#!/usr/bin/env python # -*- coding: utf-8 -*- import os import mimetypes import shlex import subprocess import zipfile 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, main 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._check_dangerous() if self.is_dangerous(): return self.log_details.update({'maintype': self.main_type, 'subtype': self.sub_type, 'extension': self.extension}) self._check_extension() self._check_mime() 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_mime(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 len(self.extension) > 0 and self.extension not in expected_extensions: self.log_details.update({'expected_extensions': expected_extensions}) self.make_dangerous() def has_metadata(self): if self.mimetype in Config.mimes_metadata: return True return False 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 self.log_name = self.logger.log 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, } # ##### 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 _print_log(self): """Print the logs related to the current file being processed.""" # TODO: change name to _write_log, move to helpers tmp_log = self.logger.log.fields(**self.cur_file.log_details) if self.cur_file.is_dangerous(): tmp_log.warning(self.cur_file.log_string) elif self.cur_file.log_details.get('unknown') or self.cur_file.log_details.get('binary'): tmp_log.info(self.cur_file.log_string) else: tmp_log.debug(self.cur_file.log_string) def _run_process(self, command_string, timeout=None): """Run command_string in a subprocess, wait until it finishes.""" args = shlex.split(command_string) # TODO: log_debug_err and log_debug are now broken, fix, move to helpers 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 ####################### # ##### Discarded mimetypes, reason in the docstring ###### def inode(self): """Empty file or symlink.""" if self.cur_file.is_symlink(): self.cur_file.log_string += 'Symlink to {}'.format(self.cur_file.log_details['symlink']) else: self.cur_file.log_string += 'Inode file' def unknown(self): """Main type should never be unknown.""" self.cur_file.log_string += 'Unknown file' def example(self): """Used in examples, should never be returned by libmagic.""" self.cur_file.log_string += 'Example file' def multipart(self): """Used in web apps, should never be returned by libmagic""" self.cur_file.log_string += 'Multipart file' # ##### Treated as malicious, no reason to have it on a USB key ###### def message(self): """Process a message file.""" self.cur_file.log_string += 'Message file' self.cur_file.make_dangerous() self._safe_copy() def model(self): """Process a model file.""" self.cur_file.log_string += 'Model file' self.cur_file.make_dangerous() self._safe_copy() # ##### 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.cur_file.sub_type: self.cur_file.log_string += 'Rich Text file' # TODO: need a way to convert it to plain text self.cur_file.force_ext('.txt') self._safe_copy() return for mt in Config.mimes_ooxml: if mt in self.cur_file.sub_type: self.cur_file.log_string += 'OOXML File' self._ooxml() return self.cur_file.log_string += 'Text file' self.cur_file.force_ext('.txt') self._safe_copy() 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.cur_file.sub_type: method() self.cur_file.log_string += 'Application file' return self.cur_file.log_string += 'Unknown Application file' self._unknown_app() def _executables(self): """Processes an executable file.""" self.cur_file.add_log_details('processing_type', 'executable') self.cur_file.make_dangerous() self._safe_copy() def _winoffice(self): """Processes a winoffice file using olefile/oletools.""" self.cur_file.add_log_details('processing_type', 'WinOffice') # Try as if it is a valid document oid = oletools.oleid.OleID(self.cur_file.src_path) if not olefile.isOleFile(self.cur_file.src_path): # Manual processing, may already count as suspicious try: ole = olefile.OleFileIO(self.cur_file.src_path, raise_defects=olefile.DEFECT_INCORRECT) except: self.cur_file.add_log_details('not_parsable', True) self.cur_file.make_dangerous() if ole.parsing_issues: self.cur_file.add_log_details('parsing_issues', True) self.cur_file.make_dangerous() else: if ole.exists('macros/vba') or ole.exists('Macros') \ or ole.exists('_VBA_PROJECT_CUR') or ole.exists('VBA'): self.cur_file.add_log_details('macro', True) self.cur_file.make_dangerous() else: indicators = oid.check() # Encrypted ban be set by multiple checks on the script if oid.encrypted.value: self.cur_file.add_log_details('encrypted', True) self.cur_file.