Re: [Request for Testers] CVE-2011-3368 "Reverse Proxy Bypass"

[Gutek <ange.gutek () gmail com>]

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Le 12/10/2011 09:34, Michael Meyer a écrit :
> *** Gutek <ange.gutek () gmail com> wrote:
>  
> > Yes, that's the key point : getting an error status code, whatever it
> > could be. Maybe a 30s timeout is, here, too short ? On the other hand, a
> > timeout of >1m could make this script very slow. I have to figure out
> > the best balance between speed and efficiency.
>
> I'm doing something like the following for OpenVAS at the moment:
>
> ,---|
> | mime@kira[4]: ~ 0)$ telnet 192.168.2.7 80
> | Trying 192.168.2.7...
> | Connected to 192.168.2.7.
> | Escape character is '^]'.
> | GET @6666.6666.6666.6666 HTTP/1.0
> |
> | HTTP/1.1 200 OK
> | Date: Wed, 12 Oct 2011 06:46:28 GMT
> | Server: Apache/2.2.10 (Linux/SUSE)
> | Vary: accept-language,accept-charset
> | Accept-Ranges: bytes
> | Content-Type: text/html; charset=iso-8859-1
> | Content-Language: en
> | Connection: close
> |
> | [...]
> |
> |<title>Bad Gateway!</title>
> `---|
>
> With such a wrong "ip", a vulnerable server immediately returns a 200 and
> "Bad Gateway". Could you confirm that? 
>
> Micha
I'd rather say no. On the first hand, Contextis' analysis concludes that
(in the case of the LAN ip test, that's different for the other ones) a
vulnerable reverse proxy should return an *error* within a *delay*
(...when querying a non-existing host).
According to this statement, *immediately* should be the evidence for a
*non* -vulnerable target, and a 200 as well, whatever the title would be.
In this particular case, a 200 which is in fact a customized error
answer (the normal behavior would be a code 502 in this case), I'd
conclude maybe "filtered" or "patched". Plus, we have no delay, which
sounds to me like a filtering system is immediately spotting something
wrong.

On the other hand, my own tests seem to show that everytime I get a 200,
that was in fact a false-positive. It seems to confirm the Contextis
conclusion on that matter.

The only case when you could get an immediate 200 is the one when you've
hit an existing LAN webservice. Lucky you :)

Cheers !

A.G.
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