mirror of
https://github.com/volatilityfoundation/volatility3.git
synced 2026-08-26 16:12:23 +02:00
Mike Auty
ca8099e7d7
Previously, for segmented layers, no chunk larger than a full segment was scanned. Now, we combine contiguous segments up to scanner.chunk_size (or until a non-present segment) in order to scan it. This may be slightly slower (by concatting the data together) but gives results of hits across page boundaries (the point of the scanning capability), whereas previously each page was scanned individually.
578 lines
25 KiB
Python
578 lines
25 KiB
Python
# This file is Copyright 2019 Volatility Foundation and licensed under the Volatility Software License 1.0
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# which is available at https://www.volatilityfoundation.org/license/vsl-v1.0
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#
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"""Defines layers for containing data.
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One layer may combine other layers, map data based on the data itself,
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or map a procedure (such as decryption) across another layer of data.
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"""
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import collections.abc
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import functools
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import logging
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import math
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import multiprocessing
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import threading
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import traceback
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from abc import ABCMeta, abstractmethod
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from typing import Any, Callable, Dict, Iterable, List, Mapping, Optional, Tuple, Union
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from volatility.framework import constants, exceptions, interfaces
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vollog = logging.getLogger(__name__)
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IMPORTED_MAGIC = False
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try:
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import magic
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IMPORTED_MAGIC = True
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vollog.debug("Imported python-magic, autodetecting compressed files based on content")
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except ImportError:
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pass
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ProgressValue = Union['DummyProgress', multiprocessing.Value]
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IteratorValue = Tuple[List[Tuple[str, int, int]], int]
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class ScannerInterface(metaclass = ABCMeta):
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"""Class for layer scanners that return locations of particular values from
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within the data.
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These are designed to be given a chunk of data and return a generator which yields
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any found items. They should NOT perform complex/time-consuming tasks, these should
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be carried out by the consumer of the generator on the items returned.
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They will be provided all *available* data (therefore not necessarily contiguous)
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in ascending offset order, in chunks no larger than chunk_size + overlap where
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overlap is the amount of data read twice once at the end of an earlier chunk and
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once at the start of the next chunk.
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It should be noted that the scanner can maintain state if necessary.
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Scanners should balance the size of chunk based on the amount of time
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scanning the chunk will take (ie, do not set an excessively large chunksize
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and try not to take a significant amount of time in the __call__ method).
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Scanners must NOT return results found *after* self.chunk_size (ie, entirely contained
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within the overlap). It is the responsibility of the scanner not to return such
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duplicate results.
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Scanners can mark themselves as thread_safe, if they do not require state
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in either their own class or the context. This will allow the scanner to be run
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in parallel against multiple blocks.
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"""
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thread_safe = False
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def __init__(self) -> None:
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self.chunk_size = 0x1000000 # Default to 16Mb chunks
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self.overlap = 0x1000 # A page of overlap by default
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self._context = None # type: Optional[interfaces.context.ContextInterface]
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self._layer_name = None # type: Optional[str]
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@property
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def context(self) -> Optional['interfaces.context.ContextInterface']:
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return self._context
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@context.setter
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def context(self, ctx: 'interfaces.context.ContextInterface') -> None:
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"""Stores the context locally in case the scanner needs to access the
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layer."""
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self._context = ctx
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@property
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def layer_name(self) -> Optional[str]:
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return self._layer_name
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@layer_name.setter
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def layer_name(self, layer_name: str) -> None:
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"""Stores the layer_name being scanned locally in case the scanner
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needs to access the layer."""
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self._layer_name = layer_name
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@abstractmethod
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def __call__(self, data: bytes, data_offset: int) -> Iterable[Any]:
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"""Searches through a chunk of data for a particular value/pattern/etc
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Always returns an iterator of the same type of object (need not be a
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volatility object)
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data is the chunk of data to search through data_offset is the
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offset within the layer that the data being searched starts at
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"""
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class DataLayerInterface(interfaces.configuration.ConfigurableInterface, metaclass = ABCMeta):
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"""A Layer that directly holds data (and does not translate it).
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This is effectively a leaf node in a layer tree. It directly
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accesses a data source and exposes it within volatility.
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"""
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_direct_metadata = collections.ChainMap({}, {
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'architecture': 'Unknown',
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'os': 'Unknown'
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}) # type: collections.ChainMap
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def __init__(self,
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context: 'interfaces.context.ContextInterface',
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config_path: str,
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name: str,
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metadata: Optional[Dict[str, Any]] = None) -> None:
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super().__init__(context, config_path)
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self._name = name
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if metadata:
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self._direct_metadata.update(metadata)
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# Standard attributes
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@property
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def name(self) -> str:
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"""Returns the layer name."""
