basic subscriptions system

python/defusedxml/ElementTree.py

@@ -0,0 +1,112 @@
+# 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.
+"""Defused xml.etree.ElementTree facade
+"""
+from __future__ import print_function, absolute_import
+
+import sys
+from xml.etree.ElementTree import TreeBuilder as _TreeBuilder
+from xml.etree.ElementTree import parse as _parse
+from xml.etree.ElementTree import tostring
+
+from .common import PY3
+
+
+if PY3:
+    import importlib
+else:
+    from xml.etree.ElementTree import XMLParser as _XMLParser
+    from xml.etree.ElementTree import iterparse as _iterparse
+    from xml.etree.ElementTree import ParseError
+
+
+from .common import (DTDForbidden, EntitiesForbidden,
+                     ExternalReferenceForbidden, _generate_etree_functions)
+
+__origin__ = "xml.etree.ElementTree"
+
+
+def _get_py3_cls():
+    """Python 3.3 hides the pure Python code but defusedxml requires it.
+
+    The code is based on test.support.import_fresh_module().
+    """
+    pymodname = "xml.etree.ElementTree"
+    cmodname = "_elementtree"
+
+    pymod = sys.modules.pop(pymodname, None)
+    cmod = sys.modules.pop(cmodname, None)
+
+    sys.modules[cmodname] = None
+    pure_pymod = importlib.import_module(pymodname)
+    if cmod is not None:
+        sys.modules[cmodname] = cmod
+    else:
+        sys.modules.pop(cmodname)
+    sys.modules[pymodname] = pymod
+
+    _XMLParser = pure_pymod.XMLParser
+    _iterparse = pure_pymod.iterparse
+    ParseError = pure_pymod.ParseError
+
+    return _XMLParser, _iterparse, ParseError
+
+
+if PY3:
+    _XMLParser, _iterparse, ParseError = _get_py3_cls()
+
+
+class DefusedXMLParser(_XMLParser):
+
+    def __init__(self, html=0, target=None, encoding=None,
+                 forbid_dtd=False, forbid_entities=True,
+                 forbid_external=True):
+        # Python 2.x old style class
+        _XMLParser.__init__(self, html, target, encoding)
+        self.forbid_dtd = forbid_dtd
+        self.forbid_entities = forbid_entities
+        self.forbid_external = forbid_external
+        if PY3:
+            parser = self.parser
+        else:
+            parser = self._parser
+        if self.forbid_dtd:
+            parser.StartDoctypeDeclHandler = self.defused_start_doctype_decl
+        if self.forbid_entities:
+            parser.EntityDeclHandler = self.defused_entity_decl
+            parser.UnparsedEntityDeclHandler = self.defused_unparsed_entity_decl
+        if self.forbid_external:
+            parser.ExternalEntityRefHandler = self.defused_external_entity_ref_handler
+
+    def defused_start_doctype_decl(self, name, sysid, pubid,
+                                   has_internal_subset):
+        raise DTDForbidden(name, sysid, pubid)
+
+    def defused_entity_decl(self, name, is_parameter_entity, value, base,
+                            sysid, pubid, notation_name):
+        raise EntitiesForbidden(name, value, base, sysid, pubid, notation_name)
+
+    def defused_unparsed_entity_decl(self, name, base, sysid, pubid,
+                                     notation_name):
+        # expat 1.2
+        raise EntitiesForbidden(name, None, base, sysid, pubid, notation_name)
+
+    def defused_external_entity_ref_handler(self, context, base, sysid,
+                                            pubid):
+        raise ExternalReferenceForbidden(context, base, sysid, pubid)
+
+
+# aliases
+XMLTreeBuilder = XMLParse = DefusedXMLParser
+
+parse, iterparse, fromstring = _generate_etree_functions(DefusedXMLParser,
+                                                         _TreeBuilder, _parse,
+                                                         _iterparse)
+XML = fromstring
+
+
+__all__ = ['XML', 'XMLParse', 'XMLTreeBuilder', 'fromstring', 'iterparse',
+           'parse', 'tostring']

