172 lines
6.8 KiB
Text
172 lines
6.8 KiB
Text
-----BEGIN PGP SIGNED MESSAGE-----
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Hash: SHA512
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=============================================================================
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FreeBSD-SA-16:24.ntp Security Advisory
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The FreeBSD Project
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Topic: Multiple vulnerabilities of ntp
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Category: contrib
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Module: ntp
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Announced: 2016-06-04
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Credits: Network Time Foundation and various contributors listed below
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Affects: All supported versions of FreeBSD.
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Corrected: 2016-06-03 08:59:21 UTC (stable/10, 10.3-STABLE)
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2016-06-04 05:46:52 UTC (releng/10.3, 10.3-RELEASE-p5)
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2016-06-04 05:46:52 UTC (releng/10.2, 10.2-RELEASE-p19)
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2016-06-04 05:46:52 UTC (releng/10.1, 10.1-RELEASE-p36)
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2016-06-03 09:03:10 UTC (stable/9, 9.3-STABLE)
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2016-06-04 05:46:52 UTC (releng/9.3, 9.3-RELEASE-p44)
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CVE Name: CVE-2016-4957, CVE-2016-4953, CVE-2016-4954, CVE-2016-4955
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CVE-2016-4956
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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 <URL:https://security.FreeBSD.org/>.
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I. Background
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The ntpd(8) daemon is an implementation of the Network Time Protocol (NTP)
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used to synchronize the time of a computer system to a reference time
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source.
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II. Problem Description
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Multiple vulnerabilities have been discovered in the NTP suite:
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The fix for Sec 3007 in ntp-4.2.8p7 contained a bug that could cause ntpd to
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crash. [CVE-2016-4957, Reported by Nicolas Edet of Cisco]
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An attacker who knows the origin timestamp and can send a spoofed packet
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containing a CRYPTO-NAK to an ephemeral peer target before any other
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response is sent can demobilize that association. [CVE-2016-4953, Reported by
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Miroslav Lichvar of Red Hat]
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An attacker who is able to spoof packets with correct origin timestamps
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from enough servers before the expected response packets arrive at the
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target machine can affect some peer variables and, for example,
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cause a false leap indication to be set. [CVE-2016-4954, Reported by
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Jakub Prokes of Red Hat]
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An attacker who is able to spoof a packet with a correct origin timestamp
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before the expected response packet arrives at the target machine can
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send a CRYPTO_NAK or a bad MAC and cause the association's peer variables
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to be cleared. If this can be done often enough, it will prevent that
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association from working. [CVE-2016-4955, Reported by Miroslav Lichvar
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of Red Hat]
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The fix for NtpBug2978 does not cover broadcast associations, so broadcast
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clients can be triggered to flip into interleave mode. [CVE-2016-4956,
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Reported by Miroslav Lichvar of Red Hat.]
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III. Impact
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Malicious remote attackers may be able to break time synchronization,
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or cause the ntpd(8) daemon to crash.
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IV. Workaround
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No workaround is available, but systems not running ntpd(8) are not
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affected. Network administrators are advised to implement BCP-38,
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which helps to reduce the risk associated with the attacks.
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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 a supported FreeBSD stable or
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release / security branch (releng) dated after the correction date.
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The ntpd service has to be restarted after the update. A reboot is
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recommended but not required.
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2) 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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The ntpd service has to be restarted after the update. A reboot is
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recommended but not required.
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3) 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-16:24/ntp.patch
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# fetch https://security.FreeBSD.org/patches/SA-16:24/ntp.patch.asc
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# gpg --verify ntp.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 the operating system using buildworld and installworld as
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described in <URL:https://www.FreeBSD.org/handbook/makeworld.html>.
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Restart the applicable daemons, or reboot the 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/9/ r301257
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releng/9.3/ r301301
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stable/10/ r301256
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releng/10.1/ r301301
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releng/10.2/ r301301
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releng/10.3/ r301301
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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://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-4957>
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<URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-4953>
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<URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-4954>
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<URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-4955>
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<URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-4956>
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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-16:24.ntp.asc>
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