# This file is Copyright 2019 Volatility Foundation and licensed under the Volatility Software License 1.0
# which is available at https://www.volatilityfoundation.org/license/vsl-v1.0
#

import logging
import struct
from typing import Optional

from volatility3.framework import constants, exceptions, interfaces, layers
from volatility3.framework.automagic import symbol_cache, symbol_finder
from volatility3.framework.layers import intel, scanners
from volatility3.framework.symbols import mac

vollog = logging.getLogger(__name__)


class MacIntelStacker(interfaces.automagic.StackerLayerInterface):
    stack_order = 35
    exclusion_list = ["windows", "linux"]

    @classmethod
    def stack(
        cls,
        context: interfaces.context.ContextInterface,
        layer_name: str,
        progress_callback: constants.ProgressCallback = None,
    ) -> Optional[interfaces.layers.DataLayerInterface]:
        """Attempts to identify mac within this layer."""
        # Bail out by default unless we can stack properly
        layer = context.layers[layer_name]
        new_layer = None
        join = interfaces.configuration.path_join

        # Never stack on top of an intel layer
        # FIXME: Find a way to improve this check
        if isinstance(layer, intel.Intel):
            return None

        mac_banners = symbol_cache.load_cache_manager().get_identifier_dictionary(
            operating_system="mac"
        )
        # If we have no banners, don't bother scanning
        if not mac_banners:
            vollog.info(
                "No Mac banners found - if this is a mac plugin, please check your symbol files location"
            )
            return None

        mss = scanners.MultiStringScanner([x for x in mac_banners if x])
        for banner_offset, banner in layer.scan(
            context=context, scanner=mss, progress_callback=progress_callback
        ):
            dtb = None
            vollog.debug(f"Identified banner: {repr(banner)}")

            isf_path = mac_banners.get(banner, None)
            if isf_path:
                table_name = context.symbol_space.free_table_name("MacintelStacker")
                table = mac.MacKernelIntermedSymbols(
                    context=context,
                    config_path=join("temporary", table_name),
                    name=table_name,
                    isf_url=isf_path,
                )
                context.symbol_space.append(table)
                kaslr_shift = cls.find_aslr(
                    context=context,
                    symbol_table=table_name,
                    layer_name=layer_name,
                    compare_banner=banner,
                    compare_banner_offset=banner_offset,
                    progress_callback=progress_callback,
                )

                if kaslr_shift == 0:
                    vollog.log(
                        constants.LOGLEVEL_VVV,
                        f"Invalid kalsr_shift found at offset: {banner_offset}",
                    )
                    continue

                bootpml4_addr = cls.virtual_to_physical_address(
                    table.get_symbol("BootPML4").address + kaslr_shift
                )

                new_layer_name = context.layers.free_layer_name("MacDTBTempLayer")
                config_path = join("automagic", "MacIntelHelper", new_layer_name)
                context.config[join(config_path, "memory_layer")] = layer_name
                context.config[join(config_path, "page_map_offset")] = bootpml4_addr

                layer = layers.intel.Intel32e(
                    context,
                    config_path=config_path,
                    name=new_layer_name,
                    metadata={"os": "Mac"},
                )

                idlepml4_ptr = table.get_symbol("IdlePML4").address + kaslr_shift
                try:
                    idlepml4_str = layer.read(idlepml4_ptr, 4)
                except exceptions.InvalidAddressException:
                    vollog.log(
                        constants.LOGLEVEL_VVVV,
                        f"Skipping invalid idlepml4_ptr: 0x{idlepml4_ptr:0x}",
                    )
                    continue

                idlepml4_addr = struct.unpack("<I", idlepml4_str)[0]

                tmp_dtb = idlepml4_addr

                if tmp_dtb % 4096:
                    vollog.log(
                        constants.LOGLEVEL_VVV,
                        f"Skipping non-page aligned DTB: 0x{tmp_dtb:0x}",
                    )
                    continue

                dtb = tmp_dtb

                # Build the new layer
                new_layer_name = context.layers.free_layer_name("IntelLayer")
                config_path = join("automagic", "MacIntelHelper", new_layer_name)
                context.config[join(config_path, "memory_layer")] = layer_name
                context.config[join(config_path, "page_map_offset")] = dtb
                context.config[join(config_path, MacSymbolFinder.banner_config_key)] = (
                    str(banner, "latin-1")
                )

                new_layer = intel.Intel32e(
                    context,
                    config_path=config_path,
                    name=new_layer_name,
                    metadata={"os": "mac"},
                )
                new_layer.config["kernel_virtual_offset"] = kaslr_shift

            if new_layer and dtb:
                vollog.debug(f"DTB was found at: 0x{dtb:0x}")
                return new_layer
        vollog.debug("No suitable mac banner could be matched")
        return None

