Re: Inaccessible Port 80 - Pentest
- From: "Steve Armstrong" <stevearmstrong@xxxxxxxxxxxxxxxxxxx>
- Date: Sun, 10 Aug 2008 00:09:18 +0100
Arvind,
Several people have mentioned firewalls, but stick to layer thee. I believe the barrier you are facing is a layer 7 one.
A mixture of layer 3 port filtering to restrict you to port 80 would seem to be inplace.
This could be open to everyone to allow troubleshooting activities. However, I believe you are also looking at a layer 7 proxy that is restricting access to the service behind it based upon source ip.
The multiple ip addresses could be on the same box thus the strange presentation you see.
There are several reasons for wanting this type of restriction. It to a certain degree priviatizes the website, is transparent to the end user, requires no installation on the client, allows traffic behind the FW to be monitored without the need for decryption. And let's not forget permissions can be changed by the admin with no cost or implementation lag.
It appears to be hidden in plain sight. Like a VPN without the V and some of the P.
As an after thought, were you getting or putting Http data? Perhaps it was a 'collection' server that only allowed clients to post or put Http. That way the clients or agents use common protocols and the layer7 FW restricts their http command
HTH
Steve A
---------------------/
Logically Secure
On 8 Aug 2008, at 16:59, "arvind doraiswamy" <arvind.doraiswamy@xxxxxxxxx > wrote:
Hey Guys,
Very recently we did a PenTest for a client where we came across a
strange(atleast to me) situation. Had an IP block which on scanning
revealed only port 80 open which sounded ok. Any kind of requests
though from the external world - I tried from multiple IP's and even
through TOR were blocked by a firewall which kept displaying its
custom "Access denied" page. So obviously there was some kind of IP
based restriction in place which said -- Only these IP's can connect
to whatever is running on port 80. No problems till here.
My question is: Why would anyone want to have a live server on the
Internet, open one port on it and then block it from public use?
Obvious answers that sprung to mind were:
a) Maybe its an internal server running a web app to be accessed only internally
----- So why is it public , in the DMZ then? Shouldnt it be
on the internal network?
b) Maybe some hosts/apps on the internal network needed to connect to
port 80 of a DMZ server before going out?
------ Then again why is it public. These servers could be
placed on an internal segment and the traffic could be NATTEd before
it goes out like all other Internet destined traffic. And Secondly I
am not able to think of a situation like this --- What traffic apart
from a proxy could behave this way --- where I have -- Internal IP
-------> DMZIP:80 ---------> Internet ? And mind you this wasnt just 1
IP - there were many, so I'm quite sure I've missed something.
What are your thoughts?
Thnx
Arvind
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