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PyCIRCLean/bin/filecheck.py

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#!/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/<subtype>')
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
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:
self.make_dangerous('no mimetype')
if not self.has_extension:
self.make_dangerous('no extension')
if self.extension in Config.malicious_exts:
self.make_dangerous('malicious_extension')
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:
# LOG: improve this string
self.make_dangerous('expected_mimetyped')
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:
# LOG: improve this string
self.make_dangerous('expected extensions')
def check(self):
self._check_dangerous()
if self.has_extension:
self._check_extension()
if self.has_mimetype:
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
@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:
symlink_path = self.get_property('symlink')
self.add_file_string('Symlink to {}'.format(symlink_path))
else:
self.add_file_string('Inode file')
self.should_copy = False
def unknown(self):
"""Main type should never be unknown."""
self.add_file_string('Unknown file')
self.should_copy = False
def example(self):
"""Used in examples, should never be returned by libmagic."""
self.add_file_string('Example file')
self.should_copy = False
def multipart(self):
"""Used in web apps, should never be returned by libmagic"""
self.add_file_string('Multipart file')
self.should_copy = False
# ##### Treated as malicious, no reason to have it on a USB key ######
def message(self):
"""Process a message file."""
self.add_file_string('Message file')
self.make_dangerous('Message file')
def model(self):
"""Process a model file."""
self.add_file_string('Model file')
self.make_dangerous('Model file')
# ##### 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.add_file_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.add_file_string('OOXML File')
self._ooxml()
return
self.add_file_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:
# TODO: should this return a value?
method()
self.add_file_string('Application file')
return
self.add_file_string('Unknown Application file')
self._unknown_app()
def _executables(self):
"""Processes an executable file."""
# LOG: change this property
self.set_property('processing_type', 'executable')
self.make_dangerous('executable')
def _winoffice(self):
"""Processes a winoffice file using olefile/oletools."""
# LOG: change this property
self.set_property('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.make_dangerous('not parsable')
if ole.parsing_issues:
self.make_dangerous('parsing issues')
else:
if ole.exists('macros/vba') or ole.exists('Macros') \
or ole.exists('_VBA_PROJECT_CUR') or ole.exists('VBA'):
self.make_dangerous('macro')
else:
indicators = oid.check()
# Encrypted can be set by multiple checks on the script
if oid.encrypted.value:
self.make_dangerous('encrypted')
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.make_dangerous('macro')
for i in indicators:
if i.id == 'ObjectPool' and i.value:
# TODO: Is it suspicious?
self.set_property('objpool', True)
elif i.id == 'flash' and i.value:
self.make_dangerous('flash')
def _ooxml(self):
"""Processes an ooxml file."""
self.set_property('processing_type', 'ooxml')
try:
doc = officedissector.doc.Document(self.src_path)
except Exception:
self.make_dangerous('invalid ooxml file')
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.make_dangerous('macro')
if len(doc.features.embedded_controls) > 0:
self.make_dangerous('activex')
if len(doc.features.embedded_objects) > 0:
# Exploited by CVE-2014-4114 (OLE)
self.make_dangerous('embedded obj')
if len(doc.features.embedded_packages) > 0:
self.make_dangerous('embedded pack')
def _libreoffice(self):
"""Processes a libreoffice file."""
self.set_property('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.make_dangerous('invalid libreoffice file')
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.make_dangerous('macro')
def _pdf(self):
"""Processes a PDF file."""
self.set_property('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.make_dangerous('encrypted pdf')
if oPDFiD.js.count > 0 or oPDFiD.javascript.count > 0:
self.make_dangerous('pdf with javascript')
if oPDFiD.aa.count > 0 or oPDFiD.openaction.count > 0:
self.make_dangerous('openaction')
if oPDFiD.richmedia.count > 0:
self.make_dangerous('flash')
if oPDFiD.launch.count > 0:
self.make_dangerous('launch')
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.set_property('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:
self.add_error(e, "Error while trying to grab full metadata for file {}; retrying for partial data.".format(self.src_path))
if tags is None:
try:
tags = exifread.process_file(img, debug=True)
except Exception as e:
self.add_error(e, "Failed to get any metadata for file {}.".format(self.src_path))
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.set_property('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.set_property('metadata', 'png')
img.close()
# Catch decompression bombs
except Exception as e:
self.add_error(e, "Caught exception processing metadata for {}".format(self.src_path))
self.make_dangerous('exception processing metadata')
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.set_property('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
self.add_error(e, "Caught exception (possible decompression bomb?) while translating file {}.".format(self.src_path))
self.make_dangerous()
self.add_file_string('Image file')
self.set_property('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: what's the purpose of this write log?:
# if self.recursive_archive_depth > 0:
# self.write_log()
# We're writing the log here because...
# How exactly does the workflow work with an archive?
for srcpath in self.list_all_files(src_dir):
dstpath = srcpath.replace(src_dir, dst_dir)
# TODO: Can we clean up the way we handle relative_path?
# Relative path is here so that when we print files in the log it
# shows only the file's path. Should we just pass it to the logger
# when we create it? Or let the logger figure it out?
# relative_path = srcpath.replace(src_dir + '/', '')
self.cur_file = File(srcpath, dstpath, self.logger)
self.process_file(self.cur_file)
def process_file(self, file):
file.check()
if file.is_recursive:
self.process_archive(file)
elif file.should_copy:
file.safe_copy()
file.set_property('copied', True)
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('Archive bomb')
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.')
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