Linux: hidden_modules: Add docstrings and comments to enhance the documentation of the module verification process. Move the hardcoded values to the linux constants file.

Author: gcmoreira

volatility3/framework/constants/linux/__init__.py

@@ -339,3 +339,11 @@ class PT_FLAGS(Flag):
     def flags(self) -> str:
         """Returns the ptrace flags string"""
         return str(self).replace(self.__class__.__name__ + ".", "")
+
+
+# Valid sizes for modules. Note that the Linux kernel does not define these values; they
+# are based on empirical observations of typical memory allocations for kernel modules.
+# We use this to verify that the found module falls within reasonable limits.
+MODULE_MAXIMUM_CORE_SIZE = 20000000
+MODULE_MAXIMUM_CORE_TEXT_SIZE = 20000000
+MODULE_MINIMUM_SIZE = 4096

volatility3/framework/symbols/linux/extensions/__init__.py

@@ -13,12 +13,24 @@
 
 from volatility3.framework import constants, exceptions, objects, interfaces, symbols
 from volatility3.framework.renderers import conversion
-from volatility3.framework.constants.linux import SOCK_TYPES, SOCK_FAMILY
-from volatility3.framework.constants.linux import IP_PROTOCOLS, IPV6_PROTOCOLS
-from volatility3.framework.constants.linux import TCP_STATES, NETLINK_PROTOCOLS
-from volatility3.framework.constants.linux import ETH_PROTOCOLS, BLUETOOTH_STATES
-from volatility3.framework.constants.linux import BLUETOOTH_PROTOCOLS, SOCKET_STATES
-from volatility3.framework.constants.linux import CAPABILITIES, PT_FLAGS
+from volatility3.framework.constants.linux import (
+    SOCK_TYPES,
+    SOCK_FAMILY,
+    IP_PROTOCOLS,
+    IPV6_PROTOCOLS,
+    TCP_STATES,
+    NETLINK_PROTOCOLS,
+    ETH_PROTOCOLS,
+    BLUETOOTH_STATES,
+    BLUETOOTH_PROTOCOLS,
+    SOCKET_STATES,
+    CAPABILITIES,
+    PT_FLAGS,
+    MODULE_MAXIMUM_CORE_SIZE,
+    MODULE_MAXIMUM_CORE_TEXT_SIZE,
+    MODULE_MINIMUM_SIZE,
+)
+
 from volatility3.framework.layers import linear
 from volatility3.framework.objects import utility
 from volatility3.framework.symbols import generic, linux, intermed
@@ -36,16 +48,23 @@ def __init__(self, *args, **kwargs):
         self._mod_mem_type = None  # Initialize _mod_mem_type to None for memoization
 
     def is_valid(self):
+        """Determine whether it is a valid module object by verifying the self-referential
+        in module_kobject. This also confirms that the module is actively allocated and
+        not a remnant of freed memory or a failed module load attempt by verifying the
+        module memory section sizes.
+        """
         layer = self._context.layers[self.vol.layer_name]
         # Make sure the entire module content is readable
         if not layer.is_valid(self.vol.offset, self.vol.size):
             return False
 
         core_size = self.get_core_size()
+        core_text_size = self.get_core_text_size()
+        init_size = self.get_init_size()
         if not (
-            1 <= core_size <= 20000000
-            and core_size + self.get_init_size() >= 4096
-            and 1 <= self.get_core_text_size() <= 20000000
+            0 < core_text_size <= MODULE_MAXIMUM_CORE_TEXT_SIZE
+            and 0 < core_size <= MODULE_MAXIMUM_CORE_SIZE
+            and core_size + init_size >= MODULE_MINIMUM_SIZE
         ):
             return False