[Snort-devel] Fwd: Snort blocking connection but not logging the drop

Cody Brugh cbrugh at ...2499...
Mon May 12 18:30:16 EDT 2014


Ok, I disabled everything (rules, normalizations, pre-processors, dynamic
rules) and still not able to connect  with snort in-line.

Attached is my snort.conf to make sure I got everything... At this point do
you believe this is a bug?  Would the alpha snort version maybe work?


On Mon, May 12, 2014 at 6:19 PM, Russ Combs (rucombs) <rucombs at ...3461...>wrote:

>
>  ------------------------------
> *From:* Cody Brugh [cbrugh at ...2499...]
>
> *Sent:* Monday, May 12, 2014 6:11 PM
> *To:* Russ Combs (rucombs)
> *Cc:* Joel Esler (jesler); snort-devel at lists.sourceforge.net
> *Subject:* Re: [Snort-devel] Fwd: Snort blocking connection but not
> logging the drop
>
>   Would a pre-processor engine be blocking but not logging?  When you say
> disable things are you talking about removing pre-processing engines or
> other?
>
> * The are two ways packets get blocked: rules and normalization.  If those
> aren't indicated, it could be a bug or it could be something else entirely,
> like your Snort environment.  To isolate, first disable all your rules.
> Then disable all normalizations.  Then start disabling preprocessors.
>
>
> On Mon, May 12, 2014 at 6:06 PM, Russ Combs (rucombs) <rucombs at ...3461...>wrote:
>
>>
>>  ------------------------------
>> *From:* Cody Brugh [cbrugh at ...2499...]
>> *Sent:* Monday, May 12, 2014 4:32 PM
>>
>> *To:* Russ Combs (rucombs)
>> *Cc:* Joel Esler (jesler); snort-devel at lists.sourceforge.net
>> *Subject:* Re: [Snort-devel] Fwd: Snort blocking connection but not
>> logging the drop
>>
>>    Running in passive mode I see no alerts/blocks for this specefic API
>> command... Also note that the API command is running without a problem now
>> that snort is in passive mode.
>>
>>  Something inside of snort is catching it but I cannot figure out what...
>> would this be like a preprocessor or dynamic rules or something?
>>
>>  * If there is something in Snort blocking your session, then the output
>> should indicate that.  At this point I would try disabling things
>> systematically to isolate it.
>>
>>
>> On Mon, May 12, 2014 at 4:18 PM, Russ Combs (rucombs) <rucombs at ...3461...>wrote:
>>
>>>
>>>  ------------------------------
>>> *From:* Cody Brugh [cbrugh at ...2499...]
>>> *Sent:* Monday, May 12, 2014 4:11 PM
>>>
>>> *To:* Russ Combs (rucombs)
>>> *Cc:* Joel Esler (jesler); snort-devel at lists.sourceforge.net
>>> *Subject:* Re: [Snort-devel] Fwd: Snort blocking connection but not
>>> logging the drop
>>>
>>>   I now see my other alerts/drops coming in on the console, however
>>> when I run the API command I get nothing from a alert/drop status...  What
>>> else could be blocking it?
>>>
>>>  * The log you sent shows no blocks, so either it isn't configured the
>>> same or it isn't getting the same traffic as before.  Or maybe you have
>>> more than one Snort running?  In any case, the output you sent indicates
>>> Snort is not the problem.
>>>
>>> What happens if you run in passive mode by just removing the -Q?  Do you
>>> get alerts?  Blocks?
>>>
>>>
>>> On Mon, May 12, 2014 at 4:09 PM, Cody Brugh <cbrugh at ...2499...> wrote:
>>>
>>>> Attached.
>>>>
>>>>
>>>> On Mon, May 12, 2014 at 4:05 PM, Russ Combs (rucombs) <
>>>> rucombs at ...3461...> wrote:
>>>>
>>>>>
>>>>>  ------------------------------
>>>>> *From:* Cody Brugh [cbrugh at ...2499...]
