import logging import os import re import zipfile from typing import Dict, Set, Pattern, Tuple, Any import xml.etree.ElementTree as ET # type: ignore from .archive import ZipParser # pylint: disable=line-too-long # Make pyflakes happy assert Set assert Pattern def _parse_xml(full_path: str) -> Tuple[ET.ElementTree, Dict[str, str]]: """ This function parses XML, with namespace support. """ namespace_map = dict() for _, (key, value) in ET.iterparse(full_path, ("start-ns", )): # The ns[0-9]+ namespaces are reserved for internal usage, so # we have to use an other nomenclature. if re.match('^ns[0-9]+$', key, re.I): # pragma: no cover key = 'mat' + key[2:] namespace_map[key] = value ET.register_namespace(key, value) return ET.parse(full_path), namespace_map def _sort_xml_attributes(full_path: str) -> bool: """ Sort xml attributes lexicographically, because it's possible to fingerprint producers (MS Office, Libreoffice, …) since they are all using different orders. """ tree = ET.parse(full_path) for c in tree.getroot(): c[:] = sorted(c, key=lambda child: (child.tag, child.get('desc'))) tree.write(full_path, xml_declaration=True) return True class MSOfficeParser(ZipParser): """ The methods modifying XML documents are usually doing so in two loops: 1. finding the tag/attributes to remove; 2. actually editing the document since it's tricky to modify the XML while iterating on it. """ mimetypes = { 'application/vnd.openxmlformats-officedocument.wordprocessingml.document', 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet', 'application/vnd.openxmlformats-officedocument.presentationml.presentation' } content_types_to_keep = { 'application/vnd.openxmlformats-officedocument.wordprocessingml.endnotes+xml', # /word/endnotes.xml 'application/vnd.openxmlformats-officedocument.wordprocessingml.footnotes+xml', # /word/footnotes.xml 'application/vnd.openxmlformats-officedocument.extended-properties+xml', # /docProps/app.xml 'application/vnd.openxmlformats-officedocument.wordprocessingml.document.main+xml', # /word/document.xml 'application/vnd.openxmlformats-officedocument.wordprocessingml.fontTable+xml', # /word/fontTable.xml 'application/vnd.openxmlformats-officedocument.wordprocessingml.footer+xml', # /word/footer.xml 'application/vnd.openxmlformats-officedocument.wordprocessingml.header+xml', # /word/header.xml 'application/vnd.openxmlformats-officedocument.wordprocessingml.styles+xml', # /word/styles.xml 'application/vnd.openxmlformats-package.core-properties+xml', # /docProps/core.xml # Do we want to keep the following ones? 'application/vnd.openxmlformats-officedocument.wordprocessingml.settings+xml', } def __init__(self, filename): super().__init__(filename) self.files_to_keep = set(map(re.compile, { # type: ignore r'^\[Content_Types\]\.xml$', r'^_rels/\.rels$', r'^word/_rels/document\.xml\.rels$', r'^word/_rels/footer[0-9]*\.xml\.rels$', r'^word/_rels/header[0-9]*\.xml\.rels$', # https://msdn.microsoft.com/en-us/library/dd908153(v=office.12).aspx r'^word/stylesWithEffects\.xml$', })) self.files_to_omit = set(map(re.compile, { # type: ignore r'^customXml/', r'webSettings\.xml$', r'^docProps/custom\.xml$', r'^word/printerSettings/', r'^word/theme', r'^word/people\.xml$', r'^word/numbering\.xml$', # we have an allowlist in self.files_to_keep, # so we can trash everything else r'^word/_rels/', })) if self.__fill_files_to_keep_via_content_types() is False: raise ValueError def __fill_files_to_keep_via_content_types(self) -> bool: """ There is a suer-handy `[Content_Types].xml` file in MS Office archives, describing what each other file contains. The self.content_types_to_keep member contains a type allowlist, so we're using it to fill the self.files_to_keep one. """ with zipfile.ZipFile(self.filename) as zin: if '[Content_Types].xml' not in zin.namelist(): return False xml_data = zin.read('[Content_Types].xml') self.content_types = dict() # type: Dict[str, str] try: tree = ET.fromstring(xml_data) except ET.ParseError: return False for c in tree: if 'PartName' not in c.attrib or 'ContentType' not in c.attrib: continue elif c.attrib['ContentType'] in self.content_types_to_keep: fname = c.attrib['PartName'][1:] # remove leading `/` re_fname = re.compile('^' + re.escape(fname) + '$') self.files_to_keep.add(re_fname) # type: ignore return True @staticmethod def __remove_rsid(full_path: str) -> bool: """ The method will remove "revision