3571e53040
patches for easier mirroring, to eliminate a special copy, to make www.freebsd.org/security a full copy of security.freebsd.org and be eventually be the same. For now files are just sitting there. The symlinks are missing. Discussed on: www (repository location) Discussed with: simon (so)
139 lines
5.3 KiB
Text
139 lines
5.3 KiB
Text
-----BEGIN PGP SIGNED MESSAGE-----
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Hash: SHA1
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=============================================================================
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FreeBSD-SA-05:15.tcp Security Advisory
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The FreeBSD Project
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Topic: TCP connection stall denial of service
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Category: core
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Module: inet
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Announced: 2005-06-29
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Credits: Noritoshi Demizu
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Affects: All FreeBSD releases.
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Corrected: 2005-06-29 21:38:48 UTC (RELENG_5, 5.4-STABLE)
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2005-06-29 21:41:03 UTC (RELENG_5_4, 5.4-RELEASE-p3)
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2005-06-29 21:42:33 UTC (RELENG_5_3, 5.3-RELEASE-p17)
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2005-06-29 21:43:42 UTC (RELENG_4, 4.11-STABLE)
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2005-06-29 21:45:14 UTC (RELENG_4_11, 4.11-RELEASE-p11)
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2005-06-29 21:46:15 UTC (RELENG_4_10, 4.10-RELEASE-p16)
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CVE Name: CAN-2005-0356, CAN-2005-2068
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For general information regarding FreeBSD Security Advisories,
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including descriptions of the fields above, security branches, and the
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following sections, please visit
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<URL:http://www.freebsd.org/security/>.
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I. Background
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The Transmission Control Protocol (TCP) of the TCP/IP protocol suite
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provides a connection-oriented, reliable, sequence-preserving data
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stream service. TCP timestamps are used to measure Round-Trip Time
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and in the Protect Against Wrapped Sequences (PAWS) algorithm. TCP
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packets with the SYN flag set are used during setup of new TCP
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connections.
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II. Problem Description
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Two problems have been discovered in the FreeBSD TCP stack.
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First, when a TCP packets containing a timestamp is received, inadequate
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checking of sequence numbers is performed, allowing an attacker to
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artificially increase the internal "recent" timestamp for a connection.
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Second, a TCP packet with the SYN flag set is accepted for established
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connections, allowing an attacker to overwrite certain TCP options.
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III. Impact
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Using either of the two problems an attacker with knowledge of the
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local and remote IP and port numbers associated with a connection
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can cause a denial of service situation by stalling the TCP connection.
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The stalled TCP connection my be closed after some time by the other
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host.
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IV. Workaround
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In some cases it may be possible to defend against these attacks by
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blocking the attack packets using a firewall. Packets used to effect
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either of these attacks would have spoofed source IP addresses.
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V. Solution
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Perform one of the following:
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1) Upgrade your vulnerable system to 4-STABLE or 5-STABLE, or to the
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RELENG_5_4, RELENG_5_3, RELENG_4_11, or RELENG_4_10 security branch
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dated after the correction date.
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2) To patch your present system:
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The following patches have been verified to apply to FreeBSD 4.10,
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4.11, 5.3, and 5.4 systems.
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a) Download the relevant patch from the location below, and verify the
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detached PGP signature using your PGP utility.
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[FreeBSD 4.x]
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# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-05:15/tcp4.patch
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# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-05:15/tcp4.patch.asc
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[FreeBSD 5.x]
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# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-05:15/tcp.patch
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# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-05:15/tcp.patch.asc
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b) Apply the patch.
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# cd /usr/src
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# patch < /path/to/patch
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c) Recompile your kernel as described in
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<URL:http://www.freebsd.org/handbook/kernelconfig.html> and reboot the
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system.
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VI. Correction details
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The following list contains the revision numbers of each file that was
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corrected in FreeBSD.
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Branch Revision
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Path
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- -------------------------------------------------------------------------
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RELENG_4
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src/sys/netinet/tcp_input.c 1.107.2.44
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RELENG_4_11
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src/UPDATING 1.73.2.91.2.12
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src/sys/conf/newvers.sh 1.44.2.39.2.15
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src/sys/netinet/tcp_input.c 1.107.2.41.4.3
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RELENG_4_10
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src/UPDATING 1.73.2.90.2.17
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src/sys/conf/newvers.sh 1.44.2.34.2.18
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src/sys/netinet/tcp_input.c 1.107.2.41.2.1
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RELENG_5
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src/sys/netinet/tcp_input.c 1.252.2.16
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RELENG_5_4
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src/UPDATING 1.342.2.24.2.12
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src/sys/conf/newvers.sh 1.62.2.18.2.8
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src/sys/netinet/tcp_input.c 1.252.2.14.2.1
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RELENG_5_3
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src/UPDATING 1.342.2.13.2.20
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src/sys/conf/newvers.sh 1.62.2.15.2.22
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src/sys/netinet/tcp_input.c 1.252.4.1
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- -------------------------------------------------------------------------
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VII. References
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http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2005-0356
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http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2005-2068
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http://www.kb.cert.org/vuls/id/637934
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The latest revision of this advisory is available at
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ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-05:15.tcp.asc
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