Snort mailing list archives

Re: Snort 2.9.6.2 inline mode problem


From: Debason Shockre <demonsdebason () gmail com>
Date: Sun, 24 Aug 2014 19:58:22 +0200

I have already tried with this rule:
drop icmp 192.168.1.2 any -> 8.8.8.8 any (msg: "NEW TEST"; sid:10666;)

Also modified 384 ICMP rule:
drop icmp $EXTERNAL_NET any -> $HOME_NET any (msg:"PROTOCOL-ICMP PING";
icode:0; itype:8; metadata:ruleset community; classtype:misc-activity;
sid:384; rev:8;)

Set HOME_NET to any, restarted Snort and got the same crap:
PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
From 8.8.8.8 icmp_seq=1 Destination Port Unreachable
64 bytes from 8.8.8.8: icmp_seq=1 ttl=46 time=40.6 ms
From 8.8.8.8 icmp_seq=2 Destination Port Unreachable
From 8.8.8.8 icmp_seq=3 Destination Port Unreachable
64 bytes from 8.8.8.8: icmp_seq=3 ttl=46 time=40.7 ms

I've set additional rule:
drop icmp any any -> any any (msg: "NEW TEST"; sid:10666;)

...and am getting:
PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
From 8.8.8.8 icmp_seq=1 Destination Port Unreachable
64 bytes from 8.8.8.8: icmp_seq=1 ttl=46 time=40.2 ms
From 8.8.8.8 icmp_seq=2 Destination Port Unreachable
From 8.8.8.8 icmp_seq=3 Destination Port Unreachable
From 8.8.8.8 icmp_seq=4 Destination Port Unreachable
From 8.8.8.8 icmp_seq=5 Destination Port Unreachable
64 bytes from 8.8.8.8: icmp_seq=5 ttl=46 time=40.6 ms
From 8.8.8.8 icmp_seq=6 Destination Port Unreachable

Tried with and without normalization, works the same.

Snort is blocking, but seems not to be able to drop all the traffic:
08/24-19:56:03.511103  [Drop] [**] [1:10666:0] NEW TEST [**] [Priority: 0]
{ICMP} 192.168.1.2 -> 8.8.8.8
08/24-19:56:03.511145  [Drop] [**] [1:10666:0] NEW TEST [**] [Priority: 0]
{ICMP} x.x.x.x -> 8.8.8.8
08/24-19:56:03.551092  [Drop] [**] [1:10666:0] NEW TEST [**] [Priority: 0]
{ICMP} 8.8.8.8 -> 192.168.1.2
08/24-19:56:03.551058  [Drop] [**] [1:10666:0] NEW TEST [**] [Priority: 0]
{ICMP} 8.8.8.8 -> x.x.x.x



On Sun, Aug 24, 2014 at 6:29 PM, Y M <snort () outlook com> wrote:


Ok, assuming you are setup this way:

Internet <---> eth2 | IPS | eth1 <---> local, where eth1 and eth2 are the
listening (promiscuous) interfaces and through which traffic is passing.
When you force Snort into inline mode using afpacket, Snort (logically)
bridges the interfaces together to let the traffic pass, otherwise drop it
when matches occur. Looking again at the rule you have, both destinations
are local. What happens if you change both destinations (HOME_NET and
EXTERNAL_NET) to any/any? Better, take rule sid:384 and modify it and try
to ping an external source and see what happens. For troubleshooting
purposes only, run Snort with -A console or -A cmg so you can see whats
going directly on the console (without -D).

Also, do you have normalization enabled?

YM
------------------------------
Date: Sun, 24 Aug 2014 17:50:27 +0200

Subject: Re: [Snort-users] Snort 2.9.6.2 inline mode problem
From: demonsdebason () gmail com
To: snort () outlook com
CC: snort-users () lists sourceforge net


Here is the setup:

INTERNET <--> | IPS/router | <--> | local machines |

IPS box has 4 interfaces, where 2 have an address, others don't. It seemed
illogical to set Snort to listen on interfaces where no traffic is passing
through.
When I set Snort it to use unaddressed interfaces, nothing happens meaning
no alerts are recorded and ICMP echo test isn't working.
Tried setting up bride interfaces and assigning the two unaddressed
interface to Snort, same results.
The only results I get is having Snort listening the interfaces traffic
traverse though.