python/defusedxml/__init__.py

@@ -0,0 +1,45 @@
+# 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.
+"""Defuse XML bomb denial of service vulnerabilities
+"""
+from __future__ import print_function, absolute_import
+
+from .common import (DefusedXmlException, DTDForbidden, EntitiesForbidden,
+                     ExternalReferenceForbidden, NotSupportedError,
+                     _apply_defusing)
+
+
+def defuse_stdlib():
+    """Monkey patch and defuse all stdlib packages
+
+    :warning: The monkey patch is an EXPERIMETNAL feature.
+    """
+    defused = {}
+
+    from . import cElementTree
+    from . import ElementTree
+    from . import minidom
+    from . import pulldom
+    from . import sax
+    from . import expatbuilder
+    from . import expatreader
+    from . import xmlrpc
+
+    xmlrpc.monkey_patch()
+    defused[xmlrpc] = None
+
+    for defused_mod in [cElementTree, ElementTree, minidom, pulldom, sax,
+                        expatbuilder, expatreader]:
+        stdlib_mod = _apply_defusing(defused_mod)
+        defused[defused_mod] = stdlib_mod
+
+    return defused
+
+
+__version__ = "0.5.0"
+
+__all__ = ['DefusedXmlException', 'DTDForbidden', 'EntitiesForbidden',
+           'ExternalReferenceForbidden', 'NotSupportedError']

python/defusedxml/cElementTree.py

@@ -0,0 +1,30 @@
+# 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.
+"""Defused xml.etree.cElementTree
+"""
+from __future__ import absolute_import
+
+from xml.etree.cElementTree import TreeBuilder as _TreeBuilder
+from xml.etree.cElementTree import parse as _parse
+from xml.etree.cElementTree import tostring
+# iterparse from ElementTree!
+from xml.etree.ElementTree import iterparse as _iterparse
+
+from .ElementTree import DefusedXMLParser
+from .common import _generate_etree_functions
+
+__origin__ = "xml.etree.cElementTree"
+
+
+XMLTreeBuilder = XMLParse = DefusedXMLParser
+
+parse, iterparse, fromstring = _generate_etree_functions(DefusedXMLParser,
+                                                         _TreeBuilder, _parse,
+                                                         _iterparse)
+XML = fromstring
+
+__all__ = ['XML', 'XMLParse', 'XMLTreeBuilder', 'fromstring', 'iterparse',
+           'parse', 'tostring']

