Date: Fri, 26 Aug 2011 07:55:01 +1000
From: "-= Glowing Sex =-" <doomxd@...il.com>
To: Pat Maechler <Patrick.Maechler@...d.unibas.ch>,
	Michal Zalewski <lcamtuf@...edump.cx>, 
	"HI-TECH ." <isowarez.isowarez.isowarez@...glemail.com>
Cc: full-disclosure@...ts.grok.org.uk
Subject: Re: Apache Killer

Hello list,
Note about the original script/script being used..

Just for anyone out there wishing to make this exploit 'useful' , as it
says, this has nothing todo with the 'testapache' used in that code, as this
involves checking on mod_deflate, wich is useless, so instead of that if ($x
= /Partial/) { }

if($x !~ /^http:\/\//) {
print "[+] Host seems alive..\n";
return 1;
} else {
return 0;
}

would then test all your servers, not just checking on those wich have
mod_deflate enabled... i am yet to test the latest 'killer' :S but i will
have a look soon.
thx to everyone for theyre help on this, every fix was put it seems into the
apache advisory, most of the fixes put forth here anyhow, wich is great.
apache.orgh saw this list, and ackowledged it had todo something good, and
they did, much props to them for theyre response on the matter, they have
been class act on this, even tho it should have been patched in 2007 or even
around then,... that is for atleast one hole... one, i guess could been
stopped if the coe had been looked at, improved, wich has happened now, so
thankyou to all who res[ponded on this.. but please be sure to adjust the
script so it just tests a live url.
cheers!
xd

The advisory i mentioned was also posted already but this, is great work:

         Apache HTTPD Security ADVISORY
         ==============================
                   UPDATE 1

Title:       Range header DoS vulnerability Apache HTTPD 1.3/2.x

CVE:         CVE-2011-3192
Last Change: 20110824 1800Z
Date:        20110824 1600Z
Product:     Apache HTTPD Web Server
Versions:    Apache 1.3 all versions, Apache 2 all versions

Description:
============

A denial of service vulnerability has been found in the way the multiple
overlapping ranges are handled by the Apache HTTPD server:

    http://seclists.org/fulldisclosure/2011/Aug/175

An attack tool is circulating in the wild. Active use of this tools has
been observed.

The attack can be done remotely and with a modest number of requests can
cause very significant memory and CPU usage on the server.

The default Apache HTTPD installation is vulnerable.

There is currently no patch/new version of Apache HTTPD which fixes this
vulnerability. This advisory will be updated when a long term fix
is available.

A full fix is expected in the next 48 hours.

Mitigation:
============

There are several immediate options to mitigate this issue until a full fix
is available:

1) Use SetEnvIf or mod_rewrite to detect a large number of ranges and then
  either ignore the Range: header or reject the request.

  Option 1: (Apache 2.0 and 2.2)

         # Drop the Range header when more than 5 ranges.
         # CVE-2011-3192
         SetEnvIf Range (,.*?){5,} bad-range=1
         RequestHeader unset Range env=bad-range

         # optional logging.
         CustomLog logs/range-CVE-2011-3192.log common env=bad-range

  Option 2: (Also for Apache 1.3)

         # Reject request when more than 5 ranges in the Range: header.
         # CVE-2011-3192
         #
         RewriteEngine on
         RewriteCond %{HTTP:range} !(^bytes=[^,]+(,[^,]+){0,4}$|^
$)
         RewriteRule .* - [F]

  The number 5 is arbitrary. Several 10's should not be an issue and may be
  required for sites which for example serve PDFs to very high end eReaders
  or use things such complex http based video streaming.

2) Limit the size of the request field to a few hundred bytes. Note that
while
  this keeps the offending Range header short - it may break other headers;
  such as sizeable cookies or security fields.

         LimitRequestFieldSize 200

  Note that as the attack evolves in the field you are likely to have
  to further limit this and/or impose other LimitRequestFields limits.

  See: http://httpd.apache.org/docs/2.2/mod/core.html#limitrequestfieldsize

3) Use mod_headers to completely dis-allow the use of Range headers:

         RequestHeader unset Range

  Note that this may break certain clients - such as those used for
  e-Readers and progressive/http-streaming video.

4) Deploy a Range header count module as a temporary stopgap measure:

    http://people.apache.org/~dirkx/mod_rangecnt.c

  Precompiled binaries for some platforms are available at:

       http://people.apache.org/~dirkx/BINARIES.txt

5) Apply any of the current patches under discussion - such as:


http://mail-archives.apache.org/mod_mbox/httpd-dev/201108.mbox/%3cCAAPSnn2PO-d-C4nQt_TES2RRWiZr7urefhTKPWBC1b+K1Dqc7g@mail.gmail.com%3e

OS and Vendor specific information
==================================

Red Hat:        Option 1 cannot be used on Red Hat Enterprise Linux 4.
               https://bugzilla.redhat.com/show_bug.cgi?id=732928

NetWare:        Pre compiled binaries available.

Actions:
========

Apache HTTPD users who are concerned about a DoS attack against their server
should consider implementing any of the above mitigations immediately.

When using a third party attack tool to verify vulnerability - know that
most
of the versions in the wild currently check for the presence of mod_deflate;
and will (mis)report that your server is not vulnerable if this module is
not
present. This vulnerability is not dependent on presence or absence of
that module.

Planning:
=========

This advisory will be updated when new information, a patch or a new release
is available. A patch or new apache release for Apache 2.0 and 2.2 is
expected
in the next 48 hours. Note that, while popular, Apache 1.3 is deprecated.

...it took into account the public,and altho the fixes could have been
credited, it is a great advisory, and very good on respnding to the issue,
albeit late.
xd



On 25 August 2011 03:07, Pat Maechler <Patrick.Maechler@...d.unibas.ch>wrote:

> Does this fix work as well if I put it in httpd.conf instead?
> I'm no Apache/RewriteEngine crack, but I know that there are some
> differences with the rewrite engine if you put it into httpd.conf
> instead of .htaccess (and I have currently no possibility to do a safe
> test) :-/
>
> Reply to
> > From: Davide Guerri <davide.guerri () gmail com>
> > Date: Wed, 24 Aug 2011 10:03:03 +0200
> >> RewriteEngine On
> >> RewriteCond %{REQUEST_METHOD} ^(HEAD|GET) [NC]
> >> RewriteCond %{HTTP:Range} ([0-9]*-[0-9]*)(\s*,\s*[0-9]*-[0-9]*)+
> >> RewriteRule .* - [F]
>
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