diff --git a/volatility3/framework/automagic/linux.py b/volatility3/framework/automagic/linux.py index 52a73f45a..27e07e564 100644 --- a/volatility3/framework/automagic/linux.py +++ b/volatility3/framework/automagic/linux.py @@ -80,14 +80,14 @@ class LinuxIntelStacker(interfaces.automagic.StackerLayerInterface): context, table_name, layer_name, progress_callback=progress_callback ) - layer_class: Type = intel.Intel if "init_top_pgt" in table.symbols: - layer_class = intel.Intel32e + layer_class = intel.LinuxIntel32e dtb_symbol_name = "init_top_pgt" elif "init_level4_pgt" in table.symbols: - layer_class = intel.Intel32e + layer_class = intel.LinuxIntel32e dtb_symbol_name = "init_level4_pgt" else: + layer_class = intel.LinuxIntel dtb_symbol_name = "swapper_pg_dir" dtb = cls.virtual_to_physical_address( diff --git a/volatility3/framework/constants/linux/__init__.py b/volatility3/framework/constants/linux/__init__.py index 7c485d3c3..303c534ed 100644 --- a/volatility3/framework/constants/linux/__init__.py +++ b/volatility3/framework/constants/linux/__init__.py @@ -11,6 +11,14 @@ KERNEL_NAME = "__kernel__" """The value hard coded from the Linux Kernel (hence not extracted from the layer itself)""" +# Translation Layer constants +PAGE_BIT_PRESENT = 0 +PAGE_BIT_PSE = 7 # Page Size Extension: 4 MB (or 2MB) page +PAGE_BIT_PROTNONE = 8 +PAGE_BIT_PAT_LARGE = 12 # 2MB or 1GB pages +PAGE_PRESENT = 1 << PAGE_BIT_PRESENT +PAGE_PROTNONE = 1 << PAGE_BIT_PROTNONE + # include/linux/sched.h PF_KTHREAD = 0x00200000 # I'm a kernel thread diff --git a/volatility3/framework/layers/intel.py b/volatility3/framework/layers/intel.py index 33d5432cc..e6d20d992 100644 --- a/volatility3/framework/layers/intel.py +++ b/volatility3/framework/layers/intel.py @@ -13,6 +13,7 @@ from volatility3 import classproperty from volatility3.framework import exceptions, interfaces, constants from volatility3.framework.configuration import requirements from volatility3.framework.layers import linear +from volatility3.framework.constants import linux as linux_constants vollog = logging.getLogger(__name__) @@ -163,12 +164,17 @@ class Intel(linear.LinearlyMappedLayer): entry, f"Page Fault at entry {hex(entry)} in page entry", ) - page = self._mask(entry, self._maxphyaddr - 1, position + 1) | self._mask( - offset, position, 0 - ) + + pfn = self.pte_pfn(entry) + page_offset = self._mask(offset, position, 0) + page = pfn << self.page_shift | page_offset return page, 1 << (position + 1), self._base_layer + def pte_pfn(self, entry: int) -> int: + """Extracts the page frame number (PFN) from the page table entry (PTE) entry""" + return entry >> self.page_shift + def _translate_entry(self, offset: int) -> Tuple[int, int]: """Translates a specific offset based on paging tables. @@ -203,10 +209,10 @@ class Intel(linear.LinearlyMappedLayer): "Page Fault at entry " + hex(entry) + " in table " + name, ) # Check if we're a large page - if large_page and (entry & (1 << 7)): + if large_page and (entry & (1 << linux_constants.PAGE_BIT_PSE)): # Mask off the PAT bit - if entry & (1 << 12): - entry -= 1 << 12 + if entry & (1 << linux_constants.PAGE_BIT_PAT_LARGE): + entry -= 1 << linux_constants.PAGE_BIT_PAT_LARGE # We're a large page, the rest is finished below # If we want to implement PSE-36, it would need to be done here break @@ -501,3 +507,85 @@ class WindowsIntel32e(WindowsMixin, Intel32e): def _translate(self, offset: int) -> Tuple[int, int, str]: return self._translate_swap(self, offset, self._bits_per_register // 2) + + +class LinuxMixin(Intel): + @functools.cached_property + def register_mask(self) -> int: + return (1 << self._bits_per_register) - 1 + + @functools.cached_property + def physical_mask(self) -> int: + # From kernels 4.18 the physical mask is dynamic: See AMD SME, Intel Multi-Key Total + # Memory Encryption and CONFIG_DYNAMIC_PHYSICAL_MASK: 94d49eb30e854c84d1319095b5dd0405a7da9362 + physical_mask = (1 << self._maxphyaddr) - 1 + # TODO: Come back once SME support is available in the framework + return physical_mask + + @functools.cached_property + def page_mask(self) -> int: + # Note that within the Intel class it's a class method. However, since it uses + # complement operations and we are working in Python, it would be more careful to + # limit it to the architecture's pointer size. + return ~(self.page_size - 1) & self.register_mask + + @functools.cached_property + def physical_page_mask(self) -> int: + return self.page_mask & self.physical_mask + + @functools.cached_property + def pte_pfn_mask(self) -> int: + return self.physical_page_mask + + @functools.cached_property + def pte_flags_mask(self) -> int: + return ~self.pte_pfn_mask & self.register_mask + + def pte_flags(self, pte) -> int: + return pte & self.pte_flags_mask + + def is_pte_present(self, entry: int) -> bool: + return ( + self.pte_flags(entry) + & (linux_constants.PAGE_PRESENT | linux_constants.PAGE_PROTNONE) + ) != 0 + + def _page_is_valid(self, entry: int) -> bool: + # Overrides the Intel static method with the Linux-specific implementation + return self.is_pte_present(entry) + + def pte_needs_invert(self, entry) -> bool: + # Entries that were set to PROT_NONE (PAGE_PRESENT/PAGE_GLOBAL) are inverted + return not (entry & linux_constants.PAGE_PRESENT) + + def protnone_mask(self, entry: int) -> int: + """Gets a mask to XOR with the page table entry to get the correct PFN""" + return ~0 & self.register_mask if self.pte_needs_invert(entry) else 0 + + def pte_pfn(self, entry: int) -> int: + """Extracts the page frame number from the page table entry""" + pfn = entry ^ self.protnone_mask(entry) + return (pfn & self.pte_pfn_mask) >> self.page_shift + + +class LinuxIntel(LinuxMixin, Intel): + pass + + +class LinuxIntelPAE(LinuxMixin, IntelPAE): + pass + + +class LinuxIntel32e(LinuxMixin, Intel32e): + # In the Linux kernel, the __PHYSICAL_MASK_SHIFT is a mask used to extract the + # physical address from a PTE. In Volatility3, this is referred to as _maxphyaddr. + # + # Until kernel version 4.17, Linux x86-64 used a 46-bit mask. With commit + # b83ce5ee91471d19c403ff91227204fb37c95fb2, this was extended to 52 bits, + # applying to both 4 and 5-level page tables. + # + # We initially used 52 bits for all Intel 64-bit systems, but this produced incorrect + # results for PROT_NONE pages. Since the mask value is defined by a preprocessor macro, + # it's difficult to detect the exact bit shift used in the current kernel. + # Using 46 bits has proven reliable for our use case, as seen in tools like crashtool. + _maxphyaddr = 46