>>>>> *Sent:* Monday, May 12, 2014 3:59 PM
>>>>>
>>>>> *To:* Russ Combs (rucombs)
>>>>> *Cc:* Joel Esler (jesler); snort-devel at lists.sourceforge.net
>>>>> *Subject:* Re: [Snort-devel] Fwd: Snort blocking connection but not
>>>>> logging the drop
>>>>>
>>>>>    Alright, I done that and run my command but see nothing... looking
>>>>> at the console and /var/log/messages...
>>>>>
>>>>> /usr/local/bin/snort -M -A console -q --daq afpacket -i eth2:eth3 -Q
>>>>> --daq-var buffer_size_mb=2048MB -c /etc/snort/snort.conf
>>>>>
>>>>>  * Ok, do this and send the whole output file (snort.log) after
>>>>> stopping with ctl-c:
>>>>>
>>>>> /usr/local/bin/snort -A cmg --daq afpacket -i eth2:eth3 -Q --daq-var
>>>>> buffer_size_mb=2048MB -c /etc/snort/snort.conf &> snort.log
>>>>>
>>>>>  This is very odd
>>>>>
>>>>>
>>>>> On Mon, May 12, 2014 at 3:24 PM, Russ Combs (rucombs) <
>>>>> rucombs at ...3461...> wrote:
>>>>>
>>>>>>
>>>>>>  ------------------------------
>>>>>> *From:* Cody Brugh [cbrugh at ...2499...]
>>>>>> *Sent:* Monday, May 12, 2014 3:01 PM
>>>>>>
>>>>>> *To:* Russ Combs (rucombs)
>>>>>> *Cc:* Joel Esler (jesler); snort-devel at lists.sourceforge.net
>>>>>> *Subject:* Re: [Snort-devel] Fwd: Snort blocking connection but not
>>>>>> logging the drop
>>>>>>
>>>>>>   That's the thing, I don't know what rule is being hit as it
>>>>>> doesn't show in sborby. Is there a way to show the rule that was triggered?
>>>>>>  Maybe that is done with the perf monitoring stuff?
>>>>>>
>>>>>>  * I can't help you with Snorby.  Since this is easy for you to
>>>>>> reproduce, I suggest running Snort from the command line directly, no
>>>>>> scripts, and no -M option.  Add -A cmg -q to your command line.  You will
>>>>>> see the alert.
>>>>>>
>>>>>>
>>>>>>
>>>>>> On May 12, 2014, at 2:59 PM, "Russ Combs (rucombs)" <
>>>>>> rucombs at ...3461...> wrote:
>>>>>>
>>>>>>
>>>>>>  ------------------------------
>>>>>> *From:* Cody Brugh [cbrugh at ...2499...]
>>>>>> *Sent:* Monday, May 12, 2014 2:53 PM
>>>>>> *To:* Russ Combs (rucombs)
>>>>>> *Cc:* Joel Esler (jesler); snort-devel at lists.sourceforge.net
>>>>>> *Subject:* Re: [Snort-devel] Fwd: Snort blocking connection but not
>>>>>> logging the drop
>>>>>>
>>>>>>   I just disabled the tcp normalize and cleaned up some
>>>>>> pre-processeors that I don't need, however I am still being dropped when
>>>>>> trying to connect to the API with snort ON.  Attached are the stats from a
>>>>>> quick run where I tried to connect 4-5 times.  Let me know if you see
>>>>>> something or other suggestions.
>>>>>>
>>>>>> * You have 1 alert, 2 blocks, 1 blacklisted, and 2 injects.  I would
>>>>>> start by changing the rule that is firing from drop to alert.
>>>>>>
>>>>>> Thanks,
>>>>>> Cody
>>>>>>
>>>>>>
>>>>>> On Mon, May 12, 2014 at 1:05 PM, Russ Combs (rucombs) <
>>>>>> rucombs at ...3461...> wrote:
>>>>>>
>>>>>>>
>>>>>>>  ------------------------------
>>>>>>> *From:* Cody Brugh [cbrugh at ...2499...]
