#!/usr/bin/env python # -*- coding: utf-8 -*- import os import mimetypes import shlex import subprocess import zipfile import argparse import oletools.oleid import olefile import officedissector import warnings import exifread from PIL import Image # from PIL import PngImagePlugin from pdfid import PDFiD, cPDFiD from kittengroomer import FileBase, KittenGroomerBase SEVENZ_PATH = '/usr/bin/7z' class Config: # Application subtypes (mimetype: 'application/') mimes_ooxml = ['vnd.openxmlformats-officedocument.'] mimes_office = ['msword', 'vnd.ms-'] mimes_libreoffice = ['vnd.oasis.opendocument'] mimes_rtf = ['rtf', 'richtext'] mimes_pdf = ['pdf', 'postscript'] mimes_xml = ['xml'] mimes_ms = ['dosexec'] mimes_compressed = ['zip', 'rar', 'bzip2', 'lzip', 'lzma', 'lzop', 'xz', 'compress', 'gzip', 'tar'] mimes_data = ['octet-stream'] # Image subtypes mimes_exif = ['image/jpeg', 'image/tiff'] mimes_png = ['image/png'] # Mimetypes with metadata mimes_metadata = ['image/jpeg', 'image/tiff', 'image/png'] # Commonly used malicious extensions # Sources: http://www.howtogeek.com/137270/50-file-extensions-that-are-potentially-dangerous-on-windows/ # https://github.com/wiregit/wirecode/blob/master/components/core-settings/src/main/java/org/limewire/core/settings/FilterSettings.java malicious_exts = ( # Applications ".exe", ".pif", ".application", ".gadget", ".msi", ".msp", ".com", ".scr", ".hta", ".cpl", ".msc", ".jar", # Scripts ".bat", ".cmd", ".vb", ".vbs", ".vbe", ".js", ".jse", ".ws", ".wsf", ".wsc", ".wsh", ".ps1", ".ps1xml", ".ps2", ".ps2xml", ".psc1", ".psc2", ".msh", ".msh1", ".msh2", ".mshxml", ".msh1xml", ".msh2xml", # Shortcuts ".scf", ".lnk", ".inf", # Other ".reg", ".dll", # Office macro (OOXML with macro enabled) ".docm", ".dotm", ".xlsm", ".xltm", ".xlam", ".pptm", ".potm", ".ppam", ".ppsm", ".sldm", # banned from wirecode ".asf", ".asx", ".au", ".htm", ".html", ".mht", ".vbs", ".wax", ".wm", ".wma", ".wmd", ".wmv", ".wmx", ".wmz", ".wvx", ) # Aliases aliases = { # Win executables 'application/x-msdos-program': 'application/x-dosexec', 'application/x-dosexec': 'application/x-msdos-program', # Other apps with confusing mimetypes 'application/rtf': 'text/rtf', } # Sometimes, mimetypes.guess_type gives unexpected results, such as for .tar.gz files: # In [12]: mimetypes.guess_type('toot.tar.gz', strict=False) # Out[12]: ('application/x-tar', 'gzip') # It works as expected if you do mimetypes.guess_type('application/gzip', strict=False) override_ext = {'.gz': 'application/gzip'} class File(FileBase): def __init__(self, src_path, dst_path, logger): super(File, self).__init__(src_path, dst_path, logger) self.is_recursive = False self.log_details.update({'maintype': self.main_type, 'subtype': self.sub_type, 'extension': self.extension}) subtypes_apps = [ (Config.mimes_office, self._winoffice), (Config.mimes_ooxml, self._ooxml), (Config.mimes_rtf, self.text), (Config.mimes_libreoffice, self._libreoffice), (Config.mimes_pdf, self._pdf), (Config.mimes_xml, self.text), (Config.mimes_ms, self._executables), (Config.mimes_compressed, self._archive), (Config.mimes_data, self._binary_app), ] self.app_subtype_methods = self._make_method_dict(subtypes_apps) types_metadata = [ (Config.mimes_exif, self._metadata_exif), (Config.mimes_png, self._metadata_png), ] self.metadata_mimetype_methods = self._make_method_dict(types_metadata) self.mime_processing_options = { 'text': self.text, 'audio': self.audio, 'image': self.image, 'video': self.video, 'application': self.application, 'example': self.example, 'message': self.message, 'model': self.model, 'multipart': self.multipart, 'inode': self.inode, } def _check_dangerous(self): if not self.has_mimetype(): # No mimetype, should not happen. self.make_dangerous() if not self.has_extension(): self.make_dangerous() if