass = ABCMeta): # Unfortunately class attributes can't easily be inheritted from parent classes provides = {"type": "interface"} @abstractmethod def mapping(self, offset, length, ignore_errors = False): """Returns a sorted iterable of (offset, mapped_offset, length, layer) mappings ignore_errors will provide all available maps with gaps, but their total length may not add up to the requested length This allows translation layers to provide maps of contiguous regions in one layer """ return [] @property @abstractmethod def dependencies(self): """Returns a list of layer names that this layer translates onto""" return [] # ## Read/Write functions for mapped pages def read(self, offset, length, pad = False): """Reads an offset for length bytes and returns 'bytes' (not 'str') of length size""" current_offset = offset output = [] for (offset, mapped_offset, length, layer) in self.mapping(offset, length, ignore_errors = pad): if not pad and offset > current_offset: raise exceptions.InvalidAddressException(self.name, current_offset, "Layer {} cannot map offset: {}".format(self.name, current_offset)) elif offset > current_offset: output += [b"\x00" * (current_offset - offset)] current_offset = offset elif offset < current_offset: raise exceptions.LayerException("Mapping returned an overlapping element") output += [self._context.memory.read(layer, mapped_offset, length, pad)] current_offset += length recovered_data = b"".join(output) return recovered_data + b"\x00" * (length - len(recovered_data)) def write(self, offset, value): """Writes a value at offset, distributing the writing across any underlying mapping""" current_offset = offset length = len(value) for (offset, mapped_offset, length, layer) in self.mapping(offset, length): if offset > current_offset: raise exceptions.InvalidAddressException(self.name, current_offset, "Layer {} cannot map offset: {}".format(self.name, current_offset)) elif offset < current_offset: raise exceptions.LayerException("Mapping returned an overlapping element") self._context.memory.write(layer, mapped_offset, length) current_offset += length # ## Scan implementation with knowledge of pages def scan(self, context, scanner, progress_callback = None, min_address = None, max_address = None): """Scans a Translation layer by chunk Note: this will skip missing/unmappable chunks of memory """ min_address, max_address, scanner, total_size = self._pre_scan(context, min_address, max_address, progress_callback, scanner) progress = 0 for block in range(min_address, total_size, scanner.chunk_size): for map in self.mapping(block, scanner.chunk_size + scanner.overlap, ignore_errors = True): offset, mapped_offset, length, layer = map chunk = self._context.memory.read(layer, mapped_offset, length) if progress_callback: progress += length progress_callback((progress * 100) / total_size) for x in scanner(chunk, offset): yield x class Memory(validity.ValidityRoutines, collections.abc.Mapping): """Container for multiple layers of data""" def __init__(self): self._layers = {} def read(self, layer, offset, length, pad = False): """Reads from a particular layer at offset for length bytes Returns 'bytes' not 'str' """ return self[layer].read(offset, length, pad) def write(self, layer, offset, data): """Writes to a particular layer at offset for length bytes""" self[layer].write(offset, data) def add_layer(self, layer): """Adds a layer to memory model This will throw an exception if the required dependencies are not met """ self._check_type(layer, DataLayerInterface) if isinstance(layer, TranslationLayerInterface): if layer.name in self._layers: raise exceptions.LayerException("Layer already exists: {}".format(layer.name)) missing_list = [sublayer for sublayer in layer.dependencies if sublayer not in self._layers] if missing_list: raise exceptions.LayerException( "Layer {} has unmet dependencies: {}".format(layer.name, ", ".join(missing_list))) self._layers[layer.name] = layer def del_layer(self, name): """Removes the layer called name This will throw an exception if other layers depend upon this layer """ for layer in self._layers: depend_list = [superlayer for superlayer in self._layers if name in superlayer.dependencies] if depend_list: raise exceptions.LayerException( "Layer {} is depended upon: {}".format(layer.name, ", ".join(depend_list))) self._layers[name].destroy() del self._layers[name] def free_layer_name(self, prefix = "layer"): """Returns an unused layer name""" self._check_type(prefix, str) count = 1 while prefix + str(count) in self: count += 1 return prefix + str(count) def __getitem__(self, name): """Returns the layer of specified name""" return self._layers[name] def __len__(self): return len(self._layers) def __iter__(self): return iter(self._layers) def check_cycles(self): """Runs through the available layers and identifies if there are cycles in the DAG""" # TODO: Is having a cycle check necessary?