Re: [ANN] Struts 2 up to 2.3.16.1: Zero-Day Exploit Mitigation (security | critical)

[Tim <tim-security () sentinelchicken org>]

Also, I'm a tad confused by the regex you have as a stop-gap.  For the
readers' convenience:

(.*\.|^|.*|\[('|"))(c|C)lass(\.|('|")]|\[).*,^dojo\..*,^struts\..*,^session\..*,^request\..*,^application\..*,^servlet(Request|Response)\..*,^parameters\..*,^action:.*,^method:.*


If your regex evaluation is case-sensitive, then clearly you need to
check for "class" and "Class", since OGNL converts "foo" to "getFoo",
and would likely also convert "Foo" to "getFoo".  But if the blacklist
is case sensitive, then don't you also need to check for
"^Request...", "^Session...", "^Struts...", and so on?  Or is it
actually case insensitive and you're just being unnecessarily careful
with "class"?

Also: Thought about unicode lately?

tim


PS- yes, I'm too lazy to actually look at the Struts code right now.



On Fri, Apr 25, 2014 at 09:52:23AM -0700, Tim wrote:
> So I have to say, I feel like the Struts team is kind of... failing.
> Here are my gripes:
>
> A) I questioned the last bug fix in the thread here [1], where we
>    were all reassured that it was just "ClassLoader manipulation", not 
>    RCE.  Clearly that's not true.
>
> B) The fix for the last CVE was that crappy "^class\." filter, which
>    I pointed out was insufficient.  The Struts team quickly fixed
>    that, but never bothered to update the "workaround" section in the 
>    last advisory to the less-terrible ".*\.class\..*" regex (or whatever
>    it was).  So if developers just implemented the work around from
>    the advisory, they were obviously not protected.  (In hindsight,
>    they never were protected even with the better regex, but was just
>    irresponsible not to make the second regex more public.)
>
> C) The Struts team is playing whack-a-mole.  Instead of fixing the
>    root issue, they are just adding one blacklist regex after another,
>    hoping no one figures out yet another way around it.
>
>
> I urge you to take OGNL and *throw it out*.  Replace it with something
> that allows only a white list of properties to be set, based on what
> the application defines as relevant.  Until then, I'm recommending to
> my clients that they avoid Struts like the plague.
>
> tim
>
> 1. http://seclists.org/fulldisclosure/2014/Mar/53
>
>
>
> On Thu, Apr 24, 2014 at 05:37:13PM +0200, Rene Gielen wrote:
> > In Struts 2.3.16.1, an issue with ClassLoader manipulation via request
> > parameters was supposed to be resolved. Unfortunately, the correction
> > wasn't sufficient.
> >
> > A security fix release fully addressing this issue is in preparation and
> > will be released as soon as possible.
> >
> > Once the release is available, all Struts 2 users are strongly
> > recommended to update their installations.
> >
> > * Until the release is available, all Struts 2 users are strongly
> > recommended to apply the mitigation described in [1] *
> >
> > Please follow the Apache Struts announcement channels [2][3][4][5] to
> > stay updated regarding the upcoming security release. Most likely the
> > release will be available within the next 72 hours. Please prepare for
> > upgrading all Struts 2 based production systems to the new release
> > version once available.
> >
> > - The Apache Struts Team.
> >
> > [1] http://struts.apache.org/announce.html#a20140424
> > [2] http://struts.apache.org/mail.html
> > [3] http://struts.apache.org/announce.html
> > [4] https://plus.google.com/+ApacheStruts/posts
> > [5] https://twitter.com/TheApacheStruts
> >
> > -- 
> > René Gielen
> > http://twitter.com/rgielen
> >
> > _______________________________________________
> > Sent through the Full Disclosure mailing list
> > http://nmap.org/mailman/listinfo/fulldisclosure
> > Web Archives & RSS: http://seclists.org/fulldisclosure/
>
> _______________________________________________
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