# This file is Copyright 2019 Volatility Foundation and licensed under the Volatility Software License 1.0
# which is available at https://www.volatilityfoundation.org/license/vsl-v1.0
#
"""Module to identify the Directory Table Base and architecture of windows
memory images.
This module contains a PageMapScanner that scans a physical layer to identify self-referential pointers.
All windows versions include a self-referential pointer in their Directory Table Base's top table, in order to
have a single offset that will allow manipulation of the page tables themselves.
In older windows version the self-referential pointer was at a specific fixed index within the table,
which was different for each architecture. In very recent Windows versions, the self-referential pointer
index has been randomized, so a different heuristic must be used. In these versions of windows it was found
that the physical offset for the DTB was always within the range of 0x1a0000 to 0x1b0000. As such, a search
for any self-referential pointer within these pages gives a high probability of being an accurate DTB.
The self-referential indices for older versions of windows are listed below:
+--------------+-------+
| Architecture | Index |
+==============+=======+
| x86 | 0x300 |
+--------------+-------+
| PAE | 0x3 |
+--------------+-------+
| x64 | 0x1ED |
+--------------+-------+
"""
import logging
import struct
from typing import Generator, Iterable, List, Optional, Tuple, Type
from volatility3.framework import constants, interfaces, layers
from volatility3.framework.configuration import requirements
from volatility3.framework.layers import intel
vollog = logging.getLogger(__name__)
[docs]class DtbSelfReferential:
"""A generic DTB test which looks for a self-referential pointer at *any*
index within the page."""
def __init__(self, layer_type: Type[layers.intel.Intel], ptr_struct: str, mask: int,
valid_range: Iterable[int], reserved_bits: int) -> None:
self.layer_type = layer_type
self.ptr_struct = ptr_struct
self.ptr_size = struct.calcsize(ptr_struct)
self.mask = mask
self.page_size: int = layer_type.page_size
self.valid_range = valid_range
self.reserved_bits = reserved_bits
def __call__(self, data: bytes, data_offset: int, page_offset: int) -> Optional[Tuple[int, int]]:
page = data[page_offset:page_offset + self.page_size]
if not page:
return None
ref_pages = set()
for ref in range(0, self.page_size, self.ptr_size):
ptr_data = page[ref:ref + self.ptr_size]
ptr, = struct.unpack(self.ptr_struct, ptr_data)
# For both Intel-32e, bit 7 is reserved (more are reserved in PAE), so if that's ever set,
# we can move on
if (ptr & self.reserved_bits) and (ptr & 0x01):
return None
if ((ptr & self.mask) == (data_offset + page_offset)) and (data_offset + page_offset > 0):
# Pointer must be valid
if (ptr & 0x01):
ref_pages.add(ref)
# The DTB is extremely unlikely to refer back to itself. so the number of reference should always be exactly 1
if len(ref_pages) == 1:
ref_page = ref_pages.pop()
if (ref_page // self.ptr_size) in self.valid_range:
return (data_offset + page_offset), ref_page
return None
[docs]class DtbSelfRef32bit(DtbSelfReferential):
def __init__(self):
super().__init__(layer_type = layers.intel.WindowsIntel,
ptr_struct = "I",
mask = 0xFFFFF000,
valid_range = [0x300],
reserved_bits = 0x0)
[docs]class DtbSelfRef64bit(DtbSelfReferential):
def __init__(self) -> None:
super().__init__(layer_type = layers.intel.WindowsIntel32e,
ptr_struct = "Q",
mask = 0x3FFFFFFFFFF000,
valid_range = range(0x100, 0x1ff),
reserved_bits = 0x80)
[docs]class DtbSelfRef64bitOldWindows(DtbSelfReferential):
def __init__(self) -> None:
super().__init__(layer_type = layers.intel.WindowsIntel32e,
ptr_struct = "Q",
mask = 0x3FFFFFFFFFF000,
valid_range = [0x1ed],
reserved_bits = 0x80)
[docs]class DtbSelfRefPae(DtbSelfReferential):
def __init__(self) -> None:
super().__init__(layer_type = layers.intel.WindowsIntelPAE,
ptr_struct = "Q",
valid_range = [0x3],
mask = 0x3FFFFFFFFFF000,
reserved_bits = 0x0)
@staticmethod
def _and_bytes(abytes, bbytes):
return bytes([a & b for a, b in zip(abytes[::-1], bbytes[::-1])][::-1])
def __call__(self, data: bytes, data_offset: int, page_offset: int) -> Optional[Tuple[int, int]]:
dtb = super().__call__(data, data_offset, page_offset)
if dtb:
# Find the top page
top_pae_page = dtb[0] - 0x4000
# The top page should map to the next four pages after it
# Build what we expect the page table to be
expected_table = b''.join([struct.pack(self.ptr_struct, top_pae_page + (i * 0x1000)) for i in range(1, 5)])
# Mask off the page bits of top level page map
page_table_mask = b"\x00\xf0\xff\xff\xff\xff\xff\xff" * 4
page_table = data[top_pae_page - data_offset: top_pae_page - data_offset + (4 * self.ptr_size)]
# Compare them
anded_bytes = self._and_bytes(page_table, page_table_mask)
if (anded_bytes == expected_table):
return top_pae_page, dtb[1]
# Return None since the dtb value *isn't* None
return None
return dtb
[docs]class PageMapScanner(interfaces.layers.ScannerInterface):
"""Scans through all pages using DTB tests to determine a dtb offset and
architecture."""
