WebApp Sec mailing list archives
Re: Apache Killer - take 2?
From: Anestis Bechtsoudis <bechtsoudis.a () gmail com>
Date: Mon, 23 Jan 2012 15:40:13 +0200
On 01/19/2012 09:59 PM, Damiano Bolzoni wrote:
Hi all, today we saw a weird HTTP header in a request that came to a web server we are monitoring: HEAD /contact HTTP/1.1 Content-Range: bytes 1-1024/-1 User-Agent: Opera/9.80 (Windows NT 5.1; U; pl) Presto/2.5.22 Version/10.51 Host: www.xyz.nl Accept: */* The offending IP is not in any blacklist, and the intent is kind of clear...the server is Apache, but I have no detailed information about the version/patching level. The server went ahead with a simple redirect to the default error page. Is this just a clumsy way to attempt an overflow of one of the range boundaries and replicate the infamous Apache Killer attack? cheers
Apache byte-range killer use many small byte-range chunks in a single request. So no, your attached request is not related to such an attack. At latest Apache stable release (2.2.21) -1 is not a valid entity-length, resulting in a full size 200 response (and not a 206 partial content response) despite the requested range. For better understanding take a look at modules/http/byterange_filter.c at apache sources. I attach a simple perl PoC to check your web servers in case you have to deal with outdated versions. Regards, Anestis -- Anestis Bechtsoudis Network Operation Center, Laboratory for Computing (LabCom), Dept. of Computer Engineering & Informatics, University of Patras, Greece
Attachment:
byte_range_check.pl
Description:
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Current thread:
- Apache Killer - take 2? Damiano Bolzoni (Jan 22)
- Re: Apache Killer - take 2? Anestis Bechtsoudis (Jan 23)
- Re: Apache Killer - take 2? Damiano Bolzoni (Jan 23)
- Re: Apache Killer - take 2? Anestis Bechtsoudis (Jan 23)