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Network Security Snort-Signatures
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Re: [Snort-sigs] Apache Proxy

Subject: Re: [Snort-sigs] Apache Proxy
Date: Fri, 14 Jan 2005 16:14:21 +0100 (CET)

Hiho,


Actually, these rules are never going to fire -- at least not under normal circumstances where clients are following RFC 2616 (http://www.faqs.org/rfcs/rfc2616.html). GET requests look like this when they come across the wire:

GET /path/to/file.html HTTP/1.1

Clients never need to transmit the http://<host> portion of a URL: http:// is obvious because the packet is being received by an HTTP server, and <host> is either implied from wherever the packet is being sent, or stated explicitly with a directive of

Host: www.example.com

somewhere following the GET request (most likely immediately after it).

That true for all normal requests. Yet I believe that Adam wants to trigger for the following attempts:

  GET http://www.ebay.com/ HTTP/1.1" 200 2986

  I see hat every now an then in the logfiles of the servers I manage.
  Don't be confused by the "200" - its the homepage that is delivered.

Even if they did fire, though, I'm a bit confused as to how these rules differentiate between a misconfigured proxy server and a standard web server.

In the example above you get www.ebay.com instead of the original requested webserver if that webserver is indeed misconfigured. A nice way to cirumvent URL Scanners.

In theory, these would fire on every single request that comes into one of your web servers -- and if you run even a moderately busy server, you're

Not even in theory. You wrote yourself that a legitimate request is GET /path/to/file.html There is only a small number of "GET http://blabla..."; requests. None of them was ever legitimate. Maybe other people have different experiences?

  Cheers,


Chris Kronberg.


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