overlap = 0x4000
thread_safe = True
tests = [DtbSelfRef64bit(), DtbSelfRefPae(), DtbSelfRef32bit()]
"""The default tests to run when searching for DTBs"""
def __init__(self, tests: Optional[List[DtbSelfReferential]]) -> None:
super().__init__()
if tests:
self.tests = tests
def __call__(self, data: bytes, data_offset: int) -> Generator[Tuple[DtbSelfReferential, int], None, None]:
for page_offset in range(0, len(data), 0x1000):
for test in self.tests:
result = test(data, data_offset, page_offset)
if result is not None:
yield (test, result[0])
[docs]class WindowsIntelStacker(interfaces.automagic.StackerLayerInterface):
stack_order = 40
exclusion_list = ['mac', 'linux']
# Group these by region so we only run over the data once
test_sets = [("Detecting Self-referential pointer for recent windows",
[DtbSelfRef64bit()], [(0x150000, 0x150000), (0x650000, 0xa0000)]),
("Older windows fixed location self-referential pointers",
[DtbSelfRefPae(), DtbSelfRef32bit(), DtbSelfRef64bitOldWindows()], [(0x30000, 0x1000000)])
]
[docs] @classmethod
def stack(cls,
context: interfaces.context.ContextInterface,
layer_name: str,
progress_callback: constants.ProgressCallback = None) -> Optional[interfaces.layers.DataLayerInterface]:
"""Attempts to determine and stack an intel layer on a physical layer
where possible.
Where the DTB scan fails, it attempts a heuristic of checking
for the DTB within a specific range. New versions of windows,
with randomized self-referential pointers, appear to always load
their dtb within a small specific range (`0x1a0000` and
`0x1b0000`), so instead we scan for all self-referential
pointers in that range, and ignore any that contain multiple
self-references (since the DTB is very unlikely to point to
itself more than once).
"""
base_layer = context.layers[layer_name]
if isinstance(base_layer, intel.Intel):
return None
if base_layer.metadata.get('os', None) not in ['Windows', 'Unknown']:
return None
layer = config_path = None
# Check the metadata
if (base_layer.metadata.get('os', None) == 'Windows' and base_layer.metadata.get('page_map_offset')):
arch = base_layer.metadata.get('architecture', None)
if arch not in ['Intel32', 'Intel64']:
return None
# Set the layer type
layer_type: Type = intel.WindowsIntel
if arch == 'Intel64':
layer_type = intel.WindowsIntel32e
elif base_layer.metadata.get('pae', False):
layer_type = intel.WindowsIntelPAE
# Construct the layer
new_layer_name = context.layers.free_layer_name("IntelLayer")
config_path = interfaces.configuration.path_join("IntelHelper", new_layer_name)
context.config[interfaces.configuration.path_join(config_path, "memory_layer")] = layer_name
context.config[interfaces.configuration.path_join(
config_path, "page_map_offset")] = base_layer.metadata['page_map_offset']
layer = layer_type(context, config_path = config_path, name = new_layer_name, metadata = {'os': 'Windows'})
page_map_offset = context.config[interfaces.configuration.path_join(config_path, "page_map_offset")]
vollog.debug(f"DTB was given to us by base layer: {hex(page_map_offset)}")
return layer
# Self Referential finder
for description, tests, sections in cls.test_sets:
vollog.debug(description)
# There is a very high chance that the DTB will live in these very narrow segments, assuming we couldn't find them previously
hits = base_layer.scan(context,
PageMapScanner(tests = tests),
sections = sections,
progress_callback = progress_callback)
# Flatten the generator
def sort_by_tests(x):
"""Key used to sort by tests"""
return tests.index(x[0]), x[1]
def get_max_pointer(page_table, test, ptr_size: int):
"""Determines a pointer from a page_table"""
max_ptr = 0
for index in range(0, len(page_table), ptr_size):
pointer = struct.unpack(test.ptr_struct, page_table[index:index + ptr_size])[0]
# Make sure the pointer is valid, ignore large pages which would require more calculation
if pointer & 0x1 and not pointer & 0x80:
max_ptr = max(max_ptr, (pointer ^ (pointer & 0xfff)) % test.layer_type.maximum_address)
return max_ptr
hits = sorted(list(hits), key = sort_by_tests)
for test, page_map_offset in hits:
# Turn the page tables into integers and find the largest one
page_table = base_layer.read(page_map_offset, 0x1000)