>>>>>>> *Sent:* Monday, May 12, 2014 12:53 PM
>>>>>>>
>>>>>>> *To:* Russ Combs (rucombs)
>>>>>>> *Cc:* Joel Esler (jesler); snort-devel at lists.sourceforge.net
>>>>>>> *Subject:* Re: [Snort-devel] Fwd: Snort blocking connection but not
>>>>>>> logging the drop
>>>>>>>
>>>>>>>   What all is the normalizer used for?  Will turning it off make me
>>>>>>> vulnerable?
>>>>>>>
>>>>>>>  * The normalizer does various scrubbing and blocking to improve
>>>>>>> detection.  You need to assess your security position with or without it.
>>>>>>> For details on the normalizer, check here:
>>>>>>> http://manual.snort.org/node168.html.
>>>>>>>
>>>>>>>  Just trying to understand what that mechanism does.
>>>>>>>
>>>>>>>  Thanks,
>>>>>>> Cody
>>>>>>>
>>>>>>> On May 12, 2014, at 12:02 PM, "Russ Combs (rucombs)" <
>>>>>>> rucombs at ...3461...> wrote:
>>>>>>>
>>>>>>>   The normalizer is blocking packets:
>>>>>>>
>>>>>>>              tcp::block: 272
>>>>>>>
>>>>>>> You can prevent that by commenting out the normalize_tcp line from
>>>>>>> your conf.
>>>>>>>
>>>>>>> You can debug it a little further by enabling all preprocessor rules
>>>>>>> by adding / uncommenting them in your conf or by adding this to your conf:
>>>>>>>
>>>>>>>     config autogenerate_preprocessor_decoder_rules
>>>>>>>
>>>>>>> Then you should see why the normalizer is blocking.  When I do that
>>>>>>> with the pcap you sent I see a bad TCP reset.
>>>>>>>
>>>>>>>  ------------------------------
>>>>>>> *From:* Cody Brugh [cbrugh at ...2499...]
>>>>>>> *Sent:* Monday, May 12, 2014 11:52 AM
>>>>>>> *To:* Russ Combs (rucombs)
>>>>>>> *Cc:* Joel Esler (jesler); snort-devel at lists.sourceforge.net
>>>>>>> *Subject:* Re: [Snort-devel] Fwd: Snort blocking connection but not
>>>>>>> logging the drop
>>>>>>>
>>>>>>>   Attached is the shutdown stats.  Let me know what you
>>>>>>> find/suggest.
>>>>>>>
>>>>>>> Thanks,
>>>>>>> Cody
>>>>>>>
>>>>>>>
>>>>>>> On Mon, May 12, 2014 at 11:41 AM, Russ Combs (rucombs) <
>>>>>>> rucombs at ...3461...> wrote:
>>>>>>>
>>>>>>>>
>>>>>>>>  ------------------------------
>>>>>>>> *From:* Cody Brugh [cbrugh at ...2499...]
>>>>>>>> *Sent:* Monday, May 12, 2014 11:18 AM
>>>>>>>>
>>>>>>>> *To:* Russ Combs (rucombs)
>>>>>>>> *Cc:* Joel Esler (jesler); snort-devel at lists.sourceforge.net
>>>>>>>> *Subject:* Re: [Snort-devel] Fwd: Snort blocking connection but
>>>>>>>> not logging the drop
>>>>>>>>
>>>>>>>>    How do I gather those stats?  Are you looking for this?
>>>>>>>> http://manual.snort.org/node20.html
>>>>>>>>
>>>>>>>>  * Not those.  Do a clean start, run your traffic, and then stop
>>>>>>>> Snort or give it a usr1 signal and check the output.  Check console or
>>>>>>>> syslog depending on how you run.
