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Date: Sat, 02 Mar 2013 21:28:06 -0700
From: Kurt Seifried <kseifried@...hat.com>
To: oss-security@...ts.openwall.com
CC: Marcus Meissner <meissner@...e.de>, Steven Christey <coley@...re.org>
Subject: Re: CVE request: ruby-openid XML denial of service
 attack

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On 03/01/2013 08:50 AM, Marcus Meissner wrote:
> Hi,
> 
> ruby-openid is affected by a XML denial of service (Entity
> Expansion Attack / out of memory) attack as recently described.
> 
> https://github.com/openid/ruby-openid/commit/a3693cef06049563f5b4e4824f4d3211288508ed
>
> 
https://github.com/openid/ruby-openid/pull/43
> https://bugzilla.novell.com/show_bug.cgi?id=804717
> 
> Ciao, Marcus

Hrmm yeah. They disable entity expansion (which seems like a safe bet
for OpenID based XML stuff).

Please use CVE-2013-1812 for this issue, specifically for XIE (XML
Internal Entity expansion).

Just a note on XML External Entity (XXE) expansion in ruby-openid
which uses rexml, according to:

https://pypi.python.org/pypi/defusedxml/0.3

Ruby's REXML document parser is vulnerable to entity expansion attacks
(both quadratic and exponential) but it doesn't do external entity
expansion by default. In order to counteract entity expansion you have
to disable the feature:

REXML::Document.entity_expansion_limit = 0

libxml-ruby and hpricot don't expand entities in their default
configuration. So in general the CVEs I'm assigning to ruby stuff will
be for internal entity expansion and not for external entity expansion
since a protective mechanism exists that the application can use.
Steve does that sound right?

- -- 
Kurt Seifried Red Hat Security Response Team (SRT)
PGP: 0x5E267993 A90B F995 7350 148F 66BF 7554 160D 4553 5E26 7993

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