• [FreeBSD-Announce] FreeBSD Security Advisory FreeBSD-SA-18:08.tcp

    From FreeBSD Security Advisories@21:1/5 to All on Mon Aug 6 21:00:00 2018
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    Hash: SHA512

    ============================================================================= FreeBSD-SA-18:08.tcp Security Advisory
    The FreeBSD Project

    Topic: Resource exhaustion in TCP reassembly

    Category: core
    Module: inet
    Announced: 2018-08-06
    Credits: Juha-Matti Tilli <juha-matti.tilli@iki.fi> from
    Aalto University, Department of Communications and Networking
    and Nokia Bell Labs
    Affects: All supported versions of FreeBSD.
    Corrected: 2018-08-06 18:46:09 UTC (stable/11, 11.1-STABLE)
    2018-08-06 17:47:47 UTC (releng/11.2, 11.2-RELEASE-p1)
    2018-08-06 17:48:46 UTC (releng/11.1, 11.1-RELEASE-p12)
    2018-08-06 18:47:03 UTC (stable/10, 10.4-STABLE)
    2018-08-06 17:50:40 UTC (releng/10.4, 10.4-RELEASE-p10)
    CVE Name: CVE-2018-6922

    For general information regarding FreeBSD Security Advisories,
    including descriptions of the fields above, security branches, and the following sections, please visit <URL:https://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.

    To transmit a stream of data, TCP breaks the data stream into segments
    for transmission through the Internet, and reassembles the segments at
    the receiving side to recreate the data stream.

    II. Problem Description

    One of the data structures that holds TCP segments uses an inefficient algorithm to reassemble the data. This causes the CPU time spent on
    segment processing to grow linearly with the number of segments in the reassembly queue.

    III. Impact

    An attacker who has the ability to send TCP traffic to a victim system
    can degrade the victim system's network performance and/or consume
    excessive CPU by exploiting the inefficiency of TCP reassembly
    handling, with relatively small bandwidth cost.

    IV. Workaround

    As a workaround, system administrators should configure their systems
    to only accept TCP connections from trusted end-stations, if it is
    possible to do so.

    For systems which must accept TCP connections from untrusted
    end-stations, the workaround is to limit the size of each reassembly
    queue. The capability to do that is added by the patches noted in the "Solution" section below.

    V. Solution

    As a temporary solution to this problem, these patches limit the size
    of each TCP connection's reassembly queue. The value is controlled by
    a sysctl (net.inet.tcp.reass.maxqueuelen), which sets the maximum
    number of TCP segments that can be outstanding on a session's
    reassembly queue. This value defaults to 100.

    Note that setting this value too low could impact the throughput of
    TCP connections which experience significant loss or
    reordering. However, the higher this number is set, the more resources
    can be consumed on TCP reassembly processing.

    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.

    Afterward, reboot the system.

    2) 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

    Afterward, reboot the system.

    3) 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.

    [FreeBSD 10.4]
    # fetch https://security.FreeBSD.org/patches/SA-18:08/tcp-10.patch
    # fetch https://security.FreeBSD.org/patches/SA-18:08/tcp-10.patch.asc
    # gpg --verify tcp-10.patch.asc

    [FreeBSD 11.x]
    # fetch https://security.FreeBSD.org/patches/SA-18:08/tcp-11.patch
    # fetch https://security.FreeBSD.org/patches/SA-18:08/tcp-11.patch.asc
    # gpg --verify tcp-11.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:https://www.FreeBSD.org/handbook/kernelconfig.html> and reboot the
    system.

    VI. Correction details

    The following list contains the correction revision numbers for each
    affected branch.

    Branch/path Revision
    - ------------------------------------------------------------------------- stable/10/ r337392 releng/10.4/ r337389 stable/11/ r337391 releng/11.1/ r337388 releng/11.2/ r337387
    - -------------------------------------------------------------------------

    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:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN>

    VII. References

    <URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-6922>

    <URL:https://www.kb.cert.org/vuls/id/962459>

    The latest revision of this advisory is available at <URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-18:08.tcp.asc> -----BEGIN PGP SIGNATURE-----
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  • From FreeBSD Security Advisories@21:1/5 to All on Wed Aug 15 07:00:00 2018
    -----BEGIN PGP SIGNED MESSAGE-----
    Hash: SHA512

    ============================================================================= FreeBSD-SA-18:08.tcp Security Advisory
    The FreeBSD Project