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return self._name
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@property
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@abstractmethod
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def maximum_address(self) -> int:
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"""Returns the maximum valid address of the space."""
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@property
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@abstractmethod
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def minimum_address(self) -> int:
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"""Returns the minimum valid address of the space."""
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@property
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def address_mask(self) -> int:
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"""Returns a mask which encapsulates all the active bits of an address
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for this layer."""
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return (1 << int(math.ceil(math.log2(self.maximum_address)))) - 1
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@abstractmethod
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def is_valid(self, offset: int, length: int = 1) -> bool:
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"""Returns a boolean based on whether the entire chunk of data (from
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offset to length) is valid or not.
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Args:
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offset: The address to start determining whether bytes are readable/valid
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length: The number of bytes from offset of which to test the validity
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Returns:
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Whether the bytes are valid and accessible
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"""
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@abstractmethod
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def read(self, offset: int, length: int, pad: bool = False) -> bytes:
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"""Reads an offset for length bytes and returns 'bytes' (not 'str') of
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length size.
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If there is a fault of any kind (such as a page fault), an exception will be thrown
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unless pad is set, in which case the read errors will be replaced by null characters.
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Args:
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offset: The offset at which to being reading within the layer
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length: The number of bytes to read within the layer
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pad: A boolean indicating whether exceptions should be raised or bad bytes replaced with null characters
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Returns:
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The bytes read from the layer, starting at offset for length bytes
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"""
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@abstractmethod
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def write(self, offset: int, data: bytes) -> None:
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"""Writes a chunk of data at offset.
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Any unavailable sections in the underlying bases will cause an exception to be thrown.
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Note: Writes are not guaranteed atomic, therefore some data may have been written, even if an exception is thrown.
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"""
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def destroy(self) -> None:
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"""Causes a DataLayer to close any open handles, etc.
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Systems that make use of Data Layers should call destroy when
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they are done with them. This will close all handles, and make
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the object unreadable (exceptions will be thrown using a
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DataLayer after destruction)
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"""
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pass
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@classmethod
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def get_requirements(cls) -> List[interfaces.configuration.RequirementInterface]:
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"""Returns a list of Requirement objects for this type of layer."""
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return []
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@property
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def dependencies(self) -> List[str]:
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"""A list of other layer names required by this layer.
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Note:
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DataLayers must never define other layers
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"""
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return []
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# ## General scanning methods
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def scan(self,
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context: interfaces.context.ContextInterface,
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scanner: ScannerInterface,
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progress_callback: constants.ProgressCallback = None,
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sections: Iterable[Tuple[int, int]] = None) -> Iterable[Any]:
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"""Scans a Translation layer by chunk.
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Note: this will skip missing/unmappable chunks of memory
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Args:
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context: The context containing the data layer
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scanner: The constructed Scanner object to be applied
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progress_callback: Method that is called periodically during scanning to update progress
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sections: A list of (start, size) tuples defining the portions of the layer to scan
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Returns:
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The output iterable from the scanner object having been run against the layer
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"""
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if progress_callback is not None and not callable(progress_callback):
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raise TypeError("Progress_callback is not callable")
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scanner = scanner
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scanner.context = context
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scanner.layer_name = self.name
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if sections is None:
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sections = [(self.minimum_address, self.maximum_address - self.minimum_address)]
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sections = list(self._coalesce_sections(sections))
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try:
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progress = DummyProgress() # type: ProgressValue
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scan_iterator = functools.partial(self._scan_iterator, scanner, sections)
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scan_metric = self._scan_metric(scanner, sections)
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if not scanner.thread_safe or constants.PARALLELISM == constants.Parallelism.Off:
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progress = DummyProgress()
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scan_chunk = functools.partial(self._scan_chunk, scanner, progress)
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for value in scan_iterator():
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if progress_callback:
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progress_callback(scan_metric(progress.value),
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"Scanning {} using {}".format(self.name, scanner.__class__.__name__))
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yield from scan_chunk(value)
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else:
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progress = multiprocessing.Manager().Value("Q", 0)
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parallel_module = multiprocessing
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if constants.PARALLELISM == constants.Parallelism.Threading:
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progress = DummyProgress()
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parallel_module = threading
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scan_chunk = functools.partial(self._scan_chunk, scanner, progress)
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with parallel_module.Pool() as pool:
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result = pool.map_async(scan_chunk, scan_iterator())
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while not result.ready():
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if progress_callback:
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# Run the progress_callback
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progress_callback(scan_metric(progress.value),
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"Scanning {} using {}".format(self.name, scanner.__class__.__name__))
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# Ensures we don't burn CPU cycles going round in a ready waiting loop
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# without delaying the user too long between progress updates/results
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result.wait(0.1)
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for result_value in result.get():
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yield from result_value
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except Exception as e:
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# We don't care the kind of exception, so catch and report on everything, yielding nothing further
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vollog.debug("Scan Failure: {}".format(str(e)))
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vollog.log(constants.LOGLEVEL_VVV,
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"\n".join(traceback.TracebackException.from_exception(e).format(chain = True)))
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def _coalesce_sections(self, sections: Iterable[Tuple[int, int]]) -> Iterable[Tuple[int, int]]:
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"""Take a list of (start, length) sections and coalesce any adjacent
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sections."""
