Snort mailing list archives
Re: Trigger anomalies (on LXC container versus host)
From: "Al Lewis (allewi)" <allewi () cisco com>
Date: Mon, 4 May 2015 01:03:17 +0000
Try running it with the "-k none" flag set (to ignore checksums). Albert Lewis QA Software Engineer SOURCEfire, Inc. now part of Cisco 9780 Patuxent Woods Drive Columbia, MD 21046 Phone: (office) 443.430.7112 Email: allewi () cisco com -----Original Message----- From: Al Lewis (allewi) Sent: Sunday, May 03, 2015 8:51 PM To: Chris Cc: snort-users () lists sourceforge net Subject: Re: [Snort-users] Trigger anomalies (on LXC container versus host) Its pretty hard to say without the pcap and conf file. Albert Lewis QA Software Engineer SOURCEfire, Inc. now part of Cisco 9780 Patuxent Woods Drive Columbia, MD 21046 Phone: (office) 443.430.7112 Email: allewi () cisco com -----Original Message----- From: Chris [mailto:berzerkatives () gmail com] Sent: Sunday, May 03, 2015 8:08 PM To: Al Lewis (allewi) Cc: snort-users () lists sourceforge net Subject: Re: [Snort-users] Trigger anomalies (on LXC container versus host) Hi Al, I've taken the pcap capture on the hypervisor (which is where it will trigger), and run it through Snort using -r, and I see that the correct number of packets are being read from the capture, and that one of them is processed (I guess for its for HTTP payload, whereas the other packets I believe are just initialising the TCP connection), however it doesn't cause it to trigger. I am certain that the packet that triggers the alert is in here, as looking through the earlier Snort alert lot I see this. [**] [1:1646:5] WEB-CGI test.cgi access [**] [Classification: access to a potentially vulnerable web application] [Priority: 2] 05/03-22:54:17.553955 XXX.XXX.XXX.XXX:55208 -> YYY.YYY.YYY.YYY:80 TCP TTL:64 TOS:0x0 ID:33526 IpLen:20 DgmLen:137 DF ***AP*** Seq: 0x934BB66C Ack: 0xF99F9563 Win: 0x3890 TcpLen: 32 And in the pcap capture I have an identically timestamped and addressed packet. 22:54:17.553955 IP XXX.XXX.XXX.XXX.55208 > YYY.YYY.YYY.YYY.80: Flags [P.], seq 0:85, ack 1, win 229, options [nop,nop,TS val 9149570 ecr 785127305], length 85 But loading it up, with identical command line arguments in addition to the -r, minus the -D, and having it log to a brand new place, fails to log/trigger anything. Here's the rule that one would expect to trigger. alert tcp $EXTERNAL_NET any -> $HTTP_SERVERS $HTTP_PORTS (msg:"WEB-CGI test.cgi access"; flow:to_server,established; uricontent:"/test.cgi"; nocase; classtype:web-application-activity; sid:1646; rev:5;) I'm left to think that I must be making a mistake somehow with my playback testing, but I'm not sure what. Any ideas? On Sun, 3 May 2015 23:03:55 +0000 "Al Lewis (allewi)" <allewi () cisco com> wrote:
The pcaps are needed for replay and testing against. As a test... if you run snort from both of your other instances and replay the packets the outputs should be the same when using the "-r" flag. If the results are the same then you know you have a problem with your setup and with packets coming off the wire. You could also replay the pcaps (using tcpreplay ) and look at the exit stats to see if the packets are making it into snort correctly. Albert Lewis QA Software Engineer SOURCEfire, Inc. now part of Cisco 9780 Patuxent Woods Drive Columbia, MD 21046 Phone: (office) 443.430.7112 Email: allewi () cisco com -----Original Message----- From: Chris [mailto:berzerkatives () gmail com] Sent: Sunday, May 03, 2015 6:33 PM To: Al Lewis (allewi) Cc: snort-users () lists sourceforge net Subject: Re: [Snort-users] Trigger anomalies (on LXC container versus host) Hi Albert, Absolutely, thanks for getting back to me, and I'd be more than happy to provide extra information. I'm guessing pcaps wouldn't be of any use as running tcpdump on the container and hypervisor at the same time yielded the exact same packets (that one system flagged, and the other ignored). I've just taken a moment to diff the packet capture that would be expected to trigger Snort, and the only difference is a very slight timestamp difference. Like I say, the configs are pretty much vanilla Debian with the smallest amount of tweaking for interface names, and not much else. Should I just tar up /etc/snort and send it over? On Sun, 3 May 2015 19:04:27 +0000 "Al Lewis (allewi)" <allewi () cisco com> wrote:Hello, It would help if you could provide some pcaps of the traffic in question. Also a snort.conf or the rules that are involved. Thanks! Albert Lewis QA Software Engineer SOURCEfire, Inc. now part of Cisco 9780 Patuxent Woods Drive Columbia, MD 21046 Phone: (office) 443.430.7112 Email: allewi () cisco com -----Original Message----- From: Chris [mailto:berzerkatives () gmail com] Sent: Sunday, May 03, 2015 9:31 AM To: snort-users () lists sourceforge net Subject: [Snort-users] Trigger anomalies (on LXC container versus host) I'm observing a problematic difference in behaviour between two instances of Snort that are configured identically (recursive diff'ed their config dirs, and compared their initialisation outputs) aside from the required differences (interfaces names) as one is running inside an LXC container, listening to its single virtual interface, and the other instance is on the hypervisor/base OS listening to the bridge interface that all the containers are attached to. The container receives traffic through NAT'ing rules on the