Re: crash its not work hiks hikss...

[Daniel Miller <bonsaiviking () gmail com>]

Here's another option, this time as a patch to Ndiff, which is similarly
affected. The logic works the same, except this one doesn't care about
finding a valid DTD, but instead returns an "empty file," short-circuiting
the DTD parsing:

diff --git a/ndiff/ndiff.py b/ndiff/ndiff.py
index 28e99da..a8706f2 100755
--- a/ndiff/ndiff.py
+++ b/ndiff/ndiff.py
@@ -21,12 +21,22 @@ import time
 import xml.sax
 import xml.sax.saxutils
 import xml.dom.minidom
+from StringIO import StringIO

 verbose = False

 NDIFF_XML_VERSION = u"1"


+class OverrideEntityResolver(xml.sax.handler.EntityResolver):
+    """This class overrides the default behavior of xml.sax to download
+    remote DTDs, instead returning blank strings"""
+    empty = StringIO()
+
+    def resolveEntity(self, publicId, systemId):
+        return OverrideEntityResolver.empty
+
+
 class Scan(object):
     """A single Nmap scan, corresponding to a single invocation of Nmap.
It is
     a container for a list of hosts. It also has utility methods to load
itself
@@ -48,6 +58,7 @@ class Scan(object):
         """Load a scan from the Nmap XML in the file-like object f."""
         parser = xml.sax.make_parser()
         handler = NmapContentHandler(self)
+        parser.setEntityResolver(OverrideEntityResolver())
         parser.setContentHandler(handler)
         parser.parse(f)


Of note: at least one Zenmap user has reported that reducing timing
template from -T5 to -T4 prevented the error from occurring. This may be an
indication that Nmap at -T5 is saturating some folks's network links. In
any case, I don't think we should be making these parsers require Internet
access to work.

Dan
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