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Re: [NSE] Improved performance of http-default-accounts
From: George Chatzisofroniou <sophron () latthi com>
Date: Sun, 18 Aug 2013 04:41:29 +0300

On Wed, Aug 14, 2013 at 01:28:25AM +0000, nnposter () users sourceforge net wrote:
For any given fingerprint from http-default-accounts-fingerprints
script http-default-accounts currently tests corresponding default
credentials if at least one  of the probe URLs succeeded, namely
returned with status other than 404.

Some web servers, such as Linksys devices, respond with HTTP/401 even
for non-existent URLs. This causes the script to assume that these URLs
do exist and to test the credentials, while ideally they should be
tested only on those servers where they make sense.

The purpose of the attached patches is to reduce unnecessary credential
guessing by implementing a new optional fingerprint element, function
target_check(), which takes some already collected target information,
including a probe URL response, and returns true or false, indicating
whether the credential guessing should be attempted or not.

All of the current fingerprints have been retrofitted with simple
target validations as follows:

* If the fingerprint uses native HTTP authentication, validate that the
target's realm matches the server type.

* If the fingerprint uses form-based authentication, validate that the
probe URL returned with HTTP/200 (as opposed to perhaps HTTP/401).

When testing against the above-mentioned Linksys the difference was
notable: 14 login attempts before the patch versus 1 attempt after the

Thanks. I commited these patches as revision r31899.

This functionality provides opportunity for further improvement by
being able to match page content to differentiate between real HTTP/200
and a custom error page. (As of now the script completely skips targets
that return HTTP/200 for non-existent pages.)

I added a TODO note for this in http-default-accounts-fingerprints.

George Chatzisofroniou
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