Date: Tue, 16 Sep 2014 15:48:35 +0300 From: Andriy Gapon <avg@FreeBSD.org> To: freebsd-security@FreeBSD.org Subject: Re: [FreeBSD-Announce] FreeBSD Security Advisory FreeBSD-SA-14:19.tcp Message-ID: <541831A3.7010700@FreeBSD.org> In-Reply-To: <201409161014.s8GAE7jY070664@freefall.freebsd.org> References: <201409161014.s8GAE7jY070664@freefall.freebsd.org>
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On 16/09/2014 13:14, FreeBSD Security Advisories wrote: > ============================================================================= > FreeBSD-SA-14:19.tcp Security Advisory > The FreeBSD Project > > Topic: Denial of Service in TCP packet processing > > Category: core > Module: inet > Announced: 2014-09-16 > Credits: Jonathan Looney (Juniper SIRT) > Affects: All supported versions of FreeBSD. Does the issue affect head aka CURRENT as well? > Corrected: 2014-09-16 09:48:35UTC (stable/10, 10.1-PRERELEASE) > 2014-09-16 09:48:35 UTC (stable/10, 10.1-BETA1-p1) > 2014-09-16 09:50:19 UTC (releng/10.0, 10.0-RELEASE-p9) > 2014-09-16 09:49:11 UTC (stable/9, 9.3-STABLE) > 2014-09-16 09:50:19 UTC (releng/9.3, 9.3-RELEASE-p2) > 2014-09-16 09:50:19 UTC (releng/9.2, 9.2-RELEASE-p12) > 2014-09-16 09:50:19 UTC (releng/9.1, 9.1-RELEASE-p19) > 2014-09-16 09:49:11 UTC (stable/8, 8.4-STABLE) > 2014-09-16 09:50:19 UTC (releng/8.4, 8.4-RELEASE-p16) > CVE Name: CVE-2004-0230 > > For general information regarding FreeBSD Security Advisories, > including descriptions of the fields above, security branches, and the > following sections, please visit <URL:http://security.FreeBSD.org/>. > > I. Background > > The Transmission Control Protocol (TCP) of the TCP/IP protocol suite > provides a connection-oriented, reliable, sequence-preserving data > stream service. New TCP connections are initiated using special SYN > flag in a datagram. Sequencing of data is controlled by 32-bit sequence > numbers, that start with a random value and are increased using modulo > 2**32 arithmetic. TCP endpoints maintain a window of expected, and > thus allowed, sequence numbers for a connection. > > II. Problem Description > > When a segment with the SYN flag for an already existing connection arrives, > the TCP stack tears down the connection, bypassing a check that the > sequence number in the segment is in the expected window. > > III. Impact > > An attacker who has the ability to spoof IP traffic can tear down a > TCP connection by sending only 2 packets, if they know both TCP port > numbers. In case one of the two port numbers is unknown, a successful > attack requires less than 2**17 packets spoofed, which can be > generated within less than a second on a decent connection to the > Internet. > > IV. Workaround > > It is possible to defend against these attacks with stateful traffic > inspection using a firewall. This can be done by enabling pf(4) on > the system and creating states for every connection. Even a default > ruleset to allow all traffic would be sufficient to mitigate this > issue. > > V. Solution > > Perform one of the following: > > 1) Upgrade your vulnerable system to a supported FreeBSD stable or > release / security branch (releng) dated after the correction date. > > 2) To update your vulnerable system via a source code patch: > > The following patches have been verified to apply to the applicable > FreeBSD release branches. > > a) Download the relevant patch from the location below, and verify the > detached PGP signature using your PGP utility. > > # fetch http://security.FreeBSD.org/patches/SA-14:19/tcp.patch > # fetch http://security.FreeBSD.org/patches/SA-14:19/tcp.patch.asc > # gpg --verify tcp.patch.asc > > b) Apply the patch. Execute the following commands as root: > > # cd /usr/src > # patch < /path/to/patch > > c) Recompile your kernel as described in > <URL:http://www.FreeBSD.org/handbook/kernelconfig.html>; and reboot the > system. > > 3) To update your vulnerable system via a binary patch: > > Systems running a RELEASE version of FreeBSD on the i386 or amd64 > platforms can be updated via the freebsd-update(8) utility: > > # freebsd-update fetch > # freebsd-update install > > VI. Correction details > > The following list contains the correction revision numbers for each > affected branch. > > Branch/path Revision > ------------------------------------------------------------------------- > stable/8/ r271668 > releng/8.4/ r271669 > stable/9/ r271668 > releng/9.1/ r271669 > releng/9.2/ r271669 > releng/9.3/ r271669 > stable/10/ r271667 > releng/10.0/ r271669 > ------------------------------------------------------------------------- > > To see which files were modified by a particular revision, run the > following command, replacing NNNNNN with the revision number, on a > machine with Subversion installed: > > # svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base > > Or visit the following URL, replacing NNNNNN with the revision number: > > <URL:http://svnweb.freebsd.org/base?view=revision&revision=NNNNNN>; > > VII. References > > <URL:http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2004-0230>; > > The latest revision of this advisory is available at > <URL:http://security.FreeBSD.org/advisories/FreeBSD-SA-14:19.tcp.asc>; > _______________________________________________ > freebsd-announce@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-announce > To unsubscribe, send any mail to "freebsd-announce-unsubscribe@freebsd.org" > -- Andriy Gapon
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