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87 lines
4.0 KiB
Python
87 lines
4.0 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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import logging
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import struct
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from typing import Optional
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from volatility.framework import exceptions, interfaces, constants
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from volatility.framework.layers import segmented
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from volatility.framework.symbols import intermed
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vollog = logging.getLogger(__name__)
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class ElfFormatException(exceptions.LayerException):
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"""Thrown when an error occurs with the underlying ELF file format."""
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class Elf64Layer(segmented.SegmentedLayer):
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"""A layer that supports the Elf64 format as documented at: http://ftp.openwatcom.org/devel/docs/elf-64-gen.pdf"""
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_header_struct = struct.Struct("<IBBB")
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MAGIC = 0x464c457f # "\x7fELF"
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ELF_CLASS = 2
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def __init__(self, context: interfaces.context.ContextInterface, config_path: str, name: str) -> None:
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# Create a custom SymbolSpace
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self._elf_table_name = intermed.IntermediateSymbolTable.create(context, config_path, 'linux', 'elf')
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super().__init__(context, config_path, name)
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def _load_segments(self) -> None:
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"""Load the segments from based on the PT_LOAD segments of the Elf64 format"""
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ehdr = self.context.object(self._elf_table_name + constants.BANG + "Elf64_Ehdr",
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layer_name = self._base_layer,
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offset = 0)
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segments = []
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for pindex in range(ehdr.e_phnum):
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phdr = self.context.object(self._elf_table_name + constants.BANG + "Elf64_Phdr",
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layer_name = self._base_layer,
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offset = ehdr.e_phoff + (pindex * ehdr.e_phentsize))
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# We only want PT_TYPES with valid sizes
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if phdr.p_type.lookup() == "PT_LOAD" and phdr.p_filesz == phdr.p_memsz and phdr.p_filesz > 0:
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# Cast these to ints to ensure the offsets don't need reconstructing
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segments.append((int(phdr.p_paddr), int(phdr.p_offset), int(phdr.p_memsz)))
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if len(segments) == 0:
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raise ElfFormatException(self.name, "No ELF segments defined in {}".format(self._base_layer))
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self._segments = segments
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@classmethod
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def _check_header(cls, base_layer: interfaces.layers.DataLayerInterface, offset: int = 0) -> bool:
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try:
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header_data = base_layer.read(offset, cls._header_struct.size)
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except exceptions.InvalidAddressException:
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raise ElfFormatException(base_layer.name,
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"Offset 0x{:0x} does not exist within the base layer".format(offset))
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(magic, elf_class, elf_data_encoding, elf_version) = cls._header_struct.unpack(header_data)
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if magic != cls.MAGIC:
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raise ElfFormatException(base_layer.name, "Bad magic 0x{:x} at file offset 0x{:x}".format(magic, offset))
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if elf_class != cls.ELF_CLASS:
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raise ElfFormatException(base_layer.name, "ELF class is not 64-bit (2): {:d}".format(elf_class))
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# Virtualbox uses an ELF version of 0, which isn't to specification, but is ok to deal with
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return True
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class Elf64Stacker(interfaces.automagic.StackerLayerInterface):
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stack_order = 10
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@classmethod
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def stack(cls,
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context: interfaces.context.ContextInterface,
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layer_name: str,
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progress_callback: constants.ProgressCallback = None) -> Optional[interfaces.layers.DataLayerInterface]:
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try:
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if not Elf64Layer._check_header(context.layers[layer_name]):
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return None
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except ElfFormatException as excp:
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vollog.log(constants.LOGLEVEL_VVVV, "Exception: {}".format(excp))
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return None
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new_name = context.layers.free_layer_name("Elf64Layer")
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context.config[interfaces.configuration.path_join(new_name, "base_layer")] = layer_name
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return Elf64Layer(context, new_name, new_name)
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