Snort mailing list archives
packet modifications not working
From: eboehnlein () aol com
Date: Tue, 31 May 2005 10:56:24 -0400
Problem: snort_inline modified packets are not being forwarded, instead it appears the original unaltered packet is
being forwarded. Also, dropped packets rules when triggered make either snort_inline and/or the sending workstation
hang.
Background:
Running Suse linux 9.0 (i586) - Kernel 2.4.30
with patch ebtables-brnf-9_vs_2.4.30.diff
iptables-1.2.8
libpcap-0.8.3
pcre-5.0
libnet-1.0.2a
snort-2.3.3
--- snort NID with the above configuration works this point: rules are triggered and events are logged --- then
include the following ---
iptables-1.3.1
bridge-utils-1.0.4
snort_inline-2.3.0-RC1
bridge script to define bridge [eth1+eth2]=br0
## clear iptables
$IPTABLES -F
$IPTABLES -A FORWARD -j QUEUE
## turn forwrding off
$ECHO 0 > /proc/sys/net/ipv4/ip_forward
The ip queue module is loaded by executing:
insmod ip_queue
Start snort
>snort_inline -v -Q -c /etc/snort_inline/snort_inline.conf
--- at this point snort inline is active and traffic is passing through bridge both direcitons --alerts are logged --
replace and drop not working but actions are logged ++
-----------------------------------------------------
Snort Rules Are defined to trigger on a HTTP query from a network:
+ Alert when any HTTP traffic is sent from workstation segment -- successfully alerts and logs.
+ Alert and replace content when a specific word is being used -- successfully alerts and logs.
Symptoms: [Verified using traces and dumps]
+ all unaltered traffic flows both ways over the bridge
+ snort_inline alert rules are triggered and logged - (using content rules)
+ snort_inline alert/replace rules are triggered and logged; however, it appears the it is the original(unaltered)
packet that being forwarded.
I suspect that snort_inline (via libnet) is not handling the modified packet correctly. I have recompiled and
reconfigured the kernel and all the software several times with no apparent errors being generated.
Any thoughts how to proceed from here?
Ed
Current thread:
- packet modifications not working eboehnlein (Jun 02)
- Re: packet modifications not working Joel Esler (Jun 02)
- Re: packet modifications not working Will Metcalf (Jun 02)
