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

Cody Brugh cbrugh at ...2499...
Mon May 12 12:53:13 EDT 2014


What all is the normalizer used for?  Will turning it off make me vulnerable?

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 ...3483.....> 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 ...3484......> 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 ...3484......> 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/20140512/696a1396/attachment.html>


More information about the Snort-devel mailing list