python/defusedxml/common.py

@@ -0,0 +1,120 @@
+# 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.
+"""Common constants, exceptions and helpe functions
+"""
+import sys
+
+PY3 = sys.version_info[0] == 3
+
+
+class DefusedXmlException(ValueError):
+    """Base exception
+    """
+
+    def __repr__(self):
+        return str(self)
+
+
+class DTDForbidden(DefusedXmlException):
+    """Document type definition is forbidden
+    """
+
+    def __init__(self, name, sysid, pubid):
+        super(DTDForbidden, self).__init__()
+        self.name = name
+        self.sysid = sysid
+        self.pubid = pubid
+
+    def __str__(self):
+        tpl = "DTDForbidden(name='{}', system_id={!r}, public_id={!r})"
+        return tpl.format(self.name, self.sysid, self.pubid)
+
+
+class EntitiesForbidden(DefusedXmlException):
+    """Entity definition is forbidden
+    """
+
+    def __init__(self, name, value, base, sysid, pubid, notation_name):
+        super(EntitiesForbidden, self).__init__()
+        self.name = name
+        self.value = value
+        self.base = base
+        self.sysid = sysid
+        self.pubid = pubid
+        self.notation_name = notation_name
+
+    def __str__(self):
+        tpl = "EntitiesForbidden(name='{}', system_id={!r}, public_id={!r})"
+        return tpl.format(self.name, self.sysid, self.pubid)
+
+
+class ExternalReferenceForbidden(DefusedXmlException):
+    """Resolving an external reference is forbidden
+    """
+
+    def __init__(self, context, base, sysid, pubid):
+        super(ExternalReferenceForbidden, self).__init__()
+        self.context = context
+        self.base = base
+        self.sysid = sysid
+        self.pubid = pubid
+
+    def __str__(self):
+        tpl = "ExternalReferenceForbidden(system_id='{}', public_id={})"
+        return tpl.format(self.sysid, self.pubid)
+
+
+class NotSupportedError(DefusedXmlException):
+    """The operation is not supported
+    """
+
+
+def _apply_defusing(defused_mod):
+    assert defused_mod is sys.modules[defused_mod.__name__]
+    stdlib_name = defused_mod.__origin__
+    __import__(stdlib_name, {}, {}, ["*"])
+    stdlib_mod = sys.modules[stdlib_name]
+    stdlib_names = set(dir(stdlib_mod))
+    for name, obj in vars(defused_mod).items():
+        if name.startswith("_") or name not in stdlib_names:
+            continue
+        setattr(stdlib_mod, name, obj)
+    return stdlib_mod
+
+
+def _generate_etree_functions(DefusedXMLParser, _TreeBuilder,
+                              _parse, _iterparse):
+    """Factory for functions needed by etree, dependent on whether
+    cElementTree or ElementTree is used."""
+
+    def parse(source, parser=None, forbid_dtd=False, forbid_entities=True,
+              forbid_external=True):
+        if parser is None:
+            parser = DefusedXMLParser(target=_TreeBuilder(),
+                                      forbid_dtd=forbid_dtd,
+                                      forbid_entities=forbid_entities,
+                                      forbid_external=forbid_external)
+        return _parse(source, parser)
+
+    def iterparse(source, events=None, parser=None, forbid_dtd=False,
+                  forbid_entities=True, forbid_external=True):
+        if parser is None:
+            parser = DefusedXMLParser(target=_TreeBuilder(),
+                                      forbid_dtd=forbid_dtd,
+                                      forbid_entities=forbid_entities,
+                                      forbid_external=forbid_external)
+        return _iterparse(source, events, parser)
+
+    def fromstring(text, forbid_dtd=False, forbid_entities=True,
+                   forbid_external=True):
+        parser = DefusedXMLParser(target=_TreeBuilder(),
+                                  forbid_dtd=forbid_dtd,
+                                  forbid_entities=forbid_entities,
+                                  forbid_external=forbid_external)
+        parser.feed(text)
+        return parser.close()
+
+    return parse, iterparse, fromstring