On Sun, Aug 24, 2014 at 4:24 PM, Y M <snort () outlook com> wrote:

How are you testing/connecting the client (icmp echo request sender), the
sensor, and the receiver of the icmp? The NICs that Snort is using to
receive --> pass/drop --> forward traffic should be inline with no IP
addresses. From your description, it seems that you are using the same
interface to ping the box as well as do the IPS work.

P.S.: Please respond to the list and not only to myself. Its a mutual
benefit.

YM

------------------------------
Date: Sun, 24 Aug 2014 14:00:20 +0200
Subject: Re: [Snort-users] Snort 2.9.6.2 inline mode problem
From: demonsdebason () gmail com
To: snort () outlook com


The same behavior when running with 'eth1:eth2'.
Yeah, the interfaces are in promiscuous, silly me.
Any ideas?


On Sun, Aug 24, 2014 at 7:34 AM, Y M <snort () outlook com> wrote:


inline.
------------------------------
Date: Sun, 24 Aug 2014 05:02:13 +0200
From: demonsdebason () gmail com
To: snort-users () lists sourceforge net
Subject: [Snort-users] Snort 2.9.6.2 inline mode problem


Hi all.
I've been working on my Snort IPS for some time now.
Noticed that 'drop' rules are working half-way, I have set the test rule
to drop ICMP coming to the sensor from local machine:
drop icmp 192.168.1.2 any -> 192.168.1.1 any (msg: "Test rule";
sid:110011;)

Alerts get logged and can view them via BASE, but when I ping from .2 to
.1 I get this:
PING 192.168.1.1 (192.168.1.1) 56(84) bytes of data.
64 bytes from 192.168.1.1

: icmp_seq=1 ttl=64 time=0.216 ms
From 192.168.1.1 icmp_seq=1 Destination Port Unreachable
64 bytes from 192.168.1.1

: icmp_seq=2 ttl=64 time=0.269 ms
From 192.168.1.1 icmp_seq=2 Destination Port Unreachable
64 bytes from 192.168.1.1

: icmp_seq=3 ttl=64 time=0.221 ms

So some of them are getting 'blocked'.

When I shutdown Snort I's all fine:
64 bytes from 192.168.1.1

: icmp_seq=8 ttl=64 time=0.226 ms
64 bytes from 192.168.1.1

: icmp_seq=9 ttl=64 time=0.201 ms
64 bytes from 192.168.1.1

: icmp_seq=10 ttl=64 time=0.253 ms
64 bytes from 192.168.1.1

: icmp_seq=11 ttl=64 time=0.204 ms

Here is my info:

   ,,_     -*> Snort! <*-
  o"  )~   Version 2.9.6.2 GRE (Build 77)
   ''''    By Martin Roesch & The Snort Team:
http://www.snort.org/snort/snort-team
           Copyright (C) 2014 Cisco and/or its affiliates. All rights
reserved.
           Copyright (C) 1998-2013 Sourcefire, Inc., et al.
           Using libpcap version 1.4.0
           Using PCRE version: 7.8 2008-09-05
           Using ZLIB version: 1.2.3
+++++++++++++++++++++++++++
snort    41104  4.6  2.0 1675528 1342832 ?     Ssl  04:48   0:00
/usr/sbin/snort -D -i eth1::eth2 -u snort -g snort -c /etc/snort/snort.conf
-Q --daq-mode inline -k none
+++++++++++++++++++++++++++

# Looks like you have double colons "eth1::eth2", as opposed to one colon
"eth1:eth2". Not sure if the double colons are causing the partial drops.


snort --daq-list
Available DAQ modules:
pcap(v3): readback live multi unpriv
ipfw(v3): live inline multi unpriv
dump(v2): readback live inline multi unpriv
afpacket(v5): live inline multi unpriv

++++++++++++++++++++++++++
snort.conf:

config policy_mode:inline
config daq: afpacket
config daq_dir: /usr/lib64/daq
config daq_mode: inline
config daq_var: buffer_size_mb=1024


I've tried dropping all the ICMPs in the iptables, results are as
expected, but Snort still logs the alerts.
Do you have any idea what is the issue here?

# Does Snort log the requests or replies or both? I would image if the NIC
is promiscuous, then it would still see the requests.


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:wq!
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