session ID". We're using '}rsid' instead of proper parsing, since rsid can have multiple forms, like `rsidRDefault`, `rsidR`, `rsids`, … For more details, see - https://msdn.microsoft.com/en-us/library/office/documentformat.openxml.wordprocessing.previoussectionproperties.rsidrpr.aspx - https://blogs.msdn.microsoft.com/brian_jones/2006/12/11/whats-up-with-all-those-rsids/ """ try: tree, namespace = _parse_xml(full_path) except ET.ParseError as e: logging.error("Unable to parse %s: %s", full_path, e) return False # rsid, tags or attributes, are always under the `w` namespace if 'w' not in namespace.keys(): return True parent_map = {c:p for p in tree.iter() for c in p} elements_to_remove = list() for item in tree.iterfind('.//', namespace): if '}rsid' in item.tag.strip().lower(): # rsid as tag elements_to_remove.append(item) continue for key in list(item.attrib.keys()): # rsid as attribute if '}rsid' in key.lower(): del item.attrib[key] for element in elements_to_remove: parent_map[element].remove(element) tree.write(full_path, xml_declaration=True) return True @staticmethod def __remove_nsid(full_path: str) -> bool: """ nsid are random identifiers that can be used to ease the merging of some components of a document. They can also be used for fingerprinting. See the spec for more details: https://docs.microsoft.com/en-us/dotnet/api/documentformat.openxml.wordprocessing.nsid?view=openxml-2.8.1 """ try: tree, namespace = _parse_xml(full_path) except ET.ParseError as e: # pragma: no cover logging.error("Unable to parse %s: %s", full_path, e) return False # The nsid tag is always under the `w` namespace if 'w' not in namespace.keys(): return True parent_map = {c:p for p in tree.iter() for c in p} elements_to_remove = list() for element in tree.iterfind('.//w:nsid', namespace): elements_to_remove.append(element) for element in elements_to_remove: parent_map[element].remove(element) tree.write(full_path, xml_declaration=True) return True @staticmethod def __remove_revisions(full_path: str) -> bool: try: tree, namespace = _parse_xml(full_path) except ET.ParseError as e: logging.error("Unable to parse %s: %s", full_path, e) return False # Revisions are either deletions (`w:del`) or # insertions (`w:ins`) del_presence = tree.find('.//w:del', namespace) ins_presence = tree.find('.//w:ins', namespace) if del_presence is None and ins_presence is None: return True # No revisions are present parent_map = {c:p for p in tree.iter() for c in p} elements_del = list() for element in tree.iterfind('.//w:del', namespace): elements_del.append(element) for element in elements_del: parent_map[element].remove(element) elements_ins = list() for element in tree.iterfind('.//w:ins', namespace): for position, item in enumerate(tree.iter()): # pragma: no cover if item == element: for children in element.iterfind('./*'): elements_ins.append((element, position, children)) break for (element, position, children) in elements_ins: parent_map[element].insert(position, children) parent_map[element].remove(element) tree.write(full_path, xml_declaration=True) return True def __remove_content_type_members(self, full_path: str) -> bool: """ The method will remove the dangling references form the [Content_Types].xml file, since MS office doesn't like them """ try: tree, namespace = _parse_xml(full_path) except ET.ParseError as e: # pragma: no cover logging.error("Unable to parse %s: %s", full_path, e) return False if len(namespace.items()) != 1: return False # there should be only one namespace for Types removed_fnames = set() with zipfile.ZipFile(self.filename) as zin: for fname in [item.filename for item in zin.infolist()]: for file_to_omit in self.files_to_omit: if file_to_omit.search(fname): matches = map(lambda r: r.search(fname), self.files_to_keep) if any(matches): # the file is in the allowlist continue removed_fnames.add(fname) break root = tree.getroot() for item in root.findall('{%s}Override' % namespace['']): name = item.attrib['PartName'][1:] # remove the leading '/' if name in removed_fnames: root.remove(item) tree.write(full_path, xml_declaration=True) return True def _specific_cleanup(self, full_path: str) -> bool: # pylint: disable=too-many-return-statements if os.stat(full_path).st_size == 0: # Don't process empty files return True if not full_path.endswith('.xml'): return True if full_path.endswith('/[Content_Types].xml'): # this file contains references to files that we might # remove, and MS Office doesn't like dangling references if self.