python/defusedxml/expatbuilder.py

@@ -0,0 +1,110 @@
+# 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.
+"""Defused xml.dom.expatbuilder
+"""
+from __future__ import print_function, absolute_import
+
+from xml.dom.expatbuilder import ExpatBuilder as _ExpatBuilder
+from xml.dom.expatbuilder import Namespaces as _Namespaces
+
+from .common import (DTDForbidden, EntitiesForbidden,
+                     ExternalReferenceForbidden)
+
+__origin__ = "xml.dom.expatbuilder"
+
+
+class DefusedExpatBuilder(_ExpatBuilder):
+    """Defused document builder"""
+
+    def __init__(self, options=None, forbid_dtd=False, forbid_entities=True,
+                 forbid_external=True):
+        _ExpatBuilder.__init__(self, options)
+        self.forbid_dtd = forbid_dtd
+        self.forbid_entities = forbid_entities
+        self.forbid_external = forbid_external
+
+    def defused_start_doctype_decl(self, name, sysid, pubid,
+                                   has_internal_subset):
+        raise DTDForbidden(name, sysid, pubid)
+
+    def defused_entity_decl(self, name, is_parameter_entity, value, base,
+                            sysid, pubid, notation_name):
+        raise EntitiesForbidden(name, value, base, sysid, pubid, notation_name)
+
+    def defused_unparsed_entity_decl(self, name, base, sysid, pubid,
+                                     notation_name):
+        # expat 1.2
+        raise EntitiesForbidden(name, None, base, sysid, pubid, notation_name)
+
+    def defused_external_entity_ref_handler(self, context, base, sysid,
+                                            pubid):
+        raise ExternalReferenceForbidden(context, base, sysid, pubid)
+
+    def install(self, parser):
+        _ExpatBuilder.install(self, parser)
+
+        if self.forbid_dtd:
+            parser.StartDoctypeDeclHandler = self.defused_start_doctype_decl
+        if self.forbid_entities:
+            # if self._options.entities:
+            parser.EntityDeclHandler = self.defused_entity_decl
+            parser.UnparsedEntityDeclHandler = self.defused_unparsed_entity_decl
+        if self.forbid_external:
+            parser.ExternalEntityRefHandler = self.defused_external_entity_ref_handler
+
+
+class DefusedExpatBuilderNS(_Namespaces, DefusedExpatBuilder):
+    """Defused document builder that supports namespaces."""
+
+    def install(self, parser):
+        DefusedExpatBuilder.install(self, parser)
+        if self._options.namespace_declarations:
+            parser.StartNamespaceDeclHandler = (
+                self.start_namespace_decl_handler)
+
+    def reset(self):
+        DefusedExpatBuilder.reset(self)
+        self._initNamespaces()
+
+
+def parse(file, namespaces=True, forbid_dtd=False, forbid_entities=True,
+          forbid_external=True):
+    """Parse a document, returning the resulting Document node.
+
+    'file' may be either a file name or an open file object.
+    """
+    if namespaces:
+        build_builder = DefusedExpatBuilderNS
+    else:
+        build_builder = DefusedExpatBuilder
+    builder = build_builder(forbid_dtd=forbid_dtd,
+                            forbid_entities=forbid_entities,
+                            forbid_external=forbid_external)
+
+    if isinstance(file, str):
+        fp = open(file, 'rb')
+        try:
+            result = builder.parseFile(fp)
+        finally:
+            fp.close()
+    else:
+        result = builder.parseFile(file)
+    return result
+
+
+def parseString(string, namespaces=True, forbid_dtd=False,
+                forbid_entities=True, forbid_external=True):
+    """Parse a document from a string, returning the resulting
+    Document node.
+    """
+    if namespaces:
+        build_builder = DefusedExpatBuilderNS
+    else:
+        build_builder = DefusedExpatBuilder
+    builder = build_builder(forbid_dtd=forbid_dtd,
+                            forbid_entities=forbid_entities,
+                            forbid_external=forbid_external)
+    return builder.parseString(string)