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result = [] # type: List[Tuple[int, int]]
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position = 0
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for (start, length) in sorted(sections):
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if result and start <= position:
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initial_start, _ = result.pop()
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result.append((initial_start, (start + length) - initial_start))
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else:
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result.append((start, length))
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position = start + length
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while result and result[0] < (self.minimum_address, 0):
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first_start, first_length = result[0]
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if first_start + first_length < self.minimum_address:
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result = result[1:]
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elif first_start < self.minimum_address:
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result[0] = (self.minimum_address, (first_start + first_length) - self.minimum_address)
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while result and result[-1] > (self.maximum_address, 0):
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last_start, last_length = result[-1]
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if last_start > self.maximum_address:
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result.pop()
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elif last_start + last_length > self.maximum_address:
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result[1] = (last_start, self.maximum_address - last_start)
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return result
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def _scan_iterator(self, scanner: 'ScannerInterface',
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sections: Iterable[Tuple[int, int]]) -> Iterable[IteratorValue]:
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"""Iterator that indicates which blocks in the layer are to be read by
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for the scanning.
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Returns a list of blocks (potentially in lower layers) that make
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up this chunk contiguously. Chunks can be no bigger than
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scanner.chunk_size + scanner.overlap DataLayers by default are
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assumed to have no holes
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"""
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for section_start, section_length in sections:
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offset, mapped_offset, length, layer_name = section_start, section_start, section_length, self.name
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while length > 0:
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chunk_size = min(length, scanner.chunk_size + scanner.overlap)
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yield [(layer_name, mapped_offset, chunk_size)], offset + chunk_size
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# It we've got more than the scanner's chunk_size, only move up by the chunk_size
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if chunk_size > scanner.chunk_size:
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chunk_size -= scanner.overlap
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length -= chunk_size
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mapped_offset += chunk_size
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offset += chunk_size
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# We ignore the type due to the iterator_value, actually it only needs to match the output from _scan_iterator
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def _scan_chunk(self, scanner: 'ScannerInterface', progress: 'ProgressValue',
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iterator_value: IteratorValue) -> List[Any]:
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data_to_scan, chunk_end = iterator_value
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data = b''
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for layer_name, address, chunk_size in data_to_scan:
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try:
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data += self.context.layers[layer_name].read(address, chunk_size)
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except exceptions.InvalidAddressException:
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vollog.debug("Invalid address in layer {} found scanning {} at address {:x}".format(
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layer_name, self.name, address))
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progress.value = chunk_end
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return list(scanner(data, chunk_end - len(data)))
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def _scan_metric(self, _scanner: 'ScannerInterface', sections: List[Tuple[int, int]]) -> Callable[[int], float]:
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if not sections:
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raise ValueError("Sections have no size, nothing to scan")
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last_section, last_length = sections[-1]
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min_address, _ = sections[0]
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max_address = last_section + last_length
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def _actual_scan_metric(value: int) -> float:
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return max(0, ((value - min_address) * 100) / (max_address - min_address))
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return _actual_scan_metric
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def build_configuration(self) -> interfaces.configuration.HierarchicalDict:
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config = super().build_configuration()
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# Translation Layers are constructable, and therefore require a class configuration variable
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config["class"] = self.__class__.__module__ + "." + self.__class__.__name__
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return config
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# ## Metadata methods
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@property
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def metadata(self) -> Mapping:
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"""Returns a ReadOnly copy of the metadata published by this layer."""