__remove_content_type_members(full_path) is False: return False elif full_path.endswith('/word/document.xml'): # this file contains the revisions if self.__remove_revisions(full_path) is False: return False elif full_path.endswith('/docProps/app.xml'): # This file must be present and valid, # so we're removing as much as we can. with open(full_path, 'wb') as f: f.write(b'') f.write(b'') f.write(b'') elif full_path.endswith('/docProps/core.xml'): # This file must be present and valid, # so we're removing as much as we can. with open(full_path, 'wb') as f: f.write(b'') f.write(b'') f.write(b'') if self.__remove_rsid(full_path) is False: return False if self.__remove_nsid(full_path) is False: return False # pragma: no cover try: _sort_xml_attributes(full_path) except ET.ParseError as e: # pragma: no cover logging.error("Unable to parse %s: %s", full_path, e) return False # This is awful, I'm sorry. # # Microsoft Office isn't happy when we have the `mc:Ignorable` # tag containing namespaces that aren't present in the xml file, # so instead of trying to remove this specific tag with etree, # we're removing it, with a regexp. # # Since we're the ones producing this file, via the call to # _sort_xml_attributes, there won't be any "funny tricks". # Worst case, the tag isn't present, and everything is fine. # # see: https://docs.microsoft.com/en-us/dotnet/framework/wpf/advanced/mc-ignorable-attribute with open(full_path, 'rb') as f: text = f.read() out = re.sub(b'mc:Ignorable="[^"]*"', b'', text, 1) with open(full_path, 'wb') as f: f.write(out) return True def _specific_get_meta(self, full_path: str, file_path: str) -> Dict[str, Any]: """ Yes, I know that parsing xml with regexp ain't pretty, be my guest and fix it if you want. """ if not file_path.startswith('docProps/') or not file_path.endswith('.xml'): return {} with open(full_path, encoding='utf-8') as f: try: results = re.findall(r"<(.+)>(.+)", f.read(), re.I|re.M) return {k:v for (k, v) in results} except (TypeError, UnicodeDecodeError): # We didn't manage to parse the xml file return {file_path: 'harmful content', } class LibreOfficeParser(ZipParser): mimetypes = { 'application/vnd.oasis.opendocument.text', 'application/vnd.oasis.opendocument.spreadsheet', 'application/vnd.oasis.opendocument.presentation', 'application/vnd.oasis.opendocument.graphics', 'application/vnd.oasis.opendocument.chart', 'application/vnd.oasis.opendocument.formula', 'application/vnd.oasis.opendocument.image', } def __init__(self, filename): super().__init__(filename) self.files_to_keep = set(map(re.compile, { # type: ignore r'^META-INF/manifest\.xml$', r'^content\.xml$', r'^manifest\.rdf$', r'^mimetype$', r'^settings\.xml$', r'^styles\.xml$', })) self.files_to_omit = set(map(re.compile, { # type: ignore r'^meta\.xml$', r'^Configurations2/', r'^Thumbnails/', })) @staticmethod def __remove_revisions(full_path: str) -> bool: try: tree, namespace = _parse_xml(full_path) except ET.ParseError as e: logging.error("Unable to parse %s: %s", full_path, e) return False if 'office' not in namespace.keys(): # no revisions in the current file return True for text in tree.getroot().iterfind('.//office:text', namespace): for changes in text.iterfind('.//text:tracked-changes', namespace): text.remove(changes) tree.write(full_path, xml_declaration=True) return True def _specific_cleanup(self, full_path: str) -> bool: if os.stat(full_path).st_size == 0: # Don't process empty files return True if os.path.basename(full_path).endswith('.xml'): if os.path.basename(full_path) == 'content.xml': if self.__remove_revisions(full_path) is False: return False try: _sort_xml_attributes(full_path) except ET.ParseError as e: logging.error("Unable to parse %s: %s", full_path, e) return False return True def _specific_get_meta(self, full_path: str, file_path: str) -> Dict[str, Any]: """ Yes, I know that parsing xml with regexp ain't pretty, be my guest and fix it if you want. """ if file_path != 'meta.xml': return {} with open(full_path, encoding='utf-8') as f: try: results = re.findall(r"<((?:meta|dc|cp).+?)[^>]*>(.+)", f.read(), re.I|re.M) return {k:v for (k, v) in results} except (TypeError, UnicodeDecodeError): # We didn't manage to parse the xml file # We didn't manage to parse the xml file return {file_path: 'harmful content', }