python/defusedxml/expatreader.py

@@ -0,0 +1,59 @@
+# 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.
+"""Defused xml.sax.expatreader
+"""
+from __future__ import print_function, absolute_import
+
+from xml.sax.expatreader import ExpatParser as _ExpatParser
+
+from .common import (DTDForbidden, EntitiesForbidden,
+                     ExternalReferenceForbidden)
+
+__origin__ = "xml.sax.expatreader"
+
+
+class DefusedExpatParser(_ExpatParser):
+    """Defused SAX driver for the pyexpat C module."""
+
+    def __init__(self, namespaceHandling=0, bufsize=2 ** 16 - 20,
+                 forbid_dtd=False, forbid_entities=True,
+                 forbid_external=True):
+        _ExpatParser.__init__(self, namespaceHandling, bufsize)
+        self.forbid_dtd = forbid_dtd
+        self.forbid_entities = forbid_entities
+        self.forbid_external = forbid_external
+
+    def defused_start_doctype_decl(self, name, sysid, pubid,
+                                   has_internal_subset):
+        raise DTDForbidden(name, sysid, pubid)
+
+    def defused_entity_decl(self, name, is_parameter_entity, value, base,
+                            sysid, pubid, notation_name):
+        raise EntitiesForbidden(name, value, base, sysid, pubid, notation_name)
+
+    def defused_unparsed_entity_decl(self, name, base, sysid, pubid,
+                                     notation_name):
+        # expat 1.2
+        raise EntitiesForbidden(name, None, base, sysid, pubid, notation_name)
+
+    def defused_external_entity_ref_handler(self, context, base, sysid,
+                                            pubid):
+        raise ExternalReferenceForbidden(context, base, sysid, pubid)
+
+    def reset(self):
+        _ExpatParser.reset(self)
+        parser = self._parser
+        if self.forbid_dtd:
+            parser.StartDoctypeDeclHandler = self.defused_start_doctype_decl
+        if self.forbid_entities:
+            parser.EntityDeclHandler = self.defused_entity_decl
+            parser.UnparsedEntityDeclHandler = self.defused_unparsed_entity_decl
+        if self.forbid_external:
+            parser.ExternalEntityRefHandler = self.defused_external_entity_ref_handler
+
+
+def create_parser(*args, **kwargs):
+    return DefusedExpatParser(*args, **kwargs)

python/defusedxml/lxml.py

@@ -0,0 +1,153 @@
+# 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")

python/defusedxml/minidom.py

@@ -0,0 +1,42 @@
+# 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.
+"""Defused xml.dom.minidom
+"""
+from __future__ import print_function, absolute_import
+
+from xml.dom.minidom import _do_pulldom_parse
+from . import expatbuilder as _expatbuilder
+from . import pulldom as _pulldom
+
+__origin__ = "xml.dom.minidom"
+
+
+def parse(file, parser=None, bufsize=None, forbid_dtd=False,
+          forbid_entities=True, forbid_external=True):
+    """Parse a file into a DOM by filename or file object."""
+    if parser is None and not bufsize:
+        return _expatbuilder.parse(file, forbid_dtd=forbid_dtd,
+                                   forbid_entities=forbid_entities,
+                                   forbid_external=forbid_external)
+    else:
+        return _do_pulldom_parse(_pulldom.parse, (file,),
+                                 {'parser': parser, 'bufsize': bufsize,
+                                  'forbid_dtd': forbid_dtd, 'forbid_entities': forbid_entities,
+                                  'forbid_external': forbid_external})
+
+
+def parseString(string, parser=None, forbid_dtd=False,
+                forbid_entities=True, forbid_external=True):
+    """Parse a file into a DOM from a string."""
+    if parser is None:
+        return _expatbuilder.parseString(string, forbid_dtd=forbid_dtd,
+                                         forbid_entities=forbid_entities,
+                                         forbid_external=forbid_external)
+    else:
+        return _do_pulldom_parse(_pulldom.parseString, (string,),
+                                 {'parser': parser, 'forbid_dtd': forbid_dtd,
+                                  'forbid_entities': forbid_entities,
+                                  'forbid_external': forbid_external})

python/defusedxml/pulldom.py

@@ -0,0 +1,34 @@
+# 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.
+"""Defused xml.dom.pulldom
+"""
+from __future__ import print_function, absolute_import
+
+from xml.dom.pulldom import parse as _parse
+from xml.dom.pulldom import parseString as _parseString
+from .sax import make_parser
+
+__origin__ = "xml.dom.pulldom"
+
+
+def parse(stream_or_string, parser=None, bufsize=None, forbid_dtd=False,
+          forbid_entities=True, forbid_external=True):
+    if parser is None:
+        parser = make_parser()
+        parser.forbid_dtd = forbid_dtd
+        parser.forbid_entities = forbid_entities
+        parser.forbid_external = forbid_external
+    return _parse(stream_or_string, parser, bufsize)
+
+
+def parseString(string, parser=None, forbid_dtd=False,
+                forbid_entities=True, forbid_external=True):
+    if parser is None:
+        parser = make_parser()
+        parser.forbid_dtd = forbid_dtd
+        parser.forbid_entities = forbid_entities
+        parser.forbid_external = forbid_external
+    return _parseString(string, parser)

