# Mobile Verification Toolkit (MVT) # Copyright (c) 2021 The MVT Project Authors. # Use of this software is governed by the MVT License 1.1 that can be found at # https://license.mvt.re/1.1/ import io import json import os import requests from appdirs import user_data_dir from .url import URL class Indicators: """This class is used to parse indicators from a STIX2 file and provide functions to compare extracted artifacts to the indicators. """ def __init__(self, log=None): self.data_dir = user_data_dir("mvt") self.log = log self.ioc_domains = [] self.ioc_processes = [] self.ioc_emails = [] self.ioc_files = [] self.ioc_files_sha256 = [] self.ioc_app_ids = [] self.ios_profile_ids = [] self.ioc_count = 0 def _add_indicator(self, ioc, iocs_list): if ioc not in iocs_list: iocs_list.append(ioc) self.ioc_count += 1 def _load_downloaded_indicators(self): if not os.path.isdir(self.data_dir): return False for f in os.listdir(self.data_dir): if f.lower().endswith(".stix2"): self.parse_stix2(os.path.join(self.data_dir, f)) def _check_stix2_env_variable(self): """ Checks if a variable MVT_STIX2 contains path to STIX Files """ if "MVT_STIX2" not in os.environ: return False paths = os.environ["MVT_STIX2"].split(":") for path in paths: if os.path.isfile(path): self.parse_stix2(path) else: self.log.info("Invalid STIX2 path %s in MVT_STIX2 environment variable", path) def load_indicators_files(self, files): """ Load a list of indicators files """ for file_path in files: if os.path.isfile(file_path): self.parse_stix2(file_path) else: self.log.warning("This indicators file %s does not exist", file_path) # Load downloaded indicators and any indicators from env variable self._load_downloaded_indicators() self._check_stix2_env_variable() self.log.info("Loaded a total of %d unique indicators", self.ioc_count) def parse_stix2(self, file_path): """Extract indicators from a STIX2 file. :param file_path: Path to the STIX2 file to parse :type file_path: str """ self.log.info("Parsing STIX2 indicators file at path %s", file_path) with open(file_path, "r") as handle: try: data = json.load(handle) except json.decoder.JSONDecodeError: self.log.critical("Unable to parse STIX2 indicator file. The file is malformed or in the wrong format.") return for entry in data.get("objects", []): if entry.get("type", "") != "indicator": continue key, value = entry.get("pattern", "").strip("[]").split("=") value = value.strip("'") if key == "domain-name:value": # We force domain names to lower case. self._add_indicator(ioc=value.lower(), iocs_list=self.ioc_domains) elif key == "process:name": self._add_indicator(ioc=value, iocs_list=self.ioc_processes) elif key == "email-addr:value": # We force email addresses to lower case. self._add_indicator(ioc=value.lower(), iocs_list=self.ioc_emails) elif key == "file:name": self._add_indicator(ioc=value, iocs_list=self.ioc_files) elif key == "app:id": self._add_indicator(ioc=value, iocs_list=self.ioc_app_ids) elif key == "configuration-profile:id": self._add_indicator(ioc=value, iocs_list=self.ios_profile_ids) elif key == "file:hashes.sha256": self._add_indicator(ioc=value, iocs_list=self.ioc_files_sha256) def check_domain(self, url) -> bool: """Check if a given URL matches any of the provided domain indicators. :param url: URL to match against domain indicators :type url: str :returns: True if the URL matched an indicator, otherwise False :rtype: bool """ # TODO: If the IOC domain contains a subdomain, it is not currently # being matched. if not url: return False try: # First we use the provided URL. orig_url = URL(url) if orig_url.check_if_shortened(): # If it is, we try to retrieve the actual URL making an # HTTP HEAD request. unshortened = orig_url.unshorten() # self.log.info("Found a shortened URL %s -> %s", # url, unshortened) # Now we check for any nested URL shorteners. dest_url = URL(unshortened) if dest_url.check_if_shortened(): # self.log.info("Original URL %s appears to shorten another shortened URL %s ... checking!", # orig_url.url, dest_url.url) return self.check_domain(dest_url.url) final_url = dest_url else: # If it's not shortened, we just use the original URL object. final_url = orig_url except Exception: # If URL parsing failed, we just try to do a simple substring # match. for ioc in self.ioc_domains: if ioc.lower() in url: self.log.warning("Maybe found a known suspicious domain: %s", url) return True # If nothing matched, we can quit here. return False # If all parsing worked, we start walking through available domain indicators. for ioc in self.ioc_domains: # First we check the full domain. if final_url.domain.lower() == ioc: if orig_url.is_shortened and orig_url.url != final_url.url: self.log.warning("Found a known suspicious domain %s shortened as %s", final_url.url, orig_url.url) else: self.log.warning("Found a known suspicious domain: %s", final_url.url) return True # Then we just check the top level domain. if final_url.top_level.lower() == ioc: if orig_url.is_shortened and orig_url.url != final_url.url: self.log.warning("Found a sub-domain matching a known suspicious top level %s shortened as %s", final_url.url, orig_url.url) else: self.log.warning("Found a sub-domain matching a known suspicious top level: %s", final_url.url) return True return False def check_domains(self, urls) -> bool: """Check a list of URLs against the provided list of domain indicators. :param urls: List of URLs to check against domain indicators :type urls: list :returns: True if any URL matched an indicator, otherwise False :rtype: bool """ if not urls: return False for url in urls: if self.check_domain(url): return True return False def check_process(self, process) -> bool: """Check the provided process name against the list of process indicators. :param process: Process name to check against process indicators :type process: str :returns: True if process matched an indicator, otherwise False :rtype: bool """ if not process: return False proc_name = os.path.basename(process) if proc_name in self.ioc_processes: self.log.warning("Found a known suspicious process name \"%s\"", process) return True if len(proc_name) == 16: for bad_proc in self.ioc_processes: if bad_proc.startswith(proc_name): self.log.warning("Found a truncated known suspicious process name \"%s\"", process) return True return False def check_processes(self, processes) -> bool: """Check the provided list of processes against the list of process indicators. :param processes: List of processes to check against process indicators :type processes: list :returns: True if process matched an indicator, otherwise False :rtype: bool """ if not processes: return False for process in processes: if self.check_process(process): return True return False def check_email(self, email) -> bool: """Check the provided email against the list of email indicators. :param email: Email address to check against email indicators :type email: str :returns: True if email address matched an indicator, otherwise False :rtype: bool """ if not email: return False if email.lower() in self.ioc_emails: self.log.warning("Found a known suspicious email address: \"%s\"", email) return True return False def check_file_name(self, file_path) -> bool: """Check the provided file path against the list of file indicators. :param file_path: File path or file name to check against file indicators :type file_path: str :returns: True if the file path matched an indicator, otherwise False :rtype: bool """ if not file_path: return False file_name = os.path.basename(file_path) if file_name in self.ioc_files: return True return False # TODO: The difference between check_file_name() and check_file_path() # needs to be more explicit and clear. Probably, the two should just # be combined into one function. def check_file_path(self, file_path) -> bool: """Check the provided file path against the list of file indicators. :param file_path: File path or file name to check against file indicators :type file_path: str :returns: True if the file path matched an indicator, otherwise False :rtype: bool """ if not file_path: return False for ioc_file in self.ioc_files: # Strip any trailing slash from indicator paths to match directories. if file_path.startswith(ioc_file.rstrip("/")): return True return False def check_profile(self, profile_uuid) -> bool: """Check the provided configuration profile UUID against the list of indicators. :param profile_uuid: Profile UUID to check against configuration profile indicators :type profile_uuid: str :returns: True if the UUID in indicator list, otherwise False :rtype: bool """ if profile_uuid in self.ios_profile_ids: return True return False def download_indicators_files(log): """ Download indicators from repo into MVT app data directory """ data_dir = user_data_dir("mvt") if not os.path.isdir(data_dir): os.makedirs(data_dir, exist_ok=True) # Download latest list of indicators from the MVT repo. res = requests.get("https://github.com/mvt-project/mvt/raw/main/public_indicators.json") if res.status_code != 200: log.warning("Unable to find retrieve list of indicators from the MVT repository.") return for ioc_entry in res.json(): ioc_url = ioc_entry["stix2_url"] log.info("Downloading indicator file '%s' from '%s'", ioc_entry["name"], ioc_url) res = requests.get(ioc_url) if res.status_code != 200: log.warning("Could not find indicator file '%s'", ioc_url) continue clean_file_name = ioc_url.lstrip("https://").replace("/", "_") ioc_path = os.path.join(data_dir, clean_file_name) # Write file to disk. This will overwrite any older version of the STIX2 file. with io.open(ioc_path, "w") as f: f.write(res.text) log.info("Saved indicator file to '%s'", os.path.basename(ioc_path))