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maps = [self.context.layers[layer_name].metadata for layer_name in self.dependencies]
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return interfaces.objects.ReadOnlyMapping(collections.ChainMap({}, self._direct_metadata, *maps))
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class TranslationLayerInterface(DataLayerInterface, metaclass = ABCMeta):
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"""Provides a layer that translates or transforms another layer or layers.
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Translation layers always depend on another layer (typically
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translating offsets in a virtual offset space into a smaller
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physical offset space).
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"""
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@abstractmethod
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def mapping(self, offset: int, length: int, ignore_errors: bool = False) -> Iterable[Tuple[int, int, int, str]]:
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"""Returns a sorted iterable of (offset, mapped_offset, length, layer)
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mappings.
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ignore_errors will provide all available maps with gaps, but
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their total length may not add up to the requested length This
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allows translation layers to provide maps of contiguous regions
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in one layer
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"""
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return []
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@property
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@abstractmethod
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def dependencies(self) -> List[str]:
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"""Returns a list of layer names that this layer translates onto."""
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return []
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def _decode(self, data: bytes, mapped_offset: int, offset: int) -> bytes:
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"""Decodes any necessary data."""
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return data
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def _encode(self, data: bytes, mapped_offset: int, offset: int) -> bytes:
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"""Encodes any necessary data."""
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return data
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# ## Read/Write functions for mapped pages
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@functools.lru_cache(maxsize = 512)
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def read(self, offset: int, length: int, pad: bool = False) -> bytes:
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"""Reads an offset for length bytes and returns 'bytes' (not 'str') of
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length size."""
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current_offset = offset
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output = [] # type: List[bytes]
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for (layer_offset, mapped_offset, mapped_length, layer) in self.mapping(offset, length, ignore_errors = pad):
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if not pad and layer_offset > current_offset:
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raise exceptions.InvalidAddressException(
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self.name, current_offset, "Layer {} cannot map offset: {}".format(self.name, current_offset))
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elif layer_offset > current_offset:
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output += [b"\x00" * (layer_offset - current_offset)]
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current_offset = layer_offset
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# The layer_offset can be less than the current_offset in non-linearly mapped layers
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# it does not suggest an overlap, but that the data is in an encoded block
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if mapped_length > 0:
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processed_data = self._decode(self._context.layers.read(layer, mapped_offset, mapped_length, pad),
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mapped_offset, layer_offset)
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# Chop off anything unnecessary at the start
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processed_data = processed_data[current_offset - layer_offset:]
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# Chop off anything unnecessary at the end
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processed_data = processed_data[:length - (current_offset - offset)]
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output += [processed_data]
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current_offset += len(processed_data)
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recovered_data = b"".join(output)
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return recovered_data + b"\x00" * (length - len(recovered_data))
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def write(self, offset: int, value: bytes) -> None:
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"""Writes a value at offset, distributing the writing across any
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underlying mapping."""
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current_offset = offset
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length = len(value)
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for (layer_offset, mapped_offset, mapped_length, layer) in self.mapping(offset, length):
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if layer_offset > current_offset:
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raise exceptions.InvalidAddressException(
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self.name, current_offset, "Layer {} cannot map offset: {}".format(self.name, current_offset))
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original_data = self._context.layers.read(layer, mapped_offset, mapped_length)
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# Always chunk the value based on the mapping
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value_to_write = original_data[:current_offset - layer_offset] + value[:mapped_length -
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(current_offset - layer_offset)]
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value = value[mapped_length - (current_offset - layer_offset):]
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encoded_value = self._encode(value_to_write, mapped_offset, layer_offset)
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if len(encoded_value) != mapped_length:
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raise exceptions.LayerException(self.name,
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"Unable to write new value, does not map to the same dimensions")
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self._context.layers.write(layer, mapped_offset, encoded_value)
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current_offset += len(value_to_write)
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# ## Scan implementation with knowledge of pages
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def _scan_iterator(self, scanner: 'ScannerInterface',
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sections: Iterable[Tuple[int, int]]) -> Iterable[IteratorValue]:
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"""Essentially, for paged systems we take a bunch of pages and chunk them up into scanner.page_size or
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as large a chunk as possible (if there are gaps)."""
