censys_enrich.py

# encoding: utf-8
import json
import configparser
import base64
import codecs
import censys.common.config
from dateutil.parser import isoparse
from . import check_input_attribute, standard_error_message
from pymisp import MISPAttribute, MISPEvent, MISPObject

try:
    #needed in order to overwrite the censys module intent of creating config files in the home folder of the proccess owner
    #--
    def get_config_over() -> configparser.ConfigParser:
        config = configparser.ConfigParser()
        config[censys.common.config.DEFAULT] = censys.common.config.default_config
        return config
    censys.common.config.get_config = get_config_over
    #--

    from censys.search import CensysHosts
    from censys.search import CensysCertificates
    from censys.common.base import *
except ImportError:
    print("Censys module not installed. Try 'pip install censys'")

misperrors = {'error': 'Error'}
moduleconfig = ['api_id', 'api_secret']
mispattributes = {'input': ['ip-src', 'ip-dst', 'domain', 'hostname', 'hostname|port', 'domain|ip', 'ip-dst|port', 'ip-src|port',
                  'x509-fingerprint-md5', 'x509-fingerprint-sha1', 'x509-fingerprint-sha256'], 'format': 'misp_standard'}
moduleinfo = {'version': '0.1', 'author': 'Loïc Fortemps',
              'description': 'Censys.io expansion module', 'module-type': ['expansion', 'hover']}

api_id = None
api_secret = None

def handler(q=False):
    global api_id, api_secret
    if q is False:
        return False
    request = json.loads(q)

    if request.get('config'):
        if (request['config'].get('api_id') is None) or (request['config'].get('api_secret') is None):
            misperrors['error'] = "Censys API credentials are missing"
            return misperrors
    else:
        misperrors['error'] = "Please provide config options"
        return misperrors

    api_id = request['config']['api_id']
    api_secret = request['config']['api_secret']

    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.'}
    attribute = request['attribute']
    if not any(input_type == attribute['type'] for input_type in mispattributes['input']):
        return {'error': 'Unsupported attribute type.'}

    attribute = MISPAttribute()
    attribute.from_dict(**request['attribute'])
    # Lists to accomodate multi-types attribute
    types = list()
    values = list()
    results = list()

    if "|" in attribute.type:
        t_1, t_2 = attribute.type.split('|')
        v_1, v_2 = attribute.value.split('|')
        # We cannot use the port information
        if t_2 == "port":
            types.append(t_1)
            values.append(v_1)
        else:
            types = [t_1, t_2]
            values = [v_1, v_2]
    else:
        types.append(attribute.type)
        values.append(attribute.value)

    found = False
    for t in types:
        try:
            value = values.pop(0)
            # ip, ip-src or ip-dst
            if t[:2] == "ip":
                r = CensysHosts(api_id, api_secret).view(value)
                results.append(parse_response(r, attribute))
                found = True
            elif t == 'domain' or t == "hostname":
                # get ips
                endpoint = CensysHosts(api_id, api_secret)
                for r_list in endpoint.search(query=value, per_page=5, pages=1):
                    for r in r_list:
                        results.append(parse_response(r, attribute))
                        found = True
            elif 'x509-fingerprint-sha256' in t:
                # use api_v1 as Certificates endpoint in api_v2 doesn't yet provide all the details
                r = CensysCertificates(api_id, api_secret).view(value)
                results.append(parse_response(r, attribute))
                found = True
        except CensysException as e:
            misperrors['error'] = "ERROR: param {} / response: {}".format(value, e)
            return misperrors

    if not found:
        misperrors['error'] = "Nothing could be found on Censys"
        return misperrors

    return {'results': remove_duplicates(results)}


def parse_response(censys_output, attribute):
    misp_event = MISPEvent()
    misp_event.add_attribute(**attribute)
    # Generic fields (for IP/Websites)
    if censys_output.get('autonomous_system'):
        cen_as = censys_output.get('autonomous_system')
        asn_object = MISPObject('asn')
        asn_object.add_attribute('asn', value=cen_as.get("asn"))
        asn_object.add_attribute('description', value=cen_as.get('name'))
        asn_object.add_attribute('subnet-announced', value=cen_as.get('routed_prefix'))
        asn_object.add_attribute('country', value=cen_as.get('country_code'))
        asn_object.add_reference(attribute.uuid, 'associated-to')
        misp_event.add_object(**asn_object)

    if censys_output.get('ip') and len(censys_output.get('services')): #"ports" in censys_output
        ip_object = MISPObject('ip-port')
        ip_object.add_attribute('ip', value=censys_output.get('ip'))
        for serv in censys_output.get('services'):
            if serv.get('port'):
                ip_object.add_attribute('dst-port', value=serv.get('port'))
        ip_object.add_reference(attribute.uuid, 'associated-to')
        misp_event.add_object(**ip_object)

    # We explore all ports to find https or ssh services
    for serv in censys_output.get('services', []):
        if not isinstance(serv, dict):
            continue
        if serv.get('service_name').lower() == 'http' and serv.get('certificate', None):
            try:
                cert = serv.get('certificate', None)
                if cert:
                    # TODO switch to api_v2 once available
                    # use api_v1 as Certificates endpoint in api_v2 doesn't yet provide all the details
                    cert_details = CensysCertificates(api_id, api_secret).view(cert)
                    cert_obj = get_certificate_object(cert_details, attribute)
                    misp_event.add_object(**cert_obj)
            except KeyError:
                print("Error !")
        if serv.get('ssh') and serv.get('service_name').lower() == 'ssh':
            try:
                cert = serv.get('ssh').get('server_host_key').get('fingerprint_sha256')
                # TODO enable once the type is merged
                # misp_event.add_attribute(type='hasshserver-sha256', value=cert['fingerprint_sha256'])
            except KeyError:
                pass

