From owner-freebsd-announce Wed Jun 10 11:35:09 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id LAA09570 for freebsd-announce-outgoing; Wed, 10 Jun 1998 11:35:09 -0700 (PDT) (envelope-from owner-freebsd-announce@FreeBSD.ORG) Received: from gvr.gvr.org (guido@gvr.gvr.org [194.151.74.97]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id LAA09374; Wed, 10 Jun 1998 11:34:27 -0700 (PDT) (envelope-from security-officer@freebsd.org) Received: (from guido@localhost) by gvr.gvr.org (8.8.8/8.8.5) id UAA25954; Wed, 10 Jun 1998 20:34:21 +0200 (MET DST) Date: Wed, 10 Jun 1998 20:34:21 +0200 (MET DST) Message-Id: <199806101834.UAA25954@gvr.gvr.org> From: FreeBSD Security Officer Subject: FreeBSD Security Advisory: FreeBSD-SA-98:06.icmp To: undisclosed-recipients:; Sender: owner-freebsd-announce@FreeBSD.ORG Precedence: bulk Reply-To: postmaster@FreeBSD.ORG X-Loop: FreeBSD.org -----BEGIN PGP SIGNED MESSAGE----- ============================================================================= FreeBSD-SA-98:06 Security Advisory FreeBSD, Inc. Topic: smurf attack Category: core Module: kernel Announced: 1998-06-10 Affects: FreeBSD 2.2.*, FreeBSD-stable and FreeBSD-current before 1998/05/26 suffer from this problem. Corrected: FreeBSD-current as of 1998/05/26 FreeBSD-stable as of 1998/05/26 FreeBSD only: yes Patches: ftp://ftp.freebsd.org/pub/FreeBSD/CERT/patches/SA-98:06/ ============================================================================= IMPORTANT MESSAGE: The FreeBSD security officer now uses the policy ftp://ftp.freebsd.org/pub/FreeBSD/POLICY.asc for sending out advisories. ============================================================================= I. Background As can be read in CERT advisory CA-98.01.smurf, there exists a denial of service attack called "smurfing". This attack sends ICMP echo requests to the broadcast address of a network. This results in the source address of the ICMP packets being flooded with ICMP echo replies. Of course, the source address is spoofed. II. Problem Description A solution at the intermediate network being abused to generate the ICMP echo replies is to either block ICMP echo requests directed to a broadcast address or to configure the hosts on that network not to respond to such an ICMP request. In the CERT advisory, the following was reported: In FreeBSD 2.2.5 and up, the tcp/ip stack does not respond to ICMP echo requests destined for broadcast and multicast addresses by default. This behavior can be changed via the sysctl command via mib net.inet.icmp.bmcastecho. Unfortunately, an error was made with the implementation of this functionality and, despite the text in the CERT advisory, the net.inet.icmp.bmcastecho sysctl variable default is to respond to ICMP packets sent to the networks broadcast address. You should explicitly run the command sysctl -w net.inet.icmp.bmcastecho=0 to disable this. III. Impact Your network can suffer performance degradation when a large amount of spoofed ICMP is sent to your broadcast address. IV. Workaround Block ICMP echo requests to broadcast addresses in your kernel using ipfw(8). See CERT advisory CA-98.01.smurf for more workarounds. V. Solution Apply the following patch: Patch for 3.0-current, 2.2-stable, 2.2.5 and 2.2.6 systems: Index: ip_icmp.c =================================================================== RCS file: /home/cvsup/freebsd/CVS/src/sys/netinet/ip_icmp.c,v retrieving revision 1.29 retrieving revision 1.30 diff -u -r1.29 -r1.30 --- ip_icmp.c 1997/08/25 16:29:27 1.29 +++ ip_icmp.c 1998/05/26 11:34:30 1.30 @@ -375,8 +375,7 @@ case ICMP_ECHO: if (!icmpbmcastecho - && (m->m_flags & (M_MCAST | M_BCAST)) != 0 - && IN_MULTICAST(ntohl(ip->ip_dst.s_addr))) { + && (m->m_flags & (M_MCAST | M_BCAST)) != 0) { icmpstat.icps_bmcastecho++; break; } @@ -385,8 +384,7 @@ case ICMP_TSTAMP: if (!icmpbmcastecho - && (m->m_flags & (M_MCAST | M_BCAST)) != 0 - && IN_MULTICAST(ntohl(ip->ip_dst.s_addr))) { + && (m->m_flags & (M_MCAST | M_BCAST)) != 0) { icmpstat.icps_bmcasttstamp++; break; } ============================================================================= FreeBSD, Inc. Web Site: http://www.freebsd.org/ Confidential contacts: security-officer@freebsd.org Security