Philipp Hörist pushed to branch master at gajim / python-nbxmpp
Commits:
70de8004 by Philipp Hörist at 2018-11-12T20:22:14Z
Harden parser against xml vulnerabilities
- - - - -
5 changed files:
- nbxmpp/dispatcher_nb.py
- nbxmpp/simplexml.py
- + test/__init__.py
- test/runtests.py
- + test/unit/test_xml_vulnerability.py
Changes:
=====================================
nbxmpp/dispatcher_nb.py
=====================================
@@ -235,8 +235,9 @@ class XMPPDispatcher(PlugIn):
if self.Stream and self.Stream.has_received_endtag():
self._owner.disconnect(self.Stream.streamError)
return 0
- except ExpatError:
+ except ExpatError as error:
log.error('Invalid XML received from server. Forcing disconnect.')
+ log.error(error)
self._owner.Connection.disconnect()
return 0
except ValueError as e:
=====================================
nbxmpp/simplexml.py
=====================================
@@ -22,6 +22,7 @@ from __future__ import unicode_literals
import sys
import xml.parsers.expat
+from xml.parsers.expat import ExpatError
import logging
log = logging.getLogger('nbxmpp.simplexml')
@@ -566,10 +567,17 @@ class NodeBuilder(object):
"""
log.debug("Preparing to handle incoming XML stream.")
self._parser = xml.parsers.expat.ParserCreate()
+ self._parser.UseForeignDTD(False)
self._parser.StartElementHandler = self.starttag
self._parser.EndElementHandler = self.endtag
self._parser.StartNamespaceDeclHandler = self.handle_namespace_start
self._parser.CharacterDataHandler = self.handle_cdata
+ self._parser.StartDoctypeDeclHandler = self.handle_invalid_xmpp_element
+ self._parser.EntityDeclHandler = self.handle_invalid_xmpp_element
+ self._parser.CommentHandler = self.handle_invalid_xmpp_element
+ self._parser.ExternalEntityRefHandler =
self.handle_invalid_xmpp_element
+ self._parser.AttlistDeclHandler = self.handle_invalid_xmpp_element
+ self._parser.ProcessingInstructionHandler =
self.handle_invalid_xmpp_element
self._parser.buffer_text = True
self.Parse = self._parser.Parse
@@ -673,6 +681,10 @@ class NodeBuilder(object):
self.data_buffer = [data]
self.last_is_data = 1
+ @staticmethod
+ def handle_invalid_xmpp_element(*args):
+ raise ExpatError('Found invalid xmpp stream element: %s' % str(args))
+
def handle_namespace_start(self, prefix, uri):
"""
XML Parser callback. Used internally
=====================================
test/__init__.py
=====================================
=====================================
test/runtests.py
=====================================
@@ -38,6 +38,7 @@ modules = ( 'unit.test_xmpp_dispatcher_nb',
'unit.test_xmpp_smacks',
#'unit.test_xmpp_client_nb', gajim.org only supports TLS/SSL
connections
'unit.test_xmpp_transports_nb2',
+ 'unit.test_xml_vulnerability',
)
nb_errors = 0
=====================================
test/unit/test_xml_vulnerability.py
=====================================
@@ -0,0 +1,73 @@
+import unittest
+from unittest.mock import Mock
+
+from nbxmpp import dispatcher_nb
+
+
+class XMLVulnerability(unittest.TestCase):
+
+ def setUp(self):
+ self.client = Mock()
+ self.client.Connection = Mock()
+ self.dispatcher = dispatcher_nb.XMPPDispatcher()
+ self.dispatcher.PlugIn(self.client)
+ self.dispatcher.StreamInit()
+
+ def tearDown(self):
+ self.dispatcher = None
+ self.client = None
+
+ def test_exponential_entity_expansion(self):
+ bomb = """<?xml version="1.0" encoding="utf-8"?>
+ <!DOCTYPE bomb [
+ <!ENTITY a "test">
+ <!ENTITY b "&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;">
+ <!ENTITY c "&b;&b;&b;&b;&b;&b;&b;&b;&b;&b;&b;&b;&b;&b;&b;&b;">
+ ]>
+ <bomb>&c;</bomb>"""
+
+ self.dispatcher.ProcessNonBlocking(bomb)
+ self.client.Connection.disconnect.assert_called()
+
+ def test_quadratic_blowup(self):
+ bomb = """<?xml version="1.0" encoding="utf-8"?>
+ <!DOCTYPE bomb [
+ <!ENTITY a "xxxxxxx... a couple of ten thousand chars">
+ ]>
+ <bomb>&a;&a;&a;... repeat</bomb>"""
+
+ self.dispatcher.ProcessNonBlocking(bomb)
+ self.client.Connection.disconnect.assert_called()
+
+ def test_external_entity_expansion(self):
+ bomb = """<?xml version="1.0" encoding="utf-8"?>
+ <!DOCTYPE external [
+ <!ENTITY ee SYSTEM "http://www.python.org/some.xml";>
+ ]>
+ <root>ⅇ</root>"""
+
+ self.dispatcher.ProcessNonBlocking(bomb)
+ self.client.Connection.disconnect.assert_called()
+
+ def test_external_local_entity_expansion(self):
+ bomb = """<?xml version="1.0" encoding="utf-8"?>
+ <stream:stream xmlns:stream='http://etherx.jabber.org/streams'
xmlns='jabber:client'>
+ <!DOCTYPE external [
+ <!ENTITY ee SYSTEM "file:///PATH/TO/simple.xml">
+ ]>
+ <root>ⅇ</root>"""
+
+ self.dispatcher.ProcessNonBlocking(bomb)
+ self.client.Connection.disconnect.assert_called()
+
+ def test_dtd_retrival(self):
+ bomb = """<?xml version="1.0" encoding="utf-8"?>
+ <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
+ "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd";>
+ <html>
+ <head/>
+ <body>text</body>
+ </html>"""
+
+ self.dispatcher.ProcessNonBlocking(bomb)
+ self.client.Connection.disconnect.assert_called()
View it on GitLab:
https://dev.gajim.org/gajim/python-nbxmpp/commit/70de8004a84ef62e0e2c25bc1c882e92a9a89e94
--
View it on GitLab:
https://dev.gajim.org/gajim/python-nbxmpp/commit/70de8004a84ef62e0e2c25bc1c882e92a9a89e94
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