Re: Snort and GTP encapsulation info

[Ana Serrano Mamolar <B00315494 () studentmail uws ac uk>]

Thanks Albert,

My rules are similar than yours, but with gtp_version and gt_type:

alert udp any any -> any any ( msg:"gtp_version"; sid:10000003; gtp_version:1;)

alert udp any any -> any any ( msg:"gtp_type"; sid:10000004; gtp_type:255; )


So, when I add any of these gtp params, the alert is not triggering. It seems like is not processing gtp information 
correctly. My snort.conf is like the manual says:


config enable_gtp
portvar GTP_PORTS [2152,3386]
preprocessor gtp: ports { 2123 3386 2152 }

Thanks




________________________________
From: Al Lewis (allewi) <allewi () cisco com>
Sent: 13 February 2017 12:04:55
To: Ana Serrano Mamolar
Cc: snort-users () lists sourceforge net
Subject: Re: [Snort-users] Snort and GTP encapsulation info

Example attached.

cliffjumper$ ./bin/snort -c etc/ANNA-gtp.conf -r etc/ANNA-gtp.pcap -Acmg -k none -q
09/08-20:20:15.504682  [**] [1:1:0] gtp_info numeric [**] [Priority: 0] {UDP} 10.1.2.3:48620 -> 10.9.8.7:3386
09/08-20:20:15.504682 02:01:02:03:04:05 -> 02:09:08:07:06:05 type:0x800 len:0x6C
10.1.2.3:48620 -> 10.9.8.7:3386 UDP TTL:64 TOS:0x0 ID:1 IpLen:20 DgmLen:94
Len: 66
10 10 00 2E 00 00 00 00 00 00 00 00 00 00 00 00  ................
00 00 00 00 06 00 00 01 0F 02 10 00 01 11 00 00  ................
80 00 02 01 21 83 00 07 65 78 70 6C 6F 69 74 85  ....!...exploit.
00 04 C0 A8 01 01 85 00 04 C0 A8 01 01 86 00 02  ................
00 00                                            ..

=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+


09/08-20:20:15.504901  [**] [1:2:0] gtp_info numeric [**] [Priority: 0] {UDP} 10.1.2.3:48620 -> 10.9.8.7:2123
09/08-20:20:15.504901 02:01:02:03:04:05 -> 02:09:08:07:06:05 type:0x800 len:0x45
10.1.2.3:48620 -> 10.9.8.7:2123 UDP TTL:64 TOS:0x0 ID:1 IpLen:20 DgmLen:55
Len: 27
58 20 00 17 00 00 00 01 00 01 00 00 5D 00 00 00  X ..........]...
47 00 07 00 65 78 70 6C 6F 69 74                 G...exploit

=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+



alert udp any any -> any any ( msg:"gtp_info numeric"; sid:1; gtp_info:131; )
alert udp any any -> any any ( msg:"gtp_info numeric"; sid:2; gtp_info:71; )



Albert Lewis
ENGINEER.SOFTWARE ENGINEERING
SOURCEfire, Inc. now part of Cisco
Email: allewi () cisco com<mailto:allewi () cisco com>

From: allewi <allewi () cisco com<mailto:allewi () cisco com>>
Date: Monday, February 13, 2017 at 6:42 AM
To: Ana Serrano Mamolar <B00315494 () studentmail uws ac uk<mailto:B00315494 () studentmail uws ac uk>>, "Joel Esler 
(jesler)" <jesler () cisco com<mailto:jesler () cisco com>>
Cc: 'snort-users' <snort-users () lists sourceforge net<mailto:snort-users () lists sourceforge net>>
Subject: Re: [Snort-users] Snort and GTP encapsulation info

Can you send us the pcap please?


Albert Lewis
ENGINEER.SOFTWARE ENGINEERING
SOURCEfire, Inc. now part of Cisco
Email: allewi () cisco com<mailto:allewi () cisco com>

From: Ana Serrano Mamolar <B00315494 () studentmail uws ac uk<mailto:B00315494 () studentmail uws ac uk>>
Date: Monday, February 13, 2017 at 6:29 AM
To: "Joel Esler (jesler)" <jesler () cisco com<mailto:jesler () cisco com>>
Cc: 'snort-users' <snort-users () lists sourceforge net<mailto:snort-users () lists sourceforge net>>
Subject: Re: [Snort-users] Snort and GTP encapsulation info


Hi again,


I can not make Snort gtp preprocessor and decoder working.

I have reviewed many times the snort manual and follow instructions to configure it to be able to manage gtp_rules. 
These are the lines in my snort.conf related to gtp:

config enable_gtp

portvar GTP_PORTS [2152,3386]

preprocessor gtp: ports { 2123 3386 2152 }


I have also checked that stream5 and frag3 are actived, and I saw that they were by default in my configuration. Is 
there any other way to check it better?


Then, I have tried with a pcap I have that includes GTP encapsulation. I can see that with Wireshark, and also its gtp 
version and message type.

Unfortunately, when I add some gtp_version ( I tried with the three, just in case) or gtp_type in my rule it doesn't 
trigger the Alert.

My alert is a very simple one for UDP, that used to be triggered with this pcap before adding ant gtp rule.


Does anybody have had the same problem or know how could it be solved?

Thanks


________________________________
From: Ana Serrano Mamolar <B00315494 () studentmail uws ac uk<mailto:B00315494 () studentmail uws ac uk>>
Sent: 09 February 2017 11:10:37
To: Joel Esler (jesler)
Cc: snort-users () lists sourceforge net<mailto:snort-users () lists sourceforge net>
Subject: Re: [Snort-users] Snort and GTP encapsulation info


Thanks Joel,

I didn't know this tool until know, very useful. Now, I have run it with my last snort.u2 log, but I can not get any 
gtp information.

As I said I have already enabled gtp in my config file. Should I use any special option when running Snort to obtain 
this gtp information?

Thanks


________________________________
From: Joel Esler (jesler) <jesler () cisco com<mailto:jesler () cisco com>>
Sent: 08 February 2017 20:06:32
To: Ana Serrano Mamolar
Cc: snort-users () lists sourceforge net<mailto:snort-users () lists sourceforge net>
Subject: Re: [Snort-users] Snort and GTP encapsulation info

It may not be a field that is inserted into the db.  It may be in the unified2 output file that you can access with 
u2spewfoo in the contrib/ directory.

--
Joel Esler | Talos: Manager | jesler () cisco com<mailto:jesler () cisco com>






On Feb 8, 2017, at 2:54 PM, Ana Serrano Mamolar <B00315494 () studentmail uws ac uk<mailto:B00315494 () studentmail uws 
ac uk>> wrote:

Hi all,
Again with an encapsulation question.
I am trying to understand how Snort manage GTP encapsulation, that I know that is supported. I already enable gtp in my 
config file by " config enable_gtp".
I run Snort with different pcaps that I have that include GTP and trying to see which info I obtained from Snort with a 
very silly rule to be sure that is triggerred.
My question is the following: Does somebody know where in the database is stored the TEID ( tunnel identifier ) of the 
packet that triggered the alert? . I have seen in Snort source code that it's parsed. But then I can not find it in the 
database.
Thanks
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