    # Info from certificate query
    if "parsed" in censys_output:
        cert_obj = get_certificate_object(censys_output, attribute)
        misp_event.add_object(**cert_obj)

    # Location can be present for IP/Websites results
    if "location" in censys_output:
        loc_obj = MISPObject('geolocation')
        loc = censys_output['location']
        loc_obj.add_attribute('latitude', value=loc.get('coordinates', {}).get('latitude', None))
        loc_obj.add_attribute('longitude', value=loc.get('coordinates', {}).get('longitude', None))
        if 'city' in loc:
            loc_obj.add_attribute('city', value=loc.get('city'))
        loc_obj.add_attribute('country', value=loc.get('country'))
        if 'postal_code' in loc:
            loc_obj.add_attribute('zipcode', value=loc.get('postal_code'))
        if 'province' in loc:
            loc_obj.add_attribute('region', value=loc.get('province'))
        loc_obj.add_reference(attribute.uuid, 'associated-to')
        misp_event.add_object(**loc_obj)

    event = json.loads(misp_event.to_json())
    return {'Object': event.get('Object', []), 'Attribute': event.get('Attribute', [])}


# In case of multiple enrichment (ip and domain), we need to filter out similar objects
# TODO: make it more granular
def remove_duplicates(results):
    # Only one enrichment was performed so no duplicate
    if len(results) == 1:
        return results[0]
    else:
        final_result = results[0]
        for i,result in enumerate(results[1:]):
            obj_l = results[i+1].get('Object', [])
            for o2 in obj_l:
                if o2['name'] == "asn":
                    key = "asn"
                elif o2['name'] == "ip-port":
                    key = "ip"
                elif o2['name'] == "x509":
                    key = "x509-fingerprint-sha256"
                elif o2['name'] == "geolocation":
                    key = "latitude"
                if not check_if_present(o2, key, final_result.get('Object', [])):
                    final_result['Object'].append(o2)

    return final_result


def check_if_present(object, attribute_name, list_objects):
    """
    Assert if a given object is present in the list.

    This function check if object (json format) is present in list_objects
    using attribute_name for the matching
    """
    for o in list_objects:
        # We first look for a match on the name
        if o['name'] == object['name']:
            for attr in object['Attribute']:
                # Within the attributes, we look for the one to compare
                if attr['type'] == attribute_name:
                    # Then we check the attributes of the other object and look for a match
                    for attr2 in o['Attribute']:
                        if attr2['type'] == attribute_name and attr2['value'] == attr['value']:
                            return True

    return False


def get_certificate_object(cert, attribute):
    parsed = cert['parsed']
    cert_object = MISPObject('x509')
    cert_object.add_attribute('x509-fingerprint-sha256', value=parsed['fingerprint_sha256'])
    cert_object.add_attribute('x509-fingerprint-sha1', value=parsed['fingerprint_sha1'])
    cert_object.add_attribute('x509-fingerprint-md5', value=parsed['fingerprint_md5'])
    cert_object.add_attribute('serial-number', value=parsed['serial_number'])
    cert_object.add_attribute('version', value=parsed['version'])
    cert_object.add_attribute('subject', value=parsed['subject_dn'])
    cert_object.add_attribute('issuer', value=parsed['issuer_dn'])
    cert_object.add_attribute('validity-not-before', value=isoparse(parsed['validity']['start']))
    cert_object.add_attribute('validity-not-after', value=isoparse(parsed['validity']['end']))
    cert_object.add_attribute('self_signed', value=parsed['signature']['self_signed'])
    cert_object.add_attribute('signature_algorithm', value=parsed['signature']['signature_algorithm']['name'])

    cert_object.add_attribute('pubkey-info-algorithm', value=parsed['subject_key_info']['key_algorithm']['name'])

    if 'rsa_public_key' in parsed['subject_key_info']:
        pub_key = parsed['subject_key_info']['rsa_public_key']
        cert_object.add_attribute('pubkey-info-size', value=pub_key['length'])
        cert_object.add_attribute('pubkey-info-exponent', value=pub_key['exponent'])
        hex_mod = codecs.encode(base64.b64decode(pub_key['modulus']), 'hex').decode()
        cert_object.add_attribute('pubkey-info-modulus', value=hex_mod)

    if "extensions" in parsed and "subject_alt_name" in parsed["extensions"]:
        san = parsed["extensions"]["subject_alt_name"]
        if "dns_names" in san:
            for dns in san['dns_names']:
                cert_object.add_attribute('dns_names', value=dns)
        if "ip_addresses" in san:
            for ip in san['ip_addresses']:
                cert_object.add_attribute('ip', value=ip)

    if "raw" in cert:
        cert_object.add_attribute('raw-base64', value=cert['raw'])

    cert_object.add_reference(attribute.uuid, 'associated-to')
    return cert_object


def introspection():
    return mispattributes


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