self.extension in Config.malicious_exts: self.log_details.update({'malicious_extension': self.extension}) self.make_dangerous() def _check_extension(self): """Guesses the file's mimetype based on its extension. If the file's mimetype (as determined by libmagic) is contained in the mimetype module's list of valid mimetypes and the expected mimetype based on its extension differs from the mimetype determined by libmagic, then it marks the file as dangerous.""" if self.extension in Config.override_ext: expected_mimetype = Config.override_ext[self.extension] else: expected_mimetype, encoding = mimetypes.guess_type(self.src_path, strict=False) if expected_mimetype in Config.aliases: expected_mimetype = Config.aliases[expected_mimetype] is_known_extension = self.extension in mimetypes.types_map.keys() if is_known_extension and expected_mimetype != self.mimetype: self.log_details.update({'expected_mimetype': expected_mimetype}) self.make_dangerous() def _check_mimetype(self): """Takes the mimetype (as determined by libmagic) and determines whether the list of extensions that are normally associated with that extension contains the file's actual extension.""" if self.mimetype in Config.aliases: mimetype = Config.aliases[self.mimetype] else: mimetype = self.mimetype expected_extensions = mimetypes.guess_all_extensions(mimetype, strict=False) if expected_extensions: if self.has_extension() and self.extension not in expected_extensions: self.log_details.update({'expected_extensions': expected_extensions}) self.make_dangerous() def check(self): self._check_dangerous() self._check_extension() self._check_mimetype() if not self.is_dangerous(): self.mime_processing_options.get(self.main_type, self.unknown)() # ##### Helper functions ##### def _make_method_dict(self, list_of_tuples): """Returns a dictionary with mimetype: method pairs.""" dict_to_return = {} for list_of_subtypes, method in list_of_tuples: for subtype in list_of_subtypes: dict_to_return[subtype] = method return dict_to_return def write_log(self): """Print the logs related to the current file being processed.""" # LOG: move to helpers.py? tmp_log = self.logger.log.fields(**self.log_details) if self.is_dangerous(): tmp_log.warning(self.log_string) elif self.log_details.get('unknown') or self.log_details.get('binary'): tmp_log.info(self.log_string) else: tmp_log.debug(self.log_string) @property def has_metadata(self): if self.mimetype in Config.mimes_metadata: return True return False def make_tempdir(self): """Make a temporary directory.""" self.tempdir_path = self.dst_path + '_temp' if not os.path.exists(self.tempdir_path): os.makedirs(self.tempdir_path) return self.tempdir_path ####################### # ##### Discarded mimetypes, reason in the docstring ###### def inode(self): """Empty file or symlink.""" if self.is_symlink(): self.log_string += 'Symlink to {}'.format(self.log_details['symlink']) else: self.log_string += 'Inode file' def unknown(self): """Main type should never be unknown.""" self.log_string += 'Unknown file' def example(self): """Used in examples, should never be returned by libmagic.""" self.log_string += 'Example file' def multipart(self): """Used in web apps, should never be returned by libmagic""" self.log_string += 'Multipart file' # ##### Treated as malicious, no reason to have it on a USB key ###### def message(self): """Process a message file.""" self.log_string += 'Message file' self.make_dangerous() def model(self): """Process a model file.""" self.log_string += 'Model file' self.make_dangerous() # ##### Files that will be converted ###### def text(self): """Process an rtf, ooxml, or plaintext file.""" for mt in Config.mimes_rtf: if mt in self.sub_type: self.log_string += 'Rich Text file' # TODO: need a way to convert it to plain text self.force_ext('.txt') return for