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

Cody Brugh cbrugh at ...2499...
Mon May 12 16:32:20 EDT 2014


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?



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.
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> ------------------------------------------------------------------------------
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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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