evtx2json.py

"""
Script to convert evtx_dump.py XML output (https://github.com/williballenthin/python-evtx)
to JSON and optionally, push events to Splunk via HTTP Event Collector (pip install splunk-hec-handler)

Process file(s)
    evtx2json.py process_files --files file1.evtx file2.evtx folder/*.evtx

Process folder
    evtx2json.py process_folder --folder evtx_folder

Enable logging to Splunk
    evtx2json.py --splunk --host splunkfw.domain.tld --port 8888 --token BEA33046C-6FEC-4DC0-AC66-4326E58B54C3 \
        process_files -f samples/*.evtx

Enable logging to Splunk but disable JSON modifications
    evtx2json.py --splunk --host splunkfw.domain.tld --port 8888 --token BEA33046C-6FEC-4DC0-AC66-4326E58B54C3 \
        --disable_json_tweaks process_files -f samples/*.evtx

"""
import os.path
import sys
import logging
from xmljson import badgerfish as bf
import json
import xml.etree.ElementTree as ET
import Evtx.Evtx as evtx
import time
from glob import glob
import argparse

logger = logging.getLogger('evtx2json')
logger.setLevel(logging.DEBUG)

stream_handler = logging.StreamHandler()
stream_handler.level = logging.INFO
formatter = logging.Formatter(fmt='%(asctime)s [%(name)10s] %(levelname)s %(message)s', datefmt='%m/%d/%y %I:%M:%S %p')
stream_handler.formatter = formatter
logger.addHandler(stream_handler)

# Additional fields for Splunk indexing
fields = dict({})

global event_counter, error_counter


def add_splunk_handler(args):
    """
    Add remote Splunk HEC logging handler to logger
    :param args:  argparse Namespace containing values to configure Splunk handler.  Host and Token required.
    :return: None.  Adds splunk log handler to loger.
    """
    if args.splunk:
        try:
            from splunk_hec_handler import SplunkHecHandler
        except ModuleNotFoundError as err:
            logger.warning("Filed to import 'splunk_hec_handler' python module.  Try 'pip install splunk_hec_handler'")
            pass
        except Exception as err:
            logger.warning("Error encountered adding Splunk logging handler.  Error: %s" % err)
            pass
        else:
            if not args.verify:
                try:
                    import urllib3
                    urllib3.disable_warnings(urllib3.exceptions.InsecureRequestWarning)
                except ModuleNotFoundError as err:
                    logger.debug("Failed to suppress SSL warnings")

            logger.debug("Configuring Splunk handler: host: %s, port: %d, proto: %s, ssl_veriy: %s, token: %s, source: %s, sourcetype: %s"
                         % (args.host, args.port, args.proto, args.verify, args.token, args.source, args.sourcetype))

            splunk_handler = SplunkHecHandler(args.host,
                                              args.token, index=args.index,
                                              port=args.port, proto=args.proto, ssl_verify=args.verify,
                                              source=args.source, sourcetype=args.sourcetype)
            splunk_handler.setLevel(logging.getLevelName(args.loglevel))
            logger.addHandler(splunk_handler)


def remove_namespace(tree):
    """
    Namespace can make Splunk output ugly.  This function removes namespace from all elements
    e.g element.tag = '{http://schemas.microsoft.com/win/2004/08/events/event}System'
    :param tree: xml ElementTree Element
    :return: xml ElementTree Element with namespace removed
    """
    # Remove namespace
    for element in tree.getiterator():
        try:
            if element.tag.startswith('{'):
                element.tag = element.tag.split('}')[1]
        except:
            pass

    return tree


def xml2json(xml_str):
    """
    Convert string xml (after striping namespace) output from evtx.Evtx to XML tree object
    :param xml_str: string
    :return: xml ElementTree Element
    """
    try:
        tree = remove_namespace(ET.fromstring(str(xml_str)))
        obj = bf.data(tree)
    except:
        logger.error("Failed to convert XML to JSON for %s" % xml_str)
    else:
        return obj


