[Snort-users] Snort 2.9.6.2 inline mode problem

James Lay jlay at ...13475...
Wed Aug 27 09:10:06 EDT 2014


On Mon, 2014-08-25 at 17:18 +0000, Y M wrote:
> Please post your snort.conf, sanitizing any private info. Also the
> command you use to run Snort.
> 
> 
> 
> YM
> 
> 
> 
> ______________________________________________________________________
> Date: Sun, 24 Aug 2014 19:58:22 +0200
> Subject: Re: [Snort-users] Snort 2.9.6.2 inline mode problem
> From: demonsdebason at ...11827...
> To: snort at ...15979...
> CC: snort-users at lists.sourceforge.net
> 
> 
> 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 at ...15979...> 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 at ...11827...
>         To: snort at ...15979...
>         
>         
>         CC: snort-users at 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 at ...15979...>
>         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 at ...11827...
>                 To: snort at ...15979...
>                 
>                 
>                 
>                 
>                 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 at ...15979...> wrote:
>                 
>                         
>                         inline.
>                         
>                         
>                         ______________________________________________
>                         Date: Sun, 24 Aug 2014 05:02:13 +0200
>                         From: demonsdebason at ...11827...
>                         To: snort-users at 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. 
>                         
>                         
>                         
>                         -- 
>                         Aut viam inveniam aut faciam
>                         :wq!
>                         
>                         
>                         
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>                 
>                 
>                 
>                 
>                 -- 
>                 Aut viam inveniam aut faciam
>                 :wq!
>                 
>         
>         
>         
>         
>         -- 
>         Aut viam inveniam aut faciam
>         :wq!
>         
> 
> 
> 
> 
> -- 
> Aut viam inveniam aut faciam
> :wq!
> 
> 
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And additionally, was this using just straight afpacket where snort
actually sets up the bridge from eth0 to eth1, or was this using nfq?
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