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

Cody Brugh cbrugh at ...2499...
Mon May 12 16:09:00 EDT 2014


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/20140512/16028777/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: snort.log
Type: application/octet-stream
Size: 99159 bytes
Desc: not available
URL: <https://lists.snort.org/pipermail/snort-devel/attachments/20140512/16028777/attachment.obj>


More information about the Snort-devel mailing list