def iter_evtx2xml(evtx_file):
    """
    Generator function to read events from evtx file and convert to xml
    :param evtx_file: file path string
    :return: generator to xml string representation of evtx event
    """
    global error_counter, event_counter
    error_counter = 0
    event_counter = 0
    try:
        with evtx.Evtx(evtx_file) as log:
            # process each log entry and return xml representation
            for record in log.records():
                event_counter += 1
                try:
                    yield record.xml()
                except Exception as err:
                    error_counter += 1
                    logger.error("Failed to convert EVTX to XML for %s. Error count: %d" % (evtx_file, error_counter))
    except Exception as err:
        raise


def _transform_system(output):
    # xmljson output of System field is rather unruly Event{System{1{}...n{}}}
    # This function cleans up the System section for easier Splunking.
    try:
        systemdata = output['Event']['System']
        new_systemdata = {}
    except KeyError:
        logger.debug('Missing "System" section. Skipping.')
    else:
        for k,v in systemdata.items():
            if hasattr(v, 'items') and len(v) == 1 and '$' in v.keys():
                new_systemdata[k] = v['$']
            else:
                new_systemdata[k] = v

        _ = output['Event'].pop('System')
        output['Event']['System'] = {}
        output['Event']['System'].update(new_systemdata)
    finally:
        return output


def _transform_eventdata(output):
    # xmljson output of EventData field is rather unruly Event{EventData{ Data[1{}...n{}] }}
    # This function cleans up the EventData section for easier Splunking.
    try:
        eventdata = output['Event']['EventData']
    except:
        logger.debug('Missing "EventData" section. Skipping.')
    else:
        new_eventdata = {}
        for data in eventdata['Data']:
            if '@Name' in data.keys() and '$' in data.keys():
                new_eventdata[data['@Name']] = data['$']
            elif '@Name' in data.keys() and '$' not in data.keys():
                new_eventdata[data['@Name']] = None
            else:
                new_eventdata.extend(data)
        _ = output['Event'].pop('EventData')
        output['Event']['EventData'] = {}
        output['Event']['EventData'].update(new_eventdata)
    finally:
        return output


def splunkify(output, source=sys.argv[1]):
    """
    Any customization to the final splunk output goes here
    :param output: JSON obj returned by xml2json
    :param source: str. evtx source
    :return: JSON obj with Splunk customizations
    """

    event = _transform_system(output)
    event = _transform_eventdata(event)

    # Custom fields for Splunk processing
    event['Event']['fields'] = {}

    # Set Splunk event _time to timestamp in the evtx event.
    try:
        _ts = event['Event']['System']['TimeCreated']['@SystemTime']
        try:
            _ts = time.mktime(time.strptime(_ts.strip(), "%Y-%m-%d %H:%M:%S.%f"))
        except ValueError:
            _ts = time.mktime(time.strptime(_ts.strip(), "%Y-%m-%d %H:%M:%S"))
    except KeyError:
        logger.warning("Event missing TimeCreated field")
        _ts = time.time()
    except ValueError:
        logger.warning("Failed to convert TimeCreated (%s) to epoch timestamp" % _ts)
        _ts = time.time()
    else:
        # example evtx timestamp '2016-07-01 11:05:48.162424'
        event['Event']['fields']['time'] = _ts

    # Set host field to Computer names in the evtx event
    try:
        _host = event['Event']['System']['Computer']
    except KeyError:
        logger.warning("Event missing Computer field")
    else:
        event['Event']['fields']['host'] = _host

