Re: Protecting publicly reacheable servers (e.g. HTTP)?

[ark () eltex ru]

nuqneH,

I am still trying to figure out how to prevent data-driven attacks
on proxy level.

I have a quite good set of application proxies that do stop protocol-driven
attacks like lpd or pop3 exploits so it adds some extra protection to
those servers but that does not work for http, where all attacks (or nearly so)
do fit the protocol. Some extra heuristics are required - do you people have
any ideas and suggestions?

YOU (Patrick M. Hausen) WROTE:
>  
>  Dear fellow wizards,
>  
>  Yesterday we got into a small internal arguement about
>  wether protecting publicly reachable servers with
>  currently available firewall products makes any sense
>  or not.
>  
>  A large corporation asked for an offer for "housing" of
>  a web and database server including hardware and software
>  for the server itself and "firewall protection".
>  The server is supposed to offer content to the public via
>  HTTP.
>  
>  My reasoning has always been that - given the state of
>  firewall products today - a static packet filter that
>  blocks all but port 80 would be the most appropriate
>  solution to offer some sort of protection to the server
>  machine.
>  
>  Since all products I know of - even our beloved Gauntlet
>  application level proxy - don't filter HTTP requests
>  wrt extremly long URLs or other "malformed" stuff, that
>  intends to cause a buffer overflow in the web application,
>  I don't see any improvement by using a "firewall product"
>  in place of the packet filter. Well, DoS attacks targeting the
>  IP stack may be guarded against, but then one would try to
>  DoS the firewall with the same result - application out
>  of service.
>  
>  I hope most of you tend to agree with the above ;-)
>  
>  Anyway, all competitors offered the customer elaborate and
>  expensive setups consisting of at least two redundant firewall
>  boxes, two switches, and those nice looking drawings with
>  a lot of crossing lines that give managers the warm fuzzy
>  impression of "redundancy" and "fail safety".
>  Probably most of them are offering Nokia or PIX, but we weren't
>  given that much detail. ;-)
>  
>  
>  So  basically, I have two questions to you all:
>  
>  1. Do you aggree with me wrt to the firewall vs. packet filter topic?
>     What's the intention of all these companies offering more complicated
>     setups? Besides making money at the job, of course. I don't imply
>     they are consciously trying to sell a big unnecessary something.
>     They rather do think they sell something "good", IMHO.
>     So, what's the point?
>  
>  2. In the last couple of years a new type of device coined "layer 4 switch"
>     appeared and these things seem to have reached a certain level of
>     maturity and market penetration. I'm talking about load balancing
>     devices like e.g. Big IP.
>  
>     Since these things actually look inside the HTTP requests to provide
>     (at least they claim to provide) session and cookie persistence and
>     similar stuff when distributing the requests to a farm of servers
>     - what do you think these boxes add to the security of the web
>     servers they "load balance"? Some claim to protect against certain
>     types of DoS attacks, too.
>  
>  
>  Thanks for your comments,
>  
>  Patrick M. Hausen
>  Technical Director
>  -- 
>  punkt.de GmbH         Internet - Dienstleistungen - Beratung
>  Scheffelstr. 17 a     Tel. 0721 9109 -0 Fax: -100
>  76135 Karlsruhe       http://punkt.de
>  _______________________________________________
>  firewall-wizards mailing list
>  firewall-wizards () nfr com
>  http://list.nfr.com/mailman/listinfo/firewall-wizards
>  


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