>>>>>>>>
>>>>>>>>  Thanks,
>>>>>>>> Cody
>>>>>>>>
>>>>>>>>
>>>>>>>> On Mon, May 12, 2014 at 11:05 AM, Russ Combs (rucombs) <
>>>>>>>> rucombs at ...3461...> wrote:
>>>>>>>>
>>>>>>>>>  What are your shutdown / usr1 stats?  Do they show normalizer
>>>>>>>>> blocks?
>>>>>>>>>
>>>>>>>>>  ------------------------------
>>>>>>>>> *From:* Cody Brugh [cbrugh at ...2499...]
>>>>>>>>> *Sent:* Monday, May 12, 2014 10:29 AM
>>>>>>>>> *To:* Russ Combs (rucombs)
>>>>>>>>> *Cc:* Joel Esler (jesler); snort-devel at lists.sourceforge.net
>>>>>>>>>
>>>>>>>>> *Subject:* Re: [Snort-devel] Fwd: Snort blocking connection but
>>>>>>>>> not logging the drop
>>>>>>>>>
>>>>>>>>>    Can you confirm you received my PCAP file?  I would really
>>>>>>>>> like to get this issue resolved so I can work with their API.
>>>>>>>>>
>>>>>>>>> Let me know the status please.
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> On Fri, May 9, 2014 at 9:02 AM, Cody Brugh <cbrugh at ...2499...>wrote:
>>>>>>>>>
>>>>>>>>>>  Attached is the pcap of the stamps.com packet capture... can
>>>>>>>>>> someone check and see what I should do?
>>>>>>>>>>
>>>>>>>>>>  Thanks,
>>>>>>>>>> Cody
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> On Fri, May 9, 2014 at 8:19 AM, Russ Combs (rucombs) <
>>>>>>>>>> rucombs at ...3461...> wrote:
>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>  ------------------------------
>>>>>>>>>>> *From:* Joel Esler (jesler)
>>>>>>>>>>> *Sent:* Thursday, May 08, 2014 8:51 PM
>>>>>>>>>>> *To:* Cody Brugh
>>>>>>>>>>> *Cc:* snort-devel at lists.sourceforge.net
>>>>>>>>>>> *Subject:* Re: [Snort-devel] Fwd: Snort blocking connection but
>>>>>>>>>>> not logging the drop
>>>>>>>>>>>
>>>>>>>>>>>   Can you send your configuration file, and a packet capture of
>>>>>>>>>>> the session?
>>>>>>>>>>>
>>>>>>>>>>>  * Can you also send your usr1 / shutdown stats?
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> --
>>>>>>>>>>> Joel Esler
>>>>>>>>>>> Sent from my iPhone
>>>>>>>>>>>
>>>>>>>>>>> On May 8, 2014, at 20:49, "Cody Brugh" <cbrugh at ...2499...> wrote:
>>>>>>>>>>>
>>>>>>>>>>>   Hi,
>>>>>>>>>>>
>>>>>>>>>>>  Our dev team is trying to work with stamps.com API however our
>>>>>>>>>>> in-line snort box is blocking the return connection for unknown reasons.
>>>>>>>>>>> When I turn off snort the connection flows perfectly.  Looking at snorby I
>>>>>>>>>>> see no event of the connection being dropped.  I've included the command we
>>>>>>>>>>> are running from a internal server that is behind the snort.  I also
>>>>>>>>>>> included the tcpdump from this same server for the connection.
>>>>>>>>>>>
>>>>>>>>>>> wget https://216.52.211.91/label/health.aspx
>>>>>>>>>>> --2014-05-08 20:37:33--  https://216.52.211.91/label/health.aspx
>>>>>>>>>>> Connecting to 216.52.211.91:443... connected.