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.cur_file.add_log_details('macro', True) self.cur_file.make_dangerous() for i in indicators: if i.id == 'ObjectPool' and i.value: # FIXME: Is it suspicious? self.cur_file.add_log_details('objpool', True) elif i.id == 'flash' and i.value: self.cur_file.add_log_details('flash', True) self.cur_file.make_dangerous() self._safe_copy() def _ooxml(self): """Processes an ooxml file.""" self.cur_file.add_log_details('processing_type', 'ooxml') try: doc = officedissector.doc.Document(self.cur_file.src_path) except Exception: # Invalid file self.cur_file.make_dangerous() self._safe_copy() 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.cur_file.add_log_details('macro', True) self.cur_file.make_dangerous() if len(doc.features.embedded_controls) > 0: self.cur_file.add_log_details('activex', True) self.cur_file.make_dangerous() if len(doc.features.embedded_objects) > 0: # Exploited by CVE-2014-4114 (OLE) self.cur_file.add_log_details('embedded_obj', True) self.cur_file.make_dangerous() if len(doc.features.embedded_packages) > 0: self.cur_file.add_log_details('embedded_pack', True) self.cur_file.make_dangerous() self._safe_copy() def _libreoffice(self): """Processes a libreoffice file.""" self.cur_file.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.cur_file.src_path, 'r') except: self.cur_file.add_log_details('invalid', True) self.cur_file.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.cur_file.add_log_details('macro', True) self.cur_file.make_dangerous() self._safe_copy() def _pdf(self): """Processes a PDF file.""" self.cur_file.add_log_details('processing_type', 'pdf') xmlDoc = PDFiD(self.cur_file.src_path) oPDFiD = cPDFiD(xmlDoc, True) # TODO: other keywords? if oPDFiD.encrypt.count > 0: self.cur_file.add_log_details('encrypted', True) self.cur_file.make_dangerous() if oPDFiD.js.count > 0 or oPDFiD.javascript.count > 0: self.cur_file.add_log_details('javascript', True) self.cur_file.make_dangerous() if oPDFiD.aa.count > 0 or oPDFiD.openaction.count > 0: self.cur_file.add_log_details('openaction', True) self.cur_file.make_dangerous() if oPDFiD.richmedia.count > 0: self.cur_file.add_log_details('flash', True) self.cur_file.make_dangerous() if oPDFiD.launch.count > 0: self.cur_file.add_log_details('launch', True) self.cur_file.make_dangerous() self._safe_copy() def _archive(self): """Processes an archive using 7zip. The archive is extracted to a temporary directory and self.processdir is called on that directory. The recursive archive depth is increased to protect against archive bombs.""" self.cur_file.add_log_details('processing_type', 'archive') self.cur_file.is_recursive = True self.cur_file.log_string += 'Archive extracted, processing content.' tmpdir = self.cur_file.dst_path + '_temp' self._safe_mkdir(tmpdir) extract_command = '{} -p1 x "{}" -o"{}" -bd -aoa'.format(SEVENZ_PATH, self.cur_file.src_path, tmpdir) self._run_process(extract_command) self.recursive_archive_depth += 1 self.logger.tree(tmpdir) self.processdir(tmpdir, self.cur_file.dst_path) self.recursive_archive_depth -= 1 self._safe_rmtree(tmpdir) def _handle_archivebomb(self, src_dir): self.cur_file.make_dangerous() self.cur_file.add_log_details('Archive Bomb', True) self.log_name.warning('ARCHIVE BOMB.') self.log_name.warning('The content of the archive contains recursively other archives.') self.log_name.warning('This is a bad sign so the archive is not extracted to the destination key.') self._safe_rmtree(src_dir) if src_dir.endswith('_temp'): bomb_path = src_dir[:-len('_temp')] self._safe_remove(bomb_path) def _unknown_app(self): """Processes an unknown