notifications: security-notifications@freebsd.org Security public discussion: freebsd-security@freebsd.org PGP Key: ftp://ftp.freebsd.org/pub/FreeBSD/CERT/public_key.asc Notice: Any patches in this document may not apply cleanly due to modifications caused by digital signature or mailer software. Please reference the URL listed at the top of this document for original copies of all patches if necessary. ============================================================================= -----BEGIN PGP SIGNATURE----- Version: 2.6.3ia Charset: noconv iQCVAwUBNX7QUlUuHi5z0oilAQEBMQP6Avlv1dEMtH7thC510f17to9UNcDAobz4 83Fd5qVfwjBy5G0AxSLOLYb4/9ZI137aNtsLRcvx3J4CRGPBCpA7UXptID/QuTHO 6Z0sqix21OAigcrdX0Aegx2JBvY+NLgBSK4NrWbpp5sAjjW1i4OS/wzGQmhXFDjU JGoIZMmYKXU= =VFXs -----END PGP SIGNATURE----- This is the moderated mailing list freebsd-announce. The list contains announcements of new FreeBSD capabilities, important events and project milestones. See also the FreeBSD Web pages at http://www.freebsd.org To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-announce" in the body of the message From owner-freebsd-announce Fri Jun 12 13:30:34 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id NAA07527 for freebsd-announce-outgoing; Fri, 12 Jun 1998 13:30:34 -0700 (PDT) (envelope-from owner-freebsd-announce@FreeBSD.ORG) Received: (from jmb@localhost) by hub.freebsd.org (8.8.8/8.8.8) id NAA07522 for freebsd-announce; Fri, 12 Jun 1998 13:30:30 -0700 (PDT) (envelope-from jmb) Date: Fri, 12 Jun 1998 13:30:30 -0700 (PDT) From: "Jonathan M. Bresler" Message-Id: <199806122030.NAA07522@hub.freebsd.org> To: freebsd-announce Sender: owner-freebsd-announce@FreeBSD.ORG Precedence: bulk Reply-To: postmaster@FreeBSD.ORG X-Loop: FreeBSD.org To: FreeBSD-announce@FreeBSD.org Subject: FreeBSD Really-Quick(TM) NewsLetter: Volume #1 Issue #1 FreeBSD Really-Quick(TM) NewsLetter. Things Happening in FreeBSD. Volume #1 Issue #1 June 1998 General News: Jordan Hubbard, Poul-Henning Kamp, Justin Gibbs, Jonathan Bresler, David Greenman and other members of the Core Team will be at the USENIX technical conference. Be Sure to Attend! Information at: http://www.usenix.org June 15-19, New Orleans, Louisiana Download the Published FreeBSD News Letter Volume #2: ftp://ftp.freebsd.org/pub/FreeBSD/newsletter/issue2.pdf Web Masters: Check out this article on balancing Webserver traffic: www.WebTechniques.com/features/1998/05/engelschall/engelschall.shtml Filesystem Management: An early version of vinum, a FreeBSD volume manager, is available. It allows volumes to span disks and spread diskload across multiple disks. Check out: http://www.lemis.com/vinum.html. Alpha Porting Project: There seems to be quite a bit of recent activity on this project. Developers are being actively sought. Join the alpha@freebsd.org mailing list. PALCode and other Alpha Documentation can be found at: ftp.digital.com/pub/Digital/info/semiconductor/literature/dsc-library.html X Window System: Check out the Enlightenment Desktop: /usr/ports/x11/enlightenment Check out the Themes you can download for Enlightenment: http://www.rasterman.com/themes/printthemes.cgi Graphics/Design: Check out the 'Blender' package from Neo-Geo ftp://ftp.freebsd.org/pub/FreeBSD/2.2.6-RELEASE/commerce/3D/Blender/ System Administration: A Web Based FreeBSD System Administration Tool is available. http://ourworld.compuserve.com/homepages/berend/FreEasy.html A X based FreeBSD System Administration Tool is also available. http://cam.grad.kiev.ua/~rssh/admin/admin.html Both are functional, yet still in developmental stages. Installing FreeBSD: Here is a newbie-oriented Install tutorial complete with screen shots. Check out: http://www.vmunix.com/fbsd-book/install.phtml This is a monthly Newsletter, published only by E-mail. If you have anything you would like to see in the next edition, please send e-mail to fbsd-book@vmunix.com -Chris Coleman This is the moderated mailing list freebsd-announce. The list contains announcements of new FreeBSD capabilities, important events and project milestones. See also the FreeBSD Web pages at http://www.freebsd.org To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-announce" in the body of the message