basic subscriptions system

1 files changed, 153 insertions, 0 deletions

diff --git a/python/defusedxml/lxml.py b/python/defusedxml/lxml.py
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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")