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FreeBSD-EN-16:03.ypclnt                                         Errata Notice
                                                          The FreeBSD Project

Topic:          YP/NIS client library critical bug

Category:       core
Module:         ypclnt
Announced:      2016-01-14
Credits:        Ravi Pokala,
                Lakshmi Narasimhan Sundararajan,
                Fred Lewis,
                Pushkar Kothavade
Affects:        All supported versions of FreeBSD.
Corrected:      2015-12-21 14:32:29 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)
                2016-01-13 05:32:24 UTC (stable/9, 9.3-STABLE)
                2016-01-14 09:11:26 UTC (releng/9.3, 9.3-RELEASE-p33)

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

I.   Background

The YP/NIS subsystem allows network management of passwd, group, netgroup,
hosts, services, rpc, bootparams and ethers file entries.  The ypclnt suite
provides an interface to the YP subsystem.

The standard NIS protocol limits its database entries to YPMAXRECORD (1024
characters).

II.  Problem Description

There is a bug with the NIS client library, which can lead to an infinite
loop.

III. Impact

A server that is deliberately configured to violate the NIS/YP protocol can
cause a FreeBSD NIS client to be stuck forever.

IV.  Workaround

No workaround is available, but systems that are not configured to use
NIS/YP are not affected.

V.   Solution

Perform one of the following:

1) Upgrade your system to a supported FreeBSD stable or release / security
branch (releng) dated after the correction date.

A reboot is recommended.

2) To update your 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

A reboot is recommended.

3) To update your 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.

# fetch https://security.FreeBSD.org/patches/EN-16:03/yplib.patch
# fetch https://security.FreeBSD.org/patches/EN-16:03/yplib.patch.asc
# gpg --verify yplib.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 <URL:https://www.FreeBSD.org/handbook/makeworld.html>.

A reboot is recommended.

VI.  Correction details

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

Branch/path                                                      Revision
- -------------------------------------------------------------------------
stable/9/                                                         r293804
releng/9.3/                                                       r293896
stable/10/                                                        r292547
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:

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

VII. References

<URL:https://reviews.freebsd.org/D4095>

The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-EN-16:03.ypclnt.asc>
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