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Date: Mon, 27 Nov 2000 00:48:49 -0500 (EST)
From: PEEETER <pjp@november.jaded.net>
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Subject: kern/23123: Turn off IP Options in IPSTEALTH mode
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>Number:         23123
>Category:       kern
>Synopsis:       IP options reveal IPstealth mode.  Just turn them off.
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sun Nov 26 21:50:00 PST 2000
>Closed-Date:
>Last-Modified:
>Originator:     PEEETER
>Release:        FreeBSD 3.5-RELEASE i386
>Organization:
Daemonium & Group of Nine
>Environment:

	patch untested for 5.0-current.

>Description:

	Most IP options allow a hop to be recorded.  This defies IPSTEALTH 
	mode which purpose it seems to hide from someone traceing.  In 
	simple form ping -R in the vicinity of 10 hops will find a 
	IPSTEALTH'ed router.  All other options also apply where a neat one 
	would be a brute force searching of IP in the timestamp pre-specified 
	ip option.  My attached fix will just avoid processing IP options.  

	I have not tested this at all but theoretically it should do what
	I don't want it to do (ermm ;)

>How-To-Repeat:

	ping -R host #reveals IPSTEALTH'ed router in route path.

>Fix:
	
Index: ip_input.c
===================================================================
RCS file: /usr/local/freebsd_repo/src/sys/netinet/ip_input.c,v
retrieving revision 1.149
diff -u -r1.149 ip_input.c
--- ip_input.c	2000/11/25 07:35:33	1.149
+++ ip_input.c	2000/11/27 05:37:52
@@ -457,6 +457,12 @@
 	 * to be sent and the original packet to be freed).
 	 */
 	ip_nhops = 0;		/* for source routed packets */
+
+#ifdef IPSTEALTH
+	/* IP Options reveal us so we don't process them in stealth mode */
+
+	if (! ipstealth)
+#endif
 	if (hlen > sizeof (struct ip) && ip_dooptions(m)) {
 #ifdef IPFIREWALL_FORWARD
 		ip_fw_fwd_addr = NULL;

>Release-Note:
>Audit-Trail:
>Unformatted:


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