python/defusedxml/sax.py

@@ -0,0 +1,49 @@
+# 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.
+"""Defused xml.sax
+"""
+from __future__ import print_function, absolute_import
+
+from xml.sax import InputSource as _InputSource
+from xml.sax import ErrorHandler as _ErrorHandler
+
+from . import expatreader
+
+__origin__ = "xml.sax"
+
+
+def parse(source, handler, errorHandler=_ErrorHandler(), forbid_dtd=False,
+          forbid_entities=True, forbid_external=True):
+    parser = make_parser()
+    parser.setContentHandler(handler)
+    parser.setErrorHandler(errorHandler)
+    parser.forbid_dtd = forbid_dtd
+    parser.forbid_entities = forbid_entities
+    parser.forbid_external = forbid_external
+    parser.parse(source)
+
+
+def parseString(string, handler, errorHandler=_ErrorHandler(),
+                forbid_dtd=False, forbid_entities=True,
+                forbid_external=True):
+    from io import BytesIO
+
+    if errorHandler is None:
+        errorHandler = _ErrorHandler()
+    parser = make_parser()
+    parser.setContentHandler(handler)
+    parser.setErrorHandler(errorHandler)
+    parser.forbid_dtd = forbid_dtd
+    parser.forbid_entities = forbid_entities
+    parser.forbid_external = forbid_external
+
+    inpsrc = _InputSource()
+    inpsrc.setByteStream(BytesIO(string))
+    parser.parse(inpsrc)
+
+
+def make_parser(parser_list=[]):
+    return expatreader.create_parser()

