FreeBSD Security Advisory FreeBSD-SA-16:02.ntp

Fabricante: FreeBSD
Fecha: 14/01/2016
Identificador: FreeBSD-SA-16:02.ntp
FreeBSD Security Advisory FreeBSD-SA-16:02.ntp
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 ============================================================================= FreeBSD-SA-16:02.ntp Security Advisory The FreeBSD Project Topic: ntp panic threshold bypass vulnerability Category: contrib Module: ntp Announced: 2016-01-14 Credits: Network Time Foundation Affects: All supported versions of FreeBSD. Corrected: 2016-01-11 01:09:50 UTC (stable/10, 10.2-STABLE) 2016-01-14 09:10:46 UTC (releng/10.2, 10.2-RELEASE-p9) 2016-01-14 09:11:16 UTC (releng/10.1, 10.1-RELEASE-p26) 2016-01-11 01:48:16 UTC (stable/9, 9.3-STABLE) 2016-01-14 09:11:26 UTC (releng/9.3, 9.3-RELEASE-p33) CVE Name: CVE-2015-5300 For general information regarding FreeBSD Security Advisories, including descriptions of the fields above, security branches, and the following sections, please visit . I. Background The ntpd(8) daemon is an implementation of the Network Time Protocol (NTP) used to synchronize the time of a computer system to a reference time source. II. Problem Description The ntpd(8) daemon has a safety feature to prevent excessive stepping of the clock called the "panic threshold". If ever ntpd(8) determines the system clock is incorrect by more than this threshold, the daemon exits. There is an implementation error within the ntpd(8) implementation of this feature, which allows the system time be adjusted in certain circumstances. III. Impact When ntpd(8) is started with the '-g' option specified, the system time will be corrected regardless of if the time offset exceeds the panic threshold (by default, 1000 seconds). The FreeBSD rc(8) subsystem allows specifying the '-g' option by either including '-g' in the ntpd_flags list or by enabling ntpd_sync_on_start in the system rc.conf(5) file. If at the moment ntpd(8) is restarted, an attacker can immediately respond to enough requests from enough sources trusted by the target, which is difficult and not common, there is a window of opportunity where the attacker can cause ntpd(8) to set the time to an arbitrary value. IV. Workaround No workaround is available, but systems not running ntpd(8), or running ntpd(8) but do not use ntpd_sync_on_start="YES" or specify the '-g' option in ntpd_flags are not affected. Neither of these are set by default. 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. The ntpd service has to be restarted after the update. A reboot is recommended but not required. 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 The ntpd service has to be restarted after the update. A reboot is recommended but not required. 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 10.1 and 10.2] # fetch https://security.FreeBSD.org/patches/SA-16:02/ntp-10.patch # fetch https://security.FreeBSD.org/patches/SA-16:02/ntp-10.patch.asc # gpg --verify ntp-10.patch.asc [FreeBSD 9.3] # fetch https://security.FreeBSD.org/patches/SA-16:02/ntp-9.patch # fetch https://security.FreeBSD.org/patches/SA-16:02/ntp-9.patch.asc # gpg --verify ntp-9.patch.asc b) Apply the patch. Execute the following commands as root: # cd /usr/src # patch < /path/to/patch c) Recompile the operating system using buildworld and installworld as described in . Restart the applicable daemons, or reboot the system. VI. Correction details The following list contains the correction revision numbers for each affected branch. Branch/path Revision - ------------------------------------------------------------------------- stable/9/ r293652 releng/9.3/ r293896 stable/10/ r293650 releng/10.1/ r293894 releng/10.2/ r293893 - ------------------------------------------------------------------------- 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: VII. References The latest revision of this advisory is available at -----BEGIN PGP SIGNATURE----- iQIcBAEBCgAGBQJWl2j2AAoJEO1n7NZdz2rnyg4QAJ/x3xs+pNGXxTT63hbBqLcB NTSljW5+hFpL94Nr+rHrelvcT3HkvdWUC+7BvMksoUYCZv0vClp5W7tsfuojDPr0 GechK1BpLwxeLnRexulWEuvDQpbr6BN9ABdfSl4h3AaUwGYbBVLMY8aT5JpTiE3I UZg/5iPXVGFPcfdFhzaPgCpZxQtGI3QV7m5jx+Pf8r0ifuTNi8bAbwHCRzmOV8rA 1LM4fvlCPd6TiP3UANWM7PFGbX8UArgzXlb8jSwkxEVC02oZitol4UhcLgacwVrO 0/0q71pyn8W3NBQ1QPUaUg1M81sE501NCTCP3rEg+o6g7oxiq+GpgB0FKwCJxrTk n3EL7tyhbvVcsglPLRkIXkGz3o5XdelFJ66+qS+mZAiPozkzEFUIdxd8rHKsA1e4 ZIFARDvDgi8iTArbJnPsQH0CgK8+/2RV2ILFW00Zcu7batvSWJtAUNNFqTSN34tk JJzHWYwKfGwRIMyEABsy9wLez9K2tRIG0fX75p82dVbRcRZwwSfPmFdfDPuMRRmc dsNF3133TA92uxwZ177cZk537g+Q0/0I6bts8us3GlCdY2HBuIc+HvRJQyEEqGEv v1GfEdnwGLp4rmPI8uY+JQ87now7KYhAK1SVil9AXm3tLrIqJsHYayA9nI8mjxfY Mh1utEeP+TMuievDMQNo =il8c -----END PGP SIGNATURE-----