Re: Serious problems Snort 2.9 with relative content matches using http_inspect preprocessor and http_uri keyword

[Bhagya Bantwal <bbantwal () sourcefire com>]

Hello,

Have you tested with snort version snort 2.9.5.5? With this snort version I
see the alert as expected.

If it still doesn't work, you can send me your pcap & conf and I will take
a look.

Thanks!
B


On Wed, Nov 6, 2013 at 2:01 PM, L0rd Ch0de1m0rt <l0rdch0de1m0rt () gmail com>wrote:

> Hello,
>
> Previously I posted on this list with an email subject of, "distance,
> within, and negated matches".  Today I bring another issue that I am having
> that I believes could be related and is non-trivial and super serious.
>
> When I analyze it I believe that relative (1 byte?) content matches are
> not being properly applied in the http_uri buffer.  Other buffers for the
> http preprocessor may be affected as well but I have not tested them but I
> won't be suprised if they are also infected by this bug.
>
> This is an example of the rule Im using:
>
> alert tcp $HOME_NET any -> $EXTERNAL_NET $HTTP_PORTS (msg:"Dont Cry 4 Me
> Trojanina"; flow:established, to_server; content:"GET"; http_method;
> content:"|2F|"; http_uri; content:"|3A|"; http_uri; distance:1; within:20;)
>
> Using a simple pcap ("Follow TCP stream" output from Ethereal is here:)
>
> GET /iused/2/trust/the.http_preprocessor/sad1/cr1090hs:SN-IF-FF- HTTP/1.1
>
> The rule does not alert even though the Snort output shows that the HTTP
> data is being properly recognized and processed by the http_inspect
> preprocessor. The Snort output shows that the specific GET request is being
> recognized as a HTTP "GET" request.
>
> When I remove the http_inspect directives, the rule starts to work, this
> is an example:
>
> alert tcp $HOME_NET any -> $EXTERNAL_NET $HTTP_PORTS (msg:"Dont Cry 4 Me
> Trojanina"; flow:established, to_server; content:"GET"; http_method;
> content:"|2F|"; content:"|3A|"; distance:1; within:20;)
>
> Is this (still?) a known issue?  I have tested this on multiple different
> versions of Snort 2.9.
>
> Cheers,
>
> Lord C.
>
>
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