# Volatility
# Copyright (C) 2018 Volatility Foundation
#
# Authors:
# awalters@4tphi.net (AAron Walters)
#
# This file is part of Volatility 3.

import struct
import typing

from volatility.framework import constants, exceptions, interfaces, validity
from volatility.framework.layers import segmented
from volatility.framework.symbols import intermed


class WindowsCrashDump32FormatException(exceptions.LayerException):
    """Thrown when an error occurs with the underlying Crash file format"""


class WindowsCrashDump32Layer(segmented.SegmentedLayer):
    """A Windows crash format TranslationLayer. This TranslationLayer supports 
    Microsoft complete memory dump files. It currently does not support
    kernel or small memory dump files."""

    provides = {"type": "physical"}
    priority = 23

    SIGNATURE = 0x45474150
    VALIDDUMP = 0x504d5544
    _magic_struct = struct.Struct('<II')
    headerpages = 1

    def __init__(self,
                 context: interfaces.context.ContextInterface,
                 config_path: str,
                 name: str) -> None:

        # Construct these so we can use self.config
        self._context = context
        self._config_path = config_path
        self._page_size = 0x1000
        self._base_layer = self.config["base_layer"]

        # Create a custom SymbolSpace
        self._crash_table_name = intermed.IntermediateSymbolTable.create(context,
                                                                         self._config_path,
                                                                         'windows',
                                                                         'crash')
        # Check Header
        hdr_layer = self._context.memory[self._base_layer]
        hdr_offset = 0
        self._check_header(hdr_layer, hdr_offset)

        # Need to create a header object
        self.header = self.context.object(self._crash_table_name + constants.BANG +
                                          "_DMP_HEADER", offset = hdr_offset,
                                          layer_name = self._base_layer)

        # Extract the DTB
        self.dtb = self.header.DirectoryTableBase

        # Verify that it is a supported format
        if self.header.DumpType != 0x1:
            raise WindowsCrashDump32FormatException("unsupported dump format 0x{:x}".format(self.header.DumpType))

        super().__init__(context, config_path, name)

    def _load_segments(self) -> None:
        """Loads up the segments from the meta_layer"""

        segments = []

        offset = self.headerpages
        for x in self.header.PhysicalMemoryBlockBuffer.Run:
            segments.append((x.BasePage * 0x1000,
                             offset * 0x1000,
                             x.PageCount * 0x1000))
            # print("Segments {:x} {:x} {:x}".format(x.BasePage * 0x1000,
            #                  offset * 0x1000,
            #                  x.PageCount * 0x1000)) 
            offset += x.PageCount

        if len(segments) == 0:
            raise WindowsCrashDump32FormatException("No Crash segments defined in {}".format(self._base_layer))

        self._segments = segments

    @classmethod
    def _check_header(cls,
                      base_layer: interfaces.layers.DataLayerInterface,
                      offset: int = 0) -> typing.Tuple[int, int]:

        # Verify the Window's crash dump file magic
        header_data = base_layer.read(offset, cls._magic_struct.size)
        (signature, validdump) = cls._magic_struct.unpack(header_data)

        if signature != cls.SIGNATURE:
            raise WindowsCrashDump32FormatException(
                "bad signature 0x{:x} at file offset 0x{:x}".format(signature, offset))
        if validdump != cls.VALIDDUMP:
            raise WindowsCrashDump32FormatException(
                "invalid dump 0x{:x} at file offset 0x{:x}".format(validdump, offset))

        return (signature, validdump)


class WindowsCrashDump32Stacker(interfaces.automagic.StackerLayerInterface):
    stack_order = 11

    @classmethod
    def stack(cls,
              context: interfaces.context.ContextInterface,
              layer_name: str,
              progress_callback: validity.ProgressCallback = None) \
            -> typing.Optional[interfaces.layers.DataLayerInterface]:
        try:
            WindowsCrashDump32Layer._check_header(context.memory[layer_name])
        except WindowsCrashDump32FormatException:
            return None
        new_name = context.memory.free_layer_name("WindowsCrashDump32Layer")
        context.config[interfaces.configuration.path_join(new_name, "base_layer")] = layer_name
        return WindowsCrashDump32Layer(context, new_name, new_name)