file.""" self.cur_file.make_unknown() self._safe_copy() def _binary_app(self): """Processses an unknown binary file.""" self.cur_file.make_binary() self._safe_copy() ####################### # Metadata extractors def _metadata_exif(self, metadata_file_path): img = open(self.cur_file.src_path, 'rb') tags = None try: tags = exifread.process_file(img, debug=True) except Exception as e: print("Error while trying to grab full metadata for file {}; retrying for partial data.".format(self.cur_file.src_path)) print(e) if tags is None: try: tags = exifread.process_file(img, debug=True) except Exception as e: print("Failed to get any metadata for file {}.".format(self.cur_file.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 if isinstance(value, str): printable = value else: printable = str(value) with open(metadata_file_path, 'w+') as metadata_file: metadata_file.write("Key: {}\tValue: {}\n".format(tag, printable)) self.cur_file.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.cur_file.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.cur_file.add_log_details('metadata', 'png') img.close() # Catch decompression bombs except Exception as e: print("Caught exception processing metadata for {}".format(self.cur_file.src_path)) print(e) self.cur_file.make_dangerous() self._safe_copy() return False def extract_metadata(self): metadata_file_path = self.cur_file.create_metadata_file(".metadata.txt") mt = self.cur_file.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.cur_file.log_string += 'Audio file' self._media_processing() def video(self): """Processes a video.""" self.cur_file.log_string += 'Video file' self._media_processing() def _media_processing(self): """Generic way to process all media files.""" self.cur_file.add_log_details('processing_type', 'media') self._safe_copy() def image(self): """Processes an image. Extracts metadata if metadata is present. Creates a temporary directory, opens the using PIL.Image, saves it to the temporary directory, and copies it to the destination.""" if self.cur_file.has_metadata(): self.extract_metadata() # FIXME make sure this works for png, gif, tiff # Create a temp directory dst_dir, filename = os.path.split(self.cur_file.dst_path) tmpdir = os.path.join(dst_dir, 'temp') tmppath = os.path.join(tmpdir, filename) self._safe_mkdir(tmpdir) # Do our image conversions warnings.simplefilter('error', Image.DecompressionBombWarning) try: imIn = Image.open(self.cur_file.src_path) imOut = Image.frombytes(imIn.mode, imIn.size, imIn.tobytes()) imOut.save(tmppath) # Copy the file back out and cleanup self._safe_copy(tmppath) self._safe_rmtree(tmpdir) # Catch decompression bombs except Exception as e: print("Caught exception (possible decompression bomb?) while translating file {}.".format(self.cur_file.src_path)) print(e) self.cur_file.make_dangerous() self._safe_copy() self.cur_file.log_string += 'Image file' self.cur_file.add_log_details('processing_type', 'image') ####################### def process_file(self, srcpath, dstpath, relative_path): self.cur_file = File(srcpath, dstpath, self.logger) self.log_name.info('Processing {} ({}/{})', relative_path, self.cur_file.main_type, self.cur_file.sub_type) if not self.cur_file.is_dangerous(): self.mime_processing_options.get(self.cur_file.main_type, self.unknown)() else: self._safe_copy() if not self.cur_file.is_recursive: self._print_log() def processdir(self, src_dir=None, dst_dir=None): """Main function coordinating file processing.""" # TODO: do we need defaults here? if src_dir is None: src_dir = self.src_root_dir if dst_dir is None: dst_dir = self.dst_root_dir if self.recursive_archive_depth > 0: self._print_log() if self.recursive_archive_depth >= self.max_recursive_depth: self._handle_archivebomb(src_dir) for srcpath in self._list_all_files(src_dir): dstpath = srcpath.replace(src_dir, dst_dir) relative_path = srcpath.replace(src_dir + '/', '') # which path do we want in the log? self.process_file(srcpath, dstpath, relative_path) if __name__ == '__main__': main(KittenGroomerFileCheck, 'File sanitizer used in CIRCLean. Renames potentially dangerous files.')