    @classmethod
    def find_aslr(
        cls,
        context: interfaces.context.ContextInterface,
        symbol_table: str,
        layer_name: str,
        compare_banner: str = "",
        compare_banner_offset: int = 0,
        progress_callback: constants.ProgressCallback = None,
    ) -> int:
        """Determines the offset of the actual DTB in physical space and its
        symbol offset."""
        version_symbol = symbol_table + constants.BANG + "version"
        version_json_address = context.symbol_space.get_symbol(version_symbol).address

        version_major_symbol = symbol_table + constants.BANG + "version_major"
        version_major_json_address = context.symbol_space.get_symbol(
            version_major_symbol
        ).address
        version_major_phys_offset = cls.virtual_to_physical_address(
            version_major_json_address
        )

        version_minor_symbol = symbol_table + constants.BANG + "version_minor"
        version_minor_json_address = context.symbol_space.get_symbol(
            version_minor_symbol
        ).address
        version_minor_phys_offset = cls.virtual_to_physical_address(
            version_minor_json_address
        )

        if not compare_banner_offset or not compare_banner:
            offset_generator = cls._scan_generator(
                context, layer_name, progress_callback
            )
        else:
            offset_generator = [(compare_banner_offset, compare_banner)]

        aslr_shift = 0

        for offset, banner in offset_generator:
            banner_major, banner_minor = (int(x) for x in banner[22:].split(b".")[0:2])

            tmp_aslr_shift = offset - cls.virtual_to_physical_address(
                version_json_address
            )

            major_string = context.layers[layer_name].read(
                version_major_phys_offset + tmp_aslr_shift, 4
            )
            major = struct.unpack("<I", major_string)[0]

            if major != banner_major:
                continue

            minor_string = context.layers[layer_name].read(
                version_minor_phys_offset + tmp_aslr_shift, 4
            )
            minor = struct.unpack("<I", minor_string)[0]

            if minor != banner_minor:
                continue

            if tmp_aslr_shift & 0xFFF != 0:
                continue

            aslr_shift = tmp_aslr_shift & 0xFFFFFFFF
            break

        vollog.log(constants.LOGLEVEL_VVVV, f"Mac find_aslr returned: {aslr_shift:0x}")

        return aslr_shift

    @classmethod
    def virtual_to_physical_address(cls, addr: int) -> int:
        """Converts a virtual mac address to a physical one (does not account
        of ASLR)"""
        if addr > 0xFFFFFF8000000000:
            addr = addr - 0xFFFFFF8000000000
        else:
            addr = addr - 0xFF8000000000

        return addr

    @classmethod
    def _scan_generator(cls, context, layer_name, progress_callback):
        darwin_signature = (
            rb"Darwin Kernel Version \d{1,3}\.\d{1,3}\.\d{1,3}: [^\x00]+\x00"
        )

        for offset in context.layers[layer_name].scan(
            scanner=scanners.RegExScanner(darwin_signature),
            context=context,
            progress_callback=progress_callback,
        ):
            banner = context.layers[layer_name].read(offset, 128)

            idx = banner.find(b"\x00")
            if idx != -1:
                banner = banner[:idx]

            yield offset, banner


class MacSymbolFinder(symbol_finder.SymbolFinder):
    """Mac symbol loader based on uname signature strings."""

    banner_config_key = "kernel_banner"
    operating_system = "mac"
    find_aslr = MacIntelStacker.find_aslr
    symbol_class = "volatility3.framework.symbols.mac.MacKernelIntermedSymbols"
    exclusion_list = ["windows", "linux"]
