Follow @Openwall on Twitter for new release announcements and other news
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date: Tue, 3 Jun 2014 08:37:26 -0700
From: Tim <tim-security@...tinelchicken.org>
To: David Jorm <djorm@...hat.com>
Cc: oss-security@...ts.openwall.com
Subject: Re: CVE-2014-0191 libxml2: external parameter entity
 loaded when entity substitution is disabled


Hi David,

> Sorry for the absurdly late reply to this thread. I finally found time to do
> some testing on OpenJDK 1.7.0_45. I can confirm Tomas' assessment that
> setExpandEntityReferences() and
> setFeature(XMLConstants.FEATURE_SECURE_PROCESSING, true) have no bearing on
> whether or not entity references are expanded, nor do they purport
> to.

Yeah, you gotta love FEATURE_SECURE_PROCESSING.  It's just like
calling a website "secure" because it uses SSL.

I agree that these features don't purport to turn off certain
dangerous features, but to a developer who doesn't know what parameter
entities are, they could very easily assume they are safe with
setExpandEntityReferences(false).


> Applications that process attacker-supplied XML using Xerces are vulnerable
> to SSRF attacks unless they use both
> setFeature("http://xml.org/sax/features/external-parameter-entities", false)
> and setFeature("http://xml.org/sax/features/external-general-entities",
> false).
> 
> The OWASP XXE document should be updated to mention
> external-parameter-entities. I will do this as soon as my OWASP wiki account
> is approved.

Feel free to use this as a reference for other thoughts on what
developers should be wary of:
  http://vsecurity.com/download/papers/XMLDTDEntityAttacks.pdf

I would also be interested to hear if you think anything I mention in
there is inaccurate.

Cheers,
tim

Powered by blists - more mailing lists

Please check out the Open Source Software Security Wiki, which is counterpart to this mailing list.

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.