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Subject: Caldera Security Advisory SA-1997.33: Vulnerabilities in inetd

Original report date:	21-Jun-1997 ("ping pong" vulnerability)
Original report date:	26-Aug-1997 (inetd denial of service vulnerability)
RPM build date:		03-Nov-1997
Advisory issue date:	18-Dec-1997

Topic: Vulnerabilities in "inetd" in netkit-base-0.10-1


I. Problem Description

	NOTE: Two different vulnerabilities are addressed in this advisory
	and corresponding update to the "inetd" daemon included in the
	netkit-base RPM.

	First issue: Sending a UDP datagram to the echo service with
	fake IP sender address and a source port of, for example,
	"echo" would cause the two hosts to ping-pong echo packets hence
	and forth.  Doing this repeatedly would create a packet storm.
	Other builtin UDP services may be similarly vulnerable.

	This can be fixed by making inetd ignore all UDP with source
	port less than 512.

	Second issue: When inetd receives more than 40 connects per
	minute to any given service, it would shut down that service
	for 10 minutes. Inetd logs this condition to syslogd saying
	`Service xxx looping, terminated'.

	There's no easy fix for that (the experts are still working on
	that). If you experience this problem, you are either under
	attack, or (more likely) you are experiencing a load peak
	from legitimate usage.	In the latter case, you can bump the
	max number of requests serviced per minute by modifying the
	inetd.conf description of the offending service:
	
	ftp stream tcp nowait.100 root /usr/sbin/tcpd in.ftpd -l
			     ^^^^ .max parameter
		
	This increases the threshold to 100 requests per minute.

	In case of an outside attack, you should make sure to firewall
	all services that are not to be used from outside.

	Another problem that was discovered in this context was that inetd
	wouldn't serve more that one request per second on average. This
	release also fixes this bug.


II. Impact

	Any machine with netkit-base-0.10-1 or earlier versions
	of NetKit-B may be vulnerable.  Run 'rpm -q netkit-base'
	to determine which version you have installed.


III. Solution

        Replace netkit-base-0.10-1 with the netkit-base-0.10-2.  The
	source and binary RPMs can be found on Caldera's ftp site at:

        ftp://ftp.caldera.com/pub/openlinux/updates/1.1/current/RPMS/

                and

        ftp://ftp.caldera.com/pub/openlinux/updates/1.1/current/SRPMS/

        The MD5 checksum (from the "md5sum" command) for this package is:

	453f0e790cccb9af8c18ed9bccf9f4e0  RPMS/netkit-base-0.10-2.i386.rpm
	3ee21bbe8d17d57cb4eb638bd12c4b38  SRPMS/netkit-base-0.10-2.src.rpm

	Install the new package by executing:

		rpm -U netkit-base-0.10-2.i386.rpm

	You will then need to restart inetd.  Do this by executing:

		/etc/rc.d/init.d/inet stop

	followed by:

		/etc/rc.d/init.d/inet start

	Note: this upgrade should be done from the console when no one
	else is logged in on the system.

	If you are still using a NetKit-B package, you should first
	upgrade to the netkit-*-0.10* packages.  See Caldera's security
	advisory:

		"SA-1997.19 - September 22, 1997 Vulnerabilities in NetKit-B"

	for information concerning this issue.


IV. References / Credits

	From:		"D. Richard Hipp" <drh@tobit.hwaci.vnet.net>
	To:		support@caldera.com
	Date:		Tue, 26 Aug 1997 14:51:54 -0400
	Subject:	Denial-of-service attack against INETD.
	Message-Id:	<199708261851.OAA04649@tobit.hwaci.vnet.net>

	Some inetd fixes: Olaf Kirch <okir@caldera.de>

	From:		Willy TARREAU <tarreau@AEMIAIF.IBP.FR>
	To:		BUGTRAQ@NETSPACE.ORG
	Date:		Sat, 21 Jun 1997 23:58:16 +0200
	Subject:	Simple TCP service can hang a system
	Message-ID:	<199706212158.XAA01904@aemiaif.ibp.fr>

	This and other Caldera security resources are located at:

		http://www.caldera.com/tech-ref/security/

	This security alert closes Caldera's internal problem reports #936
	and #978.


V. PGP Signature

	This message was signed with the PGP key for <security@caldera.com>.

	This key can be obtained from:
		ftp://ftp.caldera.com/pub/pgp-keys/

	Or on an OpenLinux CDROM under:
		/OpenLinux/pgp-keys/

	$Id: SA-1997.32,v 1.2 1997/12/18 22:49:42 ron Exp $

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