    # Set source field to name of the evtx file
    event['Event']['fields']['source'] = os.path.basename(source)

    return event


def output_stats(evtx_file, success_counter, start_time):
    """ Log basic stats per evtx file """
    global event_counter, error_counter
    delta_secs = (int(time.time()) - start_time)

    logger.info({'file': evtx_file, 'total_events': event_counter, 'pass': success_counter,
                 'fail': error_counter, 'time': start_time, 'elapsed_sec': delta_secs})


def process_files(args):
    """
    Each evtx file is first converted to xml using python-evtx module
    Next, the xml output is converted to JSON using xmljson (badgerfish)
    Finally, the JSON output is customized, unless --disable_json_tweaks is specified as a flag
    If --splunk flag is specified, events are logged to the specified Splunk host (--host)
    """
    if args.splunk:
        add_splunk_handler(args)

    global error_counter
    start_time = int(time.time())
    for evtx_file in args.files:
        if evtx_file.endswith(".evtx"):
            logger.debug("Now processing %s" % evtx_file)
            success_counter = 0
            for xml_str in iter_evtx2xml(evtx_file):
                try:
                    if args.disable_json_tweaks:
                        output = xml2json(xml_str)
                    else:
                        output = splunkify(xml2json(xml_str), evtx_file)
                except Exception:
                    error_counter += 1
                else:
                    logger.info(json.loads(json.dumps(output['Event'])))
                    success_counter += 1

            output_stats(evtx_file, success_counter, start_time)


def process_folder(args):
    files = glob(os.path.join(args.folder, "*.evtx"))
    args.__setattr__('files', files)
    process_files(args)

if __name__ == "__main__":
    parser = argparse.ArgumentParser(add_help=False, description="Convert Windows evtx files to JSON")
    parser.add_argument('--help', '-h', help="This help message.", action='help')
    parser.add_argument('--loglevel', '-v', help="Log level", choices=[0, 10, 20, 30, 40, 50], default=20, type=int)
    parser.add_argument('--disable_json_tweaks', help="Skip customization to time, host, source etc. json fields",
                        required=False, default=False, action='store_true')
    subparsers = parser.add_subparsers()

    splunk_parser_group = parser.add_argument_group(title="Splunk Integration", description="Send JSON output to Splunk")
    splunk_parser_group.add_argument('--splunk', help="Send JSON output to Splunk",
                                     required=False, default=False, action='store_true')
    splunk_parser_group.add_argument('--host', help="Splunk host with HEC listener", default="localhost")
    splunk_parser_group.add_argument('--token', help="HEC Token")
    splunk_parser_group.add_argument('--port', help="Splunk HEC listener port", type=int, required=False, default=8008)
    splunk_parser_group.add_argument('--proto', help="Splunk HEC protocol", default='https', required=False, choices=['http', 'https'])
    splunk_parser_group.add_argument('--index', help="Splunk Index", required=False)
    splunk_parser_group.add_argument('--source', help="Event Source.  NOTE: Computer name in evtx will overwrite this value", default=os.path.basename(sys.argv[0]), required=False)
    splunk_parser_group.add_argument('--sourcetype', help="Event Sourcetype", default='_json', required=False)
    splunk_parser_group.add_argument('--verify', help="SSL certificate verification", default=False, required=False, action='store_true')

    # Parser for single evtx file
    parser_fh = subparsers.add_parser('process_files')
    fh_parser_group = parser_fh.add_argument_group(title="Process evtx files")
    fh_parser_group.add_argument('--files', '-f', help="evtx file", nargs='+', required=True)
    fh_parser_group.set_defaults(func=process_files)

    # Parser for folder containing evtx files
    parser_fh = subparsers.add_parser('process_folder')
    folder_parser_group = parser_fh.add_argument_group(title="Process folder containing evtx files")
    folder_parser_group.add_argument('--folder', help="Folder containing evtx files", required=True)
    folder_parser_group.set_defaults(func=process_folder)

    args = parser.parse_args()
    try:
        stream_handler.setLevel(logging.getLevelName(args.loglevel))
        args.func(args)
    except Exception as err:
        print("Error: %s\n" % err)
        parser.print_help()