    Topic: Resource exhaustion in TCP reassembly

    Category: core
    Module: inet
    Announced: 2018-08-06
    Credits: Juha-Matti Tilli <juha-matti.tilli@iki.fi> from
    Aalto University, Department of Communications and Networking
    and Nokia Bell Labs
    Affects: All supported versions of FreeBSD.
    Corrected: 2018-08-06 18:46:09 UTC (stable/11, 11.1-STABLE)
    2018-08-15 02:30:11 UTC (releng/11.2, 11.2-RELEASE-p2)
    2018-08-15 02:30:11 UTC (releng/11.1, 11.1-RELEASE-p13)
    2018-08-06 18:47:03 UTC (stable/10, 10.4-STABLE)
    2018-08-15 02:31:10 UTC (releng/10.4, 10.4-RELEASE-p11)
    CVE Name: CVE-2018-6922

    For general information regarding FreeBSD Security Advisories,
    including descriptions of the fields above, security branches, and the following sections, please visit <URL:https://security.FreeBSD.org/>.


    0. Revision history

    v1.0 2018-08-06 Initial release.
    v1.1 2018-08-14 Fixed documentation date in manual pages.

    I. Background

    The Transmission Control Protocol (TCP) of the TCP/IP protocol suite
    provides a connection-oriented, reliable, sequence-preserving data
    stream service.

    To transmit a stream of data, TCP breaks the data stream into segments
    for transmission through the Internet, and reassembles the segments at
    the receiving side to recreate the data stream.

    II. Problem Description

    One of the data structures that holds TCP segments uses an inefficient algorithm to reassemble the data. This causes the CPU time spent on
    segment processing to grow linearly with the number of segments in the reassembly queue.

    III. Impact

    An attacker who has the ability to send TCP traffic to a victim system
    can degrade the victim system's network performance and/or consume
    excessive CPU by exploiting the inefficiency of TCP reassembly
    handling, with relatively small bandwidth cost.

    IV. Workaround

    As a workaround, system administrators should configure their systems
    to only accept TCP connections from trusted end-stations, if it is
    possible to do so.

    For systems which must accept TCP connections from untrusted
    end-stations, the workaround is to limit the size of each reassembly
    queue. The capability to do that is added by the patches noted in the "Solution" section below.

    V. Solution

    As a temporary solution to this problem, these patches limit the size
    of each TCP connection's reassembly queue. The value is controlled by
    a sysctl (net.inet.tcp.reass.maxqueuelen), which sets the maximum
    number of TCP segments that can be outstanding on a session's
    reassembly queue. This value defaults to 100.

    Note that setting this value too low could impact the throughput of
    TCP connections which experience significant loss or
    reordering. However, the higher this number is set, the more resources
    can be consumed on TCP reassembly processing.

    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.

    Afterward, reboot the system.

    2) 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

    Afterward, reboot the system.

    3) 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.

    [FreeBSD 10.4]
    # fetch https://security.FreeBSD.org/patches/SA-18:08/tcp-10.patch
    # fetch https://security.FreeBSD.org/patches/SA-18:08/tcp-10.patch.asc
    # gpg --verify tcp-10.patch.asc

    [FreeBSD 11.x]
    # fetch https://security.FreeBSD.org/patches/SA-18:08/tcp-11.patch
    # fetch https://security.FreeBSD.org/patches/SA-18:08/tcp-11.patch.asc
    # gpg --verify tcp-11.patch.asc

    [*** v1.1 NOTE ***] Patchsets are provided for completeness, it have
    little impact to runtime behavior.

    [FreeBSD 10.4]
    # fetch https://security.FreeBSD.org/patches/SA-18:08/tcp-man-10.patch
    # fetch https://security.FreeBSD.org/patches/SA-18:08/tcp-man-10.patch.asc
    # gpg --verify tcp-man-10.patch.asc

    [FreeBSD 11.x]
    # fetch https://security.FreeBSD.org/patches/SA-18:08/tcp-man-11.patch
    # fetch https://security.FreeBSD.org/patches/SA-18:08/tcp-man-11.patch.asc
    # gpg --verify tcp-man-11.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:https://www.FreeBSD.org/handbook/kernelconfig.html> and reboot the
    system.

    VI. Correction details

    The following list contains the correction revision numbers for each
    affected branch.

    Branch/path Revision
    - ------------------------------------------------------------------------- stable/10/ r337392 releng/10.4/ r337832 stable/11/ r337391 releng/11.1/ r337828 releng/11.2/ r337828
    - -------------------------------------------------------------------------

    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:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN>

    VII. References

    <URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-6922>

    <URL:https://www.kb.cert.org/vuls/id/962459>

    The latest revision of this advisory is available at <URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-18:08.tcp.asc> -----BEGIN PGP SIGNATURE-----
    Version: GnuPG v2.2.9 (FreeBSD)

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    _______________________________________________
    freebsd-announce@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-announce
    To unsubscribe, send any mail to "freebsd-announce-unsubscribe@freebsd.org"

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