[Snort-sigs] Snort "NORMALIZATION" question

Joel Esler jesler at ...435...
Mon Feb 6 13:57:58 EST 2012


http_header, http_client_body, http_cookie don't do normalization.

http_uri does, and it's configuration is based upon how you configure
http_inspect just like it always has.

On Mon, Feb 6, 2012 at 1:54 PM, Miso Patel <miso.patel at ...2420...> wrote:

> I see talk and read in the manual about "NORMALIZATION" that is done
> by pre processors.  So fields like http match (http_header, http_uri,
> http_cookie, http_client_body, etc.) are "NORMALIZED" (depending on
> what you set in your snort .conf and compile-configure times).
>
> My question is, what exactly does the "NORMALIZATION" does?  I can get
> one of my engineers to look and the code and tell me but I thought
> that perhaps there would be a good explanation of this (like one of a
> "how-to" guides) although I can-not find it when searching.
>
> For an example, what if there is http_client_body that sees a POST
> '?petsolv=true&saltedPug=7&seed=many&jeryk=12Pepper', do the '=' and
> '&' characters get "NORMALIZED" out or changed in any way?  This is
> the specifics examples of what we are asking about.  What gets changed
> and how so it?  I think many would like to read about it and can then
> know for sure without doing many lab tests or getting a programmer to
> read the Snort programming.
>
> Also (my engineers want me to ask), is when you use the specific
> 'http' fields (http_header, etc.), what is searched?  Does the header
> "name" be included in the field?  What about before and after
> new-lines?  Are more than one space removed?  Do you do double decode?
> (I'm not sure what this is but Vijay wanted me to ask :)
>
> Thank you to all.
>
> Miso, CISO
>
>
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-- 
Joel Esler | http://blog.snort.org | http://vrt-blog.snort.org |
http://blog.clamav.net
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