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for (section_start, section_length) in sections:
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for chunk_start in range(section_start, section_start + section_length, scanner.chunk_size):
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chunk_length = min(section_start + section_length - chunk_start, scanner.chunk_size + scanner.overlap)
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prev_offset = chunk_start
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output = []
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length = 0
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for mapped in self.mapping(chunk_start, chunk_length, ignore_errors = True):
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offset, mapped_offset, length, layer_name = mapped
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if offset != prev_offset:
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if len(output):
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yield output, prev_offset + length
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output = []
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prev_offset = offset + length
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output += [(layer_name, mapped_offset, length)]
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if len(output):
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yield output, prev_offset + length
|
|
|
|
|
|
class LayerContainer(collections.abc.Mapping):
|
|
"""Container for multiple layers of data."""
|
|
|
|
def __init__(self) -> None:
|
|
self._layers = {} # type: Dict[str, DataLayerInterface]
|
|
|
|
def read(self, layer: str, offset: int, length: int, pad: bool = False) -> bytes:
|
|
"""Reads from a particular layer at offset for length bytes.
|
|
|
|
Returns 'bytes' not 'str'
|
|
|
|
Args:
|
|
layer: The name of the layer to read from
|
|
offset: Where to begin reading within the layer
|
|
length: How many bytes to read from the layer
|
|
pad: Whether to raise exceptions or return null bytes when errors occur
|
|
|
|
Returns:
|
|
The result of reading from the requested layer
|
|
"""
|
|
return self[layer].read(offset, length, pad)
|
|
|
|
def write(self, layer: str, offset: int, data: bytes) -> None:
|
|
"""Writes to a particular layer at offset for length bytes."""
|
|
self[layer].write(offset, data)
|
|
|
|
def add_layer(self, layer: DataLayerInterface) -> None:
|
|
"""Adds a layer to memory model.
|
|
|
|
This will throw an exception if the required dependencies are not met
|
|
|
|
Args:
|
|
layer: the layer to add to the list of layers (based on layer.name)
|
|
"""
|
|
if layer.name in self._layers:
|
|
raise exceptions.LayerException(layer.name, "Layer already exists: {}".format(layer.name))
|
|
if isinstance(layer, TranslationLayerInterface):
|
|
missing_list = [sublayer for sublayer in layer.dependencies if sublayer not in self._layers]
|
|
if missing_list:
|
|
raise exceptions.LayerException(
|
|
layer.name, "Layer {} has unmet dependencies: {}".format(layer.name, ", ".join(missing_list)))
|
|
self._layers[layer.name] = layer
|
|
|
|
def del_layer(self, name: str) -> None:
|
|
"""Removes the layer called name.
|
|
|
|
This will throw an exception if other layers depend upon this layer
|
|
|
|
Args:
|
|
name: The name of the layer to delete
|
|
"""
|
|
for layer in self._layers:
|
|
depend_list = [superlayer for superlayer in self._layers if name in self._layers[layer].dependencies]
|
|
if depend_list:
|
|
raise exceptions.LayerException(
|
|
self._layers[layer].name,
|
|
"Layer {} is depended upon: {}".format(self._layers[layer].name, ", ".join(depend_list)))
|
|
self._layers[name].destroy()
|
|
del self._layers[name]
|
|
|
|
def free_layer_name(self, prefix: str = "layer") -> str:
|
|
"""Returns an unused layer name to ensure no collision occurs when
|
|
inserting a layer.
|
|
|
|
Args:
|
|
prefix: A descriptive string with which to prefix the layer name
|
|
|
|
Returns:
|
|
A string containing a name, prefixed with prefix, not currently in use within the LayerContainer
|
|
"""
|
|
if prefix not in self:
|
|
return prefix
|
|
count = 1
|
|
while "{}_{}".format(prefix, count) in self:
|
|
count += 1
|
|
return "{}_{}".format(prefix, count)
|
|
|
|
def __getitem__(self, name: str) -> DataLayerInterface:
|
|
"""Returns the layer of specified name."""
|
|
return self._layers[name]
|
|
|
|
def __len__(self) -> int:
|
|
return len(self._layers)
|
|
|
|
def __iter__(self):
|
|
return iter(self._layers)
|
|
|
|
def check_cycles(self) -> None:
|
|
"""Runs through the available layers and identifies if there are cycles
|
|
in the DAG."""
|
|
# TODO: Is having a cycle check necessary?
|
|
raise NotImplementedError("Cycle checking has not yet been implemented")
|
|
|
|
|
|
class DummyProgress(object):
|
|
"""A class to emulate Multiprocessing/threading Value objects."""
|
|
|
|
def __init__(self):
|
|
self.value = 0
|