virustotal.py

import json
from urllib.parse import urlparse
import vt
from . import check_input_attribute, standard_error_message
from pymisp import MISPAttribute, MISPEvent, MISPObject

misperrors = {'error': 'Error'}
mispattributes = {'input': ['hostname', 'domain', "ip-src", "ip-dst", "md5", "sha1", "sha256", "url"],
                  'format': 'misp_standard'}

# possible module-types: 'expansion', 'hover' or both
moduleinfo = {'version': '5', 'author': 'Hannah Ward',
              'description': 'Enrich observables with the VirusTotal v3 API',
              'module-type': ['expansion']}

# config fields that your code expects from the site admin
moduleconfig = ["apikey", "event_limit", 'proxy_host', 'proxy_port', 'proxy_username', 'proxy_password']


DEFAULT_RESULTS_LIMIT = 10


class VirusTotalParser:
    def __init__(self, client: vt.Client, limit: int) -> None:
        self.client = client
        self.limit = limit or DEFAULT_RESULTS_LIMIT
        self.misp_event = MISPEvent()
        self.attribute = MISPAttribute()
        self.parsed_objects = {}
        self.input_types_mapping = {'ip-src': self.parse_ip, 'ip-dst': self.parse_ip,
                                    'domain': self.parse_domain, 'hostname': self.parse_domain,
                                    'md5': self.parse_hash, 'sha1': self.parse_hash,
                                    'sha256': self.parse_hash, 'url': self.parse_url}
        self.proxies = None

    @staticmethod
    def get_total_analysis(analysis: dict, known_distributors: dict = None) -> int:
        if not analysis:
            return 0
        count = sum([analysis['undetected'], analysis['suspicious'], analysis['harmless']])
        return count if known_distributors else count + analysis['malicious']

    def query_api(self, attribute: dict) -> None:
        self.attribute.from_dict(**attribute)
        self.input_types_mapping[self.attribute.type](self.attribute.value)

    def get_result(self) -> dict:
        event = json.loads(self.misp_event.to_json())
        results = {key: event[key] for key in ('Attribute', 'Object') if (key in event and event[key])}
        return {'results': results}

    def add_vt_report(self, report: vt.Object) -> str:
        analysis = report.get('last_analysis_stats')
        total = self.get_total_analysis(analysis, report.get('known_distributors'))
        permalink = f'https://www.virustotal.com/gui/{report.type}/{report.id}'

        vt_object = MISPObject('virustotal-report')
        vt_object.add_attribute('permalink', type='link', value=permalink)
        detection_ratio = f"{analysis['malicious']}/{total}" if analysis else '-/-'
        vt_object.add_attribute('detection-ratio', type='text', value=detection_ratio, disable_correlation=True)
        self.misp_event.add_object(**vt_object)
        return vt_object.uuid

    def create_misp_object(self, report: vt.Object) -> MISPObject:
        misp_object = None
        vt_uuid = self.add_vt_report(report)

        if report.type == 'file':
            misp_object = MISPObject('file')
            for hash_type in ('md5', 'sha1', 'sha256', 'tlsh',
                              'vhash', 'ssdeep', 'imphash'):
                misp_object.add_attribute(hash_type,
                                          **{'type': hash_type,
                                             'value': report.get(hash_type)})
        elif report.type == 'domain':
            misp_object = MISPObject('domain-ip')
            misp_object.add_attribute('domain', type='domain', value=report.id)
        elif report.type == 'ip_address':
            misp_object = MISPObject('domain-ip')
            misp_object.add_attribute('ip', type='ip-dst', value=report.id)
        elif report.type == 'url':
            misp_object = MISPObject('url')
            misp_object.add_attribute('url', type='url', value=report.url)
        misp_object.add_reference(vt_uuid, 'analyzed-with')
        return misp_object

    ################################################################################
    ####                         Main parsing functions                         #### # noqa
    ################################################################################

    def parse_domain(self, domain: str) -> str:
        domain_report = self.client.get_object(f'/domains/{domain}')