python/defusedxml/xmlrpc.py

@@ -0,0 +1,157 @@
+# 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.
+"""Defused xmlrpclib
+
+Also defuses gzip bomb
+"""
+from __future__ import print_function, absolute_import
+
+import io
+
+from .common import (
+    DTDForbidden, EntitiesForbidden, ExternalReferenceForbidden, PY3)
+
+if PY3:
+    __origin__ = "xmlrpc.client"
+    from xmlrpc.client import ExpatParser
+    from xmlrpc import client as xmlrpc_client
+    from xmlrpc import server as xmlrpc_server
+    from xmlrpc.client import gzip_decode as _orig_gzip_decode
+    from xmlrpc.client import GzipDecodedResponse as _OrigGzipDecodedResponse
+else:
+    __origin__ = "xmlrpclib"
+    from xmlrpclib import ExpatParser
+    import xmlrpclib as xmlrpc_client
+    xmlrpc_server = None
+    from xmlrpclib import gzip_decode as _orig_gzip_decode
+    from xmlrpclib import GzipDecodedResponse as _OrigGzipDecodedResponse
+
+try:
+    import gzip
+except ImportError:
+    gzip = None
+
+
+# Limit maximum request size to prevent resource exhaustion DoS
+# Also used to limit maximum amount of gzip decoded data in order to prevent
+# decompression bombs
+# A value of -1 or smaller disables the limit
+MAX_DATA = 30 * 1024 * 1024  # 30 MB
+
+
+def defused_gzip_decode(data, limit=None):
+    """gzip encoded data -> unencoded data
+
+    Decode data using the gzip content encoding as described in RFC 1952
+    """
+    if not gzip:
+        raise NotImplementedError
+    if limit is None:
+        limit = MAX_DATA
+    f = io.BytesIO(data)
+    gzf = gzip.GzipFile(mode="rb", fileobj=f)
+    try:
+        if limit < 0:  # no limit
+            decoded = gzf.read()
+        else:
+            decoded = gzf.read(limit + 1)
+    except IOError:
+        raise ValueError("invalid data")
+    f.close()
+    gzf.close()
+    if limit >= 0 and len(decoded) > limit:
+        raise ValueError("max gzipped payload length exceeded")
+    return decoded
+
+
+class DefusedGzipDecodedResponse(gzip.GzipFile if gzip else object):
+    """a file-like object to decode a response encoded with the gzip
+    method, as described in RFC 1952.
+    """
+
+    def __init__(self, response, limit=None):
+        # response doesn't support tell() and read(), required by
+        # GzipFile
+        if not gzip:
+            raise NotImplementedError
+        self.limit = limit = limit if limit is not None else MAX_DATA
+        if limit < 0:  # no limit
+            data = response.read()
+            self.readlength = None
+        else:
+            data = response.read(limit + 1)
+            self.readlength = 0
+        if limit >= 0 and len(data) > limit:
+            raise ValueError("max payload length exceeded")
+        self.stringio = io.BytesIO(data)
+        gzip.GzipFile.__init__(self, mode="rb", fileobj=self.stringio)
+
+    def read(self, n):
+        if self.limit >= 0:
+            left = self.limit - self.readlength
+            n = min(n, left + 1)
+            data = gzip.GzipFile.read(self, n)
+            self.readlength += len(data)
+            if self.readlength > self.limit:
+                raise ValueError("max payload length exceeded")
+            return data
+        else:
+            return gzip.GzipFile.read(self, n)
+
+    def close(self):
+        gzip.GzipFile.close(self)
+        self.stringio.close()
+
+
+class DefusedExpatParser(ExpatParser):
+
+    def __init__(self, target, forbid_dtd=False, forbid_entities=True,
+                 forbid_external=True):
+        ExpatParser.__init__(self, target)
+        self.forbid_dtd = forbid_dtd
+        self.forbid_entities = forbid_entities
+        self.forbid_external = forbid_external
+        parser = self._parser
+        if self.forbid_dtd:
+            parser.StartDoctypeDeclHandler = self.defused_start_doctype_decl
+        if self.forbid_entities:
+            parser.EntityDeclHandler = self.defused_entity_decl
+            parser.UnparsedEntityDeclHandler = self.defused_unparsed_entity_decl
+        if self.forbid_external:
+            parser.ExternalEntityRefHandler = self.defused_external_entity_ref_handler
+
+    def defused_start_doctype_decl(self, name, sysid, pubid,
+                                   has_internal_subset):
+        raise DTDForbidden(name, sysid, pubid)
+
+    def defused_entity_decl(self, name, is_parameter_entity, value, base,
+                            sysid, pubid, notation_name):
+        raise EntitiesForbidden(name, value, base, sysid, pubid, notation_name)
+
+    def defused_unparsed_entity_decl(self, name, base, sysid, pubid,
+                                     notation_name):
+        # expat 1.2
+        raise EntitiesForbidden(name, None, base, sysid, pubid, notation_name)
+
+    def defused_external_entity_ref_handler(self, context, base, sysid,
+                                            pubid):
+        raise ExternalReferenceForbidden(context, base, sysid, pubid)
+
+
+def monkey_patch():
+    xmlrpc_client.FastParser = DefusedExpatParser
+    xmlrpc_client.GzipDecodedResponse = DefusedGzipDecodedResponse
+    xmlrpc_client.gzip_decode = defused_gzip_decode
+    if xmlrpc_server:
+        xmlrpc_server.gzip_decode = defused_gzip_decode
+
+
+def unmonkey_patch():
+    xmlrpc_client.FastParser = None
+    xmlrpc_client.GzipDecodedResponse = _OrigGzipDecodedResponse
+    xmlrpc_client.gzip_decode = _orig_gzip_decode
+    if xmlrpc_server:
+        xmlrpc_server.gzip_decode = _orig_gzip_decode