[Snort-devel] Serious problems Snort 2.9 with relative content matches using http_inspect preprocessor and http_uri keyword

L0rd Ch0de1m0rt l0rdch0de1m0rt at ...2499...
Wed Nov 20 13:50:39 EST 2013


Hello,

Thanks rmkml and all whom responded.

As stated, the latests version I tested on was SNORT 2.9.5.3.  This is a
fairly recent version IIRC (I do have many devices that are and have to run
older versions -- some 2.8.x and upgrading is not an option at this point)
...... can someone from Sourcefire tell me if version v2.9.5.3 is still
supported?  Can Joel or Cisco company say to me that they are seeing this
issue and if/when i was fixed? Can you known which versions are affected? I
was hoping this problem would go away but upper mgmt is breathing on my
neck about this.

Thanks!

Cheers,

Lord C.


On Thu, Nov 7, 2013 at 4:42 PM, L0rd Ch0de1m0rt <l0rdch0de1m0rt at ...2499...>wrote:

> Hello.
>
> @Bad Horse: I tried http_raw_uri and it still does not work.  That is good
> point about the colon in the uri.  The funny thing is that if I increase
> the distance, it WILL work so it seems that maybe the parser it getting
> "stuck" on the first content match (0x2F) and not evaluating everything in
> full.  To test, I tried this rule and it DID work! :
>
> 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:50;
> )
>
> @Baggy: I tried a number of versions and the latest was 2.9.5.3 I believe,
> is that still supported?
>
> Thanks for everyones' help.
>
> Cheers,
>
> Lord C.
>
>
> On Thu, Nov 7, 2013 at 12:31 PM, Bhagya Bantwal <bbantwal at ...402...>wrote:
>
>> 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 at ...2499...
>> > 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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>>
>>
>
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