Add patch for driverscan for windows 7 and earlier

This patches an issue for some versions of windows that require the
bottom-up approach for finding the size of "object body" by
recognizing additional structures occupying the "object body"
position. The sizes of these additional structures are added to
the size of `_DRIVER_OBJECT` to more accurately compute the actual
size of "object body".

volatility3/framework/symbols/windows/extensions/pool.py

@@ -5,6 +5,7 @@ from typing import Optional, Tuple, List, Dict, Union
 
 from volatility3.framework import objects, interfaces, constants, symbols, exceptions, renderers
 from volatility3.framework.renderers import conversion
+from volatility3.plugins.windows.poolscanner import PoolConstraint
 
 vollog = logging.getLogger(__name__)
 
@@ -17,9 +18,8 @@ class POOL_HEADER(objects.StructType):
     """
 
     def get_object(self,
-                   type_name: str,
+                   constraint: PoolConstraint,
                    use_top_down: bool,
-                   executive: bool = False,
                    kernel_symbol_table: Optional[str] = None,
                    native_layer_name: Optional[str] = None) -> Optional[interfaces.objects.ObjectInterface]:
         """Carve an object or data structure from a kernel pool allocation
@@ -34,6 +34,10 @@ class POOL_HEADER(objects.StructType):
             An object as found from a POOL_HEADER
         """
 
+        # TODO: I wasn't quite sure what to do with these values, so I just set them here for now.
+        type_name = constraint.type_name
+        executive = constraint.object_type is not None
+
         symbol_table_name = self.vol.type_name.split(constants.BANG)[0]
         if constants.BANG in type_name:
             symbol_table_name, type_name = type_name.split(constants.BANG)[0:2]
@@ -150,6 +154,10 @@ class POOL_HEADER(objects.StructType):
             # use the bottom up approach for windows 7 and earlier
             else:
                 type_size = self._context.symbol_space.get_type(symbol_table_name + constants.BANG + type_name).size
+                if constraint.additional_structures:
+                    for additional_structure in constraint.additional_structures:
+                        type_size += self._context.symbol_space.get_type(symbol_table_name + constants.BANG + additional_structure).size
+
                 rounded_size = conversion.round(type_size, alignment, up = True)
 
                 mem_object = self._context.object(symbol_table_name + constants.BANG + type_name,

volatility3/plugins/windows/poolscanner.py

@@ -39,7 +39,8 @@ class PoolConstraint:
                  size: Optional[Tuple[Optional[int], Optional[int]]] = None,
                  index: Optional[Tuple[Optional[int], Optional[int]]] = None,
                  alignment: Optional[int] = 1,
-                 skip_type_test: bool = False) -> None:
+                 skip_type_test: bool = False,
+                 additional_structures: Optional[List[str]] = None) -> None:
         self.tag = tag
         self.type_name = type_name
         self.object_type = object_type
@@ -48,6 +49,7 @@ class PoolConstraint:
         self.index = index
         self.alignment = alignment
         self.skip_type_test = skip_type_test
+        self.additional_structures = additional_structures
 
 
 class PoolHeaderScanner(interfaces.layers.ScannerInterface):
@@ -212,7 +214,8 @@ class PoolScanner(plugins.PluginInterface):
                            type_name = symbol_table + constants.BANG + "_DRIVER_OBJECT",
                            object_type = "Driver",
                            size = (248, None),
-                           page_type = PoolType.PAGED | PoolType.NONPAGED | PoolType.FREE),
+                           page_type = PoolType.PAGED | PoolType.NONPAGED | PoolType.FREE, 
+                           additional_structures = ["_DRIVER_EXTENSION"]),
             # drivers on windows starting with windows 8
             PoolConstraint(b'Driv',
                            type_name = symbol_table + constants.BANG + "_DRIVER_OBJECT",
@@ -291,9 +294,8 @@ class PoolScanner(plugins.PluginInterface):
 
         for constraint, header in cls.pool_scan(context, scan_layer, symbol_table, constraints, alignment = alignment):
 
-            mem_object = header.get_object(type_name = constraint.type_name,
+            mem_object = header.get_object(constraint = constraint,
                                            use_top_down = is_windows_8_or_later,
-                                           executive = constraint.object_type is not None,
                                            native_layer_name = 'primary',
                                            kernel_symbol_table = symbol_table)