# 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
from typing import Iterable, Tuple, List

from volatility.framework import interfaces, renderers
from volatility.framework.configuration import requirements
from volatility.framework.interfaces import plugins
from volatility.framework.layers import resources
from volatility.framework.renderers import format_hints

vollog = logging.getLogger(__name__)

try:
    import yara
except ImportError:
    vollog.info("Python Yara module not found, plugin (and dependent plugins) not available")
    raise


class YaraScanner(interfaces.layers.ScannerInterface):

    # yara.Rules isn't exposed, so we can't type this properly
    def __init__(self, rules) -> None:
        super().__init__()
        self._rules = rules

    def __call__(self, data: bytes, data_offset: int) -> Iterable[Tuple[int, str]]:
        for match in self._rules.match(data = data):
            for offset, name, value in match.strings:
                yield (offset + data_offset, name)


class YaraScan(plugins.PluginInterface):
    """Scans kernel memory using yara rules (string or file)."""

    @classmethod
    def get_requirements(cls) -> List[interfaces.configuration.RequirementInterface]:
        return [
            requirements.TranslationLayerRequirement(name = 'primary',
                                                     description = "Memory layer for the kernel",
                                                     architectures = ["Intel32", "Intel64"]),
            requirements.BooleanRequirement(name = "insensitive",
                                            description = "Makes the search case insensitive",
                                            default = False,
                                            optional = True),
            requirements.BooleanRequirement(name = "wide",
                                            description = "Match wide (unicode) strings",
                                            default = False,
                                            optional = True),
            requirements.StringRequirement(name = "yara_rules",
                                           description = "Yara rules (as a string)",
                                           optional = True),
            requirements.URIRequirement(name = "yara_file", description = "Yara rules (as a file)", optional = True),
            requirements.IntRequirement(name = "max_size",
                                        default = 0x40000000,
                                        description = "Set the maximum size (default is 1GB)",
                                        optional = True)
        ]

    def _generator(self):

        layer = self.context.layers[self.config['primary']]
        rules = None
        if self.config.get('yara_rules', None) is not None:
            rule = self.config['yara_rules']
            if rule[0] not in ["{", "/"]:
                rule = '"{}"'.format(rule)
            if self.config.get('case', False):
                rule += " nocase"
            if self.config.get('wide', False):
                rule += " wide ascii"
            rules = yara.compile(sources = {'n': 'rule r1 {{strings: $a = {} condition: $a}}'.format(rule)})
        elif self.config.get('yara_file', None) is not None:
            rules = yara.compile(file = resources.ResourceAccessor().open(self.config['yara_file'], "rb"))
        else:
            vollog.error("No yara rules, nor yara rules file were specified")

        for offset, name in layer.scan(context = self.context, scanner = YaraScanner(rules = rules)):
            yield (0, (format_hints.Hex(offset), name))

    def run(self):
        return renderers.TreeGrid([('Offset', format_hints.Hex), ('Rule', str)], self._generator())