        # DOMAIN
        domain_object = self.create_misp_object(domain_report)

        # WHOIS
        if domain_report.whois:
            whois_object = MISPObject('whois')
            whois_object.add_attribute('text', type='text', value=domain_report.whois)
            self.misp_event.add_object(**whois_object)

        # SIBLINGS AND SUBDOMAINS
        for relationship_name, misp_name in [('siblings', 'sibling-of'), ('subdomains', 'subdomain')]:
            rel_iterator = self.client.iterator(f'/domains/{domain_report.id}/{relationship_name}', limit=self.limit)
            for item in rel_iterator:
                attr = MISPAttribute()
                attr.from_dict(**dict(type='domain', value=item.id))
                self.misp_event.add_attribute(**attr)
                domain_object.add_reference(attr.uuid, misp_name)

        # RESOLUTIONS
        resolutions_iterator = self.client.iterator(f'/domains/{domain_report.id}/resolutions', limit=self.limit)
        for resolution in resolutions_iterator:
            domain_object.add_attribute('ip', type='ip-dst', value=resolution.ip_address)

        # COMMUNICATING, DOWNLOADED AND REFERRER FILES
        for relationship_name, misp_name in [
            ('communicating_files', 'communicates-with'),
            ('downloaded_files', 'downloaded-from'),
            ('referrer_files', 'referring')
        ]:
            files_iterator = self.client.iterator(f'/domains/{domain_report.id}/{relationship_name}', limit=self.limit)
            for file in files_iterator:
                file_object = self.create_misp_object(file)
                file_object.add_reference(domain_object.uuid, misp_name)
                self.misp_event.add_object(**file_object)

        # URLS
        urls_iterator = self.client.iterator(f'/domains/{domain_report.id}/urls', limit=self.limit)
        for url in urls_iterator:
            url_object = self.create_misp_object(url)
            url_object.add_reference(domain_object.uuid, 'hosted-in')
            self.misp_event.add_object(**url_object)

        self.misp_event.add_object(**domain_object)
        return domain_object.uuid

    def parse_hash(self, file_hash: str) -> str:
        file_report = self.client.get_object(f'/files/{file_hash}')
        file_object = self.create_misp_object(file_report)

        # ITW URLS
        urls_iterator = self.client.iterator(f'/files/{file_report.id}/itw_urls', limit=self.limit)
        for url in urls_iterator:
            url_object = self.create_misp_object(url)
            url_object.add_reference(file_object.uuid, 'downloaded')
            self.misp_event.add_object(**url_object)

        # COMMUNICATING, DOWNLOADED AND REFERRER FILES
        for relationship_name, misp_name in [
            ('contacted_urls', 'communicates-with'),
            ('contacted_domains', 'communicates-with'),
            ('contacted_ips', 'communicates-with')
        ]:
            files_iterator = self.client.iterator(f'/files/{file_report.id}/{relationship_name}', limit=self.limit)
            for file in files_iterator:
                file_object = self.create_misp_object(file)
                file_object.add_reference(file_object.uuid, misp_name)
                self.misp_event.add_object(**file_object)

        self.misp_event.add_object(**file_object)
        return file_object.uuid

    def parse_ip(self, ip: str) -> str:
        ip_report = self.client.get_object(f'/ip_addresses/{ip}')

        # IP
        ip_object = self.create_misp_object(ip_report)

        # ASN
        asn_object = MISPObject('asn')
        asn_object.add_attribute('asn', type='AS', value=ip_report.asn)
        asn_object.add_attribute('subnet-announced', type='ip-src', value=ip_report.network)
        asn_object.add_attribute('country', type='text', value=ip_report.country)
        self.misp_event.add_object(**asn_object)

        # RESOLUTIONS
        resolutions_iterator = self.client.iterator(f'/ip_addresses/{ip_report.id}/resolutions', limit=self.limit)
        for resolution in resolutions_iterator:
            ip_object.add_attribute('domain', type='domain', value=resolution.host_name)