hypervisor. What I see is that certain rules aren't being triggered on the container instance of Snort, but are being triggered on the hypervisor. This is despite being able to see the packets that trigger these rules appear on both machines (hypervisor and container) using tcpdump to view the respective interfaces that Snort is configured to listen on. Specifically, the rules that I've noticed are being ignored are those that involve HTTP header inspection, like GET /test.cgi. Like I said, I can see what look like the EXACT SAME packets on these respective interfaces, so I've tried the following troubleshooting without any luck. * Switching off Snort on the hypervisor in case it was interfering. * Creating a rule that triggers for any packet that is considered to be web traffic (i.e. EXTERNAL any -> HTTP HTTP_PORT) and this triggers for those packets without issue, so it's not a problem with those variables being misconfigured. * Wondering whether LXC doesn't properly isolate the interfaces somehow, so I tried configuring the container Snort to use the bridge interface on the hypervisor, however it correctly wasn't able to use it (as it didn't exist inside the container, of course). So I'm stuck as to where to go next. The container is where I want Snort to be running, as it's my load balancer (including SSL termination) so that's where I would like to detect and block rogue traffic. The only reason that I run it on the hypervisor is to just see whether any concerning traffic is bypassing the load balancer, and whether undesirable traffic is being generated by services behind it. Thanks for your time, I really hope someone can shed some light on this frustrating situation. Very happy to answer any questions about the setup, including configuration specifics, though they're essentially vanilla installions on Debian Wheezy straight out of apt. -------------------------------------------------------------------- -- -------- One dashboard for servers and applications across Physical-Virtual-Cloud Widest out-of-the-box monitoring support with 50+ applications Performance metrics, stats and reports that give you Actionable Insights Deep dive visibility with transaction tracing using APM Insight. http://ad.doubleclick.net/ddm/clk/290420510;117567292;y _______________________________________________ Snort-users mailing list Snort-users () lists sourceforge net Go to this URL to change user options or unsubscribe: https://lists.sourceforge.net/lists/listinfo/snort-users Snort-users list archive: http://sourceforge.net/mailarchive/forum.php?forum_name=snort-users Please visit http://blog.snort.org to stay current on all the latest Snort news!
------------------------------------------------------------------------------ One dashboard for servers and applications across Physical-Virtual-Cloud Widest out-of-the-box monitoring support with 50+ applications Performance metrics, stats and reports that give you Actionable Insights Deep dive visibility with transaction tracing using APM Insight. http://ad.doubleclick.net/ddm/clk/290420510;117567292;y _______________________________________________ Snort-users mailing list Snort-users () lists sourceforge net Go to this URL to change user options or unsubscribe: https://lists.sourceforge.net/lists/listinfo/snort-users Snort-users list archive: http://sourceforge.net/mailarchive/forum.php?forum_name=snort-users Please visit http://blog.snort.org to stay current on all the latest Snort news! ------------------------------------------------------------------------------ One dashboard for servers and applications across Physical-Virtual-Cloud Widest out-of-the-box monitoring support with 50+ applications Performance metrics, stats and reports that give you Actionable Insights Deep dive visibility with transaction tracing using APM Insight. http://ad.doubleclick.net/ddm/clk/290420510;117567292;y _______________________________________________ Snort-users mailing list Snort-users () lists sourceforge net Go to this URL to change user options or unsubscribe: https://lists.sourceforge.net/lists/listinfo/snort-users Snort-users list archive: http://sourceforge.net/mailarchive/forum.php?forum_name=snort-users Please visit http://blog.snort.org to stay current on all the latest Snort news!
Current thread:
- Trigger anomalies (on LXC container versus host) Chris (May 03)
- Re: Trigger anomalies (on LXC container versus host) Doug Burks (May 03)
- Re: Trigger anomalies (on LXC container versus host) Chris (May 03)
- Re: Trigger anomalies (on LXC container versus host) Al Lewis (allewi) (May 03)
- Re: Trigger anomalies (on LXC container versus host) Chris (May 03)
- Re: Trigger anomalies (on LXC container versus host) Al Lewis (allewi) (May 03)
- Re: Trigger anomalies (on LXC container versus host) Chris (May 03)
- Re: Trigger anomalies (on LXC container versus host) Al Lewis (allewi) (May 03)
- Re: Trigger anomalies (on LXC container versus host) Al Lewis (allewi) (May 03)
- Re: Trigger anomalies (on LXC container versus host) Chris (May 05)
- Re: Trigger anomalies (on LXC container versus host) Al Lewis (allewi) (May 05)
- Re: Trigger anomalies (on LXC container versus host) Chris (May 03)
- Re: Trigger anomalies (on LXC container versus host) Doug Burks (May 03)
- Re: Trigger anomalies (on LXC container versus host) waldo kitty (May 04)
- Re: Trigger anomalies (on LXC container versus host) Chris (May 05)