ptr_size = struct.calcsize(test.ptr_struct)
max_pointer = get_max_pointer(page_table, test, ptr_size)
if max_pointer <= base_layer.maximum_address:
vollog.debug(f"{test.__class__.__name__} test succeeded at {hex(page_map_offset)}")
new_layer_name = context.layers.free_layer_name("IntelLayer")
config_path = interfaces.configuration.path_join("IntelHelper", new_layer_name)
context.config[interfaces.configuration.path_join(config_path, "memory_layer")] = layer_name
context.config[
interfaces.configuration.path_join(config_path, "page_map_offset")] = page_map_offset
layer = test.layer_type(context,
config_path = config_path,
name = new_layer_name,
metadata = {'os': 'Windows'})
break
else:
vollog.debug(
f"Max pointer for hit with test {test.__class__.__name__} not met: {hex(max_pointer)} > {hex(base_layer.maximum_address)}")
if layer is not None and config_path:
break
if layer is not None and config_path:
vollog.debug("DTB was found at: 0x{:0x}".format(context.config[interfaces.configuration.path_join(
config_path, "page_map_offset")]))
return layer
[docs]class WinSwapLayers(interfaces.automagic.AutomagicInterface):
"""Class to read swap_layers filenames from single-swap-layers, create the
layers and populate the single-layers swap_layers."""
exclusion_list = ['linux', 'mac']
def __call__(self,
context: interfaces.context.ContextInterface,
config_path: str,
requirement: interfaces.configuration.RequirementInterface,
progress_callback: constants.ProgressCallback = None) -> None:
"""Finds translation layers that can have swap layers added."""
path_join = interfaces.configuration.path_join
self._translation_requirement = self.find_requirements(context,
config_path,
requirement,
requirements.TranslationLayerRequirement,
shortcut = False)
for trans_sub_config, trans_req in self._translation_requirement:
if not isinstance(trans_req, requirements.TranslationLayerRequirement):
# We need this so the type-checker knows we're a TranslationLayerRequirement
continue
swap_sub_config, swap_req = self.find_swap_requirement(trans_sub_config, trans_req)
counter = 0
swap_config = interfaces.configuration.parent_path(swap_sub_config)
if swap_req and swap_req.unsatisfied(context, swap_config):
# See if any of them need constructing
for swap_location in self.config.get('single_swap_locations', []):
# Setup config locations/paths
current_layer_name = swap_req.name + str(counter)
current_layer_path = path_join(swap_sub_config, current_layer_name)
layer_loc_path = path_join(current_layer_path, "location")
layer_class_path = path_join(current_layer_path, "class")
counter += 1
# Fill in the config
if swap_location:
context.config[current_layer_path] = current_layer_name
context.config[layer_loc_path] = swap_location
context.config[layer_class_path] = 'volatility3.framework.layers.physical.FileLayer'
# Add the requirement
new_req = requirements.TranslationLayerRequirement(name = current_layer_name,
description = "Swap Layer",
optional = False)
swap_req.add_requirement(new_req)
context.config[path_join(swap_sub_config, 'number_of_elements')] = counter
context.config[swap_sub_config] = True
swap_req.construct(context, swap_config)
[docs] @staticmethod
def find_swap_requirement(config: str,
requirement: requirements.TranslationLayerRequirement) \
-> Tuple[str, Optional[requirements.LayerListRequirement]]:
"""Takes a Translation layer and returns its swap_layer requirement."""
swap_req = None
for req_name in requirement.requirements:
req = requirement.requirements[req_name]
if isinstance(req, requirements.LayerListRequirement) and req.name == 'swap_layers':
swap_req = req
continue
swap_config = interfaces.configuration.path_join(config, 'swap_layers')
return swap_config, swap_req
[docs] @classmethod
def get_requirements(cls) -> List[interfaces.configuration.RequirementInterface]:
"""Returns the requirements of this plugin."""
return [
requirements.ListRequirement(
name = "single_swap_locations",
element_type = str,
min_elements = 0,
max_elements = 16,
description = "Specifies a list of swap layer URIs for use with single-location",
optional = True)
]