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

Cody Brugh cbrugh at ...2499...
Mon May 12 16:38:45 EDT 2014


Another odd thing is if I run the API command 10 times I would say 2 or 3
will complete successfully with snort running in-line as IPS....

This is very odd.


On Mon, May 12, 2014 at 4:32 PM, Cody Brugh <cbrugh at ...2499...> wrote:

> 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.
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> ------------------------------------------------------------------------------
>>>>>>>>>> Is your legacy SCM system holding you back? Join Perforce May 7
>>>>>>>>>> to find out:
>>>>>>>>>> • 3 signs your SCM is hindering your productivity
>>>>>>>>>> • Requirements for releasing software faster
>>>>>>>>>> • Expert tips and advice for migrating your SCM now
>>>>>>>>>> http://p.sf.net/sfu/perforce
>>>>>>>>>>
>>>>>>>>>>  _______________________________________________
>>>>>>>>>> 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!
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.snort.org/pipermail/snort-devel/attachments/20140512/c76f2bf5/attachment.html>


More information about the Snort-devel mailing list