138 lines
5.3 KiB
Text
138 lines
5.3 KiB
Text
-----BEGIN PGP SIGNED MESSAGE-----
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Hash: SHA512
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=============================================================================
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FreeBSD-SA-19:22.mbuf Security Advisory
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The FreeBSD Project
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Topic: IPv6 remote Denial-of-Service
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Category: kernel
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Module: net
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Announced: 2019-08-20
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Credits: Clement Lecigne
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Affects: All supported versions of FreeBSD.
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Corrected: 2019-08-10 00:01:25 UTC (stable/12, 12.0-STABLE)
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2019-08-20 17:49:33 UTC (releng/12.0, 12.0-RELEASE-p10)
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2019-08-10 00:02:45 UTC (stable/11, 11.3-STABLE)
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2019-08-20 17:49:33 UTC (releng/11.3, 11.3-RELEASE-p3)
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2019-08-20 17:49:33 UTC (releng/11.2, 11.2-RELEASE-p14)
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CVE Name: CVE-2019-5611
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For general information regarding FreeBSD Security Advisories, including
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descriptions of the fields above, security branches, and the following
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sections, please visit <URL:https://security.FreeBSD.org/>.
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I. Background
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mbufs are a unit of memory management mostly used in the kernel for network
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packets and socket buffers. m_pulldown(9) is a function to arrange the data
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in a chain of mbufs.
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II. Problem Description
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Due do a missing check in the code of m_pulldown(9) data returned may not be
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contiguous as requested by the caller.
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III. Impact
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Extra checks in the IPv6 code catch the error condition and trigger a kernel
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panic leading to a remote DoS (denial-of-service) attack with certain
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Ethernet interfaces. At this point it is unknown if any other than the IPv6
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code paths can trigger a similar condition.
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IV. Workaround
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For the currently known attack vector systems with IPv6 not enabled are not
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vulnerable.
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On systems with IPv6 active, IPv6 fragmentation may be disabled, or
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a firewall can be used to filter out packets with certain or excessive
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amounts of extension headers in a first fragment. These rules may be
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dependent on the operational needs of each site.
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V. Solution
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Upgrade your vulnerable system to a supported FreeBSD stable or
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release / security branch (releng) dated after the correction date,
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and reboot.
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1) To update your vulnerable system via a binary patch:
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Systems running a RELEASE version of FreeBSD on the i386 or amd64
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platforms can be updated via the freebsd-update(8) utility:
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# freebsd-update fetch
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# freebsd-update install
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# shutdown -r +10min "Rebooting for security update"
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2) To update your vulnerable system via a source code patch:
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The following patches have been verified to apply to the applicable
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FreeBSD release branches.
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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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# fetch https://security.FreeBSD.org/patches/SA-19:22/mbuf.patch
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# fetch https://security.FreeBSD.org/patches/SA-19:22/mbuf.patch.asc
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# gpg --verify mbuf.patch.asc
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b) Apply the patch. Execute the following commands as root:
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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:https://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 correction revision numbers for each
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affected branch.
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Branch/path Revision
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- -------------------------------------------------------------------------
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stable/12/ r350828
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releng/12.0/ r351259
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stable/11/ r350829
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releng/11.3/ r351259
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releng/11.2/ r351259
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- -------------------------------------------------------------------------
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To see which files were modified by a particular revision, run the
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following command, replacing NNNNNN with the revision number, on a
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machine with Subversion installed:
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# svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base
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Or visit the following URL, replacing NNNNNN with the revision number:
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<URL:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN>
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VII. References
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<URL:https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=238787>
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<URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-5611>
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The latest revision of this advisory is available at
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<URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-19:22.mbuf.asc>
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