volatility3/volatility3/framework/plugins/windows/strings.py

# 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 re
from typing import Dict, Generator, List, Set, Tuple, Optional

from volatility3.framework import interfaces, renderers, exceptions, constants
from volatility3.framework.configuration import requirements
from volatility3.framework.layers import intel, resources, linear
from volatility3.framework.renderers import format_hints
from volatility3.plugins.windows import pslist

vollog = logging.getLogger(__name__)


class Strings(interfaces.plugins.PluginInterface):
    """Reads output from the strings command and indicates which process(es) each string belongs to."""

    _required_framework_version = (2, 0, 0)

    # 2.0.0 - change signature of `generate_mapping`
    _version = (2, 0, 0)

    strings_pattern = re.compile(rb"^(?:\W*)([0-9]+)(?:\W*)(\w[\w\W]+)\n?")

    @classmethod
    def get_requirements(cls) -> List[interfaces.configuration.RequirementInterface]:
        return [
            requirements.ModuleRequirement(
                name="kernel",
                description="Windows kernel",
                architectures=["Intel32", "Intel64"],
            ),
            requirements.PluginRequirement(
                name="pslist", plugin=pslist.PsList, version=(3, 0, 0)
            ),
            requirements.ListRequirement(
                name="pid",
                element_type=int,
                description="Process ID to include (all other processes are excluded)",
                optional=True,
            ),
            requirements.URIRequirement(
                name="strings_file", description="Strings file"
            ),
        ]
        # TODO: Make URLRequirement that can accept a file address which the framework can open

    def run(self):
        return renderers.TreeGrid(
            [("String", str), ("Physical Address", format_hints.Hex), ("Result", str)],
            self._generator(),
        )

    def _generator(self) -> Generator[Tuple, None, None]:
        """Generates results from a strings file."""
        string_list: List[Tuple[int, bytes]] = []

        # Test strings file format is accurate
        accessor = resources.ResourceAccessor()
        strings_fp = accessor.open(self.config["strings_file"], "rb")
        line = strings_fp.readline()
        count: float = 0
        while line:
            count += 1
            try:
                offset, string = self._parse_line(line)
                string_list.append((offset, string))
            except ValueError:
                vollog.error(f"Line in unrecognized format: line {count}")
            line = strings_fp.readline()

        revmap = self.generate_mapping(
            context=self.context,
            kernel_module_name=self.config["kernel"],
            progress_callback=self._progress_callback,
            pid_list=self.config["pid"],
        )

        last_prog: float = 0
        line_count: float = 0
        num_strings = len(string_list)
        for offset, string in string_list:
            line_count += 1
            try:
                revmap_list = [
                    name + ":" + hex(offset) for (name, offset) in revmap[offset >> 12]
                ]
            except (IndexError, KeyError):
                revmap_list = ["FREE MEMORY"]
            yield (
                0,
                (
                    str(string, "latin-1"),
                    format_hints.Hex(offset),
                    ", ".join(revmap_list),
                ),
            )
            prog = line_count / num_strings * 100
            if round(prog, 1) > last_prog:
                last_prog = round(prog, 1)
                self._progress_callback(prog, "Matching strings in memory")

    def _parse_line(self, line: bytes) -> Tuple[int, bytes]:
        """Parses a single line from a strings file.

        Args:
            line: bytes of the line of a strings file (an offset and a string)

        Returns:
            Tuple of the offset and the string found at that offset
        """

        match = self.strings_pattern.search(line)
        if not match:
            raise ValueError("Strings file contains invalid strings line")
        offset, string = match.group(1, 2)
        return int(offset), string

    @classmethod
    def generate_mapping(
        cls,
        context: interfaces.context.ContextInterface,
        kernel_module_name: str,
        progress_callback: constants.ProgressCallback = None,
        pid_list: Optional[List[int]] = None,
    ) -> Dict[int, Set[Tuple[str, int]]]:
        """Creates a reverse mapping between virtual addresses and physical
        addresses.

        Args:
            context: the context for the method to run against
            kernel_module_name: the name of the module forthe kernel
            progress_callback: an optional callable to display progress
            pid_list: a lit of process IDs to consider when generating the reverse map

        Returns:
            A mapping of virtual offsets to strings and physical offsets
        """
        filter = pslist.PsList.create_pid_filter(pid_list)

        kernel = context.modules[kernel_module_name]

        layer = context.layers[kernel.layer_name]
        reverse_map: Dict[int, Set[Tuple[str, int]]] = dict()
        if isinstance(layer, intel.Intel):
            # We don't care about errors, we just wanted chunks that map correctly
            for mapval in layer.mapping(0x0, layer.maximum_address, ignore_errors=True):
                offset, _, mapped_offset, mapped_size, maplayer = mapval
                for val in range(mapped_offset, mapped_offset + mapped_size, 0x1000):
                    cur_set = reverse_map.get(val >> 12, set())
                    cur_set.add(("kernel", offset))
                    reverse_map[val >> 12] = cur_set
                if progress_callback:
                    progress_callback(
                        (offset * 100) / layer.maximum_address,
                        "Creating reverse kernel map",
                    )

            # TODO: Include kernel modules

            for process in pslist.PsList.list_processes(
                context=context, kernel_module_name=kernel_module_name
            ):
                if not filter(process):
                    proc_id = "Unknown"
                    try:
                        proc_id = process.UniqueProcessId
                        proc_layer_name = process.add_process_layer()
                    except exceptions.InvalidAddressException as excp:
                        vollog.debug(
                            f"Process {proc_id}: invalid address {excp.invalid_address} in layer {excp.layer_name}"
                        )
                        continue

                    proc_layer = context.layers[proc_layer_name]
                    if isinstance(proc_layer, linear.LinearlyMappedLayer):
                        for mapval in proc_layer.mapping(
                            0x0, proc_layer.maximum_address, ignore_errors=True
                        ):
                            mapped_offset, _, offset, mapped_size, _maplayer = mapval
                            for val in range(
                                mapped_offset, mapped_offset + mapped_size, 0x1000
                            ):
                                cur_set = reverse_map.get(mapped_offset >> 12, set())
                                cur_set.add(
                                    (f"Process {process.UniqueProcessId}", offset)
                                )
                                reverse_map[mapped_offset >> 12] = cur_set
                            # FIXME: make the progress for all processes, rather than per-process
                            if progress_callback:
                                progress_callback(
                                    (offset * 100) / layer.maximum_address,
                                    f"Creating mapping for task {process.UniqueProcessId}",
                                )

        return reverse_map