Snort mailing list archives
Re: Does ICMP detection work or what?
From: Dragos Ruiu <dr () kyx net>
Date: Fri, 29 Jun 2001 03:38:26 -0700
The defragger has had several fixes since Snort 1.7 that could account for the behaviour you see (esp. on sparc boxen). I posted a new one to snort-devel this afternoon, since then another small problem has been fixed in this latest version v1.4.... This should also be backwards compatible to snort 1.7 source trees. (or 1.6 for that matter, but your really ought to think about upgrading if you're there!) Please replace spp_defrag.c with this latest v1.4 one and let me know if your problem still occurs. Please contact me if it is still in error, and further information may be gleaned by enbling more diagnostics by defining DEBUG in the defragger code. Notes about the release from the snort-devel posting are attached below with the code. thanks, --dr On Fri, 29 Jun 2001, François Désarménien wrote:
Thu, 28 Jun 2001 17:22:27 -0600 (MDT) Ryan Russell <ryan () securityfocus com> wrote:On Thu, 28 Jun 2001, Sheahan, Paul (PCLN-NW) wrote: Ping and ICMP aren't the same thing, ping only accounts for two ICMP types, and there are quite a few more (as evidenced by your examples.) What kind of firewall do you have, and what exactly does the rule say?Couldn't it be related to the problem Phil told us last night :Phil Wood wrote : In my case the problem of trash icmp types and codes is the result of a problem with snort. It appears related to the defrag preprocessor. I have documented, using tcpdump and snort in parallel, that valid ICMP packets (as seen by tcpdump), end up in snort with some memory (not associated with any packet) appended to a perfectly valid IP header (with proto of ICMP). Tcpdump shows two fragments (out of order) which together make up an icmp packet. Snort's defrag constructs the complete ICMP packet with the identical IP header, but crud from some place in snort's memory as ICMP header and DATA.François _______________________________________________ Snort-users mailing list Snort-users () lists sourceforge net Go to this URL to change user options or unsubscribe: http://lists.sourceforge.net/lists/listinfo/snort-users Snort-users list archive: http://www.geocrawler.com/redir-sf.php3?list=snort-users
---------- Forwarded Message ---------- Subject: new spp_defrag.c Date: Thu, 28 Jun 2001 16:46:53 -0700 From: Dragos Ruiu <dr () kyx net> defragger with memory hard-hard limits and out of memory alert thresholding so nobody gets any snotty ideas about sticking in defrag noise. :-) Some tweaks that should help the sparc people... And a new higher efficiency timeout checker and garbage collector. Backwards compatible with snort 1.7 and 1.8 releases. just replace spp_defrag.c I sent an earlier version out to a few and didn't receive any tracebacks yet so I assume it's ok. Here is a slightly more aggresively defended version. Send me your complaints... or cpu utilization benchmarks and the %of fragmented traffic you have as I am trying to benchmark... cheers, --dr ------------------------------------------------------- -- Dragos Ruiu / kyx.net - we're from the future
Attachment:
spp_defrag.c
Description:
Current thread:
- Does ICMP detection work or what? Sheahan, Paul (PCLN-NW) (Jun 28)
- Re: Does ICMP detection work or what? Ryan Russell (Jun 28)
- Re: Does ICMP detection work or what? François Désarménien (Jun 29)
- Re: Does ICMP detection work or what? Dragos Ruiu (Jun 29)
- Re: Does ICMP detection work or what? François Désarménien (Jun 29)
- Re: Does ICMP detection work or what? Ryan Russell (Jun 28)