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# defusedxml
#
# Copyright (c) 2013 by Christian Heimes <christian@python.org>
# Licensed to PSF under a Contributor Agreement.
# See http://www.python.org/psf/license for licensing details.
"""Example code for lxml.etree protection
The code has NO protection against decompression bombs.
"""
from __future__ import print_function, absolute_import
import threading
from lxml import etree as _etree
from .common import DTDForbidden, EntitiesForbidden, NotSupportedError
LXML3 = _etree.LXML_VERSION[0] >= 3
__origin__ = "lxml.etree"
tostring = _etree.tostring
class RestrictedElement(_etree.ElementBase):
"""A restricted Element class that filters out instances of some classes
"""
__slots__ = ()
# blacklist = (etree._Entity, etree._ProcessingInstruction, etree._Comment)
blacklist = _etree._Entity
def _filter(self, iterator):
blacklist = self.blacklist
for child in iterator:
if isinstance(child, blacklist):
continue
yield child
def __iter__(self):
iterator = super(RestrictedElement, self).__iter__()
return self._filter(iterator)
def iterchildren(self, tag=None, reversed=False):
iterator = super(RestrictedElement, self).iterchildren(
tag=tag, reversed=reversed)
return self._filter(iterator)
def iter(self, tag=None, *tags):
iterator = super(RestrictedElement, self).iter(tag=tag, *tags)
return self._filter(iterator)
def iterdescendants(self, tag=None, *tags):
iterator = super(RestrictedElement,
self).iterdescendants(tag=tag, *tags)
return self._filter(iterator)
def itersiblings(self, tag=None, preceding=False):
iterator = super(RestrictedElement, self).itersiblings(
tag=tag, preceding=preceding)
return self._filter(iterator)
def getchildren(self):
iterator = super(RestrictedElement, self).__iter__()
return list(self._filter(iterator))
def getiterator(self, tag=None):
iterator = super(RestrictedElement, self).getiterator(tag)
return self._filter(iterator)
class GlobalParserTLS(threading.local):
"""Thread local context for custom parser instances
"""
parser_config = {
'resolve_entities': False,
# 'remove_comments': True,
# 'remove_pis': True,
}
element_class = RestrictedElement
def createDefaultParser(self):
parser = _etree.XMLParser(**self.parser_config)
element_class = self.element_class
if self.element_class is not None:
lookup = _etree.ElementDefaultClassLookup(element=element_class)
parser.set_element_class_lookup(lookup)
return parser
def setDefaultParser(self, parser):
self._default_parser = parser
def getDefaultParser(self):
parser = getattr(self, "_default_parser", None)
if parser is None:
parser = self.createDefaultParser()
self.setDefaultParser(parser)
return parser
_parser_tls = GlobalParserTLS()
getDefaultParser = _parser_tls.getDefaultParser
def check_docinfo(elementtree, forbid_dtd=False, forbid_entities=True):
"""Check docinfo of an element tree for DTD and entity declarations
The check for entity declarations needs lxml 3 or newer. lxml 2.x does
not support dtd.iterentities().
"""
docinfo = elementtree.docinfo
if docinfo.doctype:
if forbid_dtd:
raise DTDForbidden(docinfo.doctype,
docinfo.system_url,
docinfo.public_id)
if forbid_entities and not LXML3:
# lxml < 3 has no iterentities()
raise NotSupportedError("Unable to check for entity declarations "
"in lxml 2.x")
if forbid_entities:
for dtd in docinfo.internalDTD, docinfo.externalDTD:
if dtd is None:
continue
for entity in dtd.iterentities():
raise EntitiesForbidden(entity.name, entity.content, None,
None, None, None)
def parse(source, parser=None, base_url=None, forbid_dtd=False,
forbid_entities=True):
if parser is None:
parser = getDefaultParser()
elementtree = _etree.parse(source, parser, base_url=base_url)
check_docinfo(elementtree, forbid_dtd, forbid_entities)
return elementtree
def fromstring(text, parser=None, base_url=None, forbid_dtd=False,
forbid_entities=True):
if parser is None:
parser = getDefaultParser()
rootelement = _etree.fromstring(text, parser, base_url=base_url)
elementtree = rootelement.getroottree()
check_docinfo(elementtree, forbid_dtd, forbid_entities)
return rootelement
XML = fromstring
def iterparse(*args, **kwargs):
raise NotSupportedError("defused lxml.etree.iterparse not available")
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