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> 20:37:33.443962 IP 10.2.2.1.52661 > 216.52.211.91.443: Flags
>>>>>>>>>>> [F.], seq 3298140140, ack 2463587275, win 8208, options [nop,nop,TS val
>>>>>>>>>>> 2824990869 ecr 3731400338], length 0
>>>>>>>>>>> 20:37:33.444478 IP 216.52.211.91.443 > 10.2.2.1.52661: Flags
>>>>>>>>>>> [R.], seq 1, ack 1, win 8208, length 0
>>>>>>>>>>> 20:37:33.989510 IP 10.2.2.1.59800 > 216.52.211.91.443: Flags
>>>>>>>>>>> [S], seq 3306929108, win 65535, options [mss 1460,nop,wscale 3,sackOK,TS
>>>>>>>>>>> val 2824990923 ecr 0], length 0
>>>>>>>>>>> 20:37:34.071548 IP 216.52.211.91.443 > 10.2.2.1.59800: Flags
>>>>>>>>>>> [S.], seq 361712399, ack 3306929109, win 4140, options [mss 1380,nop,wscale
>>>>>>>>>>> 3,nop,nop,TS val 3731482846 ecr 2824990923,sackOK,eol], length 0
>>>>>>>>>>> 20:37:34.071610 IP 10.2.2.1.59800 > 216.52.211.91.443: Flags
>>>>>>>>>>> [.], ack 1, win 8208, options [nop,nop,TS val 2824990932 ecr 3731482846],
>>>>>>>>>>> length 0
>>>>>>>>>>> 20:37:34.071750 IP 10.2.2.1.59800 > 216.52.211.91.443: Flags
>>>>>>>>>>> [P.], ack 1, win 8208, options [nop,nop,TS val 2824990932 ecr 3731482846],
>>>>>>>>>>> length 139
>>>>>>>>>>> 20:37:34.154367 IP 216.52.211.91.443 > 10.2.2.1.59800: Flags
>>>>>>>>>>> [.], ack 140, win 517, options [nop,nop,TS val 3731482928 ecr 2824990932],
>>>>>>>>>>> length 1368
>>>>>>>>>>> 20:37:34.154462 IP 216.52.211.91.443 > 10.2.2.1.59800: Flags
>>>>>>>>>>> [.], ack 140, win 517, options [nop,nop,TS val 3731482928 ecr 2824990932],
>>>>>>>>>>> length 1368
>>>>>>>>>>> 20:37:34.154490 IP 10.2.2.1.59800 > 216.52.211.91.443: Flags
>>>>>>>>>>> [.], ack 2737, win 7877, options [nop,nop,TS val 2824990940 ecr
>>>>>>>>>>> 3731482928], length 0
>>>>>>>>>>>
>>>>>>>>>>> 20:37:44.153373 IP 216.52.211.91.443 > 10.2.2.1.59800: Flags
>>>>>>>>>>> [R.], seq 4233:4288, ack 140, win 534, length 55
>>>>>>>>>>>
>>>>>>>>>>>  any help or suggestions would be great, I would like to disable
>>>>>>>>>>> the rule that is blocking this connection but like I said I cannot see
>>>>>>>>>>> which rule blocked it.
>>>>>>>>>>>
>>>>>>>>>>>  Thanks.
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> ------------------------------------------------------------------------------
>>>>>>>>>>> Is your legacy SCM system holding you back? Join Perforce May 7
>>>>>>>>>>> to find out:
>>>>>>>>>>> • 3 signs your SCM is hindering your productivity
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>>>>>>>>>>>
>>>>>>>>>>>  _______________________________________________
>>>>>>>>>>> Snort-devel mailing list
>>>>>>>>>>> Snort-devel at lists.sourceforge.net
>>>>>>>>>>> https://lists.sourceforge.net/lists/listinfo/snort-devel
>>>>>>>>>>> Archive:
>>>>>>>>>>>
>>>>>>>>>>> http://sourceforge.net/mailarchive/forum.php?forum_name=snort-devel
>>>>>>>>>>>
>>>>>>>>>>> Please visit http://blog.snort.org for the latest news about
>>>>>>>>>>> Snort!
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>
>
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