full-disclosure - Re: Apache Killer

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Date: Tue, 13 Sep 2011 22:36:16 -0300
From: Javier Bassi <javierbassi@...il.com>
To: full-disclosure@...ts.grok.org.uk
Subject: Re: Apache Killer

On Mon, Sep 12, 2011 at 11:26 PM, xD 0x41 wrote:
> I know this topic is OLD but, i just wonder and, also having spoken to kcope
> re this myself, discussed the size of each bucket wich can be made to
> stupendous amounts and using a different vector, ok, instead of Range:bytes=
> , picture a GET request with as was shown in the code is there, you
> "Request-Range: bytes=5-,5-69,5-" , now we have bypassed most filters
> already in place, and the request range code, is exactly the same as range
> code.
> Only one person spotted this.

HTTPD advisory was very clear that both Range and Request-Range can be
used. Everyone who unset Range probably unset Request-Range too. If
host is vulnerable its a little better to use Range because using
Request-Range will take 8 bytes more. (more bytes = less ranges)

I have tested a bit the exploit and saw 1300 ranges is just a fixed
number chosen by kingcope but it can be a little bigger. Range field
can be almost 8KB long and its a total waste of bytes to use x-y,
format where y is an increasing number that will take more than one
digit. So instead of 1300 you can get it to 2725 max if you use repeat
x-, where x is always single digit number. By doing that the exploit
gets much more effective.

I have attached the source if anyone cares

View attachment "killapache2.pl" of type "text/x-perl" (2090 bytes)

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