mt in Config.mimes_ooxml: if mt in self.sub_type: self.log_string += 'OOXML File' self._ooxml() return self.log_string += 'Text file' self.force_ext('.txt') def application(self): """Processes an application specific file according to its subtype.""" for subtype, method in self.app_subtype_methods.items(): if subtype in self.sub_type: method() self.log_string += 'Application file' return self.log_string += 'Unknown Application file' self._unknown_app() def _executables(self): """Processes an executable file.""" self.add_log_details('processing_type', 'executable') self.make_dangerous() def _winoffice(self): """Processes a winoffice file using olefile/oletools.""" self.add_log_details('processing_type', 'WinOffice') # Try as if it is a valid document oid = oletools.oleid.OleID(self.src_path) if not olefile.isOleFile(self.src_path): # Manual processing, may already count as suspicious try: ole = olefile.OleFileIO(self.src_path, raise_defects=olefile.DEFECT_INCORRECT) except: self.add_log_details('not_parsable', True) self.make_dangerous() if ole.parsing_issues: self.add_log_details('parsing_issues', True) self.make_dangerous() else: if ole.exists('macros/vba') or ole.exists('Macros') \ or ole.exists('_VBA_PROJECT_CUR') or ole.exists('VBA'): self.add_log_details('macro', True) self.make_dangerous() else: indicators = oid.check() # Encrypted ban be set by multiple checks on the script if oid.encrypted.value: self.add_log_details('encrypted', True) self.make_dangerous() if oid.macros.value or oid.ole.exists('macros/vba') or oid.ole.exists('Macros') \ or oid.ole.exists('_VBA_PROJECT_CUR') or oid.ole.exists('VBA'): self.add_log_details('macro', True) self.make_dangerous() for i in indicators: if i.id == 'ObjectPool' and i.value: # FIXME: Is it suspicious? self.add_log_details('objpool', True) elif i.id == 'flash' and i.value: self.add_log_details('flash', True) self.make_dangerous() def _ooxml(self): """Processes an ooxml file.""" self.add_log_details('processing_type', 'ooxml') try: doc = officedissector.doc.Document(self.src_path) except Exception: # Invalid file self.make_dangerous() return # There are probably other potentially malicious features: # fonts, custom props, custom XML if doc.is_macro_enabled or len(doc.features.macros) > 0: self.add_log_details('macro', True) self.make_dangerous() if len(doc.features.embedded_controls) > 0: self.add_log_details('activex', True) self.make_dangerous() if len(doc.features.embedded_objects) > 0: # Exploited by CVE-2014-4114 (OLE) self.add_log_details('embedded_obj', True) self.make_dangerous() if len(doc.features.embedded_packages) > 0: self.add_log_details('embedded_pack', True) self.make_dangerous() def _libreoffice(self): """Processes a libreoffice file.""" self.add_log_details('processing_type', 'libreoffice') # As long as there ar no way to do a sanity check on the files => dangerous try: lodoc = zipfile.ZipFile(self.src_path, 'r') except: # TODO: are there specific exceptions we should catch here? Or is anything ok self.add_log_details('invalid', True) self.make_dangerous() for f in lodoc.infolist(): fname = f.filename.lower() if fname.startswith('script') or fname.startswith('basic') or \ fname.startswith('object') or fname.endswith('.bin'): self.add_log_details('macro', True) self.make_dangerous() def _pdf(self): """Processes a PDF file.""" self.add_log_details('processing_type', 'pdf') xmlDoc = PDFiD(self.src_path) oPDFiD = cPDFiD(xmlDoc, True) # TODO: are there other characteristics which should be dangerous? if oPDFiD.encrypt.count > 0: self.add_log_details('encrypted', True) self.make_dangerous() if oPDFiD.js.count > 0 or oPDFiD.javascript.count > 0: self.add_log_details('javascript', True) self.make_dangerous() if oPDFiD.aa.count > 0 or oPDFiD.openaction.count > 0: self.add_log_details('openaction', True) self.make_dangerous() if oPDFiD.richmedia.count > 0: self.add_log_details('flash', True) self.make_dangerous() if oPDFiD.launch.count > 0: self.add_log_details('launch', True) self.make_dangerous() def _archive(self): """Processes an archive using 7zip. The archive is extracted to a temporary directory and self.process_dir is called on that directory. The recursive archive depth is increased to protect against archive bombs.""" self.add_log_details('processing_type', 'archive') self.is_recursive = True # self.log_string += 'Archive extracted, processing content.' def _unknown_app(self): """Processes an unknown file.""" self.make_unknown() def _binary_app(self): """Processses an unknown binary file.""" self.make_binary() ####################### # Metadata extractors def _metadata_exif(self, metadata_file_path): # TODO: this method is kind of long, can we shorten it? img = open(self.src_path, 'rb') tags = None try: tags = exifread.process_file(img, debug=True) except Exception as e: # LOG: log instead of print print("Error while trying to grab full metadata for file {}; retrying for partial data.".format(self.src_path)) print(e) if tags is None: try: tags = exifread.process_file(img, debug=True) except Exception as e: # LOG: log instead of print print("Failed to get any metadata for file {}.".format(self.src_path)) print(e) img.close() return False for tag in sorted(tags.keys()): # These are long and obnoxious/binary if tag not in ('JPEGThumbnail', 'TIFFThumbnail'): printable = str(tags[tag]) # Exifreader truncates data. if len(printable) > 25 and printable.endswith(", ... ]"): value = tags[tag].values printable = str(value) with open(metadata_file_path, 'w+') as metadata_file: metadata_file.write("Key: {}\tValue: {}\n".format(tag, printable)) self.add_log_details('metadata', 'exif') img.close() return True def _metadata_png(self, metadata_file_path): warnings.simplefilter('error', Image.DecompressionBombWarning) try: img = Image.open(self.src_path) for tag in sorted(img.info.keys()): # These are long and obnoxious/binary if tag not in ('icc_profile'): with open(metadata_file_path, 'w+') as metadata_file: metadata_file.write("Key: {}\tValue: {}\n".format(tag, img.info[tag])) self.add_log_details('metadata', 'png') img.close() # Catch decompression bombs except Exception as e: # LOG: log instead of print print("Caught exception processing metadata for {}".format(self.src_path)) print(e) self.make_dangerous() return False def extract_metadata(self): metadata_file_path = self.create_metadata_file(".metadata.txt") mt = self.mimetype metadata_processing_method = self.metadata_mimetype_methods.get(mt) if metadata_processing_method: # TODO: should we return metadata and write it here instead of in processing method? metadata_processing_method(metadata_file_path) ####################### # ##### Media - audio and video aren't converted ###### def audio(self): """Processes an audio file.""" self.log_string += 'Audio file' self._media_processing() def video(self): """Processes a video.""" self.log_string += 'Video file' self._media_processing() def _media_processing(self): """Generic way to process all media files.""" self.add_log_details('processing_type', 'media') def image(self): """Processes an image. Extracts metadata to dest key if metadata is present. Creates a temporary directory on dest key, opens the using PIL.Image,saves it to the temporary directory, and copies it to the destination.""" # TODO: make sure this method works for png, gif, tiff if self.has_metadata: self.extract_metadata() tempdir_path = self.make_tempdir() tempfile_path = os.path.join(tempdir_path, self.filename) warnings.simplefilter('error', Image.DecompressionBombWarning) try: # Do image conversions img_in = Image.open(self.src_path) img_out = Image.frombytes(img_in.mode, img_in.size, img_in.tobytes()) img_out.save(tempfile_path) self.src_path = tempfile_path except Exception as e: # Catch decompression bombs # TODO: change this from all Exceptions to specific DecompressionBombWarning # LOG: change this from printing to logging print("Caught exception (possible decompression bomb?) while translating file {}.".format(self.src_path)) print(e) self.make_dangerous() self.log_string += 'Image file' self.add_log_details('processing_type', 'image') class KittenGroomerFileCheck(KittenGroomerBase): def __init__(self, root_src, root_dst, max_recursive_depth=2, debug=False): super(KittenGroomerFileCheck, self).__init__(root_src, root_dst, debug) self.recursive_archive_depth = 0 self.max_recursive_depth = max_recursive_depth def process_dir(self, src_dir, dst_dir): """Main function coordinating file processing.""" # LOG: we probably want to move this write_log elsewhere: # if self.recursive_archive_depth > 0: # self.write_log() # TODO: Can we clean up the way we handle relative_path? for srcpath in self.list_all_files(src_dir): dstpath = srcpath.replace(src_dir, dst_dir) relative_path = srcpath.replace(src_dir + '/', '') self.cur_file = File(srcpath, dstpath, self.logger) # LOG: move this logging code elsewhere self.logger.log.info('Processing {} ({}/{})', relative_path, self.cur_file.main_type, self.cur_file.sub_type) self.process_file(self.cur_file) def process_file(self, file): file.check() if file.is_recursive: self.process_archive(file) else: # TODO: Make a File attribute for should be copied True/False and check it self._safe_copy() file.write_log() if hasattr(file, "tempdir_path"): self._safe_rmtree(file.tempdir_path) def process_archive(self, file): """Unpacks an archive using 7zip and processes contents. Should be given a Kittengroomer file object whose src_path points to an archive.""" self.recursive_archive_depth += 1 # Check for archivebomb if self.recursive_archive_depth >= self.max_recursive_depth: self._handle_archivebomb(file) else: tempdir_path = file.make_tempdir() command_str = '{} -p1 x "{}" -o"{}" -bd -aoa' unpack_command = command_str.format(SEVENZ_PATH, file.src_path, tempdir_path) self._run_process(unpack_command) # LOG: check that tree is working correctly here self.logger.tree(tempdir_path) self.process_dir(tempdir_path, file.dst_path) self._safe_rmtree(tempdir_path) self.recursive_archive_depth -= 1 def _handle_archivebomb(self, file): file.make_dangerous() file.add_log_details('Archive Bomb', True) self.logger.log.warning('ARCHIVE BOMB.') self.logger.log.warning('The content of the archive contains recursively other archives.') self.logger.log.warning('This is a bad sign so the archive is not extracted to the destination key.') # TODO: delete whatever we want to delete that's already been copied to dest dir def _run_process(self, command_string, timeout=None): """Run command_string in a subprocess, wait until it finishes.""" args = shlex.split(command_string) with open(self.logger.log_debug_err, 'ab') as stderr, open(self.logger.log_debug_out, 'ab') as stdout: try: subprocess.check_call(args, stdout=stdout, stderr=stderr, timeout=timeout) except (subprocess.TimeoutExpired, subprocess.CalledProcessError): return return True def run(self): self.process_dir(self.src_root_dir, self.dst_root_dir) def main(kg_implementation, description): parser = argparse.ArgumentParser(prog='KittenGroomer', description=description) parser.add_argument('-s', '--source', type=str, help='Source directory') parser.add_argument('-d', '--destination', type=str, help='Destination directory') args = parser.parse_args() kg = kg_implementation(args.source, args.destination) kg.run() if __name__ == '__main__': main(KittenGroomerFileCheck, 'File sanitizer used in CIRCLean. Renames potentially dangerous files.')