        # URLS
        urls_iterator = self.client.iterator(f'/ip_addresses/{ip_report.id}/urls', limit=self.limit)
        for url in urls_iterator:
            url_object = self.create_misp_object(url)
            url_object.add_reference(ip_object.uuid, 'hosted-in')
            self.misp_event.add_object(**url_object)

        self.misp_event.add_object(**ip_object)
        return ip_object.uuid

    def parse_url(self, url: str) -> str:
        url_id = vt.url_id(url)
        url_report = self.client.get_object(f'/urls/{url_id}')
        url_object = self.create_misp_object(url_report)

        # COMMUNICATING, DOWNLOADED AND REFERRER FILES
        for relationship_name, misp_name in [
            ('communicating_files', 'communicates-with'),
            ('downloaded_files', 'downloaded-from'),
            ('referrer_files', 'referring')
        ]:
            files_iterator = self.client.iterator(f'/urls/{url_report.id}/{relationship_name}', limit=self.limit)
            for file in files_iterator:
                file_object = self.create_misp_object(file)
                file_object.add_reference(url_object.uuid, misp_name)
                self.misp_event.add_object(**file_object)

        self.misp_event.add_object(**url_object)
        return url_object.uuid


def get_proxy_settings(config: dict) -> dict:
    """Returns proxy settings in the requests format.
    If no proxy settings are set, return None."""
    proxies = None
    host = config.get('proxy_host')
    port = config.get('proxy_port')
    username = config.get('proxy_username')
    password = config.get('proxy_password')

    if host:
        if not port:
            misperrors['error'] = 'The virustotal_proxy_host config is set, ' \
                                  'please also set the virustotal_proxy_port.'
            raise KeyError
        parsed = urlparse(host)
        if 'http' in parsed.scheme:
            scheme = 'http'
        else:
            scheme = parsed.scheme
        netloc = parsed.netloc
        host = f'{netloc}:{port}'

        if username:
            if not password:
                misperrors['error'] = 'The virustotal_proxy_username config is set, ' \
                                      'please also set the virustotal_proxy_password.'
                raise KeyError
            auth = f'{username}:{password}'
            host = auth + '@' + host

        proxies = {
            'http': f'{scheme}://{host}',
            'https': f'{scheme}://{host}'
        }
    return proxies


def parse_error(status_code: int) -> str:
    status_mapping = {204: 'VirusTotal request rate limit exceeded.',
                      400: 'Incorrect request, please check the arguments.',
                      403: 'You don\'t have enough privileges to make the request.'}
    if status_code in status_mapping:
        return status_mapping[status_code]
    return "VirusTotal may not be accessible."


def handler(q=False):
    if q is False:
        return False
    request = json.loads(q)
    if not request.get('config') or not request['config'].get('apikey'):
        misperrors['error'] = 'A VirusTotal api key is required for this module.'
        return misperrors
    if not request.get('attribute') or not check_input_attribute(request['attribute']):
        return {'error': f'{standard_error_message}, which should contain at least a type, a value and an uuid.'}
    if request['attribute']['type'] not in mispattributes['input']:
        return {'error': 'Unsupported attribute type.'}

    event_limit = request['config'].get('event_limit')
    attribute = request['attribute']
    proxy_settings = get_proxy_settings(request.get('config'))

    try:
        client = vt.Client(request['config']['apikey'],
                           headers={
                               'x-tool': 'MISPModuleVirusTotalExpansion',
                           },
                           proxy=proxy_settings['http'] if proxy_settings else None)
        parser = VirusTotalParser(client, int(event_limit) if event_limit else None)
        parser.query_api(attribute)
    except vt.APIError as ex:
        misperrors['error'] = ex.message
        return misperrors

    return parser.get_result()


def introspection():
    return mispattributes


def version():
    moduleinfo['config'] = moduleconfig
    return moduleinfo